Functional Analysis Of Tal(Transcription Activator-like) Genes Of Xanthomonas Oryzae

Xanthomonas oryzae pv. oryzicola (Xoc) and X. oryzae pv. oryzae (Xoo), two pathovars of X. oryzae, cause bacterial leaf streak (BLS) and bacterial blight (BB) of rice (Oryza sativa), respectively. BB is one of the most serious diseases of rice, and BLS is emerging in importance. Rice is a worldwide staple as well as a model for cereal biology. Xoo and Xoc are important both from the standpoint of food security and as models for understanding fundamental aspects of bacterial interactions with plants.The interactions between Xoo, the model pathogen of rice bacterial leaf blight, and rice cultivars are controlled in a gene-for-gene manner. Specific tal genes are existed in different races. PXO99A is the typical representative strain of Xoo.19 tal effector genes were identified in the PXO99A genome in 2008 and the 19 individual genes are distributed in 9 loci in PXO99A.We isolated the 19 tal genes, according to the conservation and the size difference among the genes. To study the function of the tal genes when interacting with the rice and the coordination or inhibition among the genes. Successfully,19 tal genes (two pairs of which are the copies with only one base difference) were cloned and then constructed the genes to the vector pUAV45K(B), which is used to study the function of the tal genes. It provides a fundamental understanding of tal-plant interaction and a contribution to the identification of fitness and virulence of the tal genes.There are at least twenty highly conserved tal family genes in Xoc, which is the causal agent of bacterial leaf streak in rice. However, the contribution of these tal genes to virulence or avirulence in rice to the pathogen is still rudimentary. It is assumed that gradually knocking out tal genes in the bacterium would provide a basis to precisely assess roles of each gene in virulence contribution. In this report, five tal genes were gradually knocked out based on the conserved structure of the family by using marker-exchange mutagenesis mediated by a suicide vector pKMS 1. The knock-out mutation occurred either within a tal gene or between two tal genes. PCR and Southern hybridization analysis demonstrated that the establishment of knock-out mutagenesis in tal genes of Xoc is successful, providing a platform to assess virulence or/and avirulence roles contributed by each member of the tal family in rice.The virulence decresed as the number of the tal genes reduced.Xoo is closely related to Xoc, showing more than 90% similarity by DNA-DNA hybridization. However, they infect their hosts in distinct ways. Genetic resistance to BB and BLS is also distinct. Both the two strains contain multiple tal genes, but the function of the tal genes in the Xoc has not been identified. In this study, we isolated the tal genes from the Xoc RS105 and constructed each gene to the vector containing avrXa7 or avrXa10. In this way, we hope to find out which gene inhibits the avrXa7 or avrXalO expression in Xoc.