| The proton-pump ATPase(FTH-ATPase) of the plant plasma membrane (PM), known as a "master enzyme" in plant, acts as a primary transporter by pumping protons out of the cell, thereby creating pH and electrical potential differences across the plasma membrane. This provides a driving force for solute transport at the plasma membrane. The plasma membrane H+-ATPase is involved in many important physiological functions, including cell elongation, stomata movement, stress responses and cellular responses to a number of factors such as plant regulators, light and fungal toxins. Even it is probably a direct target molecule of plant hormones. Jasmonic acid and its derivatives (JAs), a kind of plant endogenous compounds, have ubiquitous physiological effect on plant growth and development. But our present knowledge of JAs signaling pathway is very limited. In the present study we firstly investigate the effect of MeJA on plasma membrane H+-ATPase hydrolysis activity and the phosphorylation and dephosphorylation of the enzyme after MeJA treatment comparing to fusicosin (FC) function. Moreover, the role of the calcium ion in MeJA- and FC-induced increases of the plasma membrane H-ATPase was studied.1. Characteristic properties of the plasma membrane H+-ATPase3-d-old seedlings of etiolated mung bean (Vigna radiata L) were harvested and the hypocotyls (1-2 cm in length) under hook were used to prepare the plasma membrane vesicles by means of aqueous two-phase partition. The possible contamination of other organelle membranes was determined by using markers of enzyme inhibitors in different organelle membranes such as vanadate, azide, molybdate and NOs". The aqueous two-phase partition method is based on weight, when the proportion of the weight of hypocotyls and two-phase partition reached 32 ." 8g, the plasma membrane vesicles of mung bean were purified well. The concentration of BSA in homogenization medium influenced the latency activity ofthe PM tT-ATPase. 0.5% BSA was suitable in our experiment.Characteristic properties of the plasma membrane H+-ATPase were investigated firstly. An optimum pH for PM H+-ATPase hydrolysis activity was around 7.0, and the optimum temperature was 37 in vitro. Thaw/freezing decreased the enzyme hydrolysis activity in our experiment.Mg 2+ ion was necessary for PM hT-ATPase full hydrolysis activity and K+ stimulated enzyme activity slightly. ATPase activity reached to the highest when both Mg2+and K+were present in the reaction medium.2. The influence of MeJA and FC on the PM IT- ATPase hydrolysis activityPM IT^-ATPase hydrolysis activities were determined in responding to the treatment of MeJA. The enzyme activities reached to maximum when pH was 7.0 to 7.5 hi assay medium.Application of MeJA (50 u mol/L) to 3-d-old seedlings resulted in an increase in PM tT-ATPase activity in vivo. PM H+-ATPase hydrolysis activity increased 30% comparing to the control. The levels of stimulation by 10 u mol/L MeJA in vitro also showed about 30% increase of the enzyme activity 2hr after incubation of membrane vesicles with. MeJA.FC stimulated the PM H+-ATPase activity and the maximal increase reached to 72% in vitro, while it had the same stimulation (about 30%) of enzyme activity as MeJA had in vivo. The combination of MeJA and FC did not show significant additive effect on enzyme activity.3. Phosphorylation and dephosphorlation of PM H^-ATPase after treatments of MeJA and FC1) In vitro, phosphatase inhibitors, okadaic acid and cantharidin, enhanced MeJA-induced increase of the enzyme activity to 60% and 50%, respectively. Staurosporine and cheleythrine, two inhibitors of protein kinase, inhibited the stimulation of MeJA on PM H+-ATPase activity completely.2) Both protein kinase inhibitors and phosphatase inhibitors showed the same effect on FC-induced increases of enzyme activities.3) The results from y-32p tracing experiments showed that the level of isotop labeling on PM H+-ATPase increased after treatment with MeJA and FC, respectively. Okadaic...
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