Mitosis in Filamentous Fungi

Harris, Steven D.

doi:10.1007/3-540-28135-5_3

Cited by 6 publications

(3 citation statements)

References 94 publications

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“…These observations do not fully eliminate the possibility that Bud4 functions as a scaffold for recruitment of the Rho4 GTPase module to septation sites as proposed for N. crassa, but are more consistent with the notion that Bud3 and Bud4 independently contribute to septum formation in A. nidulans. This difference is perhaps not too surprising given the distinct mitotic strategies employed by these two fungi (Harris, 2006). Unlike the parasynchronous mitoses of A. nidulans, N. crassa mitoses are completely asynchronous, which in turn may lead to differences in the mechanisms that mark septation sites and co-ordinate actin ring assembly with mitosis.…”

Section: Bud4 Has a General Role In Septum Formationmentioning

confidence: 99%

Morphogenetic and developmental functions of the Aspergillus nidulans homologues of the yeast bud site selection proteins Bud4 and Axl2

Rittenour

et al. 2012

Molecular Microbiology

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SummaryThe yeast bud site selection system represents a paradigm for understanding how fungal cells regulate the formation of a polarity axis. In Saccharomyces cerevisiae, Bud4 and Axl2 are components of the axial bud site marker. To address the possibility that these proteins regulate cellular morphogenesis in filamentous fungi, we have characterized homologues of Bud4 and Axl2 in Aspergillus nidulans. Our results show that Bud4 is involved in septum formation in both hyphae and developing conidiophores. Whereas Axl2 appears to have no obvious role in hyphal growth, it is required for the regulation of phialide morphogenesis during conidiation. In particular, Axl2 localizes to the phialide-spore junction, where it appears to promote the recruitment of septins. Furthermore, the developmental regulators BrlA and AbaA control the expression of Axl2. Additional studies indicate that Axl2 is also involved in the regulation of sexual development, not only in A. nidulans, but also in the phylogenetically unrelated fungus Fusarium graminearum. Our results suggest that Axl2 plays a key role in phialide morphogenesis and/or function during conidiation in the aspergilli.

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Section: Bud4 Has a General Role In Septum Formationmentioning

confidence: 99%

Morphogenetic and developmental functions of the Aspergillus nidulans homologues of the yeast bud site selection proteins Bud4 and Axl2

Rittenour

et al. 2012

Molecular Microbiology

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“…Staining with Calcofluor White and DAPI revealed that the bi-septate fragments and hyphal tips were multi-nucleate. In the synchronous model for mitosis, a wave of mitosis progresses from the nucleus closest to the tip so that sister nuclei located nearest the tip are of the same genotype (26). Branch formation and mitosis are also closely coordinated, and new branches acquire one or a few seed nuclei that subsequently undergo mitosis.…”

Section: Resultsmentioning

confidence: 99%

Isolation of Fungal Homokaryotic Lines from Heterokaryotic Transformants by Sonic Disruption of Mycelia

2010

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Fungal hyphae--and in some cases, spores--are multi-nucleate. During genetic transformation of these spores or mycelia, only one nucleus generally receives the transferred T-DNA generating heterokaryotic colonies. Characterization of genetic changes, such as the effects of gene disruption in the transformants, requires purified homokaryotic lines. Hyphal tip transfer has conventionally been used to isolate homokaryons. We developed an alternative method for purification of fungal homokaryons from transformed heterokaryotic lines of Sclerotinia sclerotiorum. Ultrasound pulses were used to generate bi-septate, unicellular hyphal fragments that regenerate under selection to produce homokaryotic lines that can be easily identified using colony PCR. This technique facilitates the purification of transformed lines, which allows for routine genome manipulation, and should be adaptable for other filamentous fungi.

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“…Since the Cdc13-Cdc2 single-chain CDK is expressed from the cdc13 promoter, it presumably retains both the transcriptional and translational regulation of Cdc13. Although tyrosine phosphorylation is a general mechanism for size control in fungal and metazoan somatic cells (Nurse, 1990;Harris, 2006), cyclin expression appears to regulate cell-division timing in many metazoan embryonic cells and in other eukaryotic domains, such as plants and ciliates (Minshull et al, 1989;Harashima et al, 2013). Therefore, Cdc13-Cdc2 cells may reveal a basal eukaryotic size control mechanism based on size-dependent cyclin expression that has been superseded by CDK tyrosine phosphorylation in fungi and metazoans.…”

Section: Discussionmentioning

confidence: 99%

The fission yeast S-phase cyclin Cig2 can drive mitosis

et al. 2020

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Commitment to mitosis is regulated by cyclin-dependent kinase (CDK) activity. In the fission yeast Schizosaccharomyces pombe, the major B-type cyclin, Cdc13, is necessary and sufficient to drive mitotic entry. Furthermore, Cdc13 is also sufficient to drive S phase, demonstrating that a single cyclin can regulate alternating rounds of replication and mitosis, and providing the foundation of the quantitative model of CDK function. It has been assumed that Cig2, a B-type cyclin expressed only during S phase and incapable of driving mitosis in wild-type cells, was specialized for S-phase regulation. Here, we show that Cig2 is capable of driving mitosis. Cig2/CDK activity drives mitotic catastrophe—lethal mitosis in inviably small cells—in cells that lack CDK inhibition by tyrosine-phosphorylation. Moreover, Cig2/CDK can drive mitosis in the absence of Cdc13/CDK activity and constitutive expression of Cig2 can rescue loss of Cdc13 activity. These results demonstrate that in fission yeast, not only can the presumptive M-phase cyclin drive S phase, but the presumptive S-phase cyclin can drive M phase, further supporting the quantitative model of CDK function. Furthermore, these results provide an explanation, previously proposed on the basis of computational analyses, for the surprising observation that cells expressing a single-chain Cdc13-Cdc2 CDK do not require Y15 phosphorylation for viability. Their viability is due to the fact that in such cells, which lack Cig2/CDK complexes, Cdc13/CDK activity is unable to drive mitotic catastrophe.

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Mitosis in Filamentous Fungi

Cited by 6 publications

References 94 publications

Morphogenetic and developmental functions of the Aspergillus nidulans homologues of the yeast bud site selection proteins Bud4 and Axl2

Morphogenetic and developmental functions of the Aspergillus nidulans homologues of the yeast bud site selection proteins Bud4 and Axl2

Isolation of Fungal Homokaryotic Lines from Heterokaryotic Transformants by Sonic Disruption of Mycelia

The fission yeast S-phase cyclin Cig2 can drive mitosis

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