337:). 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
397:
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.
310:
341:). 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.
314:
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.
349:
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)
396:
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
313:
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
124:
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
83:) 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 (
220:
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
344:
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
157:) 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
608:
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.
152:
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
275:
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
332:
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
350:
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
392:
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.
250:, 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.
119:
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,
893:
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).
377:. 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
137:, 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.
373:. 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
103:
144:
populations clonal reproduction and a type of “self-fertilization” (in the form of intratetrad mating) predominate. Ruderfer et al. analyzed the ancestry of natural
268:
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.
189:, 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
643:
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).
324:
is heterothallic. Sexual fruiting bodies (perithecia) can only be formed when two mycelia of different mating type come together. Like other
205:(2–3 μm) that readily become airborne. A. fumigatus possesses a fully functional sexual reproductive cycle that leads to the production of
692:
O'Gorman CM, Fuller H, Dyer PS (January 2009). "Discovery of a sexual cycle in the opportunistic fungal pathogen
Aspergillus fumigatus".
362:
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.
517:
Ruderfer DM, Pratt SC, Seidel HS, Kruglyak L (September 2006). "Population genomic analysis of outcrossing and recombination in yeast".
745:"Low genetic variation and no detectable population structure in aspergillus fumigatus compared to closely related Neosartorya species"
46:
In heterothallic fungi, two different individuals contribute nuclei to form a zygote. Examples of heterothallism are included for
839:
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).
125:
closely related yeast cells for two reasons. The first is that cells of opposite mating type are present together in the same
896:"Clonality despite sex: the evolution of host-associated sexual neighborhoods in the pathogenic fungus Penicillium marneffei"
630:
614:
365:
After formation of the ascus-initial cell, the ‘A’ and ‘a’ nucleus fuse with each other to form a diploid nucleus (see
257:, suggesting that production of genetic variation may contribute to the maintenance of heterothallism in this species.
385:
is an essential part of the life cycle of all sexually reproducing organisms, and in its main features, meiosis in
562:"Heterothallism in Saccharomyces cerevisiae isolates from nature: effect of HO locus on the mode of reproduction"
945:
Westergaard M, Mitchell HK (1947). "Neurospora. Part V. A synthetic medium favoring sexual reproduction".
225:, above, a short-term benefit of meiosis may be the key to the adaptive maintenance of sex in this species.
560:
Katz Ezov T, Chang SL, Frenkel Z, Segrè AV, Bahalul M, Murray AW, Leu JY, Korol A, Kashi Y (January 2010).
148:
strains and concluded that outcrossing occurs only about once every 50,000 cell divisions. Thus, although
793:
354:). This binuclear cell initiates ascus formation and is called an “ascus-initial” cell. Next the two
973:
31:
that reside in different individuals. The term is applied particularly to distinguish heterothallic
115:
48:
427:
1073:
173:
76:
is given in some detail, since similar life cycles are present in other heterothallic fungi.
62:
52:
701:
8:
841:"Sexuality generates diversity in the aflatoxin gene cluster: evidence on a global scale"
277:
40:
705:
998:
958:
922:
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867:
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769:
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586:
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56:
491:
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1049:
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927:
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813:
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717:
674:
626:
610:
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577:
534:
496:
447:
443:
359:
320:
154:
130:
68:
825:
358:
cells on either side of the first ascus-forming cell fuse with each other to form a
993:
985:
954:
917:
907:
862:
852:
805:
764:
756:
729:
709:
664:
656:
645:"Identification and characterization of an Aspergillus fumigatus "supermater" pair"
581:
573:
526:
486:
482:
478:
439:
182:
84:
546:
989:
912:
857:
406:
760:
309:
240:
1067:
451:
426:
Billiard, S.; LóPez‐Villavicencio, M.; Hood, M. E.; Giraud, T. (June 2012).
