Document Detail

Constitutive, light-responsive and circadian clock-responsive factors compete for the different l box elements in plant light-regulated promoters.
MedLine Citation:
PMID:  8252065     Owner:  NLM     Status:  MEDLINE    
The l box is a conserved regulatory motif which is found upstream of plant genes (rbcS, cab and nia) whose transcription is regulated by light and the circadian clock. Gel retardation and UV cross-linking assays were used to resolve two different groups of I box binding factors (IBFs) in tomato nuclear extracts. Active components of the first group (IBF-1) recognize the l box of the light-responsive rbcS promoter; one factor within this group, IBF-1a, also recognizes the adjacent G box, which has been shown previously to bind a different class of plant transcription factors, the G box binding factors (GBFs). To the limit of experimental resolution, IBF-1a and GBF compete for the same nucleotides on the G box. Nevertheless, these two activities are biochemically and immunologically distinct. The relative abundance of IBF-1a shows a vast decrease in dark-adapted plants. Factors in the second group (IBF-2), recognize the l box of the nia promoter, which is regulated both by light and the circadian clock; one factor within this group, IBF-2a, also binds the l box of a second promoter showing similar regulation, the cab promoter. The IBF-2a binding sites on the cab and nia promoters show extensive homology to a circadian clock-responsive promoter element from wheat. The abundance of IBF-2a is diurnally regulated and shows a dramatic induction around the onset of the light period. Transfer of the plants in continuous darkness demonstrates that this induction is under the control of a circadian clock.(ABSTRACT TRUNCATED AT 250 WORDS)
U Borello; E Ceccarelli; G Giuliano
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Plant journal : for cell and molecular biology     Volume:  4     ISSN:  0960-7412     ISO Abbreviation:  Plant J.     Publication Date:  1993 Oct 
Date Detail:
Created Date:  1994-01-13     Completed Date:  1994-01-13     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  9207397     Medline TA:  Plant J     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  611-9     Citation Subset:  IM    
ENEA, CRE Casaccia, Roma, Italy.
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MeSH Terms
Base Sequence
Binding, Competitive
Circadian Rhythm*
DNA-Binding Proteins / metabolism*
Gene Expression Regulation
Molecular Sequence Data
Plant Proteins / metabolism*
Promoter Regions, Genetic* / radiation effects
Regulatory Sequences, Nucleic Acid
Vegetables / genetics*
Reg. No./Substance:
0/DNA-Binding Proteins; 0/Plant Proteins; 9007-49-2/DNA

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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