CRISPR-edited rice plants produce major boost in grain yield

A team of scientists from Purdue University and the Chinese Academy of Sciences has used CRISPR/Cas9 gene-editing technology to develop a variety of rice that produces 25-31 percent more grain and would have been virtually impossible to create through traditional breeding methods. 

The team, led by Jian-Kang Zhu, a distinguished professor in the Department of Horticulture and Landscape Architecture at Purdue and director of the Shanghai Center for Plant Stress Biology at the Chinese Academy of Sciences, made mutations to 13 genes associated with the phytohormone abscisic acid, known to play roles in plant stress tolerance and suppression of growth.

Of several varieties created, one produced a plant that had little change in stress tolerance but produced 25 percent more grain in a field test in Shanghai, China, and 31 percent more in a field test conducted on China's Hainan Island.

Zhu's team silenced suites of pyrabactin resistance 1 (PYR1)/PYR1-like (PYL)/regulatory components of ABA receptor (ACAR) genes, or simply, PYL genes. These genes enhance tolerance of abiotic stresses, such as drought, soil salinity and other environmental factors, but also inhibit growth.

Since plants have evolved to create genetic redundancies, especially for traits required for survival, knocking out one gene in the PYL family might not have much effect on stress tolerance or growth since redundant genes can kick in to provide a similar function. Crafting the right knockout combination, however, led to a plant that uses just the right redundancies to hold onto its stress-tolerance characteristics but reduces the growth inhibition.