A 51 kDa protein kinase of potato activated with hyphal wall components from Phytophthora infestans

In potato tuber tissue, treatment of fungal elicitor, hyphal wall component s (HWC) induces various plant defense reactions. As treatment of protein ki nase inhibitor prior to HWC treatment blocks some of defense reactions indu ced by HWC, involvement of protein kinases in plant defense induction is pr oposed. Here, we demonstrate HWC-induced activation of a 51-kDa protein kin ase (abbreviated p51-PK) using myelin basic protein as a substrate in potat o tuber discs. The activity of pS1-PK was not detected in the absence of ph osphatase inhibitor, NaF, and p51-PK was immunoprecipitated with antibody a gainst phosphotyrosine. Pretreatment of phospholipase C inhibitor, neomycin , and GTP-binding protein activator, mastoparan, partially inhibited the HW C-induced activation of p51-PK, suggesting possible involvement of phosphol ipase C and GTP-binding protein in the activation of p51-PK. Exogenously su pplied elicitors, salicylic acid and arachidonic acid, which are known to i nduce various defense responses in potato plants, also activated the protei n kinase showing the same migration as p51-PK on SDS-PAGE and different act ivation patterns. These results implied that p51-PK might be involved in se veral signal transduction pathways leading to plant defense responses initi ated by different stimuli.