Trehalose: A Multifunctional Sugar and Its Metabolites Are Biotechnological Targets for Crop Salinity Tolerance Under Saline Conditions

Salinity stress is an abiotic threat that affects crop growth, development, and productivity, placing a heavy burden on global agriculture. Therefore, researchers must thoroughly understand the various mechanisms by which crops tolerate salinity. This knowledge enables biotechnological strategies to enhance crop resilience and yield, helping to secure sustainable food supplies for the growing world population. Several organic osmolytes greatly influence how crop plants respond to salinity stress. Trehalose is one such osmolyte that has gained increasing attention because it effectively improves crop salinity response and tolerance by influencing physiological, biochemical, and signaling processes. Beyond trehalose itself, its metabolite trehalose-6-phosphate (T6P), along with key biosynthetic enzymes such as trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP), is vital for helping crops adapt to salinity, especially when applied externally or via genetic modifications. Trehalose performs multiple roles: it acts as a cell hydration agent, an antioxidant, a gene regulator, a source of energy and carbon, a precursor for metabolic pathways, a signaling molecule, and a detoxifier of excess reactive oxygen species (ROS) in cells and organelles. This review carefully explores the structure of trehalose, its biosynthesis, protective molecular mechanisms, and the important functions of its metabolites in crop adaptation to salinity. Strategies focused on increasing trehalose levels and functions or boosting its metabolites are promising approaches for researchers aiming to enhance crop tolerance and yield in saline environments, which we highlight. We suggest that trehalose, its precursor, and the biosynthesis pathway play various roles under both normal and stressed conditions, potentially serving as biomarkers to assess crop tolerance and productivity under saline conditions. This review offers valuable insights into trehalose metabolism, paving the way for future engineering techniques to improve crop tolerance and yield in saline soils.