Nitrate reductase-dependent nitric oxide production is involved in aluminum tolerance in red kidney bean roots

The role of nitric oxide (NO) in response to aluminum (Al) stress in red kidney bean (Phaseolus vulgaris) roots was investigated. The results showed that exposure of red kidney bean to Al for 24 h led to the inhibition of root elongation and the enhancement of Al accumulation in root apexes, and such effects were alleviated by NO donor sodium nitroprusside (SNP). The above ameliorating effect of SNP could be reversed by NO scavenger. Furthermore, NO scavenger and nitrate reductase (NR) inhibitors had a similar inhibitory effect on root elongation under Al stress, but NO synthase (NOS) inhibitors had little effect on root elongation. Moreover, Al induced NO production and NR activity. The NO production was markedly reduced by NR inhibitors, but not affected by NOS inhibitors in the presence or absence of Al. Al-induced lipid peroxidation and reactive oxygen species were significantly reduced by SNP but enhanced by NO scavenger. The increased activities of all antioxidant enzymes under Al stress were inhibited by NO scavenger. Taken together, we conclude that NR-dependent NO production plays an important role in providing protection against Al toxicity by alleviating Al-induced oxidative stress in red kidney bean roots.