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While each monomeric aquaporin can independently function as an individual water pore, they normally oligomerize as tetramers in the cell membrane forming a central pore, which in some cases can function as an ion channel (Agre et al., 1993, Gomes et al., 2009, Yool and Weinstein, 2002).Įukaryotic aquaporins are divided into four major grades, including the classical aquaporins, the aquaporin 8-type aquaamoniaporins, the aquaporin 11/aquaporin 12-type unorthodox channels, and the aquaglyceroporins (Glps) (Finn and Cerdà, 2015). Solute selectivity is determined by the constriction region at the extracellular side of the channel formed by an aromatic Arg (ar/R) selectivity filter (Beitz et al., 2006, Gonen and Walz, 2006, Jung et al., 1994). Loops B (cytoplasmic) and E (extracellular) both contain the signature Asn, Pro, Ala (NPA) motif, and these two loops fold back into the channel from opposite sides of the membrane to form a seventh “broken” half membrane helix with the NPA motif at the center of the channel (Agre et al., 1993, Finn and Cerdà, 2015 Sui et al., 2001 Törnroth-Horsefield et al., 2010, Zardoya, 2005). The amino- and carboxyl-termini are located on the cytoplasmic side of the membrane and each channel consists of two similar halves formed by a tandem repeat. Generally, aquaporins consist of six transmembrane (TM) alpha helices connected through five loops (A-E) in an “hourglass” form (Jung et al., 1994). Aquaporins are widely distributed in all kingdoms of life (Abascal et al., 2014, Finn and Cerdà, 2015) and play numerous essential physiological roles, particularly in regulating cell water balance. Our phylogenetic and functional data reveal that hemipteran insects lost the classical glp genes, but have compensated for this by duplicating the eglp genes early in their evolution to comprise at least three separate clades of glycerol transporters.Īquaporins belong to the major intrinsic protein family and function as bidirectional transport channels of water or other small solutes across biological membranes (Benga, 2009, Campbell et al., 2008, Murata et al., 2000, King et al., 2004, Gomes et al., 2009). Each BtAqp has unique transcript expression profiles, cellular localization, and/or substrate preference. B. tabaci has further expanded its repertoire of water channels through the expression of three BtDrip2 amino-terminal splice variants, while other hemipteran species express amino- or carboxyl-terminal isoforms of Drip, Prip, and Eglps. Here, we show that B. tabaci has eight aquaporins (BtAqps), of which seven belong to the classical aquaporin 4-related grade of channels, including Bib, Drip, Prip, and Eglps and one that belongs to the unorthodox grade of aquaporin 12-like channels. One superfamily of proteins involved in the maintenance of fluid homeostasis in many organisms includes the aquaporins, which are integral membrane channel proteins that aid in the rapid flux of water and other small solutes across biological membranes. This pest has evolved a number of adaptations to overcome physiological challenges, including 1) the ability to regulate osmotic stress between gut lumen and hemolymph after imbibing large quantities of a low nitrogen, sugar-rich liquid diet 2) the ability to avoid or prevent dehydration and desiccation, particularly during egg hatching and molting and 3) to be adapted for survival at elevated temperatures. The Middle East-Asia Minor 1 (MEAM1) whitefly, Bemisia tabaci (Gennadius) is an economically important pest of food, fiber, and ornamental crops.