Reserve lipids and plant autophagy

Abstract

Autophagy is a universal mechanism that facilitates the degradation of unwanted cytoplasmic components in eukaryotic cells. In this review, we highlight recent developments in the investigation of the role of autophagy in lipid homeostasis in plants by comparison with algae, yeast, and animals. We consider the storage compartments that form the sources of lipids in plants, and the roles that autophagy plays in the synthesis of triacylglycerols and in the formation and maintenance of lipid droplets. We also consider the relationship between lipids and the biogenesis of autophagosomes, and the role of autophagy in the degradation of lipids in plants.

Keywords: Autophagy; beta-oxidation; endoplasmic reticulum; leaf senescence; lipid droplet; lipidomic; lipids; oil body; oleosome; triacylglycerol.

Fig. 1.

Schematic representation of the potential roles of autophagy in lipid degradation in Arabidopsis leaves. According to Fan et al. (2019) and Havé et al. (2019), autophagy may be involved in the recycling of lipids that originate from the plasma membrane and the endomembrane of several organelles, except for those of chloroplasts. While the stroma material of the chloroplasts is degraded through the macro-autophagy pathway, chlorophagy occurs through the micro-autophagy pathway (Izumi et al., 2019). Red arrows indicate autophagy-dependent lipid degradation pathways: double-ended arrows indicate that autophagy may be involved in both the degradation and replenishment of lipid droplets and fatty acids. LDs, lipid droplets; TAGs, triacylglycerols; FAs, fatty acids; SDP1, SUGARDEPENDENT1 triacylglycerol lipase; PDAT-1, phospholipid:diacylglycerol transferase, VLCFA, very-long-chain fatty acid; ER, endoplasmic reticulum.