Allelic variations in the soluble starch synthase II gene family result in changes of grain quality and starch properties in rice (Oryza sativa L.)

Abstract

SUMMARYSoluble starch synthase II (SSII) plays an important role in the biosynthesis of starch and in rice it consists of three isoforms encoded by SSII-1, SSII-2 and SSII-3. However, the genetic effects of various SSII alleles on grain quality have not been systematically characterized. In the present study, the japonica alleles on SSII-1, SSII-2 and SSII-3 (SSIIa) loci from a japonica cultivar, Suyunuo, were respectively introgressed by molecular marker-assisted selection into a typical indica cultivar, Guichao2, through successive backcrossing, generating three sets of near-isogenic lines (NILs). Grain quality and starch property analysis showed that NIL-SSII-3j exhibited significant decreases in the following parameters: amylose content, average granule size, and setback viscosity and consistency; but increases in peak viscosity, hot paste viscosity, gelatinization temperature and relative crystallinity. Moreover, the proportion of short amylopectin chains and branching degree also increased when compared with those of NIL-SSII-3i (Guochao2). Similar effects were observed in NIL-SSII-1j, and certain alterations in the fine structure of starch (granule size) were revealed. However, NIL-SSII-2j did not exert significant effect on grain quality and starch properties. In brief, among the SSII gene family, the functional diversity occurred on SSII-1 and SSII-3, and not on SSII-2. Therefore, it appears that more attention should be directed to SSII-1 and SSII-3 loci for improving the eating and cooking quality of rice.

Association Analysis of Markers Derived from Starch Biosynthesis Related Genes with Starch Physicochemical Properties in the USDA Rice Mini-Core Collection

“…This type of inconsistency suggested that compared to Waxy and SSIIa genes, these markers may have minor or environment-dependent effects on starch traits. For further evaluation of their roles in determining starch characteristics, constructing near-isogenic-lines could be a suitable approach, as demonstrated in recent reports (Luo et al, 2015; Fan et al, 2017). …”

“…Recently, Fan et al (2017) also detected the effect of SSIIa gene on AAC and viscosity parameters using near-isogenic lines. Thus, the effect of SSIIa gene on AAC-related traits could not be purely attributed to gene linkage effect although the SSIIa GC SNPs were found associated with the G SNP of intron 1 in Waxy gene in most cases in this study (103 out of 137, 75.2% percent).…”

Starch Components, Starch Properties and Appearance Quality of Opaque Kernels from Rice Mutants

“…Rice is one of the most important crops, and provides the staple food for over half the world's population. Starch is the main component of rice endosperm, and its properties greatly influence the eating and cooking qualities of rice and its processing method in industrial use [1][2][3]. Therefore, the cultivation of rice varieties with different starch properties is one of the important goals in rice breeding.…”

QTL mapping for Q-enzyme activity during grain development in rice

“…Starch biosynthetic genes played important roles for starch properties in a RIL population which was originated from the cross, IR64/Nipponbare (Luo et al 2015). Allelic variation in the soluble starch synthase II gene family is important for grain quality and starch properties (Fan et al 2017). In addition, genes that encode for rice starch branching enzyme IIb were identified through MutMapPlus (Nakata et al 2017).…”