Unraveling neurotransmitter mediated signaling in horticultural plants under abiotic stress conditions

Abstract

Plants are consistently subjected to various abiotic stresses, including drought, salinity, temperature fluctuations, heavy metal exposure, and nutrient deficiencies, which considerably hinder their growth, productivity, and overall global food security. Beyond traditional phytohormones, mounting evidence emphasizes the crucial functions of evolutionarily conserved neurotransmitter-like substances such as melatonin, acetylcholine (ACh), dopamine, and γ-aminobutyric acid (GABA) in orchestrating plant responses to stress. These bioactive agents operate as versatile signaling molecules that harmonize redox balance, ion transport, metabolic control, and transcriptional adjustments in response to challenging environmental circumstances. Melatonin, initially discovered in the human pineal gland and subsequently in plants, serves as a powerful antioxidant while influencing mitogen-activated protein kinase (MAPK) pathways, hormonal interactions, and reactive oxygen species (ROS) signaling to bolster resilience against drought, salinity, chilling, heavy metals, and nutrient-related stress. Acetylcholine plays a role in regulating ion movement, membrane depolarization, and systemic signaling, thereby aiding in growth modulation and adaptive responses to stress. Dopamine, a catecholamine that originates from tyrosine, boosts antioxidant capabilities, preserves ion and hormonal equilibrium, and enhances photosynthetic efficiency in the face of drought, salinity, cold, and nutrient scarcity. In a similar vein, GABA, which is primarily produced through the GABA shunt pathway, connects carbon and nitrogen metabolism with stress signaling, facilitating osmotic adjustment, antioxidant protection, and metabolic stability. Together, these neurotransmitter-like compounds orchestrate physiological, biochemical, and molecular processes that strengthen plant resilience in horticultural crops. Gaining insights into their biosynthesis, signaling networks, and interactions with established hormonal and redox pathways opens new avenues for creating sustainable strategies aimed at improving crop performance in the face of evolving climatic conditions.