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Author

Aude Cerutti

Bio: Aude Cerutti is an academic researcher from Paul Sabatier University. The author has contributed to research in topics: Hydathode & Xanthomonas campestris. The author has an hindex of 6, co-authored 17 publications receiving 118 citations. Previous affiliations of Aude Cerutti include University of Toulouse & Institut national de la recherche agronomique.

Papers
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Journal ArticleDOI
TL;DR: It is shown that the hydrolase CbsA acts as a phenotypic switch between vascular and nonvascular plant pathogenesis, demonstrating how the gain and loss of single loci can facilitate the evolution of complex ecological traits.
Abstract: Vascular plant pathogens travel long distances through host veins, leading to life-threatening, systemic infections. In contrast, nonvascular pathogens remain restricted to infection sites, triggering localized symptom development. The contrasting features of vascular and nonvascular diseases suggest distinct etiologies, but the basis for each remains unclear. Here, we show that the hydrolase CbsA acts as a phenotypic switch between vascular and nonvascular plant pathogenesis. cbsA was enriched in genomes of vascular phytopathogenic bacteria in the family Xanthomonadaceae and absent in most nonvascular species. CbsA expression allowed nonvascular Xanthomonas to cause vascular blight, while cbsA mutagenesis resulted in reduction of vascular or enhanced nonvascular symptom development. Phylogenetic hypothesis testing further revealed that cbsA was lost in multiple nonvascular lineages and more recently gained by some vascular subgroups, suggesting that vascular pathogenesis is ancestral. Our results overall demonstrate how the gain and loss of single loci can facilitate the evolution of complex ecological traits.

44 citations

Journal ArticleDOI
TL;DR: Recent progress on genetic manipulation and in vitro differentiation models now offers interesting perspectives for tackling key biological questions related to this particularly important developmental stage of toxoplasmosis, called bradyzoite.
Abstract: Toxoplasma gondii is a ubiquitous parasitic protist found in a wide variety of hosts, including a large proportion of the human population. Beyond an acute phase which is generally self-limited in immunocompetent individuals, the ability of the parasite to persist as a dormant stage, called bradyzoite, is an important aspect of toxoplasmosis. Not only is this stage not eliminated by current treatments, but it can also reactivate in immunocompromised hosts, leading to a potentially fatal outcome. Yet, despite its critical role in the pathology, the bradyzoite stage is relatively understudied. One main explanation is that it is a considerably challenging model, which essentially has to be derived from in vivo sources. However, recent progress on genetic manipulation and in vitro differentiation models now offers interesting perspectives for tackling key biological questions related to this particularly important developmental stage.

43 citations

Journal ArticleDOI
TL;DR: Results give a detailed anatomic description of Brassicaceae hydathodes and highlight the efficient use of this tissue as an initial niche for subsequent vascular systemic dissemination of Xcc in distant plant tissues.
Abstract: Hydathodes are water pores found on leaves of a wide range of vascular plants and are the sites of guttation. We report here on the detailed anatomy of cauliflower (Brassicaoleracea) and Arabidopsis (Arabidopsis thaliana) hydathodes. Hydathode surface presents pores resembling stomata giving access to large cavities. Beneath, the epithem is composed of a lacunar and highly vascularized parenchyma offering a direct connection between leaf surface and xylem vessels. Arabidopsis hydathode pores were responsive to ABA and light similar to stomata. The flg22 flagellin peptide, a well-characterized elicitor of plant basal immunity, did not induce closure of hydathode pores in contrast to stomata. Because hydathodes are natural infection routes for several pathogens, we investigated hydathode infection by the adapted vascular phytopathogenic bacterium Xanthomonas campestris pv campestris (Xcc), the causal agent of black rot disease of Brassicaceae. Microscopic observations of hydathodes six days postinoculation indicated a digestion of the epithem cells and a high bacterial multiplication. Postinvasive immunity was shown to limit pathogen growth in the epithem and is actively suppressed by the type III secretion system and its effector proteins. Altogether, these results give a detailed anatomic description of Brassicaceae hydathodes and highlight the efficient use of this tissue as an initial niche for subsequent vascular systemic dissemination of Xcc in distant plant tissues.

