FIRST EVIDENCE OF EXTRACELLULAR PHOSPHATIDYLINOSITOLPHOSPHATES INVOLVED IN PLANT DEFENSE RESPONSES

GONORAZKY, ANA G.; LAXALT ANA M ; MUNNIK TEUN A AND DE LA CANAL LAURA

Pinamar, Rosario

Congreso; 10th Congress of PABMB, 41th Congress of SAIB and 20th Congress of SAN; 2005

Systemic acquired resistance (SAR) is a broad-spectrum resistance mechanism in plants that is activated in naive organs after exposure of another organ to a necrotizing pathogen. It has been reported that a lipid transfer protein (LTP) triggers SAR by translocating / transmitting a mobil signal from the infected tissue to distal organs of the plants. It has been hypothesized that this mobil signal could be a lipid molecule. Since phospholipid molecules (PLs) are emerging as novel second messengers in plant defense signaling, the objective of this work was firstly to determine if there are extracellular PLs, and secondly, if they could be involved in plant defense responses. To this aim, we analyzed and compared the cellular and extracellular PL profile of suspension cultured tomato cells pre-labeled with [32P] ortophosphate by thin layer chromatography. We detected PLs in the extracellular medium and their pattern was different from cell PL profile. Moreover we found that phosphatidylinositolphosphate (PIP) was the most abundant PL in the extracellular medium, and that treatment of suspension tomato cells with the pathogenic elicitor xylanase increased extracellular PIP levels substantially. Finally, we demonstrate that exogenous addition of PIP triggers typical defense responses such as production of reactive oxygen species (ROS) and cell death, both in a dose dependent manner. These indicate that extracellular PIPs are involved in plant defense responses, and suggest their putative role in plant signaling.