Molecular characterization of an arginine kinase from Lasioderma serricorne and the effect of gene silencing on larval survival

Arginine kinase (AK) is a phosphagen kinase that is critical for energy metabolism in insects, such as the cigarette beetle, Lasioderma serricorne, which is an important pest species of stored products. Nevertheless, the AK gene has not been identified in L. serricorne. Accordingly, this study describes the identification and characterization of the AK gene in L. serricorne (designated LsAK). The cDNA sequence of LsAK contains an open reading frame of 1068-bp and encodes the LsAK protein consisting of 355 amino-acid residues. LsAK possesses features typical of other insect AKs and shares a high amino-acid identity and a close phylogenetic relationship with orthologs from other coleopteran species. The transcripts of LsAK mRNA can be detected at all developmental stages, and the highest levels of LsAK transcription are observed at the fourth-instar larval stages. Recombinant LsAK protein expressed in Escherichia coli displayed activity to convert L-arginine to phosphoarginine. Oral delivery of double-stranded RNA significantly reduces the LsAK mRNA level and AK activity, resulting in a noticeably decreased survival rate in L. serricorne larvae. The findings of this study indicate that the LsAK gene is essential for larval survival of L. serricorne and could be a viable target for RNA-interference-based pest management.