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Cytology at meiotic prophase I in pollen mother cells (PMCs) of the euploid wheat and its 21 nullisomic lines were investigated. The results revealed that all of the investigated materials had cytomixis between their PMCs, and in most lines the PMCs within a loculus of an anther developed synchronously, but asynchrony was observed in five nullisomic lines of 5A, 5B, 2D, 4D and 5D, suggesting that genes controlling meiotic synchrony among PMCs were localized on these chromosomes. Meiotic asynchrony could occur even between two neighboring pollen mother cells (PMCs) undergoing cytomixis, suggesting that cytomictic channels (CCs) alone could not sufficiently render the occurrence of this prominent phenomenon, and that some other factors must be involved in this process.

Epigenetic marks in the form of DNA methylation are involved in the development of germ cells and are important in the maintenance of fertility. However, the controlling system of the on-off switch for DNA methylation largely remains unclear. In this study, the extent of cytosine methylation during the meiotic prophase I in David lily is assessed using high pressure liquid chromatography to evaluate the DNA methylation rates. Comparing the degree of DNA methylation before, during, and after synizesis, both de novo methylation and demethylation occurred. Mainly the methylation level decreased by 21.3% (from 54.8 to 33.5%) during synizesis in the pollen mother cells. The developmental timing of genome-wide DNA methylation acquisition during pollen mother cell development is clarified in this paper. The relative amounts of 5-methyl-deoxycytidine of global methylation in leaf DNA in David lily were also higher than in other species reported.