Role of DNA methylation in growth and differentiation in Physcomitrella patens and characterization of cytosine DNA methyltransferases

Abstract

Epigenetic mechanisms such as DNA methylation are known to regulate important developmental processes in higher eukaryotes. However, little is known about the necessity and role of this process in early land plants. Using the methyltransferase (MTase) inhibitor zebularine (1-(β-d-ribofuranosyl)-1,2- dihydropyrimidine-2-one), the impact of loss of genome-wide methylation on the overall development in Physcomitrella patens was analyzed. It is observed that various aspects of growth and differentiation during gametophyte development become aberrant. A search for the core molecular components of methylation machinery, cytosine DNA MTases, revealed the presence of seven loci in the P. patens genome. Five of the loci code for MTases that are similar to corresponding proteins in higher plants, while two MTases appear specific to P. patens and are closely related to human DNMT3a and DNMT3b, respectively. These proteins possess all the conserved catalytic motifs characteristic of MTases and a domain of unknown function, DUF3444. Association of these highly conserved motifs with a DUF has not been reported in any of the MTases known so far. All the seven genes are differentially but ubiquitously expressed in gametophytes at low levels. Subcellular localization of GFP-fused proteins shows patterns of distribution that can be correlated with their putative cellular functions. This work bridges the knowledge of MTases in P. patens and makes this simple model plant accessible for studies on epigenetic aspects that remain intractable in higher plants. The role of DNA methylation on various aspects of development in Physcomitrella patens has been analyzed. A genome-wide search reveals seven cytosine DNA methyltransferases, five of which are well conserved, while two are specific to P. patens. All seven genes are differentially and ubiquitously expressed. Sub-cellular localization patterns of GFP-fused proteins have been analyzed. This work provides knowledge of methyltransferases in P. patens, one of the simplest land plants. © 2012 The Authors Journal compilation © 2012 FEBS.