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MycotoxinSecondary metabolism a b s t r a c t One of the secondary metabolite gene clusters of Aspergillus niger possesses highly homologous genes with those within the fumonisin gene cluster of Fusarium spp. At least 14 genes are considered to be present within approximately 50 kb genomic region. A number of strains of A. niger have been shown to produce fumonisin B2 (FB2), however, there has been no direct evidence that the gene cluster is responsible for FB2 production in this fungus. We investigated the involvement of the cluster in FB2 biosynthesis. The disruption of fum8, coding for an a-oxoamine synthase, resulted in loss of FB2 biosynthesis in A. niger, but did not influence the vegetative growth and sensitivity to high temperature or UV irradiation. The gene expression patterns of the transcription factor gene fum21 and fum8 were determined, but were different from those in F. verticillioides.

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The effect of trichothecene mycotoxins, deoxynivalenol (DON), fusarenon-X (FX) and nivalenol (NIV), on plaque formation of herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) in HEp-2 cells was examined. The 50% effective concentrations (EC50) of DON, FX, and NIV for HSV-1 plaque formation were 160, 56, and 120 ng/ml, respectively.Those for HSV-2 plaque formation were 94, 26, and 50 ng/ml, respectively. These three mycotoxins showed about 2-fold higher selectivity to HSV-2 than to HSV-1. Plaque formation of HSV-1 was not inhibited with trichothecenes at concentrations completely inhibiting plaque formation when cells were treated during virus adsorption period or 15 hr before infection. These results indicate that trichothecenes affect replication of HSV-1 after virus adsorption, but not before or during virus adsorption to the host cells.