Neurospora mutants beginning with M through O

Meiotic (mei)
Methionine (met)
Morphological (mo)
Methyl tryptophan resistant
Mutagen sensitive (mus)
Nicotinic acid (nic)
Nitrate non-utilization (nit)
Nuclease (nuc)
Osmotic (os)

m: microconidial
Allelic with pe, q.v.

ma-1: malate utilization-1
Unmapped. Probably in a left arm, any of III to VII.

Unable to use malate as a carbon source when the tricarboxylic acid cycle is blocked by a suc (pyruvate carboxylase) mutation. Altered mitochondrial malate dehydrogenase. Scorable only in suc mutants (703, 706, 709).

ma-2: malate utilization-2
Unmapped. Unlinked to ma-1. Probably in a left arm, any of III to VII.

Unable to use malate as a carbon source when the tricarboxylic acid cycle is blocked by a suc (pyruvate carboxylase) mutation. Altered mitochondrial malate dehydrogenase. Scorable only in suc mutants (703, 706, 709).

mac: methionine-adenine-cystine
Probably allelic with met-6, q.v., but there are some differences between them. Requires methionine. Growth on methionine is stimulated by adenine with possible additional stimulation by cystine. Inhibited by guanine (290). One occurrence: allele 65108.

mat: mat
IVR. Right of pyr-2 (3%). Left of the T(NMI52) right breakpoint and cys-4 (10%) (633, 721,812).

Spreading colonial morphology, with conidiating tufts. Grows better on sucrose minimal medium than on glycerol complete medium (789).

Mating type
See A/a.

mb-1: male barren-1
VII. Linked to nic-3 and wc-1 (23%) (1100, PB).

Perithecial development is blocked when the mb-1 mutant is used as the male parent to fertilize an mb+ female: many perithecia are produced, mostly small, brown, without beaks or ascospores; a few perithecia mature and produce ascospores (1100). Perithecia are reported to be normal and fertile when the mb-1 mutant is the female parent fertilized by an mb+ strain (1128); however, some abnormality as the female has been observed cytologically after pachytene (N.B. Raju, personal communication). Homozygous barren (PB). Recessive in heterokaryons, complementing mb-2 and mb-3 (1101). One occurrence: allele 8455.

mb-2: male barren-2
IR. Between cyh-1 (5%) and al-1 (7%) (PB). (1100)

Perithecial development is blocked when the mb-2 mutant is used as the male parent to fertilize an mb+ female; many perithecia are produced, mostly small, brown, without beaks or ascospores; a few perithecia mature and produce ascospores (1100). Perithecia are normal and fully fertile when the mb-2 mutant is used as the female parent and fertilized by an mb+ strain (1128). Homozygous barren (PB). Recessive in heterokaryons, complementing mb-1 and mb-3 (1101). One occurrence: allele 8553.

mb-3: male barren-3
IR. Linked to cyh-1 (18%), al-1 (2%), and mb-2 (6%) (1100, PB; J.F. Leslie, personal communication).

Perithecial development is blocked when an mb-2 mutant is used as the male parent to fertilize an mb+ female; many perithecia are produced, mostly small, brown, without beaks or ascospores; a few perithecia mature and produce ascospores (1100). Perithecia are normal and fully fertile when an mb-2 mutant is used as the female parent and fertilized by an mb+ strain (1128). Development of perithecia may be slower than normal, however, when an mb-2 mutant is used as the female (N.B. Raju, personal communication). Homozygous barren (PB). Recessive in heterokaryons, complementing mb-1 and mb-3 (1101). Six occurrences.

mbic
See Bml.

md: mad
VR. Between sh (3%) and sp (9%) (296).

Spreading morphological which modifies the banding phenotype of cl. Characteristic branching pattern. Photographs. (296)

me: methionine
Changed to met.

mea-1: methylammonium resistant
Unmapped.

Presumed defective in transport of ammonium (293). nit-2;mea-1 double mutants show nitrogen-starved growth on ammonium (R.H. Garrett, personal communication).

med. medusa
IVR. Linked to met-5 (5%) and pan-1 (8%) (382).

Slow growing, spreading, morphological mutant, with distinctive grooves on the agar surface (382). For a photograph, see Fig. 17 of reference 382. Reduced amount of cell wall peptides (1165).

mei: meiotic
Meiosis impaired. In addition to partial or complete blocks of meiosis and ascus development, some mutations designated mei have effects that may include sensitivity to radiation, to radiomimetic drugs, and to histidine and increased duplication instability. Both recessive and dominant meiotic mutations are known. Mutations that affect meiotic or premeiotic events may have other names, depending on the phenotype first recognized. See: asc; fmf-1; mb; mus-7, -8, -9, and -11; uvs-3, -5, and -6. Meiotic mutants are very common in natural populations of N. crassa (601).

mei-1: meiotic-1
IVR. Linked to arg-2 (<1%), probably to the right (995).

Meiosis is impaired in homozygous crosses. Recessive. Meiotic divisions occur and many ascospores are produced, but 70 to 90% are inviable and white. The viable ascospores are usually disomic for one or more linkage groups, indicating high nondisjunction at the first division (254, 995). Chromosome pairing is defective: axial elements of synaptonemal complex are present, but a completed complex is rarely seen. Separation at anaphases I and II is defective, leading to four-poled second and third division spindles (625). Not sensitive to UV, methyl methane sulfonate, ionizing radiation (939), or histidine (939; D. Newmeyer, unpublished data). mei-1 is present in wild-collected strain Abbott 4A (995), which is an ancestor of many Beadle and Tatum mutants (68). Possible allele asc(DL243) complements mei-1 but did not recombine with it (0/3,000) (253). DL243 and mei-1 strains differ phenotypically. In DL243 mutants, the major block is before karyogamy; the few asci produced have normal meiosis I but high nondisjunction at meiosis II, with most chromosomes usually attached to only one spindle-pole body (254). Possible allele asc(DL95) complements mei-1 and asc(DL243), but did not recombine with DL243 (0/96) (253). DL95 is phenotypically like mei-1 but is less extreme (254).

Mei-2: Meiotic-2
VR. Linked near inl (995). Between al-3 (20 and his-6 (A.L. Schroeder, personal communication).

Meiotic divisions occur, and many ascospor are produced, but many are inviable and white. Crosses heterozygous or homozygous for Mei-2 give extensive nondisjunction of all linkage groups (995). Chromosome pairing much reduced (B.C. Lu, cited in reference 995). Sensitive to methyl methane sulfonate, histidine, and gamma rays (939). Dominant in the original strain (995), but progeny show incomplete penetrance (939).

mei-3: meiotic-3
IL. Right of arg-1 (3%). Probably right of eth-1 (1%) and arg-3 (1%). Left of the T(39311) right breakpoint; hence, left of the centromere and sn (757, 808).

