Functional Analysis Of OsCYP2Which Involved In Aux/IAA Deeradation, Lateral Root Initiation And Pollen Development Of Rice

Auxin plays a pivotal role in many facets of plant development. The mechanism of auxin action is through inducement the interaction of AUX/IAA and ubiquitin protein ligase SCFTIR which mediate the degradation of AUX/IAA protein and then regulate the exspression level of auxin respose genes. Whether other cofactor and chaperone participates auxin signaling pathway is intriguing. Here we screened out a mutant with impaired lateral root development, and we found it was an allele to lrl8which contain a cyclophilin gene OsCYP2mutantion.Oscyp2-1contains a single nucleotide mutation (G457T), resulting in a premature stop codon which leads to series of auxin signal impaired phenotype, including lack of lateral roots, impairment of pollen development and reduced reponse to exogenous auxin treatment. Complementation test was carried out to verify that the altered phenotype in Oscyp2-1is caused by mutation in OsCYP2gene. Characterization of the mutants and functional analysis of OsCYP2provide the following results:(1) Lateral root initiation is blocked in Oscyp2mutant:Investigation of longitudinal sections and the expression patterns of cell cycle markers CycB1;1::GUS in Oscyp2-1primary roots indicates that the first asymmetric anticlinal divisions of the phloem pole pericycle cells was impaired in Oscyp2mutant.(2) Oscyp2mutant showed incomplete pollen development:The anther of Oscyp2-1showed a pale-yellow color, and almost all of the pollens have uneven distributed starch patterns, as revealed by iodium potassium iodide staining. And scanning electron microscopy examination shows the surface of Oscyp2-1mutant pollen is shriveled. Pollinating mutant stigma with wild type pollens produce normal filled seeds, suggesting that the female gametes were not affected in Oscyp2-1mutant.(3) The Oscyp2-1has less degradation rate of AUX/IAA protein subject to auxin treatment:The time-course fluorescence intensity analysis indicated that Oscyp2-1mutant exhibited descendent degradation rate of OsIAAll:GFP subject to NAA treatment.(4) OsCYP2associates with OsSGTl。A yeast two-hybrid screen indicates that OsSGTl can interact with OsCYP2. We performed an in vitro-pull down assay between His-OsSGTl and GST-OsCYP2, and test of the interaction between OsCYP2and OsSGTl in tobacco leave by firefly luciferase complementation imaging (LCI) assays. The results gave evidence for an interaction between OsCYP2and OsSGTl in living plant cells.In summary,OsCYP2is involved in auxin-mediated regulation of lateral root initiation and pollen development.OsCYP2may asist auxin signaling transducing by working together with cochaperone OsSGTl.