Androgenesis

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Androgenesis is a system of asexual reproduction that requires the presence of eggs and occurs when a zygote is produced with only paternal nuclear genes. During standard sexual reproduction, one female and one male parent each produce haploid gametes (such as a sperm or egg cell, each containing only a single set of chromosomes), which recombine to create offspring with genetic material from both parents. However, in androgenesis, there is no recombination of maternal and paternal chromosomes, and only the paternal chromosomes are passed down to the offspring (the inverse of this is gynogenesis, where only the maternal chromosomes are inherited, which is more common than androgenesis). [1] The offspring produced in androgenesis will still have maternally inherited mitochondria, as is the case with most sexually reproducing species.

Contents

One of two things can occur to produce offspring with exclusively paternal genetic material: the maternal nuclear genome can be eliminated from the zygote, or the female can produce an egg with no nucleus, resulting in an embryo developing with only the genome of the male gamete.

Androgenesis blurs the lines between sexual and asexual reproduction–it is not strictly a form of asexual reproduction because both male and female gametes are required. However, it is not strictly a form of sexual reproduction because the offspring have uniparental nuclear DNA that has not undergone recombination, and the proliferation of androgenesis can lead to exclusively asexually reproducting species. [1]

Androgenesis occurs in nature in many organisms. like plants [2] , invertebrates (for example, clams, [3] stick insects, [4] some ants, [5] bees, [2] flies [6] and parasitic wasps [2] ) and vertebrates (mainly amphibians [7] and fish [2] [8] ). The Androgenesis has been observed in roosters [9] [10] and genetically modified laboratory mice. [11]

Elimination of the maternal nuclear genome

When androgenesis occurs via elimination of the maternal nuclear genome, the elimination takes place after fertilisation. The nuclei of the two gametes fuse as normal, but immediately afterwards the male nuclear genome then eliminates the female nuclear genome, leaving a fertilized ovum with only the nuclear genome of the male parent. If viable, the resulting offspring is a clone or sub-clone of the sperm or pollen parent. [12]

Elimination of the maternal nuclear genome is evolutionarily advantageous for the male parent, because all offspring produced have the entirely paternally-inherited alleles: in contrast, a male parent that reproduces sexually without androgenesis only passes down half its genetic material to each of its offspring. A male allele promoting the elimination of the female gametic nucleus therefore has a high fitness advantage and can spread through a population and even reach fixation. [12] However, this may be part of the reason androgenesis is very rarely observed in nature: despite being advantageous to the individual producing offspring, it is deleterious to the population as a whole: if an androgenesis-inducing allele reaches high frequencies, egg-producing individuals become rare. Because both egg- and sperm-producers are necessary for androgenesis, if the sex ratio becomes highly unbalanced and there are too few egg-producers, the population is driven to extinction. [12] However, in hermaphrodites (species where a single individual produces both male and female gametes), this is less of a problem since there is no sex ratio.

Female production of a non-nuclear egg

Androgenesis can also occur through female production of an egg without a nucleus. Upon fertilization with pollen or sperm, there is no maternal nucleus to expel, and a zygote is produced that derives its nuclear genome entirely from its paternal parent. It is unclear why production of non-nucleate eggs would have evolved, because there is no fitness advantage to the egg parent: none of its nuclear genes are being passed onto its offspring. Therefore, any female allele causing non-nucleate egg production would be highly disadvantageous. This form of androgenesis could spread through genetic drift, or if there is some unknown benefit to the egg parent. Species in which non-nucleate egg production occurs are less likely to go extinct than species where the maternal nuclear genome is eliminated. This is because females producing non-nucleate eggs are disfavored by natural selection, so their proportion in a population will remain low. [12]

Male apomixis

Other type of androgenesis is the male apomixis or paternal apomixis is a reproductive process in which a plant develops from a sperm cell (male gamete) without the participation of a female cell (ovum). In this process, the zygote is formed solely with genetic material from the father, resulting in offspring genetically identical to the male organism. [13] [14] [15] This has been noted in many plants like Nicotiana , Capsicum frutescens , Cicer arietinum , Poa arachnifera , Solanum verrucosum , Phaeophyceae , [16] Pripsacum dactyloides , Zea mays , [2] and occurs as the regular reproductive method in Cupressus dupreziana . [13] This contrasts with the more common apomixis, where development occurs without fertilization, but with genetic material only from the mother.

