Abstract:

The activity of plasma membrane (PM) nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and its catalytic properties in rice was investigated under drought stress conditions. Drought stress led to decreased leaf relative water content (RWC) and, as a result of drought-induced oxidative stress, the activities of antioxidant enzymes increased significantly. More interestingly, the intensity of applied water stress was correlated with increased production of H₂O₂ and O₂⁻ and elevated activity of PM NADPH oxidase, a key enzyme of reactive oxygen species generation in plants. Histochemical analyses also revealed increased H₂O₂ and O₂⁻ production in drought-stressed leaves. Application of diphenylene iodonium (DPI), an inhibitor of PM NADPH oxidase, did not alleviate drought-induced production of H₂O₂ and O₂⁻. Catalysis experiments indicated that the rice PM NADPH oxidase was partially flavin dependent. The pH and temperature optima for this enzyme were 9.8 and 40 ℃, respectively. In addition, drought stress enhanced the activity under alkaline pH and high temperature conditions. These results suggest that a complex regulatory mechanism, associated with the NADPH oxidase-H₂O₂ system, is involved in the response of rice to drought stress.
 

Duan ZQ, Bai L, Zhao ZG, Zhang GP, Cheng FM, Jiang LX, Chen KM (2009). Drought-stimulated activity of plasma membrane nicotinamide adenine dinucleotide phosphate oxidase and its catalytic properties in rice. J. Integr. Plant Biol. 51(12), 1104–1115.

Key words: catalytic properties, drought stress, plasma membrane NADPH oxidase, reactive oxygen species, rice (Oryza sativa).