Plasma Membrane H～+-ATPase Is Involved In Stomatal Movement Regulation In Arabidopsis Thaliana

Intracellular metabolism in guard cells play an important role in stomatal movement of higher-plants.Hence,signal transduction in guard cells has a close relation with stomatal movement.It is well-known that proton pumps which exsist in plasma membrane induce H⁺-efflux from cytoplasm,alter membrane voltage and evoke some signal transduction cascades.In order to verify the role of proton pump in stomatal movement,the effect of its activator(fusicoccin)and inhibitor(sodium vanadate)on stomatal movements and cytosolic Ca²⁺concentration in guard cells of Araidopsis thaliana was investigated,by using plant physiological methods and fluorescence ratio photometry.The results showed that,after fusicoccin treatment,the stomatal aperture became wider and cytosolic Ca²⁺concentration elevated simultaneously.Stomatal aperture became narrower after sodium vanadate treatment,and cytosolic Ca²⁺concentration decreased simultaneously.Suggesting that,as a positive regulator,proton pump in plasma membrane is involved in stomatal movement by modulating cytosolic Ca²⁺ concentration.Heterotrimeric G protein also participates in transmembrane signal transduction. Here,heterotrimeric G proteinαsubunit null mutant and overexpression lines of Arabidopsis thaliana was used as material.The effect of fusicoccin and sodium vanadate on stomatal movement and cytosolic calcium concentration in different genotypes was investigated and compared.The results showed that,after adding these reagents into extracellular solution,the reactions of stomatal movement and cytosolic calcium concentration in different genotypes were quite similar.It seems that heterotrimeric G-protein locate on upstream of proton pump,or there is no direct relation between these two signal transducers.