Diversification of the Waxy Gene is Closely Related to Variations in Rice Eating and Cooking Quality

Abstract

The Wx gene encoding granule-bound starch synthase is responsible for the biosynthesis of amylose, which plays an important role in determining rice eating and cooking quality. However, the functional evaluation of different Wx alleles remains unclear. In the present study, a set of near-isogenic lines (NILs) carrying four different Wx alleles—Wx a , Wx b , Wx in , and wx—was developed in the genetic background of indica rice cv. Yangfunuo 4 (YFN 4), and designated NIL-Wx a , NIL-Wx b , NIL-Wx in , and NIL-wx, respectively. These NILs show great variations in amylose content (AC), gel consistency (GC), starch viscosity, and thermodynamic property. AC showed the following trend among different NILs: NIL-Wx a > NIL-Wx in > NIL-Wx b > NIL-wx, but the opposite trend for GC. NIL-Wx a and NIL-Wx in had lower starch thermodynamic properties, such as onset temperature, peak temperature, and conclusion temperature, when compared with both NIL-Wx b and NIL-wx. The transcript and protein of Wx gene were not detectable in the NIL-wx line. The accumulation levels of Wx transcript and Wx protein were higher in NIL-Wx a than those in NIL-Wx b and NIL-Wx in . Therefore, Wx gene was closely related to starch quality parameters, such as AC, GC, starch paste viscosity, and starch thermodynamic property. Our results provide a solid foundation for rice grain quality improvement through marker-assistant selection.