Researchers Perform Allele Exchange at EPSPS Locus in Cassava using CRISPR-Cas9

Effective weed control can protect yields of cassava (Manihot esculenta) storage roots from losses. Hence, a herbicide tolerant cultivar could benefit farmers. The team of Aaron W. Hummel from the University of Minnesota applied traditional transgenesis and gene editing to generate glyphosate tolerance in cassava.

The team aimed to replace the native promoter of cassava's 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene with a strong constitutive promoter. To achieve this, the team prepared a CRISPR-Cas9 endonuclease that targets the promoter of the EPSPS locus.

Two repair templates were also combined with the guide RNA and the Cas9 nuclease to help initiate homologous recombination and assist in the insertion of the new promoter. The team then introduced the best-performing allele of the EPSPS locus into the cassava genome while also performing a promoter swap. EPSPS-edited plants exhibited normal phenotypes and were tolerant to high doses of glyphosate.

This study demonstrates a strategy for creating glyphosate tolerance in crops as well as the potential of gene editing for further improvement of cassava.

For more information, read the article in Plant Biotechnology Journal.