Homozygous barren (757). Recessive. Blocks meiosis in zygotene (860). Sensitive to UV, histidine (757, 759), mitomycin C (195), ionizing radiation, and methyl methane sulfonate (939). Sensitivity to UV and histidine is temperature sensitive; best scored at 39 C, at least for strains carrying allele N289 (757). Causes increased duplication instability (mitotic recombination, deletion, or both) (757).

mei-4: meiotic-4
IIIR. Linked to leu-1 (12%), probably to left (757).

Homozygous barren. Recessive. Highly variable expression, depending on genetic background (757). Crosses with more extreme genotypes are blocked at crozier formation or karyogamy (860). Crosses with less extreme genotypes complete normal first division but become irregular at later divisions, producing abnormal spores (B.C. Lu and D.R. Galeazzi, cited in reference 860). Not sensitive to UV, methyl methane sulfonate, or gamma rays in spot tests, or to histidine (757, 939).

mel-1: melon-1
VIIL. Left of thi-3 (27%) (819). Growth as hemispherical colonies, similar to those of the mutant bal (717). Growth stimulated rather than depressed by sorbose (715). Cell wall analysis (278). Photographs (278, 717). Called col(C-L2b). Not tested by crossing to possible allele do.

mel-2: melon-2
Allelic with bal, q.v. (812).

mel-3: melon-3
Linked to leu-1 (17%) (717).

Growth as hemispherical colonies similar to those of the mutant bal. Photographs. A separate modifier gene is also located in linkage group III. (717)

Mepr: methylpurine resistant
See mep.

mep(3): methylpurine resistant
Not mapped. Segregates 1:1.

Resistant to 6-methylpurine. Adenine phosphoribosyltransferase activity near normal in vitro. Uptake is normal. 6-Methylpurine prevents purple pigment production by ad-3 single mutants on low adenine concentrations, but it does not prevent pigment production by the ad3A;mep(3) double mutant, suggesting that mep(3) results in an alteration in the regulation of de novo purine synthesis. Has low hypoxanthine phosphoribosyltransferase activity, as do mep(10) and ad-8 mutants, q.v. Selected on 1 mM 6-methylpurine-sorbose medium (785). Phenotype consistent with lowered affinity of glutamine amidotransferase for 6-methylpurine as a feedback inhibitor (788). Not tested for allelism with mep(10) or with ad mutations. Called Mepr-3, but not indicated to be dominant (785). Called mep-1 by Barratt and Ogata (51).

mep(10): methylpurine resistant
Not mapped. Segregates 1:1.

Resistant to 6-methylpurine. Adenine phosphoribosyltransferase activity is negligible in vitro. Adenine uptake is normal. Resistance may result from inability to convert the analog to nucleotide form. Has low hypoxanthine phosphoribosyltransferase activity, as do the mutants mep(3) and ad-8, q.v. Selected on 1 mM 6-methylpurine-sorbose medium. Not tested for allelism with mep(3). Called Mepr-10, but not indicated to be dominant. (785) Called mep-2 by Barratt and Ogata (51).

met: methionine
Auxotrophs designated met require methionine, and some can use its immediate precursors, homocysteine and cystathionine; they cannot use cysteine. (Mutants able to use cysteine as well as methionine are designated cys.) For the methionine biosynthetic pathway, see Fig. 17. For a review, see reference 351. For regulation, see individual loci and reference 965. Formerly called me.

FIG. 17. Biosynthetic pathways of homoserine, threonine, and methionine, showing sites of gene action (124, 208, 209, 351, 352, 518, 547, 965). For conversion of threonine to isoleucine, see Fig. 15. H4PteGlu, Tetrahydrofolate. It is not clear whether the polyglutamylation step controlled by met-6 occurs only at the stage shown.

met-1: methionine-1
IVR. Right of oxD (3%) and the T(S1229) left breakpoint. Left of col-4 (4%) (55, 158, 718, 768, 808).

Uses methionine but not homocysteine (469) (Fig. 17). Lacks methylene tetrahydrofolate reductase and, thus, lacks the coenzyme needed for transmethylating homocysteine (124, 963, 964). A report that the mutant met-1 also lacks cystathionine-gamma-synthase (547) proved incorrect; the error resulted because methyl tetrahydrofolate is an essential activator of cystathionine-gamma-synthase (965). Methylene tetrahydrofolate reductase is feedback-inhibited by S-adenosylmethionine (124). Used in heteroallelic duplications from T(S1229) to assay mitotic recombination (56).

met-2: methionine-2
IVR. Between trp-4 (6%) and pan-1 (4%) (719). Linked to ilv-3 (0/129) (354, 579).

Uses methionine or homocysteine; accumulates cystathionine (469). Lacks cystathionase II (353) (Fig. 17). Fine-structure map (720, 724). Complementation map (719). Used in major studies of intralocus recombination and its polarity (720, 724).

met-3: methionine-3
VR. Right of trp-5 (4%) and pab-1 (1%). Left of pk (1%) (6, 296, 362, 1036). (125)

Uses methionine, homocysteine, or cystathionine (469). Lacks cystathionine-gamma-synthase (547) (Fig. 17). This enzyme is also lacking in the mutant met-7 (547). The enzyme is activated by methyl tetrahydrofolate and feedback inhibited by S-adenosylmethionine (547, 965).

met-4: methionine-4
Changed to cys-10, q.v. (721).

met-5: methionine-5
IVR. Between his-4 (4%) and nit-3 (15%) (812, PB). (125)

Uses cystathionine, homocysteine, or methionine (354, 718). Defective homoserine transacetylase (547, 733) (Fig. 17).

met-6: methionine-6
IR. Right of T(NM103), T(ALS182), and thi-1 (7 to 14%) (808, 1091, PB). Left of ad-9 (2 to 16%) (466, 723, 789). Adjoining or allelic with mac (722, 724). (125)

