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Longoni, Fiamma

Nom
Longoni, Fiamma
Affiliation principale
Fonction
Ancien.ne collaborateur.trice
Identifiants
https://libra.unine.ch/handle/123456789/1316

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  • 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
    The kinase STATE TRANSITION 8 phosphorylates Light Harvesting Complex II and contributes to light acclimation in Arabidopsis thaliana
    (2019-9-19)
    Longoni, Fiamma 
    ;
    Samol, Iga
    ;
    Goldschmidt-Clermont, Michel
    Phosphorylation of the light-harvesting complex II (LHCII) is a central trigger for the reorganization of the photosynthetic complexes in the thylakoid membrane during short-term light acclimation. The major kinase involved in LHCII phosphorylation is STATE TRANSITION 7 (STN7), and its activity is mostly counteracted by a thylakoid-associated phosphatase, PROTEIN PHOSPHATASE 1/THYLAKOID ASSOCIATED PHOSPHATASE 38 (PPH1/TAP38). This kinase/phosphatase pair responds to the redox status of the photosynthetic electron transport chain. In Arabidopsis thaliana, Lhcb1 and Lhcb2 subunits of the LHCII trimers are the major targets of phosphorylation and have different roles in the acclimation of the photosynthetic machinery. Another antagonistic kinase and phosphatase pair, STATE TRANSITION 8 (STN8) and PHOTOSYSTEM II PHOSPHATASE (PBCP) target a different set of thylakoid proteins. Here, we analyzed double, triple, and quadruple knockout mutants of these kinases and phosphatases. In multiple mutants, lacking STN7, in combination with one or both phosphatases, but not STN8, the phosphorylation of LHCII was partially restored. The recovered phosphorylation favors Lhcb1 over Lhcb2 and results in a better adaptation of the photosynthetic apparatus and increased plant growth under fluctuating light. This set of mutants allowed to unveil a contribution of STN8-dependent phosphorylation in the acclimation to rapid light variations.
  • 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
    Production by Tobacco Transplastomic Plants of Recombinant Fungal and Bacterial Cell-Wall Degrading Enzymes to Be Used for Cellulosic Biomass Saccharification
    (2015-6-2)
    Longoni, Fiamma 
    ;
    Leelavathi, Sadhu
    ;
    Doria, Enrico
    ;
    Vanga, Siva Reddy
    ;
    Cella, Rino
    Biofuels from renewable plant biomass are gaining momentum due to climate change related to atmospheric CO2 increase. However, the production cost of enzymes required for cellulosic biomass saccharification is a major limiting step in this process. Low-cost production of large amounts of recombinant enzymes by transgenic plants was proposed as an alternative to the conventional microbial based fermentation. A number of studies have shown that chloroplast-based gene expression offers several advantages over nuclear transformation due to efficient transcription and translation systems and high copy number of the transgene. In this study, we expressed in tobacco chloroplasts microbial genes encoding five cellulases and a polygalacturonase. Leaf extracts containing the recombinant enzymes showed the ability to degrade various cell-wall components under different conditions, singly and in combinations. In addition, our group also tested a previously described thermostable xylanase in combination with a cellulase and a polygalacturonase to study the cumulative effect on the depolymerization of a complex plant substrate. Our results demonstrate the feasibility of using transplastomic tobacco leaf extracts to convert cell-wall polysaccharides into reducing sugars, fulfilling a major prerequisite of large scale availability of a variety of cell-wall degrading enzymes for biofuel industry.