Research progress on the regulatory mechanisms of the PSY promoter

Carotenoids are essential pigments in the plant photosynthetic apparatus, functioning in light harvesting, photoprotection, and signal transduction, and serving as precursors of vital nutrients such as vitamin A. Phytoene synthase (PSY) is the first rate-limiting enzyme in the plant carotenoid biosynthetic pathway, and its transcriptional regulation primarily depends on cis-acting promoter elements, associated transcription factors, and epigenetic status. The PSY promoter region contains core cis-elements as well as multiple light-, hormone-, and stress-responsive elements, which collectively function as key regulatory sites governing spatiotemporal expression. This review systematically summarizes recent advances in PSY promoter regulation by plant hormones (e.g., abscisic acid, ethylene, jasmonic acid), environmental factors (light signaling, temperature, salinity, and drought), and epigenetic mechanisms (DNA methylation, histone modifications, and chromatin remodeling). In addition, the application of transgenic and biotechnological approaches to PSY promoter regulation is further summarized. Including promoter sequence engineering with precise editing of cis-elements and promoter-targeted CRISPR activation/interference (CRISPRa/i) for tunable transcriptional control. Emphasis is placed on how these signals are integrated at the promoter level. Deeper insights into these mechanisms will provide both theoretical foundations and practical strategies for enhancing carotenoid accumulation and stress tolerance in crops through molecular design.