Induction of cell wall-degrading enzymes, secretion of toxins, enforcement of fungal cell wall architecture, and detoxification of host defense molecules are important or essential for the fungal infection of plants. Genes important for each of these functions have been identified in various fungal species. Understanding how these genes are coordinately regulated and how many regulators are involved in the process is a challenge. We recently discovered a transcription factor gene, AbVf19, which positively regulates hydrolytic enzyme-coding genes. Here, we report on another transcription factor gene, Amr1, which negatively regulates a subset of these genes during late-stage pathogenesis and positively regulates melanin biosynthesis during conidiogenesis. This study adds another dimension to the complex regulation and overall importance of hydrolytic enzyme genes during plant pathogenesis by necrotrophic fungi. In addition, this study provides an example on the evolutionary implication of virulence in the necrotrophic fungus, A. brassicicola. One transcription factor essential for long-term survival because of its role in melanin biosynthesis is used instead to suppress virulence. We speculate that the suppressive functions of Amr1 contribute to the specialized adaptation of A. brassicicola as an efficient and successful facultative parasite.