Zuchman Rina, Koren Roni, Horwitz Benjamin A
Faculty of Biology, Technion-Israel Institute of Technology, Haifa 3200003, Israel.
Smoler Protein Center, Technion-Israel Institute of Technology, Haifa 3200003, Israel.
J Fungi (Basel). 2021 Jan 26;7(2):83. doi: 10.3390/jof7020083.
Protein phosphorylation cascades are universal in cell signaling. While kinome diversity allows specific phosphorylation events, relatively few phosphatases dephosphorylate key signaling proteins. Fungal mitogen activated protein kinases (MAPK), in contrast to their mammalian counterparts, often show detectable basal phosphorylation levels. Dephosphorylation, therefore, could act as a signal. In , the Dothideomycete causing Southern corn leaf blight, ferulic acid (FA)-an abundant phenolic found in plant host cell walls-acts as a signal to rapidly dephosphorylate the stress-activated MAP kinase Hog1 (High Osmolarity Glycerol 1). In order to identify the protein phosphatases responsible, we constructed mutants in Hog1 phosphatases predicted from the genome by homology to yeast and other species. We found that mutants lacking PtcB, a member of the PP2C family, exhibited altered growth, sporulation, and attenuated dephosphorylation in response to FA. The loss of the dual-specificity phosphatase CDC14 led to slow growth, decreased virulence, and attenuated dephosphorylation. Mutants in two predicted tyrosine phosphatase genes PTP1 and PTP2 showed normal development and virulence. Our results suggest that a network of phosphatases modulate Hog1's dual phosphorylation levels. The mutants we constructed in this work provide a starting point to further unravel the signaling hierarchy by which exposure to FA leads to stress responses in the pathogen.
蛋白质磷酸化级联反应在细胞信号传导中普遍存在。尽管激酶组的多样性允许特定的磷酸化事件发生，但相对较少的磷酸酶能使关键信号蛋白去磷酸化。与哺乳动物的丝裂原活化蛋白激酶（MAPK）不同，真菌的MAPK通常显示出可检测到的基础磷酸化水平。因此，去磷酸化可能起到信号的作用。在引起玉米南方叶枯病的座囊菌中，阿魏酸（FA）——一种在植物宿主细胞壁中大量存在的酚类物质——作为一种信号，能迅速使应激激活的MAP激酶Hog1（高渗甘油1）去磷酸化。为了鉴定负责的蛋白磷酸酶，我们通过与酵母和其他物种的同源性，构建了从基因组预测的Hog1磷酸酶突变体。我们发现，缺乏PP2C家族成员PtcB的突变体，其生长、孢子形成发生改变，并且对FA的去磷酸化作用减弱。双特异性磷酸酶CDC14的缺失导致生长缓慢、毒力降低以及去磷酸化作用减弱。两个预测的酪氨酸磷酸酶基因PTP1和PTP2的突变体显示出正常的发育和毒力。我们的结果表明，一个磷酸酶网络调节着Hog1的双重磷酸化水平。我们在这项工作中构建的突变体为进一步揭示FA暴露导致病原体应激反应的信号层次提供了一个起点。
