Summary In Magnaporthe oryzae, the Pmk1 MAP kinase signaling pathway regulates appressorium formation, plant penetration, effector secretion, and invasive growth. While the Mst11‐Mst7‐Pmk1 cascade was characterized two decades ago, knowledge of its signaling in the intracellular network remains limited. In this study, we demonstrate that the endosomal surface scaffolds Pmk1 MAPK signaling and Msb2 activates Ras2 on endosomes in M. oryzae. Protein colocalization demonstrated that Msb2, Ras2, Cap1, Mst50, Mst11, Mst7, and Pmk1 attach to late endosomal membranes. Damage to the endosome–vacuole transport system influences Pmk1 phosphorylation. When Msb2 senses a plant signal, it internalizes and activates Ras2 on endosome membrane surfaces, transmitting the signal to Pmk1 via Mst11 and Mst7. Signal‐sensing and delivery proteins are ubiquitinated and sorted for degradation in late endosomes and vacuoles, terminating signaling. Plant penetration and lowered intracellular turgor are required for the transition from late endosomes to vacuoles in appressoria. Our findings uncover an effective mechanism that scaffolds and controls Pmk1 MAPK signaling through endosomal–vacuolar transport, offering new knowledge for the cytological and molecular mechanisms by which the Pmk1 MAPK pathway modulates development and pathogenicity in M. oryzae.

中文翻译：

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内体-液泡转运系统充当米瘟病菌中 Pmk1 MAP 激酶信号通路的对接平台


摘要 在米瘟病菌中，Pmk1 MAP 激酶信号通路调节贴壁形成、植物渗透、效应子分泌和侵袭性生长。虽然 Mst11-Mst7-Pmk1 级联反应在二十年前就已形成特征，但对其在细胞内网络中信号传导的了解仍然有限。在这项研究中，我们证明了内体表面支架 Pmk1 MAPK 信号传导和 Msb2 激活米分枝杆菌内体上的 Ras2。蛋白质共定位表明 Msb2 、 Ras2 、 Cap1 、 Mst50 、 Mst11 、 Mst7 和 Pmk1 附着在晚期内体膜上。内体-液泡转运系统的损伤会影响 Pmk1 磷酸化。当 Msb2 感应到植物信号时，它会内化并激活内体膜表面的 Ras2，通过 Mst11 和 Mst7 将信号传递给 Pmk1。信号感应和递送蛋白在晚期内体和液泡中被泛素化并分选降解，终止信号传导。植物渗透和降低的细胞内膨胀是从晚期内体过渡到附着体液泡所必需的。我们的研究结果揭示了一种通过内体-液泡运输支撑和控制 Pmk1 MAPK 信号传导的有效机制，为 Pmk1 MAPK 通路调节米分枝杆菌发育和致病性的细胞学和分子机制提供了新的知识。