Epigenomic changes in plant cell cultures by Hyper- & hypo- Methylation and RNA interference
Plant biologists have long known that regenerants from plant cell cultures show heritable changes known as somaclonal variation. This poses a significant challenge towards effective utilization of tissue culture techniques, if the objective is intended to mass-propagate true-to-progeny population. In a research article published in December 2008 issue of PLOS Biology, Milos Tanurdzic et al. (PLoS Biol 6(12): e302) reported epigenomic consequences of long term plant cell cultures. The group investigated the abundance of histone and DNA methylation. Their analyses have revealed that heterochromatin and euchromatin become respectively hypomethylated and hypermethylated. It is already known that hypomethylation of both DNA and histone is associated with transcriptional activation and hypermethylation with silencing. Thus, silent chromosomal region become activated and vice versa. This is similar to what is observed in cancer cells and animal cell culture lines. Their analyses have also revealed that reactivated transposable elements (TE, from heterochromatin) express predominantly 21-nucleotide (nt) long small RNAs (sRNA). On the contrary, in the inactivated portions, TE’s show 24-nt long sRNA expression. This change in predominant sRNA type is suggestive of the role of RNA interference machinery in epigenetic remodelling of plant cell culture. Summarized by Mahdi Moosa, Genetic Engineering & Biotechnology, DU.
