title: Local signalling pathways regulate the Arabidopsis root developmental response to Mesorhizobium loti inoculation.
abstract: Numerous reports have shown that various rhizobia can interact with non-host plant species, improving mineral nutrition and promoting plant growth. To further investigate the effects of such non-host interactions on root development and functions, we inoculated Arabidopsis thaliana with the model nitrogen fixing rhizobacterium Mesorhizobium loti (strain MAFF303099). In vitro, we show that root colonization by M. loti remains epiphytic and that M. loti cells preferentially grow at sites where primary and secondary roots intersect. Besides resulting in an increase in shoot biomass production, colonization leads to transient inhibition of primary root growth, strong promotion of root hair elongation and increased apoplasmic acidification in periphery cells of a sizeable part of the root system. Using auxin mutants, axr1-3 and aux1-100, we show that a plant auxin pathway plays a major role in inhibiting root growth but not in promoting root hair elongation, indicating that root developmental responses involve several distinct pathways. Finally, using a split root device, we demonstrate that root colonization by M. loti, as well as by the bona fide plant growth promoting rhizobacteria Azospirillum brasilense and Pseudomonas, affect root development via local transduction pathways restricted to the colonised regions of the root system.
authors.affiliation: LSTM, Univ. Montpellier, IRD, CIRAD, Montpellier SupAgro, Montpellier, France.
authors.forename: A
authors.initials: A
authors.lastname: Poitout
authors.affiliation: BPMP, Univ. Montpellier, INRA, CNRS, Montpellier SupAgro, Montpellier, France.
authors.forename: A
authors.initials: A
authors.lastname: Martinière
authors.affiliation: LSTM, Univ. Montpellier, IRD, CIRAD, Montpellier SupAgro, Montpellier, France.
authors.forename: B
authors.initials: B
authors.lastname: Kucharczyk
authors.affiliation: LSTM, Univ. Montpellier, IRD, CIRAD, Montpellier SupAgro, Montpellier, France.
authors.forename: N
authors.initials: N
authors.lastname: Queruel
authors.affiliation: LSTM, Univ. Montpellier, IRD, CIRAD, Montpellier SupAgro, Montpellier, France.
authors.forename: J
authors.initials: J
authors.lastname: Silva-Andia
authors.affiliation: BPMP, Univ. Montpellier, INRA, CNRS, Montpellier SupAgro, Montpellier, France.
authors.forename: S
authors.initials: S
authors.lastname: Mashkoor
authors.affiliation: LSTM, Univ. Montpellier, IRD, CIRAD, Montpellier SupAgro, Montpellier, France.
authors.forename: L
authors.initials: L
authors.lastname: Gamet
authors.affiliation: LSTM, Univ. Montpellier, IRD, CIRAD, Montpellier SupAgro, Montpellier, France.
authors.forename: F
authors.initials: F
authors.lastname: Varoquaux
authors.affiliation: BPMP, Univ. Montpellier, INRA, CNRS, Montpellier SupAgro, Montpellier, France.
authors.forename: N
authors.initials: N
authors.lastname: Paris
authors.affiliation: BPMP, Univ. Montpellier, INRA, CNRS, Montpellier SupAgro, Montpellier, France.
authors.forename: H
authors.initials: H
authors.lastname: Sentenac
authors.affiliation: LSTM, Univ. Montpellier, IRD, CIRAD, Montpellier SupAgro, Montpellier, France.
authors.forename: B
authors.initials: B
authors.lastname: Touraine
authors.affiliation: LSTM, Univ. Montpellier, IRD, CIRAD, Montpellier SupAgro, Montpellier, France.
authors.forename: G
authors.initials: G
authors.lastname: Desbrosses
mesh_terms: D017360:Arabidopsis / Q000254:growth & development* / Q000378:metabolism / Q000382:microbiology*; D007210:Indoleacetic Acids; D059128:Mesorhizobium / Q000502:physiology*; D009586:Nitrogen Fixation; D018517:Plant Roots / Q000254:growth & development / Q000382:microbiology; D015398:Signal Transduction
chemical_list: D007210:Indoleacetic Acids
keywords: Apoplasmic pH; Arabidopsis; Mesorhizobium loti; PGPR; colonization pattern; root; split root.; symbiosis