Genomics Select

The Irish potato famine, as well as countless other potato crop failures, was caused by the fungus-like oomycete pathogen Phyophthora infestans. This species has proven to be resilient because of its ability to rapidly evolve genetic weaponry to overcome host resistance. Haas et al. (2009) now report the complete genome sequence of P. infestans. The genome reveals an extensive and complex expansion of genetic material compared with the genomes of other members of this genus. In particular, the analysis indicates that families of genes critical to infection undergo frequent turnover and expansion. This may be due to their location in the genome within regions enriched in transposable elements and repeat sequences that are prone to proliferate. Although these genes themselves are not encoded by transposons, the preponderance of mobile elements in the genomic regions where these genes reside likely facilitates recombination accounting for the rapid loss and gain of these genes. These dynamics speed the diversification of the genes promoting infection and probably contribute to the adaptability and evolutionary success of P. infestans. The genome sequence of P. infestans will be a useful tool for understanding more about the biology and potential Achilles’ heel of this threatening pathogen. B.J. Haas et al. (2009). Nature 461, 393–398.