Mating type

Last updated

Mating types are the microorganism equivalent to sexes in multicellular lifeforms and are thought to be the ancestor to distinct sexes. They also occur in multicellular organisms such as fungi.

Contents

Definition

Mating types are the microorganism equivalent to sex in higher organisms [1] and occur in isogamous species. [2] Depending on the group, different mating types are often referred to by numbers, letters, or simply "+" and "−" instead of "male" and "female", which refer to "sexes" or differences in size between gametes. [1] Syngamy can only take place between gametes carrying different mating types.

Mating types are extensively studied in fungi. Among fungi, mating type is determined by chromosomal regions called mating-type loci. Furthermore, it is not as simple as "two different mating types can mate", but rather, a matter of combinatorics. As a simple example, most basidiomycete have a "tetrapolar heterothallism" mating system: there are two loci, and mating between two individuals is possible if the alleles on both loci are different. For example, if there are 3 alleles per locus, then there would be 9 mating types, each of which can mate with 4 other mating types. [3] By multiplicative combination, it generates a vast number of mating types.

Mechanism

As an illustration, the model organism Coprinus cinereus has two mating-type loci called A and B. Both loci have 3 groups of genes. At the A locus are 6 homeodomain proteins arranged in 3 groups of 2 (HD1 and HD2), which arose by gene duplication. At the B locus, each of the 3 groups contain one pheromone G-protein-coupled receptor and usually two genes for pheromones.

The A locus ensures heterothallism through a specific interaction between HD1 and HD2 proteins. Within each group, a HD1 protein can only form a functional heterodimer with a HD2 protein from a different group, not with the HD2 protein from its own group. Functional heterodimers are necessary for a dikaryon-specific transcription factor, and its lack arrests the development process. They function redundantly, so it is only necessary for one of the three groups to be heterozygotic for the A locus to work. [4]

Similarly, the B locus ensures heterothallism through a specific interaction between pheromone receptors and pheromones. Each pheromone receptor is activated by pheromones from other groups, but not by the pheromone encoded by the same group. This means that a pheromone receptor can only trigger a signaling cascade when it binds to a pheromone from a different group, not when it binds to the pheromone from its own group. They also function redundantly. [4]

In both cases, the mechanism is based on a "self-incompatibility" principle, where the proteins or pheromones from the same group are incompatible with each other, but compatible with those from different groups. [5] [6]

Similarly, the Schizophyllum commune has 2 gene groups (Aα, Aβ) for homeodomain proteins on the A locus, and 2 gene groups (Bα, Bβ) for pheromones and receptors on the B locus. Aα has 9 alleles, Aβ has 32, Bα has 9, and Bβ has 9. The two gene groups at the A locus function independently but redundantly, so only one group out of the two needs to be heterozygotic for it to work. Similarly for the two gene groups at the B locus. Thus, mating between two individuals succeeds if

Thus there are mating types, each of which can mate with other mating types. [7]

Occurrence

Reproduction by mating types is especially prevalent in fungi. Filamentous ascomycetes usually have two mating types referred to as "MAT1-1" and "MAT1-2", following the yeast mating-type locus (MAT). [8] Under standard nomenclature, MAT1-1 (which may informally be called MAT1) encodes for a regulatory protein with an alpha box motif, while MAT1-2 (informally called MAT2) encodes for a protein with a high motility-group (HMG) DNA-binding motif, as in the yeast mating type MATα1. [9] The corresponding mating types in yeast, a non-filamentous ascomycete, are referred to as MATa and MATα. [10]

Mating type genes in ascomycetes are called idiomorphs rather than alleles due to the uncertainty of the origin by common descent. The proteins they encode are transcription factors which regulate both the early and late stages of the sexual cycle. Heterothallic ascomycetes produce gametes, which present a single Mat idiomorph, and syngamy will only be possible between gametes carrying complementary mating types. On the other hand, homothallic ascomycetes produce gametes that can fuse with every other gamete in the population (including its own mitotic descendants) most often because each haploid contains the two alternate forms of the Mat locus in its genome. [11]

Basidiomycetes can have thousands of different mating types. [12]

In the ascomycete Neurospora crassa matings are restricted to interaction of strains of opposite mating type. This promotes some degree of outcrossing. Outcrossing, through complementation, could provide the benefit of masking recessive deleterious mutations in genes which function in the dikaryon and/or diploid stage of the life cycle. [13]

Evolution

Mating types likely predate anisogamy, [14] and sexes evolved directly from mating types or independently in some lineages. [15]

