Microtubule Dynamics Involves In The Protein (de) Phosphorylation Signaling Pathway In Stomatal Movement

To investigate the role of reversible protein phosphorylation in microtubule-involved guard cell signaling processes,the stomatal aperture and the dynamic organization of cortical microtubules(MTs) have been studied by some specific inhibitors of protein kinases and phosphatases.It was found that:(ⅰ)both serine/threonine kinase inhibitor staurosporine(STS) and tyrosine kinase inhibitor genistein promoted stomatal opening in the light;and vinblastine,a microtubule-depolymerizing herbicide,was able to partially reduce these effects;whereas taxol, a microtubule-stabilizing agent,had the opposite function.However,the treatment of these two kinase inhibitors could not lead to the observable microtubules reorientation in guard cells.(ⅱ)all tested types of protein phosphatases inhibitors,like 1/2A phosphatase inhibitors okadaic acid (OA),calyculin A(CalA) and tyrosine phosphatase inhibitor phenylarsine oxide(PAO) could all prevent light-induced stomatal opening,and 1/2A phosphatase inhibitors have stronger effects. Similarly,MT-specific drugs,both vinblastine and taxol have the abilities to enhance or reduce this inhibitory effect,respectively.Furthermore,treating GFP-α-tubulin-6 leaves with OA/CalA or PAO,the organization of microtubules in guard cells had changed dramatically.In the presence of OA or CalA,the normal parallel,straight and dense microtubule bundles began to break down or rearranged into random network;As to PAO,its treatment caused most cortical microtubules depolymerized and dispersed throughout the cells.All the results suggest that reversible protein phosphorylation may regulate the dynamic organization of guard cell microtubules,and microtubule dynamics seems to be more sensitive when protein was in phosphorylated status than its behaviors in protein dephosphorylation.