Phytohormone networks in heavy metal stress and phytoremediation: linking transport physiology with transcriptomic and metabolomic reprogramming

Heavy metal (HM) contamination poses severe threats to agricultural productivity and ecosystem health, necessitating innovative phytoremediation strategies. Phytoremediation remains a dynamic and expanding research domain, and an updated overview of recent advances, particularly those linking hormonal regulation with transport physiology and multi-omics reprogramming, is urgently needed. The central aim of this review is therefore to delineate how phytohormone networks orchestrate plant responses to HM stress and translate those responses into improved phytoremediation outcomes. Specifically, we examine how major phytohormones, auxin, cytokinin, ethylene, abscisic acid (ABA), jasmonic acid (JA), salicylic acid (SA), brassinosteroids, and gibberellins, modulate metal uptake, translocation, sequestration, and tolerance. Multi-omics approaches have revealed that these hormones regulate metal transporter expression (NRAMP, HMA, ZIP, ABC families), coordinate antioxidant defense, and reprogram primary and specialized metabolism. Transcriptomic analyses identify hormone-responsive transcription factors (ERFs, WRKYs, MYBs) as master controllers of metal-stress gene networks, while metabolomic profiling highlights phytohormone-driven changes in phenylpropanoid biosynthesis, amino acid metabolism, and organic acid production. Systems-biology integration of these datasets uncovers extensive hormone-crosstalk networks that fine-tune metal accumulation patterns and underpin rational phytoremediation design through genetic engineering, exogenous hormone application, and targeted breeding. Critical knowledge gaps, including tissue-specific hormone dynamics, long-distance signalling mechanisms, and the translation of laboratory findings to field-scale remediation, are identified, providing a roadmap for developing climate-resilient, metal-tolerant crops and optimising phytoremediation technologies.