Variation and Phylogeny of Fusarium oxysporum Isolates Based on Nucleotide Sequences of Polygalacturonase Genes

The nucleotide sequences of two endopolygalacturonase genes (pg1 and pg5) and two exopolygalacturonase genes (pgx1 and pgx4), which encode members of a major family of secreted cell-wall-degrading enzymes (CWDEs), were compared to detect the extent of genetic variation among isolates of Fusarium oxysporum. The nucleotide variation rate in exons was 0.23-0.93%, higher than that in introns (0.01-0.64%) and untranslated regions (UTRs) (0.07-0.25%), resulting in 0.05-0.31% variation in amino acids. pgx1 exhibited the most genetic diversity. Phylogenetic analysis of the four genes, which reside on different chromosomes, revealed different evolutionary patterns for each. Our results suggest a biased evolution of the polygalacturonase genes of F. oxysporum, or alternatively, that the genes were acquired at different times during evolution.