Phospholipids are present in extracellular fluids of imbibing sunflower seeds and are modulated by hormonal treatments

MARIANA CLELIA REGENTE; CORTI-MONZÓN, G.; DE-LA-CANAL, L.

JOURNAL OF EXPERIMENTAL BOTANY

Oxpord University Press

Año: 2008 vol. 59 p. 553 - 562

0022-0957

Phospholipids are well known messengers involved in developmental and stress responses mediating intracellular signalling. We have hypothesized on the existence of phospholipids that could participate in intercellular communication events through the apoplast of sunflower (Helianthus annuus) seeds. Here we show that extracellular washing fluids (EWF) obtained from seeds imbibed for two hours present diverse phospholipids. Lipid profiling by electro spray ionization tandem mass spectrometry revealed that the EWF display a particular composition, with phosphatidic acid (PA) and phosphatidylinositol (PI) being the major phospholipids. These profiles are clearly distinct from those of seed extract (SE), and comparative SDS-PAGE of EWF and SE followed by intracellular and plasma membrane marker analyses, allowed to discard a significant contamination of the EWF. Treatment of the seeds with 100ìM jasmonic acid (JA) induces changes in the profile of EWF phospholipids, leading to a decrease in PI content while the accumulation of phosphatidylinositol 4-phosphate (PI4P) and specific PA species is observed. On the other hand, the EWF from seeds subjected to 50ìM abscisic acid (ABA) treatment exhibit an increase in PA and phosphatidylglycerol levels. To our knowledge, this is the first report on the existence of phospholipids as extracellular components of seeds. Moreover, the modulation of PA, PI and PI4P levels by hormonal treatments further suggest their contribution to intercellular communication in planta.