Aquaporins (AQPs) are membrane proteins that form water channels, allowing rapid movement of water across cell membranes. AQPs have been reported in species of all life kingdoms and in almost all tissues, but little is known about them in insects. Our purpose was to explore the occurrence of AQPs in the ovary of the phylogenetically basal insect Blattella germanica (L.) and to study their possible role in fluid homeostasis during oogenesis. We isolated an ovarian AQP from B. germanica (BgAQP) that has a deduced amino acid sequence showing six potential transmembrane domains, two NPA motifs and an ar/R constriction region, which are typical features of the AQP family. Phylogenetic analyses indicated that BgAQP belongs to the PRIP group of insect AQPs, previously suggested to be water specific. However, ectopic expression of BgAQP in Xenopus laevis oocytes demonstrated that this AQP transports water and modest amounts of urea, but not glycerol, which suggests that the PRIP group of insect AQPs may have heterogeneous solute preferences. BgAQP was shown to be highly expressed in the ovary, followed by the fat body and muscle tissues, but water stress did not significantly modify the ovarian expression levels. RNA interference (RNAi) reduced BgAQP mRNA levels in the ovary but the oocytes developed normally. The absence of an apparent ovarian phenotype after BgAQP RNAi suggests that other functionally redundant AQPs that were not silenced in our experiments might exist in the ovary of B. germanica.

Financial support for this work was provided by the Spanish Ministry of Science and Innovation [grant number BFU2008-00484 to M.-D.P., grant number CGL2008-03517/BOS to X.B., grant number AGL2010-15597 to J.C.]; and Generalitat de Catalunya [grant number 2005 SGR 00053]. Laboratorio/nInternacional de Cambio Global (LINC-Global) is gratefully acknowledged. A.H. received a pre-doctoral research grant (JAE-LINCG program) from Consejo Superior de Investigaciones Científicas (CSIC). F.C. was supported by a postdoctoral fellowship from Juan de la Cierva Programme (Spanish Ministry of Science and Innovation)