Rhodosporidium Banno: Dosiseffektbeziehungen, Mutageneffektivität und Mutantenspektrum bei der Induktion Auxotrophie verursachender Mutationen durch ultraviolettes Licht und N-Methyl-N′-nitro-N-nitrosoguanidin

Abstract

The kinetics, efficiency, and specificity of induction of forward mutations to auxotrophy by ultraviolet light (UV) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was examined in stationary phase cells of Rhodosporidium (Rhodotorula) wild strain Rg1. In comparison to the spontaneous level the frequency of auxotrophic mutants was increased more than 1000 times by both mutagens, however, the mutagenic efficiency of MNNG was higher than that of UV. We found that the forward mutation rate is a linear function of the applicated UV and MNNG doses in the range to 600 J m-2 or 25 mM X min, respectively. The 35 studied biosynthetic pathways to amino acids, purines, pyrimidines, and vitamins are genetically blocked at different frequencies, but there is not any significant difference between UV and MNNG induced frequencies of mutants with a specific requirement. However, in difference to the approximately equal distribution of the MNNG-induced nic mutants among the genetic blocks of the tryptophan-nicotinamide pathway, UV-induced nic mutants occurred with a higher frequency in the genes of the tryptophan pyrrolase and the 3-hydroxykynureninase than in the genes of the other enzymes of the pathway.

Candida maltosa

“…In the Laboratory of Yeast Genetics at Greifswald University numerous auxotrophic, amino acid catabolic and alkane nonutilizing (alk) mutants were obtained from the C. maltosa strain!? L4 or EH15 on exposure to UV or MNNG using the same conditions as described by Bottcher and Samsonova (1978) for Rhodosporidium Banno. The total mutant frequencies were 0.05 and 0.4% with UV or MNNG, respectively Klinner et al 1984;Samsonova et al 1987;Schwarz et al 1987).…”

Occurrence of the general control of amino acid biosynthesis in yeasts

“…The results presented in this paper indicate that we found further species, whose amino acid biosynthesis is regulated by the general control, but also yeast species without this regulatory mechanism. (lys) and T. adeninovorans W77 (/u ura) were obtained on exposure to N-methyl-N'-nitro-N-nitrosoguanidine as previously decribed (BOTTCHER and SAMSONOVA 1978).…”

Enrichment of mutants of Rhodosporidium toruloides by the use of inositol starvation

“…JAeucine auxotrophs are common after mutagenesis in R. tordoides (BOTTCHER and SAMSONOVA 1978) and they are particularly common after inositol starvation in Neurospora crassa (LESTER and GROSS 1959). Tryptophan auxotrophs, in contrast, have never previously been isolated in R. toruloides (BOTTCHER and SAMSONOVA 1978). The lethal effects of inositol starvation have been rcported in the imperfect yeast Kloeckera apiculata (BIDGWAY and DOUGLAS 1958), the ascoillycete yeast 8. cerevisiae ) the aseoniycete fungus N .…”