Experts identify the molecular recipe for heat-resistant wheat crops

Experts at Lancaster University have been studying wheat plants to understand how they could be protected from heat stress on a molecular level. The research may ultimately lead to the development of wheat crops that can tolerate the rising temperatures associated with climate change. 

Just as smart thermostats can tell air conditioners when to switch on and off, plants have Rubisco activase (Rca) to switch on the energy-producing enzyme Rubisco when to kick on when there is plenty of sunlight. Then, when the leaf is deprived of light, Rca signals the enzyme to shut off to conserve energy.

The Lancaster researchers have determined that swapping just one molecular building block of Rca in wheat crops can enable the system to activate Rubisco faster when temperatures rise. This presents scientists with a great opportunity to help protect wheat crops from global warming. 

The research project, Realizing Increased Photosynthetic Efficiency (RIPE), was led by Elizabete Carmo-Silva, a senior lecturer at the Lancaster Environment Center. The RIPE project is focused on engineering crops to be more productive by improving photosynthesis. 

“We took a wheat Rca (2β) that was already pretty good at activating Rubisco in lower temperatures and swapped out just one of its amino acids with one found in another wheat Rca (1β) that works pretty well in higher temperatures but is rubbish at activating Rubisco — and the result is a new form of 2β Rca that is the best of both worlds,” said Carmo-Silva.

According to the researchers, naturally occurring wheat Rca 1β has an isoleucine amino acid and works up to 39 degrees Celsius, but is not very effective in activating Rubisco. On the other hand, 2β has a methionine amino acid, works up to about 30 degrees Celsius, and is very good at activating Rubisco. 

The team has engineered a new version of 2β for wheat crops. The modified Rca has an isoleucine amino acid that works up to 35 degrees Celsius and can sufficiently activate Rubisco.

“Essentially, 1β is a rubbish enzyme and 2β is sensitive to higher temperatures,” said Carmo-Silva. “The cool thing here is that we have shown how this one amino acid swap can make Rca active at higher temperatures without really affecting its efficiency to activate Rubisco, which could help crops kickstart photosynthesis under temperature stress to churn out higher yields.”

The findings will support RIPE’s efforts to improve wheat crops, as well as other food crops like cowpeas and soybeans.

“When looking at cowpea growing regions in Africa, it goes all the way from South Africa with an average around 22 degrees Celcius to Nigeria at about 30, and areas further north get to 38,” said Carmo-Silva. 

“If we can help Rubisco activate more efficiently across these temperatures, that is really powerful and could help us close the gap between yield potential and the reality for farmers who depend on these crops for their sustenance and livelihoods.”

The RIPE project is funded by the Bill & Melinda Gates Foundation, the U.S. Foundation for Food and Agriculture Research (FFAR), and the U.K. Government’s Department for International Development (DFID).

The study is published in The Plant Journal.

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By Chrissy Sexton, Earth.com Staff Writer