Genetic exchange between diploid and haploid mycelia of Armillaria gallica

Carvalho, Daisy; Smith, Myron L.; Anderson, James B.

doi:10.1016/s0953-7562(09)80520-0

Cited by 34 publications

(36 citation statements)

References 41 publications

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“…For one of these recombinant diploids, Napa187 ϫ R1PT3, its recombinant status was further evidenced by the absence of one allele from the diploid partner at two nuclear loci (185 at Am36 and 236 at Am59). The fact that all triploids and recombinant diploids had the same ATP6 haplotype as the haploid transformant (Arm2a) in all diploid-haploid matings is consistent with the typical pattern of mitochondrial inheritance from the haploid partner in diploid-haploid matings of Armillaria (12).…”

Section: Resultssupporting

confidence: 78%

“…The absence of such nuclear displacement in our study is expected because a mycelium with only the nucleus of the wild-type diploid would have died under hygromycin selection. It is possible that recombinant diploids form in a process analogous to parasexual recombination, in which the nucleus from the diploid partner first haploidizes and one of two resulting haploid nuclei fuses with the nucleus from the haploid partner (12). Among recombinant diploid strains, our findings of the presence of all nuclear markers from the haploid parent and only some nuclear markers from the diploid parent support this hypothesis for the generation of recombinant diploids.…”

Section: Discussionsupporting

confidence: 67%

“…Less frequently, the synthesized mycelium was recombinant and diploid, as characterized by hygromycin resistance, the presence of some but not all nuclear markers from both partners, the mitochondrial haplotype of the haploid partner, uninucleate hyphae, and diploid morphology. These patterns of nuclear inheritance are rare in laboratory matings of Armillaria compared to the common displacement of the haploid nucleus by the diploid nucleus (12,40). The absence of such nuclear displacement in our study is expected because a mycelium with only the nucleus of the wild-type diploid would have died under hygromycin selection.…”

Section: Discussionmentioning

confidence: 56%

“…Diploid and haploid mycelia can mate to form a recombinant diploid mycelium (12), although the mechanism by which this occurs is not known. Nonetheless, evidence of somatic recombination in natural populations of Armillaria (4,37) and the existence of this mode of reproduction in nature suggest that this process may be important in the pathogen's ecology.…”

mentioning

confidence: 99%

“…In diploid-haploid matings of Armillaria in the laboratory, the diploid nucleus often displaces the haploid nucleus; recombinant mycelia are uncommon (12,40). Our aim was to increase their frequency, as a study tool to examine the mechanism and adaptive consequences of somatic recombination.…”

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confidence: 99%

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Agrobacterium tumefaciens -Mediated Transformation for Investigation of Somatic Recombination in the Fungal Pathogen Armillaria mellea

Baumgartner

Fujiyoshi

Foster

et al. 2010

Appl Environ Microbiol

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Armillaria root disease is one of the most damaging timber and fruit tree diseases in the world. Despite its economic importance, many basic questions about the biology of the causal fungi, Armillaria spp., are unanswered. For example, Armillaria undergoes matings between diploid and haploid mycelia, which can result in a recombinant diploid without meiosis. Evidence of such somatic recombination in natural populations suggests that this reproductive mode may affect the pathogen's ecology. Investigations of the mechanisms and adaptive consequences of somatic recombination are, however, hampered by the lack of a method to reliably synthesize somatic recombinants. Here we report the first genetic transformation system for the genus Armillaria. We transformed A. mellea with selective markers for use in diploid-haploid matings to reliably synthesize somatic recombinants. This was accomplished with Agrobacterium tumefaciens carrying pBGgHg, which carries the hygromycin phosphotransferase gene (hph). hph was integrated into transformants, as evidenced by serial transfer to selective media, PCR, reverse transcription-PCR (RT-PCR), and Southern hybridization. Nuclear and mitochondrial markers were developed to genotype synthesized mycelia. In matings between a wild-type diploid and hygromycin-resistant haploids (transgenic), we identified recombinant, hygromycin-resistant diploids and, additionally, hygromycin-resistant triploids, all with the mitochondrial haplotype of the haploid partner. Our approach created no mycelium in which the haploid nucleus was replaced by the diploid nucleus, the typical outcome of diploid-haploid matings in Armillaria. This genetic transformation system, in combination with new markers to track chromosomal and cytoplasmic inheritance in A. mellea, will advance research aimed at characterizing the significance of somatic recombination in the ecology of this important fungus.Fungi have evolved various mechanisms of shuffling genetic material, which can occur in the absence of fruiting and meiosis. Among homobasidiomycetes in which the predominant vegetative stage is dikaryotic (e.g., Schizophyllum commune), the two nuclei per cell of a dikaryotic mycelium can exchange DNA within the mycelium to create a new dikaryotic genotype independent of basidiome formation (15). A dikaryotic mycelium can also mate with a monokaryon, the latter originating from a single spore, and subsequent nuclear migration of one of the dikaryon's two nuclei into the monokaryotic mycelium can create a new dikaryotic genotype (e.g., Heterobasidion annosum [44]). Such examples of somatic recombination/reassortment were concomitant with successful phenotypic adaptations for the new dikaryons, namely, improved tolerance of extreme environments.In the homobasidiomycete Armillaria mellea (the causal agent of Armillaria root disease), the predominant vegetative stage is diploid. Diploid and haploid mycelia can mate to form a recombinant diploid mycelium (12), although the mechanism by which this occurs is not known. Nonethele...

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Section: Resultssupporting

confidence: 78%

Section: Discussionsupporting

confidence: 67%

Section: Discussionmentioning

confidence: 56%

mentioning

confidence: 99%

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confidence: 99%

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