Localization of a Plant LTP suggest a novel role of thid protein in lipid mobilization

PAGNUSSAT L. A., LOMBARDO M. C., DE LA CANAL L

Mar del Plata

Congreso; XLIII Anual Meeting SAIB; 2007

SAIB

Lipid transfer proteins (LTPs) are low molecular-mass proteins extensively studied in plants. The mayor characteristic of this family is its ability to transfer acyl lipids between artificial membranes in vitro. The extracellular localization of LTPs suggested its role in cutin assembly or defense, but to date, its biological function remains elusive. Our lab has characterized a sunflower LTP (Ha-AP10), present in seed apoplast. Recent evidences indicate that a fraction of Ha-AP10 is associated to the microsomal fraction. To determine the subcellular localization of this protein, we performed fluorimmunolocalization studies on germinating “Paraplast”-embedded sunflower seeds.This assay revealed that during germination Ha-AP10 has both apoplastic and intracellular localization. It also showed that the intracellular fraction of the LTP was bound to internal vesicles similar to oil bodies. This presumption was confirmed byWestern blot analysis of the oil bodies´ fraction using anti-Ha-AP10 antibodies as well as coimmunolocalization experiments using anti-oleosins (oil body membrane-specific proteins) antibodies. Carbon storage in the form of triacylglycerides (TAG) is responsible to fuel postgerminative growth in oilseeds but little is known about the transport of fatty acids from oil bodies to glyoxysomes, where betaoxidation and glyoxylate cycle take place. The presence of an LTP in oil body membranes suggests a novel role of this protein in fatty acid mobilization from the oil bodies to the glyoxysome.