Promoter editing for the genetic improvement of crops.

This article focuses on the application of promoter editing—genome editing of gene regulatory regions known as promoters—in crop plants to fine-tune gene expression for improved agronomic traits such as yield, stress tolerance, and quality. It reviews successful examples across various crops, including rice, maize, tomato, and citrus, where tools like CRISPR/Cas and TALENs have been used to create novel promoter alleles that alter gene expression patterns, leading to enhanced disease resistance, increased yield components, and modified quality traits. The article also discusses technical challenges in promoter editing, such as limited knowledge of functional cis-regulatory elements and the need for more precise and versatile genome editing tools, including gene targeting, base editing, and prime editing. Additionally, it highlights future directions involving editing of alternative regulatory elements like untranslated regions and upstream open reading frames (uORFs), as well as targeted modifications of epigenetic marks, to broaden the scope and efficacy of genetic improvement in crops.