Studies on green algae have provided evidence for the evolutionary link between sexes and mating types. [16] In 2006 Japanese researchers found a gene in males of Pleodorina starrii that is an orthologue to a gene for a mating type in the Chlamydomonas reinhardtii . [17] In Volvocales, the plus mating type is the ancestor to female. [18]

In ciliates multiple mating types evolved from binary mating types in several lineages. [19] : 75  As of 2019, genomic conflict has been considered the leading explanation for the evolution of two mating types. [20]

Secondary mating types evolved alongside simultaneous hermaphrodites in several lineages. [19] : 71 [ clarification needed ]

See also

Related Research Articles

An allele, or allelomorph, is a variant of the sequence of nucleotides at a particular location, or locus, on a DNA molecule.

<span class="mw-page-title-main">Major histocompatibility complex</span> Cell surface proteins, part of the acquired immune system

The major histocompatibility complex (MHC) is a large locus on vertebrate DNA containing a set of closely linked polymorphic genes that code for cell surface proteins essential for the adaptive immune system. These cell surface proteins are called MHC molecules.

<span class="mw-page-title-main">Karyogamy</span> Fusion of the nuclei of two haploid eukaryotic cells

Karyogamy is the final step in the process of fusing together two haploid eukaryotic cells, and refers specifically to the fusion of the two nuclei. Before karyogamy, each haploid cell has one complete copy of the organism's genome. In order for karyogamy to occur, the cell membrane and cytoplasm of each cell must fuse with the other in a process known as plasmogamy. Once within the joined cell membrane, the nuclei are referred to as pronuclei. Once the cell membranes, cytoplasm, and pronuclei fuse, the resulting single cell is diploid, containing two copies of the genome. This diploid cell, called a zygote or zygospore can then enter meiosis, or continue to divide by mitosis. Mammalian fertilization uses a comparable process to combine haploid sperm and egg cells (gametes) to create a diploid fertilized egg.

<span class="mw-page-title-main">Non-Mendelian inheritance</span> Type of pattern of inheritance

Non-Mendelian inheritance is any pattern in which traits do not segregate in accordance with Mendel's laws. These laws describe the inheritance of traits linked to single genes on chromosomes in the nucleus. In Mendelian inheritance, each parent contributes one of two possible alleles for a trait. If the genotypes of both parents in a genetic cross are known, Mendel's laws can be used to determine the distribution of phenotypes expected for the population of offspring. There are several situations in which the proportions of phenotypes observed in the progeny do not match the predicted values.

Heterothallic species have sexes that reside in different individuals. The term is applied particularly to distinguish heterothallic fungi, which require two compatible partners to produce sexual spores, from homothallic ones, which are capable of sexual reproduction from a single organism.

<span class="mw-page-title-main">Pleiotropy</span> Influence of a single gene on multiple phenotypic traits

Pleiotropy occurs when one gene influences two or more seemingly unrelated phenotypic traits. Such a gene that exhibits multiple phenotypic expression is called a pleiotropic gene. Mutation in a pleiotropic gene may have an effect on several traits simultaneously, due to the gene coding for a product used by a myriad of cells or different targets that have the same signaling function.

Genetics, a discipline of biology, is the science of heredity and variation in living organisms.

<span class="mw-page-title-main">Mating of yeast</span> Biological process of yeast

The mating of yeast, also known as yeast sexual reproduction, is a fundamental biological process that promotes genetic diversity and adaptation in yeast species. Yeasts such as Saccharomyces cerevisiae are single-celled eukaryotes that can exist as either haploid cells, which contain a single set of chromosomes, or diploid cells, which contain two sets of chromosomes. Haploid yeast cells come in two mating types, a and 'α', each producing specific pheromones to identify and interact with the opposite type, thus displaying simple sexual differentiation. This mating type is determined by a specific genetic locus known as MAT, which governs the mating behaviour of the cells. Haploid yeast can switch mating types through a form of genetic recombination, allowing them to change mating type as often as every cell cycle. When two haploid cells of opposite mating types encounter each other, they undergo a complex signaling process that leads to cell fusion and the formation of a diploid cell. Diploid cells can then reproduce asexually or, under nutrient-limiting conditions, undergo meiosis to produce new haploid spores.

A meiocyte is a type of cell that differentiates into a gamete through the process of meiosis. Through meiosis, the diploid meiocyte divides into four genetically different haploid gametes. The control of the meiocyte through the meiotic cell cycle varies between different groups of organisms.

