Geographic Distribution of Neurospora Spore Killer Strains and Strains Resistant to Killing

Turner, Barbara C.

doi:10.1006/fgbi.2001.1253

Cited by 38 publications

(50 citation statements)

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“…Their loci can only be defined as a 30-map unit region because recombination is blocked between Spore killers and WT within this interval (9). Nonkiller strains that are resistant to spore killing have been found in nature (5,(9)(10)(11). Because recombination block is not observed between WT and a resistant strain, the associated resistance gene can be mapped accurately.…”

mentioning

confidence: 99%

Molecular dissection of Neurospora Spore killer meiotic drive elements

Hammond

Rehard

Xiao

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Meiotic drive is a non-Mendelian inheritance phenomenon in which certain selfish genetic elements skew sexual transmission in their own favor. In some cases, progeny or gametes carrying a meiotic drive element can survive preferentially because it causes the death or malfunctioning of those that do not carry it. In Neurospora, meiotic drive can be observed in fungal spore killing. In a cross of Spore killer (Sk) × WT (Sk-sensitive), the ascospores containing the Spore killer allele survive, whereas the ones with the sensitive allele degenerate. Sk-2 and Sk-3 are the most studied meiotic drive elements in Neurospora, and they each theoretically contain two essential components: a killer element and a resistance gene. Here we report the identification and characterization of the Sk resistance gene, rsk (resistant to Spore killer). rsk seems to be a fungal-specific gene, and its deletion in a killer strain leads to self-killing. Sk-2, Sk-3, and naturally resistant isolates all use rsk for resistance. In each killer system, rsk sequences from an Sk strain and a resistant isolate are highly similar, suggesting that they share the same origin. Sk-2, Sk-3, and sensitive rsk alleles differ from each other by their unique indel patterns. Contrary to long-held belief, the killer targets not only late but also early ascospore development. The WT RSK protein is dispensable for ascospore production and is not a target of the spore-killing mechanism. Rather, a resistant version of RSK likely neutralizes the killer element and prevents it from interfering with ascospore development.intragenomic conflict | segregation distortion | selfish elements I n fungi, plants, and animals, not all genes follow the Mendelian pattern of inheritance. Meiotic drive, sometimes referred to as segregation distortion, describes the phenomenon in which certain "cheating" alleles are recovered in more than half of the progeny (1). Two well-known examples are the segregation distorter (SD) in Drosophila and the t haplotype in Mus. In these cases, sperm not carrying the aggressive allele (the drive element) either degenerate (in flies) or become functionally impaired (in mice) (2, 3). In fungi, meiotic drive can be observed as spore killing, in which ascospores (sexual spores) that carry the "Spore killer" element survive preferentially (4). Examples of spore killing can be found in Neurospora sitophila, Neurospora intermedia, Podospora anserina, Gibberella fujikuroi, and Cochliobolus heterostrophus.Spore killer-2 (Sk-2) and Spore killer-3 (Sk-3), which behave similarly, are the most studied distortion elements in Neurospora (5). Originally discovered in N. intermedia, the two spore-killing factors have been introgressed into Neurospora crassa for extensive genetic studies. In a Spore killer (Sk) × WT (Sk-sensitive or Sk S ) cross, regardless of which acts as the female, the four Skcontaining spores are black (B) and viable, whereas the four Sksensitive spores are white (W) and inviable. Manifestation of killing does not occur until late ascospore de...

