Photoexcited CRY2 interacts with CIB1 to regulate transcription and floral initiation in Arabidopsis.
Cryptochromes (CRY) are photolyase-like blue-light receptors that mediate light responses in plants and animals. How plant cryptochromes act in response to blue light is not well understood. We report here the identification and characterization of the Arabidopsis CIB1 (cryptochrome-interacting basic-helix-loop-helix) protein. CIB1 interacts with CRY2 (cryptochrome 2) in a blue light-specific manner in yeast and Arabidopsis cells, and it acts together with additional CIB1-related proteins to promote CRY2-dependent floral initiation. CIB1 binds to G box (CACGTG) in vitro with a higher affinity than its interaction with other E-box elements (CANNTG). However, CIB1 stimulates FT messenger RNA expression, and it interacts with chromatin DNA of the FT gene that possesses various E-box elements except G box. We propose that the blue light-dependent interaction of cryptochrome(s) with CIB1 and CIB1-related proteins represents an early photoreceptor signaling mechanism in plants.
Liu
Hongtao
H
Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, CA 90095, USA.
Yu
Xuhong
X
Li
Kunwu
K
Klejnot
John
J
Yang
Hongyun
H
Lisiero
Dominique
D
Lin
Chentao
C
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D056931:Cryptochromes; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D035264:Flowers / Q000254:growth & development*; D018506:Gene Expression Regulation, Plant; D008027:Light; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques
D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D056931:Cryptochromes; D004268:DNA-Binding Proteins; D050505:Mutant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D014157:Transcription Factors; C533832:CIB1 protein, Arabidopsis; C092776:CONSTANS protein, Arabidopsis; C103618:CRY2 protein, Arabidopsis; C418905:FT protein, Arabidopsis