Understanding the mechanism of monoADP ribosylation in OsSRT1 and its linkage to DNA repair system under stress conditions

The role of sirtuins in plants are slowly unraveling. There are only reports of H3K9Ac deacetylation by OsSRT1. Here our studies shade light on its dual enzyme capability with preference for mono ADP ribosylation over deacetylation. OsSRT1 can specifically transfer the single ADP ribose group on its substrates in an enzymatic manner. This mono ADPr effect is not well known in plants, more so for deacetylases. The products of this reaction (NAM and ADP ribose) have immense negative effect on this enzyme suggesting a tighter regulation. Resveratrol, a natural plant polyphenol proves to be a strong activator of this enzyme at 150 μM concentration. Under different abiotic stress conditions, we could link this ADP ribosylase activity to the DNA repair pathway by activating the enzyme PARP1. Metal stress in plants also influences these enzyme activities. Highlights OsSRT1 can transfer a single moiety of ADP-ribose on itself as well as other nuclear proteins like histones H3 and H2A. NAM, ADP-ribose and certain metal ions negatively regulate this ADP-ribose transfer. ADPr of OsPARP1 and OsPARP2 links OsSRT1 to DNA damage repair pathways. OsSRT1 positively regulates the activity of OsPARP1 by ADP ribosylating it. On plant’s exposure to H 2 O 2 (oxidative stress) and Arsenic toxicity, there is a link between the increased activity of the players of DNA damage repair system and overexpression of OsSRT1.