43 citations

Journal ArticleDOI
TL;DR: This review refining the definition of hydathodes and illustrating their important roles in the maintenance of plant osmotic balance, nutrient retrieval, and exclusion of deleterious chemicals from the xylem sap presents the current understanding of the infection ofHydathodes by adapted vascular pathogens and the associated plant immune responses.
Abstract: Hydathodes are organs found on aerial parts of a wide range of plant species that provide almost direct access for several pathogenic microbes to the plant vascular system. Hydathodes are better known as the site of guttation, which is the release of droplets of plant apoplastic fluid to the outer leaf surface. Because these organs are only described through sporadic allusions in the literature, this review aims to provide a comprehensive view of hydathode development, physiology, and immunity by compiling a historic and contemporary bibliography. In particular, we refine the definition of hydathodes.We illustrate their important roles in the maintenance of plant osmotic balance, nutrient retrieval, and exclusion of deleterious chemicals from the xylem sap. Finally, we present our current understanding of the infection of hydathodes by adapted vascular pathogens and the associated plant immune responses.

27 citations

Journal ArticleDOI
TL;DR: A large and polymorphic repertoire of TALEs opens novel perspectives for elucidating TALE-mediated susceptibility of Brassicaceae to black rot disease and for understanding the molecular processes underlying TALE evolution.
Abstract: Xanthomonas transcription activator-like effectors (TALEs) are injected inside plant cells to promote host susceptibility by enhancing transcription of host susceptibility genes. TALE-encoding (tal) genes were thought to be absent from Brassicaceae-infecting Xanthomonas campestris (Xc) genomes based on four reference genomic sequences. We discovered tal genes in 26 of 49 Xc strains isolated worldwide and used a combination of single molecule real time (SMRT) and tal amplicon sequencing to yield a near-complete description of the TALEs found in Xc (Xc TALome). The 53 sequenced tal genes encode 21 distinct DNA binding domains that sort into seven major DNA binding specificities. In silico analysis of the Brassica rapa promoterome identified a repertoire of predicted TALE targets, five of which were experimentally validated using quantitative reverse transcription polymerase chain reaction. The Xc TALome shows multiple signs of DNA rearrangements that probably drove its evolution from two ancestral tal genes. We discovered that Tal12a and Tal15a of Xcc strain Xca5 contribute together in the development of disease symptoms on susceptible B.oleracea var. botrytis cv Clovis. This large and polymorphic repertoire of TALEs opens novel perspectives for elucidating TALE-mediated susceptibility of Brassicaceae to black rot disease and for understanding the molecular processes underlying TALE evolution.

20 citations


Cited by
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01 Sep 2016
TL;DR: The first genome-wide genetic screen of an apicomplexan parasite is presented, revealing essential functions during infection of human cells and providing broad-based functional information on T. gondii genes that will facilitate future approaches to expand the horizon of antiparasitic interventions.
Abstract: National Institute of General Medical Sciences (U.S.) (Center for Integrative Synthetic Biology Grant P50GM098792)

456 citations

01 Apr 2012
TL;DR: This paper showed that in two recently diverged populations of ocean bacteria, ecological differentiation has occurred akin to a sexual mechanism: a few genome regions have swept through subpopulations in a habitat-specific manner, accompanied by gradual separation of gene pools as evidenced by increased habitat specificity of the most recent recombinations.
Abstract: Some Sort of Species Certain populations of bacteria are known to show ecological differentiation, but how this happens has remained controversial. Shapiro et al. (p. 48; see the Perspective by Papke and Gogarten) examined whole-genome sequences from ecologically divergent Vibrio populations and found that genes and genome regions containing so-called “eco-SNPs” (single-nuleotide polymorphisms) have swept through populations. These regions differentiate the bacteria genetically, apparently according to the type of substratum on which they live. Subsequently, tight genotypic clusters may have emerged as a result of preferential recombination occurring within particular habitats. Although specialization into different habitats may reduce gene flow between bacterial populations, the bacteria will always remain open to taking up DNA from other populations and so they cannot be said to be species in the eukaryotic sense. Ecologically separated Vibrio populations diverge by gene-specific rather than genome-wide selective sweeps. Genetic exchange is common among bacteria, but its effect on population diversity during ecological differentiation remains controversial. A fundamental question is whether advantageous mutations lead to selection of clonal genomes or, as in sexual eukaryotes, sweep through populations on their own. Here, we show that in two recently diverged populations of ocean bacteria, ecological differentiation has occurred akin to a sexual mechanism: A few genome regions have swept through subpopulations in a habitat-specific manner, accompanied by gradual separation of gene pools as evidenced by increased habitat specificity of the most recent recombinations. These findings reconcile previous, seemingly contradictory empirical observations of the genetic structure of bacterial populations and point to a more unified process of differentiation in bacteria and sexual eukaryotes than previously thought.

