Analysis of heterokaryon incompatibility between heterokaryon-compatibility (h-c) groups R and GL provides evidence that at least eight het loci control somatic incompatibility in Aspergillus nidulans

Anwar, M. M.; Croft, J. H.; Dales, R. B. G.

doi:10.1099/00221287-139-7-1599

Cited by 26 publications

(19 citation statements)

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“…Based on TINC's high sequence similarity to Het-C, 25 A. nidulans isolates representing 21 heterokaryon compatibility groups (1,7,8) were sequenced at the tinC locus to determine whether tinC was multiallelic and potentially involved in heterokaryon incompatibility reactions in Aspergillus (data not shown). This sequencing identified no significant sequence differences at the tinC locus, suggesting that TINC may not participate in heterokaryon compatibility determination in Aspergillus.…”

Section: Resultsmentioning

confidence: 99%

Potential Link between the NIMA Mitotic Kinase and Nuclear Membrane Fission during Mitotic Exit inAspergillus nidulans

et al. 2004

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We have isolated TINC as a NIMA-interacting protein by using the yeast two-hybrid system and have confirmed that TINC interacts with NIMA in Aspergillus nidulans. The TINC-NIMA interaction is stabilized in the absence of phosphatase inhibitors and in the presence of kinase-inactive NIMA, suggesting that the interaction is enhanced when NIMA is not fully activated. TINC is a cytoplasmic protein. TINC homologues and a TINC-like protein (A. nidulans HETC) are conserved in other filamentous fungi. Neither deletion of tinC nor deletion of both tinC and A. nidulans hetC is lethal, but deletion of tinC does produce cold sensitivity as well as osmotic sensitivity. Expression of an amino-terminal-truncated form of TINC (⌬N-TINC) inhibits colony growth in Aspergillus and localizes to membrane-like structures within the cell. Examination of cell cycle progression in these cells reveals that they progress through multiple defective mitoses. Many cells contain large polyploid single nuclei, while some appear to have separated masses of DNA. Examination of the nuclear envelopes of cells containing more than one DNA mass reveals that both DNA masses are contained within a single nuclear envelope, indicating that nuclear membrane fission is defective. The ability of these cells to separate DNA segregation from nuclear membrane fission suggests that this coordination is normally a regulated process in A. nidulans. Additional experiments demonstrate that expression of ⌬N-TINC results in premature NIMA disappearance in mitotic samples. We propose that TINC's interaction with NIMA and the cell cycle defects produced by ⌬N-TINC expression suggest possible roles for TINC and NIMA during nuclear membrane fission.Entry into mitosis represents the irreversible commitment by a cell to segregate duplicated DNA equally to form two independent nuclei. Entry into mitosis with damaged DNA or incompletely replicated DNA, failure to establish a proper bipolar spindle, and premature exit from mitosis can all have disastrous consequences for the cell. As such, entry into, progression through, and exit from mitosis are all highly regulated cell cycle transitions. In all eukaryotes, one of the central triggers for mitotic entry is the activation of the cyclin-dependent kinase CDC2 (12,21,30). In Aspergillus nidulans, the NIMA (never in mitosis A) kinase is also required for mitotic entry, as cells with active CDC2 and inactive NIMA are unable to enter mitosis (32).Two lines of evidence suggest that a NIMA pathway of cell cycle regulation exists in a wide range of organisms. Ectopic expression of NIMA in metazoan cells can induce some of the hallmarks of mitotic onset, including DNA condensation and germinal vesicle breakdown (25). Also, NIMA-related kinases (Nek) have been identified in a range of organisms, including yeast, flies, frogs, mice, and humans (29). Additionally, mitotic regulatory roles have been identified for the Fin1p kinase (15,16,22,23) from Schizosaccharomyces pombe as well as for a number of mammalian Nek kinases, including Nek2...

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Section: Resultsmentioning

confidence: 99%

Potential Link between the NIMA Mitotic Kinase and Nuclear Membrane Fission during Mitotic Exit inAspergillus nidulans

et al. 2004

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“…This vegetative compatibility system is dictated by a series of het loci whose alleles must all be identical for stable hyphal fusions to occur (Leslie, 1993). The number of het loci in A. parasiticus has not been determined, but in A. nidulans, a minimum of eight het loci are distributed over five linkage groups (Anwar et al, 1993). Vegetatively compatible individuals within populations are often grouped together into vegetative compatibility groups (VCGs) and provide a multilocus measure of genetic diversity (Horn and Greene, 1995).…”

Section: Relationship Between Sexual and Vegetative Compatibility Sysmentioning

confidence: 99%

Sexual reproduction and recombination in the aflatoxin-producing fungus Aspergillus parasiticus

Horn

Ramírez-Prado

Carbone

2009

Fungal Genetics and Biology

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“…Genetic dissection of vegetative incompatibility systems in ascomycetes has only been undertaken in a limited number of species, including Neurospora crassa (39,61,71), Podospora anserina (12,73), Aspergillus nidulans (4), and Cryphonectria parasitica (23). The number of het loci varies from one species to another (from 6 to 11 in the species mentioned above).…”

Section: What Is Heterokaryon Incompatibility?mentioning

confidence: 99%

Molecular Genetics of Heterokaryon Incompatibility in Filamentous Ascomycetes

Saupe

2000

Microbiol Mol Biol Rev

314

284

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SUMMARY Filamentous fungi spontaneously undergo vegetative cell fusion events within but also between individuals. These cell fusions (anastomoses) lead to cytoplasmic mixing and to the formation of vegetative heterokaryons (i.e., cells containing different nuclear types). The viability of these heterokaryons is genetically controlled by specific loci termed het loci (for heterokaryon incompatibility). Heterokaryotic cells formed between individuals of unlike het genotypes undergo a characteristic cell death reaction or else are severely inhibited in their growth. The biological significance of this phenomenon remains a puzzle. Heterokaryon incompatibility genes have been proposed to represent a vegetative self/nonself recognition system preventing heterokaryon formation between unlike individuals to limit horizontal transfer of cytoplasmic infectious elements. Molecular characterization of het genes and of genes participating in the incompatibility reaction has been achieved for two ascomycetes, Neurospora crassa and Podospora anserina. These analyses have shown that het genes are diverse in sequence and do not belong to a gene family and that at least some of them perform cellular functions in addition to their role in incompatibility. Divergence between the different allelic forms of a het gene is generally extensive, but single-amino-acid differences can be sufficient to trigger incompatibility. In some instances het gene evolution appears to be driven by positive selection, which suggests that the het genes indeed represent recognition systems. However, work on nonallelic incompatibility systems in P. anserina suggests that incompatibility might represent an accidental activation of a cellular system controlling adaptation to starvation.

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Analysis of heterokaryon incompatibility between heterokaryon-compatibility (h-c) groups R and GL provides evidence that at least eight het loci control somatic incompatibility in Aspergillus nidulans

Cited by 26 publications

References 11 publications

Potential Link between the NIMA Mitotic Kinase and Nuclear Membrane Fission during Mitotic Exit inAspergillus nidulans

Potential Link between the NIMA Mitotic Kinase and Nuclear Membrane Fission during Mitotic Exit inAspergillus nidulans

Sexual reproduction and recombination in the aflatoxin-producing fungus Aspergillus parasiticus

Molecular Genetics of Heterokaryon Incompatibility in Filamentous Ascomycetes

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