Genome-Wide Association Mapping of Mixed Linkage (1,3;1,4)-β-Glucan and Starch Contents in Rice Whole Grain.

Rahele Panahabadi,Asadollah Ahmadikhah,Naser Farrokhi,Pär K Ingvarsson,Lauren S Mckee

doi:10.3389/fpls.2021.665745

Abstract

The glucan content of rice is a key factor defining its nutritional and economic value. Starch and its derivatives have many industrial applications such as in fuel and material production. Non-starch glucans such as (1,3;1,4)-β-D-glucan (mixed-linkage β-glucan, MLG) have many benefits in human health, including lowering cholesterol, boosting the immune system, and modulating the gut microbiome. In this study, the genetic variability of MLG and starch contents were analyzed in rice (Oryza sativa L.) whole grain, by performing a new quantitative analysis of the polysaccharide content of rice grains. The 197 rice accessions investigated had an average MLG content of 252 μg/mg, which was negatively correlated with the grain starch content. A new genome-wide association study revealed seven significant quantitative trait loci (QTLs) associated with the MLG content and two QTLs associated with the starch content in rice whole grain. Novel genes associated with the MLG content were a hexose transporter and anthocyanidin 5,3-O-glucosyltransferase. Also, the novel gene associated with the starch content was a nodulin-like domain. The data pave the way for a better understanding of the genes involved in determining both MLG and starch contents in rice grains and should facilitate future plant breeding programs.

Highlights

Rice (Oryza sativa L.) improvement for increased nutritional value is a crucial objective in the breeding programs
Extensive analyses of carbohydrate contents of rice grains found a negative correlation between the amount of MLG and starch; a high starch content is matched in rice grains with a low MLG content and vice versa (Supplementary Figure 2)
The MLG and starch contents of rice whole grains were measured in a large portfolio of rice accessions

Summary

Introduction

Rice (Oryza sativa L.) improvement for increased nutritional value is a crucial objective in the breeding programs. Much of the nutritious value of the rice grain derives from carbohydrates found in the plant cell wall and those used for energy storage within the grain. Plant cell walls are composites of polymer chains mainly derived from monosaccharides and phenolic compounds, with cellulose and lignin acting as the strong fibrous components surrounded by more amorphous matrix polysaccharides. The latter are often referred to as hemicelluloses and include glucuronoarabinoxylans (GAXs), arabinoxylans (AXs), mixed linkage (1,3;1,4)-β-Dglucans (MLGs), xyloglucans (XyGs), and galactoglucomannans (GGMs). The hemicelluloses may be embedded in a gel of pectic polysaccharides, depending on the plant species (Burton et al, 2010).

Methods

Results

Discussion

Conclusion