Abstract
The proper timing and positioning of cytokinesis/septation is crucial for hyphal growth and conidiation in Aspergillus nidulans. The septation initiation network (SIN) components are a conserved spindle pole body (SPB) localized signaling cascade and the terminal kinase complex SidB-MobA, which must localize on the SPB in this pathway to trigger septation/cytokinesis. The regulatory subunit of phosphatase PP2A-ParA has been identified to be a negative regulator capable of inactivating the SIN. However, little is known about how ParA regulates the SIN pathway and whether ParA regulates the septum formation process through affecting the SPB-localized SIN proteins. In this study, through RNA-Seq and genetic approaches, we identified a new positive septation regulator, a putative mitotic-spindle organizing protein and a yeast Mzt1 homolog MztA, which acts antagonistically toward PP2A-ParA to coordinately regulate the SPB-localized SIN proteins SidB-MobA during septation. These findings imply that regulators, phosphatase PP2A-ParA and MztA counteract the septation function probably through balancing the polymerization and depolymerization of microtubules at the SPB.
Highlights
In all eukaryotic organisms, cytokinesis is the cell division process after the nuclear division of mitosis in which the cytoplasm of a cell is physically partitioned into two
Many lines of evidence have identified that the conserved mitotic exit network (MEN) components, which are tightly connected with cytokinesis, exist in the budding yeast Saccharomyces cerevisiae and mammalian systems (Foltman and SanchezDiaz, 2017; Guo and Segal, 2017; Renicke et al, 2017; Scarfone and Piatti, 2017)
Our previous data confirmed that ParA, a regulatory subunit of protein phosphatase 2A (PP2A), is a negative regulator of septation since deletion of parA causes a hyperseptation phenotype while overexpressing parA results in abolished septum formation in hyphal cells (Zhong et al, 2014)
Summary
Cytokinesis is the cell division process after the nuclear division of mitosis in which the cytoplasm of a cell is physically partitioned into two. A pathway homologous to the MEN, termed the septation initiation network (SIN), has been found to couple mitotic exit with cytokinesis in the fission yeast, Schizosaccharomyces pombe and the model filamentous fungus A. nidulans (Barr and Gruneberg, 2007; Csikasz-Nagy et al, 2007; Zhong et al, 2012; Simanis, 2015). MztA and PP2A-ParA During Septation in A. nidulans are a conserved spindle pole body (SPB) localized signaling cascade, which uses SPB, the functional counterpart of the centrosome in yeasts as a scaffold from which to initiate signaling (Magidson et al, 2006; Lengefeld et al, 2017; Rüthnick et al, 2017). SPB-localized SIN proteins especially Sid2-Mob in S. pombe and SidB-MobA in A. nidulans must transmit signals through the cascade to trigger cytokinesis so that the SPB works as a signaling hub for this process
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