Preliminar proteomic analysis supports the identification of sunflower extracellular vesicles.

CORTI MONZÓN GEORGINA; REGENTE MARIANA; MALDONADO ANA; JORRÍN JESÚS; PINEDO MARCELA; DE LA CANAL LAURA

Córdoba- España

Congreso; Second Joint Meeting COST Action 0603. European Plant Proteomics.; 2008

European Plant Proteomics

PRELIMINAR PROTEOMIC ANALYSIS SUPPORTS THE IDENTIFICATION OF SUNFLOWER EXTRACELLULAR VESICLES. Corti Monzon G, Regente M, Maldonado A, Jorrin J, Pinedo M and De la Canal L. INSTITUTO DE INVESTIGACIONES BIOLÓGICAS, Universidad Nacional de Mar del Plata- CC 1245 – 7600 - MAR DEL PLATA - ARGENTINA DEPARTAMENTO DE BIOQUÍMICA Y BIOLOGÍA MOLECULAR, Universidad de Córdoba - ESPAÑA   We have recently demonstrated the presence of diverse phospholipids in the extracellular fluid (EF) of sunflower (Helinathus annuus) seeds. Since phospholipids are insoluble in aqueous fluids we have hypothesized on the existence of vesicular structures in sunflower apoplast. The EF was then subjected to fractionation by centrifugation steps at 10000g, 40000g and 100000g and the pellets analyzed by transmission electronic microscopy. These observations revealed the presence of vesicles of around 100 nm with apparent membrane organization in the 40000g pellets. SDS-PAGE allowed the detection of several proteins in the vesicles fraction. However, using tryptic fragment fingerprinting only two proteins could be identified as most of the bands displayed low score values on data base searching. A lectin belonging to the jacalin family was unequivocally identified (score 206) in the vesicles, while a small GTP binding protein from the Rab subfamily was putatively identified (score 63, 48 % coverage).  This protein shows 78% of identity with human Rab11A, involved in both constitutive and regulated secretory pathways and localized to recycling endosomes and exosomes. The later are vesicular structures of endosomal origin  secreted to extracellular fluids in animal systems. It is becoming clear that exosomes have conserved functions in evolution. We are now presenting microscopic evidence suggesting the existence of exosome-like vesicles in the apoplast of plants, also supported by the presence of  Rab11A, a typical protein involved in vesicular traffic. Although proteomic analyses are difficult in non-sequenced species, this work shows that it could be extremely useful as a complement of physiological data.