Symbiotic implications of type III protein secretion machinery in Rhizobium

Authors

  • Virginie Viprey,

    1. Laboratoire de Biologie Moléculaire des Plantes Supérieures (LBMPS), Université de Genève, 1 ch. de l'Impératrice, 1292 Chambésy, Geneva, Switzerland.,
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  • Aixa Del Greco,

    1. Laboratoire de Biologie Moléculaire des Plantes Supérieures (LBMPS), Université de Genève, 1 ch. de l'Impératrice, 1292 Chambésy, Geneva, Switzerland.,
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  • Wladyslaw Golinowski,

    1. Department of Botany, Institute of Plant Biology, Warsaw Agricultural University, Rakowiecka 26/30, 02-528 Warsaw, Poland.
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  • William J. Broughton,

    1. Laboratoire de Biologie Moléculaire des Plantes Supérieures (LBMPS), Université de Genève, 1 ch. de l'Impératrice, 1292 Chambésy, Geneva, Switzerland.,
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  • Xavier Perret

    1. Laboratoire de Biologie Moléculaire des Plantes Supérieures (LBMPS), Université de Genève, 1 ch. de l'Impératrice, 1292 Chambésy, Geneva, Switzerland.,
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William J. Broughton E-mail broughtw@sc2a.unige.ch; Tel. (22) 906 1740; Fax (22) 906 1741.

Abstract

The symbiotic plasmid of Rhizobium sp. NGR234 carries a cluster of genes that encodes components of a bacterial type III secretion system (TTSS). In both animal and plant pathogens, the TTSS is an essential component of pathogenicity. Here, we show that secretion of at least two proteins (y4xL and NolX) is controlled by the TTSS of NGR234 and occurs after the induction with flavonoids. Polar mutations in two TTSS genes, rhcN and the nod-box controlled regulator of transcription y4xI, block the secretion of both proteins and strongly affect the ability of NGR234 to nodulate a variety of tropical legumes including Pachyrhizus tuberosus and Tephrosia vogelii.

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