Glucose-6-Phosphate Dehydrogenase Plays a Pivotal Role in Nitric Oxide-Involved Defense Against Oxidative Stress Under Salt Stress in Red Kidney Bean Roots

Abstract

The pivotal role of glucose-6-phosphate dehydrogenase (G-6-PDH)-mediated nitric oxide (NO) production in the tolerance to oxidative stress induced by 100 mM NaCl in red kidney bean (Phaseolus vulgaris) roots was investigated. The results show that the G-6-PDH activity was enhanced rapidly in the presence of NaCl and reached a maximum at 100 mM. Western blot analysis indicated that the increase of G-6-PDH activity in the red kidney bean roots under 100 mM NaCl was mainly due to the increased content of the G-6-PDH protein. NO production and nitrate reductase (NR) activity were also induced by 100 mM NaCl. The NO production was reduced by NaN(3) (an NR inhibitor), but not affected by N(omega)-nitro-L-arginine (L-NNA) (an NOS inhibitor). Application of 2.5 mM Na(3)PO(4), an inhibitor of G-6-PDH, blocked the increase of G-6-PDH and NR activity, as well as NO production in red kidney bean roots under 100 mM NaCl. The activities of antioxidant enzymes in red kidney bean roots increased in the presence of 100 mM NaCl or sodium nitroprusside (SNP), an NO donor. The increased activities of all antioxidant enzymes tested at 100 mM NaCl were completely inhibited by 2.5 mM Na(3)PO(4). Based on these results, we conclude that G-6-PDH plays a pivotal role in NR-dependent NO production, and in establishing tolerance of red kidney bean roots to salt stress.

Enzymatic activity in braúna seeds subjected to thermal stress

“…Because it is the first NADPHgenerating enzyme in the pentose phosphate pathway (WAKAO et al, 2008), G6PdH-deficient cells are highly sensitive to oxidative stress, in contrast to those expressing appropriate levels of enzyme activity (LIU et al, 2007). The fact that G6PdH is a regulatory enzyme in this oxidative pathway (TAIZ & ZEIGER, 2013) suggests that the stress caused by the temperatures during seed germination of M. brauna likely resulted in less available energy for biosynthetic processes during germination, owing to lower enzyme activity.…”

Role of Nitric Oxide in Salt Stress-induced Programmed Cell Death and Defense Mechanisms

“…NaCl-induced NO synthesis was inhibited by the NOS inhibitor L-NAME in Atriplex centralasiatica (Xu et al 2011a), Olea europaea (Valderrama et al 2007), Phragmites communis (Zhao et al 2004), and Populus euphratica (Zhang et al 2007). In contrast, Liu et al (2007) reported that NO production, induced by 100 mM NaCl, was not affected by L-NAME in Phaseolus vulgaris. In Arabidopsis thaliana, Zhao et al (2007a) observed a reduced quantity of the NOA1 protein and decreased NO levels after being exposed to 100 mM NaCl for 2 h. AtNOAl {AtNOSl) was identified as a putative Arabidopsis NOS gene, because these Arabidopsis mutants were defective in NO accumulation in the roots (Guo et al 2003), but later it was found that AtNOSl had; no NOS activity in vitro.…”

“…In contrast, higher activities of POX, APX, and GR were observed in the NO-deficient Atnoal plants, and these mutants also showed lower activities of SOD and CAT than wild-type plants under NaCl stress (Zhang et al 2010). 0.05 mM of SNP increased the activity of APX, whereas it decreased that of SOD and POD, and did not affect the activity of CAT in the roots of Phaseolus vulgaris plants exposed to high salinity (Liu et al 2007). The NO donor SNP can also control the level of non-enzymatic antioxidants, such as those of ascorbate or glutathione.…”

Induction of alternative respiratory pathway involves nitric oxide, hydrogen peroxide and ethylene under salt stress

“…4 Salt stress can lead to an accumulation of high levels of ROS, such as superoxide (O 2 -·), hydrogen peroxide (H 2 O 2 ) and hydroxyl radicals (OH·). 5,6 These may disturb cellular redox homeostasis, and then lead to oxidative damage. It has been shown that the AP may participate in the adaptation to salt stress since salt stress increased the activity of the AP.…”