MODIFIERS OF THE cot GENE IN NEUROSPORA: THE GULLIVER MUTANTS

Abstract

ORPHOLOGICAL mutants were originally studied in Neurospora on account of their value as genetic markers. Recently, their potential usefulness for the analysis of differentiation has received some attention (for example MUR-RAY and SRB 1962; SUSSMAN, LOWRY, and DURKEE 1964; BACHMANN 1964;BRODY and TATUM 1966). ThiAs is a promising development because a well characterized group of morphological mutants may become instrumental in the elucidation of the circuits involved in the programming of morphogenesis, just as the study of regulatory mutants led to the elucidation of the circuits involved in the control of metabolism (JACOB and MONOD 1961 ) .This paper deals with a group of morphological mutants which might be useful for the approach outlined above. These mutants act as modifiers of the temperature sensitive colonial gene cot, giving rise to giant ("gulliver") colonies. MATERIALS A N D METHODS Strains:Standard markers were obtained from the Fungal Genetics Stock Center, and combined with the cot gene by crossing. cot (isolation No. C102t) determines colonial growth at temperatures above 32"C, but unrestricted, wild-type growth at lower temperatures (MITCHELL and MITCHELL 1954). Its wild-type allele, on the other hand, allows unrestricted growth regardless of the temperature. Gulliver (gul) mutants were usually isolated by ultraviolet (UV) irradiation of microconidia1 ( p e p ) cot strains. The UV doses applied allowed survival of 0.2 to 13% of the population. Media ~l z d incubation temperatures:Fries minimal medium (BEADLE and TATUM 1945) was used for plating at 32 to 34°C. Occasionally, a mixture of 0.1% sorbose, 0.05% glucose and 0.05% fructose was substituted for sucrose in order to obtain colonial growth of cot+ strains. The medium of WESTERGAARD and MITCHELL (1947), with 1% sucrose, was used for crosses at 20 to 25°C. The medium of VOCEL (1956) was used for stock cultures at 20°C. Media were supplemented as required.Heterocaryons: The input strains, carrying different auxotrophic markers, were inoculated jointly on minimal medium plates. Single inoculations served as controls.Crosses: In all guZ+ x gul crosses, gul+ was the protoperithecial parent. Ascopores were collected and treated for 5 min with a solution of sodium hypochlorite. The ascospores were washed in water by centrifugation and resuspended in semisolid agar (0.2%) for counting, activating by heat-shock, diluting and plating. Germination was scored using a dissection micro-' .\'did 11)grank from the Consejo Nilclonal de Investigaciones Cientificas y Tkcnicas (Repdblica Argentina

Chromosomal loci of Neurospora crassa

“…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.…”

“…Modifier of the colony size of the mutant cot-i at restrictive temperatures (875,1068). cot-i; gul-i strains take 60 h to reach the stationary phase (32 to 34°C) compared with 12 h for cot-i gul-l + strains (1068).…”

“…Able to make heterokaryons. Of 36 independent gul mutations, 25 were gul-i alleles (1068). Recombination within gul-i is unaffected by rec-3, which acts on the nearby am-i locus (998).…”

“…Occasional gulprogeny arise from gul+lgulpseudowild disomic ascospores. Unable to make heterokaryons (1068). gui4: gulliver4 VII.…”

The GUL-1 Protein Binds Multiple RNAs Involved in Cell Wall Remodeling and Affects the MAK-1 Pathway in Neurospora crassa

“…Impaired function of COT-1 results in significant morphological defects (Yarden et al, 1992 ; Gorovits et al, 1999 ; Maerz et al, 2008 ; Herold and Yarden, 2017 ). Inactivation of gul-1 partially suppresses the severity of growth phenotypes associated with cot-1 (ts) and its coactivator mob-2a (Terenzi and Reissig, 1967 ; Herold and Yarden, 2017 ; Aharoni-Kats et al, 2018 ). Deletion of gul-1 modifies the expression of cell wall remodeling genes (Herold and Yarden, 2017 ), nitrogen and amino-acid metabolism genes and almost 300 genes of unknown function (Herold et al, 2019 ).…”