There are also clonal species that reproduce through vegetative reproduction like Lomatia tasmanica [17] , Lagarostrobos franklinii [17] , Elodea canadensis [18] and Pando, [19] where the genetic material is exclusively male.

Obligate androgenesis

Although the most common term to refer to totally asexual reproduction in males is Paternal Apomixis, the term Obligated Androgenesis is more used in animals.

Obligate androgenesis is the process in which males are able to produce offspring exclusively through male genetic material, where mating with females of related species is not necessary to produce offspring, which leads to these species being able to survive in the absence of females. They are also capable of interbreeding with sexual and other androgenetic lineages in a phenomenon known as "egg parasitism." This method of reproduction is relatively rare as it has been found in several species of clams of the genus Corbicula [3] and recently in the all male fish specie Squalius alburnoides . [8] [20]

Ploidy in androgenesis

Individuals produced through androgenesis can be either haploid or diploid (having one or two sets of chromosomes, respectively), depending on the species. Diploidy occurs through either the fusion of two haploid sperm cells or the duplication of chromosomes from one haploid sperm cell. In both cases the offspring experience a loss of genetic variation: individuals with the genome of 2 fused sperm cells will suffer from inbreeding depression, and individuals with the genome of a duplicated sperm will be fully homozygous. In species with male heterogamety (males have XY or XO chromosomes and females have XX, like in most mammals), the doubling of male chromosomes will cause all offspring to be female: if the sperm carries an X chromosome, the embryo must be XX, and if it carries a Y or O, the embryo will be YY or OO, and unviable. With sperm fusion, a quarter of fertilized eggs will be female (XX), half will be male (XO or XY), and a quarter will be non-viable (YY or OO). [12]

Androgenesis is more common in haplo-diploid species, a species where sex is determined by ploidy, males generally develop from an unfertilized egg and females from a fertilized egg, than in diploid species (where all sexes are diploid). This is because with haplo-diploids, there is no requirement of the doubling of chromosomes from a haploid gamete, so that no embryos are lost due to YY or OO chromosomes. [12]

Androgenesis in non-gonochoristic species

Androgenesis is more likely to persist in hermaphrodites than in species with two distinct sexes (gonochorists) because all individuals have the ability to produce ovum, so the spread of androgenesis-promoting alleles causing egg-producers to become scarce is not an issue. Androgenesis is also seen more frequently in species that already have uncommon modes of reproduction such as hybridogenesis and parthenogenesis, and is sometimes seen in interspecies hybridization. [12]

Induced androgenesis

Humans sometimes induce androgenesis to create clonal lines in plants (specifically crops), fish, and silkworms. A common method of inducing androgenesis is through irradiation. The egg cells can have their nuclei inactivated by gamma ray, UV, or X-ray radiation before being fertilized with sperm or pollen. A 2015 study was successful in producing zebrafish adrogenones by cold-shocking just fertilized eggs, which prevents the first cleavage event that doubles the chromosome number after parthenogenesis, and then heat-shocking them to double their chromosome number. [21]

See also

Related Research Articles

<span class="mw-page-title-main">Asexual reproduction</span> Reproduction without a sexual process

Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the full set of genes of their single parent and thus the newly created individual is genetically and physically similar to the parent or an exact clone of the parent. Asexual reproduction is the primary form of reproduction for single-celled organisms such as archaea and bacteria. Many eukaryotic organisms including plants, animals, and fungi can also reproduce asexually. In vertebrates, the most common form of asexual reproduction is parthenogenesis, which is typically used as an alternative to sexual reproduction in times when reproductive opportunities are limited. Some monitor lizards, including Komodo dragons, can reproduce asexually.

<span class="mw-page-title-main">Gamete</span> Haploid sex cell

A gamete is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. The name gamete was introduced by the German cytologist Eduard Strasburger in 1878.

