Rhesus glycoprotein gene expression in the mangrove killifish Kryptolebias marmoratus exposed to elevated environmental ammonia levels and air

C. Y C Hung, K. N T Tsui, J. M. Wilson, C. M. Nawata, C. M. Wood, P. A. Wright

Research output: Contribution to journalArticle

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Abstract

The mechanism(s) of ammonia excretion in the presence of elevated external ammonia are not well understood in fish. Recent studies in other organisms have revealed a new class of ammonia transporters, Rhesus glycoprotein genes (Rh genes), which may also play a role in ammonia excretion in fish. The first objective of this study was to clone and characterize Rh genes in a fish species with a relatively high tolerance to environmental ammonia, the mangrove killifish Kryptolebias marmoratus (formerly Rivulus marmoratus). We obtained full-length cDNAs of three Rh genes in K. marmoratus: RhBG (1736 bp), RhCG1 (1920 bp) and RhCG2 (2021 bp), which are highly homologous with other known Rh gene sequences. Hydropathy analysis revealed that all three Rh genes encode membrane proteins with 10-12 predicted transmembrane domains. RhBG, RhCG1 and RhCG2 are highly expressed in gill tissue, with RhBG also present in skin of K. marmoratus. Exposure to elevated environmental ammonia (2 mmol l-1 NH4HCO3) for 5 days resulted in a modest (+37%) increase in whole-body ammonia levels, whereas gill RhCG2 and skin RhCG1 mRNA levels were upregulated by 5.8- and 7.7-fold, respectively. RhBG mRNA levels were also increased in various tissues, with 3- to 7-fold increases in the liver and skeletal muscle. In a separate group of killifish exposed to air for 24 h, RhCG1 and RhCG2 mRNA levels were elevated by 4- to 6-fold in the skin. Thus, the multifold induction of Rh mRNA levels in excretory tissues (gills and skin) and internal tissues in response to conditions that perturb normal ammonia excretion suggests that RhBG, RhCG1 and RhCG2 may be involved in facilitating ammonia transport in this species. Furthermore, the findings support earlier studies demonstrating that the skin is an important site of ammonia excretion in K. marmoratus.

Original languageEnglish
Pages (from-to)2419-2429
Number of pages11
JournalJournal of Experimental Biology
Volume210
Issue number14
DOIs
StatePublished - Jul 1 2007

Fingerprint

Fundulidae
Ammonia
mangrove
gene expression
glycoproteins
Glycoproteins
ammonia
Air
Gene Expression
air
skin
skin (animal)
excretion
Skin
gene
gills
Messenger RNA
Fishes
Genes
fold

Keywords

  • Ammonia excretion
  • Ammonia transporter
  • Gills
  • Kryptolebias marmoratus
  • Skin

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Agricultural and Biological Sciences (miscellaneous)

Cite this

Rhesus glycoprotein gene expression in the mangrove killifish Kryptolebias marmoratus exposed to elevated environmental ammonia levels and air. / Hung, C. Y C; Tsui, K. N T; Wilson, J. M.; Nawata, C. M.; Wood, C. M.; Wright, P. A.

In: Journal of Experimental Biology, Vol. 210, No. 14, 01.07.2007, p. 2419-2429.

Research output: Contribution to journalArticle

Hung, C. Y C ; Tsui, K. N T ; Wilson, J. M. ; Nawata, C. M. ; Wood, C. M. ; Wright, P. A. / Rhesus glycoprotein gene expression in the mangrove killifish Kryptolebias marmoratus exposed to elevated environmental ammonia levels and air. In: Journal of Experimental Biology. 2007 ; Vol. 210, No. 14. pp. 2419-2429.
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