Effects of high temperature on starch morphology and the expression of genes related to starch biosynthesis and degradation

- Visual signs of pitting on the granule surface induced by high temperature.
- An increase in the A-type granule of the starch under high temperature stress.
- Increased susceptibility of the starch to proteolytic enzymes under high temperature.
- Increase of grain α-amylase activity under high temperature stress.
- Differential alteration of gene transcripts under high temperature stress.

High temperature occurs frequently during grain filling in wheat (Triticum aestivum L.). The objective of this study was to investigate the high-temperature post anthesis effect on the starch granule morphology and gene transcripts that are involved in starch biosynthesis and degradation. Wheat plants were grown under day/night temperatures of 24/17 °C (control) and 37/28 °C (high temperature) from 5 days post anthesis until kernel dry matter accumulation ceased. Upon exposure to high temperature, the matured kernels underwent significant shrinkage, and signs of pitting on the granule surface were more pronounced. The high temperature altered the timing of the starch biosynthetic process and resulted in an earlier peak in the gene expression during starch biosynthesis. The high temperature had a distinct effect on the enhancement of the grain α-amylase activity during kernel filling, and the starch granules were susceptible to enzymatic hydrolysis. This result supported the hypothesis that increased pitting of the granule surface is related to an enhanced α-amylase activity in wheat kernels that are exposed to high temperature post anthesis.