348:). Protoperithecia are formed most readily in the laboratory when growth occurs on solid (agar) synthetic medium with a relatively low source of nitrogen. Nitrogen starvation appears to be necessary for expression of genes involved in sexual development. The protoperithecium consists of an ascogonium, a coiled multicellular hypha that is enclosed in a knot-like aggregation of hyphae. A branched system of slender hyphae, called the trichogyne, extends from the tip of the ascogonium projecting beyond the sheathing hyphae into the air. The sexual cycle is initiated (i.e. fertilization occurs) when a cell (usually a conidium) of opposite mating type contacts a part of the trichogyne (see
408:
for 30 minutes to induce germination. For normal strains, the entire sexual cycle takes 10 to 15 days. In a mature ascus containing 8 ascospores, pairs of adjacent spores are identical in genetic constitution, since the last division is mitotic, and since the ascospores are contained in the ascus sac that holds them in a definite order determined by the direction of nuclear segregations during meiosis. Since the four primary products are also arranged in sequence, the pattern of genetic markers from a first-division segregation can be distinguished from the markers from a second-division segregation pattern.
352:). Such contact can be followed by cell fusion leading to one or more nuclei from the fertilizing cell migrating down the trichogyne into the ascogonium. Since both ‘A’ and ‘a’ strains have the same sexual structures, neither strain can be regarded as exclusively male or female. However, as a recipient, the protoperithecium of both the ‘A’ and ‘a’ strains can be thought of as the female structure, and the fertilizing conidium can be thought of as the male participant.
321:
325:
occur between individual strains of different mating type, ‘A’ and ‘a’. Fertilization occurs by the passage of nuclei of conidia or mycelium of one mating type into the protoperithecia of the opposite mating type through the trichogyne. Fusion of the nuclei of opposite mating types occurs within the protoperithecium to form a zygote (2N) nucleus.
360:
become associated and begin to divide synchronously. The products of these nuclear divisions (still in pairs of unlike mating type, i.e. ‘A’ / ‘a’) migrate into numerous ascogenous hyphae, which then begin to grow out of the ascogonium. Each of these ascogenous hypha bends to form a hook (or crozier)
407:
A mature perithecium may contain as many as 300 asci, each derived from identical fusion diploid nuclei. Ordinarily, in nature, when the perithecia mature the ascospores are ejected rather violently into the air. These ascospores are heat resistant and, in the lab, require heating at 60 °C
324:
Neurospora crassa life cycle. The haploid mycelium reproduces asexually by two processes: (1) simple proliferation of existing mycelium, and (2) formation of conidia (macro- and micro-) which can be dispersed and then germinate to produce new mycelium. In the sexual cycle, mating can only
135:
reproduces by mitosis as either haploid or diploid cells. However, when starved, diploid cells undergo meiosis to form haploid spores. Mating occurs when haploid cells of opposite mating type, MATa and MATα, come into contact. Ruderfer et al. pointed out that such contacts are frequent between
94:) are called "pseudo-homothallic". Instead of separating into four individual spores by two meiosis events, only a single meiosis occurs, resulting in two spores, each with two haploid nuclei of different mating types (those of its parents). This results in a spore which can mate with itself (
231:
occurs in areas with widely different climates and environments, it displays low genetic variation and lack of population genetic differentiation on a global scale. Thus the capability for heterothallic sex is maintained even though little genetic diversity is produced. As in the case of
355:
The subsequent steps following fusion of ‘A’ and ‘a’ haploid cells, have been outlined by
Fincham and Day, and by Wagner and Mitchell. After fusion of the cells, the further fusion of their nuclei is delayed. Instead, a nucleus from the fertilizing cell and a nucleus from the
168:) are unlikely to be sufficient for generally maintaining sex from one generation to the next. Rather, a short-term benefit, such as meiotic recombinational repair of DNA damages caused by stressful conditions such as starvation may be the key to the maintenance of sex in
619:
Birdsell JA, Wills C (2003). The evolutionary origin and maintenance of sexual recombination: A review of contemporary models. Evolutionary
Biology Series >> Evolutionary Biology, Vol. 33 pp. 27–137. MacIntyre, Ross J.; Clegg, Michael, T (Eds.), Springer.
