ARP2/3 complex associates with peroxisomes to participate in pexophagy in plants

Abstract ARP2/3 is a heteroheptameric protein complex evolutionary conserved in all eukaryotic organisms. Its conserved role is based on the induction of actin polymerization at the interface between membranes and the cytoplasm. Plant ARP2/3 has been reported to participate in actin reorganization at the plasma membrane during polarized growth of trichomes and at the plasma membrane-endoplasmic reticulum contact sites. We demonstrate here that individual plant subunits of ARP2/3 fused to fluorescent proteins form motile dot-like structures in the cytoplasm that are associated with plant peroxisomes. ARP2/3 dot structure is found at the peroxisome periphery and contains assembled ARP2/3 complex and WAVE/SCAR complex subunit NAP1. This dot occasionally colocalizes with the autophagosome, and under conditions that affect the autophagy, colocalization between ARP2/3 and the autophagosome increases. ARP2/3 subunits co-immunoprecipitate with ATG8f marker. Since mutants lacking functional ARP2/3 complex have more peroxisomes than WT, we link the ARP2/3 complex on peroxisomes to the process of peroxisome degradation by autophagy called pexophagy. Additionally, several other peroxisomal proteins colocalize with ARP2/3 dot on plant peroxisomes. Our results suggest a specific role of ARP2/3 and actin in the peroxisome periphery, presumably in membrane remodelling. We hypothesize that this role of ARP2/3 aids processes at the peroxisome periphery such as peroxisome degradation through autophagy or regulation of peroxisomal proteins localization or function.