931:
876:
817:
778:
721:
678:
595:
538:
428:"Sex, outcrossing and mating types: unsolved questions in fungi and beyond"
1007:
660:
625:
Elvira Hörandl (2013). Meiosis and the
Paradox of Sex in Nature, Meiosis,
500:
355:
36:
713:
369:). This nucleus is the only diploid nucleus in the entire life cycle of
1053:
1030:
346:
325:
210:
35:, which require two compatible partners to produce sexual spores, from
425:
243:
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809:
530:
247:
206:
202:
198:
194:
246:
in crops worldwide. It is also an opportunistic human and animal
382:
374:
134:
24:
253:
Sexuality generates diversity in the aflatoxin gene cluster in
190:
102:
378:
126:
32:
516:
177:, is a heterothallic fungus. It is one of the most common
559:
467:"Life cycle of the budding yeast Saccharomyces cerevisiae"
892:
281:
94:
28:
691:
260:
164:
838:
742:
642:
140:
Katz Ezov et al. presented evidence that in natural
944:
228:
299:
1025:. Oxford, UK: Blackwell Scientific Publications.
1065:
971:
791:
974:"Sexual development genes of Neurospora crassa"
197:recycling. Colonies of the fungus produce from
1043:
743:Rydholm C, Szakacs G, Lutzoni F (April 2006).
1020:
832:
785:
464:
972:Nelson MA, Metzenberg RL (September 1992).
965:
794:"Sexual reproduction in Aspergillus flavus"
736:
685:
636:
553:
181:species to cause disease in humans with an
512:
510:
458:
288:by a short-term benefit of meiosis, as in
18:Sexes that reside in different individuals
997:
921:
911:
866:
856:
768:
668:
585:
490:
308:
101:
888:
886:
602:
507:
366:
351:
338:
334:
133:of cells directly produced by a single
79:Certain heterothallic species (such as
1066:
1048:. New York, NY: John Wiley and Sons.
792:Horn BW, Moore GG, Carbone I (2009).
883:
389:seems typical of meiosis generally.
72:. The heterothallic life cycle of
13:
959:10.1002/j.1537-2197.1947.tb13032.x
14:
1090:
578:10.1111/j.1365-294X.2009.04436.x
444:10.1111/j.1420-9101.2012.02495.x
1044:Wagner RP, Mitchell HK (1964).
1037:
1014:
938:
432:Journal of Evolutionary Biology
201:thousands of minute grey-green
619:
483:10.1128/MMBR.52.4.536-553.1988
465:Herskowitz I (December 1988).
419:
1:
1021:Fincham J RS, Day PR (1963).
412:
913:10.1371/journal.ppat.1002851
858:10.1371/journal.ppat.1003574
633:, InTech, DOI: 10.5772/56542
129:, the sac that contains the
7:
761:10.1128/EC.5.4.650-657.2006
400:
271:Henk et al. concluded that
39:ones, which are capable of
10:
1095:
990:10.1093/genetics/132.1.149
947:American Journal of Botany
239:is the major producer of
116:Saccharomyces cerevisiae
107:Saccharomyces cerevisiae
97:Saccharomyces cerevisiae
49:Saccharomyces cerevisiae
43:from a single organism.
1046:Genetics and Metabolism
315:
110:
81:Neurospora tetrasperma
661:10.1128/mBio.00234-11
367:figure, top of §
352:figure, top of §
339:figure, top of §
335:figure, top of §
312:
284:may be maintained in
263:Talaromyces marneffei
174:Aspergillus fumigatus
167:Aspergillus fumigatus
105:
63:Penicillium marneffei
53:Aspergillus fumigatus
318:The sexual cycle of
714:10.1038/nature07528
706:2009Natur.457..471O
296:, discussed above.
278:genetic variability
41:sexual reproduction
316:
231:Aspergillus flavus
111:
85:intratetrad mating
57:Aspergillus flavus
631:978-953-51-1197-9
302:Neurospora crassa
155:genetic diversity
69:Neurospora crassa
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672:
655:(6): e00234–11.
