A big step towards more efficient photosynthesis

18th Sep 2014

For the first time flowering plants have been successfully engineered to fix carbon like the blue-green algae do – this can potentially increase photosynthesis and yields in crop plants.

Plants, algae and some bacteria capture light energy from the sun and transform it into chemical energy by the process named photosynthesis. Blue-green algae (cyanobacteria) have a more efficient mechanism in carrying out photosynthesis than plants. For a long time now, it has been suggested that if plants could carry out photosynthesis with a similar mechanism to that of the blue-green algae, plant productivity and hence crop yields could improve.

Rothamsted Research scientists strategically funded by the BBSRC and in collaboration with colleagues at Cornell University funded by the U.S. National Science Foundation have used genetic engineering to demonstrate for the first time that flowering plants can carry out photosynthesis utilizing a faster bacterial Rubisco enzyme rather than their own slower Rubisco enzyme. These findings represent a milestone toward the goal of improving the photosynthetic rate in crop plants. The study is published in Nature.

In order to engineer the bacterial genes to work properly in plants, postdoctoral fellow Dr Myat Lin at Cornell used recombinant DNA methods to connect the bacterial DNA to plant DNA sequences so that several bacterial proteins could be produced simultaneously in chloroplasts and successfully assemble into a functional enzyme.

Dr Lin said: "In order for this project to succeed, it was essential to carefully engineer the cyanobacterial genes so that they would be expressed at sufficient levels to support photosynthesis."

Dr Alessandro Occhialini, Rothamsted Research scientist, applied sophisticated microscope techniques to observe the exact position of the enzyme within the tobacco plant chloroplasts. Moreover he tested the in vitro enzymatic activity of cyanobacterial Rubisco extracted from tobacco leaves. "I was thrilled to see that these tobacco lines were photosynthetically competent and that the faster cyanobacterial enzyme was active in plant tissue. These engineered plants represent a very important step towards the improvement of plant photosynthetic performance," he said.

Professor Maureen Hanson, lead scientist at Cornell University said: "The plants we have developed in this study are extremely valuable for further enhancing photosynthesis by surrounding the cyanobacterial Rubisco with a microcompartment called the carboxysome. Our next step is to add the proteins required to form the carboxysome in the chloroplast, as we described earlier this year in the Plant Journal."

Professor Martin Parry, lead scientist at Rothamsted Research, said: "We are truly excited about the findings of this study. Wheat yields in the UK in recent years have reached a plateau. In order to increase wheat yields in a sustainable manner in the future, we are looking at a variety of approaches that include changes within the plant as well as in terms of the surrounding environment of the plant. The present study has been undertaken in a model plant species and it represents a major milestone. Now we have acquired important knowledge and we can start taking further steps towards our goal of turbo-charging photosynthesis in major crops like wheat."

Professor Jackie Hunter, BBSRC Chief Executive, commented: "Photosynthesis is the basis for almost all life on Earth, yet it has the potential to use the sun's energy so much more efficiently. There is a great opportunity for improvement and this study and other research is working towards realising a potential that could benefit us in many diverse ways, from producing more food to fuels, materials, useful chemicals and much more."

Dr Kent Chapman, Programme Director at National Science Foundation (NSF) commented: "This US/UK team of plant biologists has replaced the key carbon-dioxide-fixing gene in photosynthesis that is present in tobacco plants with a more efficient version from a cyanobacterium. This novel achievement marks a major step toward enhancing the process of photosynthesis in crop plants for improved growth and overall yields, and is a great example of the value of international collaboration."

The funding was awarded by the UK Biotechnology and Biological Sciences Research Council (BBSRC) and the US National Science Foundation (NSF) as part of the Photosynthesis Ideas Lab programme: a pioneering undertaking to enable the best minds from the USA and UK to join forces to explore this important area.

Publication: A faster Rubisco with potential to increase photosyntheis in crops. Nature, 17 September 2014.

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