Meiosis is a special cell division that halves the chromosome number in preparation for fertilization. In this process, the genomic information of the parents is shuffled to generate a new gene combination (meiotic recombination), which is inherited to the next generation. The meiotic recombination machinery is widely conserved in eukaryotes and has been extensively studied. On the other hand, the mechanisms by which germ cells transition to meiosis are diverse among species, and little is known particularly in plants.

In this review, we mainly focused on meiosis of flowering plants, and explained how the archesporial cells, which produce meiocytes in the future, develop and eventually achieve meiosis with the latest findings. We also highlight the findings of our research group that the callose polysaccharide, a special plant cell wall components, plays an essential role in regulating the proper initiation timing and progression of male meiosis.

The image using the figures in our review paper was selected for the cover story of Plants Vol. 12, No. 10, including 143 articles.

Figure: A model of callose synthesis and transport in anthers
(A) Cross sections of the anther just before meiosis. (Upper) Staining of cellulosic cell walls. (Bottom) Double immuno-staining of callose (red) and GSL5 (yellow). Bar=20µm. (B) The plasma membrane-anchored callose synthase (GSL) of male meiotic cells (PMCs) releases synthesized callose to apoplasts between PMCs (APOPLAST) just prior to meiosis transition. Callose migrates to the apoplast between PMCs and tapetum cells (TAPETUM) where GSL is absent, and eventually envelop all PMCs within the anther locule.