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Giron D.,CNRS Research Institute of Insect Biology | Glevarec G.,CNRS Biomolecule and Plant Biotechnology Laboratory
Journal of Chemical Ecology | Year: 2014

Recently, a renewed interest in cytokinins (CKs) has allowed the characterization of these phytohormones as key regulatory molecules in plant biotic interactions. They have been proved to be instrumental in microbe- and insect-mediated plant phenotypes that can be either beneficial or detrimental for the host-plant. In parallel, insect endosymbiotic bacteria have emerged as key players in plant-insect interactions mediating directly or indirectly fundamental aspects of insect nutrition, such as insect feeding efficiency or the ability to manipulate plant physiology to overcome food nutritional imbalances. However, mechanisms that regulate CK production and the role played by insects and their endosymbionts remain largely unknown. Against this backdrop, studies on plant-associated bacteria have revealed fascinating and complex molecular mechanisms that lead to the production of bacterial CKs and the modulation of plant-borne CKs which ultimately result in profound metabolic and morphological plant modifications. This review highlights major strategies used by plant-associated bacteria that impact the CK homeostasis of their host-plant, to raise parallels with strategies used by phytophagous insects and to discuss the possible role played by endosymbiotic bacteria in these CK-mediated plant phenotypes. We hypothesize that insects employ a CK-mix production strategy that manipulates the phytohormonal balance of their host-plant and overtakes plant gene expression causing a metabolic and morphological habitat modification. In addition, insect endosymbiotic bacteria may prove to be instrumental in these manipulations through the production of bacterial CKs, including specific forms that challenge the CK-degrading capacity of the plant (thus ensuring persistent effects) and the CK-mediated plant defenses. © 2014 Springer Science+Business Media New York.

Jousset A.,University of Gottingen | Rochat L.,University of Lausanne | Lanoue A.,CNRS Biomolecule and Plant Biotechnology Laboratory | Bonkowski M.,University of Cologne | And 2 more authors.
Molecular Plant-Microbe Interactions | Year: 2011

Plant health and fitness widely depend on interactions with soil microorganisms. Some bacteria such as pseudomonads can inhibit pathogens by producing antibiotics, and controlling these bacteria could help improve plant fitness. In the present study, we tested whether plants induce changes in the antifungal activity of root-associated bacteria as a response to root pathogens. We grew barley plants in a split-root system with one side of the root system challenged by the pathogen Pythium ultimum and the other side inoculated with the biocontrol strain Pseudomonas fluorescens CHA0. We used reporter genes to follow the expression of ribosomal RNA indicative of the metabolic state and of the gene phlA, required for production of 2,4-diacetylphloroglucinol, a key component of antifungal activity. Infection increased the expression of the antifungal gene phlA. No contact with the pathogen was required, indicating that barley influenced gene expression by the bacteria in a systemic way. This effect relied on increased exudation of diffusible molecules increasing phlA expression, suggesting that communication with rhizosphere bacteria is part of the pathogen response of plants. Tripartite interactions among plants, pathogens, and bacteria appear as a novel determinant of plant response to root pathogens. © 2011 The American Phytopathological Society.

Chapeland-Leclerc F.,University of Paris Descartes | Hennequin C.,Laboratoire Of Parasitologie Mycologie | Papon N.,CNRS Biomolecule and Plant Biotechnology Laboratory | Noel T.,University of Bordeaux Segalen | And 4 more authors.
Antimicrobial Agents and Chemotherapy | Year: 2010

We describe the acquisition of flucytosine, azole, and caspofungin resistance in sequential Candida glabrata bloodstream isolates collected from a bone marrow transplant patient with clinical failure. Point mutations in C. glabrata FUR1 (CgFUR1) and CgFKS2 and overexpression of CgCDR1 and CgCDR2 were observed in resistant isolates. Copyright © 2010, American Society for Microbiology. All Rights Reserved.

Giron D.,CNRS Research Institute of Insect Biology | Frago E.,University of Oxford | Glevarec G.,CNRS Biomolecule and Plant Biotechnology Laboratory | Pieterse C.M.J.,University Utrecht | Dicke M.,Wageningen University
Functional Ecology | Year: 2013

Plant hormones play important roles in regulating plant growth and defence by mediating developmental processes and signalling networks involved in plant responses to a wide range of parasitic and mutualistic biotic interactions. Plants are known to rapidly respond to pathogen and herbivore attack by reconfiguring their metabolism to reduce pathogen/herbivore food acquisition. This involves the production of defensive plant secondary compounds, but also an alteration of the plant primary metabolism to fuel the energetic requirements of the direct defence. Cytokinins are plant hormones that play a key role in plant morphology, plant defence, leaf senescence and source-sink relationships. They are involved in numerous plant-biotic interactions. These phytohormones may have been the target of arthropods and pathogens over the course of the evolutionary arms race between plants and their biotic partners to hijack the plant metabolism, control its physiology and/or morphology and successfully invade the plant. In the case of arthropods, cytokinin-induced phenotypes can be mediated by their bacterial symbionts, giving rise to intricate plant-microbe-insect interactions. Cytokinin-mediated effects strongly impact not only plant growth and defence but also the whole community of insect and pathogen species sharing the same plant by facilitating or preventing plant invasion. This suggests that cytokinins (CKs) are key regulators of the plant growth-defence trade-off and highlights the complexity of the finely balanced responses that plants use while facing both invaders and mutualists. © 2013 The Authors. Functional Ecology © 2013 British Ecological Society.

Cannesan M.A.,University of Rouen | Gangneux C.,Laboratoire Biosol | Lanoue A.,CNRS Biomolecule and Plant Biotechnology Laboratory | Giron D.,CNRS Research Institute of Insect Biology | And 4 more authors.
Annals of Botany | Year: 2011

•Background and Aims: The oomycete Aphanomyces euteiches causes up to 80% crop loss in pea (Pisum sativum). Aphanomyces euteiches invades the root system leading to a complete arrest of root growth and ultimately to plant death. To date, disease control measures are limited to crop rotation and no resistant pea lines are available. The present study aims to get a deeper understanding of the early oomyceteplant interaction at the tissue and cellular levels. •Methods: Here, the process of root infection by A. euteiches on pea is investigated using flow cytometry and microscopic techniques. Dynamic changes in secondary metabolism are analysed with high-performance liquid chromatography with diode-array detection. •Key Results: Root infection is initiated in the elongation zone but not in the root cap and border cells. Border-cell production is significantly enhanced in response to root inoculation with changes in their size and morphology. The stimulatory effect of A. euteiches on border-cell production is dependent on the number of oospores inoculated. Interestingly, border cells respond to pathogen challenge by increasing the synthesis of the phytoalexin pisatin. •Conclusions: Distinctive responses to A. euteiches inoculation occur at the root tissue level. The findings suggest that root border cells in pea are involved in local defence of the root tip against A. euteiches. Root border cells constitute a convenient quantitative model to measure the molecular and cellular basis of plantmicrobe interactions. © The Author 2011. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.

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