BASIDIOMYCOTA (/bəˌsɪdi.oʊmaɪˈkoʊtə/ ) is one of two large
divisions that, together with the
More specifically the
* 1 Classification
* 2 Typical life-cycle
* 3 Variations in lifecycles
* 3.1 Rusts * 3.2 Smuts
* 4 See also
* 5 References
* 5.1 Sources
* 6 External links
The most recent classification adopted by a coalition of 67
mycologists recognizes three subphyla (
* Homobasidiomycetes (alternatively called holobasidiomycetes), including true mushrooms * Heterobasidiomycetes , including the jelly , rust and smut fungi
Previously the entire
Pucciniomycotina include the rust fungi, the insect
Septobasidium , a former group of smut fungi
Microbotryomycetes , which includes mirror yeasts), and a
mixture of odd, infrequently seen, or seldom recognized fungi, often
parasitic on plants. The eight classes in the
The Ustilaginomycotina are most (but not all) of the former smut fungi and the Exobasidiales . The classes of the Ustilaginomycotina are the Exobasidiomycetes , the Entorrhizomycetes, and the Ustilaginomycetes .
Sexual reproduction cycle of basidiomycetes
Unlike higher animals and plants which have readily recognizable male
and female counterparts,
The maintenance of the dikaryotic status in dikaryons in many
In summary, meiosis takes place in a diploid basidium. Each one of the four haploid nuclei migrates into its own basidiospore. The basidiospores are ballistically discharged and start new haploid mycelia called monokaryons. There are no males or females, rather there are compatible thalli with multiple compatibility factors. Plasmogamy between compatible individuals leads to delayed karyogamy leading to establishment of a dikaryon. The dikaryon is long lasting but ultimately gives rise to either fruitbodies with basidia or directly to basidia without fruitbodies. The paired dikaryon in the basidium fuse (i.e. karyogamy takes place). The diploid basidium begins the cycle again.
Coprinopsis cinerea is a multicellular basidiomycete mushroom. It is
particularly suited to the study of meiosis because meiosis progresses
synchronously in about 10 million cells within the mushroom cap, and
the meiotic prophase stage is prolonged. Burns et al. studied the
expression of genes involved in the 15-hour meiotic process, and found
that the pattern of gene expression of C. cinerea was similar to two
other fungal species, the yeasts
Cryptococcus neoformans and Ustilago maydis are examples of pathogenic basidiomycota. Such pathogens must be able to overcome the oxidative defenses of their respective hosts in order to produce a successful infection. The ability to undergo meiosis may provide a survival benefit for these fungi by promoting successful infection. A characteristic central feature of meiosis is recombination between homologous chromosomes. This process is associated with repair of DNA damages, particularly double-strand breaks. The ability of C. neoformans and U. maydis to undergo meiosis may contribute to their virulence by removing the oxidative DNA damages caused by their host’s release of reactive oxygen species.
VARIATIONS IN LIFECYCLES
Many variations occur. Some are self-compatible and spontaneously form dikaryons without a separate compatible thallus being involved. These fungi are said to be homothallic, versus the normal heterothallic species with mating types. Others are secondarily homothallic, in that two compatible nuclei following meiosis migrate into each basidiospore, which is then dispersed as a pre-existing dikaryon. Often such species form only two spores per basidium, but that too varies. Following meiosis, mitotic divisions can occur in the basidium. Multiple numbers of basidiospores can result, including odd numbers via degeneration of nuclei, or pairing up of nuclei, or lack of migration of nuclei. For example, the chanterelle genus Craterellus often has six-spored basidia, while some corticioid Sistotrema species can have two-, four-, six-, or eight-spored basidia, and the cultivated button mushroom, Agaricus bisporus . can have one-, two-, three- or four-spored basidia under some circumstances. Occasionally, monokaryons of some taxa can form morphologically fully formed basidiomes and anatomically correct basidia and ballistic basidiospores in the absence of dikaryon formation, diploid nuclei, and meiosis. A rare few number of taxa have extended diploid lifecycles, but can be common species. Examples exist in the mushroom genera Armillaria and Xerula , both in the Physalacriaceae . Occasionally, basidiospores are not formed and parts of the "basidia" act as the dispersal agents, e.g. the peculiar mycoparasitic jelly fungus, Tetragoniomyces or the entire "basidium" acts as a "spore", e.g. in some false puffballs (Scleroderma ). In the human pathogenic genus Cryptococcus , four nuclei following meiosis remain in the basidium, but continually divide mitotically, each nucleus migrating into synchronously forming nonballistic basidiospores that are then pushed upwards by another set forming below them, resulting in four parallel chains of dry "basidiospores".
Other variations occur, some as standard lifecycles (that themselves have variations within variations) within specific orders.
Pucciniales , previously known as
Uredinales ) at their
greatest complexity, produce five different types of spores on two
different host plants in two unrelated host families. Such rusts are
heteroecious (requiring two hosts) and macrocyclic (producing all five
spores types). Wheat stem rust is an example. By convention, the
stages and spore states are numbered by
The characteristic part of the life-cycle of smuts is the
thick-walled, often darkly pigmented, ornate, teliospore that serves
to survive harsh conditions such as overwintering and also serves to
help disperse the fungus as dry diaspores . The teliospores are
initially dikaryotic but become diploid via karyogamy.
Smuts with both a yeast phase and an infectious hyphal state are examples of dimorphic Basidiomycota. In plant parasitic taxa, the saprotrophic phase is normally the yeast while the infectious stage is hyphal. However, there are examples of animal and human parasites where the species are dimorphic but it is the yeast-like state that is infectious. The genus Filobasidiella forms basidia on hyphae but the main infectious stage is more commonly known by the anamorphic yeast name Cryptococcus , e.g. Cryptococcus neoformans and Cryptococcus gattii .
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* ^ "Archived copy". Archived from the original on 2007-10-25.
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