Pollen Germination and Tube Growth

Abstract

Abstract Seeds and grains are staple food supply around the world and their production is the result of successful double fertilization of female gametophytes by male gametophytes. In flowering plants, the highly reduced haploid male gametophyte (pollen grain) plays a critical role in fertilization and crop production through the generation of a pollen tube that delivers the male gametes (two sperm cells) to the egg and central cells within the female gametophyte (embryo sac) for double fertilization. Double fertilization and the functional specialization of the male gametophyte are two key innovations behind the evolutionary success of angiosperms. Pollen tube elongation involves typical polar cell growth and provides a marvelous system to study the fundamental events of morphogenesis, cellular compartmentation and signalling networks in establishing and maintaining cellular identities. Furthermore, pollen germination on the stigmatic papilla cell surface and pollen tube elongation in the style offer an exceptional system to study the molecular and cellular mechanisms involved in cell-to-cell communication and signalling. Here, we summarize current knowledge and important discoveries of genes/proteins and mechanisms essential for pollen germination, pollen tube elongation and guidance in the style that highlight new insights into the elements regulating the complex interaction between these two partners during fertilization. In addition, during the past decade, study of plant biology has been enhanced by the development of advanced instruments and valuable data: highly annotated genomes, comprehensive genetic and transcriptomic resources, readily available T-DNA insertional mutants and revolutionary microscope and imaging systems. The simultaneous availability of these tremendous resources and tools opens a new era to conduct genome-wide and systematic investigation of the molecular and cellular mechanisms governing pollen germination and tube elongation.