Requires methionine; does not use precursors (718; N. H. Horowitz, cited in reference 1180). Strain(s) carrying allele 35809 lacks polyglutamate forms of folate and, thus, apparently lacks the coenzyme needed for transmethylating homocysteine (208, 886, 963, 964) (Fig. 17). An incorrect report that the mutant met-6 also lacks cystathionine-gamma-synthase (547) proved to be due to the methyl tetrahydrofolate being removed during preparation of extracts; methyl tetrahydrofolate is an activator of cystathionine-gamma-synthase (965). The relationships between met-6 (35809) and its probable alleles met (S2706) and mac (65108) are not clear. met (S2706) and mac both complement met-6 (35809), but do not complement each other, indicating that at least met (S2706) and mac are alleles. In a high-resolution recombination study with flanking markers, met-6 (35809) and met (S2706) behaved like alleles, but mac behaved atypically, although almost equally closely linked (724). The mac mutant is reported to differ from the others in causing an accessory requirement for adenine and possibly cystine (290), whereas met-6 (35809) and met (S2706) strains are stimulated by adenine only in a CO2-enriched atmosphere (G. Roberts, cited in reference 724). mac and met-6 (35809) strains evidently lack different folylpolyglutamate synthetase activities (208, 886). Used to study polarity in intralocus recombination (722, 724). Polarity with respect to flanking markers is not reversed when the met-6 region is inverted relative to the centromere (722).

met-7: methionine-7
VIIR. Right of qa-2 (<1%), ars (<1%), and the centromere (one second-division ascus in several hundred). Left of met-9 (10[-4]) and wc-1 (1 to 4%) (146, 725; M.E. Case, personal communication). (718; M.K. Allen, cited in references 718 and 789)

Uses cystathionine, homocysteine, or methionine (718; N. H. Horowitz, cited in reference 1180). Lacks cystathionine-gamma-synthase (547) (Fig. 17). This enzyme is also lacking in the mutant met-3 (547). See met-3 for regulation. Apparently contiguous with met-9 by coconversion. Flanking markers are recombined in most met-7+ met-9+ recombinants (725). Functionally distinct from the mutant met-9, which has active cystathionine-gamma-synthase (547) but cannot use homocysteine. No mutants lacking both functions have been isolated. Allele NM251 is suppressible by supersuppressor RN33 (same as ssu-1?) (725). Allele K79 is inseparable from reciprocal translocation T(I;VII)K79 (808).

met-8: methionine-8
IIIR. Between ff-5 (1 to 4%) and ad-4 (4%) (219, 815,1052). (718)

Uses methionine but not precursors (718). Lacks methyl tetrahydrofolate homocysteine transmethylase (124, 964) (Fig. 17).

met-9: methionine-9
VIIR. Between met-7 (10[-4]) and wc-1 (1 to 2%) (725). (815)

Requires methionine; cannot use precursors (290, 718, 725). Apparently contiguous with met-7, q.v. (725). Functionally distinct from met-7. The mutant met-9 retains the met-7+ function, producing cystathionine-gamma-synthase (547). Allele NM43 is heat sensitive (725).

met-10: methionine-10
IR. Near lys-4. Right of nuc-1, T(AR173), and his-2. Left of his-3 and ad-3 (757, 808; R.L. Metzenberg, personal communication). (P. Dodd, cited in reference 816)

Requires methionine. The only known allele is heat sensitive, with the requirement at 34 C, not at 25°C (816; P. Dodd, cited in reference 816); does not grow at 39°C even with methionine (757).

meth: methionine
Changed to met.

methionine overproduction
See eth-1 (542).

[mi-1]: maternal inheritance-1 (synonym: [poky])
Mitochondrial mutant with slow growth and deficient cyanide-sensitive respiration (see reference 394). See su([mi-1]).

Microconidiation genotypes
Microconidia, being uninucleate, are valuable for such applications as somatic analysis and mutagenesis. They are much less abundant in the wild type than are multinucleate macroconidia, except under certain conditions (893). Several genotypes are known that increase the production of microconidia, notably, pe and dn, but these single-mutant strains also continue to produce macroconidia. A few microconidia, and no macroconidia, are produced by the single mutant strains fl and cpt, q.v.; large numbers can be obtained from fl strains under certain conditions (893). Large numbers of almost exclusively uninucleate microconidia can be obtained by using the double mutants pe fl or dn;fl, in which fl blocks macroconidiation and the pe or dn component promotes microconidiation. dn;fl strains have the advantage over pe fl strains of greater fertility in homozygous crosses (806), but microconidia from dn;fl strains are less viable (454). Cultures abundantly producing only microconidia appear grey-brown rather than orange. See fl, dn, and pe. For colonial microconidiating strains, see col-1, col-4. See references 415 and 416 for other gene interactions.

mig: migration of trehalase
IR. Between met-6 (7%) and al-2 (20%). Between tre (<<1%) and ad-9 (1045, 1176).

Altered electrophoretic mobility of trehalase (1045). Putative trehalase structural gene (1047). (However, see qualifications in reference 1176.) Polymorphic in laboratory stocks of N. crassa and in wild isolates of N. intermedia (1176). The adjoining mutant gene tre results in production of a protein inhibitor of trehalase (1045).

mo: morphological
Name and symbol used by Garnjobst and Tatum (382) for a miscellaneous group of mutants having spreading growth on agar, sometimes with scanty or fine hyphae and reduced conidiation. The symbol morph has also been used. Other categories of morphological mutants were designated col, spco, or smco. Other workers have assigned descriptive names, e.g., bal, fr, ro, and sc. See also moe. For reviews covering morphological mutants and morphogenesis, see references 112, 197, 642, 675, 942, 946, and 1088. Growth rates and hyphal diameters of 18 morphological mutants are given in reference 197.

mo-1: morphological-1
I. Linked mating type (9%) (382).

Altered morphology. Slow growth from ascospores (382).

mo-2: morphological-2
VII. Linked to nt (29%) and for (16%) (382, PB).

Slow growing, poorly pigmented mycelium. No conidia. Poor recovery from ascospores (PB).

mo-3: morphological-3
See sk.

mo-4: morphological-4
IIIR. Right of leu-1 (8%). Linked to pro-1 (10%) (382). (F.J. Doe, personal communication)

Altered morphology. Conidiates throughout slant. Complements col-14, col-16, and spg (382).

mo-5: morphological-5
I. Linked mating type (20%) (382).

Few conidia. May make exudate on slant (382).

mo(KH160)
See shg: shaggy.

mo(P1163)
See dr: drift.

mo(P2402t)
See un-20.

mod-5: modifier of permeability
VI. Linked to trp-2, near the centromere (3%) (909).

Improves growth of trp-1, trp-2, trp-3, trp-4, aro-1, tyr-1, tyr-3, pt, met-7, and pyr-1 strains on complex media. Increases sensitivity to 4-methyltryptophan and p-fluorophenylalanine. Recessive in heterokaryons. Attributed to permeability change that facilitates entry of metabolites (53, 909). Scorable on slants of minimal medium plus 4-methyl-DL-tryptophan (0.9 mg/ml, autoclaved; tests read at 7 days 34 C) (PB). Map location similar to that of mts, but not tested for allelism. mts differs in not allowing the mutant pyr-1 (H263) to grow on complex media (160). (Locus symbols mod-1, -2, -3, and -4 have not been used.)

mod(sc): modifier of scumbo
IV. Linked to pan-1 (17%) (497).

