A team of scientists from Purdue University and the Chinese Academy of Sciences has used CRISPR/Cas9 gene-editing to develop a rice variety that produces 25-31 percent more grain and would have been virtually impossible to create through traditional breeding.
The team, led by Jian-Kang Zhu, a distinguished professor in Purdue’s Department of Horticulture and Landscape Architecture and director of the Shanghai Center for Plant Stress Biology at the Chinese Academy of Sciences, made mutations to 13 genes associated with the plant hormone abscisic acid. It is known to play roles in plant stress tolerance and growth suppression.
Of the several rice varieties created, one produced a plant that had little change in stress tolerance but yielded 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.
Their findings were published recently in the “Proceedings of the National Academy of Sciences.”
Zhu’s team, which includes Purdue’s Ray A. Bressan, a distinguished professor in the Department of Horticulture and Landscape Architecture, and researchers from the Chinese Academy of Sciences, silenced groups of PYL genes that enhance tolerance to abiotic stresses, such as drought, soil salinity and other environmental factors. These genes 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.
“There is lots of evidence that although each PYL gene may have an individual specialty in function, by and large they also share some common functions,” Zhu says. “When you remove one, others will function as a replacement.”
The CRISPR/Cas9 technology allows plant breeders to quickly and accurately snip portions of DNA out of a sequence, editing the DNA code. The method allowed Zhu’s team to modify multiple genes at one time, something that would have taken decades to do with traditional methods without a guarantee that the resulting plants would have the desired characteristics.
The improved rice plants created in these experiments come from a common research line. The next step is to use CRISPR/Cas9 to edit the same genes in elite varieties of rice to determine if those will also show similarly improved yield.
“If this holds true for the varieties that farmers currently use, this big increase in yield would be very important,” Zhu says. “It would really help produce a lot more grains to feed more people.”
This information was provided by Purdue University.