Dynamics of heat stress response in wheat

Abstract

Recent soaring climates imposing heat stress during the wheat growing season cause frequent losses in grain yield and quality. The study aimed to observe the heat stress responses in wheat during different developmental stages. Heat stress during the seedling stage caused a reduction in the shoot, and root length and relative water content and an increase in antioxidant enzymes and antioxidants except for proline. Significant variations were observed among the genotypes studied. Night-time heat stress during the grain-filling period caused a reduction in plant height, grain yield/spike but no significance was observed for TKW. Under field conditions, variable level of responses among genotypes under different conditions was observed. The effect caused by heat treatment is much higher than late sowing viz., Yield, TKW, grain diameter. SEM analysis showed the amount of B and Ctype granules were reduced. Heat stress under controlled conditions causes early expression of the genes related to starch biosynthesis pathway, starch transporters, transcription factors, stress response and storage protein synthesis. The protein profiles also showed an upregulation of low molecular weight proteins and down-regulation of high molecular weight proteins. The continuous heat stress caused early senescence and maturation of the plant because of a reduction in gene expression related to antioxidant, defence, cell division and biosynthetic machinery. The reduction in gene expression occurred because of an interplay of multiple pathways that led to a reduction in photosynthesis, glycolysis, metabolite biosynthesis, and improper protein folding. Overall, defence response to the heat stress caused early gene expression by activating multiple pathways, which ultimately led to the reduction in grain filling duration, grain weight, yield and processing quality. newline