TOT3-AHA1 module: its role in fine-tuning stomatal responses.

Stomatal pores, controlled by surrounding guard cells, play a crucial role in balancing carbon dioxide (CO2) uptake and water loss in plants. Recent studies in Arabidopsis thaliana have identified the TARGET OF TEMPERATURE 3 (TOT3)-plasma membrane (PM) H+-ATPase (AHA1) module as a key player in stomatal movement, though its exact role in vascular plants is not yet fully understood. TOT3, a transcriptional regulator, influences the activity of AHA1, which regulates ion fluxes essential for stomatal opening. Under high-temperature conditions, TOT3 promotes stomatal opening, while OST1, a key regulator of drought-induced stomatal closure, inactivates TOT3 through phosphorylation. This phosphorylation serves as a molecular switch, adjusting stomatal aperture in response to heat and drought stress. Moreover, light may also impact stomatal movement via the TOT3-AHA1 interaction. This review explores the molecular mechanisms underlying the TOT3-AHA1 module, its integration with abscisic acid (ABA) signaling, and its role in plant adaptation to environmental stresses. Understanding this pathway could contribute to developing crops with enhanced water-use efficiency and resilience to abiotic stress.