The pea branching RMS2 gene encodes the PsAFB4/5 auxin receptor and is involved in an auxin-strigolactone regulation loop

Strigolactones (SLs) are well known for their role in repressing shoot branching. In pea, increased transcript levels of SL biosynthesis genes are observed in stems of highly branched SL deficient (ramosus1 (rms1) and rms5) and SL response (rms3 and rms4) mutants indicative of negative feedback control. In contrast, the highly branched rms2 mutant has reduced transcript levels of SL biosynthesis genes. Grafting studies and hormone quantification led to a model where RMS2 mediates a shoot-to-root feedback signal that regulates both SL biosynthesis gene transcript levels and xylem sap levels of cytokinin exported from roots. Here we cloned RMS2 using synteny with Medicago truncatula and demonstrated that it encodes a putative auxin receptor of the AFB4/5 clade. Phenotypes similar to rms2 were found in Arabidopsis afb4/5 mutants, including increased shoot branching, low expression of SL biosynthesis genes and high auxin levels in stems. Moreover, afb4/5 and rms2 display a specific resistance to the herbicide picloram. Yeast-two-hybrid experiments supported the hypothesis that the RMS2 protein functions as an auxin receptor. SL root feeding using hydroponics repressed auxin levels in stems and down-regulated transcript levels of auxin biosynthesis genes within one hour. This auxin down-regulation was also observed in plants treated with the polar auxin transport inhibitor NPA. Together these data suggest a homeostatic feedback loop in which auxin up-regulates SL synthesis in an RMS2-dependent manner and SL down-regulates auxin synthesis in an RMS3 and RMS4- dependent manner

Etude de genes de Rhizobium meliloti controlant la nodulation specifique de Medicago sativa

CNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Etude de genes de Rhizobium meliloti controlant la nodulation specifique de Medicago sativa

CNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Radiation damage in uranium dioxide: coupled effect between electronic and nuclear energy losses

International audienc

Epidémie du Covid 19 en Belgique francophone : regard sur les patients dialysés en techniques ambulatoires

In the French-speaking part of Belgium, between march and end of may 2020, 284 patients have suffered a Covid-19 infection, 7,9% of the prevalent dialysis population. Some of them have been  diagnosed through rt-PCT as they were symptomatic, others, asymptomatic,  being diagnosed by swab viral culture. Fifty two patients died (18% of the positive patients). The vast majority of them were patients on hemodialysis, only ten cases have been observed in patients on home dialysis techniques. Primary renal disease were diabetes or renal hypertensive disease in more than 50% of the patients and the most important comorbidities were cardiac ischemic or congestive disease, autonomy problems, cancer and smoking habits.En Belgique francophone, pendant la période mars à fin  mai 2020, 284 patients en dialyse ont contracté le Covid-19, soit 7,9% de la population prévalente, qu’ils aient été diagnostiques par rt-PCT parce que symptomatiques ou dépistés par culture virale systématique alors qu’asymptomatiques. Cinquante-deux décès ont été observés soit 18% de la population atteinte. La toute grand majorité de ces patients (274) étaient traités par hémodialyse en centre, seuls 10 patients étaient en traitement à domicile. Leurs maladies rénales primitives étaient à plus de 50% des diabète et pathologies vasculaires hypertensives et leurs comorbidités essentielles, les pathologies cardiovasculaires ischémiques et congestives, les problèmes d’autonomie, les néoplasies et le tabagisme

Genetic bases of variation in plant architecture and rhizobial partner choice along the pea domestication gradient

International audienceLegumes play an increasingly important role in sustainable agriculture due to their ability to form a beneficial symbiotic interaction with nitrogen-fixing Rhizobium bacteria. Legumes are also a valuable source of protein for both feed and food, but are not grown as extensively as expected in Europe due to their high yield variability. Many genomic approaches are being developed to improve stress tolerance traits. However, to date, little attention has been paid to improving the interaction between symbiotic partners. The establishment of the symbiotic interaction is a complex evolutionary process in which the interests of both partners are not always aligned. No evidence was found in pea for co-selection of competitiveness for nodulation and nitrogen (N) fixation efficiency (Bourion et al., 2018). Furthermore, several data indicated that N fixation and plant growth could be suboptimal in fields where pea is exposed to populations of heterogenous rhizobial strains with contrasting effects on nodule, root and shoot development (Laguerre et al., 2007). We performed Genome-Wide Association Studies to decipher the genetic determinants and relationships between the complex trait of pea choice between rhizobial strains in mixture and plant architecture. A large panel of 340 pea accessions including very diverse cultivars, wild accessions and landraces, all inoculated with the same mixture of 28 diverse rhizobial strains, was grown in two successive experiments, on a high throughput non-destructive phenotyping platform. The proportion of each strain in the nodules of each pea at harvest was determined by DNA metabarcoding, and 20 variables of nodulated root architecture or plant growth traits were estimated by image analysis or measured. The results highlighted differential variation and largely uncoupled genetic bases between rhizobial partner choice and architectural or growth traits, along the pea domestication gradient