Clathrin-Mediated Endocytosis in Plants: Historical to Modern Advances

Clathrin-mediated endocytosis (CME) is vital to plant physiology; however, the molecular details of how it functions in these complex multicellular eukaryotes remain to be defined relative to model yeast and animal systems. In this review, we explore potential reasons for this including a discussion of the debate of the existence of CME in plants, and the development of tools which have recently advanced our understanding of plant CME, including visualisation of live CME events in intact plants, and ultrastructural and proteomic analysis of plant clathrin-coated vesicles. In addition, we present an updated schematic of the temporal and spatially distinct stages of plant CME that attempts to consolidate our current understanding and to serve as a working model for further study of plant CME. Plants occupy a distinct branch of the evolutionary tree of life relative to yeast and animal systems with their own cellular constraints (e.g., extremely high intracellular turgor pressure conditions). Thus, while the core CME machinery that was predicted to have already been present in the Last Eukaryotic Common Ancestor is conserved in plants, it has needed to evolve to overcome these plant cellular constraints. Thus, in this review, we wish to highlight plants as important model organisms for understanding the overall principles governing CME and how it can adapt in mechanically and biochemically distinct ways.