Identification of pathogenicity genes regulated by two kinds of transcription regulators of the fungal plant pathogen Fusarium oxysporum

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We previously identified two genes, FOW2 and FOW3, which encode Zn(II)2Cys6-type and His2Cys2-type transcription regulators, respectively, essential for plant infection in the melon wilt pathogen Fusarium oxysporum f. sp. melonis. In this research, we attempted to isolate Fow2-or Fow3-regulated genes.We constructed cDNA subtraction libraries, which contained genes with changes in transcription levels caused by mutations in FOW2 and FOW3. Screening of these libraries by cDNA dot-blot differential hybridization and RNA gel blot analyses identified six genes positively regulated by Fow2. We made mutants of these genes and identified a Ren1-regulated pathogenicity gene, named VRF2-1. The vrf2-1 mutant showed reduced virulence on melon plants, although the fow2 mutant completely lost pathogenicity. This result indicates that Fow2 regulates the transcription of multiple pathogenicity genes, including VRF2-1. We sequenced a BAC clone encoding FOW2 and found that VRF2-1 is also encoded by this … More clone. This clone contains additional 29 genes, of which 10 were found to be possibly regulated by Ren1, suggesting that the Fow2-regulated genes are closely linked with FOW2. Database homology search and PCR analysis revealed that the filamentous ascomycetes species have the FOW2 homologues. This suggests that the FOW2 homologues also control plant infection in other fungi.We also identified two genes, REN1 and FoSTUA, which encode different types of transcription regulators essential for conidiation in F. oxysporum. In plant pathogenic fungi, conidia play important roles in the disease cycle as disseminated propagules and primary and secondary inocula. We performed expressed sequence tag analysis during vegetative growth and conidiation and identified 496 genes specifically detected in the conidiation cDNA library. Comparison of the transcription levels of the 496 genes between the wild-type strain and the ren1 mutant or the fostuA mutant identified 35 and three genes regulated by Ren1 and FoStuA, respectively. Less