In yeasts, ferric reductase catalyzes reduction of ferric ion to ferrous form, which is essential for the reductive iron assimilation system. However, the physiological roles of ferric reductases remain largely unknown in the filamentous fungi. In this study, genome-wide annotation revealed thirteen ferric reductase-like (Fre) proteins in the filamentous insect pathogenic fungus , and all their functions were genetically characterized. Ferric reductase family proteins exhibit different sub-cellular distributions (e.g., cell periphery and vacuole), which was due to divergent domain architectures. Fre proteins had a synergistic effect on fungal virulence, which was ascribed to their distinct functions in different physiologies. Ten Fre proteins were not involved in reduction of ferric ion in submerged mycelia, but most proteins contributed to blastospore development. Only two Fre proteins significantly contributed to vegetative growth under the chemical-induced iron starvation, but most Fre proteins were involved in resistance to osmotic and oxidative stresses. Notably, a bZIP-type transcription factor HapX bound to the promoter regions of all FRE genes in , and displayed varying roles in the transcription activation of these genes. This study reveals the important role of BbFre family proteins in development, stress response, and insect pathogenicity, as well as their distinctive role in the absorption of ferric iron from the environment.

中文翻译：

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铁还原酶样蛋白在丝状昆虫病原真菌白僵菌生长、发育、应激反应和毒力中的重要作用

在酵母中，三价铁还原酶催化三价铁离子还原为亚铁形式，这对于还原性铁同化系统至关重要。然而，丝状真菌中三价铁还原酶的生理作用仍然很大程度上未知。在这项研究中，全基因组注释揭示了丝状昆虫病原真菌中的13种铁还原酶样（Fre）蛋白，并且它们的所有功能都得到了遗传表征。三价铁还原酶家族蛋白表现出不同的亚细胞分布（例如细胞外周和液泡），这是由于不同的结构域结构所致。Fre蛋白对真菌毒力具有协同作用，这归因于它们在不同生理学中的不同功能。十种 Fre 蛋白不参与沉水菌丝体中铁离子的还原，但大多数蛋白有助于芽生孢子的发育。只有两种 Fre 蛋白在化学诱导的铁饥饿下对营养生长有显着贡献，但大多数 Fre 蛋白参与抵抗渗透和氧化应激。值得注意的是，bZIP 型转录因子 HapX 与所有 FRE 基因的启动子区域结合，并在这些基因的转录激活中发挥不同的作用。这项研究揭示了 BbFre 家族蛋白在发育、应激反应和昆虫致病性中的重要作用，以及它们在从环境中吸收三价铁中的独特作用。