Complete Genome Sequence of Bradyrhizobium sp. ORS285, a Photosynthetic Strain Able To Establish Nod Factor-Dependent or Nod Factor-Independent Symbiosis with Aeschynomene Legumes.

Here, we report the complete genome sequence of Bradyrhizobium sp. strain ORS285, which is able to nodulate Aeschynomene legumes using two distinct strategies that differ in the requirement of Nod factors. The genome sequence information of this strain will help understanding of the different mechanisms of interaction of rhizobia with legumes

The Type III Effectome of the Symbiotic Bradyrhizobium vignae Strain ORS3257.

Many Bradyrhizobium strains are able to establish a Nod factor-independent symbiosis with the leguminous plant Aeschynomene indica by the use of a type III secretion system (T3SS). Recently, an important advance in the understanding of the molecular factors supporting this symbiosis has been achieved by the in silico identification and functional characterization of 27 putative T3SS effectors (T3Es) of Bradyrhizobium vignae ORS3257. In the present study, we experimentally extend this catalog of T3Es by using a multi-omics approach. Transcriptome analysis under non-inducing and inducing conditions in the ORS3257 wild-type strain and the ttsI mutant revealed that the expression of 18 out of the 27 putative effectors previously identified, is under the control of TtsI, the global transcriptional regulator of T3SS and T3Es. Quantitative shotgun proteome analysis of culture supernatant in the wild type and T3SS mutant strains confirmed that 15 of the previously determined candidate T3Es are secreted by the T3SS. Moreover, the combined approaches identified nine additional putative T3Es and one of them was experimentally validated as a novel effector. Our study underscores the power of combined proteome and transcriptome analyses to complement in silico predictions and produce nearly complete effector catalogs. The establishment of the ORS3257 effectome will form the basis for a full appraisal of the symbiotic properties of this strain during its interaction with various host legumes via different processes

Role of bacterial envelope compounds during the free-living and symbiotic states of Bradyrhizobium strains

Le genre Bradyrhizobium est le genre de rhizobia qui nodule la plus grande diversité d’espèces de légumineuses. Certaines de ces bactéries ont la particularité d’établir une symbiose fonctionnelle avec des légumineuses du genre Aeschynomene en utilisant un processus Nod-indépendant. De plus, au sein des nodules d’Aeschynomene, les Bradyrhizobium subissent une différenciation terminale en bactéroïde qui s’accompagne de modifications métaboliques et morphologiques drastiques. A la différence de la majorité des autres rhizobia, des hopanoïdes sont retrouvés au sein des membranes de l’ensemble des souches de Bradyrhizobium, dont certains, de façon inédite, liés à l’une des très longue chaîne d’acide gras (VLCFA) présentent sur le lipide A du LPS de ces bactéries. De plus, le LPS des Bradyrhizobium photosynthétiques possède un antigène-O également inédit et non-immunogénique. Le but de cette thèse était de déterminer si les particularités de la membrane externe des Bradyrhizobium pouvaient être impliquées dans la physiologie de ces bactéries ainsi que dans l’initiation et le maintien de la symbiose avec Aeschynomene. Les résultats obtenus ont mis en évidence que les hopanoïdes et plus particulièrement ceux liés au lipide A, ainsi que les VLCFAs permettent de rigidifier la membrane externe des Bradyrhizobium. Ces propriétés leur confèrent ainsi une plus grande résistance face aux conditions de stress, dont celles présentes au sein des nodules d’Aeschynomene, ce qui permet aux Bradyrhizobium de maintenir une symbiose efficiente avec ces plantes. Ces travaux ont ainsi permis d’avancer dans la connaissance de la voie de biosynthèse et du rôle du LPS atypique et des hopanoïdes des Bradyrhizobium et pourrait conduire à la production d’inocula plus résistants.The Bradyrhizobium genus is the genus of rhizobia which nodulates the widest range of legume species. Some of these bacteria have the peculiarity of establishing a functional symbiosis with legumes of the genus Aeschynomene using a Nod-independent process. Moreover, within Aeschynomene nodules, the Bradyrhizobium strains undergo a terminal differentiation into bacteroids which is accompanied by drastic metabolic and morphological changes. Unlike the majority of other rhizobia, hopanoids are found in the membranes of all the Bradyrhizobium strains, some of which linked to one of the very long chain fatty acid (VLCFA) on the lipid A of these bacteria. In addition, LPS of photosynthetic Bradyrhizobium have an O-antigen that is also unique and non-immunogenic. The aim of this thesis was to determine whether the peculiarities of the external membrane of Bradyrhizobium strains could be implicated in the physiology of these bacteria as well as in the initiation and maintenance of the symbiosis with Aeschynomene. The obtained results showed that hopanoids and more particularly those linked to the lipid A, as well as the VLCFAs rigidify and stabilize the outer membrane of Bradyrhizobium strains. These properties give them greater resistance to stress conditions, including those present in Aeschynomene nodules, which allows the Bradyrhizobium to maintain an efficient symbiosis with these plants. This work allowed us to advance in the understanding of the biosynthesis and the role of the atypical LPS and the hopanoids produced by the Bradyrhizobium strains and could lead to the production of more resistant inocula

