When yeast cells meet, karyogamy!

Gibeaux, Romain; Knop, Michael

doi:10.4161/nucl.25021

Cited by 17 publications

(10 citation statements)

References 54 publications

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“…Mating requires the sequential processes of shmooing (polarized growth toward the mating partner), adhesion, cell wall degradation, cell fusion, nuclear congression, and nuclear fusion (karyogamy; reviewed in Ydenberg and Rose 2008 ; Merlini et al 2013 ). Nuclei congress along microtubules that emanate from the half-bridge adjacent to the spindle pole body (SPB) of each nucleus (congression; reviewed in Gibeaux and Knop 2013 ). The nuclear envelope comprises an outer nuclear membrane (ONM) that is continuous with the endoplasmic reticulum (ER), a lumenal space, and an inner nuclear membrane (INM).…”

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Kar5p Is Required for Multiple Functions in Both Inner and Outer Nuclear Envelope Fusion in Saccharomyces cerevisiae

Rogers

Rose

2015

G3 Genes|Genomes|Genetics

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During mating in the budding yeast Saccharomyces cerevisiae, two haploid nuclei fuse via two sequential membrane fusion steps. SNAREs (i.e., soluble N-ethylmaleimide–sensitive factor attachment protein receptors) and Prm3p mediate outer nuclear membrane fusion, but the inner membrane fusogen remains unknown. Kar5p is a highly conserved transmembrane protein that localizes adjacent to the spindle pole body (SPB), mediates nuclear envelope fusion, and recruits Prm3p adjacent to the SPB. To separate Kar5p’s functions, we tested localization, Prm3p recruitment, and nuclear fusion efficiency in various kar5 mutants. All domains and the conserved cysteine residues were essential for nuclear fusion. Several kar5 mutant proteins localized properly but did not mediate Prm3p recruitment; other kar5 mutant proteins localized and recruited Prm3p but were nevertheless defective for nuclear fusion, demonstrating additional functions beyond Prm3p recruitment. We identified one Kar5p domain required for SPB localization, which is dependent on the half-bridge protein Mps3p. Electron microscopy revealed a kar5 mutant that arrests with expanded nuclear envelope bridges, suggesting that Kar5p is required after outer nuclear envelope fusion. Finally, a split-GFP assay demonstrated that Kar5p localizes to both the inner and outer nuclear envelope. These insights suggest a mechanism by which Kar5p mediates inner nuclear membrane fusion.

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confidence: 99%

Kar5p Is Required for Multiple Functions in Both Inner and Outer Nuclear Envelope Fusion in Saccharomyces cerevisiae

Rogers

Rose

2015

G3 Genes|Genomes|Genetics

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“…In S. cerevisiae, Kar4 is a transcription factor that activates transcription of the microtubule minus end directed kinesin motor protein Kar3. Kar3 provides the force for nuclear congression during mating [73,74]. Ashbya mutants in KAR3 and KAR4 show only mild growth defects, yet strong sporulation defects.…”

Section: The Gear-box Of Sporulationmentioning

confidence: 99%

“…J. Fungi 2020, 6, x FOR PEER REVIEW 7 of 14 [73,74]. Ashbya mutants in KAR3 and KAR4 show only mild growth defects, yet strong sporulation defects.…”

Section: The Gear-box Of Sporulationmentioning

confidence: 99%

Sporulation in Ashbya gossypii

Wendland

2020

JoF

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Ashbya gossypii is a filamentous ascomycete belonging to the yeast family of Saccharomycetaceae. At the end of its growth phase Ashbya generates abundant amounts of riboflavin and spores that form within sporangia derived from fragmented cellular compartments of hyphae. The length of spores differs within species of the genus. Needle-shaped Ashbya spores aggregate via terminal filaments. A. gossypii is a homothallic fungus which may possess a and α mating types. However, the solo-MATa type strain is self-fertile and sporulates abundantly apparently without the need of prior mating. The central components required for the regulation of sporulation, encoded by IME1, IME2, IME4, KAR4, are conserved with Saccharomyces cerevisiae. Nutrient depletion generates a strong positive signal for sporulation via the cAMP-PKA pathway and SOK2, which is also essential for sporulation. Strong inhibitors of sporulation besides mutations in the central regulatory genes are the addition of exogenous cAMP or the overexpression of the mating type gene MATα2. Sporulation has been dissected using gene-function analyses and global RNA-seq transcriptomics. This revealed a role of Msn2/4, another potential PKA-target, for spore wall formation and a key dual role of the protein A kinase Tpk2 at the onset of sporulation as well as for breaking the dormancy of spores to initiate germination. Recent work has provided an overview of ascus development, regulation of sporulation and spore maturation. This will be summarized in the current review with a focus on the central regulatory genes. Current research and open questions will also be discussed.

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“…Nuclear fusion, however, requires the coordinated fusion of two membranes: the ONM and the INM. In yeast, nuclear fusion, also known as karyogamy, occurs as part of the mating process between cells of opposite mating type (for review, see Gibeaux and Knop, ). As described earlier, during mating, cells adhere to one another at the shmoo tip via agglutinins, at which point the cell walls break down, the plasma membranes come into contact and the cells fuse, forming a zygote (Fig.…”

Section: Nuclear Fusion During Mating: the Two‐membrane Challengementioning

confidence: 99%

The Malleable Nature of the Budding Yeast Nuclear Envelope: Flares, Fusion, and Fenestrations

Meseroll

Cohen-Fix

2016

J. Cell. Physiol.

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In eukaryotes, the nuclear envelope (NE) physically separates nuclear components and activities from rest of the cell. The NE also provides rigidity to the nucleus and contributes to chromosome organization. At the same time, the NE is highly dynamic; it must change shape and rearrange its components during development and throughout the cell cycle, and its morphology can be altered in response to mutation and disease. Here we focus on the NE of budding yeast, Saccharomyces cerevisiae, which has several unique features: it remains intact throughout the cell cycle, expands symmetrically during interphase, elongates during mitosis and, expands asymmetrically during mitotic delay. Moreover, its NE is safely breached during mating and when large structures, such as nuclear pore complexes and the spindle pole body, are embedded into its double membrane. The budding yeast NE lacks lamins and yet the nucleus is capable of maintaining a spherical shape throughout interphase. Despite these eccentricities, studies of the budding yeast NE have uncovered interesting, and likely conserved, processes that contribute to NE dynamics. In particular, we discuss the processes that drive and enable NE expansion and the dramatic changes in the NE that lead to extensions and fenestrations.

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When yeast cells meet, karyogamy!

Cited by 17 publications

References 54 publications

Kar5p Is Required for Multiple Functions in Both Inner and Outer Nuclear Envelope Fusion in Saccharomyces cerevisiae

Kar5p Is Required for Multiple Functions in Both Inner and Outer Nuclear Envelope Fusion in Saccharomyces cerevisiae

Sporulation in Ashbya gossypii

The Malleable Nature of the Budding Yeast Nuclear Envelope: Flares, Fusion, and Fenestrations

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