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

Actin microfilaments (F-actin) serve as tracks for myosin-driven organelle movement in plants. To understand how the F-actin network supports organelle movement, we examined the motility of peroxisomes as a common proxy for overall organelle motility in Arabidopsis thaliana. Using mutants of three villin (VLN) genes that encode major actin-bundling proteins that are actively expressed in vegetative tissues, we found that the vln4 mutation exacerbated the growth and subcellular F-actin defects in vln2 vln3. Compared to wild-type cells, the double and triple vln mutants exhibited progressive reduction of stable F-actin bundles and rapid remodeling of the fine filaments into a dynamic mesh. The defective F-actin organization caused significantly reduced mean speed and displacement distance of peroxisomes, although both rapid and slow movements were observed. Correlation analysis grouped complex heterogeneous peroxisome movement patterns into clusters reflecting distinct movement patterns. The vln triple mutant had significantly fewer peroxisomes with long-range and linear movement but produced actin mesh network sufficient to retain basal peroxisome function. Our results provide insights into how VLN-dependent F-actin organization is coupled with the complex patterns of actomyosin-mediated organelle movement.