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  • 1
    ISSN: 1617-4623
    Keywords: EF-1α genes ; Transcription ; Cis-acting element ; Cell cycle ; Arabidopsis thaliana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract InArabidopsis thaliana, thetef1 box is acis-acting promoter element of the EF-1α A1 gene involved in the activation of transcription in meristematic tissues. The initiation of rootcalli in transgenicArabidopsis by 2,4-D shows that thetef1-dependent expression of theGUS reporter gene is not restricted to meristematic regions but involves all of the cycling cells. Hybridization experiments conducted usingArabidopsis cDNA clones organized in a dense array on filters, and cDNA probes prepared from cells in various states of growth, or blocked at different steps of the cell cycle, indicate that the enhanced expression of EF-1α genes occurs in cycling cells at the point of entry into the cell cycle and remains constant during transit through the cycle. The analysis of several promoters of genes, other than EF-1α, which are overexpressed in growing cells and involved in the processes of translation or redox regulation, reveals the presence of sequences showing partial homologies with thetef1 box. TheArabidopsis ribosomal genesrp18 and the tobacco genethioh2, encoding a thioredoxin h, contain such sequences. Gel retardation experiments suggest that these sequences are targets for the same proteins as those that interact with thetef1 box of theArabidopsis EF-1αA1 gene. In transfectedArabidopsis protoplasts, the putativetef1 sequencethioh2 partially restores the activity of atef1 box-lessEF-1α Al promoter. These data demonstrate that thetef1 box is a ubiquitous cis-acting element involved in the transcriptional activation of plant genes that are overexpressed in cycling cells. The deduced consensus sequence of thetef1 box is arGGRYAnnnnnGTaa. The key role that this regulatory element may play in the cell cycle, by pleiotropic control of the expression of genes encoding components of the translational apparatus or involved in regulating the redox state of the cell is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5028
    Keywords: Arabidopsis ; genome ; kinase ; lectin ; receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An Arabidopsis cDNA clone that defines a new class of plant serine/threonine receptor kinases was found to be a member of a family of four clustered genes (lecRK-a1–a4) which have been cloned, sequenced and mapped on chromosome 3. This family belongs to a large superfamily encoding putative receptors with an extracellular domain homologous to legume lectins and appears to be conserved at least among dicots. In the Columbia ecotype only the lecRK-a1 and perhaps the lecRK-a3 gene is functional, since lecRK-a2 is disrupted by a Ty-copia retroelement and lecRK-a4 contains a frameshift mutation. Structural analysis of the lecRK-a1 and lecRK-a3 deduced amino-acid sequences suggests that the lectin domain is unlikely to be involved in binding monosaccharides but could interact with complex glycans and/or with hydrophobic ligands. Immunodetection of lecRK gene products in plasma membranes purified by free-flow electrophoresis showed that the lecRK-a proteins are probably highly glycosylated integral plasma membrane components.
    Type of Medium: Electronic Resource
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