Investigating the functions of glycosyl hydrolase family 1 in foxtail millet through an integrated genome-wide survey, expression profiling, and variation analysis

Glycoside hydrolase family 1 (GH1) comprises genes encoding β-glucosidases (BGLUs), which participate in various plant physiological and metabolic processes by catalysing the hydrolysis of glycosidic bonds and play crucial roles in plant responses to biotic and abiotic stresses. However, the BGLU genes in foxtail millet (Setaria italica) remain poorly characterized. Here, 35 BGLU proteins were identified in foxtail millet (SiBGLUs) and their sequence characteristics, phylogenetic relationships, responses to abiotic stress, and sequence variations were investigated within a natural population. The results revealed that the 35 SiBGLU proteins could be classified into seven distinct phylogenetic groups. Variations in sequence features and expression patterns among paralogous genes significantly contributed to the functional divergence of the GH1 family members. Notably, the strongly induced expression pattern of SiBGLU27 under stress suggested that it may be a key candidate gene for osmotic stress response, providing a clear direction for subsequent functional validation studies. Finally, by analysing sequence variations in SiBGLU genes across a natural population and conducting an association analysis with important agronomic and quality traits, we identified alleles and genes with significant contributions to these traits, which can be leveraged for breeding selection. In summary, this study provides a comprehensive framework for elucidating the functions of SiBGLU genes and offers a theoretical foundation for the use of BGLU genes to increase abiotic stress tolerance and improve key traits in foxtail millet breeding.