L’effet des thérapies thermiques sur la spasticité des patients post-AVC ::une revue de la littérature

Contexte : L’incidence de l’accident vasculaire cérébral (AVC) est en constante augmentation, notamment en raison du vieillissement de la population. Il engendre de nombreuses déficiences telles que la spasticité. Celle-ci peut être expliquée par différents mécanismes physiologiques encore mal connus et diminue l’autonomie ainsi que la qualité de vie des patients. La thérapie thermique n’a jusqu’à présent pas fait l’objet d’une revue de la littérature pour la prise en charge de la spasticité. Objectif : L’objectif de cette revue de la littérature consiste à évaluer l’effet des différentes thérapies thermiques sur la spasticité des patients post-AVC. Méthode : Une recherche dans les bases de données PubMed, CINAHL, PEDRO et Embase a permis de retenir cinq essais contrôlés randomisés (RCT), incluant au total 149 patients. Résultats : Deux études traitent de thermothérapie, deux de cryothérapie et une de thérapie thermique par contraste. La thermothérapie a démontré un effet significatif intergroupe directement et 30 minutes après l’intervention sur l’échelle d’Ashworth modifiée (MAS), auquel s’ajoute un effet cumulatif après 4 semaines de traitement. La cryothérapie démontre également un effet significatif intergroupe sur la MAS directement et 4 semaines après l’intervention. Le protocole de thérapie thermique par contraste n’a pas montré de résultats significatifs après 6 semaines d’intervention. Conclusion : Une recommandation faible selon le Grading of Recommendations, Assessment, Development and Evaluations (GRADE) concernant l’utilisation de thérapie thermique pour traiter la spasticité peut être émise. Des études de meilleure qualité sont nécessaires pour augmenter le niveau de recommandation ainsi que pour connaitre les effets de l’utilisation des différentes thérapies thermiques sur la fonction des patients.Background: The incidence of stroke is constantly increasing due to an aging population. Strokes cause numerous deficiencies, such as spasticity. Spasticity can be explained by different physiological mechanisms that are still not well known. Strokes can also reduce autonomy and quality of life. Thermal therapy has not yet been reviewed in the literature on the treatment of spasticity. Objective: This literature review aims to evaluate the effect of different thermal therapies on spasticity in post stroke patients. Method: A search of the PubMed, CINAHL, PEDRO, and Embase databases resulted in the selection of five randomized control trials (RCT), which included a total of 149 patients. Results: Two studies dealt with thermotherapy, two with cryotherapy, and one with thermal contrast therapy. Thermotherapy was assessed with the Modified Ashworth Scale (MAS) and had a significant intergroup effect immediately following and 30 minutes after the intervention, with a cumulative effect after four weeks of treatment. The effects of cryotherapy were also measured on the MAS, and cryotherapy had a significant effect immediately following and four weeks after the intervention. The thermal contrast therapy protocols did not show significant results after six weeks of intervention. Conclusion: A weak recommendation on the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) for the use of thermal therapy to treat spasticity can be made. More in-depth studies are needed to increase the level of the recommendation as well as to better understand the effects of the use of different thermal therapies on the patient’s function

