Publications

Colour bio-factories: anthocyanin production in plant cell cultures

 Bioreactors with engineered tobacco (left) and wild-type grape (right) cell cultures.

Bioreactors with engineered tobacco (left) and wild-type grape (right) cell cultures.

OpenPlant Postdoc, Ingo Appelhagen, in Prof Cathie Martin's lab in the John Innes Centre has recently published an article in the journal Metabolic Engineering about his research to develop a system for production of high-levels of anthocyanins in plant cell cultures.

Anthocyanins give many fruits and flowers their red, purple or blue colouration. The martin lab are interested in the beneficial effects of anthocyanins in our diets and their use as natural colourants in the food and cosmetic industries.

 

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Appelhagen I, Wulff-Vester AK, Wendell M, Hvoslef-Eide AK, Russell J, Oertel A, Martens S, Mock HP, Martin C, Matros A (2018). Colour bio-factories: Towards scale-up production of anthocyanins in plant cell cultures. Metabolic Engineering. Doi: https://doi.org/10.1016/j.ymben.2018.06.004

Abstract

Anthocyanins are widely distributed, glycosylated, water-soluble plant pigments, which give many fruits and flowers their red, purple or blue colouration. Their beneficial effects in a dietary context have encouraged increasing use of anthocyanins as natural colourants in the food and cosmetic industries. However, the limited availability and diversity of anthocyanins commercially have initiated searches for alternative sources of these natural colourants. In plants, high-level production of secondary metabolites, such as anthocyanins, can be achieved by engineering of regulatory genes as well as genes encoding biosynthetic enzymes. We have used tobacco lines which constitutively produce high levels of cyanidin 3-O-rutinoside, delphinidin 3-O-rutinoside or a novel anthocyanin, acylated cyanidin 3-O-(coumaroyl) rutinoside to generate cell suspension cultures. The cell lines are stable in their production rates and superior to conventional plant cell cultures. Scale-up of anthocyanin production in small scale fermenters has been demonstrated. The cell cultures have also proven to be a suitable system for production of 13C-labelled anthocyanins. Our method for anthocyanin production is transferable to other plant species, such as Arabidopsis thaliana, demonstrating the potential of this approach for making a wide range of highly-decorated anthocyanins. The tobacco cell cultures represent a customisable and sustainable alternative to conventional anthocyanin production platforms and have considerable potential for use in industrial and medical applications of anthocyanins.

Engineering plant production systems to synthesise terpenoids

  Nicotiana benthamiana by Aymeric Leveau (John Innes Centre);  NRP-103

Nicotiana benthamiana by Aymeric Leveau (John Innes Centre); NRP-103

Researchers at the John Innes Centre, including OpenPlant PI Prof Anne Osbourn have recently published a review describing strategies developed in the lab to engineer terpenoid biosynthesis in plant-based production systems.

Terpenoids are the most structurally diverse class of plant natural products with a huge range of commercial and medical applications. Exploiting this enormous potential has historically been hindered due to low levels of these compounds in their natural sources, making isolation difficult, while their structural complexity frequently makes synthetic chemistry approaches uneconomical.

Reed, J. & Osbourn A. (2018), Engineering terpenoid production through transient expression in Nicotiana benthamiana. Plant Cell Rep. https://doi.org/10.1007/s00299-018-2296-3

Abstract

Terpenoids are the most structurally diverse class of plant natural products with a huge range of commercial and medical applications. Exploiting this enormous potential has historically been hindered due to low levels of these compounds in their natural sources, making isolation difficult, while their structural complexity frequently makes synthetic chemistry approaches uneconomical. Engineering terpenoid biosynthesis in heterologous host production platforms provides a means to overcome these obstacles. In particular, plant-based production systems are attractive as they provide the compartmentalisation and cofactors necessary for the transfer of functional pathways from other plants. Nicotiana benthamiana, a wild relative of tobacco, has become increasingly popular as a heterologous expression platform for reconstituting plant natural product pathways, because it is amenable to Agrobacterium-mediated transient expression, a scalable and highly flexible process that enables rapid expression of genes and enzymes from other plant species. Here, we review recent work describing terpene production in N. benthamiana. We examine various strategies taken to engineer this host for increased production of the target metabolite. We also look at how transient expression can be utilised for rapid generation of molecular diversity, including new-to-nature products. Finally, we highlight current issues surrounding this expression platform and discuss the future directions and developments which will be needed to fully realise the potential of this system.

OpenPlant Fund project publishes on droplet-based microfluidics for rapid phenotyping of plant systems

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Researchers from the University of Cambridge have this month published the results of a collaborative project, supported by the OpenPlant Fund, to develop droplet-based microfluidics systems for rapid prototyping in plant systems. The paper describes how they have achieved on-chip encapsulation and analysis of protoplasts isolated from the emergent plant model Marchantia polymorpha. We caught up with the team to find out more about their OpenPlant Fund project. Read on to find out more...

 

Yu Z, Boehm CR, Hibberd JM, Abell C, Haseloff J, Burgess SJ, et al. (2018) Droplet-based microfluidic analysis and screening of single plant cells. PLoS ONE 13(5): e0196810.

 

Publication abstract

Droplet-based microfluidics has been used to facilitate high-throughput analysis of individual prokaryote and mammalian cells. However, there is a scarcity of similar workflows applicable to rapid phenotyping of plant systems where phenotyping analyses typically are time-consuming and low-throughput. We report on-chip encapsulation and analysis of protoplasts isolated from the emergent plant model Marchantia polymorpha at processing rates of >100,000 cells per hour. We use our microfluidic system to quantify the stochastic properties of a heat-inducible promoter across a population of transgenic protoplasts to demonstrate its potential for assessing gene expression activity in response to environmental conditions. We further demonstrate on-chip sorting of droplets containing YFP-expressing protoplasts from wild type cells using dielectrophoresis force. This work opens the door to droplet-based microfluidic analysis of plant cells for applications ranging from high-throughput characterisation of DNA parts to single-cell genomics to selection of rare plant phenotypes.

 

Interview with the OpenPlant Fund team

A brief overview of the project

A current limitation for plant synthetic biology involves high-throughput screening of genetic parts in plants. Current approaches require testing circuits in individual plants, through transient or stable transgenics. Applying these techniques to hundreds of different circuits is not feasible at a laboratory scale. In this project, we use droplet based microfluidics to isolate and characterise both gene expression activity and chlorophyll content on single plant protoplasts at a high throughput scale. Our device can potentially analyse protoplasts at a processing rate of > 100,000 cells per hour.  We use this system to quantify the stochastic properties of a heat-inducible promoter across a population of transgenic Marchantia polymorpha protoplasts to demonstrate its potential for assessing gene expression activity in response to environmental conditions. In addition, we managed to sort droplets containing YFP-expressing protoplasts from wild type cells using dielectrophoresis force.  This work opens the door to droplet-based microfluidic analysis of plant cells for applications ranging from high-throughput characterisation of DNA parts to single-cell genomics to selection of rare plant phenotypes.

