Development of new molecular tools to study secretion in plant cells:FP6 MTKD-CT-2004-509253

It has been affirmed that only constitutive secretory pathways function in higher plants- that regulated secretion does not occur in these cells, at least not in the sense of the neuronal model. Certainly, many of the best-known secretory models in plants appear more closely allied to the idea of constitutive secretion but exceptions are known. At least two exocytotic pathways exist in barley aleurone protoplasts: one, involved in cell expansion, is Ca2+ -independent and whose regulation is currently not known and an other, involved in cell damage response, is stimulated by Ca2+ and modulated by GTP-binding proteins. It is likely that the constitutive and regulated secretory pathways are present toghether in many different cell types. During exocytosis, vescicles fuse with the plasma membrane that results in the delivery to the plasma membrane of various kinds of material: membrane itself and membrane-associated proteins; cell wall precursors and extracellular proteins. This process must be highly controlled to modulate the arrival of very different materials in all cell kinds of a plant. In animals and yeast the situation is complex and many genes are involved in the process; homologue genes involved in secretion have been identified also in plants (Nt-Syr1, Knolle, Gnom, Keule, GTPases). The Syntaxin homologue Nt-Syr1 (recently re-named SYP 121) was recently isolated in a functional screen for ABA signaling elements. Competition of a soluble variant of Nt-Syr1 with the endogenous protein, strongly affects secretion of reporter proteins, thus representing a powerfull tool to study “regulated”, ABA dependent, secretion. We set up a complex experimental system in N. tabacum to monitor secretion of reporter proteins (GFP and GUS) and cell wall polysaccharides. Starting material was produced in collaboration with the group of Prof. MR Blatt in Glasgow. New molecular tools may be developed to increase quality and impact of the current research but human resources are limited and potential partners geographically distant. Transfer of knowledge is needed to extend the study to specific functions of different SNARE proteins and develop better markers. To make Marie Curie fellowships available for this research will produce a positive effect on training and internationalization of young scientists and student in Lecce, will integrate European research and maintain the activity mainly in Lecce where it started.