title: Identification and characterization of bZIP-type transcription factors involved in carrot (Daucus carota L.) somatic embryogenesis.
abstract: Seed dormancy is an important adaptive trait that enables seeds of many species to remain quiescent until conditions become favorable for germination. Abscisic acid (ABA) plays an important role in these developmental processes. Like dormancy and germination, the elongation of carrot somatic embryo radicles is retarded by sucrose concentrations at or above 6%, and normal growth resumes at sucrose concentrations below 3%. Using a yeast one-hybrid screening system, we isolated two bZIP-type transcription factors, CAREB1 and CAREB2, from a cDNA library prepared from carrot somatic embryos cultured in a high-sucrose medium. Both CAREB1 and CAREB2 were localized to the nucleus, and specifically bound to the ABA response element (ABRE) in the Dc3 promoter. Expression of CAREB2 was induced in seedlings by drought and exogenous ABA application; whereas expression of CAREB1 increased during late embryogenesis, and reduced dramatically when somatic embryos were treated with fluridone, an inhibitor of ABA synthesis. Overexpression of CAREB1 caused somatic embryos to develop slowly when cultured in low-sucrose medium, and retarded the elongation of the radicles. These results indicate that CAREB1 and CAREB2 have similar DNA-binding activities, but play different roles during carrot development. Our results indicate that CAREB1 functions as an important trans-acting factor in the ABA signal transduction pathway during carrot somatic embryogenesis.
authors.affiliation: National Centre for Plant Gene Research, Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Yucheng
authors.initials: Y
authors.lastname: Guan
authors.forename: Haibo
authors.initials: H
authors.lastname: Ren
authors.forename: He
authors.initials: H
authors.lastname: Xie
authors.forename: Zeyang
authors.initials: Z
authors.lastname: Ma
authors.forename: Fan
authors.initials: F
authors.lastname: Chen
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D000595:Amino Acid Sequence; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism*; D018552:Daucus carota / Q000196:embryology / Q000235:genetics* / Q000254:growth & development; D047108:Embryonic Development / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D008969:Molecular Sequence Data; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000196:embryology / Q000235:genetics / Q000254:growth & development; D011401:Promoter Regions, Genetic; D018749:RNA, Plant / Q000235:genetics; D016415:Sequence Alignment; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; D010940:Plant Proteins; D018749:RNA, Plant; D015534:Trans-Activators; D000040:Abscisic Acid