AP2/ERF Transcription Factors S tRAP2.7a/b Modulate trans -Zeatin Biosynthesis and StSP6A Expression to Facilitate Stolon and Tuber Formation in Potato

The tuber is the main edible and economic organ of potato ( Solanum tuberosum L.). However, the molecular mechanisms underlying tuberization, particularly the crosstalk of phytohormones and transcription factors, remain inadequately understood. In this study, we identified two AP2/ERF transcription factors, StRAP2.7a and StRAP2.7b, which are highly expressed in stolons and upregulated with swelling. Overexpression of StRAP2.7a/b significantly increased the number of stolons and tubers, ultimately enhancing yield. Integrated RNA-seq and DAP-seq analyses revealed that StRAP2.7a/b modulates the expression of multiple trans -zeatin (tZ) biosynthesis genes and tuberization-regulatory genes. It was observed that StRAP2.7a/b promotes tZ accumulation in stolons while repressing StBRC1A/B expression, thereby inducing stolon and tuber formation. Additionally, molecular dissection demonstrated that StRAP2.7a/b directly binds to and activates the promoter of StSP6A, which is finely modulated by its interacting protein StCOL1. These findings advance our understanding of the mechanisms of tuberization and provide valuable genetic resources for breeding high-yielding potato cultivars.