Genome-Wide Identification of the Heterotrimeric G-Protein Gene Family and Its Transcriptional Response to Salt Stress in Foxtail Millet

Simple SummaryG proteins are ubiquitous in plants and play an important role in many biological functions such as plant growth and development, stress response and so on. However, their specific function in foxtail millet (Setaria italicaL.) is not clear. In this study, 12 G-protein gene family members were identified in foxtail millet and divided into four categories, and their whole-genome characteristics were analyzed. Transcriptome analysis showed that these members showed different expression patterns under salt-stress treatment at different times. This study increased the understanding of the G-protein gene family and provided valuable genetic resources for foxtail millet breeding.Heterotrimeric GTP-binding proteins, commonly known as G proteins, act as core molecular switches in plant signal transduction, governing multiple biological processes including plant growth, development, phytohormone signaling, and abiotic stress adaptation. In this study, a total of 12 G-protein-related genes were identified in foxtail millet, consisting of six Gα subunit-encoding genes, one Gβ subunit-encoding gene, and five Gγ subunit-encoding genes. Gene structure and conserved motif analyses showed that members classified into the same subunit clade possessed highly conserved exon–intron organization and motif distribution, indicating evolutionary structural conservation within each G-protein subfamily. PromoterCis-acting element analysis revealed that all G-protein family genes harbored light-responsive elements, as well as multiple regulatory elements associated with phytohormone signaling and abiotic stress responses. Transcriptome analysis showed that different G-protein genes exhibited distinct expression patterns under salt stress. Notably,SiαXLG2exhibited drastically induced expression upon salt stress, which serves as a pivotal candidate gene for salt-stress response in foxtail millet. Collectively, this study provides a systematic characterization of the G-protein gene family and offers candidate gene resources for further elucidating G-protein-mediated salt-stress regulatory mechanisms in foxtail millet.