163:
is heterothallic, it appears that, in nature, mating is most often between closely related yeast cells. The relative rarity in nature of meiotic events that result from outcrossing suggests that the possible long-term benefits of outcrossing (e.g. generation of
286:
is sexually reproducing, but recombination in natural populations is most likely to occur across spatially and genetically limited distances resulting in a highly clonal population structure. Sex is maintained in this species even though very little
343:
has two mating types that, in this case, are symbolized by ‘A’ and ‘a’. There is no evident morphological difference between the ‘A’ and 'a' mating type strains. Both can form abundant protoperithecia, the female reproductive structure (see
361:
at its tip and the ‘A’ and ‘a’ pair of haploid nuclei within the crozier divide synchronously. Next, septa form to divide the crozier into three cells. The central cell in the curve of the hook contains one ‘A’ and one ‘a’ nucleus (see
403:
As the above events are occurring, the mycelial sheath that had enveloped the ascogonium develops as the wall of the perithecium, becomes impregnated with melanin, and blackens. The mature perithecium has a flask-shaped structure.
261:, causing aspergillosis in immunocompromised individuals. In 2009, a sexual state of this heterothallic fungus was found to arise when strains of opposite mating type were cultured together under appropriate conditions.
130:
is heterothallic. This means that each yeast cell is of a certain mating type and can only mate with a cell of the other mating type. During vegetative growth that ordinarily occurs when nutrients are abundant,
904:
Henk DA, Shahar-Golan R, Devi KR, Boyce KJ, Zhan N, Fedorova ND, Nierman WC, Hsueh PR, Yuen KY, Sieu TP, Kinh NV, Wertheim H, Baker SG, Day JN, Vanittanakom N, Bignell EM, Andrianopoulos A, Fisher MC (2012).
388:. The two sequential divisions of meiosis lead to four haploid nuclei, two of the ‘A’ mating type and two of the ‘a’ mating type. One further mitotic division leads to four ‘A’ and four ‘a’ nuclei in each
148:, and these cells can mate with each other. The second reason is that haploid cells of one mating type, upon cell division, often produce cells of the opposite mating type with which they may mate.
384:. The diploid nucleus has 14 chromosomes formed from the two fused haploid nuclei that had 7 chromosomes each. Formation of the diploid nucleus is immediately followed by
155:
populations clonal reproduction and a type of “self-fertilization” (in the form of intratetrad mating) predominate. Ruderfer et al. analyzed the ancestry of natural
279:
Henk et al. showed that the genes required for meiosis are present in T. marneffei, and that mating and genetic recombination occur in this species.
200:, is widespread in nature, and is typically found in soil and decaying organic matter, such as compost heaps, where it plays an essential role in
654:
Sugui JA, Losada L, Wang W, Varga J, Ngamskulrungroj P, Abu-Asab M, Chang YC, O'Gorman CM, Wickes BL, Nierman WC, Dyer PS, Kwon-Chung KJ (2011).
335:
is heterothallic. Sexual fruiting bodies (perithecia) can only be formed when two mycelia of different mating type come together. Like other
641:
216:(2–3 μm) that readily become airborne. A. fumigatus possesses a fully functional sexual reproductive cycle that leads to the production of
703:
O'Gorman CM, Fuller H, Dyer PS (January 2009). "Discovery of a sexual cycle in the opportunistic fungal pathogen
Aspergillus fumigatus".
373:
that can grow to form a further crozier that can then form its own ascus-initial cell. This process can then be repeated multiple times.
528:
Ruderfer DM, Pratt SC, Seidel HS, Kruglyak L (September 2006). "Population genomic analysis of outcrossing and recombination in yeast".
756:"Low genetic variation and no detectable population structure in aspergillus fumigatus compared to closely related Neosartorya species"
625:
114:
57:
In heterothallic fungi, two different individuals contribute nuclei to form a zygote. Examples of heterothallism are included for
850:
Moore GG, Elliott JL, Singh R, Horn BW, Dorner JW, Stone EA, Chulze SN, Barros GG, Naik MK, Wright GC, Hell K, Carbone I (2013).
