Figure 2.

Male gametogenesis in Arabidopsis thaliana, Marchantia polymorpha, and mammals. (A) In A. thaliana, microspores generated from meiosis of pollen mother cells undergo asymmetrical cell division to form vegetative and generative cells. Each generative cell divides symmetrically to yield two immotile sperm cells. Once pollen grains are attached to the surface of stigmas, they germinate to produce pollen tubes, which transport male gametes to female gametes. This figure is illustrated based on figures in Berger and Twell (2011) and Hackenberg and Twell (2019). (B) In M. polymorpha, spermatids are formed by the diagonal cell division of spermatid mother cells. Spermatids undergo a dynamic morphogenetic transformation called spermiogenesis to form spermatozoids. This figure was illustrated based on a figure in Shimamura (2016). (C) Dynamic cellular reorganization also takes place during mammalian spermiogenesis. Just before the release of spermatozoa, unnecessary cytoplasmic components are excluded from their cell bodies as the residual body, which is phagocytosed and degraded by the neiboring Sertoli cell.