Defects in dynamics and functions of actin filament in Arabidopsis caused by the dominant-negative actin fiz1-induced fragmentation of actin filament.

We isolated frizzy1 (fiz1), a novel dominant actin mutant from Arabidopsis. In the fiz1 mutant, Glu272 was substituted with lysine in the hydrophobic loop of ACT8, which is very important for the polymerization. Live imaging of actin filaments revealed that the fiz1 mutation induced fragmentation of actin filaments in a semi-dominant manner. In addition, the dynamics of Golgi stacks and mitochondria were disrupted by the fiz1 effects. From these results, it was strongly suggested that the fiz1 mutation had dominant-negative effects on actin polymerization, which causes defects in the functions of actin filaments such as organelle transport.