Functional Analysis Of The Disease Resistance To Bacterial Pathogens For OsDRxoc1 Transgenic Rice

Rice bacterial blight (BB) and bacterial leaf streak (BLS) are important bacterial leaf diseases of rice which severely limited the yield and rice quality in China. Although they are causing by different pathovar strains of Xanthomonas oryzae, their infection modes and pathogenic characters are distinguished respectively. In early studies, numerous of BB-resistance genes have been identified. While none of BLS-resistance gene has been found except some small amount of QTL (Quantitative Trait Locus) and a non-host resistance gene Rxol cloned in the corn.The unknown function of OsDRxocl, encoded a putative Myb-like DNA binding protein, was coincided to the location of qBlsr5b, which is a high resistance effect of QTL for BLS resistance. In our previously study, Chen Ming conducted the QsDRxocl-oveierpression and OsDRxocl-RNAi transgenic in rice. He found that different resistant phenotype had been observed for BB and BLS in To genration lines. The OsDRxocl may be involved in the positive regulation of resistance to BLS and negative regulation of resistance to BB. It's expected to reveal the core mechanism of two kinds of disease pathogenic differences.Based on the above studies described, we confirmed that the OsDRxocl-GFP protein was localized to the nucleus of tobacco epidermal cells and the OsDRxoc1 has transcriptional activation activity in yeast. It is suggested that OsDRxoc1 was potentially a plant transcription factor. The expression of OsDRxocl was up-regulated after 8 hours-post-inoculation with Xoc strain RS105 and down-regulated when inoculation Xoo strain PXO99, respectively. In addition,the co-segregation analysis in T1 generation was confirmed that the OsDRooc1-overexpression lines were enhance resistant to RS105 while more susceptible to PXO99. And the turnover phenotype were observed for OsDRxocl-RNAi lines, it became more resistance to PXO99 but more susceptible to RS105 compared to wild type. This was further validated that OsDRxocl was regulated the resistance to RS105 positively and to PXO99 negatively. By the same time, the pathogenesis-related genes PRla and PR10 were up-regulated in O.sDRxocl-overexpression plant after inoculation with RS105. These results suggest that the OsDRxocl gene may positively regulate the resistance to BLS by induced the expression of PR gene in rice.The RNA-sequencing analysis of the OsDRxocl-overexpression, OsDRxocl-RNAi transgenic line and the wild type have also been conducted to identify the differential expression genes (DEGs) between the OsDRxocl-overexpression and the wild type or OsDRxocl-RNAi transgenic line. Among them, about 20.81% of DEGs were involved in plant-pathogen interaction. We further cloned the promoter sequence of DEGs, included with LOC_Os02g27430.1, LOC_Os07g26150.1, LOC_Osl0g25850.1 and LOC_Os03g18779.1. The results demonstrated that OsDRxocl may directly bind to the sequence of the promoter and regulate the expression of these genes after transient co-expression assay. To explore the regulation mechanism of target gene for OsDRxoc1 by ChIP-seq in the future, we constructed the vectors carried Ubi::OsDRxoc1-GFP and transform into rice variety ZH11. The transgenic rice of Ubi::OsDRxoc1-GFP was validated to enhance resistant against RS105.The Gene Ontology result showed that more than 27 DEGs (6.8% of cellular component ontology) were predicted to functional relate to thylakoid. These results may explore that over-expression of OsDRxocl may possibly regulate the expression of thylakoid related genes and participate in chloroplast development, which finally resulted in low chlorophyll content of leaves. Thus, the above results implied that the OsDRxocl gene is not only involved in plant-pathogen interaction, but also invovled in the development of chloroplast.Taken together, our results were not only validated the function of OsDRxocl to resistant to two kinds bacterial diseases, but also analyzed the transcription profiling of the possible target genes. It's laid the foundation for further analysis of the OsDRxocl gene differentially involved in BB and BLS resistance, and also contributes to the study of chloroplast development in plant-pathogen interaction.