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Open Access Research article

The type III secretion system is necessary for the development of a pathogenic and endophytic interaction between Herbaspirillum rubrisubalbicans and Poaceae

Maria Augusta Schmidt1, Eduardo Balsanelli1, Hellison Faoro1, Leonardo M Cruz1, Roseli Wassem2, Valter A de Baura1, Vinícius Weiss1, Marshall G Yates1, Humberto M F Madeira3, Lilian Pereira-Ferrari3, Maria H P Fungaro4, Francine M de Paula4, Luiz F P Pereira5, Luiz G E Vieira5, Fábio L Olivares6, Fábio O Pedrosa1, Emanuel M de Souza1 and Rose A Monteiro1*

Author Affiliations

1 Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, R. Francisco H. dos Santos s/n, Curitiba, 81531-990, Brazil

2 Department of Genetics, Universidade Federal do Paraná, R. Francisco H. dos Santos s/n, Curitiba, 81531-990, Brazil

3 Center for Agricultural and Environmental Sciences, Pontifícia Universidade Católica do Paraná, Rua Imaculada Conceição, 1155, Curitiba, 80215-901, Brazil

4 Department of General Biology, Universidade Estadual de Londrina, Rodovia Celso Garcia Cid PR-445 Km 380, Londrina, 86051-990, Brazil

5 Departament of Genetics and Molecular Biology, Instituto Agronômico do Paraná, Rodovia Celso Garcia Cid Km 375, Londrina, 86047-902, Brazil

6 Center of Bioscience and Biotechnology, Universidade Estadual do Norte Fluminense/CBB/LBCT, Av. Alberto Lamego, 2000, Campos dos Goytacazes, 28013-600, Brazil

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BMC Microbiology 2012, 12:98  doi:10.1186/1471-2180-12-98

Published: 6 June 2012

Abstract

Background

Herbaspirillum rubrisubalbicans was first identified as a bacterial plant pathogen, causing the mottled stripe disease in sugarcane. H. rubrisubalbicans can also associate with various plants of economic interest in a non pathogenic manner.

Results

A 21 kb DNA region of the H. rubrisubalbicans genome contains a cluster of 26 hrp/hrc genes encoding for the type three secretion system (T3SS) proteins. To investigate the contribution of T3SS to the plant-bacterial interaction process we generated mutant strains of H. rubrisubalbicans M1 carrying a Tn5 insertion in both the hrcN and hrpE genes. H. rubrisulbalbicans hrpE and hrcN mutant strains of the T3SS system failed to cause the mottled stripe disease in the sugarcane susceptible variety B-4362. These mutant strains also did not produce lesions on Vigna unguiculata leaves. Oryza sativa and Zea mays colonization experiments showed that mutations in hrpE and hrcN genes reduced the capacity of H. rubrisulbalbicans to colonize these plants, suggesting that hrpE and hrcN genes are involved in the endophytic colonization.

Conclusions

Our results indicate that the T3SS of H. rubrisubalbicans is necessary for the development of the mottled stripe disease and endophytic colonization of rice.