FGSC #7209

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Reporting Genes: cot-1 nit-3

Species: crassa

Allele: C102(t) 14789

Alternate Strain Number: 4073

Depositor: DDP

Linkage Group: IVR IVR

Mating Type: A

Species Number: 10

Deposit Sheet ↗

Genes

Locus	Cultural Requirements	Link Group	Type
cot-1	IVR. Between pan-1 (2%) and his-4 (1 to 6%) (692, 812, 816). Extremely colonial at 34°C, but completely normal growth, morphology, and fertility at 25°C and below. Linear growth is maximum at 24°C (374). Becomes colonial at 32°C; colonies from ascospores or conidia are viable and continue to grow slowly with dense branching, but do not conidiate. They quickly resume normal growth when shifted to a permissive temperature (692, 1068). Recessive in duplications (808); apparent dominance in heterokaryons (374) may have resulted from a shift in nuclear ratios. Used in studies of septation and branching (202), growth-inhibiting mucopolysaccharide (878, 879), and sulfate transport (641). Cell wall analysis (374). Growth is stimulated by lysine or arginine (0.1 mM) on glucose media at high temperatures (615). Because of high viability and tightly restricted growth at restrictive temperatures and normality at 25°C, cot-1 mutants have valuable technical applications. For example, crosses homozygous for cot-1 have been used in combination with sorbose for experiments with rec genes, where high-density ascospore platings are required for precise quantitative analysis of intralocus recombination (e.g., references 165, 997, and 1070). In another application, when shifted up after initial growth at the permissive low temperature, cot-1hyphae assume a "bottle brush" appearance with small side branches (692). This has been used to select uvs mutants by subsurface survival on UV-irradiated plates containing p-aminobenzoic acid (938; D.E.A. Catcheside, personal communication). cot-1 conidia or ascospores from cot-1 x cot-1crosses are used for replication in a protocol involving transfer by filter paper (615). For suppressors of cot-1, see gul.	IVR	B
nit-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).	IVR	B