<span class="mw-page-title-main">Mating in fungi</span> Combination of genetic material between compatible mating types

Fungi are a diverse group of organisms that employ a huge variety of reproductive strategies, ranging from fully asexual to almost exclusively sexual species. Most species can reproduce both sexually and asexually, alternating between haploid and diploid forms. This contrasts with most multicellular eukaryotes such as mammals, where the adults are usually diploid and produce haploid gametes which combine to form the next generation. In fungi, both haploid and diploid forms can reproduce – haploid individuals can undergo asexual reproduction while diploid forms can produce gametes that combine to give rise to the next generation.

<span class="mw-page-title-main">HLA-DR</span> Subclass of HLA-D antigens that consist of alpha and beta chains

HLA-DR is an MHC class II cell surface receptor encoded by the human leukocyte antigen complex on chromosome 6 region 6p21.31. The complex of HLA-DR and peptide, generally between 9 and 30 amino acids in length, constitutes a ligand for the T-cell receptor (TCR). HLA were originally defined as cell surface antigens that mediate graft-versus-host disease. Identification of these antigens has led to greater success and longevity in organ transplant.

<span class="mw-page-title-main">Lorna Casselton</span> British geneticist, academic and educator

Lorna Ann Casselton, was a British academic and biologist. She was Professor Emeritus of Fungal Genetics in the Department of Plant Science at the University of Oxford, and was known for her genetic and molecular analysis of the mushroom Coprinus cinereus and Coprinus lagopus.

<i>Setosphaeria turcica</i> Species of fungus

Setosphaeria turcica is the causal agent of northern corn leaf blight in maize. It is a serious fungal disease prevalent in cooler climates and tropical highlands wherever corn is grown. It is characterized by large cigar shaped necrotic lesions that develop on the leaves due to the polyketide metabolite monocerin.

<span class="mw-page-title-main">HLA-DQB1</span> Protein-coding gene in the species Homo sapiens

Major histocompatibility complex, class II, DQ beta 1, also known as HLA-DQB1, is a human gene and also denotes the genetic locus that contains this gene. The protein encoded by this gene is one of two proteins that are required to form the DQ heterodimer, a cell surface receptor essential to the function of the immune system.

Homothallic refers to the possession, within a single organism, of the resources to reproduce sexually; 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.

<span class="mw-page-title-main">Zygosity</span> Degree of similarity of the alleles in an organism

Zygosity is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism.

John Robert "Red" Raper (1911–1974) was an American mycologist who studied genetic control of sexuality in fungi, mating type compatibility, fungal genetics, and taught at Harvard University among other places.

SilentInformationRegulator (SIR) proteins are involved in regulating gene expression. SIR proteins organize heterochromatin near telomeres, ribosomal DNA (rDNA), and at silent loci including hidden mating type loci in yeast. The SIR family of genes encodes catalytic and non-catalytic proteins that are involved in de-acetylation of histone tails and the subsequent condensation of chromatin around a SIR protein scaffold. Some SIR family members are conserved from yeast to humans.

Sexual selection has been observed in fungi as a part of their reproduction, although they also often reproduce asexually. In the basidiomycetes, the sex ratio is biased towards males, implying sexual selection there. Male–male competition to fertilize occurs in fungi including yeasts. Pheromone signaling is used by female gametes and by conidia, implying male choice in these cases. Female–female competition may also occur, indicated by the much faster evolution of female-biased genes in fungi.

<span class="mw-page-title-main">Joseph Heitman</span>

Joseph Heitman is an American physician-scientist focused on research in genetics, microbiology, and infectious diseases. He is the James B. Duke Professor and Chair of the Department of Molecular Genetics and Microbiology at Duke University School of Medicine.

