Enzyme boost makes maize heat-tolerant

Sarah Muriithi, a farmer, inspects maize at her farm in Karuga Village in Marmanet, Laikipia County. PHOTO| JOSEPH KURIA| NATION

Scientists have come up with a way of increasing maize productivity by targeting an enzyme involved in photosynthesis.

The maize, according to researchers produces Rubisco, the enzyme involved in photosynthesis. When boosted inside maize cells, it increases crop productivity.

Dr Robert Sharwood from the Centre of Excellence for Translational Photosynthesis at The Australian National University, said the plant from the process has improved photosynthesis and hence, growth.

Through photosynthesis, plants take in light to produce energy. Plants with boosted Rubisco are more tolerant of heat and drought through efficient water use.

"Maize has one of the most efficient Rubiscos and needs less nitrogen to work. So, our main question was, if we increase Rubisco content in maize, what would it do for the plant? We found that by boosting Rubisco inside the maize cells, we get an increase in crop productivity," said Dr Sharwood.

Maize is a staple food for billions of people around the world, with more maize grown annually than rice or wheat. However, maize production is vulnerable to weather variability.

"We developed transgenic maize designed to produce more Rubisco, the main enzyme involved in photosynthesis, and the result is a plant with improved photosynthesis and hence, growth. This could potentially increase tolerance to extreme climate conditions," said Dr Sharwood.


He added that there is an urgent need to deliver new higher-yielding and highly adapted crop species before crops are affected by expected climate change conditions.

"These conditions will increase threats against global food security, and the only way to prepare for them is through international research collaborations," he said.

Dr David Stern, a co-researcher, said that every plant on the planet uses photosynthesis to capture carbon dioxide from the atmosphere, but not all plants do it in the same way.

"Plants like wheat and rice use the ancient, less efficient C3 photosynthetic path, while other plants such as maize and sorghum use the more efficient C4 path.

“These plants are specially adapted to thrive in hot and dry environments, like the ones that are expected to be more prevalent in future decades," he said, adding that the centre of the whole process is Rubisco, the main enzyme of photosynthesis, which is in charge of converting carbon dioxide into organic compounds.

In C4 plants, Rubisco works much faster and they are more tolerant to heat and drought through more efficient water use.

"In our study, we improved carbon dioxide assimilation and crop biomass by 15 per cent, but now we know that we can also increase the pool of active Rubisco and these numbers will increase even higher," he said

"Our next step is to do field trials to see how our maize behaves in real field conditions.

“We have tested them in glasshouse and cabinet conditions, but now we need to go into the next phase," said Dr Sharwood.

The research results were published in the journal Nature Plants.