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

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. Promoter Cis-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, SiαXLG2 exhibited 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.