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Open Access Research article

Genomic insights into strategies used by Xanthomonas albilineans with its reduced artillery to spread within sugarcane xylem vessels

Isabelle Pieretti1, Monique Royer1, Valérie Barbe2, Sébastien Carrere3, Ralf Koebnik4, Arnaud Couloux2, Armelle Darrasse5, Jérôme Gouzy3, Marie-Agnès Jacques5, Emmanuelle Lauber6, Charles Manceau5, Sophie Mangenot2, Stéphane Poussier7, Béatrice Segurens2, Boris Szurek4, Valérie Verdier4, Matthieu Arlat8, Dean W Gabriel9, Philippe Rott1 and Stéphane Cociancich110*

Author affiliations

1 CIRAD, UMR BGPI, F-34398 Montpellier Cedex 5, France

2 CEA/DSV/IG/Génoscope, Centre National de Séquençage, F-91057 Evry Cedex France

3 INRA, UMR LIPM, F-31326 Castanet-Tolosan Cedex France

4 IRD, UMR RPB, F-34394 Montpellier Cedex 5, France

5 INRA, UMR IRHS, F-49071 Beaucouzé France

6 CNRS, UMR LIPM, F-31326 Castanet-Tolosan Cedex France

7 Université de la Réunion, UMR PVBMT, F-97715 Saint-Denis La Réunion, France

8 Université Paul Sabatier, UMR LIPM, F-31326 Castanet-Tolosan Cedex France

9 University of Florida, Plant Pathology Department, Gainesville FL 32605 USA

10 UMR BGPI, Campus International de Baillarguet, TA A-54/K, F-34398 Montpellier Cedex 5, France

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Citation and License

BMC Genomics 2012, 13:658  doi:10.1186/1471-2164-13-658

Published: 21 November 2012

Abstract

Background

Xanthomonas albilineans causes leaf scald, a lethal disease of sugarcane. X. albilineans exhibits distinctive pathogenic mechanisms, ecology and taxonomy compared to other species of Xanthomonas. For example, this species produces a potent DNA gyrase inhibitor called albicidin that is largely responsible for inducing disease symptoms; its habitat is limited to xylem; and the species exhibits large variability. A first manuscript on the complete genome sequence of the highly pathogenic X. albilineans strain GPE PC73 focused exclusively on distinctive genomic features shared with Xylella fastidiosa—another xylem-limited Xanthomonadaceae. The present manuscript on the same genome sequence aims to describe all other pathogenicity-related genomic features of X. albilineans, and to compare, using suppression subtractive hybridization (SSH), genomic features of two strains differing in pathogenicity.

Results

Comparative genomic analyses showed that most of the known pathogenicity factors from other Xanthomonas species are conserved in X. albilineans, with the notable absence of two major determinants of the “artillery” of other plant pathogenic species of Xanthomonas: the xanthan gum biosynthesis gene cluster, and the type III secretion system Hrp (hypersensitive response and pathogenicity). Genomic features specific to X. albilineans that may contribute to specific adaptation of this pathogen to sugarcane xylem vessels were also revealed. SSH experiments led to the identification of 20 genes common to three highly pathogenic strains but missing in a less pathogenic strain. These 20 genes, which include four ABC transporter genes, a methyl-accepting chemotaxis protein gene and an oxidoreductase gene, could play a key role in pathogenicity. With the exception of hypothetical proteins revealed by our comparative genomic analyses and SSH experiments, no genes potentially involved in any offensive or counter-defensive mechanism specific to X. albilineans were identified, supposing that X. albilineans has a reduced artillery compared to other pathogenic Xanthomonas species. Particular attention has therefore been given to genomic features specific to X. albilineans making it more capable of evading sugarcane surveillance systems or resisting sugarcane defense systems.

Conclusions

This study confirms that X. albilineans is a highly distinctive species within the genus Xanthomonas, and opens new perpectives towards a greater understanding of the pathogenicity of this destructive sugarcane pathogen.