Identification and Functional Analysis of the First Aquaporin from Striped Stem Borer, Chilo suppressalis

Ming-Xing Lu, Dan-Dan Pan, Jing Xu, Yang Liu, Gui-Rong Wang, Yu-Zhou Du

Aquaporins are integral membrane proteins some of which form high capacity water-selective channels, promoting water permeation across cell membranes. In this study, we isolated the aquaporin transcript (CsDrip1) ofChilo suppressalis, one of the important rice pests.CsDrip1 included two variants,CsDrip1_v1 andCsDrip1_v2. AlthoughCsDrip1_v2 sequence (>409 bp) was longer thanCsDrip1_v1, they possessed the same open reading frame (ORF). Protein structure and topology ofCsDrip1 was analyzed using a predicted model, and the results demonstrated the conserved properties of insect water-specific aquaporins, including 6 transmembrane domains, 2 NPA motifs, ar/R constriction region (Phe69, His194, Ser203, and Arg209) and the C-terminal peptide sequence ending in "SYDF." Our data revealed that theXenopusoocytes expressingCsDrip1 indicatedCsDrip1 could transport water instead of glycerol, trehalose and urea. Further, the transcript ofCsDrip1 expressed ubiquitously but differentially in different tissues or organs and developmental stages ofC. suppressalis. CsDrip1 mRNA exhibited the highest level of expression within hindgut and the third instar larvae. Regardless of pupae and adults, there were significantly different expression levels ofCsDrip1 gene between male and female. Different from at low temperature, the transcript ofCsDrip1 in larvae exposed to high temperature was increased significantly. Moreover, the mRNA levels ofCsDrip1 in the third instar larvae, the fifth instar larvae, pupae (male and female), and adults (male and female) under different humidities were investigated. However, the mRNA levels ofCsDrip1 of only female and male adults were changed remarkably. In conclusions,CsDrip1 plays important roles in maintaining water homeostasis in this important rice pest.