Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung Hsing University, Taichung 40227, Taiwan.
Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung Hsing University, Taichung 40227, Taiwan.
Fungal Genet Biol. 2020 Jun;139:103384. doi: 10.1016/j.fgb.2020.103384. Epub 2020 Apr 9.
The siderophore-mediated iron uptake machinery is required by the tangerine pathotype of Alternaria alternata to colonize host plants. The present study reports the functions of the GATA-type transcription regulator SreA by analyzing loss- and gain-of-function mutants. The expression of sreA is transiently upregulated by excess iron. The sreA deficiency mutant (ΔsreA) shows severe growth defect but produces ACT toxin and incites necrotic lesions on citrus leaves as efficiently as wild type. SreA suppresses the expression of genes encoding polypeptides required for siderophore biosynthesis and transport under iron-replete conditions. Under iron-replete conditions, SreA impacts the expression of the genes encoding the NADPH oxidase complex involved in HO production. SreA negatively impacts HO resistance as ΔsreA increases resistance to HO. However, sreA deficiency has no effects on the expression of genes encoding several key factors (Yap1, Hog1, and Skn7) involved in oxidative stress resistance. ΔsreA increases resistance to calcofluor white and Congo red, which may suggest a role of SreA in the maintenance of cell wall integrity. Those are novel phenotypes associated with fungal sreA. Overall, our results indicate that SreA is required to protect fungal cells from cytotoxicity caused by excess iron. The results also highlight the regulatory functions of SreA and provide insights into the critical role of siderophore-mediated iron homeostasis in resistance to oxidative stress in A. alternata.
铁载体介导的铁摄取机制是柑橘盘长孢菌橙色致病型定植宿主植物所必需的。本研究通过分析缺失和获得功能突变体，报告了 GATA 型转录调节因子 SreA 的功能。过量铁会使 sreA 的表达短暂上调。sreA 缺陷突变体（Δ sreA）表现出严重的生长缺陷，但与野生型一样有效地产生 ACT 毒素并引发柑橘叶片坏死病变。SreA 在铁充足条件下抑制铁载体生物合成和转运所需多肽编码基因的表达。在铁充足条件下，SreA 影响参与 HO 产生的 NADPH 氧化酶复合物相关基因的表达。SreA 对 HO 抗性有负面影响，因为Δ sreA 增加了对 HO 的抗性。然而，sreA 缺失对编码几种关键因子（Yap1、Hog1 和 Skn7）的基因表达没有影响，这些因子参与氧化应激抗性。Δ sreA 增加了对 Calcofluor White 和刚果红的抗性，这可能表明 SreA 在维持细胞壁完整性方面发挥作用。这些是与真菌 sreA 相关的新表型。总的来说，我们的结果表明 SreA 是保护真菌细胞免受过量铁引起的细胞毒性所必需的。结果还突出了 SreA 的调节功能，并深入了解了铁载体介导的铁稳态在柑橘盘长孢菌对氧化应激抗性中的关键作用。