The ecophysiological determinants of nitrophily in annual weed species

International audiencePlant nitrophily plays a key role in weed community assembly. To date, the determinants of the success of nitrophilic weeds and of the decline of oligotrophic weeds in intensive cropping systems are not fully understood. This study investigated which ecophysiological traits related to carbon and N nutrition explain plant nitrophily in field annual species. Twelve species (consisting of monocotyledonous and dicotyledonous species, as well as crops and weeds) covering the oligotrophic-nitrophilic continuum were grown in a glasshouse experiment at two contrasted conditions of soil-nitrogen supply. From measured plant growth variables, ecophysiological traits were calculated to account for plant nutritional strategies. Globally, whatever the soil-nitrogen supply, increased nitrophily was associated with a decreased allocation of carbon to root vs. shoot. At high soil-nitrogen only, increased nitrophily was also generally associated with an increased nitrogen uptake activity per unit of root biomass, pointing to a trade-off between oligotrophic species with a preferential carbon investment in root structure and nitrophilic species with a preferential carbon investment in root activity. Beyond these global trends explaining nitrophily, results also show that different strategies are possible for plant species to be considered as nitrophilic. This study provides evidence on why adjusting N fertilisation in quantity, in space (with nitrogen fertiliser placement on the row) or in time can be useful strategies to manage the most nitrophilic weeds, which are also the most problematic in intensive cropping systems

Genetic Diversity of Type 3 Secretion System in Burkholderia s.l. and Links With Plant Host Adaptation

International audienceBurkholderia sensu lato species are prominent for their diversity of hosts. The type 3 secretion system (T3SS) is a major mechanism impacting the interactions between bacteria and eukaryotic hosts. Besides the human pathogenic species Burkholderia pseudomallei and closely affiliated species, the T3SS has received little attention in this genus as in taxonomically and evolutionary close genera Paraburkholderia , Caballeronia , Trinickia , and Mycetohabitans . We proceeded to identify and characterize the diversity of T3SS types using the genomic data from a subset of 145 strains representative of the species diversity found in the Burkholderia s.l. group. Through an analysis of their phylogenetic distribution, we identified two new T3SS types with an atypical chromosomal organization and which we propose to name BCI ( Burkholderia cepacia complex Injectisome) and PSI ( Paraburkholderia Short Injectisome). BCI is the dominant T3SS type found in Burkholderia sensu stricto ( s.s. ) species and PSI is mostly restricted to the Paraburkholderia genus. By correlating their distribution with the ecology of their strains of origin, we propose a role in plant interaction for these T3SS types. Experimentally, we demonstrated that a BCI deficient B. vietnamiensis LMG10929 mutant was strongly affected in its rice colonization capacity

Symbiotic compatibility between rice cultivars and arbuscular mycorrhizal fungi genotypes affects rice growth and mycorrhiza-induced resistance

International audienceIntroduction: Arbuscular mycorrhizal fungi (AMF) belong to the Glomeromycota clade and can form root symbioses with 80% of Angiosperms, including crops species such as wheat, maize and rice. By increasing nutrient availability, uptake and soil anchoring of plants, AMF can improve plant’s growth and tolerance to abiotic stresses. AMF can also reduce symptoms and pathogen load on infected plants, both locally and systemically, through a phenomenon called mycorrhiza induced resistance (MIR). There is scarce information on rice mycorrhization, despite the high potential of this symbiosis in a context of sustainable water management in rice production systems.Methods: We studied the symbiotic compatibility (global mycorrhization & arbuscules intensity) and MIR phenotypes between six rice cultivars from two subspecies (indica: IR64 & Phka Rumduol; japonica: Nipponbare, Kitaake, Azucena & Zhonghua 11) and three AMF genotypes (Funneliformis mosseae FR140 (FM), Rhizophagus irregularis DAOM197198 (RIR) & R. intraradices FR121 (RIN)). The impact of mycorrhization on rice growth and defence response to Xanthomonas oryzae pv oryzae (Xoo) infection was recorded via both phenotypic indexes and rice marker gene expression studies.Results: All three AMF genotypes colonise the roots of all rice varieties, with clear differences in efficiency depending on the combination under study (from 27% to 84% for Phka Rumduol-RIN and Nipponbare-RIR combinations, respectively). Mycorrhization significantly (α=0.05) induced negative to beneficial effects on rice growth (impact on dry weight ranging from -21% to 227% on Azucena-FM and Kitaake-RIN combinations, respectively), and neutral to beneficial effects on the extent of Xoo symptoms on leaves (except for Azucena-RIN combination which showed a 68% increase of chlorosis). R. irregularis DAOM197198 was the most compatible AMF partner of rice, with high root colonisation intensity (84% of Nipponbare’s roots hyphal colonisation), beneficial effects on rice growth (dry weight +28% (IR64) to +178% (Kitaake)) and decrease of Xoo-induced symptoms (-6% (Nipponbare) to -27% (IR64)). Transcriptomic analyses by RT-qPCR on leaves of two rice cultivars contrasting in their association with AMF show two different patterns of response on several physiological marker genes

