Expression Analysis On DNA Methyltransferase Genes And DNA Methylation In Pollen Mother Cells

Epigenetic marks in the form of DNA methylation are involved in the regulation of genome function. However, the controlling system of the on-off switch for DNA methylation largely remains unclear. According to the fusion vector of Arabidopsis DNA methyltransferase gene's promoter and GUS, we studied the expression patterns of genes in space and time. We found that the expression of METâ…¡a and DRM2 decreased accompanying with the development of hypocotyl and root, respectively. Furthermore, DRM2, MET1, CMT3 and DNMT2L were activated at different developmental stages with different amount of GUS signal. In the same organ, we also detected the expression of more than one DNA methyltransferase genes. For example, there were eight genes activated in stigma, leaf and cotyledon. MET1, CMT3 and DRM2 showed strong GUS signals in apical point. Among those genes, only MET1 expressed in root hairs and embryo. CMT1 and METIII specially expressed in micropyle and ovule stalk. These results suggest that these genes are of importance in the formation of Arabidopsis development. The different gene families (MET/CMT/DRM) have the similar expression but not identical and genes from the same family have the simiar expression but different GUS signal, suggesting the genes have redundant function. Together, the DNA methyltransferase genes probably participated in the whole development and the formation of organs. At the same time, the area and capacity of expression are distinct among the genes. It suggests that the function of methyltransferases is overlapping, but also different.In order to characterise the variety of cytosine methylation during meiotic prophase I, we used the high pressure liquid chromatography to evaluate the DNA methylation rates in David lily (Lilium davidii vav. Willmottiae (Wilson) Roffill). By comparing the extent of DNA methlation in pollen mother cells (PMCs) before, during and after synizesis, we found that the degree of DNA methylation during synizesis was lowest,33.5%, while before and after synizesis were about 54.8%. The increase and decrease was up to 21.3%. It suggests that the DNA in PMCs underwent demethylation and de novo methylation. Our results suggest that the extend of genome-wide DNA methylation changes accompanying with development.