FGSC #8110

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Reporting Genes: leu-3 cyt-1 a[m33]

Species: crassa

Allele: R156, C115, m33

Alternate Strain Number: 1840

Depositor: DDP

Linkage Group: IL

Mating Type: a

Species Number: 10

Opposite Mating Type: 8109

Deposit Sheet ↗

Genes

Locus	Cultural Requirements	Link Group	Type
a^m33	IL. Between un-3 (0.04 to 0.1%) and un-16 ( < 1%) (488, 758; D. D. Perkins, unpublished data). (609) Opposite mating types are essential for a complex of events associated with sexual reproduction and morphogenesis: attraction of trichogyne to cells of opposite mating type (39, 93); pickup and transport of the nucleus to the ascogonium; growth and development of the perithecium; proliferation of heterokaryotic ascogenous hyphae; conjugate nuclear divisions in precrozier and crozier cells; karyogamy. Mating type alleles also act as vegetative incompatibility genes during the vegetative phase. A+a combinations are unable to form stable heterokaryons (66, 384, 830, 914). Vegetative fusion is usually followed by cell death (384), but some A+a heterokaryons grow slowly (252, 412, 422). Heterozygous A/a duplications are highly abnormal, with inhibited growth and spider-like morphology (761. 804). Incompatibility in heterokaryons or duplications is relieved by spontaneous deletion of either allele (252, 756). Vegetative incompatibility is not expressed during the sexual phase after fertilization. Both manifestations of vegetative incompatibility are suppressed by tol, but sexual compatibility is not affected (755). The vegetative incompatibility is normally suppressed in N. tetrasperma (668) and N. sitophila (674, 804). Extensive efforts have failed to separate the sexual and vegetative traits by genetic recombination (758). Null mutants selected by loss of vegetative incompatibility usually lose both sexual and vegetative functions simultaneously (one exception), and both functions are usually restored simultaneously in revertants selected for restoration of fertility (one null mutant gives atypical revertants) (252, 411, 412).Only two mating type alleles, A and a, are known. These are apparently homologous throughout the genus Neurospora (820) and perhaps in related genera (770). Nothing is known about the genetics of the five true-homothallic species of Neurospora, which closely resemble N. crassa in karyotype and meiotic behavior, including the fusion of two haploid nuclei in the penultimate cell of the crozier to form the zygote nucleus (855). In the early literature, A was called + (plus) or A, and a was called - (minus) or B (e.g., reference 286). The locus may also be designated mt, mating type (e.g., reference 808), and is usually referred to as mt in the present paper.	IL	B
cyt-1	IL. Between leu-3 (5 to 8%) (583) and T(OY321) (D.D. Perkins, N.B. Raju, and E.G. Barry, in preparation). (694) Deficient in cytochromes aa3 and b. Very slow growth. Female sterile (87, 694). Scoring aided by slower growth on complete medium relative to that on minimal, presumably owing to inhibition by yeast extract (694, 816). cyt-U-9 is linked and may be allelic with the original cyt-1 mutation C115 (87; H. Bertrand, personal communication).	IL	B
leu-3	IL. Right of the In(OY323) left breakpoint and nit-2 (12 to 18%). Left of cyt-1 (5 to 8%) and T(OY321) (57, 816, PB; D.D. Perkins, N.B. Raju, and E.G. Barry, in preparation). (868)Requires leucine (867, 868). Regulatory mutation; prevents synthesis of alpha-isopropylmalate isomerase and beta-isopropylmalate dehydrogenase and prevents full derepression of alpha-isopropylmalate synthetase; also involved in regulation of isoleucine and valine synthesis, q.v. (427, 771, 833) (Fig. 15). The original allele, 47313, is leaky, but some other alleles, e.g., R156, are not.	IL	B