"Molecular Dialogues between Pollen and Pistil"

Pollen tubes penetrate the stigma, extend through specialized pistil transmitting tissue, are attracted to ovules and deliver two sperm to the female gametophyte so one can fuse with the egg to form the embryo and the other with the central cell to form endosperm. This process depends on a series of complex cell:cell interactions and is central to seed crop production. These interactions need to be understood in molecular detail if we are to apply biotechnology to improving yields and controlling fertilization. In recent years, genetics, genomics, and cellular imaging have combined to record snippets of the pollen-pistil dialogue, but there is much to be learned. Our analysis of the pollen tube transcriptome has led to identification of a group of transcription factors that control the ability of the pollen tube to reshape its gene expression profile as it grows through the pistil. Genetic analysis identified the hap2(gcs1) mutation that blocks the ability of sperm to fuse with either the egg or the central cell. HAP2(GCS1) is likely at the center of a highly conserved mechanism that mediates gamete fusion and we are using a number of approaches to understand its biochemical function. I will discuss our recent findings in the context of an integrated model of how pollen-pistil interactions have evolved to maximize reproductive fitness.