|CAMPBELL, EWAN - Adelaide University
|YOOL, ANDREA - Adelaide University
Submitted to: Insect Biochemistry and Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2010
Publication Date: 3/1/2011
Citation: Mathew, L.G., Campbell, E.M., Yool, A.J., Fabrick, J.A. 2011. Identification and characterization of functional aquaporin water channel protein from alimentary tract of whitefly, Bemisia tabaci. Insect Biochemistry and Molecular Biology. 41(3):178-190.
Interpretive Summary: The whitefly, Bemisia tabaci, is a global insect pest of food, fiber, and ornamental crops. Whiteflies damage crops by feeding directly on plant sap or phloem, transmission of plant disease viruses, and by promoting growth of microbes on plant material due to the excretion of large volumes of high sugar content waste. Because whiteflies completely subsist on a liquid phloem diet, their digestive tracts reflect the unique adaptation to process relatively large volumes of fluid with high concentrations of sugar, which further imposes water stress within the gut. Like some other sap feeding insects, the B. tabaci gut contains a filter chamber, an unusual structural arrangement whereby the gut loops upon itself allowing contact between anterior and posterior portions, thereby providing an avenue for excess dietary water to be removed for excretion and concentration of nutrients. In this paper, we describe the identification and characterization of an aquaporin water channel protein (BtAQP1) from within the B. tabaci gut and filter chamber, where it functions to maintain osmotic water pressure and/or assist in the excretion of excess dietary water. These results reveal new information regarding the role of aquaporin in the digestive physiology of B. tabaci and point to its potential as a novel target for control.
Technical Abstract: Some hemipteran xylem and phloem feeding insects have evolved specialized alimentary structures or filter chambers that rapidly transport water for excretion or osmoregulation. In the whitefly, Bemisia tabaci, mass movement of water through opposing alimentary tract tissues within the filter chamber is likely facilitated by an aquaporin protein. B. tabaci aquaporin-1 (BtAQP1) possesses characteristic aquaporin topology and conserved pore-forming residues found in water-specific aquaporins. As predicted for an integral transmembrane protein, recombinant BtAQP1 expressed in cultured insect cells localized within the plasma membrane. BtAQP1 is primarily expressed in early instar nymphs and adults, where in adults it is localized in the filter chamber and hindgut. Xenopus oocytes expressing BtAQP1 were water permeable and mercury sensitive, both characteristics of classical water-specific aquaporins. These data support the hypothesis that BtAQP1 is a water transport protein within the specialized filter chamber of the alimentary tract and functions to translocate water across tissues for maintenance of osmotic pressure and/or excretion of excess dietary fluid.