 

 A schematic of the droplet based microfluidics setup

A schematic of the droplet based microfluidics setup

 

What inspired the project?

Part of our research is focused on identifying DNA regulatory elements that could be used for designing synthetic promoters in plants. To achieve this, we would normally create a reporter construct containing the element of interest and then test its activity on individual plants through transient or stable genetic transformation. This approach can be very time consuming and impedes the researcher to test more than a handful of constructs at the time. Based on this we consider there was a need to develop methods that could accelerate the process. We knew Droplet-based microfluidics has been used to facilitate high throughput analysis of individual prokaryote and mammalian cells so we thought implementing this method in plants will be very useful.  

How did this project develop links between Cambridge and Norwich?

During the early stages of the project we teamed up with Oleg Raitskin from the Patron lab at the Earlham Institute. Oleg was very kind to share his experiences with protoplast isolation and also he showed us his method for protoplast transformation in tobacco leaves.

 

 Microscopy images of protoplasts captured in droplets and sorted by fluorescence

Microscopy images of protoplasts captured in droplets and sorted by fluorescence

 

What was your favourite aspect of the project?

We really enjoyed learning more about each other’s area of expertise. This project spans the disciplines of physical chemistry optomechatronics and biology so it gave us an opportunity to approach disciplines in which we were not very familiar.

 Sorting of M. polymorpha protoplasts: Microscopy images of microdroplets sorted into positive and negative channels based on their fluorescence intensity.

Sorting of M. polymorpha protoplasts: Microscopy images of microdroplets sorted into positive and negative channels based on their fluorescence intensity.

What is the biggest challenge the team faced?

Preparing high quality protoplast preparations from Marchantia was one of the greater challenges we encountered.

Is there something that came out of the project that you never expected at the beginning?

Being able to perform the sorting was unexpected at the beginning. Protoplasts are very sensitive cells that can burst spontaneously. The fact that we manage not just to isolate and measure but also sort opens a lot of possibilities for further applications.

How did the OpenPlant Fund enable the development of the project?

We could have never done this kind of project without the OpenPlant Fund. Apart of the funding which played a primal role in the development of the project, the OpenPlant fund offered great support across the whole process. For instance, our collaboration was established during a fund mixer organized by the synbio fund. Thanks to the Open Plant initiative we showed our project in various Open Plant meetings which resulted in very useful comments from various colleagues. Finally the costs derived from publishing the paper and making it open access were also covered by the grant.

What are the future opportunities to take this project forward?

Now that the system is set up, the next step could be to expand it to on-chip protoplast transformation (as has been done for other cell types). Protoplast transformation currently requires large amounts of materials (cells and DNA) and is low throughput, so this would be a big plus.

Researchers find first land plants were parasitised by microbes

The following blog was first published on the website of The Sainsbury Laboratory, Cambridge, and has been reproduced with the permission. The original can be found here.

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Sainsbury Laboratory researchers have found that the relationship between plants and filamentous microbes not only dates back millions of years, but that modern plants have maintained this ancient mechanism to accommodate and respond to microbial invaders.

Why do some plants welcome some microbes with open arms while giving others the cold-shoulder? Like most relationships, it’s complicated, and it all goes back a long way.

By studying liverworts – which diverged from other land plants early in the history of plant evolution – researchers from the Sainsbury Laboratory at the University of Cambridge have found that the relationship between plants and filamentous microbes not only dates back millions of years, but that modern plants have maintained this ancient mechanism to accommodate and respond to microbial invaders.

Liverworts

 Close up of a liverwort.

Close up of a liverwort.

Liverworts are small green plants that don’t have roots, stems, leaves or flowers. They belong to a group of plants called Bryophytes, which also includes mosses and hornworts. Bryophytes diverged from other plant lineages early in the evolution of plants and are thought to be similar to some of the earliest diverging land plant lineages. Liverworts are found all over the world and are often seen growing as a weed in the cracks of paving or on the soil of potted plants. Marchantia polymorpha, which is also known as the common liverwort or umbrella liverwort, was used in this research.

Published today in the journal Proceedings of the National Academy of Sciences, a new study shows that aggressive filamentous microbial (fungi-like) pathogens can invade liverworts and that some elements of the liverwort’s response are shared with distantly related plants. The first author of the paper, Dr Philip Carella, said the research showed that liverworts could be infected by the common and devastating microorganism Phytophthora: “We know a great deal about microbial infections of modern flowering plants, but until now we haven’t known how distantly related plant lineages dealt with an invasion by an aggressive microbe. To test this, we first wanted to see if Phytophthora could infect and complete its life cycle in a liverwort."

 

   A healthy Marchantia polymorpha liverwort (left) and one that has been infected by Phytophthora palmivora (right).

A healthy Marchantia polymorpha liverwort (left) and one that has been infected by Phytophthora palmivora (right).

We found that Phytophthora palmivora can colonise the photosynthetic tissues of the liverwort Marchantia polymorpha by invading living cells. Marchantia responds to this by deploying proteins around the invading Phytophthora hyphal structures. These proteins are similar to those that are produced in flowering plants such as tobacco, legumes or Arabidopsis in response to infections by both symbiont and pathogenic microbes.”

 

   Microscopy image of a cross-section of a Marchantia polymorpha thallus showing the Phytophthora infection (red) in the upper photosynthetic layer of the liverwort plant.

Microscopy image of a cross-section of a Marchantia polymorpha thallus showing the Phytophthora infection (red) in the upper photosynthetic layer of the liverwort plant.

These lineages share a common ancestor that lived over 400 million years ago, and fossils from this time period show evidence that plants were already forming beneficial relationships with filamentous microbes. Dr Carella added: “These findings raise interesting questions about how plants and microbes have interacted and evolved pathogenic and symbiotic relationships. Which mechanisms evolved early in a common ancestor before the plant groups diverged and which evolved independently?”

Phytophthora

  Phytophthora  growing on  Marchantia thallus

Phytophthora growing on Marchantia thallus

Phytophthora is a water mould. Although it looks like it, it is not a fungus at all. Instead it belongs to the oomycetes and is a type of filamentous microbe. Phytophthora pathogens are best known for devastating crops, such as causing the Irish potato famine through potato late blight disease as well as many tropical diseases. This research used the tropical species, Phytophthora palmivora, which causes diseases in cocoa, oil palms, coconut palms and rubber trees.

Dr Sebastian Schornack, who led the research team, says the study indicates that early land plants were already genetically equipped to respond to microbial infections: “This discovery reveals that certain response mechanisms were already in place very early on in plant evolution.”

“Finding that pathogenic filamentous microbes can invade living liverwort cells and that liverworts respond using similar proteins as in flowering plants suggests that the relationship between filamentous pathogens and plants can be considered ancient. We will continue to study whether pathogens are exploiting mechanisms evolved to support symbionts and, hopefully, this will allow us to establish future crop plants that both benefit from symbionts whilst remaining more resistant to pathogens.

