Characterization of two ABC transporters from biocontrol and phytopathogenic Fusarium oxysporum

Sequence comparisons of ABC transporter genes from two strains of Fusarium oxysporum (one biocontrol and one phytopathogenic (f. sp. lycopersici Race 1) isolates) to 16 sequences from other fungi among those deposited in GenBank indicated that these genes are well conserved. However, sequences of promoter and 5′ UTR regions of a previously characterized ABC transporter gene FoABC1 differed between 8 phytopathogenic and 11 biocontrol strains of F. oxysporum. A phylogenetic analysis of promoter sequences indicated that pathogenic strains were grouped in a single clade, clearly distinct from clades with biocontrol agents. Although sequencing of promoter regions was done on only 20 strains, results suggest that FoABC1 may be regulated differently between phytopathogenic and biocontrol strains of the fungus. In studies on the activity (RNA) of FoABC1 in the presence of the fungicide thiram, one pathogen was down regulated to undetectable levels by a brief exposure to thiram, the other pathogenic strain was not affected, while the one of the two biocontrol strains was up regulated and expression of FoABC1 in the other biocontrol strain was not changed. After a 1 h exposure to thiram, the level of expression of one pathogen remained down regulated to undetectable levels, while the other pathogen and both biocontrol agents were up regulated compared to the time zero control. Additional research is needed to further understand the significance of the genetic difference in promoter regions between phytopathogenic and biocontrol strains for FoABC1.