Abstract
There is little information available to decipher the interaction between molybdenum (Mo) and nitric oxide (NO) in mitigating arsenic (As-V) stress in plants. The present work highlights the associative role of exogenous Mo and endogenous NO signaling in regulating As-V tolerance in wheat seedlings. Application of Mo (1 mu M) on 25-day-old wheat seedlings grown in the presence (5 mu M) or absence of As-V stress caused improvement of photosynthetic pigment metabolism, reduction of electrolytic leakage and reactive oxygen species (ROS), and higher accumulation of osmolytes (praline and total soluble sugars). The molybdenum treatment upregulated antioxidative enzymes, such as superoxide dismutase, ascorbate pemxidase and glutathione reductase. In addition, the accumulation of nonenzymatic antioxidants (ascorbate and glutathione) was correlated with an increase in ascorbate peroxidase and glutathione reductase activity. The application of cPTIO (endogenous NO scavenger; 100 mu M) reversed the Mo-mediated effects, thus indicating that endogenous NO may accompany Mo-induced mitigation of As-V stress. Mo treatment stimulated the accumulation of endogenous NO in the presence of As-V stress. Thus, it is evident that Mo and NO-mediated As-V stress tolerance in wheat seedlings are primarily operative through chlorophyll restoration, osmolytes accumulation, reduced electrolytic leakage, and ROS homeostasis.