A Nitrate Non-utilizing Mutant of Gibberella Zeae

Abstract

A nitrate non-utilizing mutant of Gibberella zeae (Fusarium graminearum) was isolated following UV mutagenesis and filtration enrichment. In preliminary reports, this mutant was designated gdh, but it has now been renamed nnu. This mutant has a complex pleiotropic phenotype which affects most aspects of nitrogen utilization. The wild-type parent could use nitrate, nitrite, ammonium, urea, polyamines, and most amino acids and purines as sole source of nitrogen, but the nnu mutant could use only putrescine, anthranilic acid, and the amino acids asparagine, aspartic acid, glutamic acid, glutamine, ornithine, proline and tyrosine. Most of these compounds could also serve as the sole source of both carbon and nitrogen. Addition of 1 mM-glutamine or 1 mM-proline to the medium resulted in a synergistic growth response if spermidine, arginine, citrulline, histidine, phenylalanine or tryptophan was present as the primary nitrogen source. Addition of 1 mwammonium to the medium repressed growth when putrescine, aspartic acid, asparagine, glutamic acid or tyrosine was the primary nitrogen source. The addition of ammonium did not repress growth when anthranilic acid, glutamine, ornithine or proline was the primary nitrogen source. The nnu mutant grew more rapidly than its wild-type parent in race tubes on some complex media. The complexity and diversity of the alterations in nitrogen catabolism caused by the nnu mutation suggest that this locus is important in the regulation of nitrogen catabolism by G. zeae.

Chlorate-resistant, Nitrate-utilizing (crn) Mutants of Fusarium moniliforme (Gibberella fujikuroi)

“…[sexual stage Gibberella fujikuroi (Sawada) Wr.] is a filamentous ascomycete which can produce carcinogenic mycotoxins (Gelderblom et al, 1988) and cause stalk rot of maize and sorghum and equine leukoencephalomalacia of horses and donkeys (Nelson et al, 1981 ;Marasas et al, 1984). The fungus is heterothallic and can be readily crossed in the laboratory.…”