title: A vapBC-type toxin-antitoxin module of Sinorhizobium meliloti influences symbiotic efficiency and nodule senescence of Medicago sativa.
abstract: The symbiotic nitrogen-fixing soil bacterium Sinorhizobium meliloti carries a large number of toxin-antitoxin (TA) modules both on the chromosome and megaplasmids. One of them, the vapBC-5 module that belongs to the type II systems was characterized here. It encodes an active toxin vapC-5, and was shown to be controlled negatively by the complex of its own proteins. Different mutants of the vapBC-5 genes exhibited diverse effects on symbiotic efficiency during interaction with the host plant Medicago sativa. The absence of the entire vapBC-5 region had no influence on nodule formation and nitrogen fixation properties. The strain carrying an insertion in the antitoxin gene showed a reduced nitrogen fixation capacity resulting in a lower plant yield. In contrast, when the toxin gene was mutated, the strain developed more efficient symbiosis with the host plant. The nitrogen fixing root nodules had a delayed senescent phenotype and contained elevated level of plant-derived molecules characteristic of later steps of nodule development. The longer bacteroid viability and abundance of active nitrogen fixing zone resulted in increased production of plant material. These data indicate that modification of the toxin/antitoxin production may influence bacteroid metabolism and may have an impact on the adaptation to changing environmental conditions.
authors.affiliation: Institut Sophia Agrobiotech (ISA), INRA UMR 1355, CNRS UMR 7254, Université de Nice Sophia Antipolis, 400 Route des Chappes - BP167, Sophia Antipolis Cedex, F-06903, France.
authors.forename: Justine
authors.initials: J
authors.lastname: Lipuma
authors.forename: Gyöngyi
authors.initials: G
authors.lastname: Cinege
authors.forename: Monica
authors.initials: M
authors.lastname: Bodogai
authors.forename: Boglárka
authors.initials: B
authors.lastname: Oláh
authors.forename: Aurélie
authors.initials: A
authors.lastname: Kiers
authors.forename: Gabriella
authors.initials: G
authors.lastname: Endre
authors.forename: Laurence
authors.initials: L
authors.lastname: Dupont
authors.forename: Ilona
authors.initials: I
authors.lastname: Dusha
mesh_terms: D000992:Antitoxins / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001427:Bacterial Toxins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D000455:Medicago sativa / Q000254:growth & development / Q000382:microbiology* / Q000502:physiology; D009154:Mutation; D009586:Nitrogen Fixation / Q000235:genetics; D009876:Operon; D010641:Phenotype; D053204:Root Nodules, Plant / Q000254:growth & development / Q000382:microbiology; D016962:Sinorhizobium meliloti / Q000235:genetics* / Q000502:physiology*; D013559:Symbiosis
chemical_list: D000992:Antitoxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins