Fig. 5: Behavior of GUVs with area reservoirs provided by nanotubes.

a Series of (transient) shapes observed for a single GUV when the GFP concentration was increased from X = 0 nM to X = 5.3 nM over a period of about 30 min. Initially, nanotubes (I, white arrow) protruding from the spherical mother vesicle into the vesicle interior were stabilized by negative spontaneous curvature arising from the solution asymmetry between a 300 mM sucrose solution inside the vesicle and a 150 mM NaCl + 40 mM sucrose solution outside the vesicle. The addition of GFP to the exterior solution generated a less negative spontaneous curvature that transformed the in-tubes into in-buds (II) and eventually into out-buds (III, IV). The response of another GUV exposed to the same time-dependent GFP concentration is displayed in Supplementary Fig. 9. b Time-dependent shape evolution of a single GUV exposed to the constant GFP concentration X = 7.8 nM. At time t = 0 s, the GUV exhibits a short outward-pointing necklace consisting of two small spheres (white circles) that were successively released from the GUV via neck fission. The neck between the two small spheres was cleaved after about 19 s, the neck between the remaining bud and the mother vesicle after about 117 s. c Classification of stable GUV morphologies into three fractions as observed in two independent experiments: for each GFP concentration, we determined the fraction of shapes with inward-pointing membrane protrusions and total spontaneous curvature m < 0, prolate shapes with no visible protrusions and m ≃ 0, shapes with outward-pointing protrusions and m > 0 as illustrated by the three images on the right. All data displayed in the present figure were obtained for 1 mol% anchor-lipids. All scale bars: 5 μm. Source data (number of vesicles per condition) for panel c are provided in the Source Data file.