Nitric Oxide Mediates Molybdenum-Induced Antioxidant Defense in Wheat under Drought Stress

Abstract

Molybdenum (Mo) has been reported to alleviate drought stress by enhancing antioxidant defense in plants, but the underlying mechanism remains unclear. Here, we hypothesized that Mo mediates nitric oxide (NO)-induced antioxidant defense through Mo-enzymes, particularly by nitrate reductase (NR) in wheat under drought stress. The 30-day-old wheat seedlings cultivated in -Mo (0 μM Mo) and +Mo (1 μM Mo) Hoagland solutions were detached and then pretreated with Mo-enzyme inhibitors, NO scavengers, NO donors or their combinations according to demands of complementary experiment under 10% polyethylene glycol 6000 (PEG)-stimulated drought stress (PSD). Mo supplementation increased the activities and transcripts of antioxidant enzymes, decreased H2O2 and MDA contents, and elevated NO production, implying that Mo-induced antioxidant defense may be related to NO signal. Complementary experiment showed that NO production was induced by Mo, while suppressed by Mo-enzyme inhibitors and NO scavengers, but restored by NO donors, suggesting that Mo-induced increase of NO production may be due to the regulation by Mo-enzymes. Further experiment indicated that the increased activities and transcripts of antioxidant enzymes induced by Mo were suppressed by Mo-enzyme inhibitors and NO scavengers, and NO donors could eliminate their suppressing effects. Moreover, Mo application increased NR activity and inhibitors of Mo-enzymes inhibited NR activity in wheat leaves under PSD, suggesting that NR might involve in the regulation of Mo-induced NO production. These results clearly indicate that NO mediates Mo-induced antioxidant defense at least partially through the regulation of NR.

Exogenous Nitric Oxide Improves the Protective Effects of TiO2 Nanoparticles on Growth, Antioxidant System, and Photosynthetic Performance of Wheat Seedlings Under Drought Stress

“…NO and TiO 2 NPs as potential ROS scavengers may directly react with oxygen species and oxidize/ reduce O 2 − /O 2 •to O 2 /H 2 O 2 by increasing consumption of oxygen in mitochondrial respiratory chain (Amini et al 2017;Siddiqui et al 2017). It was also reported that NO and TiO 2 NPs may indirectly promote antioxidant system through up-regulating the expression of antioxidant enzymes which leads to enhanced activities of these enzymes, thereby improving plant tolerance against oxidative stress (Amini et al 2017;Tumburu et al 2015;Wu et al 2017). More recently, alleviation of oxidative stress via improving the activities of antioxidant enzymes such as SOD, CAT, and APX have been reported by application of NO and TiO 2 NPs (Amini et al 2017;Khan 2016;Mohammadi et al 2016;Tripathi et al 2017a, b;Siddiqui et al 2017;Yan et al 2016).…”

“…NO may directly act as an antioxidant and alleviate oxidative damage by scavenging ROS (Sahay and Gupta 2017) or indirectly enhance the antioxidant capacity of cells by increasing the activities of ROS-scavenging enzymes like SOD, CAT, and APX (Siddiqui et al 2017). Recently, it has been shown that NO increased transcripts and activities of antioxidant enzymes (SOD, CAT, APX) in wheat under drought stress and alleviated oxidative damage caused by ROS accumulation (Khan et al 2017b;Wu et al 2017). Moreover, there are growing evidences suggesting that NO can improve photosynthetic performance of plants under drought stress.…”

Molybdenum Application Regulates Oxidative Stress Tolerance in Winter Wheat Under Different Nitrogen Sources

“…For the ascorbate peroxidase (APX; EC 1.11.1.11) activity determination, fresh wheat leaf samples were homogenized with cold 50 mM sodium phosphate (pH 5.5) Wu et al (2017). Briefly, top fully expanded winter wheat leaves were detached (5 cm) from the leaf tip, and 2-cm leaf tip was cut.…”

“…The measurement of O 2 − was visually detected using nitro blue tetrazolium solution (0.5 mg mL −1 ) for 8 h and decolorized in boiling ethanol. The malonaldehyde (MDA) contents were measured according to the method used in our previous study (Wu et al 2017). Fresh wheat samples were thoroughly homogenized with cold TCA (0.1%), and the crude extracts were centrifuged at 4°C for 20 min at 12000 rpm.…”

5-Aminolevulinic Acid-induced Salt Tolerance in Strawberry: Possible Role of Nitric Oxide on Interception of Salty Ions in Roots

“…In plants, nitrate reductase (NR) is the key enzyme for NO production, which catalyzes nitrite reduction to NO using NAD(P)H as co-factor [29]. Up to now, NO has been known to be involved in stomatal movement [30], adventitious root formation [31], avonoid biosynthesis [32], and alleviation of various abiotic stresses [33], such as drought [34,35], chilling [36], freezing [37], and salinity [38]. In rice plants, NO induces antioxidant enzyme activity against salt stress [39].…”