FISSION1A and FISSION1B proteins mediate the fission of peroxisomes and mitochondria in Arabidopsis.

Peroxisomes and mitochondria are metabolically diverse organelles that act in concert in a number of pathways in eukaryotes, including photorespiration and lipid mobilization in plants. The division machineries of these two types of organelles also share several components such as dynamin-related proteins (DRPs) and their organelle anchor, the FISSION1 (FIS1) protein. In Arabidopsis, members of the DRP3 and FIS1 small protein families, namely DRP3A, DRP3B, FIS1A, and FIS1B, are each dual-targeted to peroxisomes and mitochondria and are required for the division of both organelles; DRP3A and DRP3B are partially redundant in function. To further determine the contribution of FIS1A and FIS1B to the division of peroxisomes and mitochondria, we analyzed plants overexpressing FIS1A or FIS1B and mutants in which the functions of both proteins were disrupted. Domains in FIS1A and FIS1B required for peroxisomal targeting were also dissected. Our results demonstrate that FIS1A and FIS1B play rate-limiting and partially overlapping roles in promoting the fission of peroxisomes and mitochondria. Furthermore, although the C-terminus of FIS1 is both necessary and sufficient for targeting to peroxisomes, the role of the short C-terminal segment adjacent to the transmembrane domain may differ among diverse species in peroxisomal targeting.