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Actin cytoskeleton is involved in regulation of many processes in plants, for instance proper morphogenesis of the cells and of the whole organisms, organelle movement, regulation of cell division. Its dynamics and polymerization is regulated by various complexes and associated proteins which include ARP2/3 complex. This complex nucleates new actin filaments de novo and helps their branching. This diploma thesis deals with the role of actin and ARP2/3 complex in diverse processes in plant cells. The first part of the thesis concentrates on the role of actin in morphogenesis; the second section is focused on the endocytosis in epidermal cells. The investigation of the importance of individual plant cytoskeletal components suggests that microtubules are of key importance for plant growth. Impairing of actin cytoskeleton by latrunculin B caused inhomogeneous reaction of the plants. It is known that loss of ARP2/3 complex in A. thaliana plants results in the specific malformation of trichomes which are known as distorted trichomes. It was found that the loss of actin isoforms is not associated with severe malformation of trichomes. The most pronounced phenotype was observable in case of ACT7 protein loss. It was further found that the distorted phenotype was not induced by application of latrunculin B...

The cells are able to acquire variety of shapes, in which cytoskeleton plays an important role. Cytoskeleton influences deposition of cell wall materials, regulates vesicle movement in cell, participates in exocytosis and endocytosis. Cortical microtubules affect celulose accumulation in cell wall and determine direction of cell expansion, although the exact connection between microtubules and cellulose remains unclear. Actin promotes growth and contributes to its spatial regulation in both tip ang diffuse growing cells. Actin is important for secretion in expanding cells but its exact functions in cell growth regulation are not explained yet. Analysis of mutants, spectroscopic methods, cytoskeletal drugs, fluorescence proteins and other methods are used to better understand how actin and microtubule cytoskeleton are integrated during plant cell morphogenesis. Epidermal and trichome cells of Arabidopsis thaliana are a good model of research and they are used for most studies.