Membrane bending is a ubiquitous cellular process that is required for membrane traffic, cell motility, organelle biogenesis, and cell division. Proteins that bind to membranes using specific structural features, such as wedge-like amphipathic helices and crescent-shaped scaffolds, are thought to be the primary drivers of membrane bending. However, many membrane-binding proteins have substantial regions of intrinsic disorder which lack a stable three-dimensional structure. Interestingly, many of these disordered domains have recently been found to form networks stabilized by weak, multivalent contacts, leading to assembly of protein liquid phases on membrane surfaces. Here we ask how membrane-associated protein liquids impact membrane curvature. We find that protein phase separation on the surfaces of synthetic and cell-derived membrane vesicles creates a substantial compressive stress in the plane of the membrane. This stress drives the membrane to bend inward, creating protein-lined membrane tubules. A simple mechanical model of this process accurately predicts the experimentally measured relationship between the rigidity of the membrane and the diameter of the membrane tubules. Discovery of this mechanism, which may be relevant to a broad range of cellular protrusions, illustrates that membrane remodeling is not exclusive to structured scaffolds but can also be driven by the rapidly emerging class of liquid-like protein networks that assemble at membranes.

No abstract

Membrane bending is a ubiquitous cellular process that is required for membrane traffic, cell motility, organelle biogenesis, and cell division. Proteins that bind to membranes using specific structural features, such as wedge-like amphipathic helices and crescentshaped scaffolds, are thought to be the primary drivers of membrane bending. However, many membrane-binding proteins have substantial regions of intrinsic disorder, which lack a stable three-dimensional structure. Interestingly, many of these disordered domains have recently been found to form networks stabilized by weak, multi-valent contacts, leading to assembly of protein liquid phases on membrane surfaces. Here we ask how membrane-associated protein liquids impact membrane curvature. Using synthetic and cell-derived membrane vesicles, we find that liquid-liquid phase separation of membrane-associated disordered proteins creates a substantial compressive stress in the plane of the membrane. This stress drives the membrane to bend away from the protein layer, creating protein-lined membrane tubules. A simple mechanical model of this process accurately predicts the experimentally measured relationship between the rigidity of the membrane and the diameter of the membrane tubules. Discovery of this mechanism, which may be relevant to a broad range of membrane protrusions, illustrates that membrane remodeling is not exclusive to structured scaffolds, but can also be driven by the rapidly emerging class of liquid-like protein networks that assemble at membranes.

Although Agrobacterium-mediated transformation protocols for many economically important plant species have been well established, protocol for a number of flowering plants including Anthurium andraeanum remains challenging. In this study, we report success in generating transgenic Anthurium andraeanum cv Arizona using Agrobacterium GV3101 strain harboring a binary vector carrying gfp as a reporter gene. The possibility of facilitating the screening process for transgenic plants expressing functional proteins using gfp marker was explored. In order to realize high transformation efficiency, different explant sources including undifferentiated callus pieces and petioles were compared for their regeneration efficiency and susceptibility to Agrobacterium-mediated transformation. We also optimized the concentration of AS added to co-cultivation media. Genomic PCR revealed that 11 of the 22 resistant plantlets regenerated on selective medium were successfully transformed. Green fluorescence was observed using a fluorescence microscope in 7 of the 11 PCR-positive plants, indicating GFP was expressed stably in the transformed Anthurium andraeanum. The highest transformation efficiency obtained in this study was 1.71% (percentage of explants with transgenic shoots in total explants) when callus explants were used as starting material and 125 μmol l -1 AS was added during the co-cultivation process.

In all molecular simulations of periodic ordered morphologies (such as those formed by block copolymers), the periodic boundary conditions (PBCs) of the simulation box usually do not match the bulk...