An aromatic prenyltransferase-like gene HlPT-1 preferentially expressed in lupulin glands of hop

Abstract

Prenylated aromatic compounds represent the chemical components in the glandular trichomes (lupulin glands) of hops (Humulus lupulus, Cannabinaceae), which give the characteristic flavor and taste of beer. To isolate cDNAs for prenyltransferase recognizing aromatic substrates in hops, we constructed a cDNA library from the lupulin glands and randomly sequenced 11,233 EST clones, to obtain 6,613 non-redundant EST sequence information. Among them, we found an aromatic prenyltransferase-like gene (HlPT-1), which possessed three features of the plant aromatic prenyltransferase family, i.e., a D-rich motif, membrane-spanning domains, and a transit peptide. The tissue-specific expression study of HlPT-1 in the intact plant revealed this gene to be highly expressed in hop corns (female flowers), especially in the lupulin glands. Subcellular localization analysis using GFP fusion proteins suggested that HlPT-1 was localized to plastids. Phylogenetic analysis predicted that the HlPT-1 gene evolved from homogentisate prenyltransferases involved with vitamin E and plastoquinone biosynthesis.