Fig. 5: The specific SBS can be employed to dynamically fine-tune gene expression.

a Sequence of SBS-A and schematic of the SBS-A testing system (pKD236-P_tac-SBS-A-GFP) in E. coli BL21. b E. coli BL21 with pET-28a-S1 (induced by IPTG) and acetyl-mimetic S1 (induced by arabinose). c Expression of GFP (relative fluorescence unit) in E. coli BL21 cultured in N^L or supplemented with nitrogen (N) at 10 h. The black line represents the RFU of GFP in E. coli BL21 cultured in N^L, the red line represents the RFU of GFP in E. coli BL21 after addition of nitrogen in N^L at 10 h. *P < 0.05, **P < 0.01, ***P < 0.001. Three replicates were made for each sample. d Expression of GFP in E. coli BL21 cultured in N or transferred to limited nitrogen (N^L) at 10 h. The red line represents the RFU of GFP in E. coli BL21 cultured in N, the black line represents the RFU of GFP in E. coli BL21 after transferring to N^L at 10 h. *P < 0.05, **P < 0.01, ***P < 0.001. Three replicates were made for each sample. e Expression of GFP in E. coli BL21 with pET-28a-S1-S1 (K411Q/K464Q) when cultured in LB medium. Arabinose was added to induce S1 (K411Q/K464Q) at 0 h, and IPTG was added to induce S1 at 10 h. The black line represents the RFU of GFP in E. coli BL21 with arabinose, the red line represents the RFU of GFP in E. coli BL21 after adding IPTG at 10 h. *P < 0.05, **P < 0.01, ***P < 0.001. Three replicates were made for each sample. f IPTG was added to induce S1 at 0 h, and Ara was added to induce S1 (K411Q/K464Q) at 10 h. The red line represents the RFU of GFP in E. coli BL21 with IPTG, the black line represents the RFU of GFP in E. coli BL21 after adding arabinose at 10 h. *P < 0.05, **P < 0.01, ***P < 0.001. Three replicates were made for each sample.