Molecular cloning and characterization of a novel gene encoding limonoid UDP-glucosyltransferase in Citrus

We isolated a cDNA clone encoding limonoid UDP-glucosyltransferase (limonoi d GTase) from the albedo of Satsuma mandarin (Citrus unshiu Marc.) and inve stigated the contribution to limonoid glucoside accumulation in fruit, The isolated cDNA clone (CitLGT) was 1732 bp in length encoding 511 deduced ami no acids with a predicted molecular mass of 57.5 kDa. The products of in vi tro translation from an expression vector had the limonoid GTase activity. Southern blot analysis of genomic DNA indicated that CitLGT was present as a single copy gene in the Citrus genome, The amount of transcript correspon ding to CitLGT mRNA changed the same way as the fluctuation of limonin gluc oside content during fruit development of navel orange (Citrus sinensis Osb .). This indicates that the transcription of CitLGT regulates the conversio n of limonoid aglycones to glucosides in citrus fruit. (C) 2000 Federation of European Biochemical Societies.