Genome-wide study of Protein Arginine Methyltransferases (PRMT) gene family in selected orchid species: the epigenetic architects of orchid genome.

Protein arginine methyltransferases (PRMTs) are an important group of epigenetic regulators that mediate methylation of target proteins at arginine residues. These post-translational histone modifiers play a substantial role in controlling various biological activities of plants by altering the chromatin structure and thus, regulating the gene expression. In the present study, a total of 24 putative PRMT genes were reported in three orchid species, Apostasia shenzhenica (eight AshPRMTs), Dendrobium catenatum (eight DcaPRMTs) and Phalaenopsis equestris (eight PeqPRMTs). Based on the presence of characteristic domains and conserved motifs, the PRMTs could be classified into three distinct types, type I, II and III which was substantiated using multiple sequence alignment. Phylogenetic analysis showed the distinct clustering of PRMTs into three types along with their PRMT counterparts of Arabidopsis thaliana and Oryza sativa. Prediction of secondary and tertiary protein structures as well as gene structures provided further validation of this classification. Furthermore, expression profiling across different vegetative and reproductive tissues and analysis of cis-regulatory promoter elements suggested their plausible roles in various growth and development related processes. Since PRMT gene family constitutes an important class of histone-modifying enzymes playing a pivotal role in many morphological processes, this study would be an important base for functional validation of their role in important biological phenomenon in orchids.