title: Salinity alters snakeskin and mesh transcript abundance and permeability in midgut and Malpighian tubules of larval mosquito, Aedes aegypti.
abstract: This study examined the distribution and localization of the septate junction (SJ) proteins snakeskin (Ssk) and mesh in osmoregulatory organs of larval mosquito (Aedes aegypti), as well as their response to altered environmental salt levels. Ssk and mesh transcripts and immunoreactivity were detected in tissues of endodermal origin such as the midgut and Malpighian tubules of A. aegypti larvae, but not in ectodermally derived hindgut and anal papillae. Immunolocalization of Ssk and mesh in the midgut and Malpighian tubules indicated that both proteins are concentrated at regions of cell-cell contact between epithelial cells. Transcript abundance of ssk and mesh was higher in the midgut and Malpighian tubules of brackish water (BW, 30% SW) reared A. aegypti larvae when compared with freshwater (FW) reared animals. Therefore, [3H]polyethylene glycol (MW 400Da, PEG-400) flux was examined across isolated midgut and Malpighian tubule preparations as a measure of their paracellular permeability. It was found that PEG-400 flux was greater across the midgut of BW versus FW larvae while the Malpighian tubules of BW-reared larvae had reduced PEG-400 permeability in conjunction with increased Cl-secretion compared to FW animals. Taken together, data suggest that Ssk and mesh are found in smooth SJs (sSJs) of larval A. aegypti and that their abundance alters in association with changes in epithelial permeability when larvae reside in water of differing salt content. This latter observation suggests that Ssk and mesh play a role in the homeostatic control of salt and water balance in larval A. aegypti.
authors.affiliation: Department of Biology, York University, Toronto, Ontario, Canada. Electronic address: artks@yorku.ca.
authors.forename: Sima
authors.initials: S
authors.lastname: Jonusaite
authors.affiliation: Department of Biology, York University, Toronto, Ontario, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Donini
authors.affiliation: Department of Biology, York University, Toronto, Ontario, Canada.
authors.forename: Scott P
authors.initials: SP
authors.lastname: Kelly
mesh_terms: D000064:Acclimatization / Q000235:genetics / Q000502:physiology; D000330:Aedes / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D004064:Digestive System / Q000378:metabolism; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D007814:Larva / Q000235:genetics / Q000378:metabolism; D008317:Malpighian Tubules / Q000378:metabolism; D008958:Models, Molecular; D064587:Osmoregulation / Q000235:genetics / Q000502:physiology; D010539:Permeability; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D054712:Salinity; D017386:Sequence Homology, Amino Acid
chemical_list: D019476:Insect Proteins; D012333:RNA, Messenger
keywords: Mesh; Midgut permeability; Mosquito; Osmoregulatory epithelia; Smooth septate junctions; Snakeskin