Detection of Endogenous Phosphatidylinositol 4,5–bisphosphate in Phytophthora cinnamomi.

Plant diseases caused by Phytophthora species are serious threats to agriculture and the natural environment. Genome sequencing has revealed the lack of a gene for canonical phospholipase C (PLC), an enzyme that was hitherto thought to be ubiquitous in eukaryotes. PLC acts in the hydrolysis of phosphatidylinositol 4,5–bisphosphate (PtdIns‐4,5‐P2), a membrane‐bound phospholipid critical for signal initiation in many cellular processes. Previous studies have not provided evidence of endogenous PtdIns‐4,5‐P2 in Phytophthora and, in the absence of canonical PLC, argued for redundancy or loss in the PLC pathway in Phytophthora. Using liquid chromatography mass spectrometry, we have detected endogenous PtdIns‐4,5‐P2 in Phytophthora cinnamomi. This is the first identification of the phospholipid in the genus, and is significant because it indicates that the signal transduction pathway of the PLC product, inositol 1,4,5‐trisphosphate (IP3), may have been retained in Phytophthora incorporating an as‐yet unidentified homolog or analog of PLC. [ABSTRACT FROM AUTHOR]