Vignette d'image

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

Résultat de la recherche

Filtres

965
4947
933
Réinitialiser les filtres

Paramètres

Voici les éléments 1 - 10 sur 96
  • Publication
    Métadonnées seulement
    Characterization of a Plastoglobule-Localized SOUL4 Heme-Binding Protein in Arabidopsis thaliana
    (2020-1-31)
    Kessler, Félix 
    Heme plays an active role in primary plant metabolic pathways as well as in stress signaling. In this study, we characterized the predicted heme-binding protein SOUL4. Proteomics evidence suggests that SOUL4 is a component of Arabidopsis plastoglobules (PGs, chloroplast lipid droplets). SOUL4 contains heme-binding motifs and the recombinant protein is shown here to bind heme in vitro. Fluorescence-tagged SOUL4 colocalized with the specific PG marker Fibrillin1A (FBN1A) in transiently transformed Nicotiana benthamiana leaves. In addition, SOUL4 cofractionated with another PG marker Fibrillin2 (FBN2) in sucrose gradient ultracentrifugation experiments. In vitro kinase experiments revealed that SOUL4 is phosphorylated by a yet unknown chloroplast protein kinase. Our data demonstrate that SOUL4 is a bona fide PG protein and may function in heme-buffering in the chloroplast.
  • Publication
    Accès libre
    How chloroplasts protect themselves from unfolded proteins
    (2019-10-15)
    Kessler, Félix 
    ;
    Longoni, Fiamma 
    A genetic screen has identified the first signaling component of the unfolded protein response in chloroplasts.
  • Publication
    Accès libre
    Plastoquinone homoeostasis by Arabidopsis proton gradient regulation 6 is essential for photosynthetic efficiency
    (2019-6-20)
    Pralon, Thibaut 
    ;
    Venkatasalam, Shanmugabalaji 
    ;
    Longoni, Fiamma 
    ;
    Ksas, Brigitte
    ;
    Collombat, Joy 
    ;
    Desmeules, Saskia
    ;
    Glauser, Gaëtan 
    ;
    Havaux, Michel
    ;
    Finazzi, Giovanni
    ;
    Kessler, Félix 
    Photosynthesis produces organic carbon via a light-driven electron flow from H2O to CO2 that passes through a pool of plastoquinone molecules. These molecules are either present in the photosynthetic thylakoid membranes, participating in photochemistry (photoactive pool), or stored (non-photoactive pool) in thylakoid-attached lipid droplets, the plastoglobules. The photoactive pool acts also as a signal of photosynthetic activity allowing the adaptation to changes in light condition. Here we show that, in Arabidopsis thaliana, proton gradient regulation 6 (PGR6), a predicted atypical kinase located at plastoglobules, is required for plastoquinone homoeostasis, i.e. to maintain the photoactive plastoquinone pool. In a pgr6 mutant, the photoactive pool is depleted and becomes limiting under high light, affecting short-term acclimation and photosynthetic efficiency. In the long term, pgr6 seedlings fail to adapt to high light and develop a conditional variegated leaf phenotype. Therefore, PGR6 activity, by regulating plastoquinone homoeostasis, is required to cope with high light.
  • Publication
    Accès libre
    The Novel Chloroplast Outer Membrane Kinase KOC1 Is a Required Component of the Plastid Protein Import Machinery
    (2017)
    Zufferey, Mónica
    ;
    Montandon, Cyrille
    ;
    Douet, Véronique 
    ;
    Demarsy, Emilie
    ;
    Agne, Birgit
    ;
    Baginsky, Sacha
    ;
    Kessler, Félix 
    The biogenesis and maintenance of cell organelles such as mitochondria and chloroplasts require the import of many proteins from the cytosol, a process that is controlled by phosphorylation. In the case of chloroplasts, the import of hundreds of different proteins depends on translocons at the outer and inner chloroplast membrane (TOC and TIC, respectively) complexes. The essential protein TOC159 functions thereby as an import receptor. It has an N-terminal acidic (A-) domain that extends into the cytosol, controls receptor specificity, and is highly phosphorylated in vivo. However, kinases that phosphorylate the TOC159 A-domain to enable protein import have remained elusive. Here, using co-purification with TOC159 from Arabidopsis, we discovered a novel component of the chloroplast import machinery, the regulatory kinase at the outer chloroplast membrane 1 (KOC1). We found that KOC1 is an integral membrane protein facing the cytosol and stably associates with TOC. Moreover, KOC1 phosphorylated the A-domain of TOC159 in vitro, and in mutant koc1 chloroplasts, preprotein import efficiency was diminished. koc1 Arabidopsis seedlings had reduced survival rates after transfer from the dark to the light in which protein import into plastids is required to rapidly complete chloroplast biogenesis. In summary, our data indicate that KOC1 is a functional component of the TOC machinery that phosphorylates import receptors, supports preprotein import, and contributes to efficient chloroplast biogenesis.
