Nod factor signalling
For the LR symbiosis, we have shown that the CSP is activated by secreted bacterial, lipochitooligosaccharidic (LCO) signals, called Nod factors. These signals are required for host recognition, infection and nodule organogenesis and are perceived by lysin-motif receptor like kinases (LysM-RLKs). A major project of the group concerns the regulation and function of the LysM-RLK family of Medicago truncatula, using a combination of molecular, biochemical, cell biology and genetic approaches. Analysis of the Nod factor binding capacity of receptor proteins and complexes is also being carried out. In addition, we are interested in how LysM-RLK activation is transduced to downstream components. This work involves studies of several of the signal transduction proteins and also protein interactors of the symbiotic receptors. In this way we aim to understand how host legume plants perceive specific Nod factors from rhizobial symbionts, and how they transduce the symbiotic signals to activate plant symbiotic responses.
Mycorrhizal symbiotic signalling
We collaborated with Guillaume Bécard (UMR CNRS/UPS 5546) and Vérena Poinsot (UMR CNRS/UPS 5623), to show that the AM fungus Rhizophagus irregularis produces sulphated and non-sulphated lipochitooligosaccharidic signals called Myc-LCOs. These signals activate the CSP, leading to induction of gene expression and root branching in M. truncatula and stimulate formation of AM in plant species of diverse families. Using Myc-LCOs synthesised by colleagues at CERMAV, Grenoble, we are now further dissecting the mechanisms by which M. truncatula perceives AM fungi and activates downstream responses. We are also investigating how Nod factor and Myc factor signalling is integrated.
Mycorrhization in non-legumes
A new project aims to use non-legume plants to specifically address questions related to the mycorrhizal symbiosis. These include addressing the role of Myc-LCOs and short COs in mycorrhization and using genetic variation in the model monocot, Brachypodium distachyon, to identify molecular mechanisms critical for mycorrhizal growth responses.
Developmental effects and agronomic use of symbiotic signals
Based on the observation that Nod and Myc factors stimulate the formation of lateral roots in M. truncatula, we are studying the signalling mechanisms underlying this response using cell biology and transcriptomic approaches together with M. truncatula mutants affected for Myc and/or Nod factor induction of root branching. The ability of Nod factors to act as growth regulators has led to the commercialisation by Novozymes (formerly EMD Crop BioScience), of rhizobial inoculants enriched in Nod factors for soybean, peanut, alfalfa and pea. Work is on-going to investigate whether purified Myc-LCOs have growth-promoting properties on a wide range of plants and whether seed treatments with these signals stimulate root development and/or mycorrhization. We are also investigating the perception mechanisms of LCOs in non-legumes.
Medicago truncatula genomics
Our work on the dissection of symbiotic signal perception/transduction has required use of the extensive genetic and genomic tools which have been developed by the International research community for M. truncatula. We have contributed to the International Genome Sequencing Project of M. truncatula through the sequencing of chromosome 5, in collaboration with the Génoscope (Evry) (http://medicago.org/genome).
Our collaborators for Nod factor signalling are the groups of David Barker and Pascal Gamas (LIPM), René Geurts and Ton Bisseling (Wageningen Univeristy, The Netherlands), Theodorus Gadella (Amsterdam University, The Netherlands), Jean-Michel Ané (Wisconsin University), L. Gentzbittel (SP2, ENSAT), and Thomas Ott (University of Munich).
Our collaborators for mycorrhizal symbiotic signalling are the groups of Guillaume Bécard (UMR CNRS/UPS 5546) and Vérena Poinsot (UMR CNRS/UPS 5623).
Our collaborators for LCO synthesis are the groups of Jean-Marie Beau (Orsay, Paris) and Sébastien Fort (CERMAV, Grenoble).
Our collaborators for genomic studies are J. Gouzy (LIPM), Francis Quétier and collaborators (Génoscope-CEA Paris), and The International consortium for the genome sequencing project for Medicago truncatula : Nevin Young (University of Minnesota, USA), Chris Town (JCVI, USA), Bruce Roe (University of Oklahoma, USA), René Geurts (Wageningen University, The Netherlands), Giles Oldroyd and Jane Rogers (JIC, UK).
ANR Jeune Chercheur (2010-2014) « LCOin NONLEGUMES » ANR-2010 JCJC 1602 01). Perception of lipo-chitooligosaccharides and roles of their putative receptors in non legumes. B. Lefevbre, coordinator 205kE
ANR Blanc (2011-2013) (“Nod on-Nod-off ANR-10-BLAN-1722 01). Novel genetic approaches to dissect host range control in the rhizobium-legume symbiosis. F. Debellé, coordinator 254 kE
Research collaboration for PhD cofunding CNRS/Novozymes (2010-2013). The influence of symbiotic signals on root system development in Medicago truncatula. S. Bensmihen, C. Gough, PhD supervisors.
ANR Blanc (2009-2012) (“SympaSignal” ANR-08-BLAN-0208-03). Symbiotic and Pathogenic Signals in legumes. JJ. Bono, coordinator, 540 kE
ANR Blanc (2009-2012) (“MycSignalling” ANR-09-BLAN-0241) Molecular dissection of mycorrhizal signalling in Medicago truncatula during establishment of the arbuscular mycorrhizal symbiosis. C. Gough, coordinator, 515 K€
ANR Blanc (2008-2011) (“SYMbiMICS” ANR-08-BLAN-XXX). Molecular dissection of the Rhizobium-legume interaction: a combined laser micro-dissection and deep EST sequencing approach. P. Gamas, coordinator, 566 kE