Physcomitrella patens DNA methyltransferase 2 is required for recovery from salt and osmotic stress

• Published in: The FEBS journal 2016-02, Vol.283 (3), p.556-570
• Main Authors: Arya, Deepshikha, Kapoor, Sanjay, Kapoor, Meenu
• Format: Article
• Language: English
• Subjects: abiotic stress; Amino Acid Sequence; biogenesis; Bryopsida - drug effects; Bryopsida - enzymology; Bryopsida - growth & development; culture media; cytosine; Deoxyribonucleic acid; DNA; DNA (Cytosine-5-)-Methyltransferases - genetics; DNA (Cytosine-5-)-Methyltransferases - metabolism; DNMT2; gene targeting; genes; heat shock proteins; Mannitol - pharmacology; methyltransferase; methyltransferases; Molecular Sequence Data; moss; mutants; Mutation; Osmosis; Osmotic Pressure - drug effects; osmotic stress; Phylogeny; Physcomitrella patens; salt tolerance; Sequence Alignment; Sodium Chloride - pharmacology; stress tolerance; substrate specificity; transfer DNA; Transfer RNA
• ISSN: 1742-464X; 1742-4658
• DOI: 10.1111/febs.13611

DNA methyltransferase 2 (DNMT2) unlike other members of the cytosine DNA methyltransferase gene family has dual substrate specificity and it methylates cytosines in both the DNA and transfer RNA (tRNA). Its role in plants, however, has remained obscure to date. In this study, we demonstrate that DNMT2 from Physcomitrella patens accumulates in a temporal manner under salt and osmotic stress showing maximum accumulation during recovery, i.e. 24 h after plants are transferred to normal growth medium. Therefore, to study its role in stress tolerance, we generated PpDNMT2 targeted knockout plants (ppdnmt2ko). Mutant plants show increased sensitivity to salt and osmotic stress and are unable to recover even after 21 days of growth on optimal growth media. ppdnmt2ko, however, accumulate normal levels of dehydrin‐like and small heat shock protein encoding transcripts under stress but show dramatic reduction in levels of tRNAᴬ ˢᵖ‐ ᴳᵁC. The levels of tRNAᴬ ˢᵖ‐ ᴳᵁC, in contrast, increase ~ 25–30‐fold in ppdnmt2ko under non‐stress conditions and > 1200‐fold in wild‐type plants under stress. The role of PpDNMT2 in modulating biogenesis/stability of tRNAᴬ ˢᵖ‐ ᴳᵁC under salt and osmotic stress is discussed in the light of these observations.