Reversible protein phosphorylation is crucial for cell signal transduction in stress response. Fusarium oxysporum is a soil inhabiting fungus that can adapt to a wide range of ecological niches and environmental conditions. Three mitogen activated protein kinase (MAPK) cascades have been shown to orchestrate the response of the fungus to external insults such as high temperature, cell wall, oxidative or hyperosmotic stress in F. oxysporum. However, the protein phosphatases that fine-tune phosphorylation levels of different MAPKs in this fungus are unknown. In this study we show that the serine/threonine phosphatase Ptc1 regulates phosphorylation of the high osmolarity glycerol response (HOG) MAPK Hog1 and the cell wall integrity (CWI) MAPK Mpk1. A Δptc1 mutant showed decreased phosphorylation levels of the Mpk1 and was more sensitive to cell wall damaging agents in comparison to the wild type strain. In contrast, this mutant exhibited higher phosphorylation levels of the p38 MAPK Hog1, increased tolerance to osmotic stress compounds and higher expression of genes induced by osmotic stress. Moreover, Δptc1 contained fragmented vacuoles even in absence of the osmotic stressor, supporting the involvement of Ptc1 in the HOG pathway.

中文翻译：

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磷酸酶Ptc1在尖孢镰刀菌CWI和HOG途径介导的应激反应中的作用。

可逆的蛋白质磷酸化对于应激反应中的细胞信号转导至关重要。尖孢镰刀菌（Fusarium oxysporum）是一种土壤真菌，可适应各种生态位和环境条件。已经证明了三个促分裂原活化蛋白激酶（MAPK）级联可以协调真菌对外界伤害的反应，例如高温，细胞壁，氧化假单胞菌的氧化或高渗胁迫。但是，尚不清楚微调该真菌中不同MAPK磷酸化水平的蛋白质磷酸酶。在这项研究中，我们显示丝氨酸/苏氨酸磷酸酶Ptc1调节高渗透压甘油反应（HOG）MAPK Hog1和细胞壁完整性（CWI）MAPK Mpk1的磷酸化。与野生型菌株相比，Δptc1突变体显示Mpk1的磷酸化水平降低，并且对细胞壁破坏剂更敏感。相反，该突变体表现出更高的p38 MAPK Hog1磷酸化水平，对渗透压化合物的耐受性增加以及渗透压诱导的基因的更高表达。而且，即使在没有渗透压的情况下，Δptc1也含有碎片状的液泡，从而支持Ptc1参与HOG途径。