Investigating and modelling the morphological plasticity of weeds

International audienceWeed dynamics models are essential for assessing crop management techniques and cropping systems. They must include a competition model that accounts for the particular characteristics of crop:weed stands, i.e. heterogeneous canopies consisting of contrasting species presenting a high morphological plasticity and resulting from successive emergence flushes. In a previous study, we developed a model which predicts light incidence and absorption in each location of a 3D, individual-based canopy as a function of plant morphology, latitude and seasonal solar height. Plant morphology was simplified to a set of five plant traits (plant height, diameter, leaf vs. non-leaf biomass ratio, specific leaf area and median leaf distribution height). Here, the objective was to propose and parameterize a new modelling approach for predicting these simplified morphological variables as a function of two effects that are notoriously difficult to separate (1) plant biomass which results from past light absorption and determines a large part of the current competitive ability and (2) past and current shading to integrate changes in morphology resulting from plant response to shading. A field experiment was sown with oilseed rape in September. Gaps were artificially created in the canopy by removing seedlings after emergence; additional bare-soil plots were created. Target plants of one grass weed species (Alopecurus myosuroides), three broadleaved weed species (Galium aparine, Sinapis arvensis, Stellaria media), and one broadleaved crop species (oilseed rape) were transplanted into the various canopy scenarios. Target and canopy plants were sampled five times from October to April to determine the morphological variables. A shading index was calculated from incident light averaged over each target plant from predictions with the light availability submodel. A single equation was successfully fitted to each morphological variable, estimating parameters in shadeless conditions, a correlation parameter with plant biomass (for height and diameter only), and a parameter representing sensitivity to shading for each variable, species and date. Plant biomass decreased in the shade but plants were taller with more stem biomass (except in grass weeds) and larger/thinner leaves concentrated towards the top of the plant. The grass species was least plastic; among the broadleaved species, the crop species presented the least plasticity. The light availability and the plasticity submodels were combined to simulate the effect of crop sowing densities and patterns (row-sown vs. broadcast, varying interrow widths) on weed morphological variables. The latter was more altered in dense and in row-sown vs. broadcast canopies but its range of variation was smaller in the former, pointing to a more selective and less diverse environment. The consequences for weed adaptation to crops and for optimizing crop and cultivar choices were discussed. (C) 2013 Elsevier B.V. All rights reserved

Motility and aerotaxis in Sinorhizobium melilotiSinorhizobium\ meliloti, a soil bacterium

International audienceAerotaxis is the ability of motile cells to move towards oxygen. Bacteria tracking and in-situ oxygen concentration measurements are used to characterize aerotaxis in Sinorhizobium meliloti, a motile nitrogen-fixing bacterium naturally present in the soil. Aerotaxis takes place in a sealed glass capillary closed at one end with an oxygen-permeable plug. Our results suggest that the oxygen dependence of the aerotactic velocity, ∝ ∇c/c$^2$ , is stronger than the "logarithmic sensing" response (∝ ∇c/c) found in other chemoattractants

Aerotactic response of bacteria: experimental characterization at the bacteria scale and population scale

International audienc