MOLECULAR IDENTIFICATION AND RNAI OF THE AQUAPORIN GENE(S) FROM THE EGYPTIAN COTTON LEAFWORM, SPODOPTERA LITTORALIS

Abstract

Aquaporins (AQPs) are integral membrane proteins belong to the Major Intrinsic Proteins (MIP) superfamily identified in different tissues from all living organisms including mammals, plants, invertebrates and microorganisms. Aquaporins play crucial physiological roles in insects besides maintaining the appropriate water homeostasis. Therefore, they were suggested as good targets for insect control through RNAi. Only few AQPs were isolated and studied from terrestrial insects. In the present study, we report the cloning of partial cDNA sequences of AQP1 and AQP3 genes from Spodoptera littoralis. Our study revealed that AQP1 and AQP3 genes are expressed in all insect developmental stages (eggs, larval instars, pupae, and adult males and females), while AQP2 gene expression was detected in all insect stages except for eggs and adult females. Furthermore, AQP1, AQP2 and AQP3 gene expression was detected in tissues of the digestive and the excretory systems (foregut, midgut, hindgut and Malpighian tubules) of fourth, fifth and sixth larval instars. Gene expression of AQP1 and AQP3 was detected in the reproductive system of adult females and males, while AQP2 gene expression was detected in the reproductive system of adult males only. Silencing of AQP2 gene was more effective than silencing of AQP1 or AQP3 genes as it gave higher mortality ratio and more delayed adult emergence than silencing of AQP1 and AQP3 genes. The highest reduction in gene expression through RNAi was achieved for AQP2 gene compared to AQP1 and AQP3 genes. Consequently, we suggest that these AQP genes have critical role in maintaining water balance in Spodoptera