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Les protéines à domaines LIM chez le protoplaste de tournesol (Helianthus annuus L.) : expression des gènes et cytolocalisation

Abstract : LIM proteins have been described as developmental regulators of eucaryotic organisms. They are characterized by the presence of one or several double zinc finger motifs, called LIM domains, in their sequence, which function by mediating protein-protein interactions. LIM proteins have the ability to interact with multiple protein partners. The majority of LIM proteins have been characterized in animal cells where they have been localized in the nucleus and in the cytoplasm. Nuclear LIM proteins, owing to their capacity to mediate numerous interactions, play an important role in the regulation of transcription. These proteins are involved in the control of key developmental processes, like cell division and embryonic development. Cytoplasmic LIM proteins are generally associated to actin cytoskeleton, and could regulate cytoskeleton dynamic. Several LIM proteins have been described to date in plants, but the biological functions of these proteins remained to be determined. To study the function of LIM proteins in sunflower, sunflower hypocotyl protoplasts were used as experimental model, as theirdevelopment can be modulated by varying culture conditions.
Using primer sets specific for each of the previously described LIM genes from sunflower, we have studied their expression in sunflower protoplasts by RT-PCR. We detected a transcript only for the gene HaWLIM-1, but not for the other two genes HaPLIM-1 and HaPLIM-2. On immunowestern blots, polyclonal antibodies directed against HaWLIM-1 protein recognized two proteins of 52 and 78 kDa respectively, indicating that the protein is not present as the 21 kDa monomer but rather as stable higher molecular structures. Immunocytolocalization studies showed that HaWLIM-1 is located in the nucleus and in the cortical cytoplasm. In the nucleus, it concentrated mainly in the nucleolus and could therefore play a role in the transcription of rRNA genes or the assembly of ribosomes. In the cytoplasm, different approaches, including double labelling and drug application, showed a strong colocalization of HaWLIM-1 with microtubules, suggesting a role in cytoskeleton organization.
HaWLIM-1 gene expression decreases during protoplast culture. Immunoblot experiments showed that antibodies directed against HaWLIM-1 recognized new proteins during culture, indicating that HaWLIM-1 protein could interact with other high molecular structures during protoplast development. Moreover, HaWLIM-1 protein showed a strong colocalization with microtubules during all the steps of cell division.
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Contributor : Anne-Claire Bordel <>
Submitted on : Friday, April 28, 2006 - 4:50:36 PM
Last modification on : Monday, April 20, 2020 - 10:14:24 AM
Long-term archiving on: : Saturday, April 3, 2010 - 11:17:11 PM

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Anne-Claire Bordel. Les protéines à domaines LIM chez le protoplaste de tournesol (Helianthus annuus L.) : expression des gènes et cytolocalisation. Biochimie [q-bio.BM]. Institut National Polytechnique de Toulouse - INPT, 2000. Français. ⟨tel-00012190⟩

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