Marie-cecile Caillaud

Publications (9) View all

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  Available from: Marie-cecile Caillaud

  Article: Characterization of the membrane-associated HaRxL17 Hpa effector candidate.

  Marie-Cécile Caillaud, Sophie J M Piquerez, Jonathan D G Jones
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  ABSTRACT: We examined changes to subcellular architecture during the compatible interaction between the biotroph pathogen Hyaloperonospora arabidopsidis (Hpa) and its host Arabidopsis. Live-cell imaging highlighted rearrangements in plant cell membranes upon infection. In particular, the tonoplast appeared close to the extrahaustorial membrane surrounding the haustorium. We investigated the subcellular localization patterns of Hpa RxLR effector candidates (HaRxLs) in planta. This subcellular localization screening led to the identification of an extrahaustorial membrane-localized effector, HaRxL17 that when stably expressed in Arabidopsis increased plant susceptibility to Hpa during compatible and incompatible interactions. Here, we report that the N-terminal part of HaRxL17 is sufficient to target the plant cell membranes. We showed that both C- or N-terminal fluorescent-tagged HaRxL17 localizes around Hpa haustoria, in early and in late stages of infection. As with Hpa infection, GFP-HaRxL17 also localizes around haustoria during infection with Albugo laibachii. Thus, HaRxL17 that increases plant susceptibility to Hpa during both compatible and incompatible interactions, localizes around oomycete haustoria when stably expressed in Arabidopsis.
  Plant signaling & behavior 01/2012; 7(1):145-9.
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  Available from: Rebecca L Allen

  Article: Multiple candidate effectors from the oomycete pathogen Hyaloperonospora arabidopsidis suppress host plant immunity.

  Georgina Fabro, Jens Steinbrenner, Mary Coates, Naveed Ishaque, Laura Baxter, David J Studholme, Evelyn Körner, Rebecca L Allen, Sophie J M Piquerez, Alejandra Rougon-Cardoso, David Greenshields, Rita Lei, Jorge L Badel, Marie-Cecile Caillaud, Kee-Hoon Sohn, Guido Van den Ackerveken, Jane E Parker, Jim Beynon, Jonathan D G Jones
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  ABSTRACT: Oomycete pathogens cause diverse plant diseases. To successfully colonize their hosts, they deliver a suite of effector proteins that can attenuate plant defenses. In the oomycete downy mildews, effectors carry a signal peptide and an RxLR motif. Hyaloperonospora arabidopsidis (Hpa) causes downy mildew on the model plant Arabidopsis thaliana (Arabidopsis). We investigated if candidate effectors predicted in the genome sequence of Hpa isolate Emoy2 (HaRxLs) were able to manipulate host defenses in different Arabidopsis accessions. We developed a rapid and sensitive screening method to test HaRxLs by delivering them via the bacterial type-three secretion system (TTSS) of Pseudomonas syringae pv tomato DC3000-LUX (Pst-LUX) and assessing changes in Pst-LUX growth in planta on 12 Arabidopsis accessions. The majority (~70%) of the 64 candidates tested positively contributed to Pst-LUX growth on more than one accession indicating that Hpa virulence likely involves multiple effectors with weak accession-specific effects. Further screening with a Pst mutant (ΔCEL) showed that HaRxLs that allow enhanced Pst-LUX growth usually suppress callose deposition, a hallmark of pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI). We found that HaRxLs are rarely strong avirulence determinants. Although some decreased Pst-LUX growth in particular accessions, none activated macroscopic cell death. Fewer HaRxLs conferred enhanced Pst growth on turnip, a non-host for Hpa, while several reduced it, consistent with the idea that turnip's non-host resistance against Hpa could involve a combination of recognized HaRxLs and ineffective HaRxLs. We verified our results by constitutively expressing in Arabidopsis a sub-set of HaRxLs. Several transgenic lines showed increased susceptibility to Hpa and attenuation of Arabidopsis PTI responses, confirming the HaRxLs' role in Hpa virulence. This study shows TTSS screening system provides a useful tool to test whether candidate effectors from eukaryotic pathogens can suppress/trigger plant defense mechanisms and to rank their effectiveness prior to subsequent mechanistic investigation.
  PLoS Pathogens 11/2011; 7(11):e1002348. · 9.13 Impact Factor
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  Available from: Marie-cecile Caillaud

  Article: Subcellular localization of the Hpa RxLR effector repertoire identifies a tonoplast-associated protein HaRxL17 that confers enhanced plant susceptibility.