“Liverworts are showing great promise as a model plant system and this discovery that they can be colonised by pathogens of flowering plants makes them a valuable model plant to continue research into plant-microbe interactions.”

Read the full paper online.

This research was funded by the Gatsby Charitable Foundation, the Royal Society, the BBSRC OpenPlant initiative and the Natural Environment Research Council.

 

Photo Credits: Images by Philip Carella.

Collaboration including OpenPlant researchers discovers that C4 photosynthesis has co-opted an ancient C3 regulatory code

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A new publication in Molecular Biology and Evolution has resulted from a collaboration of OpenPlant PI Prof. Julian Hibberd and researcher Dr Ivan Reyna-Llorens with colleagues in Portugal at the Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, and the Instituto de Biologia Experimental e Tecnológica in Portugal. The paper shows that C4 photosynthesis has co-opted an ancient C3 regulatory code:

Borba AR, Serra TS, Górska A, Gouveia P, Cordeiro AM, Reyna-Llorens I, Kneřová J, Barros PM, Abreu IA, Oliveira MM, Hibberd JM, Saibo NJM (2018). Synergistic binding of bHLH transcription factors to the promoter of the maize NADP-ME gene used in C4 photosynthesis is based on an ancient code found in the ancestral C3 state. Molecular Biology and Evolution, msy060, https://doi.org/10.1093/molbev/msy060

Abstract

C4 photosynthesis has evolved repeatedly from the ancestral C3 state to generate a carbon concentrating mechanism that increases photosynthetic efficiency. This specialised form of photosynthesis is particularly common in the PACMAD clade of grasses, and is used by many of the world’s most productive crops. The C4 cycle is accomplished through cell-type specific accumulation of enzymes but cis-elements and transcription factors controlling C4 photosynthesis remain largely unknown. Using the NADP-Malic Enzyme (NADP-ME) gene as a model we tested whether mechanisms impacting on transcription in C4 plants evolved from ancestral components found in C3 species. Two basic Helix-Loop-Helix (bHLH) transcription factors, ZmbHLH128 and ZmbHLH129, were shown to bind the C4NADP-ME promoter from maize. These proteins form heterodimers and ZmbHLH129 impairs trans-activation by ZmbHLH128. Electrophoretic mobility shift assays indicate that a pair of cis-elements separated by a seven base pair spacer synergistically bind either ZmbHLH128 or ZmbHLH129. This pair of cis-elements is found in both C3 and C4 Panicoid grass species of the PACMAD clade. Our analysis is consistent with this cis-element pair originating from a single motif present in the ancestral C3 state. We conclude that C4 photosynthesis has co-opted an ancient C3 regulatory code built on G-box recognition by bHLH to regulate the NADP-ME gene. More broadly, our findings also contribute to the understanding of gene regulatory networks controlling C4 photosynthesis.


Image by Ninghui Shi: Cross section of a C4 plant. Specifically of a maize leaf. Vascular bundles shown. Drawing based on microscopic images courtesy of Cambridge University Plant Sciences Department. Image is shared under licence CC BY-SA 3.0

Bio-solar panel developed by researchers at University of Cambridge and Imperial College London

A two-in-one solar bio-battery and solar panel has been created by researchers who printed living cyanobacteria and circuitry onto paper.

Cyanobacteria are photosynthetic micro-organisms that have been on Earth for billions of years. They are thought to be the primary reason why the Earth’s atmosphere is oxygen rich. Several synthetic biology groups in Cambridge are working on these useful organisams, including OpenPlant PI Prof Chris Howe and OpenPlant Fund grantee Dr Paolo Bombelli (both Department of Biochemistry).

Together with researchers from Imperial College London and Central Saint Martins, they demonstrated that cyanobacteria could be used as an ink and printed from an inkjet printer in precise patterns onto electrically conductive carbon nanotubes, which were also inkjet-printed onto the piece of paper. The team showed that the cyanobacteria survived the printing process and were able to perform photosynthesis so that small amounts of electrical energy could be harvested over a period of 100 hours.

A bio-solar panel made in this way, the approximate size of an iPad, could power a simple digital clock, and in separate experiments, a small LED light bulb.

The team suggest their breakthrough could lead to new types of electrical devices that are made from paper and printed photosynthetic bacteria. These could include disposable power supplies integrated into paper-based sensors for monitoring patients with diabetes or devices that resemble wallpaper but are in fact environmental sensors for monitoring air quality in the home.

Dr Marin Sawa, a co-author from the Department of Chemical Engineering at Imperial College London, said: “We think our technology could have a range of applications such as acting as a sensor in the environment. Imagine a paper-based, disposable environmental sensor disguised as wallpaper, which could monitor air quality in the home. When it has done its job it could be removed and left to biodegrade in the garden without any impact on the environment.” 

New type of renewable energy

The solar bio-battery pushes forward research into a new type of renewable energy technology currently being developed by scientists globally called microbial biophotoltaics (BPV). It exploits the ability of cyanobacteria and other algae that use photosynthesis to convert light energy into an electrical current using water as the source of electrons.

One of the advantages of using BPVs to harvest energy from cells like cyanobacteria is that they can produce small amounts electricity in daylight and carry on producing it even in the dark from molecules produced in the light.

Some of the current limitations that scientists have previously faced when developing BPVs are that they are expensive to make, have low power output, and a short lifespan. All these drawbacks have prevented scientists from being able to scale up the technology to an industrial level.

The team says their approach of using an off-the-shelf inkjet printer to construct BPVs demonstrates a potential method for easily scaling up the technology, which may pave the way for its wider use.

Dr Andrea Fantuzzi, a co-author of the study from Department of Life Sciences at Imperial College London, said: “Paper-based BPVs are not meant to replace conventional solar cell technology for large-scale power production, but instead, could be used to construct power supplies that are both disposable and biodegradable. Their low power output means they are more suited to devices and applications that require a small and finite amount of energy, such as environmental sensing and biosensors.”

New types of paper-based sensors

The researchers suggest BPVs could be used in new forms of sensors built entirely from paper, which would mean that they are cheaper and more cost effective to make with less impact on resources and the environment.

Another example for BPVs, suggest the team, is in the healthcare industry.

Dr Andrea Fantuzzi said: “Paper-based BPVs integrated with printed electronics and biosensor technology could usher in an age of disposable paper-based sensors that monitor health indicators such as blood glucose levels in patients with diabetes. Once a measurement is taken, the device could be easily disposed of with low environmental impact and its ease of use could facilitate its direct employment by the patients. Furthermore, this approach has the potential to be very cost-effective, which could also pave the way for its use in developing countries with limited healthcare budgets and strains on resources.”

Next steps

The current paper-based BPV unit is a palm size. The next step will see the team scale up their proof-of-concept to A4 size to determine the electrical output on a larger scale.

