雌雄同型の、ホモタリックな

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/12/16 13:07:48」(JST)

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Homothallic refers to the possession, within a single organism, of the resources to reproduce sexually^[1] i. e having male and female reproductive structures on the same thallus. The opposite sexual functions are performed by different cells of a single mycelium.^[2]

It can be contrasted to heterothallic.

It is often used to categorize fungi. In yeast, heterothallic cells have mating types a and α. An experienced mother cell (one that has divided at least once) will switch mating type every cell division cycle because of the HO allele.

Sexual reproduction commonly occurs in two fundamentally different ways in fungi. These are outcrossing (in heterothallic fungi) in which two different individuals contribute nuclei to form a zygote, and self-fertilization or selfing (in homothallic fungi) in which both nuclei are derived from the same individual.

Among the 250 known species of aspergilli, about 36% have an identified sexual state.^[2] Among those Aspergillus species for which a sexual cycle has been observed, the majority in nature are homothallic (self-fertilizing).^[2] Selfing in the homothallic fungus Aspergillus nidulans involves activation of the same mating pathways characteristic of sex in outcrossing species, i.e. self-fertilization does not bypass required pathways for outcrossing sex but instead requires activation of these pathways within a single individual.^[3] Fusion of haploid nuclei occurs within reproductive structures termed cleistothecia, in which the diploid zygote undergoes meiotic divisions to yield haploid ascospores.

A lichen is a composite organism consisting of a fungus and a photosynthetic partner that are growing together in a symbiotic relationship. The photosynthetic partner is usually either a green alga or a cyanobacterium. Lichens occur in some of the most extreme environments on Earth—arctic tundra, hot deserts, rocky coasts, and toxic slag heaps. Most lichenized fungi produce abundant sexual structures and in many species sexual spores appear to be the only means of dispersal (Murtagh et al., 2000). The lichens Graphis scripta and Ochrolechia parella do not produce symbiotic vegetative propagules. Rather the lichen-forming fungi of these species reproduce sexually by self-fertilization (i.e. they are homothallic), and it was proposed that this breeding system allows successful reproduction in harsh environments.^[4] (Murtagh et al., 2000). Homothallism appears to be common in natural populations of fungi. Although self-fertilization employs meiosis, it produces minimal genetic variability. Homothallism is thus a form of sex that is unlikely to be adaptively maintained by a benefit related to producing variability. However, homothallic meiosis may be maintained in fungi as an adaptation for surviving stressful conditions; a proposed benefit of meiosis is the promoted homologous meiotic recombinational repair of DNA damages that are ordinarily caused by a stressful environment.^[5]

References

^ "On-Line Glossary: H". Retrieved 2008-10-24.
^ ^a ^b Dyer PS, O'Gorman CM (January 2012). "Sexual development and cryptic sexuality in fungi: insights from Aspergillus species". FEMS Microbiol. Rev. 36 (1): 165–92. doi:10.1111/j.1574-6976.2011.00308.x. PMID 22091779.
^ Paoletti M, Seymour FA, Alcocer MJ, Kaur N, Calvo AM, Archer DB, Dyer PS (August 2007). "Mating type and the genetic basis of self-fertility in the model fungus Aspergillus nidulans". Curr. Biol. 17 (16): 1384–9. doi:10.1016/j.cub.2007.07.012. PMID 17669651.
^ Murtagh GJ, Dyer PS, Crittenden PD (April 2000). "Sex and the single lichen". Nature 404 (6778): 564. doi:10.1038/35007142. PMID 10766229.
^ Bernstein H and Bernstein C (2013). Evolutionary Origin and Adaptive Function of Meiosis. In Meiosis: Bernstein C and Bernstein H, editors. ISBN 978-953-51-1197-9, InTech, http://www.intechopen.com/books/meiosis/evolutionary-origin-and-adaptive-function-of-meiosis

External links

4 Growth and Life Cycles (of Yeast)
thefreedictionary.com

English Journal

Genetics of mating in members of the Chaetomiaceae as revealed by experimental and genomic characterization of reproduction in Myceliophthora heterothallica.

Hutchinson MI1, Powell AJ2, Tsang A3, O'Toole N3, Berka RM4, Barry K5, Grigoriev IV5, Natvig DO6.
Fungal genetics and biology : FG & B.Fungal Genet Biol.2015 Nov 30;86:9-19. doi: 10.1016/j.fgb.2015.11.007. [Epub ahead of print]
Members of the Chaetomiaceae are among the most studied fungi in industry and among the most reported in investigations of biomass degradation in both natural and laboratory settings. The family is recognized for production of carbohydrate-active enzymes and antibiotics. Thermophilic species are of
PMID 26608618

A Large-Scale Functional Analysis of Putative Target Genes of Mating-Type Loci Provides Insight into the Regulation of Sexual Development of the Cereal Pathogen Fusarium graminearum.

Kim HK1, Jo SM1, Kim GY1, Kim DW1, Kim YK2, Yun SH1.
PLoS genetics.PLoS Genet.2015 Sep 3;11(9):e1005486. doi: 10.1371/journal.pgen.1005486. eCollection 2015.
Fusarium graminearum, the causal agent of Fusarium head blight in cereal crops, produces sexual progeny (ascospore) as an important overwintering and dissemination strategy for completing the disease cycle. This homothallic ascomycetous species does not require a partner for sexual mating; instead,
PMID 26334536

Characterization and distribution of mating-type genes of the turfgrass pathogen Sclerotinia homoeocarpa on a global scale.

Putman AI1, Tredway LP2, Carbone I3.
Fungal genetics and biology : FG & B.Fungal Genet Biol.2015 Aug;81:25-40. doi: 10.1016/j.fgb.2015.05.012. Epub 2015 Jun 3.
Sclerotinia homoeocarpa F.T. Bennett is a filamentous member of Ascomycota that causes dollar spot, the most economically important disease of turfgrass worldwide. We sequenced and characterized the mating-type (MAT) locus of four recently-collected contemporary strains causing dollar spot, four his
PMID 26049125

Japanese Journal

Potent L-lactic acid assimilation of the fermentative and heterothallic haploid yeast Saccharomyces cerevisiae NAM34-4C(ENVIRONMENTAL BIOTECHNOLOGY)

Journal of bioscience and bioengineering 117(1), 65-70, 2014-01
NAID 110009766606

Distribution of the Sex-Determining Gene MID and Molecular Correspondence of Mating Types within the Isogamous Genus Gonium (Volvocales, Chlorophyta).