Scientists closer to developing heat-tolerant wheat

Lancaster University researchers working on molecular-level responses in crops are one step closer to producing heat-tolerant wheat, to help protect crops from rising temperatures. Much like smart thermostats tell air conditioners to switch on when the sun is bearing down in the summer and when to shut down to conserve energy, plants have Rubisco activase (Rca). Rca tells the plant’s energy-producing enzyme (Rubisco) to kick on when the sun is shining and signals it to stop when the leaf is deprived of light to conserve energy.

A study from Lancaster University, published in The Plant Journal, reports that swapping one molecular building block out of 380 that make up an Rca in wheat enables it to activate Rubisco faster in hotter temperatures, which could help protect crops.

“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 Elizabete Carmo-Silva, a senior lecturer at the Lancaster Environment Centre who oversaw this work for a research project called Realising Increased Photosynthetic Efficiency (RIPE).

From left, Senior Lecturer Elizabete Carmo-Silva, Research Technician Dawn Worrall and Graduate Student Gustaf E Degen from Lancaster University discovered that swapping just one amino acid creates a better helper enzyme that can trigger photosynthesis more efficiently at higher temperatures in wheat. Image credit: RIPE Project.

RIPE, supported by the Bill & Melinda Gates Foundation, is engineering crops to be more productive by improving photosynthesis, the natural process all plants use to convert sunlight into energy and yields.

The study from Lancaster University found that naturally occurring wheat Rca 1β has an isoleucine amino acid, works up to 39°C, but is not great at activating Rubisco. Conversely, the naturally occurring 2β has a methionine amino acid, works up to about 30°C, and is good at activating Rubisco. Researchers have created a new version of 2β with an isoleucine amino acid that works up to 35°C and is good at activating Rubisco.

“Essentially, 1β is a rubbish enzyme and 2β is sensitive to higher temperatures. 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,” Carmo-Silva said.

This work was carried out in vitro in E. coli. The findings will support RIPE’s efforts to characterise and improve the Rca of other food crops such as cowpea and soybean, each with multiple different forms of Rca.

Researchers analysed cowpea growing regions in Africa, and found that helping Rubisco activate more efficiently at higher temperatures could help close the gap between yield potential and the reality for farmers who depend on these crops for sustenance.