Generating waxy rice starch with target type of amylopectin fine structure and gelatinization temperature by waxy gene editing

Waxy rice, which lacks amylose, is an important variant in rice, and its starches have been widely used. New waxy rice varieties generated via the CRISPR/Cas9 gene-editing system is described. Herein, four waxy rice starches with different physicochemical properties were successfully obtained by the CRISPR/Cas9 editing Waxy (Wx) gene. The results showed that the amylose content (AC) of wx mutant starches ranged from 0.26 to 1.78 %, and CZBwx1 starches had the best gel consistency and highest water solubility among all wx mutants. Mutations of Wxb allele produced more short-chains (degree of chain polymerization (DP) 6-11), and less medium-and long-chains (DP12-70) than that of Wxa, while the AC of Wxa allele mutants was higher than the mutations of Wxb allele. The gelatinization temperature (GT) of wxa mutant starches was higher than that of wxb mutant starches. Moreover, we found that the GT and amylopectin fine structure type of waxy rice starch did not change after Wx gene editing. Based on these findings, it is possible to produce waxy rice starch with different physi-cochemical properties, containing target GT and chain length distributions of amylopectin.

Automated summary

Four waxy rice starches with different physicochemical properties were successfully obtained using the CRISPR/Cas9 gene-editing system, and CZBwx1 starches exhibited the best gel consistency and highest water solubility. Mutations of the Wxb allele resulted in a decrease in medium-and long-chains (DP12-70) and an increase in short-chains (DP 6-11), while mutations of the Wxa allele led to a higher amylose content (AC) compared to Wxb allele mutations. The gelatinization temperature (GT) of the wxa mutant starches was higher than that of the wxb mutant starches, and the GT and amylopectin fine structure type of waxy rice starch remained unchanged after Wx gene editing.