Table 2.
The similarity of chloroplasts and cyanobacteria turned out to be explained by different mechanisms.
| Apparent Similarity | Revealed Difference | Cyanobacteria | Chloroplasts | Reference |
|---|---|---|---|---|
| Chlorophylls and tetrapyrroles | Partially different biosynthesis pathway (PPO) 1 | HemJ (or HemY) | HemY | [143] |
| Galactolipids (MGDG and DGDG) 2 | Different biosynthesis pathway | MgdA- > MgdE- > DgdA | MGD1- > DGD1 | [50] |
| Peptidoglycan 3 | Different origins of biosynthesis enzymes | Cyanobacterial enzymes | Most enzymes originated from bacteria other than cyanobacteria | [77,78] |
| DNA replication | Different enzyme | PolIII | POP 4 | [108] |
| Transcription | Additional enzyme in chloroplast | Prokaryotic RNAP | Prokaryotic RNAP + NEP 5 | [110] |
| Division by binary fission | Additional components of division machinery in chloroplast | MinC, MinD, MinE, FtsZ, etc. | MinD, MinE, FtsZ, dynamin, etc (no MinC) | [111,112,113] |
| Oxygen producing photosynthesis | Partially different components of oxygen-evolving complex | PsbO, PsbU, PsbV | PsbO, PsbP, PsbQ (Red algae retain cyanobacteria-like system) | [144] |
1 PPO, protoporphyrinogen IX oxidase. 2 MGDG, monogalactosyl diacylglycerol; DGDG, digalactosyl diacylglycerol. 3 Peptidoglycan synthesis system is found in glaucophytes, some green algae, bryophytes, pteridophytes, and some gymnosperms. 4 POP, plant/protist organellar DNA polymerase. 5 RNAP, RNA polymerase; NEP, nuclear-encoded RNA polymerase.