Abstract

Chrysosplenium americanum has a number of flavonoid O -methyltransferases (OMT's) that methylate substrates in a substrate and position specific fashion. These OMT's have been characterized biochemically, but only one such enzyme has been cloned to date, namely a 3 ' 5 ' flavonoid OMT. A genomic DNA clone containing OMT like sequences which was previously isolated was characterized in this work in order to investigate the possibility that these sequences might be derived from genes that had novel substrate and position specificity. These clones also gave insight into gene duplication and rearrangement in the gene family of flavonoid OMTs. Analysis indicated that the OMT-like sequences in the genomic clone are likely pseudogenes. They are likely the product of gene duplication, multiple segmental rearrangements and frame shift mutations. A PCR based strategy was used to isolate partial length cDNA clones that were nearly identical to the genomic sequences. This indicated that highly related genes are expressed, however there is no indication that the cDNA encode active enzymes. The screening of the C. americanum cDNA library using the partial cDNA clone isolated by PCR as a radioactive probe led to the recovery of 16 cDNA clones that were nearly identical to previously characterized 3 ' 5 ' flavonoid OMT. These cDNAs contained polymorphims for dinucleotide and trinucleotide repeats in their 5 ' UTR region.