Quantitative regulation of Waxy expression by CRISPR/Cas9-based promoter and 5’UTR-intron editing improves grain quality in rice
Host: Tan Yan
Date: 24 Nov 2021
In cereal crops, grain starches are composed of different proportions of amylose and amylopectin, which determine the cooking and eating qualities. The amylose synthesis is controlled by the Waxy (Wx) gene encoding a granule bound NDP-glucose- starch glucosyltransferase (Shure et al., 1983). In rice (Oryza sativa L.), the varied activities of natural Wx alleles regulate different amylose contents (AC), gel consistency (GC) and pasting viscosity of grain starches; these factors together influence the grain appearance, cooking/eating quality and starch physical characters (Zhang et al., 2019). Wxa is a strong allele mainly distributing in indica (an O. sativa subspecies) cultivars producing high ACs (25%–30%) (Wang et al., 1995). While Wxb, presenting mainly in japonica (another subspecies) cultivars, is a weak allele producing moderate ACs (15–18%) (Isshiki et al., 1998). Generally, rice grains with higher ACs and lower GC values have poor eating quality, while those with moderate ACs (15–20%) and higher GC values (60–80 mm) give better taste for most consumers. Using the successive backcrossing methods, Wxb can be introgressed into indica varieties to improve the grain quality. However, the traditional breeding methods are time consuming and difficult to break close linkage drags with undesirable traits.