<span class="mw-page-title-main">Meiosis</span> Cell division producing haploid gametes

Meiosis (; from Ancient Greek μείωσις 'lessening', is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one copy of each chromosome. Additionally, prior to the division, genetic material from the paternal and maternal copies of each chromosome is crossed over, creating new combinations of code on each chromosome. Later on, during fertilisation, the haploid cells produced by meiosis from a male and a female will fuse to create a zygote, a cell with two copies of each chromosome again.

<span class="mw-page-title-main">Ploidy</span> Number of sets of chromosomes of a cell

Ploidy is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Here sets of chromosomes refers to the number of maternal and paternal chromosome copies, respectively, in each homologous chromosome pair—the form in which chromosomes naturally exist. Somatic cells, tissues, and individual organisms can be described according to the number of sets of chromosomes present : monoploid, diploid, triploid, tetraploid, pentaploid, hexaploid, heptaploid or septaploid, etc. The generic term polyploid is often used to describe cells with three or more sets of chromosomes.

<span class="mw-page-title-main">Reproduction</span> Biological process by which new organisms are generated from one or more parent organisms

Reproduction is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. There are two forms of reproduction: asexual and sexual.

<span class="mw-page-title-main">Sex</span> Trait that determines an organisms sexually reproductive function

Sex is the biological trait that determines whether a sexually reproducing organism produces male or female gametes. During sexual reproduction, a male and a female gamete fuse to form a zygote, which develops into an offspring that inherits traits from each parent. By convention, organisms that produce smaller, more mobile gametes are called male, while organisms that produce larger, non-mobile gametes are called female. An organism that produces both types of gamete is hermaphrodite.

<span class="mw-page-title-main">Zygote</span> Diploid eukaryotic cell formed by fertilization between two gametes

A zygote is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. The sexual fusion of haploid cells is called karyogamy, the result of which is the formation of a diploid cell called the zygote or zygospore.

<span class="mw-page-title-main">Fertilisation</span> Union of gametes of opposite sexes during the process of sexual reproduction to form a zygote

Fertilisation or fertilization, also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a zygote and initiate its development into a new individual organism or offspring. While processes such as insemination or pollination, which happen before the fusion of gametes, are also sometimes informally referred to as fertilisation, these are technically separate processes. The cycle of fertilisation and development of new individuals is called sexual reproduction. During double fertilisation in angiosperms, the haploid male gamete combines with two haploid polar nuclei to form a triploid primary endosperm nucleus by the process of vegetative fertilisation.

<span class="mw-page-title-main">Alternation of generations</span> Reproductive cycle of plants and algae

Alternation of generations is the predominant type of life cycle in plants and algae. In plants both phases are multicellular: the haploid sexual phase – the gametophyte – alternates with a diploid asexual phase – the sporophyte.

<span class="mw-page-title-main">Apomixis</span> Replacement of the normal sexual reproduction by asexual reproduction, without fertilization

In botany, apomixis is asexual development of seed or embryo without fertilization. However, other definitions include replacement of the seed by a plantlet or replacement of the flower by bulbils.

<span class="mw-page-title-main">Double fertilization</span> Complex fertilization mechanism of flowering plants

Double fertilization or double fertilisation is a complex fertilization mechanism of angiosperms. This process involves the fusion of a female gametophyte or megagametophyte, also called the embryonic sac, with two male gametes (sperm). It begins when a pollen grain adheres to the stigmatic surface of the carpel, the female reproductive structure of angiosperm flowers. The pollen grain begins to germinate, forming a pollen tube that penetrates and extends down through the style toward the ovary as it follows chemical signals released by the egg. The tip of the pollen tube then enters the ovary by penetrating through the micropyle opening in the ovule, and releases two sperm into the embryonic sac (megagametophyte).

<span class="mw-page-title-main">Haplodiploidy</span> Biological system where sex is determined by the number of sets of chromosomes

Haplodiploidy is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid. Haplodiploidy is sometimes called arrhenotoky.

Plant reproduction is the production of new offspring in plants, which can be accomplished by sexual or asexual reproduction. Sexual reproduction produces offspring by the fusion of gametes, resulting in offspring genetically different from either parent. Asexual reproduction produces new individuals without the fusion of gametes, resulting in clonal plants that are genetically identical to the parent plant and each other, unless mutations occur.

