Plusieurs niveaux de contrôle sont mis en jeu lors de flétrissement bactérien chez la légumineuse modèle Medicago truncatula

Nous présentons l étude de l interaction entre la bactérie pathogène racinaire Ralstonia solanacearum et la légumineuse modèle Medicago truncatula. Un pathosystème avec les lignées A17 et F83005.5, respectivement sensible et résistante à la souche GMI1000, a été mis en place avec une procédure d inoculation sur racines intactes. Ce dispositif expérimental nous a permis de suivre le processus infectieux, de la pénétration de la bactérie par l extrémité racinaire au développement des symptômes foliaires. L analyse des étapes précoces de l interaction a permis de décrire l apparition de symptômes racinaires qui se mettent en place rapidement après l infection, que les lignées soient résistantes ou sensibles à la bactérie. Un arrêt de croissance de la racine s'observe dès 24 heures post-inoculation, ainsi qu une mortalité de l épiderme de l extrémité racinaire. Ces phénotypes sont notés suite à des inoculations avec de faibles concentrations bactériennes, et ce sur plusieurs espèces hôtes ou non-hôtes testées. La mise en place des symptômes racinaires est dépendante de l appareil de sécrétion de type III. Un crible de mutants d effecteurs de type III de la souche GMI1000, basé sur l apparition des symptômes racinaires, a permis de montrer que des pools différents d effecteurs interviennent chez A17 et F83005.5. Chez la lignée sensible A17, deux effecteurs sont principalement impliqués, Gala7 et AvrA. L étude de la colonisation de cette lignée a montré que le mutant gala7 ne pénètre pas la plante et n induit pas de symptômes de flétrissement. Le mutant avrA s est révélé capable d induire la maladie chez la lignée A17 mais de manière nettement réduite par rapport à la souche sauvage. L analyse des extrémités racinaires des lignées sensible et résistante infectées par la souche GMI1000 a révélé qu au niveau des parois de l endoderme, la présence de lignine est induite de manière plus précoce chez la lignée résistante. Des phénomènes de division cellulaire ont été identifiés autour du cylindre central et semblent également liés à une restriction de la propagation bactérienne. Au niveau du contenu cellulaire, une autofluorescence et une production de ROS semblent liés à une phase nécrotrophe de la bactérie lors de sa propagation dans la zone corticale de l extrémité racinaire. L étude de la colonisation bactérienne en s affranchissant de l étape de pénétration a révélé que des mécanismes de résistances peuvent intervenir au niveau de collet chez la lignée F83005.5 et lors de la colonisation racinaire des vaisseaux conducteurs suite à une inoculation avec le mutant gala7ManquantTOULOUSE-ENSAT-Documentation (315552324) / SudocSudocFranceF

Genomics and transcriptomics of Xanthomonas campestris species challenge the concept of core type III effectome

The bacterial species Xanthomonas campestris infects a wide range of Brassicaceae. Specific pathovars of this species cause black rot (pv. campestris), bacterial blight of stock (pv. incanae) or bacterial leaf spot (pv. raphani). In this study, we extended the genomic coverage of the species by sequencing and annotating the genomes of strains from pathovar incanae (CFBP 1606R and CFBP 2527R), pathovar raphani (CFBP 5828R) and a pathovar formerly named barbareae (CFBP 5825R). While comparative analyses identified a large core ORFeome at the species level, the core type III effectome was limited to only three putative type III effectors (XopP, XopF1 and XopAL1). In Xanthomonas, these effector proteins are injected inside the plant cells by the type III secretion system and contribute collectively to virulence. A deep and strand-specific RNA sequencing strategy was adopted in order to experimentally refine genome annotation for strain CFBP 5828R. This approach also allowed the experimental definition of novel ORFs and non-coding RNA transcripts. Using a constitutively active allele of hrpG, a master regulator of the type III secretion system, a HrpG-dependent regulon of 141 genes co-regulated with the type III secretion system was identified. Importantly, all these genes but seven are positively regulated by HrpG and 56 of those encode components of the Hrp type III secretion system and putative effector proteins. This dataset is an important resource to mine for novel type III effector proteins as well as for bacterial genes which could contribute to pathogenicity of X. campestris

Wild Helianthus species: A reservoir of resistance genes for sustainable pyramidal resistance to broomrape in sunflower

Orobanche cumana Wall., sunflower broomrape, is one of the major pests for the sunflower crop. Breeding for resistant varieties in sunflower has been the most efficient method to control this parasitic weed. However, more virulent broomrape populations continuously emerge by overcoming genetic resistance. It is thus essential to identify new broomrape resistances acting at various stages of the interaction and combine them to improve resistance durability. In this study, 71 wild sunflowers and wild relatives accessions from 16 Helianthus species were screened in pots for their resistance to broomrape at the late emergence stage. From this initial screen, 18 accessions from 9 species showing resistance, were phenotyped at early stages of the interaction: the induction of broomrape seed germination by sunflower root exudates, the attachment to the host root and the development of tubercles in rhizotron assays. We showed that wild Helianthus accessions are an important source of resistance to the most virulent broomrape races, affecting various stages of the interaction: the inability to induce broomrape seed germination, the development of incompatible attachments or necrotic tubercles, and the arrest of emerged structure growth. Cytological studies of incompatible attachments showed that several cellular mechanisms were shared among resistant Helianthus species.This study was performed in the frame of a 3-year project (ResODiv), funded by “Promosol” (the association of French Sunflower and Rapeseed Breeders for promoting these crops).Peer reviewe

