Maintaining the quality and yield of crops adapted to lower temperatures will increasingly become a huge challenge as global temperatures continue to rise. Rice is one crop that is known to be affected by higher nighttime temperatures, especially during the ripening phase. Rice crops can exhibit a condition known as “chalkiness” due to heat stress.
Chalkiness is described as a condition where the rice granule is less compact due to the decreased concentration of starch. This can result in lower milling yields, cooking quality, and overall market value.
Researchers at the University of Arkansas and the University of Arkansas System Division of Agriculture (UADA) have published a new paper in the Plant Journal that may offer a remedy to both heat-induced and genetic chalkiness. Titled “Targeted mutagenesis of the vacuolar H+ translocating pyrophosphatase gene reduces grain chalkiness in rice,” the paper details how the team of researchers was able to gene edit a strain of japonica rice to reduce chalkiness.
Using the CRISPR-Cas9 gene-editing technology, the researchers specifically targeted a gene that encodes vacuolar H+ translocating pyrophosphatase (V-PPase), an enzyme known to play a role in increasing grain chalkiness. They were able to reduce the expression of V-PPase by editing a promoter element, which controls how much it is expressed.
The mutated rice lines resulted in a 7 to 15-fold decrease in chalkiness, depending on the strain of rice, with a consequent increase in grain weight. Even under increased nighttime temperatures, the results held up. The mutated lines showed a clear improvement in rice quality as they exhibited the more compact packing of starch granules and the formation of translucent (as opposed to chalky) rice grains.
The paper’s first author, Peter James Icalia Gann, a Fulbright Scholar in the Cell and Molecular Biology Program, and co-author, Vibha Srivastava, a professor in the Department of Crop, Soil and Environmental Sciences who has a joint appointment with the U of A and the UADA, filed for a provisional patent as the process used to improve rice quality was novel enough.
“If we want to sustain life on our planet, it is really important to identify solutions to problems in our food systems that are coming with increasing average temperatures,” Gann said. “We were really excited to share our findings that utilized gene-editing in rice to improve grain quality that remains consistent — even under heat stress.”
Additional co-authors included Dominic Dharwadker, an honors student in chemistry and biochemistry at the U of A, as well as Sajedeh Rezaei Cherati, Kari Vinznat, and Mariya Khodakovskaya with the Department of Biology at the University of Arkansas, Little Rock.