Citrus canker genome sequenced
Researchers from the US and Brazil have completed draft sequences of two strains of the bacterium, Xanthomonas fuscans subsp aurantifolii a causative agent of the as yet untreatable disease, citrus canker. It can be caused by three different strains of the bacterium, dubbed A, B and C, which differ in virulence. Information from the latest sequences (strains B and C) in conjunction with that from the sequence for the most virulent Xanthomonas strain, X citri subsp citri (strain A), which was completed in 2002, enabled the researchers to identify key proteins, known as effector proteins, expressed by the strains but not other Xanthomonas species. They also found that some genes in the less virulent B and C strain genomes were absent from the X citri genome. The missing genes could encode effector proteins that are recognised by some citrus species in a way that triggers a resistance response that interferes with disease development.