Genetic Effects of Soluble Starch Synthase IV-2 and It with ADPglucose Pyrophorylase Large Unit and Pullulanase on Rice Qualities

Abstract

Background Rice amylose content and amylopectin structure corporately determine rice eating and cooking qualities (ECQs). Soluble starch synthase ( SS ) IV-2 is a member of the soluble starch synthesis gene family but with unknown effects on ECQs. Results In this study, three populations derived from a cross of two parents who possess the same major genes of starch bio-synthesis were employed to investigate the influence of SSIV-2 and its combined effects with ADPglucose pyrophorylase large unit ( AGPlar ) and Pullulanase ( PUL ) on ECQs. The results illustrated that the polymorphism of SSIV-2 alleles significantly affected gel consistency (GC), gelatinization temperature (GT), percent of retrogradation (PR) and three crucial rapid viscosity analysis (RVA) profile parameters: peak viscosity (PKV), breakdown viscosity (BDV) and setback viscosity (SBV). And SSIV-2 allele derived from CG173R had better quality traits with lower GT, SBV and PR. Moreover, its interaction with AGPlar was responsible for the variations of GC, apparent amylose content (AAC), GT, PR and all RVA parameters except for pasting temperature (PaT) and peak time (PeT), in terms of GC, PKV and CSV, AGPlar derived from CG173R had an epistatic effect on SSIV-2 ; additionally, interaction of SSIV-2 and PUL mainly affected GC, AAC, PKV, CPV, CSV and SBV. I-C and C-1 (I, allele of AGPlar from Guangzhan 63S; C, allele of SSIV-2 from CG173R; 1, allele of PUL from Guangzhan 63S) combinations had better ECQs. Conclusions SSIV-2 alleles significantly affect rice quality, especially the parameters relevant to gelatinized and thermal characteristics of starch (GC, PR, GT, PKV, BDV and SBV) under the same major genes ( Waxy and SSII-3 ) background. It indicates that SSIV-2 functions elongation of starch chain. These findings suggest that the effects of SSIV-2 and its interaction with AGPlar and PUL are vital for rice quality breeding with the same major genes.

Effects of Starch Synthesis-Related Genes Polymorphism on Quality of Glutinous Rice

“…As in earlier studies, we found that SBE1, BEIIb, SSIVb, and PUL affected GC (He et al, 2006;Tian et al, 2009;Xu et al, 2020). Besides, ISA1, SSIIc, BEIIa, and SSIIa were also associated with GC, and their genetic effects decreased in order (Table 4).…”

“…Furthermore, the effects of SSIVb and its interaction with AGPlar and pullulanase (PUL) are vital for rice quality breeding under the background of the same major genes (Xu et al, 2020). Many studies favored understanding the genetic basis of rice qualities by quantitative trait loci (QTLs) mapping (Leng et al, 2014).…”

Post-genomics revolution in the design of premium quality rice in a high-yielding background to meet consumer demands in the 21st century

“…It is noteworthy that mutation of SSIV-2 or SSIIIa had no significant effect on rice starch granule morphology, but their combination resulted in small and spherical starch granules ( Toyosawa et al., 2016 ). Recently, it has been confirmed that the interaction of AGPlar and PUL contributes to rice ECQ ( Xu et al., 2020 ). The mutation of individual SS genes usually leads to undesirable grain quality traits (i.e., SSIII-1 ) and minor changes in ECQ ( Huang et al., 2021a ; Zhu et al., 2021 ).…”

Active-type starch synthase (SS) IIa from indica rice partially complements the sugary-1 phenotype in japonica rice endosperm

“…Therefore, it was concluded that the effects of SSIIa, GBSSI, and ISA1 gave greater influence than the other genes derived from parental japonica and indica lines. The minor differences observed between these two lines may be due to nucleotide polymorphisms found in other genes, such as SSIVb and AGPase, and that may give minor effects on the properties of starch (Xu et al 2020). To eliminate the minor effects of other genes, it is necessary to perform backcrossing to produce near isogenic lines or to perform targeted insertion of transgenes.…”