An Anthocyanin-Based Visual Reporter System for Genetic Transformation and Genome Editing in Cassava

Cassava (Manihot esculenta Crantz) is a staple crop in tropical and subtropical regions, valued for its high starch content in roots. Effective genetic transformation and genome editing of cassava require efficient screening methods for transgenic and edited plants. In this study, a visual selection marker system using an R2R3-MYB transcription factor anthocyanin 1 gene (HbAN1, LOC110667474) from a rubber tree (Hevea brasiliensis Müll. Arg.) has been developed to facilitate the identification of transgenic cassava plants. Transgenic cassava lines expressing HbAN1 accumulated anthocyanins in their leaves, allowing for easy visual identification without the need for destructive assays or specialized equipment. Importantly, the accumulation of anthocyanins did not affect the regeneration or transformation efficiency of cassava. Additionally, the AR-CRISPR/Cas9-gRNA system with the HbAN1 gene as a marker produced MeCDD4 gene-edited cassava mutants with purple leaves, demonstrating successful editing. This anthocyanin-based visual reporter (AR) system will provide an effective tool for genetic transformation and genome editing in cassava.