The plasma membrane H+-ATPase is related to the development of salicylic acid-induced thermotolerance in pea leaves

The plasma membrane H+-ATPase (PM H+-ATPase, EC.3.6.1.35) plays a key role in the plant response to environmental stress. In this study, a possible mechanistic link between the PM H+-ATPase and salicylic acid (SA)-induced thermotolerance was investigated in pea (Pisum sativum L. cv. NingXia) leaves. The burst of free SA in response to heat acclimation (38 ± 0.5°C) was observed, and peaks appeared subsequently both in activity and amount of PM H+-ATPase in pea leaves during heat acclimation. Similarly, exogenous SA also triggered the two peaks in the room temperature (25 ± 0.5°C). Paclobutrazol (PAC) was employed to infiltrate onto pea leaves prior to heat acclimation treatment. The results showed that the peaks of both free SA and activity of PM H+-ATPase still occurred after the PAC pretreatment. In acquired thermotolerance assessment (malondialdehyde content and degree of wilting), spraying SA and fusicoccin (FC, the activator of PM H+-ATPase) separately could protect pea leaves from heat injury. Results from RT-PCR and western blotting analysis indicated that the increase in activity of the PM H+-ATPase was due to its transcriptional and translational regulation. The subcellular localizations of PM H+-ATPase after the FC or SA pretreatment also showed that the PM H+-ATPase is important to maintain the integrity of plasma membrane against the heat stress. Taken together, these results suggest PM H+-ATPase is related to the development of SA-induced thermotolerance in pea leaves.