Role of the Arabidopsis LIM proteins in the regulation of the actin cytoskeleton organisation and dynamics

Jessica Papuga

    Research output: Types of ThesisDoctoral Thesis


    Actin cytoskeleton organisation and dynamics are regulated by different types of actin-binding proteins. Recently, novel actin filament crosslinkers involved in the formation of parallel bundles have been characterized in both plants and animals: the two LIM domain-containing (LIM) proteins. In plants, these proteins can be divided into two sub-families whose members differ in their expression pattern. The WLIM sub-family members are widely expressed in vegetative tissues (WLIMs) whereas the PLIM subfamily members (PLIMs) are highly and almost exclusively expressed in pollen grains. An important question that remained to be answered is: why do plants have several proteins of this family and are the different members functionally distinct, or do they share one or several functions? To address these issues, we characterised and compared the actin regulatory activities of all six LIM proteins from Arabidopsis. Confocal analyses of transgenic Arabidopsis plants expressing individual GFP- fused LIM proteins and in vitro biochemical assays demonstrate that all the Arabidopsis LIM proteins are “true” actin-binding proteins able to directly interact with the actin cytoskeleton. In addition, all six Arabidopsis LIM proteins retain the ability to stabilize actin filaments and to trigger the formation of thick actin bundles in vitro as well as in transgenic LIM-expressing plants. Interestingly, in vitro investigations suggest that the members of WLIM and PLIM subfamilies are differentially regulated. Indeed, only PLIM respond to changes in pH and [Ca2+]. Whereas the modification of these parameters has no significant effects on WLIM activities, an increase of pH or [Ca2+] markedly inhibits PLIM activities. These data are strongly supported by live cell experiments in which we artificially modulated the cytoplasmic pH and [Ca2+] of cells derived from the transgenic LIM-overexpressing plants. The C-terminal domain of PLIMs has been identified as necessary for their regulation by pH and Ca2+.

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    Original languageEnglish
    • Steinmetz, André, Supervisor
    Award date28 Feb 2011
    Publication statusPublished - 28 Feb 2011


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