Fig. 2. (a) Schematic illustration of pioneering attempts to construct genetic circuits in artificial vesicles (dashed lines). (i) ADP is polymerized into poly(A) by polynucleotide phosphorylase (PNPase). (ii) Templated RNA replication by Qβ replicase. (iii) T7 polymerase-based transcription. (iv) Peptide/protein translation. (v) Hybrid bacteriophage-E. coli system by coupling the transcription procedure of bacteriophage and the translation procedure of E. coli. rsGFP, red-shifted green fluorescent protein. (vi) All-E. coli cell-free TX/TL system. eGFP, enhanced green fluorescent protein. (b) Schematic representation of Synells with a phospholipid bilayer membrane and its components. Synells membranes are permeable to theophylline (Theo) and arabinose (Ara), and are impermeable to IPTG and doxycycline (Dox). But when channel-forming proteins aHL (grey membrane pores) are present, IPTG and Dox can traverse the membrane through aHL channels. Synells contain programmed genetic circuits that can be triggered by these molecules. fLuc, firefly luciferase. rLuc, Renilla luciferase. (c) Different genetic circuits running within and between Synells. (i) Two genetic circuits working in independent protocells without crosstalk. (ii) Genetic circuits in two different protocells interacting in a cascading way. (iii) Genetic circuits running in parallel in separate protocells can be joined hierarchically after protocell fusion. Reproduced from ref. 40 with permission. Copyright 2016 Springer Nature.