title: FAR-RED INSENSITIVE219 modulates CONSTITUTIVE PHOTOMORPHOGENIC1 activity via physical interaction to regulate hypocotyl elongation in Arabidopsis.
abstract: FAR-RED INSENSITIVE219 (FIN219) in Arabidopsis (Arabidopsis thaliana) is involved in phytochrome A-mediated far-red (FR) light signaling. Previous genetic studies revealed that FIN219 acts as an extragenic suppressor of CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1). However, the molecular mechanism underlying the suppression of COP1 remains unknown. Here, we used a transgenic approach to study the regulation of COP1 by FIN219. Transgenic seedlings containing ectopic expression of the FIN219 amino (N)-terminal domain in wild-type Columbia (named NCox for the expression of the N-terminal coiled-coil domain and NTox for the N-terminal 300-amino acid region) exhibited a dominant-negative long-hypocotyl phenotype under FR light, reflected as reduced photomorphogenic responses and altered levels of COP1 and ELONGATED HYPOCOTYL5 (HY5). Yeast two-hybrid, pull-down, and bimolecular fluorescence complementation assays revealed that FIN219 could interact with the WD-40 domain of COP1 and with its N-terminal coiled-coil domain through its carboxyl-terminal domain. Further in vivo coimmunoprecipitation study confirms that FIN219 interacts with COP1 under continuous FR light. Studies of the double mutant fin219-2/cop1-6 indicated that HY5 stability requires FIN219 under darkness and FR light. Moreover, FIN219 levels positively regulated by phytochrome A can modulate the subcellular location of COP1 and are differentially regulated by various fluence rates of FR light. We conclude that the dominant-negative long-hypocotyl phenotype conferred by NCox and NTox in a wild-type background was caused by the misregulation of COP1 binding with the carboxyl terminus of FIN219. Our data provide a critical mechanism controlling the key repressor COP1 in response to FR light.
authors.affiliation: Institute of Plant Biology, College of Life Science, National Taiwan University, Taipei 106, Taiwan.
authors.forename: Jhy-Gong
authors.initials: JG
authors.lastname: Wang
authors.forename: Chih-Hao
authors.initials: CH
authors.lastname: Chen
authors.forename: Ching-Te
authors.initials: CT
authors.lastname: Chien
authors.forename: Hsu-Liang
authors.initials: HL
authors.lastname: Hsieh
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D005799:Genes, Dominant / Q000235:genetics; D018546:Hypocotyl / Q000254:growth & development* / Q000378:metabolism / Q000528:radiation effects; D008027:Light; D055537:Light Signal Transduction / Q000528:radiation effects; D009024:Morphogenesis / Q000528:radiation effects; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000378:metabolism; D010641:Phenotype; D030821:Plants, Genetically Modified; D011485:Protein Binding / Q000528:radiation effects; D055503:Protein Multimerization / Q000528:radiation effects; D055550:Protein Stability / Q000528:radiation effects; D017434:Protein Structure, Tertiary; D036226:Seedlings / Q000235:genetics / Q000528:radiation effects; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D010453:Peptide Synthases
chemical_list: D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D009687:Nuclear Proteins; D044767:Ubiquitin-Protein Ligases; C412831:AT2G46370 protein, Arabidopsis; D010453:Peptide Synthases; C109254:HY5 protein, Arabidopsis; C471983:AT2G32950 protein, Arabidopsis