Functional Analysis Of Xa13 In Rice-Xoo Interaction And Rice Development

Rice bacterial blight is the most devasting bacterial disease trigged by Xanthomonas ozyza sativa pv. oryza, causing tremendous yield loss each year all over the world. An effective way among such control is the utilization of host resistance genes during agricultural production, the investigation of function and mechanism on disease resistance genes could be accelerate the utilization of these genes with reason, and these have important significance in science and application for lighting disease on rice.xa13, a typical recessive R gene in rice, which is fully recessive and specifically confers resistance to the Philippine Xoo race6 (PXO99), whereas, the dominant Xa13 gene was susceptible to PXO99. Here we report that the promoter of Xa13 gene, which was induced by only PXO99, was sticking point for susceptible to PXO99 during rice-Xoo interaction. We used the promoter of Xa13 gene to regulate xa13 and xal3Leu49(a natural recessive allele of xal3) in the rice line IRBB13 carrying xa13, the transgenic plants showed the same level of susceptibility as those of the rice line carrying dominant Xa13. Constitutive overexpression of Xa13 or different xa13 (xa13, xal3Leu49, xal3Ala85 or xa13Val184) in IRBB13 had no effect on Xoo infection in the transgenic plants, but had negative influence on development. In addition to, Xa13 gene influence many kinds of physiology, such as gibberellin pathway, jasmonate acid pathway and senscence pathway. Constitutive overexpression of Xa13 and xa13 gene could enhance the expression of OsGA2ox genes of gibberellin pathway; AOS2, LOX and AOC genes of jasmonate acid pathway; SAG genes of senscence pathway. However, the AOS2, LOX and AOC genes, and SAG genes during senscence pathway were all suppressed in the Xa13-suppressing transgenic plants, along with lower jasmonate content in leaves. At the same time, the different expression patterns were found between Xa13 gene promoter and xa13 gene promoter, the Xa13 or xa13 gene expression could be detected in vascular bundle of many tissues, only Xa13 gene could be examined in the vascular bundle of leaf, root and branch. And Xa13 or xa13 gene have different response to different hormone and molecular signal.Xa13 gene not only function in disease, but also in pollen development. Xa13 gene influence the stamen and pistil development through in situ hybridization and immunohistochemistry experiments. The reduced fertility within Xa13-suppressing transgenic plants was due to that the development of the most of microspores stopped at the unicellular pollen grain stage or bicellular pollen grain stage, and the development of antipodal cell stopped ahead of schedule.Two new proteins were found which interacting with XA13 through yeast two hybrid, these two proteins OsCOPT1 and OsCOPT5 were belong to a gene family, encoding membrane protein, and function in copper transport. The interaction between XA13 and OsCOPT1 or OsCOPT5 were validated via membrane protein yeast two hybrid, Co-immunoprecipitation, and bimolecular fluorescence complementation experiments in vivo or in vitro. In addition to, we found that XA13 protein was a polytopic membrane protein with the extracellularly located amido-terminal and intracellularly located carboxyl-terminal, and with different amino acid regions to interact with OsCOPT1 or OsCOPT5. Furthermore, OsCOPT1 or OsCOPT5 protein could form homodimer or heterodimer, and these two proteins form a complex with XA13 protein to participate copper pump in.Constitutive overexpressing OsCOPTl or OsCOPT5 gene not only improved copper content, but also caused transgenic plants susceptible to Xoo, as reason that copper was transported from vessel, which was the channel for Xoo growth, to plasma membrane of vascular bundle sheath cell and intercellular space, the lower copper content in vessel of OsCOPT1- or OsCOT5-overexpression transgenic plant could be propitious for Xoo growth. In addition, the interaction between OsCOPT1 or OsCOPT5 and XA13 could influence pollen development.Focus on copper transporter gene family, OsCOPT1 and OsCOPT5 protein possess part "Ctr superfamily" fixation domain, whereas OsCOPT7 protein with the integrity domain, and which could functional complement of the yeast mutant. We also found that the OsCOPTs genes had different expression pattern in tissues, and diversity expression manner under metal sufficiency or deficiency.