Dresden 2020 – scientific programme

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BP: Fachverband Biologische Physik

BP 14: Focus: Phase Separation in Biological Systems II (joint session BP/CPP)

BP 14.10: Talk

Tuesday, March 17, 2020, 12:30–12:45, ZEU 250

Protein storage vacuoles and autophagosomes form by similar physical mechanisms — •Roland L. Knorr — Max Planck Institute of Colloids and Interfaces, Potsdam, Germany — The University of Tokyo, Tokyo 113-0033, Japan — Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany

Proteins are components and nutrients essential for the growth and maintenance of the human body. The most important protein source worldwide are plants and the majority of plant protein consumed is packed in protein storage vacuoles (PSVs) of seeds in all major crops including wheat and soy. How highly fragmented PSVs storing protein derive from a single, vegetative vacuole functioning in protein degradation is little understood. Here, we investigate the mechanisms of PSV generation. We find in living embryos that vacuolar phase separation generates storage protein droplets with liquid-like properties. A physical model combined with reconstituted droplet-membrane interactions shows that partial wetting of proteinaceous droplets on membranes determines droplet engulfment by a process we call liquid scaffolding. We thus demonstrate that phase separation and engulfment are the mechanisms underlying the formation of physically separated droplets of storage proteins, which may be important to reprogram degradative vacuoles into storage vacuoles by restricting the access of vacuolar proteases to developing protein reservoirs. Further, we demonstrate that the autophagosomal sequestration of cytosolic droplets underlies similar physical principles.

References: Fujioka, Y; Alam, J.M.D.; Noshiro, D.; Mouri, K.; Ando, T.; Okada, Y.; May, A.I.; Knorr, R. L.; Suzuki, K.; Ohsumi, Y; Noda, N.N.; Nature, accepted. Knorr, R. L.*; Franzmann, T.; Feeney, M.; Kittelmann, M.; Frigerio, L.; Dimova, R.; Hyman, A. A.; Lipowsky, R.; submitted. Agudo-Canalejo, J.; Schultz, S.W.; Chino, H.; Migliano, S.; Saito, C.; Koyama-Honda, I.; Stenmark, H.; Brech, A.; May, A.I.; Mizushima, N.; Knorr, R. L.*; submitted.