Genetic linkage map of Phaeosphaeria nodorum, the causal agent of stagonospora nodorum blotch disease of wheat

Malkus, Arkadiusz; Song, Qijian; Cregan, Perry B.; Arseniuk, E.; Ueng, Peter P.

doi:10.1007/s10658-009-9454-y

Cited by 8 publications

(5 citation statements)

References 29 publications

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“…Increasing intra-tetrad selfing also induces more heterozygosity and thus slightly reinforces the sheltering effect of the mating-type locus. This is consistent with the findings that, in fungi, ascomycetes that reproduce via outcrossing and live as haploids do not show evolutionary strata (Skinner et al, 1993, Zhong et al, 2002, Phan et al, 2003, Kuhn et al, 2006, Jin et al, 2007, Malkus et al, 2009) whereas pseudo-homothallic ascomycete fungi, living as dikaryotic and undergoing mostly intra-tetrad selfing, are those with evolutionary strata around their mating-type locus (Menkis et al, 2008, Hartmann, Duhamel, et al, 2021, Hartmann, Ament-Velásquez, et al, 2021, Vittorelli et al, 2022). In basidiomycetes also, the species with evolutionary strata are dikaryotic and automictic, e.g.…”

Section: Discussionsupporting

confidence: 91%

The fate of recessive deleterious or overdominant mutations near mating-type loci under partial selfing

Tezenas

Giraud

Véber

et al. 2022

Preprint

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Large regions of suppressed recombination having extended with time occur in many organisms around genes involved in mating compatibility (sex-determining or mating-type genes). The sheltering of deleterious alleles has been proposed to be involved in such expansions. However, the dynamics of deleterious mutations partially linked to genes involved in mating compatibility are not well understood, especially in finite populations. In particular, under what conditions deleterious mutations are likely to be maintained for long enough near mating-compatibility genes remains to be evaluated, especially under selfing, which generally increases the purging rate of deleterious mutations. Using a branching process approximation, we studied the fate of a new deleterious or overdominant mutation in a diploid population, considering a locus carrying two permanently heterozygous mating-type alleles, and a partially linked locus at which the mutation appears. We obtained analytical and numerical results on the probability and purging time of the new mutation. We investigated the impact of recombination between the two loci and of the mating system (outcrossing, intra and inter-tetrad selfing) on the maintenance of the mutation. We found that the presence of a mating-type locus always sheltered the mutation under selfing, i.e. it decreased the purging probability and increased the purging time of the mutations. The sheltering effect was higher in case of automixis (intra-tetrad selfing). This may contribute to explain why evolutionary strata of recombination suppression near the mating-type locus are found mostly in automictic (pseudo-homothallic) fungi. We also showed that rare events of deleterious mutation maintenance during strikingly long evolutionary times could occur, suggesting that deleterious mutations can indeed accumulate near the mating-type locus over evolutionary time scales. In conclusion, our results show that, although selfing purges deleterious mutations, these mutations can be maintained for very long times near a mating-type locus, which may contribute to promote the evolution of recombination suppression in sex-related chromosomes.

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Section: Discussionsupporting

confidence: 91%

The fate of recessive deleterious or overdominant mutations near mating-type loci under partial selfing

Tezenas

Giraud

Véber

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…Increasing intra-tetrad selfing also induces more heterozygosity and thus slightly reinforces the sheltering effect of the mating-type locus. This is consistent with the findings that, in fungi, ascomycetes that reproduce via outcrossing and live as haploids do not show evolutionary strata (Skinner et al, 1993, Zhong et al, 2002, Phan et al, 2003, Kuhn et al, 2006, Jin et al, 2007, Malkus et al, 2009 whereas pseudo-homothallic ascomycete fungi, living as dikaryotic and undergoing mostly intra-tetrad selfing, are those with evolutionary strata around their mating-type locus (Menkis et al, 2008, Hartmann, Duhamel, et al, 2021, Hartmann, Ament-Velásquez, et al, 2021, Vittorelli et al, 2023. In basidiomycetes also, the species with evolutionary strata are dikaryotic and automictic, e.g.…”

Section: The Presence Of the Mating-type Locus Has A Sheltering Effec...supporting

confidence: 90%

The fate of recessive deleterious or overdominant mutations near mating-type loci under partial selfing

