Emerging Paradigms in Hormonal Regulation of Plant Secondary Metabolism: Integrative Mechanisms and Biotechnological Frontiers

Plant secondary metabolites are central to ecological adaptation, stress resilience, and their expanding applications in medicine, agriculture, and industry. Their biosynthesis is now understood as a highly dynamic process orchestrated by intricate hormonal signaling networks. Phytohormones such as jasmonic acid, abscisic acid, salicylic acid, strigolactone, melatonin, and polyamines modulate secondary metabolism through synergistic and antagonistic interactions, transcriptional reprogramming, and multilayered feedback regulation. Hormonal crosstalk operates in a species, organ, and environment-specific manner, further fine-tuned by lipid-derived signals, reactive oxygen species, and calcium fluxes. Epigenetic mechanisms, including DNA methylation and histone modifications, add an additional dimension of regulation, conferring both flexibility and stress-induced memory to metabolic responses. Recent breakthroughs in genome editing (e.g., CRISPR/Cas), synthetic biology, and integrative multi-omics have enabled precise engineering of hormonal pathways to enhance the yield and diversity of bioactive compounds. These advances open transformative opportunities for medicinal plant productivity, crop resilience, and industrial metabolite synthesis. By bridging molecular biology, plant physiology, and systems-level approaches, this review synthesizes current knowledge and delineates emerging paradigms in hormone-driven regulation of secondary metabolism, providing conceptual framework to accelerate future biotechnological innovations.