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PLoS One. 2017 Jul 17;12(7):e0181192. doi: 10.1371/journal.pone.0181192. eCollection 2017.

Analysis of aquaporins from the euryhaline barnacle Balanus improvisus reveals differential expression in response to changes in salinity.

Author information

1
Department of Marine Sciences, Lundberg laboratory, University of Gothenburg, Gothenburg, Sweden.
2
Department of Chemistry and Molecular Biology, Lundberg laboratory, University of Gothenburg, Gothenburg, Sweden.
3
Department of Marine Sciences, National Infrastructure of Bioinformatics (NBIS), Lundberg laboratory, University of Gothenburg, Gothenburg, Sweden.
4
Department of Molecular and Clinical Medicine, Wallenberg Laboratory, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
5
RISE Research Institute of Sweden, Section for Chemistry and Materials, Borås, Sweden.
6
Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden.
7
Department of Marine Sciences-Tjärnö, University of Gothenburg, Strömstad, Sweden.

Abstract

Barnacles are sessile macro-invertebrates, found along rocky shores in coastal areas worldwide. The euryhaline bay barnacle Balanus improvisus (Darwin, 1854) (= Amphibalanus improvisus) can tolerate a wide range of salinities, but the molecular mechanisms underlying the osmoregulatory capacity of this truly brackish species are not well understood. Aquaporins are pore-forming integral membrane proteins that facilitate transport of water, small solutes and ions through cellular membranes, and that have been shown to be important for osmoregulation in many organisms. The knowledge of the function of aquaporins in crustaceans is, however, limited and nothing is known about them in barnacles. We here present the repertoire of aquaporins from a thecostracan crustacean, the barnacle B. improvisus, based on genome and transcriptome sequencing. Our analyses reveal that B. improvisus contains eight genes for aquaporins. Phylogenetic analysis showed that they represented members of the classical water aquaporins (Aqp1, Aqp2), the aquaglyceroporins (Glp1, Glp2), the unorthodox aquaporin (Aqp12) and the arthropod-specific big brain aquaporin (Bib). Interestingly, we also found two big brain-like proteins (BibL1 and BibL2) constituting a new group of aquaporins not yet described in arthropods. In addition, we found that the two water-specific aquaporins were expressed as C-terminal splice variants. Heterologous expression of some of the aquaporins followed by functional characterization showed that Aqp1 transported water and Glp2 water and glycerol, agreeing with the predictions of substrate specificity based on 3D modeling and phylogeny. To investigate a possible role for the B. improvisus aquaporins in osmoregulation, mRNA expression changes in adult barnacles were analysed after long-term acclimation to different salinities. The most pronounced expression difference was seen for AQP1 with a substantial (>100-fold) decrease in the mantle tissue in low salinity (3 PSU) compared to high salinity (33 PSU). Our study provides a base for future mechanistic studies on the role of aquaporins in osmoregulation.

PMID:
28715506
PMCID:
PMC5513457
DOI:
10.1371/journal.pone.0181192
[Indexed for MEDLINE]
Free PMC Article

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