The ROP2Involves In The Auxin Rapidly Responsive Regulation Of Vesicular Transport

There are apparently two pathways of the auxin signaling on plants. The one is the F-box protein mediated signal transduction leading to gene expression pattern changes by the receptor TIR that has been better illustrated. But there is another rapid response signaling that do not involve in gene expression regulation, the rapid auxin respond pathway, which is poorly explored. The Auxin Binding Protein1is considered to be the most likely receptor protein in this route. As the plant extracellular signal, auxin binding with ABPl is involved in rapid response of cell in cell elongation thus determines the stem phototropism and actives of the membrane transport. It will affect most of the process of growth and development. The widespread small G proteins, as a molecular switch, play a direct role in the regulation of the cytoskeleton and vesicular transport. There was evidence that ABP1route also conducts signal transmission through such a molecular switch.A G protein family ROPs is only found in plant. We selected the member ROP2as a candidate that may involve in the auxin rapid response signalling. We cloned the cDNA of ROP2from Arabidopsis and then we designed the constitutively active ROP2(CA-ROP2) mutant gene and dominant negative ROP2(DN-ROP2) mutant gene by point mutations through PCR. The mutant sequences and AtROP2cDNA were constructed into a Ti vector pWM101respectively to construct the CA-ROP2, DN-ROP2and OX-ROP2expression vector. The three recombinants were transformed into the BY-2, model plant cell line, which is membrane labeled with GFP and the induciable ABP1overexpression or antisense inhibition are previously transfomed. The6cell lines were screened out and applied in the auxin response confocal observation.The vesicular transport is very active and rapidly responses to the auxin treatment if the ABP1is overexpressed after the estradiol inducing. The vesicular exocytosis is greatly enhanced in CA-ROP2and OX-ROP2cells if the ABPl is overexpressed. But the exocytosis transport is week in DN-ROP2cell line even the ABP1is overexpressed. While the vesicular transport is appearently week in the ABP1inhibited cell whenever the ROP2is in CA, DN or OX state. We concluded that the ROP2participates the ABP1mediated vesicular transport.