通用转录因子TFIIH亚基Tfb5介导的柑橘褐斑病菌致病分子机制研究

柑橘褐斑病是柑橘上重要的真菌病害，而ACT毒素是柑橘褐斑病菌的重要致病因子，抑制ACT毒素则可使病原菌失去致病性。因此，尽快阐明ACT毒素的合成调控机制、寻找阻断ACT毒素合成的关键基因对于实现褐斑病防控具重要意义。我们前期研究发现，柑橘褐斑病菌转录因子Tfb5缺失突变体中ACT毒素合成基因簇基因显著下调，且ACT毒素累积受阻、致病性显著下降，但Tfb5对ACT毒素的分子调控网络尚不清楚。因此本项目一方面进行ChIP-seq，并结合RNA-seq分析获得基因组上Tfb5的靶标基因，明确Tfb5在毒素诱导下对靶标基因转录调控作用和调控网络。另一方面进行免疫亲和捕获，得到与Tfb5共同参与ACT毒素合成的互作蛋白。最后对靶标基因或互作蛋白进行基因敲除，研究突变体的ACT毒素和致病性，最终系统解析Tfb5在ACT毒素合成与致病的调控机制，为开发以阻断ACT毒素为目标的褐斑病防治提供理论依据。

Citrus brown spot is one of the most important fungal disease of citrus. The ACT toxin has been demonstrated to be crucial for pathogenicity in the tangerine pathotype of Alternaria alternata. Blocking the ACT production can break the pathogenicity of A. alternata. Therefore, it is important to clarify the regulation mechanism of ACT and find the key genes that block the synthesis of ACT for development of control technologies of citrus brown spots. Our previous study found that Tfb5 deficient mutants (△Tfb5) was defective in toxin production and failed to induce necrotic lesions on detached citrus leaves. The expression levels of genes involved in the biosynthesis of ACT were downregulated in △Tfb5. However, the pathway for synthesis regulation of Tfb5 on ACT toxin is still unclear. In this project, we plan to a) clarify the by regulation mechanism of Tfb5 on its target genes under the induction of toxins by ChIP-seq and RNA-seq, b) obtain the interacting proteins that participates in the synthesis of ACT toxin by affinity capture assays, c) figure out the biology roles of target genes or interacting proteins in ACT toxin and pathogenicity by construction gene deletion mutants. These results would not only gain a better understanding of molecular mechanisms of ACT toxin and pathogenicity regulated by Tfb5 but also provide theoretical basis for new control technologies of citrus brown spot by blocking ACT toxin secretion.