<span class="mw-page-title-main">Parthenogenesis</span> Asexual reproduction without fertilization

Parthenogenesis is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means development of an embryo from an unfertilized egg cell. In plants, parthenogenesis is a component process of apomixis. In algae, parthenogenesis can mean the development of an embryo from either an individual sperm or an individual egg.

<span class="mw-page-title-main">Sexual reproduction</span> Biological process

Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete with a single set of chromosomes combines with another gamete to produce a zygote that develops into an organism composed of cells with two sets of chromosomes (diploid). This is typical in animals, though the number of chromosome sets and how that number changes in sexual reproduction varies, especially among plants, fungi, and other eukaryotes.

<span class="mw-page-title-main">Klepton</span> Species that requires input from another biological taxon to complete its reproductive cycle

In biology, a klepton and synklepton is a species that requires input from another biological taxon to complete its reproductive cycle. Specific types of kleptons are zygokleptons, which reproduce by zygogenesis; gynokleptons which reproduce by gynogenesis, and tychokleptons, which reproduce by a combination of both systems.

Parthenogenesis is a mode of asexual reproduction in which offspring are produced by females without the genetic contribution of a male. Among all the sexual vertebrates, the only examples of true parthenogenesis, in which all-female populations reproduce without the involvement of males, are found in squamate reptiles. There are about 50 species of lizard and 1 species of snake that reproduce solely through parthenogenesis. It is unknown how many sexually reproducing species are also capable of parthenogenesis in the absence of males, but recent research has revealed that this ability is widespread among squamates.

Parthenogenesis is a form of reproduction where eggs develop without fertilization, resulting in unisexual species. This phenomenon is closely related with reproductive modes such as hybridogenesis, where fertilization occurs, but the paternal DNA is not passed on. Among amphibians, it is seen in numerous frog and salamander species, but has not been recorded in caecilians.

Autogamy or self-fertilization refers to the fusion of two gametes that come from one individual. Autogamy is predominantly observed in the form of self-pollination, a reproductive mechanism employed by many flowering plants. However, species of protists have also been observed using autogamy as a means of reproduction. Flowering plants engage in autogamy regularly, while the protists that engage in autogamy only do so in stressful environments.

Gynogenesis, a form of parthenogenesis, is a system of asexual reproduction that requires the presence of sperm without the actual contribution of its DNA for completion. The paternal DNA dissolves or is destroyed before it can fuse with the egg. The egg cell of the organism is able to develop, unfertilized, into an adult using only maternal genetic material. Gynogenesis is often termed "sperm parasitism" in reference to the somewhat pointless role of male gametes. Gynogenetic species, "gynogens" for short, are unisexual, meaning they must mate with males from a closely related bisexual species that normally reproduces sexually.

