Heterologous expression of the Aspergillus nidulans regulatory gene nirA in Fusarium oxysporum.
We have isolated strains of Fusarium oxysporum carrying mutations conferring a phenotype characteristic of a loss of function in the regulatory gene of nitrate assimilation (nirA in Aspergillus nidulans, nit-4 in Neurospora crassa). One of these nir- mutants was successfully transformed with a plasmid containing the nirA gene of A. nidulans. The nitrate reductase of the transformants is still inducible, although the maximum activity is lower than in the wild type. Single and multiple integration events were found, as well as a strict correlation between the presence of the nirA gene and the Nir+ phenotype of the F. oxysporum transformants. We also investigated how the A. nidulans structural gene (niaD) is regulated in F. oxysporum. Enzyme assays and Northern experiments show that the niaD gene is subject to nitrate induction and that it responds to nitrogen metabolite repression in a F. oxysporum genetic background. This indicates that both the mechanisms of specific induction, mediated by a gene product isofunctional to nirA, and nitrogen metabolite repression, presumably mediated by a gene product isofunctional to the homologous gene of A. nidulans, are operative in F. oxysporum.
Daboussi
M J
MJ
Institut de Génétique et Microbiologie, Unité Associée au CNRS 1354, Université Paris-Sud, Orsay, France.
Langin
T
T
Deschamps
F
F
Brygoo
Y
Y
Scazzocchio
C
C
Burger
G
G
D001233:Aspergillus nidulans / Q000235:genetics*; D015139:Blotting, Southern; D005670:Fusarium / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D005809:Genes, Regulator / Q000235:genetics*; D005816:Genetic Complementation Test; D005822:Genetic Vectors; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000235:genetics*; D009566:Nitrates / Q000378:metabolism; D014170:Transformation, Genetic
D009566:Nitrates; D009565:Nitrate Reductases; D050901:Nitrate Reductase