Peroxisome Function, Biogenesis, and Dynamics in Plants

Abstract

Recent advances highlight understanding of the diversity of peroxisome contributions to plant biology and the mechanisms through which these essential organelles are generated.

Figure 1.

Plant peroxisome functions. Peroxisomes house a variety of catabolic and biosynthetic reactions (Reumann and Bartel, 2016), several of which generate H₂O₂ and other ROS (orange). β-oxidation (red) is used to catabolize fatty acids (purple) and in the synthesis of several hormones (blue). Peroxisomal ROS can be inactivated by catalase and other enzymes within the peroxisome or can exit the peroxisomes to serve signaling roles. OPC8, 3-oxo-2-(2′-pentenyl)-cyclopentane-1-octanoic acid; OPDA, 12-oxo-phytodienoic acid.

Figure 2.

Peroxisome dynamics. Peroxisome biogenesis and division are coordinated by peroxins (numbered ovals) that coordinate peroxisomal membrane protein insertion into the ER or the peroxisomal membrane. After preperoxisomes bud from the ER, peroxisomes mature through import of matrix proteins. Peroxisomes can be degraded by pexophagy, a type of specialized autophagy. Dynamic peroxisome extensions (peroxules) assist peroxisome interactions with other organelles and can be associated with peroxisome division. PEX11 promotes peroxisome division together with a group of proteins (PMD1, FIS1, DRP) that also act in division of mitochondria or chloroplasts. PMP, peroxisomal membrane protein.

Figure 3.

Matrix protein import and receptor recycling. Matrix proteins harboring peroxisome-targeting signals are synthesized in the cytosol, where they are recognized by the PEX5 (PTS1 proteins) or PEX7 (PTS2 proteins) receptors. Receptor-cargo complexes dock with PEX13-PEX14, which allows cargo release into the matrix. Membrane-associated PEX5 is ubiquitinated near the N-terminus by enzymes in the RING complex assisted by the PEX4 ubiquitin-conjugating enzyme. Monoubiquitinated or diubiquitinated PEX5 is recycled via removal from the membrane by the PEX1-PEX6 ATPase complex whereas PEX5 polyubiquitination can lead to PEX5 proteasomal degradation or may trigger pexophagy. PTS2 proteins are processed in the matrix by the DEG15 protease. C, C-terminus; N, N-terminus; Ub, ubiquitin.