Phytophthora sojae undergoes many developmental changes throughout its lifecycle from freely swimming zoospores to vegetative mycelium. These changes in development are accompanied by changes in gene expression; however, little is known about gene regulation in this organism. During infection effector proteins are secreted and act as one of the major virulence determinants of P. sojae. Avirulence genes have been long sought after because these genes control race-cultivar compatibility. Different strains of P. sojae have been shown to carry copies of the same effectors but display variation in expression; gene silencing mechanism of some of these genes is not known.
One common epigenetic mechanism used to regulate gene expression by both prokaryotes and eukaryotes is DNA methylation, however; the DNA methylation status of the soybean pathogen P. sojae has yet to be shown. We provide evidence of cytosine methylation in the promoter regions of two known Avr effectors, Myb DNA-binding proteins, and the housekeeping gene actin by the method of MeDIP. DNA methylation was detected in a range of genes suggesting that P. sojae employs DNA methylation as one mechanism of gene regulation.