397 citations

01 Jan 1991
TL;DR: All Xanthomonas campestris pathovars tested contain DNA which hybridizes to the large hrp gene cluster of Pseudomonas solanacearum, suggesting the existence of two independent sets of pathogenicity genes that are regulated differently.
Abstract: All Xanthomonas campestris pathovars tested contain DNA which hybridizes to the large hrp gene cluster of Pseudomonas solanacearum (C.A. Boucher, F. Van Gijsegem, P.A. Barberis, M. Arlat, and C. Zischek, J. Bacteriol. 169:5626-5632, 1987). Clones carrying these sequences were isolated from genomic libraries of X. campestris pvs. campestris and vitians. Mutagenesis of the corresponding genomic regions of both pathovars gave strains defective in both pathogenicity and hypersensitive response induction. X. c. pv. campestris contained a hrp gene cluster covering about 25 kb, which was homologous and colinear over a continuous 19-kb DNA region with the P. solanacearum hrp cluster. Cross-complementation showed that X. c. pv. vitians and X. c. pv. campestris hrp sequences are functionally interchangeable, but the source of the hrp genes did not determine the compatibility-incompatibility of the host-pathogen interaction. One X. c. pv. campestris Hrp- mutant was "complemented" by specific subclones of the P. solanacearum hrp cluster, suggesting the existence of some functional homology between the clusters of the two species. Expression of hrp genes (studied by lacZ fusions) was repressed in rich medium, and in minimal medium the level of expression depended on the carbon source supplied to the cells. Transcription of hrp genes was not regulated by genes that control the synthesis of extracellular enzymes, which are required for pathogenicity. In addition X. campestris Hrp- mutants produced wild-type levels of these extracellular enzyme activities. These results suggest the existence of two independent sets of pathogenicity genes that are regulated differently.

137 citations

Journal ArticleDOI
TL;DR: The current knowledge on the infection strategies and regulatory networks controlling virulence and adaptation mechanisms from Xanthomonas species are summarized and the novel opportunities that this body of work has provided for disease control and plant health are discussed.
Abstract: Xanthomonas is a well-studied genus of bacterial plant pathogens whose members cause a variety of diseases in economically important crops worldwide. Genomic and functional studies of these phytopathogens have provided significant understanding of microbial-host interactions, bacterial virulence and host adaptation mechanisms including microbial ecology and epidemiology. In addition, several strains of Xanthomonas are important as producers of the extracellular polysaccharide, xanthan, used in the food and pharmaceutical industries. This polymer has also been implicated in several phases of the bacterial disease cycle. In this review, we summarise the current knowledge on the infection strategies and regulatory networks controlling virulence and adaptation mechanisms from Xanthomonas species and discuss the novel opportunities that this body of work has provided for disease control and plant health.

136 citations

Journal ArticleDOI
TL;DR: In this paper, the authors integrate theoretical and empirical findings to discuss the mechanisms underpinning these evolutionary shifts, as well as the ecological drivers and why some host-microorganism interactions may be stuck at the end of the continuum.
Abstract: Virtually all plants and animals, including humans, are home to symbiotic microorganisms. Symbiotic interactions can be neutral, harmful or have beneficial effects on the host organism. However, growing evidence suggests that microbial symbionts can evolve rapidly, resulting in drastic transitions along the parasite-mutualist continuum. In this Review, we integrate theoretical and empirical findings to discuss the mechanisms underpinning these evolutionary shifts, as well as the ecological drivers and why some host-microorganism interactions may be stuck at the end of the continuum. In addition to having biomedical consequences, understanding the dynamic life of microorganisms reveals how symbioses can shape an organism's biology and the entire community, particularly in a changing world.

85 citations