ylo : yellow
This name is used for mutants with yellow carotenoids. Ease of recognition of carotenoid differences depends on the light source. Hue appears to differ under various fluorescent lamps or in daylight. The difference from wild type is less marked in young cultures. In addition to mutations at loci designated ylo, some alleles of al-1 produce lemon yellow carotenoids (especially ALS4 and RES-25), although in reduced quantity (2018, 2020, 2084). Some morphological mutants may appear yellowish or pale rather than wild-type orange. Saturation is modified by vvd and by genes such as eas and os.
ylo-1 : yellow-1
VIL. Between cys-1 (8%), T(IBj5)L and un-13 (2%; 38 kb), cpc-1 (1%; 3%; 143 kb), Bml (1815, 2182).
Cloned and sequenced: Orbach-Sachs clone G17E11 (1815, 2182).
Encodes a putative aldehyde dehydrogenase (1815). Mutants are defective in the genesis of carotenoids. Both conidia and mycelia become yellow. The exact nature of the defect is not known; no one specific stage of carotenoid biosynthesis appears to be blocked. Small amounts of several carotenoids, including β-carotene, are accumulated, but neurosporaxanthin, the major carotenoid pigment in wild type, is not (748, 1785). A role has been suggested for ylo-1 in the conversion of either lycopene to 3,4-dehydrolycopene or torulene or γ-carotene to neurosporaxanthin (748) (Fig. 7). The structural similarity between neurosporaxanthin and retinoic acid suggests that late steps of carotenoid synthesis in Neurospora may resemble those in retinoic acid metabolism (1815). The appearance of mutant strains is nearly wild type in young cultures, but a color difference becomes clear with age. The apparent color and the ease of scoring depend on the illumination source, being quite different under fluorescent and incandescent lamps than in daylight. Undefined modifiers affect intensity.
ylo-2 : yellow-2
IL. Between suc, In(H4250)L and arg-1 (1%) (1592).
Conidia are yellow and rather sparse (1592). The yellow color may be a secondary effect of abnormal development. First shown to be distinct from ylo-1 in ref. (1031). Inferior to ylo-1 as a marker.
ylo-3 : yellow-3
A slow-conidiating allele of fl (1594).
ylo-4 : yellow-4
A pigmenting al-1 allele, called age-3 as well as ylo-4 (1394).
ypt-1 : ypt-like-1
IIR. Linked to eas (0T/17 asci) (867).
Cloned and sequenced: Swissprot YPT1_NEUCR, EMBL/GenBank S51252, PIR S30096; EST NP2C4.
Belongs to the ypt subfamily of ras-like genes, encoding a small GTP-binding protein thought to be involved in intracellular transport or secretion. Obtained by screening cDNA libraries with Zmypt genes from maize. Mutant phenotype not known (867).
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