Table 1. Summary of compact transposon-encoded editors.
| Characteristics | Cas9 | TnpB and IscB | Fanzor | Plant genome editing |
| crRNA, CRISPR RNA; tracrRNA, transactivating CRISPR RNA; PAM, protospacer adjacent motif; DSB, double-strand break; aa, amino acid. | ||||
| Size | ~1,000–1,400 aa (e.g., SpCas9: 1,368 aa) | ~400–500 aa (TnpB); ~350–450 aa (IscB) |
~400–600 aa | Delivery advantage: easier packaging into size-limited vectors (e.g., AAV, plant viral vectors); suitable for multiplex editing |
| Guide RNA | crRNA + tracrRNA (or fused sgRNA) | Single ωRNA (simpler structure) | Single ωRNA (eukaryotic origin) | Simplified design: easier expression and optimization in plants |
| PAM specificity | Stringent (e.g., SpCas9: NGG) | Relaxed (e.g., TTN, NG) | Moderately relaxed (e.g., T-rich) |
Expanded targeting scope: enables editing of genomic regions previously inaccessible due to PAM constraints |
| Cleavage pattern | Blunt-ended DSB | Staggered DSB (5-nt overhang) | Staggered DSB | Potential for precise integration: staggered ends may facilitate homologous recombination or specific repair pathways |
| System origin | Bacterial CRISPR immune system | Prokaryotic transposon (IS200/IS605) | Eukaryotic transposon (first eukaryotic-derived programmable nuclease) | Eukaryotic compatibility (Fanzor): may reduce plant cytotoxicity and holds potential for organellar genome editing |
| Immunogenicity | High (bacterial origin; may trigger plant immune responses) | Potentially lower (still prokaryotic-derived) | Likely lowest (eukaryotic origin; more 'familiar' to plant cells) | Improved editing efficiency: reduced suppression by plant defense responses |