Ectopic Expression of the Human MutT-Type Nudix Hydrolase, hMTH1, Confers Enhanced Tolerance to Oxidative Stress in Arabidopsis

Abstract

Oxidized nucleotides produced by oxidative stress cause DNA mutations and the production of abnormal proteins. Thus, mammalian cells have developed multiple MutT-type Nudix hydrolases that exhibit pyrophosphohydrolase activity toward oxidized nucleotides in the cytosol, mitochondria and nucleus. On the other hand, AtNUDX1 is the only MutTtype Nudix hydrolase in the cytosol of Arabidopsis plants.To clarify the physiological significance of the defenses against oxidatively induced DNA damage in plant organelles, we analyzed the effects of the ectopic expression of the human MutT-type Nudix hydrolase, hMTH1, which was localized in the cytosol (cyt-hMTH1), chloroplasts (chlhMTH1) and mitochondria (mit-hMTH1) of Arabidopsis cells, on tolerance to oxidative stress. Tolerance to oxidative stress caused by heating and paraquat (PQ) treatment was higher in the mit-hMTH1 and chl-hMTH1 plants than in the control and cyt-hMTH1 plants. The accumulation of H 2 O 2 and the frequency of dead cells were lower in the mithMTH1 and chl-hMTH1 plants under stressful conditions. The poly(ADP-ribosyl)ation (PAR) reaction, which regulates repair systems for damaged DNA, was activated in the mithMTH1 and chl-hMTH1 plants under heat stress and PQ treatment. Furthermore, DNA fragmentation, which caused programmed cell death, was clearly suppressed in the mit-hMTH1 and chl-hMTH1 plants under heat stress. These results demonstrated that the ectopic expression of hMTH1 in the chloroplasts and mitochondria of Arabidopsis enhanced oxidative stress tolerance by activating the PAR reaction and suppressing programmed cell death.

Pst DC3000 infection alleviates subsequent freezing and heat injury to host plants via a salicylic acid‐dependent pathway in Arabidopsis

“…Trypan blue staining was performed as described by Yoshimura, Ogawa, Tsujimura, Ishikawa, and Shigeoka (), and the fifth leaf was used for staining. The stained leaves were photographed using ZEISS Axio Scope 5 (PlanApo S 1.0 × FWD60 mm; Germany) with SPOT 5.1 imaging software, and nonviable cell portion was quantified by detecting coloration area of trypan blue staining using the software ImageJ (Hartig, ).…”