Calcium-dependent protein kinases are involved in potato signal transduction in response to race-specific elicitors from the oomycete Phytophthora infestans.

BLANCO F, ZANETTI ME AND DALEO G.

JOURNAL OF PHYTOPATHOLOGY-PHYTOPATHOLOGISCHE ZEITSCHRIFT

Año: 2008 vol. 156 p. 53 - 61

0931-1785

Plant response to pathogens involves an intricate network of signal transduction pathways. Here, potato cell cultures were used to study signal transduction in response to elicitors from Phytophthora infestans. Pre-treatment of cells with Ser/Thr protein kinase inhibitors, EGTA, calmodulin antagonists or a channel blocker abolished the induction of two enzymes involved in defense responses, phenylalanine ammonia-lyase (PAL) and peroxidase. Phosphatase inhibitors caused an increase of these activities in the absence of elicitors. Hyphal cell wall components from an incompatible race (HWC 0) produced a rapid and transient increment of histone phosphorylation, whereas induction by HWC from a compatible race (HWC C) was less pronounced and more sustained. Since activities were calcium dependent, a fraction enriched in calcium-dependent protein kinases (CDPKs) was obtained by DEAE chromatography. Fractions from HWC 0 and HWC C treated cells presented higher kinase activity than that from untreated cells. Moreover, total activity was higher in the incompatible than in the compatible interaction. Activity was calcium dependent, partially inhibited by calmodulin antagonists and able to phosphorylate syntide-2, a specific substrate of CDPKs. An in-gel kinase assay showed the presence of a band of approximately 50 kDa whose activity was higher in HWC 0 than in HWC C treated cells and was not detected in control extracts. This report presents evidences of the differential activation of CDPKs in response to elicitors from different races of P. infestans, revealing that these protein kinases participate in the defense response to oomycete.