Transcriptome profiling of wheat genotypes under heat stress during grain-filling

Abstract

High temperatures adversely impact productivity and quality (nutritional and functional) of wheat grains. Anthesis and post-anthesis developmental stages are more sensitive to heat stress, with the grain-filling stage being crucial for sustained grain yield and quality. Comparative transcriptome profiling of the developing grain of three wheat genotypes (contrasting for heat stress tolerance) during early- (14-dpa (days post anthesis)) and late-grain filling (30-dpa) was studied to identify key genes involved in imparting heat tolerance. Heat stress during grain-filling (early- and late-) significantly down-regulated key genes in the genotypes, Gregory and Banks, found to be more heat susceptible. Upregulation of the cluster of genes comprising 6-phosphogluconate dehydrogenase, S6 RPS6-2 ribosomal protein, peptidylprolyl isomerase, plasma membrane proton ATPase, Heat shock cognate-70, FtsH protease, RuBisCO activase B, methionine synthase, cytochrome C (class I), and HMW-glutenin in the genotype Fang-60 during heat stress was found to be associated with heat stress tolerance in this genotype. Upregulation of β-glucanase (1,3 & 1,4), triose phosphate isomerase and calnexin at 14-dpa; and downregulation of Na+/H+antiporter, glucose-1-phosphate adenylyltransferase, ips1 riboregulator and AraC family transcriptional regulator at 30-dpa was observed specifically in the heat susceptible genotypes. Hsp-family, ascorbate peroxidase, β-amylase, γ-gliadin-2 and LMW-glutenin were heat stress responsive and were upregulated during stress across 14- and 30-dpa in all three genotypes. This study provides insights into genes that may be involved in regulating heat tolerance in a tolerant genotype and those that are responsive to heat in the developing wheat grain of tolerant and susceptible genotypes. The genotype Fang-60 was demonstrated to be a potential source of heat stress tolerance for use in wheat breeding.