Moretti Marino, Wang Lei, Grognet Pierre, Lanver Daniel, Link Hannes, Kahmann Regine
Department of Organismic Interactions, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Strasse 10, Marburg, D-35043, Germany.
Dynamic Control of Metabolic Networks, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Strasse 16, Marburg, D-35043, Germany.
Mol Microbiol. 2017 Sep;105(6):901-921. doi: 10.1111/mmi.13745. Epub 2017 Jul 21.
Regulators of G protein signaling (RGS) proteins modulate heterotrimeric G protein signaling negatively. To broaden an understanding of the roles of RGS proteins in fungal pathogens, we functionally characterized the three RGS protein-encoding genes (rgs1, rgs2 and rgs3) in the phytopathogenic fungus Ustilago maydis. It was found that RGS proteins played distinct roles in the regulation of development and virulence. rgs1 had a minor role in virulence when deleted in a solopathogenic strain. In crosses, rgs1 was dispensable for mating and filamentation, but was required for teliospore production. Haploid rgs2 mutants were affected in cell morphology, growth, mating and were unable to cause disease symptoms in crosses. However, virulence was unaffected when rgs2 was deleted in a solopathogenic strain, suggesting an exclusive involvement in pre-fusion events. These rgs2 phenotypes are likely connected to elevated intracellular cAMP levels. rgs3 mutants were severely attenuated in mating, in their response to pheromone, virulence and formation of mature teliospores. The mating defect could be traced back to reduced expression of the transcription factor rop1. It was speculated that the distinct roles of the three U. maydis RGS proteins were achieved by direct modulation of the Gα subunit-activated signaling pathways as well as through Gα-independent functions.
G蛋白信号调节（RGS）蛋白对异源三聚体G蛋白信号传导起负调节作用。为了更深入了解RGS蛋白在真菌病原体中的作用，我们对植物致病真菌玉米黑粉菌中三个编码RGS蛋白的基因（rgs1、rgs2和rgs3）进行了功能表征。研究发现，RGS蛋白在发育和毒力调节中发挥着不同的作用。在单倍体致病菌株中缺失rgs1时，其对毒力影响较小。在杂交过程中，rgs1对于交配和菌丝形成并非必需，但对冬孢子产生是必需的。单倍体rgs2突变体在细胞形态、生长、交配方面受到影响，并且在杂交中无法引起疾病症状。然而，在单倍体致病菌株中缺失rgs2时，毒力不受影响，这表明它仅参与融合前事件。这些rgs2表型可能与细胞内cAMP水平升高有关。rgs3突变体在交配、对信息素的反应、毒力以及成熟冬孢子形成方面严重减弱。交配缺陷可追溯到转录因子rop1表达降低。据推测，玉米黑粉菌这三种RGS蛋白的不同作用是通过直接调节Gα亚基激活的信号通路以及通过不依赖Gα的功能实现的。