References

  1. 1 2 "mating type". Oxford Reference. Retrieved 2021-08-26.
  2. ↑ From Mating Types to Sexes. Bachtrog D, Mank JE, Peichel CL, Kirkpatrick M, Otto SP, et al. (2014) Sex Determination: Why So Many Ways of Doing It? PLoS Biol 12(7): e1001899. doi:10.1371/journal.pbio.1001899
  3. ↑ Idnurm, Alexander; Hood, Michael E.; Johannesson, Hanna; Giraud, Tatiana (2015-12-01). "Contrasted patterns in mating-type chromosomes in fungi: Hotspots versus coldspots of recombination". Fungal Biology Reviews. Special Issue: Fungal sex and mushrooms – A credit to Lorna Casselton. 29 (3): 220–229. doi:10.1016/j.fbr.2015.06.001. ISSN   1749-4613.
  4. 1 2 Kamada, Takashi (May 2002). "Molecular genetics of sexual development in the mushroom Coprinus cinereus". BioEssays. 24 (5): 449–459. doi:10.1002/bies.10083. ISSN   0265-9247.
  5. ↑ Riquelme, Meritxell; Challen, Michael P; Casselton, Lorna A; Brown, Andrew J (2005-07-01). "The Origin of Multiple B Mating Specificities in Coprinus cinereus". Genetics. 170 (3): 1105–1119. doi:10.1534/genetics.105.040774. ISSN   1943-2631. PMC   1451185 . PMID   15879506.
  6. ↑ Brown, Andrew J.; Casselton, Lorna A. (2001-07-01). "Mating in mushrooms: increasing the chances but prolonging the affair". Trends in Genetics. 17 (7): 393–400. doi:10.1016/S0168-9525(01)02343-5. ISSN   0168-9525.
  7. ↑ Kothe, Erika (1996). "Tetrapolar fungal mating types: Sexes by the thousands". FEMS Microbiology Reviews. 18 (1): 65–87. doi: 10.1016/0168-6445(96)00003-4 . PMID   8672296.
  8. ↑ Yoder, O.C.; Valent, Barbara; Chumley, Forrest (1986). "Genetic Nomenclature and Practice for Plant Pathogenic Fungi" (PDF). Phytopathology. 76 (4): 383–385. doi:10.1094/phyto-76-383 . Retrieved 11 November 2015.
  9. ↑ Turgeon, B.G.; Yoder, O.C. (2000). "Proposed Nomenclature for Mating Type Genes of Filamentous Ascomycetes". Fungal Genetics and Biology. 31 (1): 1–5. doi:10.1006/fgbi.2000.1227. PMID   11118130.
  10. ↑ Hanson, Sara J; Wolfe, Kenneth H (2017-05-01). "An Evolutionary Perspective on Yeast Mating-Type Switching". Genetics. 206 (1): 9–32. doi:10.1534/genetics.117.202036. ISSN   1943-2631. PMC   5419495 . PMID   28476860.
  11. ↑ Giraud, T.; et al. (2008). "Mating system of the anther smut fungus Microbotryum violaceum: Selfing under heterothallism". Eukaryotic Cell. 7 (5): 765–775. doi:10.1128/ec.00440-07. PMC   2394975 . PMID   18281603.
  12. ↑ Casselton LA (2002). "Mate recognition in fungi". Heredity. 88 (2): 142–147. doi: 10.1038/sj.hdy.6800035 . PMID   11932772.
  13. ↑ Bernstein H, Byerly HC, Hopf FA, Michod RE. Genetic damage, mutation, and the evolution of sex. Science. 1985 Sep 20;229(4719):1277-81. doi: 10.1126/science.3898363. PMID 3898363
  14. ↑ Andersson, Malte (1994-06-16). Sexual Selection. Princeton University Press. p. 4. ISBN   978-0-691-00057-2.
  15. ↑ Perrin, Nicolas (2012-04-06). "What Uses Are Mating Types? The "Developmental Switch" Model". Evolution. 66 (4): 947–956. doi:10.1111/j.1558-5646.2011.01562.x. PMID   22486681. S2CID   5798638.
  16. ↑ Sawada, Hitoshi; Inoue, Naokazu; Iwano, Megumi (2014). Sexual Reproduction in Animals and Plants. Springer. pp. 215–227. ISBN   978-4-431-54589-7.
  17. ↑ Nozaki, Hisayoshi; Mori, Toshiyuki; Misumi, Osami; Matsunaga, Sachihiro; Kuroiwa, Tsuneyoshi (2006-12-19). "Males evolved from the dominant isogametic mating type". Current Biology. 16 (24): R1018–1020. Bibcode:2006CBio...16R1018N. doi: 10.1016/j.cub.2006.11.019 . ISSN   0960-9822. PMID   17174904. S2CID   15748275.
  18. ↑ Togashi, Tatsuya; Cox, Paul Alan (2011-04-14). The Evolution of Anisogamy: A Fundamental Phenomenon Underlying Sexual Selection. Cambridge University Press. pp. 1–15. ISBN   978-1-139-50082-1.
  19. 1 2 Beukeboom, Leo W.; Perrin, Nicolas (2014). The Evolution of Sex Determination. Oxford University Press. ISBN   978-0-19-965714-8.
  20. ↑ Hill, Geoffrey E. (2019-04-30). Mitonuclear Ecology. Oxford University Press. p. 115. ISBN   978-0-19-881825-0.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.