A Mutant of Arabidopsis thaliana with Decreased Activity of the Plasma-membrane Proton Pump Lacks the Fusicoccin-dependent Stimulation of Ethylene Synthesis

Abstract

Summary Ethylene production by leaves of Arabidopsis thaliana line Landsberg erecta and its stimulation by fusicoccin have been studied both in wild type (La + ) and in a fusicoccin-resistant mutant (5–2) with reduced capability for proton extrusion. This mutant did not show any difference with the wild type in the rate of ethylene production, either basal or dependent on 1-Aminocyclopropane-l-carboxylic acid (ACC) supply. However, when saturating levels of ACC led the ACC oxidase to be the rate limiting reaction, the production of ethylene was strongly stimulated by fusicoccin in the wild type but not in the mutant. The data extend to Arabidopsis leaves the conclusion that the fusicoccin-dependent stimulation of ethylene production involves an activation of the ACC oxidase and supports the hypothesis of a regulation of the last step of ethylene biosynthesis by the plasma membrane (PM) proton pump.