The basal transcription factor II H (TFIIH) is a multicomponent complex. In the present study, we characterized a TFIIH subunit Tfb5 by analysing loss‐ and gain‐of‐function mutants to gain a better understanding of the molecular mechanisms underlying stress resistance and pathogenicity in the citrus fungal pathogen Alternaria alternata. Tfb5 deficiency mutants (ΔAatfb5) decreased sporulation and pigmentation, and were impaired in the maintenance of colony surface hydrophobicity and cell wall integrity. ΔAatfb5 increased sensitivity to ultraviolet light, DNA‐damaging agents, and oxidants. The expression of Aatfb5 was up‐regulated in the wild type upon infection in citrus leaves, implicating the requirement of Aatfb5 in fungal pathogenesis. Biochemical and virulence assays revealed that ΔAatfb5 was defective in toxin production and cellwall‐degrading enzymes, and failed to induce necrotic lesions on detached citrus leaves. Aatfb5 fused with green fluorescent protein (GFP) was localized in the cytoplasm and nucleus and physically interacted with another subunit, Tfb2, based on yeast two‐hybrid and co‐immunoprecipitation analyses. Transcriptome and Antibiotics & Secondary Metabolite Analysis Shell (antiSMASH) analyses revealed the positive and negative roles of Aatfb5 in the production of various secondary metabolites and in the regulation of many metabolic and biosynthetic processes in A. alternata. Aatfb5 may play a negative role in oxidative phosphorylation and a positive role in peroxisome biosynthesis. Two cutinase‐coding genes (AaCut2 and AaCut15) required for full virulence were down‐regulated in ΔAatfb5. Overall, this study expands our understanding of how A. alternata uses the basal transcription factor to deal with stress and achieve successful infection in the plant host.

中文翻译：

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基础交替因子II H亚基Tfb5是链格孢（Alternaria alternata）的橘病原型中的应激反应和致病性所必需的。

基底转录因子II H（TFIIH）是一种多组分复合物。在本研究中，我们通过分析功能丧失和获得功能的突变体来表征TFIIH亚基Tfb5，以更好地了解柑橘类真菌病原体链格孢中的抗逆性和致病性的分子机制。Tfb5缺乏突变体（ΔAatfb5）减少了孢子形成和色素沉着，并且在维持菌落表面疏水性和细胞壁完整性方面受到损害。Δ Aatfb5敏感性增加紫外光，DNA损伤剂和氧化剂。柑橘叶片感染后，野生型中Aatfb5的表达上调，暗示了对Aatfb5的需求在真菌的发病机理中。生化和毒力测定结果表明，ΔAatfb5在毒素产生和细胞壁降解酶方面存在缺陷，并且未能在分离的柑橘叶片上诱发坏死性病变。基于酵母双杂交和共免疫沉淀分析，与绿色荧光蛋白（GFP）融合的Aatfb5位于细胞质和细胞核中，并与另一个亚基Tfb2物理相互作用。转录组和抗生素及次级代谢产物分析Shell（antiSMASH）分析揭示了Aatfb5在各种次级代谢产物的产生以及在链球菌中许多代谢和生物合成过程的调节中的正负作用。Aatfb5可能在氧化磷酸化中起负作用，在过氧化物酶体生物合成中起正作用。完全毒力所需的两个角质酶编码基因（AaCut2和AaCut15）在ΔAatfb5中被下调。总的来说，这项研究扩大了我们对交链孢霉如何利用基础转录因子处理压力并成功感染植物宿主的理解。