Expression And Regulation Of OsAQP Gene Expreeion In Rice

Aquaporin is water-specific transporter embedded in biological membrane which widely found inanimals, plants and microbes. The rapid transportation of water by aquaporin are involved in variousprocesses, such as growth, development and abiotic responses in plant.OsAQP is a rice vacuolar membrane-type aquaporin gene highly expressed in leaves guard cells.In order to study its expression profile during rice development and the relationship withphytochrome-mediated light signal pathway, we focus on the flowering time, stomatal density and length ofwild type, phytochrome A and B mutants rice in this report, and the expression pattern of OsAQP in theleaves of three varieties were detected by semi-quantitative RT-PCR and real time PCR. The resultindicates that the stomatal density and length in phytochrome B mutant are lowest compared with the othervarieties at the same stage, indicating that phytochrome B-mediated pathway is involved in the stomadevelopment. qRT-PCR result demonstrated that the expression level of OsAQP in the three varieties aredifferent, but invariably showed downward trend during the development. Taken together, these resultsimplicate rice phytochrome B-mediated light signal pathway in stomatal development, and phytochrome Bpathway may participate in the opening and closing regulation of stoma accompanied by the phytochromeA signaling through the expression regulation of OsAQP.In order to identify effect of abiotic stress on the expression of OsAQP, RT-PCR and qPCR areapplied to analyze the expression profile of OsAQP in the rice seedling leaves after salt and droughttreatment. The result showed that the expression patterns of OsAQP in the three rice materials are different.Among them the changes of OsAQP expression was not significant in the phyA mutant, meanwhile, theexpression peak were appeared in1hour and12h after salt stress in phyB mutant and Wt rice, up to4.5and3.6folds, respectively, which indicated in normal conditions, phytochrome B and its related signal maydecrease the sensitivity to salt stress, suggests there may be some relevance between rice light signalpathway and salt stress response. Under drought treatment, the change of OsAQP in wild type rice wasviolent, up to4.3folds at6h, but both of the variation in phytochrome mutant phyA and phyB were onlywithin2folds. By rice genome databases blast and sequence alignments, the2.29kb-length promoter of OsAQPis obtained, and the cis elements were predicted. The759bp-length promoter was further cloned by PCR,and the GUS fusion carries（OsAQPpro∶GUS）pBI121-OsAQP were constructed. The vector had beentransformed into Arabidopsis thaliana, the T₀transgenic arabidopsis seeds were obtained, help the furtherstudy on the function analysis of the promoter.Taken together, the study provide some important clues for identification the function of OsAQP,and regulation by phytochrome-mediated light signal pathway, also function in the drought and salt stressresponse. It is significant to uncover the plant stress-tolerant molecular mechanism, which provides a newway of crop stress-tolerant breeding by genetic engineering.