136:
closely related yeast cells for two reasons. The first is that cells of opposite mating type are present together in the same
907:"Clonality despite sex: the evolution of host-associated sexual neighborhoods in the pathogenic fungus Penicillium marneffei"
376:
After formation of the ascus-initial cell, the ‘A’ and ‘a’ nucleus fuse with each other to form a diploid nucleus (see
268:, suggesting that production of genetic variation may contribute to the maintenance of heterothallism in this species.
396:
is an essential part of the life cycle of all sexually reproducing organisms, and in its main features, meiosis in
573:"Heterothallism in Saccharomyces cerevisiae isolates from nature: effect of HO locus on the mode of reproduction"
956:
Westergaard M, Mitchell HK (1947). "Neurospora. Part V. A synthetic medium favoring sexual reproduction".
126:
59:
236:, above, a short-term benefit of meiosis may be the key to the adaptive maintenance of sex in this species.
571:
Katz Ezov T, Chang SL, Frenkel Z, Segrè AV, Bahalul M, Murray AW, Leu JY, Korol A, Kashi Y (January 2010).
159:
strains and concluded that outcrossing occurs only about once every 50,000 cell divisions. Thus, although
1084:
184:
73:
63:
804:
712:
365:). This binuclear cell initiates ascus formation and is called an “ascus-initial” cell. Next the two
984:
42:
that reside in different individuals. The term is applied particularly to distinguish heterothallic
288:
51:
832:
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67:
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79:
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is given in some detail, since similar life cycles are present in other heterothallic fungi.
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852:"Sexuality generates diversity in the aflatoxin gene cluster: evidence on a global scale"
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cells on either side of the first ascus-forming cell fuse with each other to form a
740:
656:"Identification and characterization of an Aspergillus fumigatus "supermater" pair"
493:
557:
1000:
923:
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771:
366:
47:
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221:
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17:
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Billiard, S.; LóPez‐Villavicencio, M.; Hood, M. E.; Giraud, T. (June 2012).
254:
99:
942:
887:
828:
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732:
689:
606:
549:
439:"Sex, outcrossing and mating types: unsolved questions in fungi and beyond"
1018:
671:
636:
Elvira Hörandl (2013). Meiosis and the
Paradox of Sex in Nature, Meiosis,
511:
113:
258:
217:
213:
209:
205:
724:
380:). This nucleus is the only diploid nucleus in the entire life cycle of
1064:
1041:
393:
385:
145:
46:, which require two compatible partners to produce sexual spores, from
35:
201:
820:
541:
389:
257:
in crops worldwide. It is also an opportunistic human and animal
137:
43:
264:
Sexuality generates diversity in the aflatoxin gene cluster in
292:
39:
188:, is a heterothallic fungus. It is one of the most common
478:"Life cycle of the budding yeast Saccharomyces cerevisiae"
151:
Katz Ezov et al. presented evidence that in natural
1036:. Oxford, UK: Blackwell Scientific Publications.
985:"Sexual development genes of Neurospora crassa"
208:recycling. Colonies of the fungus produce from
754:Rydholm C, Szakacs G, Lutzoni F (April 2006).
8:
983:Nelson MA, Metzenberg RL (September 1992).
805:"Sexual reproduction in Aspergillus flavus"
192:species to cause disease in humans with an
523:
521:
299:by a short-term benefit of meiosis, as in
29:Sexes that reside in different individuals
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362:
349:
345:
144:of cells directly produced by a single
90:Certain heterothallic species (such as
1059:. New York, NY: John Wiley and Sons.
803:Horn BW, Moore GG, Carbone I (2009).
7:
400:seems typical of meiosis generally.
83:. The heterothallic life cycle of
970:10.1002/j.1537-2197.1947.tb13032.x
25:
589:10.1111/j.1365-294X.2009.04436.x
455:10.1111/j.1420-9101.2012.02495.x
1055:Wagner RP, Mitchell HK (1964).
