A mutation in Aspergillus nidulans which affects the regulation of nitrite reductase and is tightly linked to its structural gene
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The selection of nis-5, a mutation which is tightly linked to the structural genes for nitrate reductase (niaD) and nitrite reductase (niiA) but which only affects nitrite reductase activities, is described. nis-5 single mutants have only 40% of the wild type activity of nitrite reductase after induction by nitrate and, for this reason, grow poorly on nitrate and nitrite. Nitrate reductase activity is not affected, and nis-5 is shown to complement with a niaD- mutation but not with a niiA- mutation.
When grown without inducer, nis-5 strains have higher than the non-induced wild type activity of nitrite reductase. This low, constitutive activity is insensitive to repression by ammonium. These facts explain why the nis-5 mutation weakly suppresses many nirA- and areAr mutations for utilization of nitrite.
Three of the possible explanations of this unusual phenotype are considered. Studies of nitrite reductase in cell-free extracts provided no evidence for the already unlikely possibility that nis-5 is a structural gene mutation resulting in the observed phenotype because of alteration in the catalytic activity and/or stability of the nitrite reductase.
A more plausible explanation is that it defines a receptor site for either the nirA gene product and/or the areA gene product. However, no evidence for this has yet been obtained from a study of double mutants carrying nis-5 and areA or nirA mutations.
A third possibility is that nis-5 creates a new, but inefficient promoter or ‘initiator’, which is not subject to the normal control systems (and therefore causes constitutive, deprepressed synthesis) but whose physical presence reduces maximal enzyme synthesis. The presence of a translocation in nis-5 strains suggests a means by which niiA could come to be under the control of another promoter/initiator.
KeywordsNitrite Aspergillus Structural Gene Nitrate Reductase Reductase Activity
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- Arst, H.N., Jr., Cove, D.J.: Methylammonium resistance in Aspergillus nidulans. J. Bact. 98, 1284–1293 (1969)Google Scholar
- Arst, H.N., Jr., Cove, D.J.: Nitrogen metabolite repression in Aspergillus nidulans. Molec. gen. Genet. 126, 111–141 (1973)Google Scholar
- Arst, H.N., Jr., Page, M.M.: Mutants of Aspergillus nidulans altered in the transport of methylammonium and ammonium. Molec. gen. Genet. 121, 239–245 (1973)Google Scholar
- Beckwith, J.R., Signer, E.R., Epstein, W.: Transposition of the lac region of E. coli. Cold Spr. Harb. Symp. quant. Biol. 31, 393–401 (1966)Google Scholar
- Bruenn, J., Files, J.G., Weber, K.: Synthesis of two lac repressor polypeptides in a mutant of Escherichia coli that has a new promotor for the lac operon mapping within the i gene. J. molec. Biol. 110, 255–267 (1977)Google Scholar
- Casadaban, M.J.: Transposition and fusion of the lac genes to selected promotors in Escherichia coli using bacteriophage lambda and mu. J. molec. Biol. 104, 541–555 (1976)Google Scholar
- Clutterbuck, A.J.: Aspergillus nidulans. In: Handbook of genetics (King, R.C., ed.), Vol. I, Bacteria, bacteriophages and fungi, pp. 447–510. New York and London: Plenum Press 1974Google Scholar
- Cohen, B.L.: Ammonium repression of extracellular protease in Aspergillus nidulans. J. gen. Microbiol. 71, 293–299 (1972)Google Scholar
- Cove, D.J.: The induction and repression of nitrate reductase in the fungus Aspergillus nidulans. Biochim. biophys. Acta (Amst.) 113, 51–56 (1966)Google Scholar
- Cove, D.J.: Control of gine action in Aspergillus nidulans. Proc. roy. Soc. B 176, 267–275 (1970)Google Scholar
- Cove, D.J.: Chlorate toxicity in Aspergillus nidulans: Studies of mutants altered in nitrate assimilation. Molec. gen. Genet. 146, 147–159 (1976)Google Scholar
- Hastie, A.C.: Benlate-induced instability of Aspergillus diploids. Nature (Lond.) 226, 771 (1970)Google Scholar
- Hynes, M.J.: Pleiotropic mutants affecting the control of nitrogen metabolism in Aspergillus nidulans. Molec. gen. Genet. 125, 99–107 (1973)Google Scholar
- Hynes, M.J.: Repression of enzymes of nitrogen catabolism by methylammonium and caesium chloride in strains of Aspergillus nidulans insensitive to ammonium repression. Molec. gen. Gene. 132, 147–152 (1974)Google Scholar
- Hynes, M.J., Pateman, J.A.J.: The genetic analysis of regulation of amidase synthesis in Aspergillus nidulans. I. Mutants able to utilize acrylamide. Molec. gen. Genet. 108, 97–106 (1970)Google Scholar
- Kinghorn, J.R., Pateman, J.A.: Studies of partially repressed mutants at the tamA and areA loci in Aspergillus nidulans. Molec. gen. Genet. 140, 137–147 (1975)Google Scholar
- Layne, E.: Spectrophotometric and turbidimetric methods for measuring proteins. In: Methods in enzymology (Colowick, S.P. and Kaplan, N.O., eds.), Vol. III, pp. 447–454. New York: Academic Press 1957Google Scholar
- MacDonald, D.W., Coddington, A.: Properties of the assimilatory nitrate reductase from Aspergillus nidulans. Europ. J. Biochem. 46, 169–178 (1974)Google Scholar
- MacDonald, D.W., Cove, D.J.: Studies on temperature sensitive mutants affecting the assimilatory nitrate reductase of Aspergillus nidulans. Europ. J. Biochem. 47, 107–110 (1974)Google Scholar
- Mackintosh, M.E., Pritchard, R.A.: The production and replica plating of micro-colonies of Aspergillus nidulans. Genet. Res. 4, 320–322 (1963)Google Scholar
- Pateman, J.A., Cove, D.J.: Regulation of nitrate reduction in Aspergillus nidulans. Nature (Lond.) 215, 1234–1237 (1967)Google Scholar
- Pateman, J.A., Kinghorn, J.R.: Nitrogen metabolism. In: Filamentous fungi, Vol 2, pp. 159–237 (Smith, J.E. and Berry, D., eds.) London: Edward Arnold Press 1976Google Scholar
- Pateman, J.A., Rever, B.M., Cove, D.J.: Genetic and biochemical studies of nitrate reduction in Aspergillus nidulans. Biochem. J. 104, 103–111 (1967)Google Scholar
- Pontecorvo, G., Roper, J.A., Hemmons, L.M., Macdonald, K.D., Bufton, A.W.J.: The genetics of Aspergillus nidulans. Advanc. Genet. 5, 141–238 (1953)Google Scholar