Functional analysis of vesicular glutamate transporter in Chilo suppressalis: Implications for glutamate transport and pest management

Glutamate is the primary excitatory neurotransmitter in animals, and its storage and release are regulated by vesicular glutamate transporters (vGluTs) in mammals. However, the function of vGluTs in agricultural pests remains largely unexplored. In this study, we successfully cloned the full-length vGluT gene from the rice striped stem borer (RSB) Chilo suppressalis, a major rice pest. Multiple sequence alignment revealed that the amino acid sequence of CsvGluT shared more than 69.82 % similarity with other known insect vGluTs. In the phylogenetic tree, CsvGluT was clustered into a clade with the Asian corn borer Ostrinia furnacalis, which also belongs to Crambidae family. Spatial-temporal expression analysis showed that CsvGluT was highly expressed in the larval heads and abundant in the 1^st- and 2^nd-instar larvae, whose expression levels are more than three-fold higher than those in the 3^rd- to 6^th -instar larvae. Electrophysiological recordings indicated that CsvGluT exhibited functional properties like mammalian vGluTs under high concentrations of protons and chloride ions. Furthermore, inhibitors of mammalian vGluTs, including evans blue (EB) and 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS), significantly inhibited CsvGluT activity. RNA interference (RNAi)-mediated knockdown of CsvGluT significantly reduced the survival rate of RSB to 66 %, highlighting its physiological role and a potential target for RNAi-based RSB control. In summary, our findings elucidated the physiological function of vGluT in RSB and provide a theoretical foundation for advanced research in the development of RNAi-based transporter-targeted strategies for pest management.