The role of reactive oxygen species in regulation of the plasma membrane H-ATPase activity in Masson pine (Pinus massoniana Lamb.) roots responding to acid stress

To understand the role of reactive oxygen species (ROS) in regulation of the plasma membrane (PM) H-ATPase in acid-stressed Masson pine roots, different acidity (pH 6.6 as the control, pH 5.6 and pH 4.6) of simulated acid rain (SAR) added with and without external chemicals (HO, enzyme inhibitors and ROS scavenger) was prepared. After 30 days of SAR exposure, the plant morphological phenotype attributes, levels of cellular ROS and lipid peroxidation, enzymatic activities of antioxidants, PM nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and PM H-ATPase activity in pine seedlings were measured. Compared with the control, the growth of pine seedlings exposed to SAR in the presence or absence of HO was well-maintained, but the application of NaVO4, 1,3-dimethyl-2-thiourea, N, N-dimethylthiourea (DMTU) and diphenyleneiodonium chloride (DPI) caused a substantial growth inhibition. In addition, SAR exposure, SAR with HO treatment, and SAR with NaVO4 treatment increased the cellular HO content, O content and malondialdehyde (MDA) content, while the use of DMTU and DPI lead to relatively low levels. Similarly, the enzymatic activities of antioxidants, PM NADPH oxidase and PM H-ATPase in acid stressed pine seedlings elevated with the increasing acidity. A significant stimulation of these enzymatic activities obtained from SAR with HO treatment was observed, whereas which decreased obviously with the addition of NaVO4, DMTU and DPI (P < 0.05). Moreover, a positive correlation was found between plant morphological attributes and the PM H-ATPase activity (P < 0.05). Besides, the PM H-ATPase activity positively correlated with the cellular ROS contents and the enzymatic activities of antioxidants and PM NADPH oxidase (P < 0.05). Therefore, the PM H-ATPase is instrumental in the growth of pine seedlings resisting to acid stress by enhancing its activity. The process involves the signaling transduction of cellular ROS and coordination with PM NADPH oxidase.