Professor Christopher Howe, a co-author from the Department of Biochemistry at the University of Cambridge, added: “This is an exciting proof-of-concept. The challenge now is to make panels that are more powerful, long-lasting and robust.”

Publication

Sawa, Marin, Andrea Fantuzzi, Paolo Bombelli, Christopher J. Howe, Klaus Hellgardt, and Peter J. Nixon. "Electricity generation from digitally printed cyanobacteria." Nature Communications 8, no. 1 (2017): 1327.

Press release text is from Imperial College London and is available under an Attribution-NonCommercial-ShareAlike Creative Commons license.

Image credit: From publication, licensed under CC-BY 4.0

Marchantia polymorpha genome published with OpenPlant co-authors

 Marchantia polymorpha. Credit: Jim Haseloff

Marchantia polymorpha. Credit: Jim Haseloff

OpenPlant Director Dr Jim Haseloff and past and present Cambridge-based plant synthetic biology researchers including Mihails Delman, Bernardo Pollak and Christian Boehm are all co-authors of a major Cell publication on the Marchantia polymorpha genome. The paper involved contributions from researchers across the world who work on this interesting liverwort.

OpenPlant is establishing Marchantia as a test bed for plant synthetic biology, exploiting its extraordinary experimental properties in order to provide a prototype for other OpenPlant initiatives in higher plants. We will produce systematic collections of experimental protocols, shared DNA parts and Marchantia lines to be distributed via the OpenMTA.

Abstract

The evolution of land flora transformed the terrestrial environment. Land plants evolved from an ancestral charophycean alga from which they inherited developmental, biochemical, and cell biological attributes. Additional biochemical and physiological adaptations to land, and a life cycle with an alternation between multicellular haploid and diploid generations that facilitated efficient dispersal of desiccation tolerant spores, evolved in the ancestral land plant. We analyzed the genome of the liverwort Marchantia polymorpha, a member of a basal land plant lineage. Relative to charophycean algae, land plant genomes are characterized by genes encoding novel biochemical pathways, new phytohormone signaling pathways (notably auxin), expanded repertoires of signaling pathways, and increased diversity in some transcription factor families. Compared with other sequenced land plants, M. polymorpha exhibits low genetic redundancy in most regulatory pathways, with this portion of its genome resembling that predicted for the ancestral land plant.

Reference

Bowman, John L., et al. "Insights into Land Plant Evolution Garnered from the Marchantia polymorpha Genome.Cell 171.2 (2017): 287-304.

 Fig 1 from Bowman et al., 2017

Fig 1 from Bowman et al., 2017

Report highlights opportunities and risks associated with synthetic biology and bioengineering

Human genome editing, 3D-printed replacement organs and artificial photosynthesis – the field of bioengineering offers great promise for tackling the major challenges that face our society. But as a new article out today highlights, these developments provide both opportunities and risks in the short and long term.

Rapid developments in the field of synthetic biology and its associated tools and methods, including more widely available gene editing techniques, have substantially increased our capabilities for bioengineering – the application of principles and techniques from engineering to biological systems, often with the goal of addressing 'real-world' problems.

In a feature article published in the open access journal eLife, an international team of experts led by Dr Bonnie Wintle and Dr Christian R. Boehm from the Centre for the Study of Existential Risk at the University of Cambridge, capture perspectives of industry, innovators, scholars, and the security community in the UK and US on what they view as the major emerging issues in the field. The participants included several OpenPlant researchers and members of the management team.

Dr Wintle says: “The growth of the bio-based economy offers the promise of addressing global environmental and societal challenges, but as our paper shows, it can also present new kinds of challenges and risks. The sector needs to proceed with caution to ensure we can reap the benefits safely and securely.”

The report is intended as a summary and launching point for policy makers across a range of sectors to further explore those issues that may be relevant to them.

Among the issues highlighted by the report as being most relevant over the next five years are:

Artificial photosynthesis and carbon capture for producing biofuels

If technical hurdles can be overcome, such developments might contribute to the future adoption of carbon capture systems, and provide sustainable sources of commodity chemicals and fuel.  

Enhanced photosynthesis for agricultural productivity

Synthetic biology may hold the key to increasing yields on currently farmed land – and hence helping address food security – by enhancing photosynthesis and reducing pre-harvest losses, as well as reducing post-harvest and post-consumer waste.

Synthetic gene drives

Gene drives promote the inheritance of preferred genetic traits throughout a species, for example to prevent malaria-transmitting mosquitoes from breeding. However, this technology raises questions about whether it may alter ecosystems, potentially even creating niches where a new disease-carrying species or new disease organism may take hold.

Human genome editing

Genome engineering technologies such as CRISPR/Cas9 offer the possibility to improve human lifespans and health. However, their implementation poses major ethical dilemmas. It is feasible that individuals or states with the financial and technological means may elect to provide strategic advantages to future generations.

Defence agency research in biological engineering

The areas of synthetic biology in which some defence agencies invest raise the risk of ‘dual-use’. For example, one programme intends to use insects to disseminate engineered plant viruses that confer traits to the target plants they feed on, with the aim of protecting crops from potential plant pathogens – but such technologies could plausibly also be used by others to harm targets.

In the next five to ten years, the authors identified areas of interest including:

Regenerative medicine: 3D printing body parts and tissue engineering

While this technology will undoubtedly ease suffering caused by traumatic injuries and a myriad of illnesses, reversing the decay associated with age is still fraught with ethical, social and economic concerns. Healthcare systems would rapidly become overburdened by the cost of replenishing body parts of citizens as they age and could lead new socioeconomic classes, as only those who can pay for such care themselves can extend their healthy years.

Microbiome-based therapies

The human microbiome is implicated in a large number of human disorders, from Parkinson’s to colon cancer, as well as metabolic conditions such as obesity and type 2 diabetes. Synthetic biology approaches could greatly accelerate the development of more effective microbiota-based therapeutics. However, there is a risk that DNA from genetically engineered microbes may spread to other microbiota in the human microbiome or into the wider environment.

Intersection of information security and bio-automation

Advancements in automation technology combined with faster and more reliable engineering techniques have resulted in the emergence of robotic 'cloud labs' where digital information is transformed into DNA then expressed in some target organisms. This opens the possibility of new kinds of information security threats, which could include tampering with digital DNA sequences leading to the production of harmful organisms, and sabotaging vaccine and drug production through attacks on critical DNA sequence databases or equipment.

Over the longer term, issues identified include:

New makers disrupt pharmaceutical markets

Community bio-labs and entrepreneurial startups are customizing and sharing methods and tools for biological experiments and engineering. Combined with open business models and open source technologies, this could herald opportunities for manufacturing therapies tailored to regional diseases that multinational pharmaceutical companies might not find profitable. But this raises concerns around the potential disruption of existing manufacturing markets and raw material supply chains as well as fears about inadequate regulation, less rigorous product quality control and misuse.

Platform technologies to address emerging disease pandemics

Emerging infectious diseases—such as recent Ebola and Zika virus disease outbreaks—and potential biological weapons attacks require scalable, flexible diagnosis and treatment. New technologies could enable the rapid identification and development of vaccine candidates, and plant-based antibody production systems.

