Abstract:Phytophthora genus, including the significant causal agents of plant diseases such as Phytophthora sojae, belongs to the oomycetes in the kingdom of Stramenopiles, which are evolutionarily distant from ‘true’ fungi. Because gene knockout and multiple other conventional molecular genetic manipulation technologies are not feasible for Phytophthora species to date, researches on the molecular mechanisms of growth, development, and pathogenesis were hampered. In this study, we combined the integrated approaches of genomics and transcriptomics to identify and compare protein kinase genes, especially MAPKs, from several representative plant-pathogenic oomycetes and fungi, and then did further analyses on the MAPK genes in P. sojae, for example, gene structures, protein domains, and transcription patterns, etc.. The results showed that the plant-pathogenic-oomycetes contain more protein kinases (including MAPKs) than fungi, and the MAPKs from oomycetes and relative species diatom exhibited a distant evolution relationship with fungi in phylogenetic study. A total of 14 MAPKs were found in P. sojae, in which 4 contained novel phosphorylation lip sequences in the MAPK domain, i.e., SEY, THE, and TKH, and 7 contained additional functional domains related to intracellular signal transduction, i.e., PH, C2, WW, and PAS. Transcription patterns indicated that most of the MAPKs played important roles in all or certain stages of growth, development, and pathogenesis of P. sojae. This study on protein kinases, especially MAPKs, revealed the specifity and complexity of oomycetes in intracellular signal transduction networks and mechanisms when compared with the fungi. These results will provide new insights for further study on biological functions and mechanisms of signal regulation of Phytophthora MAPKs.