CLONING AND STRUCTURAL-ANALYSIS OF THE MELANIN BIOSYNTHESIS GENE SCD1ENCODING SCYTALONE DEHYDRATASE IN COLLETOTRICHUM-LAGENARIUM

Appressoria of the phytopathogenic fungus Colletotrichum lagenarium co ntain melanin, which has been implicated as an important factor in the penetration of host plants. A cDNA clone containing the melanin biosy nthetic gene encoding scytalone dehydratase (SCD1) from C. lagenarium was identified by hybridization with a heterologous cDNA probe from Ma gnaporthe grisea. The cDNA clone was used to identify a cosmid contain ing SCD1 in a genomic library of C. lagenarium, and the nucleotide seq uence was determined for both the cDNA and genomic clones. The SCD1 ge ne contained one open reading frame composed of 188 codons and two ded uced introns of 57 and 67 nucleotides. The deduced amino acid sequence of the N-terminal region of SCD1 showed high similarity to the amino acid sequence of scytalone dehydratase from Cochliobolus miyabeanus. A plasmid containing the SCD1 gene transformed the melanin-deficient mu tant 9201Y (Sed(-)) to the wild phenotype but did not complement the c onditional seytalone dehydratase-deficient mutant C. lagenarium 8015. Genomic DNA analysis indicated that the SCD1 gene is a single locus in C. lagenarium. Transcripts of the SCD1 gene were detected 2 h after t he start of conidial germination.