The (1,3)β‐ d ‐glucan synthase subunit Bgs1p is responsible for the fission yeast primary septum formation

The cell-integrity and stress-response MAP kinase pathways (CIP and SRP, respectively) are stimulated by various environmental stresses. Ssp1 kinase modulates actin dynamics and is rapidly recruited to the plasma membrane following osmotic stress. Here, we show that osmotic stress arrested tip growth, induced the deposition of abnormal cell-wall deposits at tips and led to disassociation of F-actin foci from cell tips together with a reduction in the amount of F-actin in these foci. Osmotic stress also `froze' the dynamics of interphase microtubule bundles, with microtubules remaining static for approximately 38 minutes (at 30°C) before fragmenting upon return to dynamic behaviour. The timing with which microtubules resumed dynamic behaviour relied upon SRP activation of Atf1-mediated transcription, but not on either CIP or Ssp1 signalling. Analysis of the recovery of tip growth showed that: (1) the timing of recovery was controlled by SRP-stimulated Atf1 transcription; (2) re-establishment of polarized tip growth was absolutely dependent upon SRP and partially dependent upon Ssp1 signalling; and (3) selection of the site for polarized tip extension required Ssp1 and the SRP-associated polarity factor Wsh3 (also known as Tea4). CIP signalling did not impact upon any aspect of recovery. The normal kinetics of tip growth following osmotic stress of plo1.S402A/E mutants established that SRP control over the resumption of tip growth after osmotic stress is distinct from its control of tip growth following heat or gravitational stresses.

Section: Discussionmentioning

confidence: 99%

Stress-regulated kinase pathways in the recovery of tip growth and microtubule dynamics following osmotic stress inS. pombe

Robertson

Hagan

2008

“…This is essential for formation of the division septum, and does not occur until late anaphase (Cortes et al, 2007;. Moreover, its localisation depends upon an active SIN (Liu et al, 2002).…”

Section: Does Cdc2p Inhibit the Sin In Early Mitosis?mentioning

confidence: 99%

Chemical genetic analysis of the regulatory role of Cdc2p in theS. pombeseptation initiation network

Dischinger

Krapp

Xie

et al. 2008

The protein kinase Cdc2p is the master regulator of cell cycle progression in the fission yeast Schizosaccharomyces pombe. It is required both for entry into mitosis and for onset of DNA replication. Cdc2p must be inactivated to permit exit from mitosis, licensing of replication origins and cytokinesis. To study the role of Cdc2p in greater detail, we generated a cdc2 allele that is sensitive to an inhibitory ATP analogue. We show that the inhibitor-induced cell cycle arrest is reversible and examine the effect of inhibiting Cdc2p on the regulation of the septation initiation network (SIN), which controls the initiation of cytokinesis in S. pombe. We found that specific inactivation of Cdc2p in a mitotically arrested cell promotes the asymmetrical recruitment of SIN proteins to the spindle poles and the recruitment of the most downstream SIN components and β-(1,3) glucan synthase to the contractile ring. Thus, we conclude that inactivation of Cdc2p is sufficient to activate the SIN and promote cytokinesis.

“…Cells with mutations in mok1 + /ags1 + lyse during cell separation at the end of cytokinesis. Schizosaccharomyce pombe has four transmembrane enzymes that synthesize β-D-glucans -Bgs1p, Bgs3p and Bgs4p are required for cell wall integrity during vegetative growth, and Bgs2p is required during spore formation (Cortes et al, 2005(Cortes et al, , 2002(Cortes et al, , 2007Liu et al, 2000Liu et al, , 2002Liu et al, , 1999Martin et al, 2003Martin et al, , 2000. Bgs1p, Bgs3p and Bgs4p appear to contribute at different stages of septum formation.…”

Section: Introductionmentioning

confidence: 99%

“…Bgs1p, Bgs3p and Bgs4p appear to contribute at different stages of septum formation. Bgs1p is the first of these enzymes to be recruited to the cleavage site and synthesizes the primary septum (Cortes et al, 2005(Cortes et al, , 2007Martin et al, 2003). Mutations in the cps1 + /bgs1 + gene cause cytokinesis defects (Liu et al, 1999;Cortes et al, 2007); ∼40% of contractile rings are poorly anchored so they slide to one end of the cell, and some contractile rings fail to constrict (Arasada and Pollard, 2014).…”

Section: Introductionmentioning

confidence: 99%

A role for F-BAR protein Rga7p during cytokinesis in S. pombe

Arasada

Pollard

2015

F-BAR proteins are known to participate in cytokinesis, but their mechanisms are not well understood. Here we investigated Rga7p an S. pombe F-BAR protein with a RhoGAP domain. Localization of Rga7p to the cytokinetic cleavage furrow depends on its F-BAR domain, actin filaments, formins Cdc12p and For3p, and the presence of a contractile ring. Rga7p is not required for the constriction of the contractile ring but does participate in the transport of a β-glucan synthetase Bgs4p from the late Golgi compartments to the plasma membrane adjacent to the contractile ring. Cells without Rga7p moved Bgs4p normally from the poles to the Golgi apparatus near the cell center, but Bgs4p then moved slowly from the late Golgi compartments to the cleavage site. The late arrival and lower than normal numbers of Bgs4p result in septal defects late in cytokinesis and lysis of separating cells similar to cells with the mutations in the cwg1+ gene encoding Bgs4p.