From Neurotransmitter to Plant Protector: The Intricate World of GABA Signaling and its Diverse Functions in Stress Mitigation

Gamma-aminobutyric acid (GABA) is a non-protein amino acid and has been thoroughly studied in animals, where it works as a neurotransmitter. In plants, GABA was found to be a signaling molecule after the discovery of its binding sites. GABA metabolism takes place through the GABA shunt. It occurs in mitochondria and bypasses two steps of the tricarboxylic acid (TCA) cycle. It is also produced via proline and polyamine metabolic pathways. Both abiotic and biotic stress conditions affect plant’s growth and development. These stresses impact respiration and energy production in mitochondria, resulting in the elevated production of reactive oxygen species (ROS), which ultimately leads to cell death. The synthesis of GABA aids in the restoration of respiratory processes and energy production. Its accumulation is observed during plant stress conditions. In stress conditions, GABA concentration increases which raises the tolerance level of plants. It mitigates ROS formation, improves photosynthetic machinery, regulates the opening of stomata, and activates antioxidant enzymes. The transport of GABA is crucial for its functioning throughout plants, making it important to understand its cell and organelle transport. This review describes the biosynthesis, distribution, transport, and signaling roles of GABA, and also highlights the management aspects of the GABA shunt pathway for ROS production and in the defense mechanism of plants.