Table 2.
Promoters employed for facilitating synthetic biology in cyanobacteria and microalgae are summarized
| Sl. no. | Promoters usable in synthetic biology (functional elements) | Host experimented on | Remarks about application (expressed gene, output level, significance) | References |
|---|---|---|---|---|
| Promoters (metabolite induced) | ||||
| 1. | trp–lac from E. coli induced by IPTG (100 µM) | Synechococcus elongatus PCC 7942 | invA and glf genes from Zymomonas mobilis. Increase of 160- and 30-fold for fructose (160 µM) and glucose (30 µM) | [72] |
| 2. | A1lacO-1 from E. coli induced by IPTG (100 mM) | Synechocystis sp. PCC 6803 | EFE encoding gene from Pseudomonas syringae. Increase of eightfold (170 nL ethylene/mL h) | [152] |
| 3. | Trc from E. coli induced by IPTG (1 mM) | S. elongatus PCC 7942 | uidA gene from E. coli. 36-fold increase (340 nmol MU/min mg/protein) | [153] |
| 4. | tet from E. coli induced by aTc (103 ng/ml) | Synechocystis sp. strain ATCC27184 | eYFP gene. 10,000 relative fluorescence unit. 290-fold increase | [154] |
| 5. | (a) Ptrc induced by IPTG (b) Ptrc/PlacO1 |
S. elongatus PCC 7942 | (a) kviD, YqhD. Isobutanol (450 mg/L). Decarboxylation of KIV channeled the flux towards production of isobutanol. (b) kivd/alsS-ilvC-ilvD. Isobutyraldehyde (1100 mg/L). Decarboxylation of KIV channeled towards production of metabolite |
[37] |
| 6. | Ptrc/PLLacO1 induced by IPTG | S. elongatus PCC 7942 | ter/atoB, adhE2, crt, hbd. 1-butanol (14.5 mg/L). Metabolite produced through dark anaerobic conditions | [155] |
| Promoters (light inducible) | ||||
| 7. | psbA2 from Synechocystis sp. PCC6803 induced by 500 μmol photons/m2 s | Synechocystis sp. PCC 6803 | ispS gene from Pueraria montana 50 mg isoprene dry wt/day | [73] |
| 8. | psbA2 from Synechocystis sp. PCC 6803 induced by 50 μmol/m2 s | Synechocystis sp. PCC 6803 | hydA1 gene derived from Chlamydomonas reinhardtii 130 nmol H2 produced mg/Chl min | [156] |
| 9. | Endogenous CABII-1 that controls chla/b binding proteins of PSII, induced by changing light condition | Chlamydomonas reinhardtii | NIT1 nitrate reductase gene | [107] |
| Promoters (nutrient induced) | ||||
| 10. | nirA from Synechococcus elongates PCC 7942 induced/repressed by NO3−/NH4+ with concentration 17.6 mM each | Synechocystis sp. PCC 6803 | p-Hydroxyphenyl pyruvate dioxygenase gene. Increase of 25-fold (250 ng tocopherol mg/dry wt.) | [157] |
| 11. | nirA from Synechococcus elongates PCC 7942 induced/Repressed by NO3−/NH4+ with concentration 15.0 mM/3.75 mM | S. elongates PCC 7942 | cmpABCD. Increase of fivefold (260 nmol HCO3− mg/Chl) | [158] |
| 12. | NIT1 induced/repressed by NO3−/NH4+ | C. reinhardtii, Phaeodactylum tricornutum, Dunaliella salina, Chlorella vulgaris | NIT1 nitrate reductase gene switched on/off by NO3−/NH4+. Expression vector having NIT1 promoter is used widely as circuits on expression studies | [47, 104, 105] |
| Promoters (metal induced) | ||||
| 13. | Coat from Synechocystis sp. PCC 6803 induced by Co2+ (6 μM) | Synechocystis sp. PCC 6803 | EFE gene from Pseudomonas Syringae. 500-fold increase (48 nL ethylene/mL h) | [152] |
| 14. | petE from Synechocystis sp. PCC 6803 induced by Cu2+ (0.5 μM) | Synechocystis sp. PCC 6803 | EFE gene obtained from Pseudomonas syringae. fivefold increase (28 nL ethylene/mL h) | [152] |
| 15. | ziaA from Synechocystis sp. PCC 6803 induced by Zn2+ (3.5 μM) | Synechocystis sp. PCC 6803 | hydA1 gene derived from Chlamydomonas reinhardtii 109 nmol of H2 produced mg/Chl min | [156] |
| 16. | smt from Synechococcus elongates PCC 7002 induced by Zn2+ (2 μM) | Synechocystis sp. PCC 6803 | EFE gene obtained from Pseudomonas syringae twofold increase (2 nL ethylene/mL h) | [152] |
| 17. | isiAB Synechococcus sp. strain PCC 7002 repressed by Fe3+ (100 nM) | S. sp. strain PCC 7002 | luxAB gene derived from Vibrio harveyi. twofold increase | [159] |
| 18. | isiAB Synechocystis sp. PCC 6803 repressed by Fe3+ (30 μM) | Synechocystis sp. PCC 6803 | isiAB+gfp genes. 5000-fold increase | [74] |
| 19. | CYC6 endogenous promoter that controls cytochrome c6 repressed by Cu2+ | C. reinhardtii | Inducible expression of copper responsive element (CuRe) responsive to Cu2+ and by Co2+ by CYC6 | [160] |
| 20. | Synthetic promoter sap11 produced to resemble native cis-elements and its structure | C. reinhardtii | Synthesized to understand promoter structure and increase in nuclear gene expression. Synthetic sap11 drives expression better than best endogenous promoter chimeric hsp70/rbs2. A highly conserved DNA motif was isolated by sap11 that is important for promoter function | [89] |
| 21. | TPP riboswitch based on Thiamine pyrophosphate biosynthesis from THIC genes of Arabidopsis | C. reinhardtii | Inducible expression system depending on the presence of TPP. Conditional repression of rpoA or rps12 chloroplast genes influencing their transcription/translation | [161] |
| 22. | RNAi silencing | C. reinhardtii | A RNAi construct effectively silenced 20 LHC proteins. 290% higher light penetration, augmentation in photosynthetic yield, less vulnerable to photo-inhibition | [162] |
| 23. | Differential expression of rbcl mRNA maturation factor MRL1 | C. reinhardtii | MRL1 under a inducible promoter can be used to regulate Rubisco level for optimum utilisation of energy according to conditions like light and CO2 | [85] |
These promoters can be utilized to construct pathways and build artificial circuits having rational, controllable logical genetic units that can yield desired output under specific stimulus