Accepted Article This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/nph.15891 This article is protected by copyright. All rights reserved. Article Type: Regular Article The Medicago truncatula LysM receptor-like kinase LYK9 plays a dual role in immunity and the arbuscular mycorrhizal symbiosis Chrystel Gibelin-Viala 1 , Emilie Amblard 2 , Virginie Puech-Pages 2 , Maxime Bonhomme 2 , Magali Garcia 1 , Adeline Bascaules-Bedin 2 , Judith Fliegmann 1 , Jiangqi Wen 3 , Kirankumar S. Mysore 3 , Christine le Signor 4 , Christophe Jacquet 2 and Clare Gough 1* 1 LIPM, Université de Toulouse, INRA, CNRS, 31326 Castanet-Tolosan, France. 2 Laboratoire de Recherche en Sciences Végétales, Université de Toulouse, CNRS, UPS, 31326 Castanet-Tolosan, France. 3 Noble Research Institute, LLC., 2510 Sam Noble Parkway, Ardmore, Oklahoma 73401, USA. 4 INRA, UMR1347 Agroécologie, Dijon, France. * Author for correspondence (clare.gough@inra.fr) tel. +33 561285416, ORCID:0000-0001- 5844-7217 ORCID ID for CJ : 0000-0002-7377-5638 ; Received: 12 February 2019 Accepted: 24 April 2019 Summary  Plant specific lysin-motif receptor-like kinases (LysM-RLKs) are implicated in the perception of N-acetyl glucosamine-containing compounds, some of which are important signal molecules in plant-microbe interactions. Among these, both lipo-chitooligosaccharides (LCOs) and chitooligosaccharides (COs) are proposed as arbuscular mycorrhizal (AM)