Identification and functional characterization of an ovarian aquaporin from the cockroachBlattella germanicaL. (Dictyoptera, Blattellidae)

Abstract

SUMMARYAquaporins (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. Supplementary material available online at

Molecular and functional characterization of Bemisia tabaci aquaporins reveals the water channel diversity of hemipteran insects

“…Aquaporins are indispensable water and solute channels needed to maintain homeostasis in living organisms. In insects, aquaporins relieve pressure imposed by osmotically imbalanced diets, remove excess fluids and excretions, maintain fluid homeostasis during oogenesis, stabilize membranes and enzymes for anhydrobiosis and cryoprotection, are involved in water movement in respiration, and prevent desiccation during molting and egg hatching (Campbell et al, 2008;Drake et al, 2010, Duchesne et al, 2003, Fabrick et al, 2014Goto et al, 2011Goto et al, , 2015Herraiz et al, 2011;Kikawada et al, 2008;Le Cahérec et al, 1997;Liu et al, 2011;Martini et al, 2004;Maruyama et al, 2015;Mathew et al, 2011;Nagae et al, 2013;Philip et al, 2011;Spring et al, 2009;Staniscuaski et al, 2013;Yi et al, 2011). Because of their major importance in these physiological processes, aquaporins may serve as potential targets for insect pest management, especially in phloem-feeding hemipterans where imbibition of large volumes of liquid diet is required to meet nutrient requirements (Douglas, 2006;Ibanez et al, 2014;Mathew et al, 2011;Shakesby et al, 2009;Tzin et al, 2015;Wallace et al, 2012).…”

“…In other insects, Prips have a variety of physiological functions. For example, Blattella germanica Prip is present in the adult ovary, fat body, and muscles, and plays a role in fluid homeostasis during oogenesis (Herraiz et al, 2011). The Bombyx mori Prip is found in the oocyte plasma membrane within ovaries and functions during oocyte growth (Maruyama et al, 2015).…”

RNA interference‐mediated functional characterization of aquaporin genes in Tribolium castaneum

“…However, only a very small fraction of insect aquaporins have been functionally characterized by sensitivity to mercuric ions, knockout (aquaporin-deficient) organisms and functional system assays (Kaufmann et al, 2005;Cohen, 2012;Tzin et al, 2015;Van Ekert et al, 2016). Insect Drips (Kaufmann et al, 2005;Raza et al, 2016;Shakesby et al, 2009;Tzin et al, 2015;Van Ekert et al, 2016), Prips (Kikawada et al, 2008;Herraiz et al, 2011;Tzin et al, 2015;Van Ekert et al, 2016) and Eglps (Van Ekert et al, 2016) have been confirmed to be involved in water permeability. Moreover, using in vivo RNA interference (RNAi; knockdown) techniques, inhibitory or modified effects have been documented in plant sap-sucking and blood-feeding insect species (Cohen, 2013;Jing et al, 2016;Van Ekert et al, 2016;Tsujimoto et al, 2017).…”

Comparative genomic analyses of transport proteins encoded within the red algae Chondrus crispus, Galdieria sulphuraria, and Cyanidioschyzon merolae11

“…The one C. merolae homologue most closely resembles aquaporin‐1 of Bemisia tabaci (Sweet potato whitefly; TC# 1.A.8.8.15) which has specificity for water and perhaps small neutral solutes such as urea (Herraiz et al. , Mathew et al. ).…”