A research team from Purdue University and the Chinese Academy of Sciences
has developed a rice variety that produces 25-31 percent more grain using
CRISPR-Cas9 gene editing technology.

The team, led by Jian-Kang Zhu, 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 abscisic acid, known to play roles in plant stress
tolerance and suppression of growth. From the varieties that were developed,
one variety exhibited a little change in stress tolerance, but produced 25%
more grain in a field test in Shanghai, China, and 31% more in a field test
conducted on China's Hainan Island.

The researchers 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.
Knocking out one gene in the PYL family might not have much effect on stress
tolerance or growth since redundant genes can provide a similar function. A
specific knockout combination, however, led to a variety that uses just the
right redundancies to hold onto its stress-tolerance characteristics but
reduces the growth inhibition.

The improved rice plants came from a common research line. The team's next
step is to to use CRISPR-Cas9 to edit the same genes in elite varieties of
rice to determine if those will also show improved yields.

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