Molecular propensity and stress tolerance of dehydrins from desert plants

Dehydrins (DHNs) are hydrophilic proteins that accumulate in plant vegetative tissues in response to abiotic stress and during the late stages of seed development. To investigate the genetic basis of stress tolerance in desert plants, full-length cDNA sequences encoding DHN proteins were isolated from three desert plant species including Prosopis cineraria (PcDHN1), Citrullus colocynthis (CcDHN1), and Phoenix dactylifera (PdDHN1 and PdDHN2). This study examined the structural characteristics and potential functional roles of these DHNs in relation to the abiotic stress adaptation of desert plants. Due to their evolution in arid environments, these desert plant DHNs showed unique structural adaptations and functional stability under severe abiotic stress conditions. The sequence analysis identified PcDHN1 and CcDHN1 genes as encoding for Y₂SK₂- and Y₃SK₂-type DHNs, respectively, while PdDHN1 and PdDHN2 for FSK₃-type DHNs. All four proteins demonstrated strong hydrophilicity, with grand average of hydropathy (GRAVY) scores of less than 0, indicating their water-binding ability under dehydration stress. Structural modelling predicted extensive disordered regions, with random coils and short α-helix as the major structural features. Gene Ontology (GO) analysis suggested that these DHNs may play key roles in cellular regulation, stress response, and metabolic processes. Functional characterization through heterologous expression in yeast knockout mutants (Cdc25 and AXT3K strains) showed a significant enhancement in heat and salinity stress tolerance. AXT3K yeast cells expressing DHNs exhibited a substantial accumulation of K⁺ over Na⁺ in saline conditions, resulting in a four-fold increase in the K⁺/Na⁺ ratio. Enzymatic assays demonstrated that the DHNs effectively prevented the inactivation of lactate dehydrogenase (LDH) under heat stress, dehydration-rehydration, and freeze-thaw cycles, reducing LDH aggregation by 20% to 70%. These DHNs can have a larger ability for osmoprotection and protein stabilization compared to DHNs from non-desert plant species, due to their naturally evolved mechanisms for overcoming extreme abiotic stresses. Thus, our study specifies the potential of desert plant DHNs to enhance abiotic stress tolerance, particularly for developing tolerant crops and stabilizing enzymes under different constraints of reactional processes.