title: Copper-induced modifications in early symbiotic signaling factors of Ensifer (Sinorhizobium)-Medicago interactions.
abstract: Cu is an essential micronutrient required during nitrogen fixation, but above threshold concentrations it becomes toxic. The present study was aimed at studying the effect of high Cu concentrations on the early plant-microbe interactions between Ensifer (Sinorhizobium) meliloti 1021, a symbiotic diazotrophic bacterium belonging to α-Proteobacteria, and its plant host Medicago truncatula. E. meliloti exhibited pleomorphism with elongated and branched growth at 100 µM Cu which brought about 50 % reduction in growth. Early symbiotic signaling factors like exopolysaccharides and lipopolysaccharides levels and biofilm formation were adversely affected at sublethal levels of Cu. Cu stress resulted in over-expression of proteins such as GroEL (60 kDa chaperonin) and WrbA (NAD(P)H dehydrogenase). E. meliloti was unable to show efficient attachment on the roots of M. truncatula at 3 µM Cu, which corresponds to 50 % growth inhibitory levels for the plant, indicating that plant root surface modifications may also contribute to adverse effect of Cu on early plant-microbe interactions during nodulation.
authors.affiliation: Department of Microbiology and Biotechnology Centre, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, 390002, India.
authors.forename: Murali
authors.initials: M
authors.lastname: Sharaff
authors.affiliation: Department of Microbiology and Biotechnology Centre, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, 390002, India. archanagayatri@yahoo.com.
authors.forename: G
authors.initials: G
authors.lastname: Archana
mesh_terms: D003300:Copper / Q000378:metabolism* / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000378:metabolism*; D046913:Medicago truncatula / Q000382:microbiology*; D009586:Nitrogen Fixation; D010084:Oxidation-Reduction / Q000187:drug effects; D018517:Plant Roots / Q000382:microbiology; D011135:Polysaccharides, Bacterial / Q000378:metabolism*; D015398:Signal Transduction; D016962:Sinorhizobium meliloti / Q000378:metabolism*; D013559:Symbiosis / Q000187:drug effects*
chemical_list: D008070:Lipopolysaccharides; D011135:Polysaccharides, Bacterial; D003300:Copper
keywords: Copper stress; Ensifer meliloti; Medicago truncatula; Symbiotic factors