443:Journal of Evolutionary Biology
212:thousands of minute grey-green
494:10.1128/MMBR.52.4.536-553.1988
476:Herskowitz I (December 1988).
1:
1032:Fincham J RS, Day PR (1963).
924:10.1371/journal.ppat.1002851
869:10.1371/journal.ppat.1003574
644:, InTech, DOI: 10.5772/56542
140:, the sac that contains the
772:10.1128/EC.5.4.650-657.2006
282:Henk et al. concluded that
50:ones, which are capable of
1106:
1001:10.1093/genetics/132.1.149
958:American Journal of Botany
250:is the major producer of
127:Saccharomyces cerevisiae
118:Saccharomyces cerevisiae
108:Saccharomyces cerevisiae
60:Saccharomyces cerevisiae
54:from a single organism.
1057:Genetics and Metabolism
326:
121:
92:Neurospora tetrasperma
672:10.1128/mBio.00234-11
378:figure, top of §
363:figure, top of §
350:figure, top of §
346:figure, top of §
323:
295:may be maintained in
274:Talaromyces marneffei
185:Aspergillus fumigatus
178:Aspergillus fumigatus
116:
74:Penicillium marneffei
64:Aspergillus fumigatus
329:The sexual cycle of
725:10.1038/nature07528
717:2009Natur.457..471O
307:, discussed above.
289:genetic variability
52:sexual reproduction
327:
242:Aspergillus flavus
122:
96:intratetrad mating
68:Aspergillus flavus
642:978-953-51-1197-9
313:Neurospora crassa
166:genetic diversity
80:Neurospora crassa
16:(Redirected from
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666:(6): e00234–11.
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626:978-0306472619
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536:(9): 1077–81.
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482:Microbiol. Rev
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398:N. crassa
382:N. crassa
341:N. crassa
332:N. crassa
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311:Life cycle of
309:
291:is produced.
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272:Life cycle of
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170:S. cerevisiae
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161:S. cerevisiae
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133:S. cerevisiae
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33:Heterothallic
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18:Heterothallic
1085:Reproduction
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978:
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815:(3): 423–9.
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766:(4): 650–7.
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305:A. fumigatus
304:
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297:T. marneffei
296:
284:T. marneffei
283:
281:
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273:
265:
263:
252:carcinogenic
247:
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229:A. fumigatus
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198:A. fumigatus
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964:: 573–577.
911:PLOS Pathog
856:PLOS Pathog
367:uninucleate
337:ascomycetes
234:S. cereviae
190:Aspergillus
48:homothallic
1079:Categories
1065:B00BXTC5BO
1042:B000W851KO
530:Nat. Genet
424:References
358:ascogonium
255:aflatoxins
222:ascospores
124:The yeast
809:Mycologia
577:Mol. Ecol
463:1010-061X
266:A. flavus
248:A. flavus
227:Although
100:automixis
85:N. crassa
1090:Mycology
989:Genetics
943:23055919
888:24009506
837:20648447
829:19537215
790:16607012
733:19043401
690:22108383
607:20002587
550:16892060
412:See also
259:pathogen
206:nitrogen
1019:1356883
1010:1205113
934:3464222
879:3757046
781:1459663
741:4371721
713:Bibcode
681:3225970
598:3892377
512:3070323
394:Meiosis
386:meiosis
214:conidia
146:meiosis
36:species
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558:783720
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503:373162
500:
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202:carbon
142:tetrad
120:tetrad
833:S2CID
737:S2CID
554:S2CID
390:ascus
138:ascus
44:fungi
40:sexes
38:have
1061:ASIN
1038:ASIN
1015:PMID
939:PMID
884:PMID
825:PMID
786:PMID
729:PMID
686:PMID
660:mBio
638:ISBN
622:ISBN
603:PMID
546:PMID
508:PMID
459:ISSN
303:and
220:and
204:and
77:and
1005:PMC
997:doi
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966:doi
929:PMC
919:doi
874:PMC
864:doi
817:doi
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776:PMC
768:doi
721:doi
709:457
676:PMC
668:doi
593:PMC
585:doi
538:doi
498:PMC
490:doi
451:doi
293:Sex
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