BACKGROUND: Published accounts of horizontally acquired genes in plant-parasitic nematodes have not been the result of a specific search for gene transfer per se, but rather have emerged from characterization of individual genes. We present a method for a high-throughput genome screen for horizontally acquired genes, illustrated using expressed sequence tag (EST) data from three species of root-knot nematode, Meloidogyne species.
RESULTS: Our approach identified the previously postulated horizontally transferred genes and revealed six new candidates. Screening was partially dependent on sequence quality, with more candidates identified from clustered sequences than from raw EST data. Computational and experimental methods verified the horizontal gene transfer candidates as bona fide nematode genes. Phylogenetic analysis implicated rhizobial ancestors as donors of horizontally acquired genes in Meloidogyne.
CONCLUSIONS: High-throughput genomic screening is an effective way to identify horizontal gene transfer candidates. Transferred genes that have undergone amelioration of nucleotide composition and codon bias have been identified using this approach. Analysis of these horizontally transferred gene candidates suggests a link between horizontally transferred genes in Meloidogyne and parasitism.