Genome-Wide Identification and Characterization of the VQ Motif-Containing Gene Family Based on Their Evolution and Expression Analysis under Abiotic Stress and Hormone Treatments in Foxtail Millet (Setaria italica L.)

Valine–glutamine (VQ) motif-containing proteins are transcriptional regulatory cofactors that play critical roles in plant growth and response to biotic and abiotic stresses. However, information on the VQ gene family in foxtail millet (Setaria italica L.) is currently limited. In this study, a total of 32 SiVQ genes were identified in foxtail millet and classified into seven groups (I–VII), based on the constructed phylogenetic relationships; the protein-conserved motif showed high similarity within each group. Gene structure analysis showed that most SiVQs had no introns. Whole-genome duplication analysis revealed that segmental duplications contributed to the expansion of the SiVQ gene family. The cis-element analysis demonstrated that growth and development, stress response, and hormone-response-related cis-elements were all widely distributed in the promoters of the SiVQs. Gene expression analysis demonstrated that the expression of most SiVQ genes was induced by abiotic stress and phytohormone treatments, and seven SiVQ genes showed significant upregulation under both abiotic stress and phytohormone treatments. A potential interaction network between SiVQs and SiWRKYs was predicted. This research provides a basis to further investigate the molecular function of VQs in plant growth and abiotic stress responses.