Reactive oxygen species derived from NADPH oxidase regulate autophagy

Reactive oxygen species (ROS) originating from nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) play vital roles in regulating autophagy. However, the relationship between autophagy and NOX in common wheat (Triticum aestivum L.) is still unknown. In order to clarify the mechanism of autophagy in wheat, ROS content, NOX activity, and autophagy levels in root tip cells under condition of N or C deficiency were measured. The results showed that the N and C deficiency increased the production of superoxide anions (O2-.) and hydrogen peroxide (H2O2) via the NOX activation, leading to an increase in the number of autophagic bodies, in comparison to the control group. This showed that autophagy constitutively existed in the root tip cells of wheat seedlings. Interestingly, imidazole, a NOX inhibitor, inhibited the H2O2 and O2-. content and reduced the accumulation of autophagic bodies under N deficiency. Hydrogen peroxide and O2-. derived from NOX possibly regulated autophagy in wheat root tip cells. In order to further verify whether ROS regulated autophagy, exogenous ROS or a reductant was applied to the roots of wheat seedlings under N deficiency. The results showed that exogenous O2-. and H2O2 both induced the accumulation of autophagic bodies in the vacuoles of root tip cells. On the contrary, glutathione and ascorbic acid significantly decreased the accumulation of autophagic bodies. Therefore, this study confirmed that H2O2 and O2-. derived from NOX could regulate autophagy in root tip cells of wheat seedlings under stress.