Starch and Sugar Metabolism Response to Post-Anthesis Drought Stress During Critical Periods of Elite Wheat (Triticum aestivum L.) Endosperm Development

Wheat is very sensitive to drought stress, especially during the grain filling stage. The aim of this study was to investigate the response of starch and sugar metabolism to drought stress during the critical period of wheat grain filling. In this study, Logistic regression analysis was used to simulate the grain filling rate of two elite wheat varieties under two water treatments. It was found that the early period of grain-filling was mostly affected by drought stress through testing the sucrose and soluble sugar contents, sucrose synthase activity, starch content and its fractions, and the activity of key starch synthases of endosperm under two water treatments at 7 and 14 DPA (days post anthesis). Meanwhile, the differential expressed proteins (DEPs) of endosperm between two water treatments were identified by the isobaric tags for relative and absolute quantification (iTRAQ) quantitative proteomics technology. The results showed that the soluble sugar contents and sucrose synthase (SS) activity in the endosperm of both cultivars were significantly increased under drought stress. Under drought treatment, the sucrose content and total starch firstly decreased and then increased compared with their respective controls. The variety (Xindong 18) with strong drought resistance was conducive to the accumulation of amylose during early grain development. KEGG pathway analysis revealed that most of the DEPs were involved in carbohydrate metabolism, while the largest proportion of DEPs involved in carbohydrate metabolism was related to the metabolism of starch and sugar. Importantly, the expression levels of DEPs involved in starch biosynthesis and degradation were upregulated in response to drought stress. Drought stress during the early stage of grain-filling stimulated wheat to shift the focus of life activities to energy and material accumulation, which improves the organismal ability to resist drought. This study provides novel insights on the mechanisms of starch and sugar metabolism regulate drought tolerance in wheat during early endosperm development.