Arabidopsis T‐DNA mutants affected in TRDMT1/DNMT2 show differential protein synthesis and compromised stress tolerance

TRDMT1/DNMT2 belongs to the conserved family of nucleic acid methyltransferases. Unlike the animal systems, studies on TRDMT1/DNMT2 in land plants have been limited. We show that TRDMT1/DNMT2 is strongly conserved in the green lineage. Studies in mosses have previously shown that TRDMT1/DNMT2 plays a crucial role in modulating molecular networks involved in stress perception and signalling and in transcription/stability of specific tRNAs under stress. To gain deeper insight into its biological roles in a flowering plant, we examined more closely the previously reported Arabidopsis SALK_136635C line deficient in TRDMT1/DNMT2 function [Goll MG et al. (2006) Science 311, 395–398]. RNAs derived from Arabidopsis Dnmt2‐deficient plants lacked m⁵C38 in tRNA^Asp. In this study, by transient expression assays we show that Arabidopsis TRDMT1/DNMT2 is distributed in the nucleus, cytoplasm and RNA‐processing bodies, suggesting a role for TRDMT1/DNMT2 in RNA metabolic processes possibly by shuttling between cellular compartments. Bright‐field and high‐resolution SEM and qPCR analysis reveal roles of TRDMT1/DNMT2 in proper growth and developmental progression. Quantitative proteome analysis by LC–MS/MS coupled with qPCR shows AtTRDMT1/AtDNMT2 function to be crucial for protein synthesis and cellular homeostasis via housekeeping roles and proteins with poly‐Asp stretches and RNA pol II activity on selected genes are affected in attrdmt1/atdnmt2. This shift in metabolic pathways primes the mutant plants to become increasingly sensitive to oxidative and osmotic stress. Taken together, our study sheds light on the mechanistic role of TRDMT1/DNMT2 in a flowering plant.