Shifting ownership models in biotechnology

The rise of off-patent, generic tools and the lowering of technical barriers for engineering biology has the potential to help those in low-resource settings, benefit from developing a sustainable bioeconomy based on local needs and priorities, particularly where new advances are made open for others to build on.

Dr Jenny Molloy comments: “One theme that emerged repeatedly was that of inequality of access to the technology and its benefits. The rise of open source, off-patent tools could enable widespread sharing of knowledge within the biological engineering field and increase access to benefits for those in developing countries.”

Professor Johnathan Napier from Rothamsted Research adds: “The challenges embodied in the Sustainable Development Goals will require all manner of ideas and innovations to deliver significant outcomes. In agriculture, we are on the cusp of new paradigms for how and what we grow, and where. Demonstrating the fairness and usefulness of such approaches is crucial to ensure public acceptance and also to delivering impact in a meaningful way.”

Dr Christian R. Boehm concludes: “As these technologies emerge and develop, we must ensure public trust and acceptance. People may be willing to accept some of the benefits, such as the shift in ownership away from big business and towards more open science, and the ability to address problems that disproportionately affect the developing world, such as food security and disease. But proceeding without the appropriate safety precautions and societal consensus—whatever the public health benefits—could damage the field for many years to come.”

The research was made possible by the Centre for the Study of Existential Risk, the Synthetic Biology Strategic Research Initiative (both at the University of Cambridge), and the Future of Humanity Institute (University of Oxford). It was based on a workshop co-funded by the Templeton World Charity Foundation and the European Research Council under the European Union’s Horizon 2020 research and innovation programme. 

Reference
Wintle, BC, Boehm, CR et al. A transatlantic perspective on 20 emerging issues in biological engineering. eLife; 14 Nov 2017; DOI: 10.7554/eLife.30247

Link to original piece on University News

Hear OpenPlant Coordinator Dr Jenny Molloy discuss the work on BBC Radio 4 'Inside Science' 


The text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Image Credit: Reaching for the Sky
Susanne Nilsson

 

Low cost and open source multi-fluorescence imaging system for teaching and research in biology and bioengineering

Former OpenPlant Fellow Dr Fernan Federici, former OpenPlant PDRA Dr Tim Rudge and colleagues have recently published a pre-print for their low cost and open source multi-fluorescence imaging system for teaching and research in biology and bioengineering, supported by the OpenPlant Fund.

Nuñez, Isaac, Tamara Matute, Roberto Herrera, Juan Keymer, Tim Marzullo, Tim Rudge, and Fernan Federici. "Low cost and open source multi-fluorescence imaging system for teaching and research in biology and bioengineering." bioRxiv (2017): 194324

 Examples of images of bacterial colonies and cell-free systems using the microscope. Credit: Federici Lab

Examples of images of bacterial colonies and cell-free systems using the microscope. Credit: Federici Lab

Abstract

The advent of easy-to-use open source microcontrollers, off-the-shelf electronics and customizable manufacturing technologies has facilitated the development of inexpensive scientific devices and laboratory equipment. In this study, we describe an imaging system that integrates low-cost and open-source hardware, software and genetic resources. The multi-fluorescence imaging system consists of readily available 470 nm LEDs, a Raspberry Pi camera and a set of filters made with low cost acrylics. This device allows imaging in scales ranging from single colonies to entire plates.

We developed a set of genetic components (e.g. promoters, coding sequences, terminators) and vectors following the standard framework of Golden Gate, which allowed the fabrication of genetic constructs in a combinatorial, low cost and robust manner. In order to provide simultaneous imaging of multiple wavelength signals, we screened a series of long stokes shift fluorescent proteins that could be combined with cyan/green fluorescent proteins. We found CyOFP1, mBeRFP and sfGFP to be the most compatible set for 3-channel fluorescent imaging. We developed open source Python code to operate the hardware to run time-lapse experiments with automated control of illumination and camera and a Python module to analyze data and extract meaningful biological information.

To demonstrate the potential application of this integral system, we tested its performance on a diverse range of imaging assays often used in disciplines such as microbial ecology, microbiology and synthetic biology. We also assessed its potential for STEM teaching in a high school environment, using it to teach biology, hardware design, optics, and programming. Together, these results demonstrate the successful integration of open source hardware, software, genetic resources and customizable manufacturing to obtain a powerful, low cost and robust system for STEM education, scientific research and bioengineering. All the resources developed here are available under open source license

OpenPlant Fund supported project publishes on better DNA transfer from Escherichia coli to Bacillus subtilis

Dr Mario Juhas and OpenPlant PI  Dr Jim Ajioka from the Department of Pathology at the University of Cambridge have contributed to creating reliable and efficient systems for the transfer of synthetic DNA between E. coli and B. subtilis, supported by the OpenPlant Fund.

The majority of the good DNA editing techniques have been developed in Escherichia coli; however, Bacillus subtilis is better host for a plethora of synthetic biology and biotechnology applications. 

Using synthetic biology approaches, such as streamlined lambda Red recombineering and Gibson Isothermal Assembly, the team integrated genetic circuits  encoding the lysis genes of bacteriophages MS2, ΦX174 and lambda, the thermosensitive repressor and the T7 RNA polymerase into the E. coli chromosome.

In this system the T7 RNA polymerase regulated by the thermosensitive repressor drives the expression of the phage lysis genes. T7 RNA polymerase significantly increases efficiency of cell lysis and transfer of the plasmid and bacterial artificial chromosome-encoded DNA from the lysed E. coli into B. subtilis. The T7 RNA polymerase-driven inducible cell lysis system is therefore suitable for the efficient cell lysis and transfer of the DNA engineered in E. coli to other naturally competent hosts, such as B. subtilis.

The research obtained support from the SynBio Fund and OpenPlant Fund

The full article can be read here.

Image attribution: Debivort at the English language Wikipedia
This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

 

Commentary on a Major Advance in Plastid Transformation

OpenPlant PI Professor Julian Hibberd (Department of Plant Sciences, University of Cambridge) has summarised advances towards efficient plastid transformation in Arabidopsis thaliana as part of a new paper in Plant Physiology

This commentary follows 'Efficient Plastid Transformation in Arabidopsis' reported by Pal Maliga's team in this month's Plant Physiology, which could be regarded as a major advance in plastid transformation. Stable manipulation of the plastid genome of flowering plants was first reported nearly 30 years agoby Svab et al. However, for key species including cereal crops including Arabidopsis (Arabidopsis thaliana), the spectinomycin-based approach using the addition of the aadA gene has proved ineffective.

Hibberd cites Parker et al who showed that ecotypes of Arabidopsis vary in their sensitivity to spectinomycin due to the mutant allele of the nuclear gene ACC2. Its product is targeted to plastids and so provides an alternate to the partially plastid-encoded acetyl-Coenzyme A carboxylase that is inactivated by spectinomycin. Parker et al. proposed that their findings may provide a route to increase efficiency of chloroplast transformation in the Brassicaceae.

