The infection and colonization of pathogenic fungi are often regulated by transcription factors. In our previous study, the zinc finger protein-encoding gene StMR1 was found to be highly expressed during the infection process of Setosphaeria turcica, the pathogen causing northern corn leaf blight. Evolutionary tree analysis showed that this gene was associated with regulatory factors of melanin synthesis. However, the regulatory mechanism of melanin synthesis and its effect on pathogenicity remain unclear. In this study, the function of StMR1 was analyzed by gene knockout. When the expression level of StMR1 in the mutants was significantly reduced, the colony color became lighter, the mycelia were curved and transparent, and the mutant showed a significant loss of pathogenicity. In addition, compared with wild-type, the accumulation of melanin decreased significantly in ΔStmr1. RNA-seq analysis revealed 1,981 differentially expressed genes between the wild-type and knockout mutant, among which 39 genes were involved in melanin metabolism. qPCR revealed that the expression levels of six key genes in the melanin synthesis pathway were significantly reduced. ChIP-PCR and yeast one-hybrid assays confirmed that StMR1 directly binds to the promoters of St3HNR, St4HNR, StPKS, and StLAC2 in the DHN melanin synthesis pathway and regulates gene expression. The C2H2-type zinc fingers and Zn(Ⅱ)2Cys6 binuclear cluster in StMR1 were important for the binding to targets.

中文翻译：

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锌指蛋白StMR1影响Setosphaeria turcica的致病性和黑色素合成，直接调控DHN黑色素合成途径基因的表达

病原真菌的感染和定殖通常受转录因子的调节。在我们之前的研究中，发现编码锌指蛋白的基因StMR1在引起北方玉米叶枯病的病原体Setosphaeria turcica的感染过程中高度表达。进化树分析表明，该基因与黑色素合成的调控因子有关。然而，黑色素合成的调控机制及其对致病性的影响仍不清楚。在本研究中，通过基因敲除分析了StMR1的功能。当StMR1的表达水平突变体中明显减少，菌落颜色变浅，菌丝弯曲透明，突变体表现出显着的致病性丧失。此外，与野生型相比，Δ Stmr1中黑色素的积累显着减少。RNA-seq 分析显示野生型和敲除突变体之间有 1,981 个差异表达基因，其中 39 个基因参与黑色素代谢。qPCR 显示黑色素合成途径中六个关键基因的表达水平显着降低。ChIP-PCR 和酵母单杂交试验证实 StMR1 直接与St3HNR、St4HNR、StPKS和StLAC2的启动子结合在DHN黑色素合成途径中并调节基因表达。StMR1中的C2H2型锌指和Zn(Ⅱ)2Cys6双核簇对与靶标的结合很重要。