Qu Yingmin, Wang Jing, Huang Pengyun, Liu Xiaohong, Lu Jianping, Lin Fu-Cheng
State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, Institute of Biotechnology, Zhejiang University, Hangzhou, China.
College of Life Sciences, Zhejiang University, Hangzhou, China.
Front Plant Sci. 2021 Sep 13;12:702368. doi: 10.3389/fpls.2021.702368. eCollection 2021.
is an important plant pathogenic fungus that can severely damage rice and wheat crops, leading to significant reductions in crop productivity. To penetrate into and invade tissues of its plant host, this fungus relies on an invasive structure known as an appressorium. Appressorium formation is rigorously regulated by the cAMP-PKA and Pmk1 MAPK pathways. Here, we identified PoRal2, a homologous protein of Ral2, and characterized its roles in fungal development and virulence in . PoRal2 contains N-terminal kelch repeats and C-terminal BTB domains. PoRal2 is involved in sporulation, aerial hypha and conidiophore differentiation, appressorium formation, plant penetration, and virulence. During appressorium formation, ∆ mutants generate appressoria with long germ tubes on hydrophobic surfaces. ∆ mutants exhibited a defective response to exogenous cAMP and the activated on a hydrophilic surface, indicating impairment in the cAMP-PKA or Pmk1 MAPK signaling pathways. Deletion of leads to lowered Pmk1 phosphorylation level in the mutant. Moreover, PoRal2 is found to interact with Scd1, Smo1, and Mst50, which are involved in activation of Pmk1. In addition, the expression levels of , , and in the cAMP-PKA pathway, in both the cAMP-PKA and Pmk1 MAPK pathways, and melanin biosynthesis genes (, , and ) were significantly down-regulated in the ∆. Therefore, PoRal2 is involved in fungal development and virulence by its crosstalk in the cAMP-PKA and Pmk1 MAPK signaling pathways.
是一种重要的植物病原真菌，可严重损害水稻和小麦作物，导致作物产量大幅下降。为了穿透并侵入其植物宿主的组织，这种真菌依赖于一种称为附着胞的侵入结构。附着胞的形成受到cAMP-PKA和Pmk1 MAPK信号通路的严格调控。在这里，我们鉴定了PoRal2，它是Ral2的同源蛋白，并表征了其在真菌发育和毒力中的作用。PoRal2包含N端的kelch重复序列和C端的BTB结构域。PoRal2参与孢子形成、气生菌丝和分生孢子梗分化以及附着胞形成、植物穿透和毒力。在附着胞形成过程中，∆突变体在疏水表面产生带有长芽管的附着胞。∆突变体对外源cAMP和亲水表面上激活的 表现出缺陷反应，表明cAMP-PKA或Pmk1 MAPK信号通路受损。缺失 导致突变体中Pmk1磷酸化水平降低。此外，发现PoRal2与参与Pmk1激活的Scd1、Smo1和Mst50相互作用。此外，cAMP-PKA信号通路中的 、 和 的表达水平，cAMP-PKA和Pmk1 MAPK信号通路中的 以及黑色素生物合成基因（ 、 和 ）在∆中均显著下调。因此，PoRal2通过在cAMP-PKA和Pmk1 MAPK信号通路中的相互作用参与真菌发育和毒力。
