AcMYB176-Regulated AcCHS5 Enhances Salt Tolerance in Areca catechu by Modulating Flavonoid Biosynthesis and Reactive Oxygen Species Scavenging

High-salinity stress induces severe oxidative damage in plants, leading to growth inhibition through cellular redox imbalance. Chalcone synthase (CHS), a pivotal enzyme in the flavonoid biosynthesis pathway, plays critical roles in plant stress adaptation. However, the molecular mechanisms underlying CHS-mediated salt tolerance remain uncharacterized in <i>Areca catechu</i> L., a tropical crop of high economic and ecological significance. Here, we systematically identified the <i>CHS</i> gene family in <i>A. catechu</i> and revealed tissue-specific and salt-stress-responsive expression patterns, with <i>AcCHS5</i> exhibiting the most pronounced induction under salinity. Transgenic <i>Arabidopsis</i> overexpressing <i>AcCHS5</i> displayed enhanced salt tolerance compared to wild-type plants, characterized by elevated activities of antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), increased flavonoid accumulation, and reduced reactive oxygen species (ROS) accumulation. Furthermore, we identified the transcription factor <i>AcMYB176</i> as a direct activator of <i>AcCHS5</i> through binding to its promoter. Our findings demonstrate that the <i>AcMYB176-AcCHS5</i> regulatory module enhances salt tolerance by orchestrating flavonoid biosynthesis and ROS scavenging. This study provides functional evidence of CHS-mediated salt adaptation in <i>A. catechu</i> and highlights its potential for improving stress resilience in tropical crops.