Early Activation by Ethylene of the Tonoplast H+-Pumping ATPase in the Latex from Hevea brasiliensis

The treatment of Hevea brasiliensis (rubber tree) bark by chloro-2-ethyl phosphonic acid (ethrel), an ethylene-producing compound, induces a significant increase in the tonoplast H(+)-translocating ATPase activity in the latex during the first 24 hours after the application of the stimulating agent. Moreover, the tonoplast-bound ATPase is highly activated when vacuoles (lutoids) are resuspended in ultrafiltrated cytosol. This effect is amplified during ethrel stimulation. Preliminary assays to characterize the endogenous effector(s) suggest that the activator(s) could be a heat-resistant compound with a low molecular weight, most likely an anion. The activation of the tonoplast-bound ATPase and the associated activation of the protons translocation across the lutoid membrane, could explain the cytosolic alkalinization observed in latex following the ethrel treatment of Hevea bark, which results in an enhanced rubber production.