Actin nucleation in plant cell

The ability of plant cells to nucleate actin is important especially for dynamic of intracellular movements of organelles and vesicles, cell structure and growth organization and coordination of endo- and exocytosis . Actin nucleation means the development of new actin filaments from G-actin. Actin associated proteins - Arp2/3 complex and formins serve for this purpose. Arp2/3 complex polymerizes new "daughter " filament from the side of the "parent" filament at an angle of 70 degrees and after the nucleation remains at minus end of filaments, thus inducing branching of filaments. Nucleation by Arp2/3 complex further requires nucleation promoting factors - NPFs. Deletion of subunits of Arp2/3 complex is often lethal in animal cells. On the other hand, deletion results in rather mild phenotype in plants. Formins catalyze the formation of direct actin fibers and remain on the plus end of the fiber after nucleation. There are multiple isoforms of formins in plants than in animals, which suggest an important role of formins in plants. New actin nucleators Cobl, Lmod, Spire, JMY and APC containing WH2 (WASP homology 2) domain were identified in non-plant cells. This type of actin nucleation was not described in plants. Kew words: Actin, Arp2/3 complex, formins, Scar/WAVE, Cobl, Lmod, Spir