PI4P accumulates extracellularly and triggers defence responses in tomato cell suspensions

GONORAZKY, A. G.; ANA MARIA LAXALT; MUNNIK, T.; DE LA CANAL, L

Mar del Plata

Congreso; SAIB; 2007

PL-P61. PI4P ACCUMULATES EXTRACELLULARLY AND TRIGGERS DEFENCE RESPONSES IN TOMATO CELL SUSPENSIONS Gonorazky AG, LaxaltAM, Munnik T, de la Canal L. Instituto de Investigaciones Biológicas, UNMdP. E-mail: gonorazk@mdp.edu.ar Various phospholipid molecules have recently been implicated in plant defence signalling. Until now, such molecules have been exclusively related to intracellular signalling. Here evidence is provided for a role of phosphatidylinositol 4-phosphate (PI4P) in intercellular signalling. We have analyzed and compared the intracellular and extracellular phospholipid profiles of [ Pi]- prelabeled tomato cell suspensions challenged with the fungal elicitor xylanase. These phospholipid patterns were found to be different from each other, being phosphatidylinositol phosphate (PIP) the most abundant phospholipid in the extracellular medium. There are three natural PIP isoforms occurring: PI3P, PI4P and PI5P. Two experimental approaches (PIP kinase assays and lipid overlay assays) have allowed the identification of extracellular PIP as PI4P. Exogenous application of PI4P to tomato cell suspensions triggered typical defence responses such as the production reactive oxygen species. However other negative phospholipids such as PA, phosphatidylinositol (PI) and phosphatidylinositol biphosphate (PIP2) also induced defence responses in tomato cell suspensions. The biological relevance of these data is discussed.