THE GENE CODING FOR THE DOPA DIOXYGENASE INVOLVED IN BETALAIN BIOSYNTHESIS IN AMANITA-MUSCARIA AND ITS REGULATION

Genomic and cDNA clones derived from the gene (dodA) coding for DOPA d ioxygenase, a key enzyme in the betalain pathway, were obtained from t he basidiomycete Amanita muscaria. A cDNA library was established in t he phage lambda ZapII and dodA clones were isolated using polyclonal a ntibodies raised against the purified enzyme. Their identity was confi rmed by comparison of the deduced amino acid sequence with the sequenc e of several tryptic peptide fragments of DOPA dioxygenase. The gene c oded for a 228-amino acid protein that showed no homology to published sequences. The coding region was interrupted by five short introns. R egulation was shown to occur at the transcriptional level; the mRNA ac cumulated to high levels only in the coloured cap tissue. dodA was fou nd to be a single-copy gene in A. muscaria. To our knowledge, this is the first gene from the betalain pathway to be cloned. It encodes a ty pe of aromatic ring-cleaving dioxygenase that has not been previously described.