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.