Male Gametophyte Development and Function

Male gametophyte development in higher plants is a complex process that requires the coordinated participation of various cell and tissue types and their associated specific gene expression patterns. The male gametophytic life cycle can be divided into a developmental phase leading to the formation of mature pollen grains, and a functional or progamic phase, beginning with the impact of the grains on the stigma surface and ending at double fertilisation. Pollen ontogeny is also an excellent model in which to dissect the cellular networks that control cell growth, polarity, cellular differentiation and cell signaling. Here we present an overview of important cellular processes in male gametophyte development and recent advances in genetics and genomic approaches that are advancing the field significantly. Genetic approaches have identified a growing number of gametophytic mutants affecting discrete steps during the developmental or progamic phases that are now beginning to uncover some of the key molecular processes involved. With recent technological advances pollen transcriptomic studies now provide the first genome-wide view of male reproductive cell development in Arabidopsis These studies reveal at least two successive global gene expression programs and the identity of a large number of male gametophyte-specific genes and putative transcriptional regulators. Transcriptome analysis has revealed a striking overrepresentation of cell wall metabolism, cytoskeleton and signaling genes in preparation for the progamic phase. This quantum leap in gene-centered knowledge highlights the functional specialization of this pathway and offers many new opportunities for the dissection of cellular processes that control male reproductive success.