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Increasing food and fuel production – thinking outside the box

27 September 2011

New research projects, announced by BBSRC in September, aimed at overcoming some of the fundamental limitations to exploiting photosynthesis could lead to major increases in crop yields for food, bioenergy and in the production of renewable chemicals.

The world faces significant challenges in the coming decades, and chief among these are producing enough sustainable and affordable food for a growing population and replacing diminishing fossil fuels. Even a small change to the efficiency of photosynthesis - the process by which plants, algae and some bacteria use the sun's energy to make sugars - would make a huge impact on these problems. Yet, despite developing an increasingly detailed picture of photosynthetic mechanisms, research has so far failed to deliver any real gains.

In September 2010, BBSRC held an 'Ideas Lab' activity with the US National Science Foundation (NSF), bringing together the best researchers from the UK and US in order to explore new ideas and novel approaches in the photosynthesis research field.

Science Minister David Willetts said: "Food security is an important issue for governments and researchers worldwide, and it's great to see UK scientists contributing to such a valuable body of international research. If we can gain a better understanding of the scientific processes underlying food production, we are a significant step closer to being able to support an increasing global population in future."

Biochemist Professor Richard Cogdell from the University of Glasgow, who acted as a mentor for the Ideas Lab said, "Trying to improve photosynthesis is challenging both scientifically in itself and because it requires the coming together of engineers, physicists, chemists as well as more traditional biologists. The new targeted programme in this area has allowed real innovative, 'out of the box' projects to be explored in a very exciting way."

As a result of the Ideas Lab, BBSRC and NSF announced the award of four trans-Atlantic multi-centre research projects worth over £6.M earlier this year. And last month BBSRC awarded a further £2M to UK researchers through a complementary call. The challenge of all nine projects is to achieve a step change in photosynthesis.

Surpassing evolution

Together, the nine research projects span the whole photosynthetic pathway, from the shape of the crop canopy and the structure of individual leaves through to light capture at the molecular level and the production and storage of sugars.

For example, Professor Nicholas Smirnoff from the University of Exeter is trying to improve a reaction driven by the enzyme Rubisco - widely recognised as a bottleneck in the photosynthetic pathway. He wants to see whether making the cell environment richer in carbon dioxide will allow Rubisco to work more efficiently, in a complementary approach to the Ideas Lab projects on the same topic. Working with the photosynthetic bacterium Synechocystis, the team plan to test this hypothesis by linking Rubisco to another enzyme that concentrates CO2. If successful, the idea is to improve Rubisco activity in a similar manner in a range of crops including rice, wheat, potatoes and pulses.

Whilst at the University of Manchester, Professor Giles Johnson is investigating the role of fumaric acid as a temporary carbon store (in addition to starch) in order to prevent the build up of sugar molecules in the leaf that would otherwise inhibit photosynthesis.

One of the drivers for BBSRC was fostering the development of multidisciplinary teams. We are encouraging a collaborative approach by holding regular workshops with researchers from all nine projects, in both the UK and US, so that they work together from an early stage.

"It's ambitious, but if the scientists we are supporting can achieve their aims it will be a profound achievement," says BBSRC Director of Research Janet Allen.

About the projects

The projects funded by this round of grants are:

Enhancing Photosynthesis Parallel Call: Funded Grant Abstracts Metabolic engineering to enhance photosynthesis based on empirical data and in silico modelling - Professor Christine Raines, University of Essex.
Over the last decade numerous experiments on plants grown in elevated CO2 have shown unambiguously that increased rates of photosynthetic carbon assimilation can lead to increased biomass. Furthermore transgenic experiments conducted during the 1990's in which activities of individual enzymes were up- or down-regulated provided information showing that manipulation of the Calvin cycle could influence plant composition and increase plant productivity. These studies clearly identified photosynthetic carbon assimilation as an untapped opportunity to increase yield. In this project we will produce transgenic Arabidopsis plants with altered photosynthetic characteristics based on a combination of empirical data, metabolic and network modelling. A detailed physiological and molecular analysis of the resulting lines will carried out to obtain detailed measurements of photosynthetic parameters and growth in greenhouse grown plants. The transgenic plants generated in this programme with altered photosynthetic carbon metabolism will be used to explore the relationships between CO2 assimilation, carbon storage and plant growth. These analyses will provide data for further interrogation and improvement of these models. This research will also provide a proof of concept and will form the basis to enable informed manipulation of crop plants.