Restricts the growth of sc but not of four other morphological mutants (cr-1, fr, bis, sp) or of the wild type (497).

moe-1: morphological, environment sensitive-1
Probably allelic with sk, q.v. VII. Linked to nt (12 to 19%) (382), probably to the right (PB).

Morphology identical to that of sk mutants; linkage similar (PB). Morphology reported influenced by temperature and medium: more spreading on minimal or complete medium at 25 C; zoned growth at 34°C on complete (382). Temperature effect could be due to scot, the presence of which in the strain of origin was not recognized. Photographs of strain R2408: Fig. 19 through 22 in reference 382. Reduced amount of cell wall peptides (1165).

moe-2: morphological, environment sensitive-2
VI. Linked to trp-2 (14%), probably to the left (382).

Grows with concentric zones on minimal medium and as restricted colonies on glycerol complete medium (34 C). Photographs of strain R2532: Fig. 23 and 24 in reference 382. The scot mutation may have been present in the strain of origin.

moe-3: morphological, environment sensitive-3
IV. Left of pan-1 (17 to 25%) and bd (18%) (929).

Blocks conidial germination at high temperature. Colonial at high temperature if on dialysis tubing on agar surface, but fairly normal vegetative growth if submerged. Strong circadian conidiation rhythm at low temperature (929). Effect on conidial germination (but not on vegetative growth) counteracted by high conidial concentration or C02 (190, 929). Histidine is stimulatory, but there is disagreement as to whether it affects germination or vegetative growth (929; G.W. Charlang, personal communication). Partially curable by siderophores (ferricrocin). Conidia rapidly lose siderophores on contact with aqueous medium, even at permissive temperatures, suggesting an alteration in the plasma membrane attachment site (190). Called JS134-9.

morph: morphological
Symbol changed to mo.

mt: mating type
See A/a. Also used as a symbol for mtr.

mtr: methyltryptophan resistant
IVR. Between pdx-1 (2%) and col-4 (1%) (101, 1017).

Resistant to 4-methyltryptophan and p-fluorophenylalanine. pmn (= Pm-N, pm n), selected by resistance to p-fluorophenylalanine, has been shown to be alletic with mtr (R. Sadler and S. Ogilvie-Villa, personal communication; see also reference 248). Defective in transport of neutral aliphatic and aromatic amino acids via amino acid transport system I (as defined in reference 777) (248, 602, 1017, 1152). Causes an alteration in surface glycoproteins (1038). Used extensively for transport studies (247a, 1150 [review], 1152), also for studies of the mechanism of intralocus recombination (1021). Resistance is recessive in duplications from T(S1229) (PB). Recessive resistance used in a heterokaryon test system for mutation studies (1020). Suppressors obtained and used for selecting other resistance mutants (106, 107, 555, 1018). Allele 26 is a putative frameshift mutation reverted by ICR170 (106, 107). mtr ascospores are slow to darken and mature; up to 50% of the young ascospores from heterozygous crosses are white (152, PB). With probable allele MN18, ascospore viability is improved by the addition of peptone to the crossing medium when the male parent is added (152). mtr has been scored on media containing 10 or 70 µg of filter-sterilized 4-methyltryptophan per ml or on 20 or 60 µg of p-fluorophenylalanine per ml (550, 1021, PB). Unlike 4-methyltryptophan, p-fluorophenylalanine is heat stable and can be added before autoclaving. Strains with mutations at the mtr locus may be obtained by selection for resistance to numerous agents or for defects in uptake ability. Thus, there is confusion in nomenclature. Genes originally designated neua, neur, neut, tru (628) may be mtr alleles. mtr was initially called mt (602).

mts: methyltryptophan sensitive
VIL. Right of ylo-1 (<1%) (152, 160).

Sensitive to analogs of all tested aromatic, neutral, and basic amino acids and to analogs of purines and pyrimidines. Ten to 100 times more sensitive than the wild type. Not sensitive to cold, salt, or detergent. Resembles mod-5 in enabling the mutant trp-3 (A78) to grow well on complex media, but differs in not doing so for the mutant pyr-1 (H263). No allelism test with mod-5. Obtained by filtration enrichment in the presence of 5-methyltryptophan (152, 160). Used for selection of mutants resistant to analogs: 5-methyltryptophan (152); 8-azaadenine (524). Could be useful where the wild type is not sufficiently sensitive to allow direct selection of resistant mutants. Conveniently scored on p-fluorophenylalanine (2 µg/ml, solid medium, autoclaved in medium; p-fluorophenylalanine is more heat stable than is 5-methyltryptophan). Best tested with small inocula on slants (10 by 75 mm) and read after 3 days at 34°C (PB). Called 5mt.

multicent
Linkage tester strain containing mt, bal, acr-2, pdx-1, at, ylo-1, and wc-1, which are linked to centromeres of linkage groups I through VII, respectively (800). Especially useful to establish linkages of translocations (808). Scoring of test markers is somewhat more laborious than for alcoy, which may therefore be preferred for locating point mutations.

mus: mutagen sensitive
Symbol adopted in 1980. Locus numbers begin with mus-7 to avoid confusion with uvs-1 through -6 (537, 539). Previously named mutagen-sensitive genes bearing other symbols retain their original designations in the present compilation. (See uvs-1 to -6, upr-1, Mei-2, mei-3, nuh-4, and gs.) Several new unmapped mus genes (255) are not listed separately. For properties of double mutants, see reference 539.

mus-7: mutagen sensitive-7
IIR. Between arg-5 (8 to 12%) and nuc-2 (11%) (539).

Sensitive to X rays, methyl methane sulfonate, and nitrosoguanidine, but not to UV. Extremely sensitive to histidine. Normal spontaneous, UV-induced, and X-ray-induced mutation. Homozygous barren (537, 539). Not tested for allelism with asc(DL879), which maps in same region and causes nondisjunction when homozygous.

mus-8: mutagen sensitive-8
IV. Linked to pdx-1 (6%) and mtr (1%) (537, 539; E. Kafer, unpublished data).

Sensitive to UV, X rays, methyl methane sulfonate, nitrosoguanidine, and mitomycin C. Decreased spontaneous mutation (537). Homozygous barren (539).

mus-9: mutagen sensitive-9
IR. Between cyh-1 (18%) and al-2 (6%) (537).

Sensitive to UV, X rays, methyl methane sulfonate, histidine, nitrosoguanidine, and mitomycin C. High spontaneous mutation; little or no mutability by UV or X rays. Homozygous sterile. Reduced conidial viability. (537, 539) Defective in extracellular nuclease, giving reduced halos around colony on DNA agar (537). Initially called uvs(FK104) in reference 538.

mus-10: mutagen sensitive-10
VIIR. Right of met-7 (7%) (539).

