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Open Access Research article

The complete genome sequence of Xanthomonas albilineans provides new insights into the reductive genome evolution of the xylem-limited Xanthomonadaceae

Isabelle Pieretti1, Monique Royer1, Valérie Barbe2, Sébastien Carrere3, Ralf Koebnik4, Stéphane Cociancich1, Arnaud Couloux2, Armelle Darrasse5, Jérôme Gouzy3, Marie-Agnès Jacques5, Emmanuelle Lauber3, Charles Manceau5, Sophie Mangenot2, Stéphane Poussier6, Béatrice Segurens2, Boris Szurek4, Valérie Verdier4, Matthieu Arlat7 and Philippe Rott1*

Author Affiliations

1 CIRAD, UMR 385 BGPI, Campus international de Baillarguet, TA A-54K, F-34398 Montpellier Cedex 5, France

2 Génoscope, Centre national de séquençage, CEA/DSV/IG/Genoscope, 2 rue Gaston Cremieux, F-91057 Evry Cedex, France

3 Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR CNRS-INRA 2594/441, F-31320 Castanet-Tolosan, France

4 Laboratoire Génome et Développement des Plantes, Université de Perpignan via Domitia - CNRS - IRD, UMR 5096, 911 Avenue Agropolis, BP 64501, F-34394 Montpellier cedex 5, France

5 INRA, UMR 077 PaVé, F-49071 Beaucouzé, France

6 Agrocampus Ouest centre d'Angers, UMR 077 PaVé, F-49071 Beaucouzé, France

7 Université de Toulouse, UPS, 118 Route de Narbonne, F-31062 Toulouse, France

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BMC Genomics 2009, 10:616  doi:10.1186/1471-2164-10-616

Published: 17 December 2009

Abstract

Background

The Xanthomonadaceae family contains two xylem-limited plant pathogenic bacterial species, Xanthomonas albilineans and Xylella fastidiosa. X. fastidiosa was the first completely sequenced plant pathogen. It is insect-vectored, has a reduced genome and does not possess hrp genes which encode a Type III secretion system found in most plant pathogenic bacteria. X. fastidiosa was excluded from the Xanthomonas group based on phylogenetic analyses with rRNA sequences.

Results

The complete genome of X. albilineans was sequenced and annotated. X. albilineans, which is not known to be insect-vectored, also has a reduced genome and does not possess hrp genes. Phylogenetic analysis using X. albilineans genomic sequences showed that X. fastidiosa belongs to the Xanthomonas group. Order of divergence of the Xanthomonadaceae revealed that X. albilineans and X. fastidiosa experienced a convergent reductive genome evolution during their descent from the progenitor of the Xanthomonas genus. Reductive genome evolutions of the two xylem-limited Xanthomonadaceae were compared in light of their genome characteristics and those of obligate animal symbionts and pathogens.

Conclusion

The two xylem-limited Xanthomonadaceae, during their descent from a common ancestral parent, experienced a convergent reductive genome evolution. Adaptation to the nutrient-poor xylem elements and to the cloistered environmental niche of xylem vessels probably favoured this convergent evolution. However, genome characteristics of X. albilineans differ from those of X. fastidiosa and obligate animal symbionts and pathogens, indicating that a distinctive process was responsible for the reductive genome evolution in this pathogen. The possible role in genome reduction of the unique toxin albicidin, produced by X. albilineans, is discussed.