Starch Metabolism in Wheat: Gene Variation and Association Analysis Reveal Additive Effects on Kernel Weight.

Jian Hou,Tian Li,Yunchuan Liu,Xueyong Zhang,Chenyang Hao,Hongxia Liu

doi:10.3389/fpls.2020.562008

Abstract

Kernel weight is a key determinant of yield in wheat (Triticum aestivum L.). Starch consists of amylose and amylopectin and is the major constituent of mature grain. Therefore, starch metabolism in the endosperm during grain filling can influence kernel weight. In this study, we sequenced 87 genes involved in starch metabolism from 300 wheat accessions and detected 8,141 polymorphic sites. We also characterized yield-related traits across different years in these accessions. Although the starch contents fluctuated, thousand kernel weight (TKW) showed little variation. Polymorphisms in six genes were significantly associated with TKW. These genes were located on chromosomes 2A, 2B, 4A, and 7A; none were associated with starch content or amylose content. Variations of 15 genes on chromosomes 1A and 7A formed haplotype blocks in 26 accessions. Notably, accessions with higher TKWs had more of the favorable haplotypes. We thus conclude that these haplotypes contribute additive effects to TKW.

Highlights

Wheat (Triticum aestivum L.) yield depends on three main components: spike number per area, grain number per spike, and thousand kernel weight (TKW)
Amylose in the grain is mainly synthesized by GBSSI, and mutations in GBSSI can reduce amylose contents in rice (Oryza sativa L.), maize, barley (Hordeum vulgare L.), and wheat (Tsai, 1974; Sano, 1984; Nakamura et al, 1995; Patron et al, 2002; Perez et al, 2019)
We identified over 8,000 variants in 300 wheat accessions and tested them for association with thousand kernel weight (TKW), starch content (SC), and amylose content (AC), to identify useful polymorphisms among the natural populations

Summary

Introduction

Wheat (Triticum aestivum L.) yield depends on three main components: spike number per area, grain number per spike, and thousand kernel weight (TKW). SUS is a key enzyme in the starch and sucrose synthesis pathway, and its overexpression can increase starch content in potato (Solanum tuberosum L.) and maize (Zea mays L.) (BarojaFernández et al, 2009; Li et al, 2013). Amylose in the grain is mainly synthesized by GBSSI, and mutations in GBSSI can reduce amylose contents in rice (Oryza sativa L.), maize, barley (Hordeum vulgare L.), and wheat (Tsai, 1974; Sano, 1984; Nakamura et al, 1995; Patron et al, 2002; Perez et al, 2019). Overexpression of plastidic AATP in potato can increase the accumulation of ADP-glucose and increase starch content by 16% to 36% compared with WT (Tjaden et al, 1998; Geigenberger et al, 2001). Altering starch metabolism genes represents a promising approach by which to alter wheat grain components

Methods

Results

Conclusion