From experimental clues to theoretical modeling: Evolution associated with the membrane-takeover at an early stage of life
Fig 6
The decreased permeability caused by phospholipid content in the membrane could drive the emergence of other functions in the protocells.
For each of the two subfigures, the upper panel shows the trend of relevant protocells while the lower panel demonstrates the trend of relevant RNA species. The legends identical to those included in Fig 2 have the same meaning, and additional ones are as follows: Cnrgrnpr — protocells containing NR, GR and NPR; Cnrgrtr — protocells containing NR, GR and TR; npr — NPR; tr — TR. At step 1 × 103, an empty fatty-acid protocell is inoculated. At step 1 × 104, ten empty protocells are selected (arbitrarily, the same below), each of which is inoculated with one NR molecule, one GR molecule, and one control molecule. (a) NPR, i.e., a ribozyme using more fundamental raw materials, would not spread if the influence of phospholipid content on membrane permeability is not assumed (solid circles and solid lines; FPP and FPPW are set to 0 throughout the simulation), but would spread when this influence is considered (empty circles and dotted lines; at step 3 × 105, FPP and FPPW are turned up to 30 and 3 respectively). In both cases, at step 6 × 105, ten NR-GR protocells are selected, each of which is inoculated with one NPR molecule. (b) TR, an RNA species favoring the membrane transport, would not spread if the influence of phospholipid content on membrane permeability is not assumed (solid circles and solid lines; FPP and FPPW are set to 0 throughout the simulation), but would spread when this influence is considered (empty circles and dotted lines; at step 3 × 105, FPP and FPPW are turned up to 30 and 3 respectively). In both cases, at step 6 × 105, ten NR-GR protocells are selected, each of which is inoculated with one TR molecule. PNP = 5 × 10-6.