Genetic code to increase the size of rice grain cracked

Looking for ways to enhance rice yield, Indian plant biologists have cracked a novel genetic code that could nearly double the length of a rice grain.

As a consequence, the yield per every rice plant would increase, providing the country with yet another option to augment rice productivity.

While India has the world's largest rice acreage with every state cultivating paddy, the overall productivity is low compared to China, Japan, Korea, the USA and Indonesia.

The Indian productivity is little more than 2,000 kg per hectare which is far less compared to others.

Researchers at the National Institute of Plant Genome Research, Delhi have now identified a rice gene named OsMed15a that has the potential to transform the landscape as it plays a key role to regulate the rice grain size and consequently the yield. A tweak of the gene can make the rice grains bigger.

Globally scientists are yet to fully comprehend the complex biochemical mechanism that lies behind the process to determine the grain size and weight in rice, though important roles played by several genes and proteins are known.

“Our understanding about the molecular mechanism is full of gaps. We don't know how different regulators coordinate to regulate the size and shape of the grain. The genetic and molecular interactions between these regulators are not yet known. In this context, our study is very significant,” NIPGR scientist Jitendra K Thakur, who led the team, told DH.

Thakur and his colleagues at NIPGR have discovered a genetic switch, which can be turned on or off in order to control the grain size. Once turned on, the gene can influence several other molecular behaviours related to grain growth in the rice plant.

“When we suppressed the expression of the gene (OsMed15a), the seeds became smaller and wider. On the other hand, its over-expression makes the rice seeds bigger. Thus expression level of the gene has a profound effect on rice grain size and weight,” he said.

Buoyed by early success in the laboratory, the NIPGR team has tied up with Indian Institute of Agriculture Biotechnology, Ranchi — one of the Indian Council of Agriculture Research units— to create rice plants with the gene turned-on through the standard breeding methods.

"We hope to nearly double the grain size, from about 5 mm to nearly 10 mm," Thakur said.

This, however, may take several months as standard breeding techniques are time consuming. Meanwhile, a part of the NIPGR team's research has been accepted for publication in the journal BBA - Gene Regulatory Mechanisms.