Group 1 LEA Proteins in Durum Wheat: Evolution, Expression, and Roles in Abiotic Stress Tolerance

Group 1 LEA proteins are involved in embryo water dynamics during the maturation stage of seed development and contribute to desiccation stress protection in vegetative and embryonic tissues. Nevertheless, their roles in durum wheat remain largely unexplored. This study represents the first comprehensive survey of group 1 LEA proteins and their encoding genes in Triticum turgidum ssp. Durum (durum wheat). Eight group 1 LEA (TtEM1 to TtEM8) genes were identified in the durum wheat genome, which were named according to their chromosomal location. Analyses of the physiochemical characteristics and subcellular location revealed that all TtEM proteins exhibited a highly disordered structure (more than 90% of tendency of disorder) and were located in the nucleus. Evolutionary analysis between the durum wheat family and all other known group 1 LEA proteins from Arabidopsis thaliana, rice (Oryza sativa), barley (Hordeum vulgare), and barrel medic (Medicago truncatula) showed four phylogenetic groups; each group shares the same conserved motifs and gene structure. Interestingly, almost TtEM genes harbor cis-elements related to hormone regulation, stress response, and growth regulation, indicating their function in stress tolerance and developmental control. Subsequently, Expression analysis of two homoeologous genes, TtEM1 and TtEM4, demonstrated that the two genes exhibited distinct expression profiles across different tissues and in response to various stress treatments, suggesting that these genes may be involved in regulating growth, development, and stress adaptation in durum wheat. TtEM1 and TtEM4 purified proteins act as molecular chaperones and protect LDH activity against desiccation, cold, and heat treatments. Moreover, TtEM1 and TtEM4 genes were proved to enhance heat, cold, oxidative, and drought tolerance in yeast. These results clearly described the characteristics and the evolutionary dynamics of the EM gene family in wheat, and unveiled their role in wheat development and response to abiotic stress.