Scytalone dehydratase is involved in the production of fungal dihydroxynaphthalene melanin. We isolated and characterized SCD1, a gene encoding scytalone dehydratase, from the phytopathogenic fungus Bipolaris oryzae. Sequence analysis showed that SCD1 encodes a putative protein that has 185 amino acids, a molecular weight of 21 kDa and 51-75% sequence identity to other fungal scytalone dehydratases. Targeted disruption of SCD1 showed that this gene is necessary for melanin biosynthesis in B. oryzae. Northern blot analysis showed that SCD1 transcripts are specifically enhanced by near-ultraviolet (300-400 nm) radiation.