Comparing Xanthomonas

Comparison of the sequence of two phytopathogen genomes reveals insights into the molecular basis for host specificity and pathogenicity.

The Scientist Staff

In the 23 May Nature, da Silva et al. report the comparative analysis of genomes of two bacterial phytopathogens that differ in their host specificity and pathogenicity (Nature 2002, 417:459-463).

Xanthomonasaxonopodis pv citri (Xac) affects citrus cultivars and causes canker lesions. In contrast, Xanthomonas campestris pv. campestris (Xcc) affects crucifers and causes black rot. Each genome contains a circular chromosome of around 5 megabases. In addition, Xac carries two plasmids, of 34 and 65 kilobases. The chromosomes display a high degree of colinearity, suggesting as few as three major rearrangement events have occurred in the time that separates them, and they have as many as 80% of genes in common. Regions around the putative termini of replication contain most strain-specific genes that may be related to pathogenesis. Xac-specific genes include those for fungicide synthesis, secreted toxins, and nodulation pathways. Xcc-specific...

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