Identification of 6-Hydroxymellein Synthase and Accessory Genes in the Lichen Cladonia uncialis.

A transcribed polyketide synthase (PKS) gene has been identified in the lichen Cladonia uncialis. The complete nucleotide sequence of this PKS was determined from the amplified cDNA, and an assignment of individual domains was accomplished by homology searching using AntiSMASH. A scan of the complete genome sequence of C. uncialis revealed the accessory genes associated with this PKS gene. A homology search has identified that several genes in this cluster are similar to genes responsible for the biosynthesis of terrein in Aspergillus terreus. This permitted assignment of putative function to each of the genes in this new C. uncialis cluster. It is proposed that this gene cluster is responsible for the biosynthesis of a halogenated iscoumarin. This is the first report linking a gene cluster to a halogenated metabolite in lichen.