Pieretti Isabelle, Cociancich Stéphane, Bolot Stéphanie, Carrère Sébastien, Morisset Alexandre, Rott Philippe, Royer Monique
CIRAD UMR BGPI, TA A-54/K, Campus International de Baillarguet, F-34398 Montpellier Cedex 5, France.
INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, 24 Chemin de Borde Rouge-Auzeville CS52627, F-31326 Castanet Tolosan Cedex, France.
Genes (Basel). 2015 Jul 23;6(3):714-33. doi: 10.3390/genes6030714.
Xanthomonas albilineans is the bacterium responsible for leaf scald, a lethal disease of sugarcane. Within the Xanthomonas genus, X. albilineans exhibits distinctive genomic characteristics including the presence of significant genome erosion, a non-ribosomal peptide synthesis (NRPS) locus involved in albicidin biosynthesis, and a type 3 secretion system (T3SS) of the Salmonella pathogenicity island-1 (SPI-1) family. We sequenced two X. albilineans-like strains isolated from unusual environments, i.e., from dew droplets on sugarcane leaves and from the wild grass Paspalum dilatatum, and compared these genomes sequences with those of two strains of X. albilineans and three of Xanthomonas sacchari. Average nucleotide identity (ANI) and multi-locus sequence analysis (MLSA) showed that both X. albilineans-like strains belong to a new species close to X. albilineans that we have named "Xanthomonas pseudalbilineans". X. albilineans and "X. pseudalbilineans" share many genomic features including (i) the lack of genes encoding a hypersensitive response and pathogenicity type 3 secretion system (Hrp-T3SS), and (ii) genome erosion that probably occurred in a common progenitor of both species. Our comparative analyses also revealed specific genomic features that may help X. albilineans interact with sugarcane, e.g., a PglA endoglucanase, three TonB-dependent transporters and a glycogen metabolism gene cluster. Other specific genomic features found in the "X. pseudalbilineans" genome may contribute to its fitness and specific ecological niche.
白叶枯病菌是导致甘蔗叶烧病（一种甘蔗致命病害）的细菌。在黄单胞菌属中，白叶枯病菌呈现出独特的基因组特征，包括存在显著的基因组侵蚀、一个参与杀稻菌素生物合成的非核糖体肽合成（NRPS）基因座，以及沙门氏菌致病岛-1（SPI-1）家族的III型分泌系统（T3SS）。我们对从不同寻常的环境中分离出的两株类白叶枯病菌株进行了测序，即从甘蔗叶上的露珠以及野生黍稷中分离得到的菌株，并将这些基因组序列与两株白叶枯病菌株和三株甘蔗黄单胞菌的序列进行了比较。平均核苷酸同一性（ANI）和多位点序列分析（MLSA）表明，这两株类白叶枯病菌株均属于一个与白叶枯病菌相近的新物种，我们将其命名为“假白叶枯病菌”。白叶枯病菌和“假白叶枯病菌”具有许多共同的基因组特征，包括（i）缺乏编码过敏反应和致病性III型分泌系统（Hrp-T3SS）的基因，以及（ii）可能发生在这两个物种共同祖先中的基因组侵蚀。我们的比较分析还揭示了可能有助于白叶枯病菌与甘蔗相互作用的特定基因组特征，例如一种PglA内切葡聚糖酶、三种TonB依赖性转运蛋白和一个糖原代谢基因簇。在“假白叶枯病菌”基因组中发现的其他特定基因组特征可能有助于其适应性和特定生态位。
