Involvement of 5mC DNA demethylation via 5-aza-2'-deoxycytidine in regulating gene expression during early somatic embryo development in white spruce (Picea glauca).

DNA methylation plays a crucial role in the development of somatic embryos (SEs) through the regulation of gene expression. To examine the impact of DNA methylation on gene expression during early SE development in Picea glauca, the demethylation reagent 5-aza-dC (5-aza-2'-deoxycytidine) was employed to modify DNA methylation regions and levels during the pre-maturation stage of somatic embryogenesis. The application of 2.0 µM 5-aza-dC did not induce toxicity to SEs in early development. Following treatment, the global DNA methylation level decreased significantly on the 7^th day of pre-maturation and the 1^st week of maturation. Methylated DNA immunoprecipitation (MeDIP) sequencing revealed that differentially methylated regions, as analyzed through Gene Ontology (GO), were related to plant development and reproduction and that they were hypomethylated on the 3^rd day but hypermethylated on the 7^th day in 5-aza-dC-treated embryogenic tissues. These findings indicate that 5-aza-dC treatment positively impacts early SE development, which was inhibited following 7 d of treatment. The expression of MSH7, JMJ14, and CalS10 was associated with DNA methylation, epigenetic regulation, and somatic embryogenesis. Further analysis of methylated regions revealed that the expression profiles of MSH7, JMJ14, and CalS10 were correlated with altered DNA methylation, suggesting DNA methylation at 5 mC may play a role in controlling the expression of these genes and regulating the early development of SEs in P. glauca. This study offers new insights into the regulation of somatic embryogenesis in conifers.