Neurospora Intermedia Var

''Neurospora'' is a genus of Ascomycete fungi. The genus name, meaning "nerve spore" refers to the characteristic striations on the spores that resemble axons.

The best known species in this genus is ''Neurospora crassa'', a common model organism in biology. '' Neurospora intermedia'' var. ''oncomensis'' is believed to be the only mold belonging to ''Neurospora'' which is used in food production (to make oncom).

Characteristics

''Neurospora'' species are molds with broadly spreading colonies, with abundant production of ascomata. Ascomata are superficial or immersed, perithecial and ostiolate or cleistothecial and non-ostiolate, hairy or glabrous, dark coloured. Peridium membranaceous, asci cylindrical, clavate or subspherical, with a persistent or evanescent wall, usually with a thickened and non-amyloid annular structure at the apex, usually 8-spored. Ascospores broadly fusiform, ellipsoidal, or nearly spherical, unicellular, hyaline to yellowish brown or olive-brown, becoming dark and opaque at maturity, ascospore wall with longitudinal ribs or pitted, occasionally nearly smooth, 1–2 (but rarely up to 12) germ pores disposed at the ends of the ascospores, gelatinous sheaths or appendages are absent. Anamorphs are known in only a relatively small number of species, which belong to the fungi imperfecti genus ''Chrysonilia''. The type species of the genus is ''Neurospora sitophila'' Shear.

Systematics

The former genus '' Gelasinospora'' is closely related and not resolved as a distinct monophyletic group, thus the former genus is nowadays included as a synonym of ''Neurospora''.

Species

*'' Neurospora africana''
*'' Neurospora autosteira''
*'' Neurospora bonaerensis''
*'' Neurospora brevispora''
*'' Neurospora caffra''
*'' Neurospora calospora''
*'' Neurospora cerealis''
*''Neurospora crassa''
*'' Neurospora cratophora''
*'' Neurospora dictyophora''
*'' Neurospora discreta''
*'' Neurospora dodgei''
*'' Neurospora endodonta''
*'' Neurospora erythraea''
*'' Neurospora fallaciosa''
*'' Neurospora foveaconica''
*'' Neurospora galapagosensis''
*'' Neurospora goundaensis''
*'' Neurospora hapsidophora''
*'' Neurospora heterospora''
*'' Neurospora himalayensis''
*'' Neurospora hippopotama''
*'' Neurospora hispaniola''
*'' Neurospora indica''
*'' Neurospora intermedia''
*'' Neurospora inversa''
*'' Neurospora kobi''
*'' Neurospora lineolata''
*'' Neurospora longispora''
*'' Neurospora macrospora''
*'' Neurospora metzenbergii''
*'' Neurospora micropertusa''
*'' Neurospora mirabilis''
*'' Neurospora multiforis''
*'' Neurospora nigeriensis''
*'' Neurospora novoguineensis''
*'' Neurospora pannonica''
*'' Neurospora perkinsii''
*'' Neurospora pseudocalospora''
*'' Neurospora pseudoreticulata''
*'' Neurospora reticulata''
*'' Neurospora retispora''
*'' Neurospora saitoi''
*'' Neurospora santi-florii''
*'' Neurospora seminuda''
*'' Neurospora sitophila''
*'' Neurospora sphaerospora''
*'' Neurospora stellata''
*'' Neurospora sublineolata''
*'' Neurospora terricola''
*'' Neurospora tetrasperma''
*'' Neurospora tetraspora''
*'' Neurospora toroi''
*'' Neurospora udagawae''
*'' Neurospora uniporata''
*'' Neurospora varians''
*'' Neurospora xylopiae''

As model organisms

''Neurospora'' is widely used in genetics as a model organism (especially ''N. crassa'') because it quickly reproduces, is easy to culture, and can survive on minimal media (inorganic salts, glucose, water and biotin in agar).

The first studies of sexual reproduction in ''Neurospora'' were made by B. O. Dodge. ''Neurospora'' was later used by George Wells Beadle and Edward Lawrie Tatum in X-ray mutation experiments to discover mutants that would differ in nutritional requirements. The results of their experiments led them to the one gene-one enzyme hypothesis, in which they postulated that every enzyme was encoded with its own gene.

Research with ''Neurospora'' is reported semi-annually at the Neurospora Meeting at Asilomar, California, coordinated by the Fungal Genetics Stock Center. Mutant and wild-type strains of ''Neurospora'' are available from the FGSC. The FGSC also publishes the Fungal Genetics Reports.

Important people in ''Neurospora'' research:
* Bernard Ogilvie Dodge (1872–1960)
*George Beadle (Nobel Prize in Physiology or Medicine, 1958)
*Edward Tatum (Nobel Prize in Physiology or Medicine, 1958)
* Esther LederbergGiles, N. H. Jr., Lederberg, E. Z., March 1948, "Induced reversions of biochemical mutants in Neurospora crassa", American Journal of Botany 35(3):150-157
* Norman Giles
* David Perkins
*Robert Metzenberg
* Norman Horowitz
* Herschel K. Mitchell
* Mary B. Mitchell
* Martha Merrow

Sexual reproduction

In the heterothallic species ''Neurospora crassa'', the interaction of haploid strains of opposite mating type is necessary for the occurrence of sexual reproduction and the production of ascospores by meiosis. Ascospores then restore haploid individuals of either mating type. The life cycle phase is thus predominantly haploid, however, upon mating, the nuclei do not immediately fuse: karyogamy is delayed until the very onset of meiosis. The resulting mycelium is called a heterokaryon and is neither diploid nor haploid. The genus ''Neurospora'' also includes homothallic species in which a single haploid individual carries both mating type loci and can undergo self-fertilization leading to meiosis and sexual reproduction. ''Neurospora africana'' is an example of such a species. Additionally, some "Neurospora" species are said pseudohomothallic. They carry both mating types, but in separate nuclei in the same individual. Two haploid nuclei originating from the same meiosis are packaged into one ascospore. The individual is thus permanently heterokaryotic. Examples of this mating system include "Neurospora tetrasperma" and "Neurospora tetraspora".
Because heterothallic species necessarily undergo some degree of outcrossing they may benefit from a higher efficiency of selection because of higher effective recombination rates. In contrast, pseudohomothallic and homothallic species do not outcross (or rarely) and do not experience these benefits: in homothallics a reduced efficiency of negative selection has been shown. However, both hetero- and pseudohomothallic species benefit from the masking of deleterious recessive alleles in the heterokaryotic phase. In addition, all species derive the benefits of meiosis that include the removal of stress-induced DNA damages by homologous recombinational repair, and the formation of stress-resistant ascospores.

References

External links

*


Fungal Genetics Stock Center


Neurospora Meeting website

Neurospora strains
at the FGSC




at University of Edinburgh, UK. Website includes many movies and images of ''Neurospora''.


Fungal Genetics Reports


Montenegro-Montero A. (2010) "The Almighty Fungi: The Revolutionary Neurospora crassa". A historical view of the many contributions of this organism to molecular biology.


''Neurospora crassa'' genome

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Sordariales
Sordariomycetes genera
Taxa described in 1927