Gibberella fujikuroi mutants obtained with UV radiation and N-methyl-N'-nitro-N-nitrosoguanidine

Abstract

N-methyl-N'-nitro-N-nitrosoguanidine (nitrosoguanidine) and to a lesser extent UV radiation are very mutagenic for Gibberella microconidia. The recommended nitrosoguanidine doses lead to much higher frequencies of mutants than are found in other microorganisms. The frequency of mutants among the survivors increases linearly with the nitrosoguanidine dose (molar concentration X time); the absolute number of viable mutants in a given population reaches a maximum for a dose of ca. 0.7 M X s. The microconidia are uninucleate. The onset of germination brings about increased lethality of nitrosoguanidine, but it does not modify the action of UV radiation. Mycelia are more resistant than spores to both agents. Visible illumination effectively prevents lethality when given immediately after UV radiation. Auxotrophs and color mutants are very easily obtained. Pink adenine auxotrophs and several classes of color mutants are affected in the biosynthesis of the carotenoid pigment, neurosporaxanthin.

Identification and biochemical characterization of a novel carotenoid oxygenase: elucidation of the cleavage step in the Fusarium carotenoid pathway

“…For northern experiments, the strains were grown in 250 ml of minimal medium (Avalos et al, 1985) in 500 ml Erlenmeyer flasks for 3 days at 30°C on an orbital shaker in the dark, and the mycelia were recovered by filtration through filter paper. The mycelial pads were either kept in the dark or illuminated for different times under a battery of fluorescent lamps (25 W m -2 ), and then frozen in liquid nitrogen.…”

Nitrogen availability and production of bikaverin and gibberellins in Gibberella fujikuroi

“…Strain IMI58289 is a gibberellin-producing wildtype of G. fujikuroi that belongs to mating group C, a separate genetic species, and was received from the Commonwealth Mycological Institute (Kew, UK). Mutants SG1 and SG140 were derived from IMI58289 after exposure of its spores to Nmethyl-N'-nitro-N-nitrosoguanidine [9]. Mycelia of the mutant SG1 hava a deep orange color, due to the accumulation of large amounts of carotenoids, mainly neurosporaxanthin [10].…”

“…Spores were collected from cultures grown on sporulation agar [9]. Erlenmeyer £asks (125 ml) that contained 25 ml of liquid minimal medium with 80 g l 3I D(+)-glucose were inoculated with spores [4] and incubated at 30³C in the dark in an orbital shaker (150 rpm).…”

Deviation of the neurosporaxanthin pathway towards β‐carotene biosynthesis in Fusarium fujikuroi by a point mutation in the phytoene desaturase gene

“…SF1 is a spontaneous nitrate reductase mutant obtained from FKMC1995 upon growth selection on media supplemented with KClO 3 [25]. SF4 is a carotenoid-overproducing mutant obtained from SF1 conidia exposed to N-methyl-N¢-nitro-N-nitrosoguanidine [63]. SF21 is a yellow-pigmented mutant obtained by the same procedure from SF4 (Table 1).…”