Non-coding RNAs as central regulators of phytohormone signaling in plant abiotic stress responses.

Plants are continuously exposed to a wide range of abiotic stresses, including drought, salinity, temperature extremes, nutrient deficiency, and heavy metal toxicity, which severely constrain growth and productivity. To cope with these challenges, plants have evolved sophisticated regulatory networks involving phytohormones and non-coding RNAs (ncRNAs). This review provides a comprehensive overview of the biogenesis and functional roles of major ncRNA classes' microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) and their dynamic interplay with phytohormonal signaling pathways under stress conditions. We highlight how ncRNAs modulate key hormonal pathways, including abscisic acid, auxin, jasmonic acid, ethylene, and gibberellins, to fine-tune stress-responsive gene expression and maintain cellular homeostasis. Special emphasis is placed on nutrient stress and heavy metal toxicity, where ncRNA-mediated regulation influences ion transport, autophagy, reactive oxygen species detoxification, and metabolic reprogramming. Emerging evidence on circRNAs as miRNA sponges further reveals an additional regulatory layer linking developmental processes with stress adaptation. The review also integrates recent advances in high-throughput sequencing, multi-omics approaches, and bioinformatics tools that have enabled large-scale identification and functional annotation of stress-responsive ncRNAs. Furthermore, the application of artificial intelligence and machine learning models in predicting ncRNA target interactions and regulatory networks is discussed as a transformative approach in plant stress biology. Collectively, this synthesis provides a systems-level understanding of ncRNA-phytohormone cross-talk and underscores its potential in developing climate-resilient crops through advanced molecular and computational strategies.