Genetic and epigenetic regulation of meiotic fate decision and gametophyte specification in rice

Abstract

The life cycle of sexual organisms is achieved through repeated rounds of fertilization and meiosis. After premeiotic DNA replication, plant meiosis produces four haploid spores by two sequential cell divisions without DNA replication. In most model organisms, including rice, the homologous chromosome pair is separated to opposite poles during meiosis I, and sister chromatids are separated during meiosis II. In animals, meiotic products directly mature into gametes, namely, sperms and eggs. In contrast, meiosis of land plants produces spores that undergo further somatic cell division and eventually form a multicellular haploid body containing sperms or eggs. In other words, land plants have two distinct multicellular bodies, sporophytic diploid and gametophytic haploid bodies. This type of reproductive mode is called alternation of generations and is commonly found in all land plants, some algae and fungi (Graham, Am Sci 73:178-186, 1985). These facts imply that plants have evolved unique genetic systems for reproduction, in addition to systems common to non-plant species. In this chapter, we overview the genetic and epigenetic systems regulating meiosis and gametogenesis and introduce challenges to improve the efficiency of breeding methods in rice (Oryza sativa L.).