  • Publication
    Accès libre
    Identification of Plastoglobules as a Site of Carotenoid Cleavage
    (2016)
    Rottet, Sarah
    ;
    Devillers, Julie
    ;
    Glauser, Gaétan
    ;
    Douet, Véronique 
    ;
    Besagni, Céline
    ;
    Kessler, Félix 
    Carotenoids play an essential role in light harvesting and protection from excess light. During chloroplast senescence carotenoids are released from their binding proteins and are eventually metabolized. Carotenoid cleavage dioxygenase 4 (CCD4) is involved in carotenoid breakdown in senescing leaf and desiccating seed, and is part of the proteome of plastoglobules (PG), which are thylakoid-associated lipid droplets. Here, we demonstrate that CCD4 is functionally active in PG. Leaves of Arabidopsis thaliana ccd4 mutants constitutively expressing CCD4 fused to yellow fluorescent protein showed strong fluorescence in PG and reduced carotenoid levels upon dark- induced senescence. Lipidome-wide analysis indicated that ß-carotene, lutein, and violaxanthin were the principle substrates of CCD4 in vivo and were cleaved in senescing chloroplasts. Moreover, carotenoids were shown to accumulate in PG of ccd4 mutant plants during senescence, indicating translocation of carotenoids to PG prior to degradation.
  • Publication
    Accès libre
    Lipid Antioxidant and Galactolipid Remodeling under Temperature Stress in Tomato Plants
    (2016)
    Spicher, Livia
    ;
    Glauser, Gaétan
    ;
    Kessler, Félix 
    Increased temperatures are a major scenario in climate change and present a threat to plant growth and agriculture. Plant growth depends on photosynthesis. To function optimally, the photosynthetic machinery at the thylakoid membrane in chloroplasts continuously adapts to changing conditions. Here, we set out to discover the most important changes arising at the lipid level under high temperature (38°C) in comparison to mild (20°C) and moderately cold temperature (10°C) using a non- targeted lipidomics approach. To our knowledge, no comparable experiment at the level of the whole membrane system has been documented. Here, 791 molecular species were detected by mass spectrometry and ranged from membrane lipids, prenylquinones (tocopherols, phylloquinone, plastoquinone, plastochromanol), carotenoids (ß-carotene, xanthophylls) to numerous unidentified compounds. At high temperatures, the most striking changes were observed for the prenylquinones (a- tocopherol and plastoquinone/-ol) and the degree of saturation of fatty acids in galactolipids and phosphatidyl ethanolamine. Photosynthetic efficiency at high temperature was not affected but at moderately cold temperature mild photoinhibition occurred. The results indicate, that the thylakoid membrane is remodeled with regard to fatty acid saturation in galactolipids and lipid antioxidant concentrations under high temperature stress. The data strongly suggest, that massively increased concentrations of a-tocopherol and plastoquinone are important for protection against high temperature stress and proper function of the photosynthetic apparatus.
  • Publication
    Accès libre
    Down-regulation of tomato PHYTOL KINASE strongly impairs tocopherol biosynthesis and affects prenyllipid metabolism in an organ-specific manner
    (2016)
    Almeida, Juliana
    ;
    Azevedo, Mariana da Silva
    ;
    Spicher, Livia
    ;
    Glauser, Gaétan
    ;
    vom Dorp, Katharina
    ;
    Guyer, Luzia
    ;
    del Valle Carranza, Andrea
    ;
    Asis, Ramón
    ;
    de Souza, Amanda Pereira
    ;
    Buckeridge, Marcos
    ;
    Demarco, Diego
    ;
    Bres, Cécile
    ;
    Rothan, Christophe
    ;
    Peres, Lázaro Eustáquio Pereira
    ;
    Hörtensteiner, Stefan
    ;
    Kessler, Félix 
    ;
    Dörmann, Peter
    ;
    Carrari, Fernando
    ;
    Técnicas, Castelar, Argentina
    ;
    Rossi, Magdalena
    Tocopherol, a compound with vitamin E (VTE) activity, is a conserved constituent of the plastidial antioxidant network in photosynthetic organisms. The synthesis of tocopherol involves the condensation of an aromatic head group with an isoprenoid prenyl side chain. The latter, phytyl diphosphate, can be derived from chlorophyll phytol tail recycling, which depends on phytol kinase (VTE5) activity. How plants co- ordinate isoprenoid precursor distribution for supplying biosynthesis of tocopherol and other prenyllipids in different organs is poorly understood. Here, Solanum lycopersicum plants impaired in the expression of two VTE5-like genes identified by phylogenetic analyses, named SlVTE5 and SlFOLK, were characterized. Our data show that while SlFOLK does not affect