Efficient prime editors for heritable multiplex precision genome editing in soybean

Prime editing (PE) is limited by low efficiency in dicot plants. Here we develop an optimized PE system for soybean, GmPEplus, by deleting the RNase H domain, introducing a V223A substitution within the reverse transcriptase domain, inserting a viral nucleocapsid protein between Cas9 and reverse transcriptase, and co-expressing a dominant-negative engineered allele of the endogenous GmMLH1. GmPEplus achieves editing efficiencies of up to 81.3% in stable transgenic lines. Subsequently, we show that nicking the non-edited strand using an additional sgRNA via the tRNA processing system enhances editing efficiency, and that optimizing its expression with an independent AtU6 cassette boosts efficiency by 13.1-fold. Importantly, a Csy4-mediated multiplex PE system (CMMPE) is established for simultaneous editing of 2-12 genes in soybean hairy roots and up to 3 genes in stable transgenic lines. GmPEplus and CMMPE offer powerful, versatile tools for precise, multiplex and heritable genome editing in soybean breeding.