Drought Priming at Vegetative Growth Stages Enhances Tolerance to Drought Stress during Grain Filling in Wheat.

Wheat is one of the major crops grown throughout the world with a primary use in human nutrition. Anticipated changes in global climatic variability leading to more frequent extreme conditions will require adaptations of crop species on an unprecedented magnitude in order to sustain agricultural production. Drought stress is one of the most severe abiotic stress forms, constraining both plant growth and productivity. The response of plants to stress involves both short-term molecular and physiological responses as well as long-term structural and morphological modifications. Little is known on the impact of the increased frequency of extreme climate events and the implications of environmental variability on quality parameters in wheat. In order to investigate the effect and mechanisms of drought acclimation, wheat plants were subjected to single or multiple mild drought episodes before anthesis and/or to a severe drought stress event at 15 days after anthesis. The responses of the physiological (photosynthesis rate, activities of antioxidant enzymes and abscisic acid content) and proteomic parameters (protein expression in leaves) were analyzed and identified. Here, The single or multiple drought priming events before anthesis resulted in higher grain yield under drought stress during grain filling. The primed plants showed higher leaf water status, higher photosynthesis rates, higher ascorbate peroxidase activity and lower cell membrane peroxidation than did the non-primed plants. Furthermore, the protein abundances of Rubisco small subunit, Rubisco activase and ascorbate peroxidase were up regulated in primed plants compared to non-primed plants. Both the up-regulated synthesis (expressed as protein abundance) and activities of proteins involved in photosynthesis and stress defence in primed plants could be contributing to the priming effects enabling the plants to cope with the drought stress during grain filling.