Neurospora is a genus of Ascomycetefungi. The genus name, meaning "nerve spore" refers to the characteristic striations on the spores that resemble axons.
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.[3]
Systematics
The former genus Gelasinospora is closely related and not resolved as a distinct monophyletic group,[4] thus the former genus is nowadays included as a synonym of Neurospora.[3]
Neurospora is widely used in genetics as a model organism (especially N. crassa) because it quickly reproduces, is easy to culture,[5] 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.
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.[12][13] 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.[14] 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.[15] 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.
^Ho, C.C. (April 1986). "Identity and characteristics of Neurospora intermedia responsible for oncom fermentation in Indonesia". Food Microbiology. 3 (2): 115–132. doi:10.1016/S0740-0020(86)80035-1.
^ abGarcia, D.; et al. (2004). "A synopsis and re-circumscription of Neurospora (syn. Gelasinospora) based on ultrastructural and 28S rDNA sequence data". Mycological Research. 108 (10): 1119–1142. doi:10.1017/s0953756204000218. PMID15535064. S2CID31673455.
^Cai, L.; et al. (2006). "Phylogenetic investigations of Sordariaceae based on multiple gene sequences and morphology". Mycological Research. 110 (2): 137–150. doi:10.1016/j.mycres.2005.09.014. PMID16378718.
^ abDodge, B. O. (1932). "Crossing hermaphroditic races of Neurospora". Mycologia. 24 (1): 7–13. doi:10.2307/3753727. JSTOR3753727.
^Zimmer, E. M., August 1946, "MUTANT STRAINS OF NEUROSPORA DEFICIENT IN PARA-AMINOBENZOIC ACID", MA Thesis, Stanford University
^Hollaender, A., Sansome E. R., Zimmer, E., Demerec, M., April 1945, "Quantitative Irradiation Experiments with Neurospora crassa. II. Ultraviolet Irradiation", American Journal of Botany 32(4):226-235 Also: "Quantitative effects of radiation on mutation production in Neurospora crassa", Records of the Genetics Society of America, Number Thirteen, 1944
^ abGiles, N. H. Jr., Lederberg, E. Z., March 1948, "Induced reversions of biochemical mutants in Neurospora crassa", American Journal of Botany 35(3):150-157
^Glass NL, Smith ML (August 1994). "Structure and function of a mating-type gene from the homothallic species Neurospora africana". Mol. Gen. Genet. 244 (4): 401–9. doi:10.1007/bf00286692. PMID8078466. S2CID19747733.
^Raju, N. B., Perkins, D. D. (1994). "Diverse programs of ascus development in pseudohomothallic species of Neurospora, Gelasinospora, and Podospora". Developmental Genetics. 15 (1): 104–118. doi:10.1002/dvg.1020150111. PMID8187347.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^Nygren, Kristiina, Wallberg, Andreas, Samils, Nicklas, Stajich, Jason E., Townsend, Jeffrey P., Karlsson, Magnus, Johannesson, Hanna (2012). "Analyses of expressed sequence tags in Neurospora reveal rapid evolution of genes associated with the early stages of sexual reproduction in fungi". BMC Evol. Biol. 12 (3): 649–663. doi:10.1016/j.ympev.2011.03.023. PMID21439389.{{cite journal}}: CS1 maint: multiple names: authors list (link)
[4] Montenegro-Montero A. (2010) "The Almighty Fungi: The Revolutionary Neurospora crassa". A historical view of the many contributions of this organism to molecular biology.
