Lipid droplet proteome plasticity in plant evolution, growth and development, and response to stress

Lipid droplets (LDs) are subcellular structures that occur in all plant cells and are composed of a core of hydrophobic molecules, such as triacylglycerols, surrounded by a phospholipid monolayer and various associated proteins. In recent years, proteomic studies have significantly increased the number of known LD proteins, revealing that the LD proteins that predominate in seeds already evolved in streptophyte algae. In multicellular plants, there are distinct differences across tissues regarding the composition of the LD proteome. There are also dynamic changes in the LD proteome during developmental processes, such as seedling establishment and senescence, and in response to abiotic and biotic stresses. Overall, the success of these proteomics studies has come not only from cataloging of LD protein compositions, but also the identification of previously unknown LD protein families. As a result, these studies have provided the framework for the functional characterization of LD proteins and their wide-ranging roles in LD biogenesis and degradation, metabolism, and during stress. In this review, we highlight the main differences in the LD proteomes across plant species, tissues, development and/or environmental factors, and provide descriptions of some of the key physiological and subcellular functions of the individual families of LD proteins.