  Marie-Cécile Caillaud, Sophie J M Piquerez, Georgina Fabro, Jens Steinbrenner, Naveed Ishaque, Jim Beynon, Jonathan D G Jones
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  ABSTRACT: Filamentous phytopathogens form sophisticated intracellular feeding structures called haustoria in plant cells. Pathogen effectors are likely to play a role in the establishment and maintenance of haustoria in addition to their better-characterized role in suppressing plant defence. However, the specific mechanisms by which these effectors promote virulence remain unclear. To address this question, we examined changes in subcellular architecture using live-cell imaging during the compatible interaction between the oomycete Hyaloperonospora arabidopsidis (Hpa) and its host Arabidopsis. We monitored host-cell restructuring of subcellular compartments within plant mesophyll cells during haustoria ontogenesis. Live-cell imaging highlighted rearrangements in plant cell membranes upon infection, in particular to the tonoplast, which was located close to the extra-haustorial membrane surrounding the haustorium. We also investigated the subcellular localization patterns of Hpa RxLR effector candidates (HaRxLs) in planta. We identified two major classes of HaRxL effector based on localization: nuclear-localized effectors and membrane-localized effectors. Further, we identified a single effector, HaRxL17, that associated with the tonoplast in uninfected cells and with membranes around haustoria, probably the extra-haustorial membrane, in infected cells. Functional analysis of selected effector candidates in planta revealed that HaRxL17 enhances plant susceptibility. The roles of subcellular changes and effector localization, with specific reference to the potential role of HaRxL17 in plant cell membrane trafficking, are discussed with respect to Hpa virulence.
  The Plant Journal 09/2011; 69(2):252-65. · 6.16 Impact Factor
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  Available from: Marie-cecile Caillaud

  Article: Spindle assembly checkpoint protein dynamics reveal conserved and unsuspected roles in plant cell division.

  Marie-Cécile Caillaud, Laetitia Paganelli, Philippe Lecomte, Laurent Deslandes, Michaël Quentin, Yann Pecrix, Manuel Le Bris, Nicolas Marfaing, Pierre Abad, Bruno Favery
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  ABSTRACT: In eukaryotes, the spindle assembly checkpoint (SAC) ensures that chromosomes undergoing mitosis do not segregate until they are properly attached to the microtubules of the spindle. We investigated the mechanism underlying this surveillance mechanism in plants, by characterising the orthogolous SAC proteins BUBR1, BUB3 and MAD2 from Arabidopsis. We showed that the cell cycle-regulated BUBR1, BUB3.1 and MAD2 proteins interacted physically with each other. Furthermore, BUBR1 and MAD2 interacted specifically at chromocenters. Following SAC activation by global defects in spindle assembly, these three interacting partners localised to unattached kinetochores. In addition, in cases of 'wait anaphase', plant SAC proteins were associated with both kinetochores and kinetochore microtubules. Unexpectedly, BUB3.1 was also found in the phragmoplast midline during the final step of cell division in plants. We conclude that plant BUBR1, BUB3.1 and MAD2 proteins may have the SAC protein functions conserved from yeast to humans. The association of BUB3.1 with both unattached kinetochore and phragmoplast suggests that in plant, BUB3.1 may have other roles beyond the spindle assembly checkpoint itself. Finally, this study of the SAC dynamics pinpoints uncharacterised roles of this surveillance mechanism in plant cell division.
  PLoS ONE 02/2009; 4(8):e6757. · 4.09 Impact Factor
• Article: Cytoskeleton reorganization, a key process in root-knot nematode-induced giant cell ontogenesis

  M. C. Caillaud, P. Abad, B. Favery
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  ABSTRACT: Root-knot nematodes are plant parasitic worms that establish and maintain an intimate relationship with their host plants. RKN induce the redifferentiation of root cells into multinucleate and hypertrophied giant cells essential for nematode growth and reproduction. Major rearrangements of the cytoskeleton occur during giant cell formation. We characterized the first plant candidate genes implicated in giant cell actin and microtubule cytoskeleton reorganization. We showed previously that formins may regulate giant cell isotropic growth by controlling the assembly of actin cables. Recently we demonstrated that a Microtubule-Associated Protein, MAP65-3, is essential for giant cell development. In the absence of functional MAP65-3, giant cells started to develop but failed to fully differentiate and were eventually destroyed. In developing giant cells, MAP65-3 was associated with a novel kind of cell plate-the giant cell mini cell plate-that separates daughter nuclei. Despite karyokinesis occurs without cell division in giant cell, we demonstrated that cytokinesis is initiated and required for successful pathogen growth and development.
  Plant signaling & behavior 11/2008; 3(10):816-8.