title: Expression and functional analyses of the plastid lipid-associated protein CHRC suggest its role in chromoplastogenesis and stress.
abstract: Chromoplastogenesis during flower development and fruit ripening involves the dramatic overaccumulation of carotenoids sequestered into structures containing lipids and proteins called plastid lipid-associated proteins (PAPs). CHRC, a cucumber (Cucumis sativus) PAP, has been suggested to be transcriptionally activated in carotenoid-accumulating flowers by gibberellin (GA). Mybys, a MYB-like trans-activator identified here, may represent a chromoplastogenesis-related factor: Its expression is flower specific and parallels that of ChrC during flower development; moreover, as revealed by stable ectopic and transient-expression assays, it specifically trans-activates ChrC promoter in flowers accumulating carotenoids and flavonoids. A detailed dissection of ChrC promoter revealed a GA-responsive element, gacCTCcaa, the mutation of which abolished ChrC activation by GA. This cis-element is different from the GARE motif and is involved in ChrC activation probably via negative regulation, similar to other GA-responsive systems. The GA responsiveness and MYBYS floral activation of the ChrC promoter do not overlap with respect to cis-elements. To study the functionality of CHRC, which is activated in vegetative tissues similar to other PAPs by various biotic and abiotic stresses, we employed a tomato (Lycopersicon esculentum) plant system and generated RNAi-transgenic lines with suppressed LeCHRC. Transgenic flowers accumulated approximately 30% less carotenoids per unit protein than controls, indicating an interrelationship between PAPs and flower-specific carotenoid accumulation in chromoplasts. Moreover, the transgenic LeCHRC-suppressed plants were significantly more susceptible to Botrytis cinerea infection, suggesting CHRC's involvement in plant protection under stress conditions and supporting the general, evolutionarily preserved role of PAPs.
authors.affiliation: Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Hebrew University of Jerusalem, Rehovot 76100, Israel.
authors.forename: Yael
authors.initials: Y
authors.lastname: Leitner-Dagan
authors.forename: Marianna
authors.initials: M
authors.lastname: Ovadis
authors.forename: Elena
authors.initials: E
authors.lastname: Shklarman
authors.forename: Yigal
authors.initials: Y
authors.lastname: Elad
authors.forename: Dalia
authors.initials: D
authors.lastname: Rav David
authors.forename: Alexander
authors.initials: A
authors.lastname: Vainstein
mesh_terms: D000222:Adaptation, Physiological; D000595:Amino Acid Sequence; D001483:Base Sequence; D020171:Botrytis / Q000502:physiology; D002338:Carotenoids / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018553:Cucumis sativus / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D035264:Flowers / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D005875:Gibberellins / Q000502:physiology; D018551:Solanum lycopersicum / Q000382:microbiology / Q000502:physiology; D008969:Molecular Sequence Data; D010935:Plant Diseases; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D030821:Plants, Genetically Modified / Q000382:microbiology / Q000502:physiology; D018087:Plastids / Q000502:physiology*; D011401:Promoter Regions, Genetic; D034622:RNA Interference
chemical_list: C104174:CHRC protein, Cucumis sativus; D002352:Carrier Proteins; D005875:Gibberellins; D010940:Plant Proteins; D002338:Carotenoids