Moderately sensitive to UV and methyl methane sulfonate. Not sensitive to nitrosoguanidine or mitomycin C. Slight or no sensitivity to X rays or histidine. Homozygous fertile (although less so than the wild type). Normal spontaneous and UV- and X-ray induced mutation. (537, 539)

mus-11: mutagen sensitive-11
VR. Linked to pab-2 (539), near his-6 (E. Kafer, personal communication).

Extremely sensitive to methyl methane sulfonate and histidine; also sensitive to X rays, nitrosoguanidine, and mitomycin C (< X rays). High spontaneous mutation. Little or no mutability by UV or X rays. Homozygous barren. Reduced conidial viability (537, 539). Not allelic with Mei-2 (939).

mus(SC3): mutagen sensitive
Perhaps VI, linked to lys-5.

Sensitive to methyl methane sulfonate but not to histidine. Slow growth. Both the mycelium and conidia are sensitive. Very sensitive on methyl methane sulfonate medium, but not after treatment of conidia with methyl methane sulfonate. (255) Allelism with mus(SC10) has not been excluded.

mus(SC10): mutagen sensitive
Sensitivity cosegregates with a translocation involving linkage groups II, III, and VI.

Sensitive to methyl methane sulfonate, UV, and X rays. Sensitive to histidine at 37°C but not at 25°C. High spontaneous mutation. Female sterile. Complements uvs-4 (in IIIR) (255; A.M. De Lange, personal communication). Allelism with mus-7 (II) or uvs-5 (111) is not excluded.

mus(SC15): mutagen sensitive
V. Left of inl (10%) (255).

Highly sensitive to methyl methane sulfonate but not to histidine (255). Sensitive to X rays (A. M. De Lange, personal communication). Both the mycelium and conidia are sensitive. Very sensitive on methyl methane sulfonate medium; the effect is slight after treatment of conidia with methyl methane sulfonate (255). No allelism test with mus(SC17).

mus(SC17): mutagen sensitive
V. Left of inl (27%) (255).

Sensitive to methyl methane sulfonate but not to histidine. Sensitivity is shown by the mycelium, not by conidia, and only after preincubation at 15°C. Growth is cold sensitive on minimal medium (255).

mus(SC28): mutagen sensitive
IR. Right of al-1 (18%) (255).

Sensitive to methyl methane sulfonate. Both the mycelium and conidia are sensitive (255).

nada: NAD(P)ase
IV. Left of ad-6 (18%) (747).

NAD(P) glycohydrolase structural gene. Normal morphology. Identified by a plaque test, using Haemophilus influenzae. Recessive in heterokaryons. Allele 62ts is temperature sensitive, with altered substrate affinity. (747) Used in a study of glutamic acid decarboxylase during conidial germination (196).

nap: neutral and acidic amino acid permeability
VR. Linked to inl (15%) (516); right of ure-2 (32%) (1149).

Selected as resistant to ethionine plus p-fluorophenylalanine (516). Causes reduced amino acid uptake by neutral, basic, and general systems. Also causes reduced uptake of uridine and glucose. Defect is not in amino acid-binding glycoproteins. (865) See reference 1149 for aspartate uptake and resistance to inhibitors. Scored by spotting conidial suspension on minimal medium plus 1.5% sucrose, agar, 0.3 mM ethionine, and 0.02 mM p-fluorophenylalanine.

nd: natural death
IR. Between the centromere (15%) and al-2 (20%) (981).

Decreasing clonal growth potential under all nutritional conditions, followed by abrupt irreversible cessation of growth (707, 981). Hypersensitive to sorbose. Conidia die rapidly on slants at 4°C (707). Recessive in heterokaryons. An aged strain can be rejuvenated through heterokaryosis or by crossing to nd+. Extracts nontoxic (981). Used to examine hypotheses of senescence based on faulty protein synthesis (607) and lipid autoxidation with free-radical reactions (702). Stocks maintained in balanced heterokaryons. Initial growth rate of the original strain, 2.5 mm/h; however, nd progeny free of modifiers grow initially at 4.5 mm/h (wild-type rate) (707).

ndc-1: nuclear division cycle-1
VR. Left of arg-4 (2%) (976).

Heat-sensitive conditional mutant. Growth at 25°C but not at 34°C. Recessive. Division cycle blocked just before initiation of DNA synthesis while spindle-pole bodies are duplicated but not separated. (976) Scored as an irreparable un mutant (see un).

neu: neutral amino acid transport
See mtr.

nic: nicotinic acid
nic mutants are preferably supplemented with nicotinamide rather than nicotinic acid at most pH values because of permeability (97). nt mutants are best treated as nic mutants for purposes of growth and scoring. For good recovery of some nic mutants from crosses, crossing media should be supplemented with nicotinamide at levels higher (10X) than those required for growth, even when the protoperithecial parent is nic+ (789; P. St. Lawrence, personal communication). See Fig. 18 for the biosynthetic pathway. For regulation, see references 111, 371, 604, and 926.

nic-1: nicotinic acid-1
IR. Right of ace-3 (<1%), lys-1 (1%), and In(OY323). Left of os-1 (10 to 29%) (2, 57, 131, 578, 789, 816, 907). (482)

Uses nicotinic acid or nicotinamide, but not precursors (97, 100) (Fig. 18). Accumulates quinolinic acid (100). Used to study intralocus recombination (907). Called the q locus.

nic-2: nicotinic acid-2
IR. Between ad-3B (4%) and ace-7 (4 to 7%) (271, 578). (482)

Grows on nicotinic acid, nicotinamide, or high concentrations of quinolinic acid (97, 1168). Cannot use kynurenine, hydroxykynurenine, or hydroxyanthranilic acid (96, 1168). Accumulates 3-hydroxyanthranilic acid (96) (Fig. 18). Aging cultures accumulate red-brown pigment in the medium. Used to study intralocus recombination (908). Translocations T(4540) and T(S1325) are inseparable from nic-2 (808, 908, 911).

nic-3: nicotinic acid-3
VIIL. Right of spco-4 (1%) and do (3%). Left of thi-3 (9 to 27%) and csp-2 (16 to 22%) (539, 812, 816, PB). (M.K. Allen, cited in references 718 and 789)

Uses nicotinic acid, nicotinamide, 3-hydroxyanthranilic acid, 3-hydroxykynurenine, or high concentrations of quinolinic acid (96, 1168). Accumulates alpha-N-acetylkynurenine; blocked in conversion of kynurenine to 3-hydroxykynurenine (1168) (Fig. 18). Pyridine nucleotide levels (111).

