Photosynthesis breakthrough could boost food crops

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Researchers have increased plant productivity by boosting levels of three proteins involved in photosynthesis, according to a new study in the journal Science.

In field trials, the scientists saw 14 to 20 percent increases in the productivity of their modified tobacco plants.

Many years of computational analysis and laboratory and field experiments led to the selection of the proteins targeted in the study led by Professor Stephen Long of the University of Illinois and Lancaster University.

The researchers used tobacco because it is easily modified. Now they are focusing on food crops.

They hope eventually the discovery could help address global food shortage.

“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,” said Professor Stephen Long (FRS).

The Professor of Plant Biology and Crop Sciences said: “Crop leaves exposed to full sunlight absorb more light than they can use. If they can’t get rid of this excess energy, it will actually bleach the leaf.”

Plants protect themselves by making changes within the leaf that dissipate the excess energy as heat. This process is called ‘nonphotochemical quenching’ or NPQ.

“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,” said Professor Long. “In the shade, the lack of light limits photosynthesis, and NPQ is also wasting light as heat.”

The research team used a supercomputer 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.

Professor Long’s discussions with University of California, Berkeley researcher and study co-author Krishna Niyogi – an expert on the molecular processes underlying NPQ –suggested that boosting levels of three proteins might speed up the recovery process.

To test this concept, the team inserted a “cassette” of the three genes (taken from the model plant Arabidopsis) into tobacco.

“The objective was simply to boost the level of three proteins already present in tobacco,” said Professor Long.

The researchers grew seedlings from multiple 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 upon transfer 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.

Postdoctoral researchers Katarzyna Glowacka and Johannes Kromdijk also worked on the study.

“Tobacco is grown for its leaves, which were substantially increased,” Johannes Kromdijk said. “But in food crops, it will be whatever we eat from the plant – the fruit, the seeds or the roots – that we will need to increase.”

Other experiments have demonstrated that increasing photosynthesis by exposing plants to high carbon dioxide results in more seed in wheat, soy and rice, he said.

“Now we can do this genetically, and we are actively working on repeating our work in various food crops,” he said.

The new results are a proof-of-concept that photosynthesis can be made more efficient, and that this does result in more crop productivity – something the scientific community once doubted, said Katarzyna Glowacka.

“This finding offers some rare good news at a time of dire forecasts of future food shortages,” she said.

“The United Nations predicts that by 2050, we’re going to need to produce about 70 percent more food on the land we’re currently using,” said 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 farmers’ fields. If we don’t do it now, we won’t have this solution when we need it.”

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.

The picture shows Professor Stephen Long (FRS) at the Lancaster Environment Centre

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