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Exocyst is a protein complex conserved in yeast, animals and plants. It mediates tethering of a secretory vesicle to the plasma membrane in the semifinal step of exocytosis. Several roles of exocyst in the processes of cell polarization in plant cells have been implied, including polarized growth of polen tubes and root hairs, cytokinesis, deposition of seed coat pectin and possibly autophagy. One of the most recent roles of exocyst includes also a response to bacterial and fungal pathogens. Exo70B2 and Exo70H1 subunits were shown to play prominent roles in this respect, with Exo70H1 being responsible for mediating defense against bacterial (Pseudomonas syringae) and Exo70B2 defense against both bacterial and fungal (Blumeria graminis) pathogens. Recently, new data appeared indicating the interaction between Exo70B1 and RIN4 and Exo70A1 and NOI6, respectively. RPM-1 interacting protein 4 (RIN4) is a well known negative regulator of both basal and effector-triggered resistance. This thesis shows interaction between NOI6 and several exocyst subunits, confirming previous data. I show here that exocyst subunints interact specifically with N terminus of NOI6 protein and that this interaction is lost in the shorter version of NOI6 mimicking AvrRpt2 cleavage. Since AvrRpt2 is an effector protein from...

Plants are sessile organisms that have to cope with the changes of their ambient environment. These changes include abiotic disturbances and stresses as well as biotic interactions with other organisms. In many of the biotic interactions, plant cells are hurt or damaged by various bacterial and fungal pathogens. Moreover, plants lack mobile immune cells, which would otherwise render them susceptible to most of these pathogens. Plants have, however, developed other mechanisms for suppressing the infection. Activating the components of the secretory pathway during resistance response is crucial step for suppressing the penetration and growth of pathogens. Fungal pathogens, such as powdery mildews, usually attempt to penetrate the cell wall in order to gain the access to protoplast providing nutrients and to exchange their virulence factors. On the other hand, pathogenic bacteria inhabit extracellular spaces of plant tissues. In both cases, however, the deposition of papilla into the plant cell wall was observed. Papilla thus seems to be the common defence mechanism. There is an increasing evidence confirming the indispensable role of polarized secretion in formation of papilla. Recently, SNARE proteins participating in papilla-associated defence have been described. PEN1 and SNAP33 syntaxins are of...