Yu et al. (2017) now provide strong support for this conjecture showing that by removing redundancy afforded by ACC2, efficient selection for transplastomic events can be achieved in Arabidopsis.

The next challenge is therefore to identify procedures and ecotypes that facilitate this conversion of transplastomic callus of Arabidopsis into stable and heritable plant material.

Hibberd's full commentary can be read here.

OpenPlant researchers publish a strategy to improve conversion of plant biomass to sugars for bioenergy

A new publication from the lab of OpenPlant PI Prof. Paul Dupree, University of Cambridge in Biotechnology for Biofuels describes work to improve processing of softwood to biofuels using a synthetic biology strategy to express and assay conifer cell wall synthesis enzymes.

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Lyczakowski, J.J., Wicher, K.B., Terrett, O.M., Faria-Blanc, N., Yu, X., Brown, D., Krogh, K.B.R.M., Dupree, P., and Busse-Wicher, M. (2017). Removal of glucuronic acid from xylan is a strategy to improve the conversion of plant biomass to sugars for bioenergy. Biotechnology for Biofuels 10: 224

Abstract

Background: Plant lignocellulosic biomass can be a source of fermentable sugars for the production of second generation biofuels and biochemicals. The recalcitrance of this plant material is one of the major obstacles in its conversion into sugars. Biomass is primarily composed of secondary cell walls, which is made of cellulose, hemicelluloses and lignin. Xylan, a hemicellulose, binds to the cellulose microfibril and is hypothesised to form an interface between lignin and cellulose. Both softwood and hardwood xylan carry glucuronic acid side branches. As xylan branching may be important for biomass recalcitrance and softwood is an abundant, non-food competing, source of biomass it is important to investigate how conifer xylan is synthesised.

Results: Here, we show using Arabidopsis gux mutant biomass that removal of glucuronosyl substitutions of xylan can allow 30% more glucose and over 700% more xylose to be released during saccharification. Ethanol yields obtained through enzymatic saccharification and fermentation of gux biomass were double those obtained for non-mutant material. Our analysis of additional xylan branching mutants demonstrates that absence of GlcA is unique in conferring the reduced recalcitrance phenotype. As in hardwoods, conifer xylan is branched with GlcA. We use transcriptomic analysis to identify conifer enzymes that might be responsible for addition of GlcA branches onto xylan in industrially important softwood. Using a combination of in vitro and in vivo activity assays, we demonstrate that a white spruce (Picea glauca) gene, PgGUX, encodes an active glucuronosyl transferase. Glucuronic acid introduced by PgGUX reduces the sugar release of Arabidopsis gux mutant biomass to wild-type levels indicating that it can fulfil the same biological function as native glucuronosylation.

Conclusion: Removal of glucuronic acid from xylan results in the largest increase in release of fermentable sugars from Arabidopsis plants that grow to the wild-type size. Additionally, plant material used in this work did not undergo any chemical pretreatment, and thus increased monosaccharide release from gux biomass can be achieved without the use of environmentally hazardous chemical pretreatment procedures. Therefore, the identification of a gymnosperm enzyme, likely to be responsible for softwood xylan glucuronosylation, provides a mutagenesis target for genetically improved forestry trees.

Rapid transporter regulation prevents substrate flow traffic jams in boron transport

Researchers at the John Innes Centre collaborated with colleagues from the University of Tokyo to understand the regulation of boron transport in Arabidopsis. Nutrient uptake relies on both a regulatory circuit within cells, and a coordinated behaviour across tissues. This work used both computational and molecular biology tools to model the effects of slowing boron uptake, discovering that this peturbation of the system leads to traffic-jam like behaviour of nutrient flow. Read more about it in this JIC news article. Experiments were partly funded through the OpenPlant Fund.

Sotta, N., Duncan, S., Tanaka, M., Takafumi, S., Marée, A.F., Fujiwara, T., Grieneisen, V.A., 2017. Rapid transporter regulation prevents substrate flow traffic jams in boron transport. eLife 2017;6: e27038.

Abstract

Nutrient uptake by roots often involves substrate-dependent regulated nutrient transporters. For robust uptake, the system requires a regulatory circuit within cells and a collective, coordinated behaviour across the tissue. A paradigm for such systems is boron uptake, known for its directional transport and homeostasis, as boron is essential for plant growth but toxic at high concentrations. In Arabidopsis thaliana Boron up-take occurs via diffusion facilitators (NIPs) and exporters (BORs), each presenting distinct polarity. Intriguingly, although boron soil concentrations are homogenous and stable, both transporters manifest strikingly swift boron-dependent regulation. Through mathematical modelling, we demonstrate that slower regulation of these transporters leads to physiologically detrimental oscillatory behaviour. Cells become periodically exposed to potentially cytotoxic boron levels, and nutrient throughput to the xylem becomes hampered. We conclude that, while maintaining homeostasis, swift transporter regulation within a polarised tissue context is critical to prevent intrinsic traffic-jam like behaviour of nutrient flow.

 

John Innes Centre researchers develop plant-made synthetic polio vaccine

Researchers at the John Innes Centre, including OpenPlant PI Prof George Lomonossoff, and collaborators, have published research to produce a new polio vaccine in plants, using the HyperTrans transient expression system. The work, funded by the World Health Organisation, was published in Nature Communications. It is hoped that this new polio vaccine will be a move towards global eradication of the disease. The publication was covered by JIC News and the BBC.

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Marsian, J., Fox, H., Bahar, M.W., Kotecha, A., Fry, E.E., Stuart, D.I., Macadam, A.J., Rowlands, D.J., & Lomonossoff, G.P. (2017) Plant-made polio type 3 stabilized VLPs—a candidate synthetic polio vaccine. Nature Communications 8, Article number: 245.

Abstract

Poliovirus (PV) is the causative agent of poliomyelitis, a crippling human disease known since antiquity. PV occurs in two distinct antigenic forms, D and C, of which only the D form elicits a robust neutralizing response. Developing a synthetically produced stabilized virus-like particle (sVLP)-based vaccine with D antigenicity, without the drawbacks of current vaccines, will be a major step towards the final eradication of poliovirus. Such a sVLP would retain the native antigenic conformation and the repetitive structure of the original virus particle, but lack infectious genomic material. In this study, we report the production of synthetically stabilized PV VLPs in plants. Mice carrying the gene for the human PV receptor are protected from wild-type PV when immunized with the plant-made PV sVLPs. Structural analysis of the stabilized mutant at 3.6 Å resolution by cryo-electron microscopy and single-particle reconstruction reveals a structure almost indistinguishable from wild-type PV3.