FIG. 18. Pathway from tryptophan to nicotinic mononucleotide, showing sites of gene action (96, 100, 368, 1168). The enzymatic reactions between 3-hydroxyanthranilate and nicotinic mononucleotide have not been demonstrated directly in Neurospora.

nit: nitrate nonutilizer
Conveniently scored on synthetic crossing medium (1134), in which nitrate is the sole nitrogen source. Also scorable on slants by pH change when grown with ammonium nitrate as the nitrogen source and bromcresol purple (4 mg/ml) as an indicator (791). In most crosses, a nit mutant can be used as the fertilizing parent; in nit x nit or other crosses where it is required as the female parent, crossing medium can be altered by substituting ammonium nitrate for potassium nitrate (155). Nitrite is toxic at low pH; test media containing nitrite should be neutralized, and the nitrite should preferably be filter-sterilized (G.S. Sorger, personal communication). For a summary of nutritional requirements, based on the data of various authors, see reference 1080. nit-1, nit-7, nit-8, and nit-9 involve a molybdenum-containing cofactor common to nitrate reductase and xanthine dehydrogenase (591, 1080, 1081) (Fig. 19 and 24). For a review of nitrate assimilation, see reference 385. For regulation, see reference 643 (review), references 292, 835, 837, and 1081, and entries for nit loci, gln-1, and nmr.

FIG. 19. Nitrate reduction pathway showing sites of gene action. am only blocks the NADP-specific glutamate dehydrogenase, not the NAD-specific enzyme. (185, 293, 336, 591, 912, 999, 1081)

nit-1: nitrate nonutilizer-1
IR. Right of Tp(T54M94) and ad-9 (3 to 15%). Left of cyh-1 (6%) (466, 496, 816). (482)

Cannot use nitrate or hypoxanthine as a nitrogen source, but uses nitrite, ammonia, or amino acids (1000). Does not prevent formation or nitrate reductase apoprotein (999), but lacks the molybdenum-containing cofactor common to nitrate reductase and xanthine dehydrogenase (591, 741) (Fig. 19 and 24). The nitrate reductase in nit-1 extracts does not catalyze the complete electron transport sequence from NADPH to N03 but does catalyze the initial part of this sequence if a suitable electron acceptor (e.g., cytochrome c) is provided (999). See reference 198 for a model of interaction of nit-1 and nit-3 gene products. See references 226, 999, and 1000 for regulation.

nit-2: nitrate nonutilizer-2
IL. Right of the T(39311) left breakpoint and of un-5 (2%). Left of In(OY323) and leu-3 (12 to 18%) (57, 808, 816, PB). (335, 1135)

Cannot use nitrate, nitrite, purines, or most amino acids as a nitrogen source but will grow on ammonia, glutamine, or glutamate. nit-2+ is a major nitrogen control gene and mediates nitrogen catabolite repression. The nit-2 mutant is missing (or has severely reduced levels of) nitrate reductase, nitrite reductase, uricase, xanthine dehydrogenase, allantoinase, allantoicase, L-amino acid oxidase, general amino acid permease, extracellular protease, and an intracellular neutral phenylmethylsulfonyl fluoride-sensitive protease (227, 324, 441, 872, 1001, and references therein). Also affects levels of glutamate dehydrogenases (226) and uptake of uracil and uridine (128). Prevents leaky growth of the mutant am on minimal medium (155). The product of the nit-2 gene has been tentatively identified as a nuclear DNA-binding protein, whose affinity for DNA is reduced in the presence of glutamine (433). Allele K31 (called pink) originated in N. sitophila and was introgressed into N. crassa (335); protein product of K31 may show altered mobility (433). Recombination within the nit-2 locus is subject to regulation by rec-1 (157). Heterozygosity for closely linked ss reduces recombination within nit-2 (161). Called amr: ammonium regulation in reference 872.

nit-3: nitrate nonutilizer-3
IVR. Between met-5 (15%) and pyr-2 (2 to 9%) (1000, PB). (453)

Cannot use nitrate as a nitrogen source, but uses nitrite, ammonia, hypoxanthine, or amino acids (28, 999). Structural gene for NADPH nitrate reductase (28) (Fig. 19). Allele 14789 apparently codes for an altered enzyme that cannot catalyze the whole electron transport sequence from NADPH to N03-, but can catalyze the terminal portion of this sequence, providing that a suitable electron donor (reduced viologen dye) is provided (999). See reference 198 for a model of interaction of nit-1 and nit-3 gene products. For regulation, see references 226, 999, and 1000. The nit-3+ gene has been cloned and is expressed in Escherichia coli (989).

nit-4: nitrate nonutilizer-4
IVR. Right of pyr-1 (1 to 6%). Probably right of col-4 (2%). Left of pan-1 (6 to 27%) (1000, PB). (94)

Cannot use nitrate or nitrite as a nitrogen source, but uses ammonia and amino acids (94). Regulator for induction by nitrate of nitrate reductase and nitrite reductase (1080). Allele nr15, called nit-5 (1000), is phenotypically identical to other nit-4 alleles; shown to be allelic by failure to complement or recombine (0 prototrophs per 2,080 progeny) (1080). Original allele was discovered in a wild isolate of N. intermedia from Borneo and introgressed into N. crassa (94).

nit-5
Allelic nit-4, q.v.

nit-6: nitrate nonutilizer-6
VIL. Right of chol-2 (6%). Left of ser-7 (10%) and ad-8 (17%) (PB; O.C. Yoder, personal communication).

Unable to use nitrate or nitrite as a nitrogen source (185). Lacks nitrite reductase (185) (Fig. 19), which is subject to positive nitrogen metabolite repression (186). Affected by nit-2 and MS5 regulator genes (838, 1076a) (see nmr-1). Used to study repression of nitrate reductase (26) and nonenzymatic reduction of nitrite (185). Induced by nitrite (198).

nit-7: nitrate nonutilizer-7
IIIR. Between trp-1 (26 to 32%) and dow (45%) (D.D. Perkins, unpublished data).

Cannot use nitrate or hypoxanthine as a nitrogen source. Resembles nit-1, nit-8, and nit-9 in affecting the molybdenum-containing cofactor common to nitrate reductase and xanthine dehydrogenase (1080, 1081) (Fig. 19 and 24).

nit-8: nitrate nonutilizer-8
IR. Linked to nit-1 (32%) (1080). Right of mt (10 to 15%) (D.D. Perkins, unpublished data).

