Characterization, expression analysis and RNAi-mediated knockdown of two aquaporin genes in the cotton leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae)

Abstract

Aquaporins (AQPs) are integral membrane proteins that can transport water and small molecules across cell membranes in organisms. In a previous report, we identified an AQP (SlAQP1) gene of the cotton leafworm, Spodoptera littoralis. In the current study, we identify and characterize two more SlAQP genes and their developmental and tissues expression. Predicted amino acid sequence and phylogenetic analysis revealed that SlAQP2 is a glycerol channel belonging to the insect specific Eglp subfamily, whereas SlAQP3 is a water specific channel belonging to the Prip subfamily. SlAQP2 expression was detected mainly in the first four larval instars and adult males, whereas SlAQP3 was detected in all developmental stages. SlAQP2 gene expression was mainly detected in larval midgut and Malpighian tubules and adult male testes, whereas SlAQP3 was detected in all the tissues tested. RNAi mediated knockdown of each gene separately resulted in deleterious effects including larval and pupal mortality, deformed pupae and adults and prolonged development. Results were confirmed using qRT-PCR, which revealed downregulation of both genes after injection of larvae with gene specific dsRNA. Our results confirm the presence of Prip and Eglp AQPs in S. littoralis and suggest that Eglp has a role in male reproductive ability.