Decreasing the oxygenase activity of Rubisco: a synthetic biology approach - Professor Nicholas Smirnoff, University of Exeter.
We are proposing a pilot study to assess the potential of physically linking the enzyme Rubisco, which has an important role in photosynthesis, to another enzyme (carbonic anhydrase, CA) which, under the right conditions, could deliver a high concentration of carbon dioxide to Rubisco and reduce the wasteful oxygenase activity. To achieve this aim we propose to reconfigure the carbon dioxide fixing step of photosynthesis by engineering the bacterium Synechocystis. We will prepare a synthetic gene which, when introduced into Synechocystis will cause it to produce a protein scaffold that can bind both Rubisco and CA. The modified strain will also contain forms of Rubisco and CA that have been engineered with tags that allow them to bind to the scaffold protein. This engineered organism will allow us to test the proposal that close proximity of Rubisco and CA increases the efficiency of photosynthesis by decreasing the "wasteful" oxygenase activity.

Enhancing leaf transient carbon stores - role of fumarate as a possible storage compound - Dr Giles Johnson, University of Manchester.
If the concentration of the sugars produced by photosynthesis becomes too high, this can slow down or stop photosynthesis. To overcome this effect, plants can convert sugars into different substances, in particular starch. Starch is relatively unreactive and does not inhibit photosynthesis. The rate at which starch can accumulate and the amount that the leaf can hold is currently metabolically limited. So, if a plant does more photosynthesis, starch accumulation cannot keep up and sugar concentrations will increase and photosynthesis will then become inhibited.

Work in a weed called Thale Cress has identified, in addition to starch, a novel storage compound fumaric acid. Fumaric acid is a natural substance, found in all organisms including humans. It is widely used as a food additive to control the acidity of food and drink products. Although all plants contain fumaric acid, only a few are able to store high concentrations. In most crop species, only low amounts are found. If we could breed crops that, in addition to starch, are able to store fumaric acid in their leaves, we may be able to increase plants' ability to carry out photosynthesis.

Removing the inefficiencies of 3-dimensional canopy photosynthesis by the alteration of leaf light-response dynamics and plant architecture - Dr Erik Murchie, University of Nottingham.
Productivity is the sum total of a large number of leaves in a canopy, many of which shade (or partly shading each other) and are usually different ages. We can calculate the potential productivity of whole canopies based on leaf photosynthetic attributes and other physical and physiological factors. When we do this the theoretical productivity tends to be much higher than the measured productivity. The reasons are unclear but a large part is thought to be due to the way leaves respond when re-constructed into a large 3D canopy. In this state, plants exist as a community which has emergent properties that we cannot necessarily predict from plants grown individually. If we can eliminate the gap between the theoretical and measured productivity we can achieve a step change in productivity.

We hope to take good 3D images of crop canopies, both still and moving, calculate the typical changes in light intensity that occur in that canopy and then change photosynthetic dynamics so that it matches those changes.

Optimising Photosynthetic Efficiency via Leaf Structure - Professor Andrew Fleming, University of Sheffield and Professor Sacha Mooney, University of Nottingham.
The form of the leaf is important for photosynthesis since it will directly influence the efficiency of the process. For example, carbon dioxide in the atmosphere must first enter a leaf by small pores on the leaf surface (stomata), then traverse the inside of the leaf via air spaces before reaching the cells where the chloroplasts are located, which is where photosynthesis occurs. Even though these distances may seem quite small, differences in this internal pathway of carbon dioxide movement can have a major affect on the efficiency of photosynthesis. The aim of this project is to understand more about the rules which link the efficiency of photosynthesis and the internal cellular architecture of a leaf. By knowing more about these rules, we will be in a stronger position to select new breeds of plant which can perform photosynthesis more efficiently The research will form part of Project Sunshine, an initiative led by the Faculty of Science at the University of Sheffield. Project Sunshine aims to unite scientists across the traditional boundaries in both the pure and applied sciences to harness the power of the Sun and tackle the biggest challenge facing the world today: meeting the increasing food and energy needs of the world´s population in the context of an uncertain climate and global environment change. It is hoped that Project Sunshine will change the way scientists think and work and become the inspiration for a new generation of scientists focused on solving the world´s problems.

Contact

Riaz Bhunnoo

tel: 01793 442194