Unravelling the nanoparticle-mediated regulation of phytohormone biosynthesis and signalling

Nanoparticles (NPs) have emerged as key plant growth and development regulators that influence various physiological and biochemical processes, including hormone regulation, stress response, and antioxidant defense. Similarly, phytohormones are essential for controlling cell division, differentiation, and organ development and are significantly impacted by NPs. NPs interact with plant systems by altering transcription-associated genes in phytohormone synthesis and signalling networks, thus modulating plant adaptations to biotic and abiotic challenges. This review explores the role of NPs in directing the biosynthesis of phytohormones and their involvement in the complex signalling networks that govern plant development and stress adaptation. The extensive role of NPs in hormone synthesis and accumulation and their involvement in signalling networks, have been reported recently. However, the direct association of NP-assisted phytohormone regulation has not yet been revealed. Thus, this review explores new research aimed at understanding how NPs affect phytohormone interference, biosynthesis mechanisms, signalling networks, and phytohormone-mediated modulation and interactions. Furthermore, we examined how NPs affect the biosynthesis and signalling pathways of ethylene, brassinosteriods, auxin, gibberellin, cytokinin, abscisic acid, ethylene, salicylic acid, and jasmonic acid to highlight key areas for future research and identify existing gaps in the literature. Furthermore, the potential mechanisms and underlying factors responsible for the observed discrepancies in specific phytohormone responses are discussed. • Phytohormones play an important role in governing the growth and development in all stages of plant life, including protection against biotic and abiotic stresses. • Nanoparticles (NPs), at optimum concentration, reprogram phytohormone biosynthesis and signalling. • NPs can stimulate seed germination, support plant growth, and enhance yield in different plant varieties by phytohormone modulation. • NPs exposure at higher concentration shows inhibitory effects in the phytohormone signalling mechanism. • The exact mechanism behind NPs - Phytohormone interactions is still in the primary stage, which needs to be explored.