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438:(6): 1020–1038.
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183:immunodeficiency
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1038:
1023:Fungal Genetics
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891:
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851:(8): e1003574.
837:
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749:Eukaryotic Cell
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700:(7228): 471–4.
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360:binucleate cell
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19:
12:
11:
5:
1092:
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984:(1): 149–162.
964:
937:
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831:
810:10.3852/09-011
784:
735:
684:
635:
618:
615:978-0306472619
601:
552:
531:10.1038/ng1859
525:(9): 1077–81.
506:
471:Microbiol. Rev
457:
417:
416:
414:
411:
410:
409:
402:
399:
387:N. crassa
371:N. crassa
330:N. crassa
321:N. crassa
304:
300:Life cycle of
298:
280:is produced.
265:
261:Life cycle of
259:
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229:Life cycle of
227:
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165:Life cycle of
163:
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95:Life cycle of
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572:(1): 121–31.
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540:
536:
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528:
524:
520:
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511:
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477:(4): 536–53.
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290:S. cerevisiae
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207:cleistothecia
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200:
199:conidiophores
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159:S. cerevisiae
156:
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150:S. cerevisiae
147:
146:S. cerevisiae
143:
142:S. cerevisiae
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122:S. cerevisiae
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22:Heterothallic
16:
1074:Reproduction
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1016:
981:
977:
967:
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946:
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903:
899:
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804:(3): 423–9.
801:
797:
787:
755:(4): 650–7.
752:
748:
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687:
652:
648:
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621:
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370:
364:
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329:
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294:A. fumigatus
293:
289:
286:T. marneffei
285:
273:T. marneffei
272:
270:
267:
262:
254:
252:
241:carcinogenic
236:
235:
230:
222:
218:A. fumigatus
217:
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187:A. fumigatus
186:
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121:
114:
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106:
96:
80:
78:
73:
67:
61:
47:
45:
21:
20:
15:
953:: 573–577.
900:PLOS Pathog
845:PLOS Pathog
356:uninucleate
326:ascomycetes
223:S. cereviae
179:Aspergillus
37:homothallic
1068:Categories
1054:B00BXTC5BO
1031:B000W851KO
519:Nat. Genet
413:References
347:ascogonium
244:aflatoxins
211:ascospores
113:The yeast
798:Mycologia
566:Mol. Ecol
452:1010-061X
255:A. flavus
237:A. flavus
216:Although
89:automixis
74:N. crassa
1079:Mycology
978:Genetics
932:23055919
877:24009506
826:20648447
818:19537215
779:16607012
722:19043401
679:22108383
596:20002587
539:16892060
401:See also
248:pathogen
195:nitrogen
1008:1356883
999:1205113
923:3464222
868:3757046
770:1459663
730:4371721
702:Bibcode
670:3225970
587:3892377
501:3070323
383:Meiosis
375:meiosis
203:conidia
135:meiosis
25:species
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694:Nature
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629:
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584:
547:783720
545:
537:
499:
492:373162
489:
450:
191:carbon
131:tetrad
109:tetrad
822:S2CID
726:S2CID
543:S2CID
379:ascus
127:ascus
33:fungi
29:sexes
27:have
1050:ASIN
1027:ASIN
1004:PMID
928:PMID
873:PMID
814:PMID
775:PMID
718:PMID
675:PMID
649:mBio
627:ISBN
611:ISBN
592:PMID
535:PMID
497:PMID
448:ISSN
292:and
209:and
193:and
66:and
994:PMC
986:doi
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918:PMC
908:doi
863:PMC
853:doi
806:doi
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757:doi
710:doi
698:457
665:PMC
657:doi
582:PMC
574:doi
527:doi
487:PMC
479:doi
440:doi
282:Sex
185:.
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681:.
659::
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