OpenPlant researchers advance a translational synthetic biology platform for rapid access to new drug-like molecules

Researchers in Prof Anne Osbourn's lab at the John Innes Centre, including Prof Osbourn and OpenPlant PDRA Dr Michael Stephenson, have published a new paper detailing their advances in rapidly creating and purifying gram-scale quantities of natural products that were previously not possible to synthesise. This has the potential to reinvigorate drug discovery pipelines by opening up whole regions of chemical diversity for testing and production of potentially medicinally important molecules.

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Reed, J., Stephenson, M.J., Miettinen, K., Brouwer, B., Leveau, A., Brett, P., Goss, R.J., Goossens, A., O’Connell, M.A. and Osbourn, A., 2017. A translational synthetic biology platform for rapid access to gram-scale quantities of novel drug-like moleculesMetabolic Engineering. DOI: 10.1016/j.ymben.2017.06.012

 Fig 2 from paper: Generation of gram quantities of triterpene using vacuum infiltration  a , Vacuum infiltration of  N. benthamiana  plants. Plants are retained by a bespoke holder, inverted into a bath containing 10 L of  A. tumefaciens  suspension, and a vacuum applied. Upon release of the vacuum the infiltration process is complete.  b , GFP expression in leaves from a vacuum-infiltrated plant 5 days after infiltration (leaves arranged from top left to bottom right in descending order of their height on the plant). The youngest leaves (top left) were formed post-infiltration.  c , β-Amyrin purified from vacuum-infiltrated plants following transient expression.

Fig 2 from paper: Generation of gram quantities of triterpene using vacuum infiltration a, Vacuum infiltration of N. benthamiana plants. Plants are retained by a bespoke holder, inverted into a bath containing 10 L of A. tumefaciens suspension, and a vacuum applied. Upon release of the vacuum the infiltration process is complete. b, GFP expression in leaves from a vacuum-infiltrated plant 5 days after infiltration (leaves arranged from top left to bottom right in descending order of their height on the plant). The youngest leaves (top left) were formed post-infiltration. c, β-Amyrin purified from vacuum-infiltrated plants following transient expression.

Abstract

Plants are an excellent source of drug leads. However availability is limited by access to source species, low abundance and recalcitrance to chemical synthesis. Although plant genomics is yielding a wealth of genes for natural product biosynthesis, the translation of this genetic information into small molecules for evaluation as drug leads represents a major bottleneck. For example, the yeast platform for artemisinic acid production is estimated to have taken >150 person years to develop. Here we demonstrate the power of plant transient transfection technology for rapid, scalable biosynthesis and isolation of triterpenes, one of the largest and most structurally diverse families of plant natural products. Using pathway engineering and improved agro-infiltration methodology we are able to generate gram-scale quantities of purified triterpene in just a few weeks. In contrast to heterologous expression in microbes, this system does not depend on re-engineering of the host. We next exploit agro-infection for quick and easy combinatorial biosynthesis without the need for generation of multi-gene constructs, so affording an easy entrée to suites of molecules, some new-to-nature, that are recalcitrant to chemical synthesis. We use this platform to purify a suite of bespoke triterpene analogs and demonstrate differences in anti-proliferative and anti-inflammatory activity in bioassays, providing proof of concept of this system for accessing and evaluating medicinally important bioactives. Together with new genome mining algorithms for plant pathway discovery and advances in plant synthetic biology, this advance provides new routes to synthesize and access previously inaccessible natural products and analogs and has the potential to reinvigorate drug discovery pipelines.

 

 

OpenPlant Fund contributes to publication of methods for single molecule RNA FISH in Arabidopsis root cells

Researchers from the John Innes Centre have published a method for accurate quantification and localization of mRNA in fixed plant samples by detection of individual mRNA molecules. This work was in part supported through the OpenPlant Fund.

Duncan, S., Olsson, T.S.G., Hartley, M., Dean, C., Rosa S., 2017. Single Molecule RNA FISH in Arabidopsis Root Cells. Bio-protocol 7(8): e2240.

Abstract

Methods that allow the study of gene expression regulation are continually advancing. Here, we present an in situ hybridization protocol capable of detecting individual mRNA molecules in plant root cells, thus permitting the accurate quantification and localization of mRNA within fixed samples (Duncan et al., 2016; Rosa et al., 2016). This single molecule RNA fluorescence in situ hybridization (smFISH) uses multiple single-labelled oligonucleotide probes to bind target RNAs and generate diffraction-limited signals that can be detected using a wide-field fluorescence microscope. We adapted a recent version of this method that uses 48 fluorescently labeled DNA oligonucleotides (20 mers) to hybridize to different portions of each transcript (Raj et al., 2008). This approach is simple to implement and has the advantage that it can be readily applied to any genetic background.

The cutting edge of Synthetic Botany reviewed by OpenPlant researchers

Cambridge researchers including OpenPlant Director Prof Jim Haseloff  and OpenPlant PI Dr Nicola Patron (Earlham Institute) have reviewed the state of art and future prospects for Synthetic Botany - the application of synthetic biology to engineering nuclear and chloroplast genomes in plants.

Plants represent the only available platform allowing sustainable bioproduction at the gigatonne scale. Combining modular body plans and developmental plasticity with capacity for photosynthesis and extensive secondary metabolism, plants are highly attractive targets for genetic engineering. However, efforts in this area have been complicated by slow growth rates, physiological complexity, and technical challenges in the handling and manipulation of plants. Furthermore, better experimental and theoretical frameworks are needed to dissect and understand the hierarchies of genetic and physical interactions shaping their multicellular behavior.  

Joint first-authors Christian Boehm and Bernardo Pollak and colleagues reviewed the state of the art in genetic engineering of the nuclear and chloroplast genomes in plants, and highlight new approaches to harnessing their potential as custom agronomic systems for large-scale production. In particular, they show how simple plant models like the liverwort Marchantia polymorpha - combined with standard DNA parts and advanced quantitative imaging technqiues - can bridge the complexity gap between microbes and higher plants. Synthetic genetic circuits proven in Marchantia may serve as valuable tools for addressing some of the major challenges in plant metabolic engineering such as the introduction of C4 photosynthesis in C3 crops or the refactoring of nitrogen fixation pathways.

Boehm CR, Pollak B, Purswani N, Patron N & Haseloff J. (2017) Synthetic Biology. CSH Perspect Biol a023887o

Integrative bacterial artificial chromosomes for DNA integration into the Bacillus subtilis chromosome

The research presented in the following publication was funded in part through the OpenPlant Fund.

Juhas, Mario, and James W. Ajioka. “Integrative bacterial artificial chromosomes for DNA integration into the Bacillus subtilis chromosome.”Journal of microbiological methods 125 (2016): 1-7.

