Flower development under drought stress: morphological and transcriptomic analyses reveal acute responses and long-term acclimation in Arabidopsis.

Drought dramatically affects plant growth and crop yield, but previous studies primarily examined responses to drought during vegetative development. Here, to study responses to drought during reproductive development, we grew Arabidopsis thaliana plants with limited water, under conditions that allowed the plants to initiate and complete reproduction. Drought treatment from just after the onset of flowering to seed maturation caused an early arrest of floral development and sterility. After acclimation, plants showed reduced fertility that persisted throughout reproductive development. Floral defects included abnormal anther development, lower pollen viability, reduced filament elongation, ovule abortion, and failure of flowers to open. Drought also caused differential expression of 4153 genes, including flowering time genes flowering locus t, suppressor of overexpression of CO1, and leafy, genes regulating anther and pistil development, and stress-related transcription factors. Mutant phenotypes of hypersensitivity to drought and fewer differentially expressed genes suggest that dehydration response element B1A may have an important function in drought response in flowers. A more severe filament elongation defect under drought in myb21 plants demonstrated that appropriate stamen development requires MYB domain protein 21 under drought conditions. Our study reveals a regulatory cascade in reproductive responses and acclimation under drought.