Beyond neurotransmission: dopamine as an emerging biotic and abiotic stress regulator in plants.

Dopamine (DA) is a catecholamine that plays a role in both animals and plants. Popularly known as a neurotransmitter hormone in animals involved in motor control and reward sensing, it also has a defense-related function in the plant kingdom. In plants, DA functions as a redox-active metabolite, a signalling regulator, and a metabolic modulator, rather than a classical neurotransmitter. Accumulating evidence demonstrates that DA enhances tolerance to diverse abiotic and biotic stresses, including drought, salinity, heavy metals, nutrient imbalance, temperature extremes, and pathogen attack, by stabilizing photosynthetic machinery, optimizing root architecture, improving water and nutrient use efficiency, and activating antioxidant and detoxification systems. Mechanistically, DA operates through coordinated regulation of reactive oxygen species (ROS) signalling, calcium-mediated secondary messenger cascades, transcription factor activation (WRKY, ERF, NAC), and reprogramming of nutrient and ion transporter networks. DA also exhibits extensive crosstalk with phytohormones, fine-tuning growth defence trade-offs in a species and stress-specific manner. Collectively, these findings position DA as a central signalling hub integrating redox balance, metabolic plasticity, and transcriptional control in plants. Understanding the conserved structure yet divergent biosynthesis and signalling logic of DA across kingdoms provides critical insights into its distinct modes of action and highlights its potential as a next-generation regulator for enhancing plant resilience under changing environmental conditions.