Fluid-Phase Endocytosis in Plant Cells

The uptake of nutrients by plant cells has been traditionally believed to be mediated by membrane-bound carriers. However, the last decade has seen an increase in evidence pointing to the parallel uptake by fluid-phase endocytosis (FPE). Recent advances in plant endocytosis reveal that this is true for heterotrophic cells, whether storage parenchyma, cell suspensions, or nutrient absorbing cells of carnivorous plants. Uptake of extracellular matrix components, endocytic markers, and sugar analogs in a wide variety of heterotrophic cells has confirmed the uptake of extracellular fluids and their transport to the vacuole. Furthermore, there is evidence to indicate the passage through an intracellular compartment where solutes are distributed. The precise nature of FPE has not been revealed; however, evidence using specific inhibitors, CdSe/ZnS quantum dots in combination with other FPE markers and inhibitors such as ikargalukin, points to the clathrin-independent nature of FPE and its possible association with flotillin. That FPE operates in conjunction with membrane-bound transporters in the uptake of solutes is supported by experiments analyzing uptake kinetics of the fluorescent endocytic marker Alexa-488 in the presence of sucrose and membrane-bound transporters and endocytic inhibitors. The mechanisms of membrane remodeling to accommodate the addition of membrane and aqueous volume to the vacuole during FPE remain unresolved. E. Etxeberria (&) Department of Horticultural Sciences, Citrus Research and Education Center, University of Florida/IFAS, 700 Experiment Station Road, Lake Alfred, FL 33850, USA e-mail: [email protected] J. Pozueta-Romero E. B. Fernández Instituto de Agrobiotecnologia, Universidad Publica de Navarra/Consejo de Investigaciones Cientificas, Gobierno de Navarra, Mutiloako etorbidea zenbaki gabe, 31192, Mutiloabeti, Nafarroa, Spain J. Šamaj (ed.), Endocytosis in Plants, DOI: 10.1007/978-3-642-32463-5_5, Springer-Verlag Berlin Heidelberg 2012 107