Abstract
We have reported previously that transgenic Arabisopsisplants expressing ADP-ribose/NADH pyrophosphatase (AtNUDX2) had increased tolerance of oxidative stress. Here we studied in detail the relationship between activities of ADP-ribose/NADH pyrophosphatase (AtNUDX2, 6, 7) and tolerance of oxidative stress. The AtNUDX2-overexpressing plants suppressed the accumulation of free ADP-ribose under oxidative stress caused by 3 μM paraquat treatment. The levels of NADH in the AtNUDX7-overexpressing and knockout plants were considerably low and high, respectively, under normal conditions. High levels of NADH were also observed in the AtNUDX6-knockout plants. Interestingly, the activities of poly (ADP-ribosyl)ation (PAR) in the AtNUDX7-overexpressing and the knockout plants were clearly enhanced and suppressed, respectively, under normal conditions. These results indicate that the AtNUDX2 protein plays an important role in the removal of free ADP-ribose, and AtNUDX6 and 7 proteins function in the activation of PAR via hydrolyzation of NADH, resulting in increased tolerance of oxidative stress.
