Melatonin plays a central role in plant growth regulation and abiotic stress tolerance, and serotonin N -acetyltransferase (SNAT) catalyzes a key step in its biosynthetic pathway. SNAT proteins belong to the GCN5-related N -acetyltransferase (GNAT) superfamily, members of which share conserved acetyltransferase domains but may differ in substrate specificity. Despite the exceptional stress resilience of foxtail millet ( Setaria italica ), a genome-wide analysis of SNAT-related GNAT genes in this species has not yet been reported. In this study, we performed a comprehensive identification and characterization of the SNAT-like GNAT acetyltransferase gene family in foxtail millet. A total of 29 SiSNAT / GNAT genes were identified and unevenly distributed across all nine chromosomes. Phylogenetic analysis revealed clustering with homologs from other monocots, indicating lineage-specific expansion. Gene structure and motif analyses showed substantial diversity, ranging from intronless genes to complex multi-exon members, while all proteins possessed conserved GNAT acetyltransferase domains. Promoter analysis revealed abundant stress- and hormone-responsive cis-elements, suggesting transcriptional regulation under multiple abiotic stresses. Expression profiling by qRT-PCR demonstrated that several SiSNAT genes were strongly induced under drought, salinity, heat, and cold treatments, indicating potential roles in stress adaptation. Protein interaction and functional enrichment analyses linked SiSNAT proteins to acetylation-related metabolic pathways, including tryptophan metabolism associated with melatonin biosynthesis. This study provides the first genome-wide overview of SNAT-like GNAT genes in foxtail millet and establishes a foundation for understanding their roles in melatonin-associated stress tolerance in cereals.
Supriya et al. (Mon,) studied this question.