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Kessler, Félix

Nom
Kessler, Félix
Affiliation principale
Fonction
Professeur.e ordinaire
Email
felix.kessler@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/320
_
0000-0001-6409-5043

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  • Publication
    Accès libre
    In vivo interaction between atToc33 and atToc159 GTP-binding domains demonstrated in a plant split-ubiquitin system
    (2008)
    Rahim, Gwendoline
    ;
    Bischof, Sylvain
    ;
    Kessler, Félix 
    ;
    Agne, Birgit
    The GTPases atToc33 and atToc159 are pre-protein receptor components of the translocon complex at the outer chloroplast membrane in Arabidopsis. Despite their participation in the same complex in vivo;, evidence for their interaction is still lacking. Here, a split-ubiquitin system is engineered for use in plants, and the in vivo; interaction of the Toc GTPases in Arabidopsis and tobacco protoplasts is shown. Using the same method, the self-interaction of the peroxisomal membrane protein atPex11e is demonstrated. The finding suggests a more general suitability of the split-ubiquitin system as a plant in vivo; interaction assay.
  • Publication
    Accès libre
    Plastid Proteome Assembly without Toc159: Photosynthetic Protein Import and Accumulation of N-Acetylated Plastid Precursor Proteins
    Bischof, Sylvain
    ;
    Baerenfaller, Katja
    ;
    Wildhaber, Thomas
    ;
    Troesch, Raphael
    ;
    Vidi, Pierre-Alexandre
    ;
    Roschitzki, Bernd
    ;
    Hirsch-Hoffmann, Matthias
    ;
    Hennig, Lars
    ;
    Kessler, Félix 
    ;
    Gruissem, Wilhelm
    ;
    Baginsky, Sacha
    Import of nuclear-encoded precursor proteins from the cytosol is an essential step in chloroplast biogenesis that is mediated by protein translocon complexes at the inner and outer envelope membrane (TOC). Toc159 is thought to be the main receptor for photosynthetic proteins, but lacking a large-scale systems approach, this hypothesis has only been tested for a handful of photosynthetic and nonphotosynthetic proteins. To assess Toc159 precursor specificity, we quantitatively analyzed the accumulation of plastid proteins in two mutant lines deficient in this receptor. Parallel genome-wide transcript profiling allowed us to discern the consequences of impaired protein import from systemic transcriptional responses that contribute to the loss of photosynthetic capacity. On this basis, we defined putative Toc159-independent and Toc159- dependent precursor proteins. Many photosynthetic proteins accumulate in Toc159- deficient plastids, and, surprisingly, several distinct metabolic pathways are negatively affected by Toc159 depletion. Lack of Toc159 furthermore affects several proteins that accumulate as unprocessed N-acetylated precursor proteins outside of plastids. Together, our data show an unexpected client protein promiscuity of Toc159 that requires a far more differentiated view of Toc159 receptor function and regulation of plastid protein import, in which cytosolic Met removal followed by N-terminal acetylation of precursors emerges as an additional regulatory step.
  • Publication
    Accès libre
    The Acidic A-Domain of Arabidopsis Toc159 Occurs as a Hyperphosphorylated Protein
    Agne, Birgit
    ;
    Andrès, Charles
    ;
    Montandon, Cyril
    ;
    Christ, Bastien
    ;
    Ertan, Anouk
    ;
    Jung, Friederike
    ;
    Infanger, Sibylle
    ;
    Bischof, Sylvain
    ;
    Baginsky, Sacha
    ;
    Kessler, Félix 
    The translocon at the outer membrane of the chloroplast assists the import of a large class of preproteins with amino-terminal transit sequences. The preprotein receptors Toc159 and Toc33 in Arabidopsis (Arabidopsis thaliana) are specific for the accumulation of abundant photosynthetic proteins. The receptors are homologous GTPases known to be regulated by phosphorylation within their GTP-binding domains. In addition to the central GTP-binding domain, Toc159 has an acidic N-terminal domain (A-domain) and a C-terminal membrane-anchoring domain (M-domain). The A-domain of Toc159 is dispensable for its in vivo activity in Arabidopsis and prone to degradation in pea (Pisum sativum). Therefore, it has been suggested to have a regulatory function. Here, we show that in Arabidopsis, the A-domain is not simply degraded but that it accumulates as a soluble, phosphorylated protein separated from Toc159. However, the physiological relevance of this process is unclear. The data show that the A-domain of Toc159 as well as those of its homologs Toc132 and Toc120 are targets of a casein kinase 2-like activity.
  • Publication
    Accès libre
    The Chloroplast Import Receptor Toc90 Partially Restores the Accumulation of Toc159 Client Proteins in the Arabidopsis thaliana ppi2 Mutant
    Infanger, Sibylle
    ;
    Bischof, Sylvain
    ;
    Hiltbrunner, Andreas
    ;
    Agne, Birgit
    ;
    Baginsky, Sacha
    ;
    Kessler, Félix 
    Successful import of hundreds of nucleus-encoded proteins is essential for chloroplast biogenesis. The import of cytosolic precursor proteins relies on the Toc- (translocon at the outer chloroplast membrane) and Tic- (translocon at the inner chloroplast membrane) complexes. In Arabidopsis thaliana, precursor recognition is mainly mediated by outer membrane receptors belonging to two gene families: Toc34/33 and Toc159/132/120/90. The role in import and precursor selectivity of these receptors has been intensively studied, but the function of Toc90 still remains unclear. Here, we report the ability of Toc90 to support the import of Toc159 client proteins. We show that the overexpression of Toc90 partially complements the albino knockout of Toc159 and restores photoautotrophic growth. Several lines of evidence including proteome profiling demonstrate the import and accumulation of proteins essential for chloroplast biogenesis and functionality.