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confidence: 99%

Molecular dissection of Neurospora Spore killer meiotic drive elements

Hammond

Rehard

Xiao

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…The molecular mechanisms of meiotic drive remain largely elusive, except in the case of SD in Drosophila, where distortion involves a truncated form of a RanGAP protein and its mislocalization to the nucleus (2). The best studied examples of segregation distortion in fungi are the spore killer systems in the ascomycetes Neurospora crassa (3)(4)(5)(6) and Podospora anserina (7). In these haploid organisms, the sexual progeny, the ascospores, are linearly arranged after meiosis.…”

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confidence: 99%

Sexual transmission of the [Het-s] prion leads to meiotic drive in Podospora anserina

Dalstra

Swart²,

Debets³

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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In the filamentous fungus Podospora anserina, two phenomena are associated with polymorphism at the het-s locus, vegetative incompatibility and ascospore abortion. Two het-s alleles occur naturally, het-s and het-S. The het-s encoded protein is a prion propagating as a self-perpetuating amyloid aggregate. M eiotic drive is a process mediated by genetic elements, called segregation distorters, that actively bias Mendelian segregation in their favor. In metazoans, classic examples of meiotic drive include the t haplotype in mice and Segregation Distorter (SD) in Drosophila (1). In both these autosomal drive systems, heterozygous males produce gametes of the driver genotype in excess. The molecular mechanisms of meiotic drive remain largely elusive, except in the case of SD in Drosophila, where distortion involves a truncated form of a RanGAP protein and its mislocalization to the nucleus (2). The best studied examples of segregation distortion in fungi are the spore killer systems in the ascomycetes Neurospora crassa (3-6) and Podospora anserina (7). In these haploid organisms, the sexual progeny, the ascospores, are linearly arranged after meiosis. Ascomycetes therefore provide excellent opportunities to investigate the behavior of meiotic drive elements (8). Presence of a killer gene can readily be detected by directly analyzing the pattern of ascospore abortion. Spore killer genes exist as a killer and a sensitive allele or haplotype. In a killer ϫ sensitive cross, the ascospores harboring only the sensitive genotype degenerate. Heterokaryotic spores, containing both a sensitive and a killer nucleus, escape abortion. Both in Neurospora and in Podospora, several spore killer loci have been genetically identified, but so far the mechanism of spore killing is unknown.In 1965, Bernet (9, 10) described properties of the het-s gene in Podospora, now recognized to be analogous to a spore killer locus. The discovery that het-s encodes a prion protein (11, 12) places this observation into a new perspective. The het-s locus, together with at least eight other loci, determines vegetative incompatibility in P. anserina (13,14). Two alleles are found at this locus, termed het-s During the sexual cycle, a single mating-type culture of P. anserina differentiates both male (microconidia) and female (protoperithecia) reproductive structures. The protoperithecium emits a specialized hypha called the trichogyne. Fertilization occurs when a microconidium fuses with a trichogyne of opposite mating type. After migration of the male nucleus down the trichogyne into the female ascogonium, individualized male and female nuclei divide synchronously in a syncytial structure. Because the male gamete contributes very little cytoplasm to this heterokaryon, the cytoplasm of the zygote is essentially of maternal origin. Nuclei of opposite mating type then pair up, and karyogamy takes place in specialized cells. Importantly, at this stage there is a transition from a syncytial to a cellular state (21). Meiotic progeny are linearly arranged as ...

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“…In individual asci, these elements kill sibling ascospores that do not carry them, leading to segregation distortion similar to meiotic drive elements in Drosophila, but more accessible to experimental work. Studies on the geographic distribution, heterogeneity, cytology, and suppression of meiotic gene silencing by Sk elements have preoccupied the laboratory for .30 years (Turner 2001;Raju 2002).…”

Section: A Man a Model A Missionmentioning

confidence: 99%

Tending Neurospora: David Perkins, 1919–2007, and Dorothy Newmeyer Perkins, 1922–2007

Davis

2007

Genetics

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Geographic Distribution of Neurospora Spore Killer Strains and Strains Resistant to Killing

Cited by 38 publications

References 30 publications

Molecular dissection of Neurospora Spore killer meiotic drive elements

Molecular dissection of Neurospora Spore killer meiotic drive elements

Sexual transmission of the [Het-s] prion leads to meiotic drive in Podospora anserina

Tending Neurospora: David Perkins, 1919–2007, and Dorothy Newmeyer Perkins, 1922–2007

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