Genome‐wide association study of the resistant starch content in rice grains

Abstract

The consumption of resistant starch (RS), which can increase satiety and reduce calorie intake, may help ameliorate lifestyle-related diseases such as diabetes, hypertension, and obesity. The identification of genes or quantitative trait loci (QTLs) may facilitate improvement in the amounts and properties of RS in cereals such as rice. A genome-wide association mapping of the RS content in milled rice grain was carried out to identify QTLs in a rice germplasm collection. The RS contents among 105 rice accessions ranged from 0.3 to 2.42%, and the apparent amylose content (AAC) was positively correlated with the RS content (R 2 ¼ 0.75). Four QTLs were detected, and each explained a total phenotypic variation of 10-13%. Two of these, on chromosome 6, were identified at the Waxy gene locus encoding granule-bound starch synthase I and starch synthase IIa. The other two QTLs, on chromosomes 8 and 9, were close to candidate genes encoding the starch debranching enzyme isoamylase I and ADP-glucose pyrophosphorylase small subunit 1, respectively. The results of this study should improve our understanding of the genetic basis of RS in milled rice and may assist plant breeders attempting to develop new rice varieties and food processors working to develop functional foods.

Waxy and Soluble Starch SynthaseII-3 Alleles Regulating Rice Resistant Starch Contents from Different Processing Status

“…SSII-3 plays a vital role in the amylopectin synthesis pathway, and it can control the degree of crystallinity and the amount of short A chains of amylopectin (Kong et al 2015). As reported in previous articles, SSII-3 was found to have an effect on RS content (Bao et al 2017), and the down-regulation of SSII-3 could enhance RS content in barley (Bird et al 2004) and wheat (Yamamori et al 2006). SSII-3 is present in a large complex including ADP-glucose pyrophosphorylase (AGPase), pyruvate orthophosphate dikinase (PPDK), SSIIIa, SBEIIa and SBEIIb, which regulate the partitioning of ADP-glucose (ADPGlc) into lipid or starch and further control RS5 (Zhou et al 2016).…”

“…Raigond et al (2015) found that high amylose could contribute to RS content. Bao et al (2017) utilized the genome-wide association study to select the candidate genes affecting RS and identi ed that Wx was one of the candidate genes, as well as the mean RS content of indica rice was higher than that of the japonica rice. Furthermore, Zhou et al (2016) revealed that RS production was dependent on the high expression of Wx a allele, which is consistence with our conclusion.…”

Phytic acid content may affect starch digestibility and glycemic index value of rice (Oryza sativa L.)

“…GBSSI was highly expressed in the developing grains and the up‐regulation or down‐regulation of this gene may cause alteration of AC in rice grains. A SNP (G/T) at the splice site of intron 1 of GBSSI suggested that GI is negatively correlated with AC . This indicates that the amylose synthesis and accumulation occur during the middle stage of grain filling as expression of GBSSI is substantially increased during this particular stage.…”

Addition of Pulses, Cooking Oils, and Vegetables Enhances Resistant Starch and Lowers the Glycemic Index of Rice (Oryza sativa L.)

“…As RS is not digested, it does not form a source of energy for the consumer. [6] Thus, RS improves the functioning of the digestive tract, microbial colonization, blood cholesterol level, and thus helps to control diabetes. [7] Amylose-rich rice varieties exhibit lower GI values than the low-amylose varieties.…”