PIN-FORMED Auxin Efflux Transporters in Abiotic Stress Adaptation: Mechanisms, Expression Dynamics, and Crop Improvement Potential.

Plants continuously encounter abiotic stresses such as drought, salinity, and temperature fluctuations that severely constrain their growth and productivity. Adaptation to such stress involves the dynamic regulation of developmental and physiological processes through phytohormone signaling networks, notably auxin. Among auxin transporters, the PIN-FORMED (PIN) family of efflux carriers plays a pivotal role in establishing and maintaining polar auxin transport (PAT), which is crucial for plant stress adaptation. Recent pieces of evidence highlight spatiotemporal regulation, subcellular trafficking, and transcriptional modulation of PIN genes in response to environmental stressors. However, the mechanism linking PIN dynamics to abiotic stress responses remains only partially understood. This review critically examines the molecular and physiological roles of PIN transporters under abiotic stress, focusing on their regulation, expression profiles across species, and experimental validations through overexpression or silencing. We also highlight current knowledge gaps and discuss the potential of PIN manipulation as a strategy for improvement of crop resilience under changing climate conditions using biotechnological tools, such as genome editing, crucial for developing sustainable agricultural practices.