Cambridge Repository Full-Text | Publisher Full-Text

Open Access publication under CC-BY 4.0

Abstract

Bacillus subtilis is a well-characterized model bacterium frequently used for a number of biotechnology and synthetic biology applications. Novel strategies combining the advantages of B. subtilis with the DNA assembly and editing tools of Escherichia coli are crucial for B. subtilis engineering efforts. We combined Gibson Assembly and λ red recombineering in E. coli with RecA-mediated homologous recombination in B. subtilisfor bacterial artificial chromosome-mediated DNA integration into the well-characterized amyE target locus of the B. subtilis chromosome. The engineered integrative bacterial artificial chromosome iBAC(cav) can accept any DNA fragment for integration into B. subtilis chromosome and allows rapid selection of transformants by B. subtilis-specific antibiotic resistance and the yellow fluorescent protein (mVenus) expression. We used the developed iBAC(cav)-mediated system to integrate 10 kb DNA fragment from E. coliK12 MG1655 into B. subtilis chromosome. iBAC(cav)-mediated chromosomal integration approach will facilitate rational design of synthetic biology applications in B. subtilis.

Keywords

  • Bacterial artificial chromosome;
  • Chromosomal integration;
  • λ red recombineering;
  • mVenus;
  • RecA homologous recombination

Using ‘chemical origami’ to generate customisable, high-value chemicals from plants

The following article was originally published on the John Innes Centre news feed: Using ‘chemical origami’ to generate customisable, high-value chemicals from plants. Anne Osbourn is Co-Director of OpenPlant and this work from her group is highly relevant to the efforts of OpenPlant to create toolkits for plant metabolic engineering, but was funded from other sources.

Following the discovery of a new and very valuable enzyme which folds linear molecules into different shapes, scientists at the John Innes Centre are building a ‘triterpene machine’ which will enable them to custom-build valuable chemical compounds called triterpenes and produce them in large, cost-effective quantities. Working with the pharmaceutical, agricultural and biotechnology industries, they hope to improve existing triterpenes to make better medicines with fewer side effects, or improve the specificity of pesticides. They also hope to make completely new, custom-designed triterpenes to any specification, which could lead to development of new anti-cancer drugs, agrochemicals, industrial chemicals or cosmetics.

In the ancient Japanese art of origami, different ways of folding a single sheet of paper can transform it into an aeroplane, a flower, or a bird. Plants perform origami too – not with paper, but with chemical compounds, taking individual precursor molecules and using enzymes to fold and modify them to create many different variations.

For several years, Professor Anne Osbourn of the John Innes Centre has been studying the ‘chemical origami’ that gives rise to a large group of plant compounds called triterpenes, many of which may have valuable uses in the pharmaceutical, agricultural and biotechnology industries.

Professor Osbourn said:

“Some triterpenes are currently used in drinks as foaming agents, but there are many more exciting possibilities – new medical therapies such as anti-cancer drugs, diabetes medicines and antidepressants, for example; anti-fungal agents in crop protection, or cosmetic ingredients. All of the triterpenes we know about are based on a suite of similar molecular ‘scaffolds’ – we want to understand how these scaffolds are made, ‘folded’ and ‘decorated’ so that we might be able to engineer completely new triterpenes to make new medicines and industrial chemicals, or to improve those we already have.”

In a new research article published this week in the scientific journal Proceedings of the National Academy of Sciences, Professor Osbourn, along with colleagues at the John Innes Centre and collaborators from the USA, describes how she discovered an important part of the triterpene origami process, almost by accident.

By analysing oat plants that had been exposed to a DNA-mutating chemical, the researchers “stumbled across” a handful of mutated versions of an enzyme called SAD1. SAD1 is a triterpene synthase enzyme responsible for a critical step in building triterpenes: in its normal form, it takes a linear precursor molecule called 2,3-oxidosqualene (OS for short), and turns it into a pentacyclic scaffold – a molecule with 5 carbon rings. This is then further modified by other enzymes to produce hundreds of different triterpene compounds.

However, one of the mutated forms, which differed from the normal form by one little change in the enzyme’s structure, produced tetracyclic scaffolds with four carbon rings instead – the scaffold for a completely different set of triterpenes. Incidentally, the same mutation in an equivalent gene from a different plant, Arabidopsis thaliana, gave the same results, suggesting that this ‘molecular switch’ from pentacyclic to tetracyclic triterpene production is conserved between different plant species.

Next, the scientists tried putting the mutant SAD1 gene into yeast, a fast-growing, single-celled organism, to see if it could be used to make large quantities of triterpenes. Here, the team discovered that the SAD1 enzyme favoured dioxidosqualene (DOS) as a substrate rather than OS.

“This was an exciting discovery,” said Professor Osbourn, “because we realised that we could not only modify the enzyme to produce different triterpene scaffolds, but we could also modify the building block to make different more highly oxygenated scaffolds.”

The PNAS article presents just one part of ongoing work by the Osbourn lab to harness the power of genes and enzymes to generate high-value chemicals from plants.

Professor Osbourn said:

“Here at the Norwich Research Park we’re building a ‘Triterpene Machine’; a toolkit of molecular parts we can put into yeast, or a recently developed rapid expression system using tobacco leaves, which we hope will allow us to custom-build valuable triterpenes and produce them in large, cost-effective quantities. Working with the pharmaceutical, agricultural and biotechnology industries, we hope we’ll be able to modify known triterpenes to improve their existing applications – to make better medicines with fewer side effects, or improve the specificity of pesticides, for example. We might even be able to make completely new, custom-designed triterpenes to any specification we want, which could provide us with new anti-cancer drugs, agrochemicals, industrial chemicals or cosmetics. The possibilities are potentially endless!”

This research was funded by the Biotechnology and Biological Sciences Research Council, the John Innes Foundation and a Norwich Research Park Studentship Award.


Image by Ftiercel [Public domain], shared via Wikimedia Commons

Gene Discovery for Synthetic Biology: Exploring the Novel Natural Product Biosynthetic Capacity of Eukaryotic Microalgae

OpenPlant PI Professor Rob Field at the John Innes Centre has published work of relevance to those working on algae and microalgae.

O’Neill, G. Saalbach, R.A. Field (2016). Gene Discovery for Synthetic Biology: Exploring the Novel Natural Product Biosynthetic Capacity of Eukaryotic Microalgae. Methods in Enzymology 576, p 99-120.

Abstract

Eukaryotic microalgae are an incredibly diverse group of organisms whose sole unifying feature is their ability to photosynthesize. They are known for producing a range of potent toxins, which can build up during harmful algal blooms causing damage to ecosystems and fisheries. Genome sequencing is lagging behind in these organisms because of their genetic complexity, but transcriptome sequencing is beginning to make up for this deficit. As more sequence data becomes available, it is apparent that eukaryotic microalgae possess a range of complex natural product biosynthesis capabilities. Some of the genes concerned are responsible for the biosynthesis of known toxins, but there are many more for which we do not know the products. Bioinformatic and analytical techniques have been developed for natural product discovery in bacteria and these approaches can be used to extract information about the products synthesized by algae. Recent analyses suggest that eukaryotic microalgae produce many complex natural products that remain to be discovered.


Image credit: microscopic-view-of-microalgae by Learn 2 Teach, Teach 2 Learn on Flick, licensed under CC-BY-NC 2.0