Table 1.

Summary of key features of DNA-modifying technologies that have been employed for removal of selectable marker genes from plants

System Name	Meganuclease	Site-specific recombinase	ZFN
Enzyme involved	Homing nucleases	Site-specific recombinases	Zinc-finger fused Fokl nuclease
System examples	l-Scel	Cre-lox, phiC31-att	Custom-designed ZFNs
Recognition sites	Specific DNA sequence	Specific DNA sequence	Any endorgenous targeted DNA sequence
Pre-inserted target sites	Needed [random insertion]	Needed [random insertion]	Not needed [locus specific]
Reaction mode	Induce DSB and repair mechanism	Site-specific recombination	Induce DSB and repair mechanism
Product	Not-conserved [through NHEJ repair]	Conserved	Not-conserved [through NHEJ repair]
Concerns of using this technology	Natural existing sites in genomes	Pseudo sites in genomes	Low affinity of ZFN to target DNA
Negative impacts from the concerns above	Genome fractionation	Chromosome rearrangement or deletion	Non-specific DSB induction at the non-specific sites