Tezenas¹,

Giraud²,

Véber³

et al. 2023

Peer Community Journal

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Large regions of suppressed recombination having extended over time occur in many organisms around genes involved in mating compatibility (sex-determining or mating-type genes). The sheltering of deleterious alleles has been proposed to be involved in such expansions. However, the dynamics of deleterious mutations partially linked to genes involved in mating compatibility are not well understood, especially in finite populations. In particular, under what conditions deleterious mutations are likely to be maintained for long enough near mating-compatibility genes remains to be evaluated, especially under selfing, which generally increases the purging rate of deleterious mutations. Using a branching process approximation, we studied the fate of a new deleterious or overdominant mutation in a diploid population, considering a locus carrying two permanently heterozygous mating-type alleles, and a partially linked locus at which the mutation appears. We obtained analytical and numerical results on the probability and purging time of the new mutation. We investigated the impact of recombination between the two loci and of the mating system (outcrossing, intra and inter-tetrad selfing) on the maintenance of the mutation. We found that the presence of a fungal-like mating-type locus (i.e. not preventing diploid selfing) always sheltered the mutation under selfing, i.e. it decreased the purging probability and increased the purging time of the mutations. The sheltering effect was higher in case of automixis (intra-tetrad selfing). This may contribute to explain why evolutionary strata of recombination suppression near the mating-type locus are found mostly in automictic (pseudo-homothallic) fungi. We also showed that rare events of deleterious mutation maintenance during strikingly long evolutionary times could occur, suggesting that deleterious mutations can indeed accumulate near the mating-type locus over evolutionary time scales. In conclusion, our results show that, although selfing purges deleterious mutations, these mutations can be maintained for very long times near a mating-type locus, which may contribute to promote the evolution of recombination suppression in sex-related chromosomes.

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“…In S. nodorum strain-to-strain SGA sometime comprised entire scaffolds. Pulsed field gel and genetic mapping evidence suggests that there are about 20 chromosomes in S. nodorum (Cooley and Caten 1991; Malkus et al 2009), whereas the SN15 assembly contains 107 scaffolds. The lack of a finished SN15 genome assembly means that it is not currently possible to determine the chromosomal location of the SGA regions.…”

Section: Discussionmentioning

confidence: 99%

Resequencing and Comparative Genomics of Stagonospora nodorum: Sectional Gene Absence and Effector Discovery

Syme

Hane

Friesen

et al. 2013

G3 Genes|Genomes|Genetics

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Stagonospora nodorum is an important wheat (Triticum aestivum) pathogen in many parts of the world, causing major yield losses. It was the first species in the large fungal Dothideomycete class to be genome sequenced. The reference genome sequence (SN15) has been instrumental in the discovery of genes encoding necrotrophic effectors that induce disease symptoms in specific host genotypes. Here we present the genome sequence of two further S. nodorum strains (Sn4 and Sn79) that differ in their effector repertoire from the reference. Sn79 is avirulent on wheat and produces no apparent effectors when infiltrated onto many cultivars and mapping population parents. Sn4 is pathogenic on wheat and has virulences not found in SN15. The new strains, sequenced with short-read Illumina chemistry, are compared with SN15 by a combination of mapping and de novo assembly approaches. Each of the genomes contains a large number of strain-specific genes, many of which have no meaningful similarity to any known gene. Large contiguous sections of the reference genome are absent in the two newly sequenced strains. We refer to these differences as “sectional gene absences.” The presence of genes in pathogenic strains and absence in Sn79 is added to computationally predicted properties of known proteins to produce a list of likely effector candidates. Transposon insertion was observed in the mitochondrial genomes of virulent strains where the avirulent strain retained the likely ancestral sequence. The study suggests that short-read enabled comparative genomics is an effective way to both identify new S. nodorum effector candidates and to illuminate evolutionary processes in this species.

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Genetic linkage map of Phaeosphaeria nodorum, the causal agent of stagonospora nodorum blotch disease of wheat

Cited by 8 publications

References 29 publications

The fate of recessive deleterious or overdominant mutations near mating-type loci under partial selfing

The fate of recessive deleterious or overdominant mutations near mating-type loci under partial selfing

The fate of recessive deleterious or overdominant mutations near mating-type loci under partial selfing

Resequencing and Comparative Genomics of Stagonospora nodorum: Sectional Gene Absence and Effector Discovery

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