References

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  2. 1 2 3 4 5 Schwander, Tanja; Oldroyd, Benjamin P (28 Sep 2008). "Androgenesis: where males hijack eggs to clone themselves".
  3. 1 2 Hedtke, Shannon M.; Stanger-Hall, Kathrin; Baker, Robert J.; Hillis, David M. (May 2008). "All-Male Asexuality: Origin and Maintenance of Androgenesis in the Asian Clam Corbicula". Evolution. 62 (5): 1119–1136. doi:10.1111/j.1558-5646.2008.00344.x. PMID   18266987.
  4. ↑ Tinti, Fausto; Scali, Valerio (November 1992). "Genome exclusion and gametic dapi—dna content in the hybridogenetic Bacillus rossius—grandii benazzii complex (insecta phasmatodea)". Molecular Reproduction and Development. 33 (3): 235–242. doi:10.1002/mrd.1080330302. PMID   1449790.
  5. ↑ Fournier, Denis; Estoup, Arnaud; Orivel, Jérôme; Foucaud, Julien; Jourdan, Hervé; Breton, Julien Le; Keller, Laurent (June 2005). "Clonal reproduction by males and females in the little fire ant". Nature. 435 (7046): 1230–1234. doi:10.1038/nature03705. PMID   15988525.
  6. ↑ Komma, D J; Endow, S A (5 December 1995). "Haploidy and androgenesis in Drosophila". Proceedings of the National Academy of Sciences. 92 (25): 11884–11888. doi: 10.1073/pnas.92.25.11884 . PMC   40507 . PMID   8524868.
  7. ↑ "All-male hybrids of a tetrapod Pelophylax esculentus share its origin and genetics of maintenance". 28 Sep 2024.
  8. 1 2 Matos, I.; Machado, M.P.; Sucena, é.; Collares-Pereira, M.J.; Schartl, M.; Coelho, M.M. (2010). "Evidence for Hermaphroditism in the Squalius alburnoides Allopolyploid Fish Complex". Sexual Development. 4 (3): 170–175. doi:10.1159/000313359.
  9. ↑ "Sigue causando asombro el gallo que puso huevos". 12 Nov 2024.
  10. ↑ "Rooster who is now laying eggs". 12 Nov 2024.
  11. ↑ Ledford, Heidi (2023). "Making mice with two dads: this biologist rewrote the rules on sexual reproduction". Nature. 624 (7992): 499. Bibcode:2023Natur.624..499L. doi:10.1038/d41586-023-03922-6. PMID   38093054.
  12. 1 2 3 4 5 6 7 Schwander, Tanja; Oldroyd, Benjamin P. (2016-10-19). "Androgenesis: where males hijack eggs to clone themselves". Philosophical Transactions of the Royal Society B: Biological Sciences. 371 (1706): 20150534. doi:10.1098/rstb.2015.0534. ISSN   0962-8436. PMC   5031619 . PMID   27619698.
  13. 1 2 Christian Pichot; Benjamin Liens; Juana L. Rivera Nava; Julien B. Bachelier; Mohamed El Maâtaoui (January 2008). "Cypress Surrogate Mother Produces Haploid Progeny From Alien Pollen". Genetics. 178 (1): 379–383. doi:10.1534/genetics.107.080572. PMC   2206086 . PMID   18202380.
  14. ↑ Christian Pichot; Bruno Fady; Isabelle Hochu (2000). "Lack of mother tree alleles in zymograms of Cupressus dupreziana A. Camus embryos". Annals of Forest Science. 57 (1): 17–22. Bibcode:2000AnFSc..57...17P. doi: 10.1051/forest:2000108 .
  15. ↑ Pichot, C.; El Maataoui, M.; Raddi, S.; Raddi, P. (2001). "Conservation: Surrogate mother for endangered Cupressus". Nature. 412 (6842): 39. doi: 10.1038/35083687 . PMID   11452293. S2CID   39046191.
  16. ↑ Heesch, Svenja; Serrano-Serrano, Martha; Barrera-Redondo, Josué; Luthringer, Rémy; Peters, Akira F; Destombe, Christophe; Cock, J Mark; Valero, Myriam; Roze, Denis; Salamin, Nicolas; Coelho, Susana M (July 2021). "Evolution of life cycles and reproductive traits: Insights from the brown algae". Journal of Evolutionary Biology. 34 (7): 992–1009. doi:10.1111/jeb.13880.
  17. 1 2 "The Oldest Soul". 10 Nov 2024.
  18. ↑ "No sex at all? Extremely low genetic diversity in Gagea spathacea (Liliaceae) across Europe". 10 Nov 2024.
  19. ↑ DeWoody, Jennifer; Rowe, Carol A.; Hipkins, Valerie D.; Mock, Karen E. (2008). ""Pando" Lives: Molecular Genetic Evidence of a Giant Aspen Clone in Central Utah". Western North American Naturalist. 68 (4): 493–497. doi:10.3398/1527-0904-68.4.493. S2CID   59135424.
  20. ↑ FishBase (en inglés)
  21. ↑ Hou, Jilun; Fujimoto, Takafumi; Saito, Taiju; Yamaha, Etsuro; Arai, Katsutoshi (2015-08-20). "Generation of clonal zebrafish line by androgenesis without egg irradiation". Scientific Reports. 5 (1): 13346. doi:10.1038/srep13346. ISSN   2045-2322. PMC   4542340 .
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