A role of villin-dependent F-actin organization in peroxisome motility in Arabidopsis cells

Actin microfilaments (F-actin) serve as the track for directional movement of organelles in plants. To understand how the F-actin network is employed for the movement of peroxisomes, essential organelles in plant metabolism, we analyzed mutants of three villin ( VLN ) genes, which encode the primary actin-bundling factor and are most actively expressed in vegetative tissues in Arabidopsis thaliana . We found that the vln4 mutation greatly exacerbated the growth and subcellular defects in vln2 vln3 . Compared to the wild-type cells, the double and triple vln mutants exhibit progressive reduction of stable F-actin bundles and rapid remodeling of the fine filaments. The defective F-actin network did not prevent peroxisomes from taking on both rapid and slow movements along the tracks but caused significantly reduced speed of movement and displacement distance of peroxisomes. Using a correlation analysis method, we classified the complex heterogeneous peroxisome movement patterns into clusters reflecting distinct movement directionalities. The vln triple mutant had significantly reduced number of peroxisomes with long-range and linear movement. Our results provide insights into how VLN-dependent F-actin organization is coupled with the complex pattern of peroxisome movement.