Detection of phospholipids in apoplastic fluid of sunflower seeds

MARIANA REGENTE; LAURA DE LA CANAL

Pinamar, Buenos Aires, Argentina

Congreso; XLI Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2005

Sociedad Aregentina de Investigación Bioquímica y Biología Molecular

The apoplast of plants is an interconnected liquid layer surrounding the cells that transports water, micronutrients, amino acids, hormones, signaling molecules, RNA and proteins, serving as a conduct for the delivery of information containing macromolecules. Recent indirect evidences suggests the existence of putative lipid signals involved in long distance signaling upon stress. However, current knowledge on lipids molecules acting as signals is limited to intracellular events.  The aim of this work was to determine the presence of phospholipids (PLs) potentially involved in signaling mechanisms in the seed apoplastic fluids. The extracellular fluid (EF) from sunflower seeds was obtained by vacuum-infiltration and centrifugation. Western blot analyses indicate the absence of the intracellular marker glyceraldehide-3P-deshydrogenase (GAPDH) in the EF, indicating no significant intracellular contamination. Lipid fraction from the EF was submitted to thin layer chromatography (TLC) analysis showing the presence of several lipid spots. PLs were further identified by electrospray ionization mass spectrometry (ESI-MS). The analysis pointed out that phosphatidylinositol (PI), phosphatidic acid (PA) and phosphatidylglycerol were the most abundant components. Lysophosphatidyl glycerol, lysophosphatidyl choline, lysophosphatidylethanolamine, phosphatidylcholine and phosphatidylethanolamine were also detected, but as minor components of seed EF. This pattern is clearly different from that obtained by ESI-MS of total seed extracts. The presence in apoplastic fluids of PLs such as PI and PA, which are known to participate in intracellular signaling events, suggest that they may also have a role as long-distance signals in plants. Experiments are in progress to confirm this hypothesis.