title: Riboflavin accumulation and characterization of cDNAs encoding lumazine synthase and riboflavin synthase in bitter melon (Momordica charantia).
abstract: Riboflavin (vitamin B2) is the universal precursor of the coenzymes flavin mononucleotide and flavin adenine dinucleotide--cofactors that are essential for the activity of a wide variety of metabolic enzymes in animals, plants, and microbes. Using the RACE PCR approach, cDNAs encoding lumazine synthase (McLS) and riboflavin synthase (McRS), which catalyze the last two steps in the riboflavin biosynthetic pathway, were cloned from bitter melon (Momordica charantia), a popular vegetable crop in Asia. Amino acid sequence alignments indicated that McLS and McRS share high sequence identity with other orthologous genes and carry an N-terminal extension, which is reported to be a plastid-targeting sequence. Organ expression analysis using quantitative real-time RT PCR showed that McLS and McRS were constitutively expressed in M. charantia, with the strongest expression levels observed during the last stage of fruit ripening (stage 6). This correlated with the highest level of riboflavin content, which was detected during ripening stage 6 by HPLC analysis. McLS and McRS were highly expressed in the young leaves and flowers, whereas roots exhibited the highest accumulation of riboflavin. The cloning and characterization of McLS and McRS from M. charantia may aid the metabolic engineering of vitamin B2 in crops.
authors.affiliation: Department of Crop Science, College of Agriculture and Life Sciences, Chungnam National University, 99 Daehangno, Yuseong-gu, Daejeon 305-764, Korea.
authors.forename: Pham Anh
authors.initials: PA
authors.lastname: Tuan
authors.forename: Jae Kwang
authors.initials: JK
authors.lastname: Kim
authors.forename: Sanghyun
authors.initials: S
authors.lastname: Lee
authors.forename: Soo Cheon
authors.initials: SC
authors.lastname: Chae
authors.forename: Sang Un
authors.initials: SU
authors.lastname: Park
mesh_terms: D020413:3' Untranslated Regions; D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005638:Fruit / Q000378:metabolism / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D029777:Momordica charantia / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D009097:Multienzyme Complexes / Q000235:genetics* / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D012256:Riboflavin / Q000378:metabolism*; D012258:Riboflavin Synthase / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D020413:3' Untranslated Regions; D018076:DNA, Complementary; D009097:Multienzyme Complexes; D010940:Plant Proteins; C044822:6,7-dimethyl-8-ribityllumazine synthase; D012258:Riboflavin Synthase; D012256:Riboflavin