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Journal of Bacteriology, July 2004, p. 4774-4780, Vol. 186, No. 14
0021-9193/04/$08.00+0 DOI: 10.1128/JB.186.14.4774-4780.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
Hajime Kobayashi,2 William J. Deakin,2 Corinne Marie,2,
Hari B. Krishnan,3 William J. Broughton,2* and Xavier Perret2
Department of Microbiology, Swedish University of Agricultural Sciences, SLU, Uppsala S-75007, Sweden,1 Laboratoire de Biologie Moléculaire des Plantes Supérieures (LBMPS), University of Geneva, Sciences III, CH-1211 Geneva 4, Switzerland,2 Plant Genetics Research Unit, USDA Agricultural Research Service, and Department of Agronomy, University of Missouri, Columbia, Missouri 652113
Received 12 February 2004/ Accepted 13 April 2004
The type three secretion system (TTSS) encoded by pNGR234a, the symbiotic plasmid of Rhizobium sp. strain NGR234, is responsible for the flavonoid- and NodD1-dependent secretion of nodulation outer proteins (Nops). Abolition of secretion of all or specific Nops significantly alters the nodulation ability of NGR234 on many of its hosts. In the closely related strain Rhizobium fredii USDA257, inactivation of the TTSS modifies the host range of the mutant so that it includes the improved Glycine max variety McCall. To assess the impact of individual TTSS-secreted proteins on symbioses with legumes, various attempts were made to identify nop genes. Amino-terminal sequencing of peptides purified from gels was used to characterize NopA, NopL, and NopX, but it failed to identify SR3, a TTSS-dependent product of USDA257. By using phage display and antibodies that recognize SR3, the corresponding protein of NGR234 was identified as NopP. NopP, like NopL, is an effector secreted by the TTSS of NGR234, and depending on the legume host, it may have a deleterious or beneficial effect on nodulation or it may have little effect.
Present address: Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520.
Present address: Unité de Génétique Microbienne, Domaine de Vilvert, INRA, 78352 Jouy en Josas Cedex, France.
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