Breakthrough in Photosynthesis Leads to Crop Increases

21 Nov 2016 --- Scientists from the University of Illinois have made a major breakthrough they believe could be used to feed the growing global population - tweaking photosynthesis in plants to boost crop yields. Increasing plant productivity is a key element in the challenge to produce enough food to feed the predicted 9.7 billion people living in the world by 2050. And thanks to research and field trials by plant biology and crop sciences professor Stephen Long, we could be a lot closer to figuring out how to do it. 

The research team report in the Journal Science that they can step-up three proteins involved in photosynthesis, with field trials results showing an increase of 14 percent to 20 percent in the growth of their modified tobacco plants. The hypothesis that photosynthesis can be made more efficient to increase plant yield has been doubted by some in the science field, but the study involving several years of computational analysis and laboratory and field experiments led to the selection of the proteins targeted in the study. Now other crops can be used as part of the research.

“It had always been my goal, once we understood the basics of photosynthesis, that we start putting it back together We are also beginning to understand ways to improve in terms of re-adapting it to the climate that we have now, but also improving on what evolution delivered to us to work with and so we have a lot of understanding now of what we might be able to do to improve photosynthesis and thereby improve crop productivity and food security around the world.” says Professor Donald Ort, of the University of Illinois. 

To improve photosynthesis and the efficiency with which the crop might convert sunlight into food, the team represented 140 steps on a computer so they could simulate the whole process to know which ones might be the best to experimentally change. 

Tobacco was selected as the easiest plant in terms of its molecular biology and genomics and it’s large enough to test in the field to achieve proof of concept. The next steps are to target rice, soya beans and cassava, three important crops in sub-Saharan Africa. 

“Arguably photosynthesis is the most important process on our planet, it is the driving force of all of life, it’s the source of energy for all of life. It’s not only our source of food but it’s also where the oxygen on the planet actually came from. We wouldn’t be here today if it wasn’t for photosynthesis. Because population is rising and the global population is becoming far more urban, the UN Food and Agricultural Organization predict that by 2050 we’re going to need 70 percent more food than we are producing today,” adds Professor Long.

“My attitude is that it is very important to have these new technologies on the shelf now because it can take 20 years before such inventions can reach farmer’s fields. If we don’t do it now, we won’t have this solution when we need it.”

“But you have to bear in mind that any innovation we make today in producing ore food is not going to be in farmer’s fields in any scale for probably 20 years so with the forecasts of increased global demand, if we don’t start today when food shortages start to appear in 20 years time, it will be too late.”

The team targeted a process plants use to shield themselves from excessive solar energy.

“Crop leaves exposed to full sunlight absorb more light than they can use. If they can’t get rid of this extra energy, it will actually bleach the leaf.”

Plants protect themselves by making changes within the leaf that dissipate the excess energy as heat, he said. This process is called nonphotochemical quenching.

“But when a cloud crosses the sun, or a leaf goes into the shade of another, it can take up to half an hour for that NPQ process to relax. In the shade, the lack of light limits photosynthesis, and NPQ is also wasting light as heat.”

Using a supercomputer at the National Center for Supercomputing Applications at the university to predict how much the slow recovery from NPQ reduces crop productivity over the course of a day, these calculations revealed “surprisingly high losses” of 7.5 percent to 30 percent, depending on the plant type and prevailing temperature, Long says. 

After discussions with expert on the molecular processes underlying NPQ and study co-author, Krishna Niyogi, it was suggested that boosting levels of three proteins might speed up the recovery process and to test this concept the team inserted a “cassette” of the three genes (taken from the model plant Arabidopsis) into tobacco.

Seedlings were then grown from multi experiments, then tested how quickly the engineered plants responded to changes in available light. A fluorescence imaging technique allowed the team to determine which of the transformed plants recovered more quickly when transferred to shade. The researchers selected the three best performers and tested them in several field plots alongside plots of the unchanged tobacco.

Two of the modified plant lines consistently showed 20 percent higher productivity, and the third was 14 percent higher than the unaltered tobacco plants.

“We don’t know for certain this approach will work in other crops, but because we’re targeting a universal process that is the same in all crops, we’re pretty sure it will.”

Other experiments have demonstrated that increasing photosynthesis by exposing plants to high carbon dioxide results in more seeds in wheat, soy and rice. Now the researchers can do this genetically and work on repeating the techniques in various food crops - which could significantly impact forecasts of future food shortages. 

The Bill and Melinda Gates Foundation funded this research, with the stipulation that any new agricultural products that result from the work be licensed in such a way that the technology is freely available to farmers in poor countries of Africa and South Asia.