Genome-wide identification, characterization, and expression analyses of the solute carrier 2 (SLC2) gene family in fall armyworm (Spodoptera frugiperda)

Abstract

The solute carrier 2 (SLC2) gene family, responsible for hexose and polyol transport, has not been fully characterized in Spodoptera frugiperda, a globally invasive pest. Among this family, the trehalose transporter (TRET) genes, the largest and most functionally important subfamily, contribute to energy homeostasis and stress adaptation in insects. Despite their importance, TRET genes’ role in insect responses to bioinsecticide exposure remains largely unknown. Therefore, this study aimed to identify and characterize SLC2 genes, from which TRET genes were validated under bioinsecticidal stress in S. frugiperda. A genome-wide identification of the SLC2 gene family in S. frugiperda was performed using bioinformatics approaches. Third-instar larvae were treated under controlled temperature and light conditions with the technical grade of Emamectin benzoate (EMB) and Spinosad (SPD), along with their solvent acetone (Ac) and negative control (NC). In parallel, field bioassays were conducted using the commercial formulations of both insecticides on second- and fourth-instar larvae. Gene expression levels of selected TRET genes were evaluated using qRT-PCR. A total of 86 putative SfruSLC2 members were identified and analyzed for their structural, functional, and physicochemical properties, confirming their stability as membrane-associated transporters. Laboratory treatments induced dose-dependent toxic symptoms, whereas field applications resulted in 100% mortality within 24 h. qRT-PCR results revealed significant upregulation of TRET genes, with EMB eliciting the highest expression, followed by SPD and Ac. EMB and Ac showed non-linear responses, while SPD induced a more linear pattern. This study provides the first genome-wide characterization of the SLC2 gene family in S. frugiperda and highlights TRET genes as key mediators of energy regulation under bioinsecticide and Ac stress. These findings contribute novel insights into the molecular response mechanisms of S. frugiperda and may support future strategies for sustainable pest control and resistance management.