Cannot use nitrate or hypoxanthine as a nitrogen source. Lacks the molybdenum cofactor for nitrate reductase and xanthine dehydrogenase (1080, 1081) (Fig. 19 and 24).

nit-9: nitrate nonutilizer-9
IVR. Right of nit-4 (9%). Linked to nit-3 (35 to 38%) (1080).

Cannot use nitrate or hypoxanthine as a nitrogen source. Lacks the molybdenum cofactor for nitrate reductase and xanthine dehydrogenase (Fig. 19 and 24). A complex locus with three complementation groups, comparable to cnxABC of Aspergillus nidulans. (1080, 1081)

nmr-1: nitrogen metabolite regulation
VR. Between am (3 to 7%) and gln-1 (4 to 10%) (1079).

Synthesis of nitrate reductase is derepressed on ammonium, glutamate, or glutamine. Hypostatic to nit-2 and nit-4. Prototrophic. Isolated and scored by sensitivity to chlorate in the presence of glutamine. (295, 1079) MS5 is a possible allele. MS5 is unmapped and is not allelic with nit-2 or nit-3 on the basis of two wild-type ascospores from poorly fertile crosses in each case. MS5 is derepressed on glutamine. Levels of nitrate reductase, nitrite reductase, histidase, and acetamidase are elevated in the presence of glutamine and the respective enzyme inducer. Prototrophic. Scored the same as the mutant nmr-1 and checked by assaying for nonrepressibility of nitrate reductase by glutamine. (838; G.J. Sorger, personal communication)

NO: Nucleolus organizer
VL. Right of terminal sat (60, 817) and of terminal translocations ALS176, ALS182, and AR190. Left of lys-1 and of translocations AR30, AR33, AR45, NM130, AR177, and NM183; thus, left of caf-1 (60, 817; D.D. Perkins, N.B. Raju, and E.G. Barry, in preparation). T(OY321) divides the NO into two portions, each of which retains ability to form a nucleolus (D.D. Perkins, N.B. Raju, and E.G. Barry, in preparation). (821)

Genes specifying 5.8S, 17S, and 26S rRNA (but not 5S) are located in the nucleolus organizer region in a tandemly repeated DNA sequence (215, 361). Wild type 74-OR23-1A has 185 tandem repeats (571). Nucleotide sequence of the 5.8S ribosomal DNA has been determined; comparison with yeast cells shows 145 of 158 rRNA residues conserved (974). Hybridization shows that sequences are shared both with Xenopus and Drosophila (216). T(AR33) produces duplications with two copies of the nucleolus organizer (817), which undergo demagnification (887) in such a way that different nontranscribed spacer sequences from both parental nucleolus organizers are retained (888). Genes specifying 5S rRNA are not included in the ribosomal DNA repeat unit, but are located elsewhere in the genome as dispersed single genes surrounded by heterogeneous flanking sequences (361, 975). For rRNA processing, see rip-1.

nt: nicotinic acid or tryptophan
VIIR. Between arg-10 (2 to 12%) and sk (7 to 18%) (789). (874)

Uses nicotinic acid. May respond also to tryptophan, phenylalanine, tyrosine, quinic acid, and precursors of nicotinic acid or tryptophan, or both, depending on genetic background (448, 760). Best supplemented with nicotinamide and scored as a nic mutant. Probably deficient in tryptophan pyrrolase (tryptophan 2,3-dioxygenase) (Fig. 18), but direct evidence is lacking because tryptophan oxygenase cannot be assayed in Neurospora (368). Kynurenine formamidase levels are normal (368). Pyridine nucleotide levels (111).

nuc-1: nuclease-1
IR. Right of T(AR173) and his-2 (<1%). Left of lys-4 (1%). (514)

nuc-1 mutants (other than nuc-1c) are unable to use RNA or DNA as a phosphorus source (450, 514). Defective in production of repressible alkaline and acid phosphatases (671, 1077). Several nucleases are absent or reduced (449). nuc-1 is epistatic to both pconc and pregc (671) and to pgovc (665). Scored on low-phosphate medium by a staining reaction with alpha-naphthyl phosphate plus diazo blue B (397, 1077), by failure to grow on minimal medium altered so that 0.1 g of RNA or DNA per liter is substituted for the inorganic phosphate source (514, 538), or by failure to grow on low-phosphate medium at a pH above 7 (R.L. Metzenberg, personal communication). nuc-1c is constitutive for alkaline phosphatase synthesis and maps very close to nuc-1. nuc-1c acts only if it is cis to normal nuc-1. In duplications, nuc-1c is dominant to nuc-1+, which is dominant to nuc-1. nuc-1c is epistatic to nuc-2 (670). nuc-1c is scored on high-phosphate medium by a staining reaction with alpha-naphthyl phosphate plus diazo blue B (397, 1077) or by suppression of the nuc-2 phenotype on low-phosphate medium at high pH (670). Used to study phosphate transport (624). For regulation model see references 665 and 670.

nuc-2: nuclease-2
IIR. Between the T(NM177) breakpoints; hence, right of aro-3. Left of preg (1 to 2%) and pe (4%). Probably allelic with pcon (0/854) (593, 671). (514)

Unable to use RNA or DNA as a phosphorus source (514). Defective in production of repressible alkaline and acid phosphatases (671, 1077). Several nucleases absent or reduced (449). Interaction with other phosphate regulatory genes (665). Recessive to nuc+ in partial diploids and heterokaryons (671). Not defective in nuh function (538). Scored on low-phosphate medium by a staining reaction with alpha-naphthyl phosphate plus diazo blue B (397, 1077), by failure to grow on minimal medium altered so that 0.1 g of RNA or DNA per liter is substituted for the inorganic phosphate source (514, 538), or by failure to grow on low-phosphate medium at a pH above 7 (R.L. Metzenberg, personal communication). Used to study phosphate transport (624). For a regulation model, see references 665 and 670. See pcon.

nuh: nuclease halo
Deficient in extracellular nuclease, giving reduced halos around colonies on DNA agar (538). The mutant nuh-4 is also sensitive to UV and nitrosoguanidine; the others are not. However, two mutants isolated by UV sensitivity, uvs-3 and uvs-6, also have the nuh phenotype (538).

nuh-1: nuclease halo
IIIR. Right of leu-1 (4%). Left of nuh-2 (<1%) and trp-1 (11%) (538).

nuh-2: nuclease halo-2
IIIR. Right of nuh-1 (<1%) and leu-1 (4%). Left of trp-1 (11%) (538).

nuh-3: nuclease halo-3
VR. Between cyh-2 (4%) and al-3 (17%) (538).

