Characterization of two Phytophthora infestans Auxiliary Activity Family 17 genes involved in pathogenicity

Abstract The plant cell wall, composed of complex polysaccharides, provides the first line of defense against invading plant pathogens. Therefore, many plant pathogens, including the oomycete Phytophthora infestans, are thought to possess secreted cell wall degrading enzymes (CWDEs) that break down the host cell wall and improve pathogen entry. One group of CWDEs is lytic polysaccharide monooxygenases, a type of pectinase encoded by genes in the Auxiliary Activity Family 17 (AA17) class. The role of these AA17 genes in late blight disease of potato, including the genes PITG_04949 and PITG_13520, is not fully understood. This study analyzes the AA17 family genes and reports the presence of the initiator element and flanking promoter region supramotif in over half of these genes, providing evidence that suggests shared regulatory mechanisms. In addition, PITG_04949 and PITG_13520 were cloned and structurally characterized and their expression levels examined at four timepoints during plant infection. Gene expression analysis revealed that both genes are significantly up-regulated at 12, 24, 36, and 48 hours post inoculation (hpi), with peak expression at 36 hpi, suggesting that these genes may be important for infection of potato plants by P. infestans.