A new identified suppressor of Cdc7p/SepH kinase, PomA, regulates fungal asexual reproduction via affecting phosphorylation of MAPK-HogA

Abstract

The septation initiation network (SIN), composed of a conserved SepH (Cdc7p) kinase cascade, plays an essential role in fungal cytokinesis/septation and conidiation for asexual reproduction, while the mitogen-activated protein kinase (MAPK) pathway depends on successive signaling cascade phosphorylation to sense and respond to stress and environmental factors. In this study, a SepH suppressor–PomA in the filamentous fungus A . nidulans is identified as a negative regulator of septation and conidiation such that the pomA mutant is able to cure defects of sepH1 in septation and conidiation and overexpression of pomA remarkably suppresses septation. Under the normal cultural condition, SepH positively regulates the phosphorylation of MAPK-HogA, while PomA reversely affects this process. In the absence of PbsB (MAPKK, a putative upstream member of HogA), PomA and SepH are unable to affect the phosphorylation level of HogA. Under the osmostress condition, the induced phosphorylated HogA is capable of bypassing the requirement of SepH, a key player for early events during cytokinesis but not for MobA/SidB, the last one in the core SIN protein kinase cascade, indicating the osmotic stimuli-induced septation is capable of bypassing requirement of SepH but unable to bypass the whole SIN requirement. Findings demonstrate that crosstalk exists between the SIN and MAPK pathways. PomA and SepH indirectly regulate HogA phosphorylation through affecting HogA-P upstream kinases.

Aspergillus nidulans Septa Are Indispensable for Surviving Cell Wall Stress

“…Previous studies in Aspergillus fumigatus ( 6 ) and Candida albicans ( 7 ) show that the presence of septa increases cell viability during exposure to cell wall-damaging compounds. Consistent with this, we and others have recently found increased septation as a response to micafungin (a cell wall-damaging echinocandin) exposure ( 8 – 10 ). Specifically, we found that cells treated with micafungin formed more septa per hyphal unit area compared to a control.…”

Dynamic Transcriptomic and Phosphoproteomic Analysis During Cell Wall Stress in Aspergillus nidulans

“…13 ) ( 101 , 102 , 103 , 104 ), thereby reinforcing the notion that pathway cross-talk might be an integral feature of the response to cell wall perturbation. In A. nidulans , Zhou et al recently reported that hyperosmotic stress could trigger septation in a HogA- and SIN-dependent manner ( 105 ). This raises the intriguing possibility that a general function of stress-induced MAP kinase signaling in filamentous fungi might be activation of septum formation.…”

Phosphoproteomic analysis of STRIPAK mutants identifies a conserved serine phosphorylation site in PAK kinase CLA4 to be important in fungal sexual development and polarized growth

“…Neurospora crassa (Jonkers et al, 2014;Xiong et al, 2014). In this work, we present an in-depth quantitative phosphoproteomic data set of S. macrospora in conjunction with corresponding global proteome analysis, allowing for differentiation between changes in total protein ex- across all conditions, our data set exhibits substantially higher coverage than comparable work with other filamentous fungi to date (Franck et al, 2015;Jonkers et al, 2014;Xiong et al, 2014;Zhou, Ye, Zheng, Jiang, & Lu, 2019). Here, we provide the first comprehensive STRIPAKdependent quantitative proteome and phosphoproteome analyses in a eukaryotic organism.…”