Wild Wheat Rhizosphere-Associated Plant Growth-Promoting Bacteria Exudates: Effect on Root Development in Modern Wheat and Composition

Diazotrophic bacteria isolated from the rhizosphere of a wild wheat ancestor, grown from its refuge area in the Fertile Crescent, were found to be efficient Plant Growth-Promoting Rhizobacteria (PGPR), upon interaction with an elite wheat cultivar. In nitrogen-starved plants, they increased the amount of nitrogen in the seed crop (per plant) by about twofold. A bacterial growth medium was developed to investigate the effects of bacterial exudates on root development in the elite cultivar, and to analyze the exo-metabolomes and exo-proteomes. Altered root development was observed, with distinct responses depending on the strain, for instance, with respect to root hair development. A first conclusion from these results is that the ability of wheat to establish effective beneficial interactions with PGPRs does not appear to have undergone systematic deep reprogramming during domestication. Exo-metabolome analysis revealed a complex set of secondary metabolites, including nutrient ion chelators, cyclopeptides that could act as phytohormone mimetics, and quorum sensing molecules having inter-kingdom signaling properties. The exo-proteome-comprised strain-specific enzymes, and structural proteins belonging to outer-membrane vesicles, are likely to sequester metabolites in their lumen. Thus, the methodological processes we have developed to collect and analyze bacterial exudates have revealed that PGPRs constitutively exude a highly complex set of metabolites; this is likely to allow numerous mechanisms to simultaneously contribute to plant growth promotion, and thereby to also broaden the spectra of plant genotypes (species and accessions/cultivars) with which beneficial interactions can occur

TOWARDS A DIAGNOSIS OF NON-CELIAC GLUTEN SENSITIVITY: the contribution of metabolomics for monitoring metabolites produced by in vitro digestates of bread

International audienceBody fluid metabolomics is a large-scale approach allowing exploring the mechanisms that might underlie specific diseases or sensitivity to processed foods, and identifying associated biomarkers for diagnostics or stratification. Over the past decade, the non-celiac gluten sensitivity (NCGS) is more and more self-diagnosed, which makes the gluten-free diet more frequent, without objective clinical criteria. In fact, because of a lack of clinical indicators, NCGS is poorly understood and challenging to diagnose in contrast to celiac disease. Therefore, finding biomarkers associated with this phenotype is critical for an accurate diagnosis and innovative patient management.To understand the relationship between bread digestion mechanisms and the occurrence of NCGS, a recent approach with in vitro investigation was applied to study the overall digestive process of different breads, combining tools from the oral step thanks to the AM2 masticator apparatus, until the end of digestion thanks to a dynamic digester (DIDGI©) mimicking the physiology of the adult gastrointestinal tract "GIT". One objective in this study was to monitor metabolites produced by in vitro digestates using an untargeted metabolomics approach.In this study, we will outline the methodological strategy taken from preparation of the stomach and intestinal digestates, to acquisition, processing, and annotation of the LC-HRMS data.Interestingly, the first results show fluctuations in certain metabolites identified according to the type of bread digested. This reveals the impact of type of bread on the digestibility and allowed us to emphasize the contribution of metabolomic approach for monitoring the metabolites produced by in vitro digestates

Search for potassium transport systems involved in arbuscular mycorrhiza-rice symbiotic interactions

International audienceArbuscular mycorrhizal fungi (AMF) develop interdependent connections with roots of about90% of plant species. These interactions increase availability as well as translocation ofnutrients (especially N and P), and thereby improve plant nutrition and growth. Moreover,resistance to a variety of stresses, among which salt stress, has been shown to be improved byAMF-plant interactions, for example in rice. Intense research to explain the molecularmechanisms of AMF-plant beneficial interactions led to the identification of phosphate andammonium transporters involved in nutrient exchanges from AMF to the plant, in several plantspecies. In spite of the importance of potassium (K+) for plant physiology, the contribution ofAMF symbiosis to plant K+ nutrition has been little documented. Over-expression of plant K+transporters has been described in Lotus japonicus and tomato in condition of AMF symbiosis.Furthermore, K+ transport systems in the AMF Rhizophagus irregularis have been identified insilico. Here, K+ nutrition in rice colonized by R. irregularis has been analyzed at molecular andphysiological levels. Surprisingly, major K+ transport systems in rice were down-regulated uponAMF interactions, suggesting strong increase in K+ availability for uptake by root cells insymbiotic conditions. Role of K+ in the relationships between rice and R. irregularis will also bediscusse

Recherche de systèmes de transport de potassium impliqués dans le transfert de K+ de la mycorhize arbusculaire au riz lors d'interactions symbiotiques

