Plant germline development: a tale of cross-talk, signaling, and cellular interactions

Abstract

Plants have a complex life cycle in which diploid and haploid generations alternate: the diploid sporophyte produces the spores, while the haploid gametophytes form the gametes. In bryophytes and ferns, the dimorphic gametophytes are free-living, but their development has become dependent on the sporophyte in seed plants. This opens a multitude of opportunities for interactions and cross-talk between the two generations, many of which are discussed in this issue of Sexual Plant Reproduction. In angiosperms, gametophytes develop within the reproductive organs of the flower: the male gametophyte (pollen) within the anthers and the female gametophyte (embryo sac) within the ovule, which develops from the placental tissues of the carpel (Ma and Sundaresan 2010). The gametophytes in turn differentiate one pair of gametes each. During double fertilization, which initiates seed development, one sperm fuses with the central cell producing the endosperm, while the second fertilizes the egg to form the embryo and thus the next sporophyte generation. Although Theophrastus of Eresos (371‐287 BC), the ‘Father of Botany’, already recognized the existence of male and female plants (Negbi 1995), it took the offering of a prize by the Imperial Academy of Sciences in St. Peterburg, to experimentally prove that plants reproduce sexually just as animals do. By crossing Nicotiana rustica