*Article* **Genome-Wide Identification and Expression Profiling of Glutathione** *S***-Transferase Gene Family in Foxtail Millet (***Setaria italica* **L.)**

**Linlin Wang 1, Hongbo Fu 2, Juan Zhao 1, Jiagang Wang 3, Shuqi Dong 1, Xiangyang Yuan 1, Xiaorui Li 1,\* and Mingxun Chen 4,\***


**Abstract:** Glutathione *S*-transferases (GSTs) are a critical superfamily of multifunctional enzymes in plants. As a ligand or binding protein, GSTs regulate plant growth and development and detoxification. Foxtail millet (*Setaria italica* (L.) P. *Beauv*) could respond to abiotic stresses through a highly complex multi-gene regulatory network in which the GST family is also involved. However, *GST* genes have been scarcely studied in foxtail millet. Genome-wide identification and expression characteristics analysis of the foxtail millet GST gene family were conducted by biological information technology. The results showed that 73 *GST* genes (*SiGSTs*) were identified in the foxtail millet genome and were divided into seven classes. The chromosome localization results showed uneven distribution of *GSTs* on the seven chromosomes. There were 30 tandem duplication gene pairs belonging to 11 clusters. Only one pair of *SiGSTU1* and *SiGSTU23* were identified as fragment duplication genes. A total of ten conserved motifs were identified in the GST family of foxtail millet. The gene structure of *SiGSTs* is relatively conservative, but the number and length of exons of each gene are still different. The cis-acting elements in the promoter region of 73 *SiGST* genes showed that 94.5% of *SiGST* genes possessed defense and stress-responsive elements. The expression profiles of 37 *SiGST* genes covering 21 tissues suggested that most *SiGST* genes were expressed in multiple organs and were highly expressed in roots and leaves. By qPCR analysis, we found that 21 *SiGST* genes were responsive to abiotic stresses and abscisic acid (ABA). Taken together, this study provides a theoretical basis for identifying foxtail millet GST family information and improving their responses to different stresses.

**Keywords:** foxtail millet; glutathione *S*-transferase (GSTs); expression analysis; stress response