National audienceLes champignons mycorhiziens à arbuscules (CMA) développent des connexions interdépendantes avec les racines d'environ 90% des espèces végétales. Ces interactions augmentent la disponibilité ainsi que la translocation des nutriments (en particulier N et P), et améliorent ainsi la nutrition et la croissance des plantes. De plus, la résistance à une variété de stress, parmi lesquels le stress salin, s'est avérée améliorée par les interactions CMA-plante, par exemple chez le riz. Des recherches intenses pour expliquer les mécanismes moléculaires des interactions bénéfiques CMA-plante ont conduit à l'identification de transporteurs de phosphate et d'ammonium impliqués dans les échanges de nutriments du CMA vers la plante, chez plusieurs espèces végétales. Malgré l'importance du potassium (K+) pour la physiologie des plantes, la contribution de la symbiose mycorhizienne à arbuscule à la nutrition en K+ des plantes a été peu documentée. La surexpression des transporteurs de K+ végétaux a été décrite chez Lotus japonicus et la tomate en condition de symbiose mycorhizienne à arbuscule. Ici, la nutrition en K+ du riz colonisé par Rhizophagus irregulis a été analysée aux niveaux moléculaire et physiologique. Étonnamment, les principaux systèmes de transport de K+ dans le riz étaient régulés à la baisse lors des interactions AMF, suggérant une forte augmentation de la disponibilité de K+ pour l'absorption par les cellules racinaires dans des conditions symbiotiques. De plus, des systèmes de transport de K+ dans le CMA R. irregularis ont été identifiés in silico. La fonction de l’un d’entre eux a été analysée. Le rôle de K+ dans les relations entre le riz et R. irregularis sera également discuté

Arbuscular mycorrhizal fungus Rhizophagus irregularis expresses an outwardly Shaker-like channel involved in potassium nutrition of rice ( Oryza sativa L.)

Abstract Potassium (K + ) plays crucial roles in many physiological, molecular and cellular processes in plants. Direct uptake of this nutrient by root cells has been extensively investigated, however, indirect uptake of K + mediated by the interactions of the roots with fungi in the frame of a mutualistic symbiosis, also called mycorrhizal nutrient uptake pathway, is much less known. We identified an ion channel in the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis . This channel exhibits the canonical features of Shaker-like channel shared in other living kingdoms and is named RiSKC3. Transcriptionally expressed in hyphae and in arbuscules of colonized rice roots, RiSKC3 has been shown to be located in the plasma membrane. Voltage-clamp functional characterization in Xenopus oocytes revealed that RiSKC3 is endowed with outwardly-rectifying voltage-gated activity with a high selectivity for K + over sodium ions. RiSKC3 may have a role in the AM K + pathway for rice nutrition in normal and salt stress conditions. The current working model proposes that K + ions taken up by peripheral hyphae of R. irregularis are secreted towards the host root into periarbuscular space by RiSKC3. Significance Statement Mutualistic symbiosis with arbuscular mycorrhizal (AM) fungi are beneficial for about 80% of land plants thanks to an exchange of nutrients. The AM pathway responsible for potassium (K + ) nutrition of the plant is not known. Here we uncovered a key step of this phenomenon, by functionally characterizing the first transport system in the AM fungus Rhizophagus irregularis , and we univocally demonstrated that RiSKC3 is an K + outwardly-rectifying voltage-gated Shaker-like channel

Wild Wheat Rhizosphere-Associated Plant Growth-Promoting Bacteria Exudates: Effect on Root Development in Modern Wheat and Composition

Diazotrophic bacteria isolated from the rhizosphere of a wild wheat ancestor, grown from its refuge area in the Fertile Crescent, were found to be efficient Plant Growth-Promoting Rhizobacteria (PGPR), upon interaction with an elite wheat cultivar. In nitrogen-starved plants, they increased the amount of nitrogen in the seed crop (per plant) by about twofold. A bacterial growth medium was developed to investigate the effects of bacterial exudates on root development in the elite cultivar, and to analyze the exo-metabolomes and exo-proteomes. Altered root development was observed, with distinct responses depending on the strain, for instance, with respect to root hair development. A first conclusion from these results is that the ability of wheat to establish effective beneficial interactions with PGPRs does not appear to have undergone systematic deep reprogramming during domestication. Exo-metabolome analysis revealed a complex set of secondary metabolites, including nutrient ion chelators, cyclopeptides that could act as phytohormone mimetics, and quorum sensing molecules having inter-kingdom signaling properties. The exo-proteome-comprised strain-specific enzymes, and structural proteins belonging to outer-membrane vesicles, are likely to sequester metabolites in their lumen. Thus, the methodological processes we have developed to collect and analyze bacterial exudates have revealed that PGPRs constitutively exude a highly complex set of metabolites; this is likely to allow numerous mechanisms to simultaneously contribute to plant growth promotion, and thereby to also broaden the spectra of plant genotypes (species and accessions/cultivars) with which beneficial interactions can occur