Lipo‐chitooligosaccharide signalling blocks a rapid pathogen‐induced ROS burst without impeding immunity. Issue 2 (26th November 2018)

• Record Type: Journal Article
• Authors: Rey, Thomas; André, Olivier; Nars, Amaury; Dumas, Bernard; Gough, Clare; Bottin, Arnaud; Jacquet, Christophe
• Is Part Of: New phytologist. Volume 221:Issue 2(2019)
• Page Start: 743
• Page End: 749
• Publication Date: 2018-11-26
• Subjects: Aphanomyces euteiches -- immunity -- lipo‐chitooligosaccharide (LOS) -- Medicago truncatula -- oomycete -- reactive oxygen species (ROS) -- symbiosis; Botany -- Periodicals; 580
• DOI: 10.1111/nph.15574
• Languages: English
• ISSNs: 0028-646X

Abstract

Summary: Molecular signals released by microbes at the surface of plant roots and leaves largely determine host responses, notably by triggering either immunity or symbiosis. How these signalling pathways cross‐talk upon coincident perception of pathogens and symbionts is poorly described in plants forming symbiosis. Nitrogen fixing symbiotic Rhizobia spp. and arbuscular mycorrhizal fungi produce lipo‐chitooligosaccharides (LCOs) to initiate host symbiotic programmes. In Medicago truncatula roots, the perception of LCOs leads to reduced efflux of reactive oxygen species (ROS). By contrast, pathogen perception generally triggers a strong ROS burst and activates defence gene expression. Here we show that incubation of M. truncatula seedlings with culture filtrate (CF) of the legume pathogen Aphanomyces euteiches alone or simultaneously with Sinorhizobium meliloti LCOs, resulted in a strong ROS release. However, this response was completely inhibited if CF was added after pre‐incubation of seedlings with LCOs. By contrast, expression of immunity‐associated genes in response to CF and disease resistance to A. euteiches remained unaffected by LCO treatment of M. truncatula roots. Our findings suggest that symbiotic plants evolved ROS inhibition response to LCOs to facilitate early steps of symbiosis whilst maintaining a parallel defence mechanisms toward pathogens.