The STEME system: a novel tool for directed evolution in vivo

Directed evolution can be rapidly applied for engineering proteins, studying gene functions, and obtaining mutants with important agronomic traits. Recently, Caixia Gao and Jiayang Li's team from the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, worked together to engineer novel saturated targeted endogenous mutagenesis editors (STEMEs), realizing in vivo directed evolution and function selection in plants. This system integrated the existing two single-base editing techniques, successfully induced C:G>T:A and A:T>G:C double-base editing in plants, and artificially evolved into herbicide-resistant rice through targeting the OsACC carboxyltransferase domain coding sequence. This new method of gene directed evolution in vivo displays great application potential in important agronomic trait screening and plant functional gene researches. Here we introduce the composition, editing efficiency, and application principle of the STEME system, and compare it with the existing directed evolution methods, so as to provide a reference for accelerating the innovation of crop germplasm resources.