Releases only small amounts of deoxyribonuclease A (endonuclease) and deoxyribonuclease C (endo-, exonuclease) (359). Not sensitive to UV or chemical mutagens (E. Kafer, cited in reference 195).

nuh-4: nuclease halo-4
Probably allelic with uvs-3, q.v. (537, 538).

nuh-5: nuclease halo-5
IIR. Linked to trp-3 (30%), near T(4637) (538).

nuh-6: nuclease halo-6
IR. Between the centromere (5%) and nic-2 (4%) (538).

nuh-8: nuclease halo-8
IR. Right of nic-1. (See note added in proof in reference 538). Formerly called nuh(18).

nuh(23): nuclease halo
VR. Linked to nuh-3 (6%) (538).

Nystatin resistant
See erg: ergosterol.

oli: oligomycin resistant
VIIR. Between met-9 (8 to 24%) and arg-11 (3 to 16%) (960). Linked to frq-1 (<2%) and possibly allelic (282, 283). (959)

Resistant to oligomycin. Defective in energy transduction (313). Structural gene for dicyclohexylcarbodiimide-binding proteolipid (subunit 9) of F0 portion of mitochondrial adenosine triphosphate synthetase (958). The amino acid sequence (81 residues) (959) shows extensive homology with the corresponding proteolipid in yeast, in which, in contrast to Neurospora, it is the product of a mitochondrial gene (960, 1109). Specific single amino acid substitutions have been identified for three mutants (959). oli mutants are selected effectively by using double mutant azs; has (called ANT-1), which is deficient in both salicyl hydroxamic acid-sensitive and azide-sensitive alternate oxidase pathways. Scored on 5 µg of oligomycin per ml of liquid medium, 3 days, 30°C (312). Altered period of circadian rhythm cosegregates and reverts with oli (282, 283).

os: osmotic sensitive
Unable to grow on media with elevated osmotic pressure. Scorable on solid or liquid media plus 4% NaCl (1.4 M). Most alleles can also be scored by morphology, having sticky, close-cropped aerial hyphae that tend to rupture and bleed. Morphology is influenced by humidity. Intense pigment of aggregated hyphae has suggested the name "flame," which was originally applied to some os mutants. os strains are useful for obtaining protoplasts (e.g., reference 971) and are reported to be efficient as recipients for DNA-mediated transformation in media of high osmolarity (1162). In addition to the numerous loci designated os, cut is a typical osmotic mutation. Mutant sor(T9) is osmotic sensitive and sorbose resistant and has low glucoamylase activity, but does not show the typical os morphology.

os-1: osmotic-1
IR. Between nic-1 (10 to 29%) and arg-13 (1%) (789, 812, 816). (M.R. Emerson, cited in reference 789)

Sensitive to high osmotic pressure. Readily scored by morphology on nonmoist slants or by failure to grow on media with 4% NaCl. Most os-1 alleles result in cultures that form no or few conidia on agar slants. Alleles NM233t and NM204t are heat sensitive (25°C versus 34°C). In media of high osmolarity, os-1 strains form protoplasts (323, 438). os-1 (Bl35) is an essential genotypic component of the wall-less strain slime (321). Protoplasts of strains carrying heatsensitive allele NM233t are stable at 37 C, with a 7.5-h redoubling time, and show good regeneration. The biochemical defect differs from that affected by either polyoxin or sorbose (chitin or glucan syntheses) (970, 971). Cell wall pores are four times larger in an os-1 mutant than in the wild type; os-1 also has a higher exclusion threshold and a 30-fold-higher galactosamine/ glucosamine ratio (1083, 1084). Intralocus complementation (676). Allele Y256M209 called flm-1.

os-2: osmotic-2
IVR. Right of cot-1 (4%) (816; A.L. Schroeder, personal communication).

Sensitive to high osmotic pressure. Readily scored by morphology on nonmoist slants.

os-3: osmotic-3
Described as a IR mutation right of nic-2 (4%) (654). Because of stock loss and ambiguity, validity as a separate locus cannot be confirmed (655, 802).

os-4: osmotic-4
I. Right of T(39311) and arg-1 (1%). Left of T(AR173) and T(AR190); hence, of un-2 and his-2. Linked to sn (0/33). (Data for allele Y256M233.) (802, PB)

Sensitive to high osmotic pressure. Readily scored by morphology on nonmoist slants. Allele Y256M223, originally called flm-2, is preferred over NM201o, on which the locus designation was initially based. (802)

os-5: osmotic-5
IR. Right of cyh-1 (12%). Left of the Tp(T54M94) right breakpoint and of arg-6 (1%). Linked to al-2 (<1%). (802, 808)

Sensitive to high osmotic pressure. Scorable by morphology on nonmoist slants.

os-6: osmotic-6; os-7: osmotic-7
Symbols used in reference 676 for os-1-linked osmotic mutations obtained among inl+ transformants in experiments using wild-type Neurospora DNA. Osmotic and osmotic-like mutants have also been reported in other transformation experiments (1162). It seems wise not to define new loci on the basis of variants arising in transformation experiments or to use data from transformed strains or their derivatives in mapping. Accordingly, os-6 and os-7 have not been included in the list of established loci.

ota: ornithine transaminase
IIIR. Between ad-4 (15%) and tyr-1 (14%) (241). Linked to pro-4 (4%) (D.J. West, cited in Neurospora Newsl. 16:19-22, 1970).

Ornithine-delta-transaminase deficient (241) (Fig. 10). Conidiates somewhat less than does the wild type (S. Brody, personal communication). Selected by ability to use exogenous ornithine as a precursor for arginine in an arg-5 arg-12s double mutant. Catabolism of ornithine (to glutamic-gamma-semialdehyde) is blocked, resulting in ornithine concentrations high enough to compensate for the low activity of the ornithine carbamyl transferase in the arg-12s mutant. The ota single mutant is prototrophic but prevents the efficient use of ornithine or arginine as the sole nitrogen source (241). Used to study flux through the arginine biosynthetic pathway (401). Used to study the utilization of endogenous versus exogenous ornithine (234). Sideramine production is completely blocked in absence of ornithine in the ota;arg-5;aga triple mutant, which is used to study iron transport (1146, 1147).

oxD: D-amino acid oxidase
IVR. Between the T(S1229) breakpoints; hence, right of pdx-1 (0/55 asci). Left of met-1 (3%) (55, 768, 808).

Lacks D-amino acid oxidase. Unable to use D-methionine to satisfy the growth requirement of the mutant met-1. Increased sensitivity to toxic effects Of D-phenylalanine and D-tyrosine. Unable to use D-methionine as the sole sulfur source (768). Resistant to D-ethionine (477). Strains carrying allele oxD1 are cysteine auxotrophs, probably owing to a closely linked coincident lesion (768); see cys-15.

Oxidase, terminal
See aod, azs, has, and cni-1.

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