Current Status of Herbicide-Tolerant Protein Research and Strategy for Development of Herbicide-Tolerant Tomato Using CRISPR-Cas9 System

The development of herbicide-tolerant plants provided a convenient farming method. The five most popular herbicides are glyphosate, sulfonylureas/imidazolinones, glufosinate, norflurasone and oxyfluorfen. These herbicides inhibit 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), acetohydroxyacid synthase (AHAS), glutamine synthetase (GS), Phytoene desaturase (PDS) and protoporphyrinogen oxidase (PPO), respectively. Inhibition of EPSPS and AHAS reduces the biosynthesis of phenolic and branched amino acids, respectively, and inhibition of GS and PDS enhances the production of reactive oxygen species and induces plant necrosis. Inhibition of PPO decreases chlorophyll biosynthesis and inhibits plant photosynthesis. These herbicides induce plant death by interacting with their target proteins therefore the development of herbicide resistant plants is based on the discovery of mutant proteins insensi-tive to these herbicides. We reviewed the development of herbicide-tolerant plants and derived target amino acids for the production of herbicide-tolerant proteins using the CRISPR/Cas9 system in tomatoes.