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Dernière mise à jour : Mai 2018

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Institut Sophia Agrobiotech

UMR INRA - Univ. Nice Sophia Antipolis - Cnrs

http://www.paca.inra.fr/institut-sophia-agrobiotech_eng/

Ph defence - Laïla Giordano

Monday 16 december - 14:00 - Sophia Antipolis - Inra PACA - Salle A010

Soutenance de thèse
Laïla Giordano: "Effet de la diversification spatiale et temporelle des cultures à l’échelle du paysage agricole sur le biocontrôle et les ravageurs de culture"

Abstract

Plant cells have a diversifying number of plasma membrane-localized receptors, which are specialized in detecting environmental changes and allow the plant to adapt accordingly. About 200 of these receptors are composed of an extracellular domain with leucine-rich repeats (LRR) and an intracellular kinase domain. We have previously identified a member of this receptor family in Arabidopsis, which contributes to the infection success by biotrophic filamentous pathogens, such as the oomycete Hyaloperonospora arabidopsidis (Hpa). The plant mutant for the receptor gene loses its susceptibility to infection, and according to this phenotype the receptor has been named "Impaired Oomycete Susceptibility 1" (IOS1). IOS1 negatively regulates the abscisic acid (ABA) hormone signaling pathway upon infection. In addition, the receptor has been shown to be part of a plasma membrane receptor complex that detects bacterial infections and triggers innate immunity. The extracellular region of IOS1 harbors an additional so-called Malectin-Like Domain (MLD), which has strong structural similarities to animal malectin. Animal malectin resides in the endoplasmic reticulum (ER), where it interacts with ribophorins from the oligosaccharyltransferase (OST) complex. Proteins from this complex ensure post-translational protein maturation by adding N-glycosylations. Ribophorins monitor the correct folding of neo-synthetized glycoproteins. Environmental changes frequently alter the rate of proteins that are produced and require maturation. If monitoring system is not efficient, neo-synthetized proteins accumulate in the ER and generate the "Unfolded Protein Response" (UPR). The mechanism for controlling glycoprotein maturation and the UPR also exist in plant cells. In order to characterize the functions of the extracellular domain (ED) of IOS1, we show by confocal laser-scanning microscopy that the MLD mediates a retention of the receptor in the ER. Here, the MLD of the receptor attenuates the UPR, which is triggered by the oomycete infection. We identified the plant ribophorin HAP6 and the cell death attenuator Bax-Inhibitor-1 (BI-1) as ER-residing proteins that interact with the ED of IOS1. In functional complementation experiments involving the ios1-1 mutant transformed with individual IOS1 domains, we further evaluated the role of IOS1 and the MLD in the plant responses to ER and ABA stress signaling. We show that the MLD attenuates the UPR during the plant-oomycete interaction, thus promoting successful infection. We also show that ABA signaling correlates positively with the UPR, indicating that the observed IOS1-mediated regulation of hormone signaling is a consequence of interference with the UPR. Taken together, our data suggest that individual domains of the IOS1 receptor target distinct functions in different subcellular compartments.

  • Encadrée par Harald Keller 

Devant le jury composé de :

  • Sylvie German-Retana, Directrice de Recherche INRA au Laboratoire de Biologie du Fruit et Pathologie de Bordeaux, France
  • Aurélien Boisson-Dernier, Responsable d’équipe à l’Institut de Botanique de l’Université de Cologne, Allemagne
  • Benoit Lefebvre, Chargé de recherche INRA au Laboratoire des Interactions Plantes-Microbes, Toulouse, France
  • Béatrice Bailly-Maitre, Chargée de recherche INSERM au Centre Méditerranéen de Médecine Moléculaire, Nice, France