Isolation and Characterization of o-Diphenol-O-Methyltransferase cDNA Clone in Hot Pepper (Capsicum annuum L)
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Lee Byeong-Ha | Choi Dong-Su Department of Biology, Seoul National University, Seoul 151-742 (Korea Republic)
A cDNA clone, CaOMTI encoding an o-diphenol-O-methyltransferase (OMT), which is involved in capsaicin biosynthesis, was isolated by screening of a cDNA library prepared from the mRNA of pepper (Capsicum annuum L.) pericarp. Nucleotide sequence analysis of CaOMTI revealed that it had an open reading frame of 1080 bp which encodes a polypeptide with a predicted molecular weight of 39,430 D, corresponding well with the size of the known OMT's of tobacco, poplar, aspen, alfalfa, and cabbage. It also had five conserved boxes which appear in all known OMT's. The nucleotide sequence of CaOMTI had 89~74% identity with the OMT cDNA's of tobacco, aspen, alfalfa, and poplar, but a relatively lower identity of 59% with the OMT cDAN of maize. Amino acid sequence analysis also revealed that CaOMTI has high identity with the known OMT's which have a substrate of o-diphenolic compounds, especially 5-hydroxyferulic acid and caffeic acid. It supports CaOMTI which encodes an OMT. Southern blot analysis suggested that CaOMTI might exist in the form of multiple copies in the pepper genome. CaOMTI is expressed preferentially in pepper fruit and its expression levels increased during pepper fruit development, but decreased during fruit ripening, suggesting that the CaOMTI gene is fruit development-related. CaOMTI is the first reported cDNA clone for enzymes related to the phenlypropanoid pathway in pepper.
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