Interactions physiologiques et pharmacologiques entre les systèmes cannabinoïde et opioïde (approches in vivo et in vitro)

De part leurs similitudes d'action, notamment pour leurs propriétés antinociceptives et renforçantes, l'hypothèse d'une interaction entre les systèmes opioïde et cannabinoïde a été proposée dans la littérature. Afin d'avancer dans la compréhension de ces interactions, nous avons analysé, d'un point de vue physiologique et pharmacologique, l'effet de la modification du système cannabinoïde - délétion du gène codant le récepteur CB1 ou stimulation chronique par le THC - sur des réponses comportementales liées au système opioïde. De plus, nous avons pu reproduire, in vitro, l'effet du THC sur la libération de met-enképhaline, sur culture primaire de neurones de striatum dans le but d'identifier les voies de signalisation impliquées dans l'interaction entre les deux systèmes.Thanks to their similarities of action, in particular for their antinociceptive and reinforcing properties, the hypothesis of an interaction between the opioid and cannabinoid systems was proposed in the literature. In order to understand these interactions, we analyzed, from a physiological and pharmacological point of view, the effect of the modification of the cannabinoïd system - CB1 receptor gene deletion or chronic stimulation by THC - on behavioral properties related to opioid system. Moreover, we could reproduce, in vitro, the effect of the THC on the release of met-enkephalin observed in vivo, on primary culture of striatum neurons in order to identify the signal tranduction involved in the interaction between the two systems.PARIS-BIUP (751062107) / SudocSudocFranceF

Cytokinins in Symbiotic Nodulation: When, Where, What For?

Substantial progress has been made in the understanding of early stages of the symbiotic interaction between legume plants and rhizobium bacteria. Those include the specific recognition of symbiotic partners, the initiation of bacterial infection in root hair cells, and the inception of a specific organ in the root cortex, the nodule. Increasingly complex regulatory networks have been uncovered in which cytokinin (CK) phytohormones play essential roles in different aspects of early symbiotic stages. Intriguingly, these roles can be either positive or negative, cell autonomous or non-cell autonomous, and vary, depending on time, root tissues, and possibly legume species. Recent developments on CK symbiotic functions and interconnections with other signaling pathways during nodule initiation are the focus of this review

CB1 receptor knockout mice show similar behavioral modifications to wild-type mice when enkephalin catabolism is inhibited.

Behavioral and biochemical studies have suggested a functional link between the endogenous cannabinoid and opioid systems. Different hypotheses have been proposed to explain the interactions between opioid and cannabinoid systems such as a common pathway stimulating the dopaminergic system, a facilitation of signal-transduction- and/or a cannabinoid-induced enhancement of opioid peptide release. However, at this time, all the studies have been performed with exogenous agonists (delta-9-tetrahydrocannabinol or morphine), leading to a generally excessive stimulation of receptors normally stimulated by endogenous effectors (anandamide or opioid peptides) in various brain structures. To overcome this problem, we have measured various behavioral responses induced by the stimulation of the endogenous opioid system using the dual inhibitor of enkephalin-degrading enzymes, RB101, in CB1 receptor knockout mice. Thus, analgesia, locomotor activity, anxiety and antidepressant-like effects were measured after RB101 administration (80 and 120 mg/kg i.p. or 10 mg/kg, i.v.) in CB1 receptor knockout mice and their wild-type littermates. In all the experiments, inhibition of enkephalin catabolism produced similar modifications in behavior observed in CB1 knockout and wild-type mice. These results suggest limited physiological interaction between cannabinoid and opioid systems.Comparative StudyJournal Articleinfo:eu-repo/semantics/publishe

Progressive prediction of hospitalisation and patient disposition in the emergency department

International audienceHospitals face high occupation rates resulting in a longer boarding time and more complex bed management. This task could be facilitated by anticipating the unscheduled admissions. We study the capability of information from French electronic health records of an emergency department (ED) to predict patient disposition decisions. We compare the performances of five learning models in predicting the admission of a patient visiting an emergency department and in predicting the patient’s place of admission at two progressive time points throughout the ED care process: triage and initial assessment. Medical and administrative data were retrospectively collected on 53,608 visits to the Groupe Hospitalier Bretagne Sud, France, from July 2020 to June 2021. Our best model achieve a ROCAUC equal to 88% and F1-score equal to 75% for admission prediction. Regarding medical unit admission prediction, the global ROC-AUC equals to 87% and F1-score ranges from 38%to 77% for the four admission classes, i.e., intensive care unit (6% of the dataset), medicine units (45%), surgery units (13.2%), and observation unit (35.8%). A validation with a posterior dataset indicates constant results