New perspectives on lipid droplets in Arabidopsis leaves: biogenesis, resident proteins and functional diversity

Lipid droplets (LDs) are ubiquitous eukaryotic organelles for neutral lipid storage and have long been studied primarily in seeds for storing carbon and energy. However, accumulating evidence indicates that LDs are also abundant and highly dynamic in vegetative tissues such as leaves. In Arabidopsis thaliana, diverse abiotic and biotic stresses induce triacylglycerol accumulation and LD formation in leaves. Recent advances in lipid metabolism research, mass spectrometry-based proteomics, and genetic analysis have substantially advanced our understanding of leaf LD biogenesis, composition, and function. Proteomic studies have identified numerous LD-localized proteins, including regulators of LD formation, enzymes involved in lipid synthesis and modification, cytoskeleton-associated proteins, and factors linked to stress responses and protein quality control. In parallel, analyses of mutants with altered LD accumulation have revealed key roles for lipid trafficking, sterol homeostasis, carbon allocation, and peroxisomal lipid degradation. Together, these findings redefine leaf LDs as multifunctional organelles that integrate lipid metabolism with environmental stress responses and cellular homeostasis. This review summarizes recent progress in identifying LD-associated proteins and genetic regulators to discuss emerging concepts regarding the diverse roles of LDs in plant leaves.