Review of Cell–Cell Communication in Plant Reproduction

Unlike animals, the angiosperm gametes are emerged in the multicellular gametophytes, which are produced from meiotic products through multiple mitotic divisions. The non-motile sperm cell should be delivered to the female gamete via a pollen tube during the process of sexual reproduction. During this journey of the pollen tube to the female gametophyte, a series of events happen, including activation and germination of pollen grains on the stigma, polar tip growth of pollen tubes in the transmitting tract, guidance of pollen tubes to the ovules, perception of pollen tubes by the female gametophyte, and pollen tubes rupture to release the sperm cells for the double fertilization. In general, the tube cell interacts and communicates with more than seven types of tissues/cells; thereby the smooth going of this long journey depends on complex signal exchanges and coordinated communications between male and female tissues/cells in each step. In particular, peptide signals and their corresponding receptor-like kinases are found to play important roles in mediating the male/female communication. In recent years, more and more molecular mechanisms of the male/female interactions have been uncovered and a number of important advances have been made, which will be mainly introduced and discussed in this review.