tocopherol content, the production of this metabolite is >80% dependent on SlVTE5 in tomato, in both leaves and fruits. VTE5 deficiency greatly impacted lipid metabolism, including prenylquinones, carotenoids, and fatty acid phytyl esters. However, the prenyllipid profile greatly differed between source and sink organs, revealing organ-specific metabolic adjustments in tomato. Additionally, VTE5-deficient plants displayed starch accumulation and lower CO2 assimilation in leaves associated with mild yield penalty. Taken together, our results provide valuable insights into the distinct regulation of isoprenoid metabolism in leaves and fruits and also expose the interaction between lipid and carbon metabolism, which results in carbohydrate export blockage in the VTE5-deficient plants, affecting tomato fruit quality.
  • Publication
    Accès libre
    The role of plastoglobules in thylakoid lipid remodeling during plant development
    (2015)
    Rottet, Sarah
    ;
    Besagni, Céline
    ;
    Kessler, Félix 
    Photosynthesis is the key bioenergetic process taking place in the chloroplast. The components of the photosynthetic machinery are embedded in a highly dynamic matrix, the thylakoid membrane. This membrane has the capacity to adapt during developmental transitions and under stress conditions. The galactolipids are the major polar lipid components of the thylakoid membrane conferring bilayer properties, while neutral thylakoid lipids such as the prenyllipids and carotenoids contribute to essential functions such as electron transport and photoprotection. Despite a large number of studies, the intriguing processes of thylakoid membrane biogenesis and dynamics remain unsolved. Plastoglobules, thylakoid-associated lipid droplets, appear to actively participate in thylakoid function from biogenesis to senescence. Recruitment of specific proteins enables the plastoglobules to act in metabolite synthesis, repair and disposal under changing environmental conditions and developmental stages. In this review, we describe plastoglobules as thylakoid membrane microdomains and discuss their involvement in lipid remodeling during stress and in the conversion from one plastid type to another. This article is part of a Special Issue entitled: Chloroplast Biogenesis.
  • Publication
    Accès libre
    Unexpected roles of plastoglobules (plastid lipid droplets) in vitamin K1 and E metabolism
    (2015)
    Spicher, Livia
    ;
    Kessler, Félix 
    Tocopherol (vitamin E) and phylloquinone (vitamin K1) are lipid-soluble antioxidants that can only be synthesized by photosynthetic organisms. These compounds function primarily at the thylakoid membrane but are also present in chloroplast lipid droplets, also known as plastoglobules (PG). Depending on environmental conditions and stage of plant development, changes in the content, number and size of PG occur. PG are directly connected to the thylakoid membrane via the outer lipid leaflet. Apart from storage, PG are active in metabolism and likely trafficking of diverse lipid species. This review presents recent advances on how plastoglobules are implicated in the biosynthesis and metabolism of vitamin E and K.
  • Publication
    Accès libre
    Characterization of Chloroplast Protein Import without Tic56, a Component of the 1-Megadalton Translocon at the Inner Envelope Membrane of Chloroplasts
    (2015)
    Köhler, Daniel
    ;
    Montandon, Cyril
    ;
    Hause, Gerd
    ;
    Majovsky, Petra
    ;
    Kessler, Félix 
    ;
    Baginsky, Sacha
    ;
    Agne, Birgit
    We report on the characterization of Tic56, a unique component of the recently identified 1-MD translocon at the inner envelope membrane of chloroplasts (TIC) in Arabidopsis (Arabidopsis thaliana) comprising Tic20, Tic100, and Tic214. We isolated Tic56 by copurification with Tandem Affinity Purification-tagged Toc159 in the absence of precursor protein, indicating spontaneous and translocation-independent formation of the translocon at the outer envelope membrane of chloroplasts (TOC) and TIC supercomplexes. Tic56 mutant plants have an albino phenotype and are unable to grow without an external carbon source. Using specific enrichment of protein amino termini, we analyzed the tic56-1 and plastid protein import2 (toc159) mutants to assess the in vivo import capacity of plastids in mutants of an outer and inner envelope component of the anticipated TOC-TIC supercomplex. In both mutants, we observed processing of several import substrates belonging to various pathways. Our results suggest that despite the severe developmental defects, protein import into Tic56-deficient plastids is functional to a considerable degree, indicating the existence of alternative translocases at the inner envelope membrane.