Morphological and molecular effects of short-term water deficiency in barley stamen maturation

ABSTRACT Water deficiency at the reproductive stage of cereal crops mainly affects the development or function of male organs, which causes strong losses in grain yield. We investigated the effects of short-term drought on the post-meiotic maturation of stamens in barley cultivar Scarlett, where it leads to a stage-dependent decline in fertility. Water deficiency neither affects pollen viability nor the formation of trinuclear pollen. However, it completely blocks pollen starch accumulation. Metabolite profiling suggests that this is due to decreased sugar content at starch-filling stages, probably reflecting impaired carbon supply from photosynthetic tissues to anther sinks. Accordingly, transcriptomic analysis shows that drought reduces the expression of stamen sugar transporters. Moreover, drought causes a strong downregulation of the pollen transcriptional network of auxin signalling and central carbon metabolism genes that controls barley pollen starch production. This wider model of the molecular effects of water deficiency on cereal pollen provides a solid foundation to characterize tolerance mechanisms in potential drought-resistant germplasm.