title: Molecular cloning of a carotenoid-associated protein from Cucumis sativus corollas: homologous genes involved in carotenoid sequestration in chromoplasts.
abstract: Chromoplasts are carotenoid-accumulating plastids found in the corollas and fruits of many higher plants. In most cases, the pigment in these plastids is accumulated with the aid of carotenoid-associated proteins located within unique structures. This paper reports the isolation and characterization of the cDNA (CHRC) from Cucumis sativus corollas which encodes the chromoplast-specific carotenoid-associated protein CHRC. The transit peptide cleavage site was determined and, using a chloroplast uptake system, it is shown that CHRC can be post-translationally targeted to these plastids where it is peripherally associated with thylakoids. Analysis of CHRC transcript level in Cucumis sativus revealed its temporal and tissue-specific regulation: the transcript was detected only in corollas, where its level increased in parallel to flower development, peaking just before anthesis. CHRC shares significant homology (59%) with the gene coding for fibrillin-a protein in Capsicum annuum red fruits whose function is essentially identical to that of CHRC. A CHRC fragment including the potential active site of the protein was used as a probe in Northern blot analyses of floral and fruit tissues from various plants containing chromoplasts of different types: CHRC homologs of similar sizes were revealed in all cases. The existence of a group of homologous genes coding for chromoplast-specific proteins which aid in the sequestration of carotenoids within specific structures is proposed.
authors.affiliation: Kennedy Leigh Center for Horticultural Research, Rehovot, Israel.
authors.forename: M
authors.initials: M
authors.lastname: Vishnevetsky
authors.forename: M
authors.initials: M
authors.lastname: Ovadis
authors.forename: H
authors.initials: H
authors.lastname: Itzhaki
authors.forename: M
authors.initials: M
authors.lastname: Levy
authors.forename: Y
authors.initials: Y
authors.lastname: Libal-Weksler
authors.forename: Z
authors.initials: Z
authors.lastname: Adam
authors.forename: A
authors.initials: A
authors.lastname: Vainstein
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport; D002338:Carotenoids / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000235:genetics; D003001:Cloning, Molecular; D018553:Cucumis sativus / Q000737:chemistry / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D017343:Genes, Plant; D008969:Molecular Sequence Data; D010940:Plant Proteins; D018520:Plant Shoots / Q000737:chemistry; D018087:Plastids / Q000378:metabolism*; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
chemical_list: C104174:CHRC protein, Cucumis sativus; D002352:Carrier Proteins; D018076:DNA, Complementary; D010940:Plant Proteins; D002338:Carotenoids