Analysis of the role of the two flagella of Bradyrhizobium japonicum in competition for nodulation of soybean

Authors

  • Maria Julia Althabegoiti,

    1. Departamento de Ciencias Biológicas, Instituto de Biotecnología y Biología Molecular (IBBM), Facultad de Ciencias Exactas, Universidad Nacional de La Plata y CCT La Plata-CONICET, La Plata, Argentina
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  • Julieta M. Covelli,

    1. Departamento de Ciencias Biológicas, Instituto de Biotecnología y Biología Molecular (IBBM), Facultad de Ciencias Exactas, Universidad Nacional de La Plata y CCT La Plata-CONICET, La Plata, Argentina
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  • Julieta Pérez-Giménez,

    1. Departamento de Ciencias Biológicas, Instituto de Biotecnología y Biología Molecular (IBBM), Facultad de Ciencias Exactas, Universidad Nacional de La Plata y CCT La Plata-CONICET, La Plata, Argentina
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  • Juan Ignacio Quelas,

    1. Departamento de Ciencias Biológicas, Instituto de Biotecnología y Biología Molecular (IBBM), Facultad de Ciencias Exactas, Universidad Nacional de La Plata y CCT La Plata-CONICET, La Plata, Argentina
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  • Elías J. Mongiardini,

    1. Departamento de Ciencias Biológicas, Instituto de Biotecnología y Biología Molecular (IBBM), Facultad de Ciencias Exactas, Universidad Nacional de La Plata y CCT La Plata-CONICET, La Plata, Argentina
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  • Maria Florencia López,

    1. Departamento de Ciencias Biológicas, Instituto de Biotecnología y Biología Molecular (IBBM), Facultad de Ciencias Exactas, Universidad Nacional de La Plata y CCT La Plata-CONICET, La Plata, Argentina
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  • Silvina L. López-García,

    1. Departamento de Ciencias Biológicas, Instituto de Biotecnología y Biología Molecular (IBBM), Facultad de Ciencias Exactas, Universidad Nacional de La Plata y CCT La Plata-CONICET, La Plata, Argentina
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  • Aníbal R. Lodeiro

    1. Departamento de Ciencias Biológicas, Instituto de Biotecnología y Biología Molecular (IBBM), Facultad de Ciencias Exactas, Universidad Nacional de La Plata y CCT La Plata-CONICET, La Plata, Argentina
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  • Present address: Elías J. Mongiardini, Laboratori Genètica Molecular Bacteriana, Institut de Biotecnologia i Biomedicina, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain.

  • Editor: Juan Imperial

Correspondence: Aníbal R. Lodeiro, Departamento de Ciencias Biológicas, Instituto de Biotecnología y Biología Molecular (IBBM), Facultad de Ciencias Exactas, Universidad Nacional de La Plata y CCT La Plata-CONICET, Calles 47 y 115 (1900) La Plata, Argentina. Tel.: +54 221 425 0497; fax: +54 221 422 6947; e-mail: lodeiro@biol.unlp.edu.ar

Abstract

Bradyrhizobium japonicum has two types of flagella. One has thin filaments consisting of the 33-kDa flagellins FliCI and FliCII (FliCI-II) and the other has thick filaments consisting of the 65-kDa flagellins FliC1, FliC2, FliC3, and FliC4 (FliC1-4). To investigate the roles of each flagellum in competition for nodulation, we obtained mutants deleted in fliCI-II and/or fliC1-4 in the genomic backgrounds of two derivatives from the reference strain USDA 110: the streptomycin-resistant derivative LP 3004 and its more motile derivative LP 3008. All mutations diminished swimming motility. When each mutant was co-inoculated with the parental strain on soybean plants cultivated in vermiculite either at field capacity or flooded, their competitiveness differed according to the flagellin altered. ΔfliCI-II mutants were more competitive, occupying 64–80% of the nodules, while ΔfliC1-4 mutants occupied 45–49% of the nodules. Occupation by the nonmotile double mutant decreased from 55% to 11% as the water content of the vermiculite increased from 85% to 95% field capacity to flooding. These results indicate that the influence of motility on competitiveness depended on the water status of the rooting substrate.

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