JXB Advance Access published online on January 22, 2008
Journal of Experimental Botany, doi:10.1093/jxb/erm329
REVIEW-ARTICLE |
Phospholipids are present in extracellular fluids of imbibing sunflower seeds and are modulated by hormonal treatments
Instituto de Investigaciones Biológicas, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, CC 1245, 7600 Mar del Plata, Buenos Aires, Argentina
* To whom correspondence should be addressed. E-mail: mregente{at}mdp.edu.ar
Phospholipids are well known messengers involved in developmental and stress responses mediating intracellular signalling. It has been hypothesized that phospholipids exist which could participate in intercellular communication events through the apoplast of sunflower (Helianthus annuus) seeds. Here it is shown that extracellular washing fluids (EWFs) obtained from seeds imbibed for 2 h contain diverse phospholipids. Lipid profiling by electrospray ionization tandem mass spectrometry revealed that the EWFs have 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 a significant contamination of the EWF to be discarded. Treatment of the seeds with 100 µM 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 50 µM 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 suggests their contribution to intercellular communication in planta.
Key words: Apoplast, phospholipids, seed, sunflower
Received 15 August 2007; Accepted 27 November 2007