Abstract
We isolated a paraquat-resistant mutant (pqr-216) from Arabidopsis activation-tagged lines and found that the tolerance to oxidative stress was responsible for overexpression of a MutT-like protein (AtMutT1). Among eleven types of cytosolic MutT-like protein homologues (AtMutT1-11) in Arabidopsis, we found that AtMutT1 hydrolyses ADP-ribose and AtMutT8 hydrolyses 8-oxo-dGTP. Here we explored the molecular properties of cytosolic MutT-like proteins. Using His-tagged recombinant proteins of AtMutTs, we analyzed substrate specificities to various types of nucleoside diphosphate derivatives and deoxyribonucleoside triphosphates. The recombinant proteins of AtMutT5 and AtMutT6 also showed the ability to hydrolyse ADP-ribose, like AtMutT1. The transcript levels of AtMutT1, 5, and 6 were increased by various stress conditions, such as high light, paraquat treatment, drought, and salinity. These results suggest that MutT-like proteins in Arabidopsis are associated with the maintenance of level of ADP-ribose in the cells under stress conditions.
