Heavy metal-induced differential gene expression of metallothionein in Javanese medaka, Oryzias javanicus.
ABSTRACT A metallothionein (MT) gene was isolated for the first time from Javanese medaka, Oryzias javanicus, which shows high adaptability from freshwater to seawater. The full-length cDNA of MT from O. javanicus (OjaMT) comprises 349 bp, excluding the poly(A)+ stretch, and codes for a total of 60 amino acids. The positions of cysteine residues are highly conserved. The pattern of OjaMT expression induced by six heavy metals was analyzed via real-time quantitative polymerase chain reaction (PCR). The level of hepatic OjaMT mRNA was increased in a dose-dependent manner by Ag, Cd, Cu, and Zn after 24 h of exposure. However, after Cr and Ni exposure, a significant decrease in OjaMT levels was observed. Cadmium-induced OjaMT expression was detectable in fishes as young as 3 months. After Cd exposure, OjaMT induction was prominent in intestine and liver and moderate in muscle and gill. OjaMT mRNA levels could represent a good biomarker for monitoring heavy metals in seawater.
Full-textDOI: · Available from: Taek-Kyun Lee, Jul 07, 2014
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ABSTRACT: We characterized the cytoskeletal beta-actin (-ACT) gene (actb) and its 5'-upstream regulatory region in the Javanese ricefish Oryzias javanicus. The gene and protein structures were deduced from amino acid sequences of the actb gene and conserved in the teleost lineage. The O. javanicus actb gene has common transcription factor binding motifs in its regulatory region found in teleostean orthologues. Following quantitative reverse transcription-PCR, actb gene transcripts were detected in all tissues examined; however, the basal expression levels were different. During early development, O. javanicus actb mRNA levels showed a gradual increase and peaked between late somitogenesis and the heartbeat stage. Microinjection of O. javanicus embryos with the actb gene promoter-driven red fluorescent protein (RFP) gene reporter vector showed a ubiquitous distribution of RFP signals, although most exhibited a mosaic pattern of transgene expression. A small number of microinjected embryos displayed a wide distribution of RFP signals over their entire body, which resembled the expression pattern of endogenous actb. Data from this study provide a basis to develop a transgenic system with ubiquitous expression of foreign genes in O. javanicus.12/2012; 15(4). DOI:10.5657/FAS.2012.0317
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ABSTRACT: White sturgeon (Acipenser transmontanus) are among the most sensitive species of fishes to Cu, Cd, and Zn, but there is no information about sensitivity of lake sturgeon (Acipenser fulvescens). To begin to elucidate molecular mechanism(s) of sensitivity of sturgeons to metals a cDNA encoding metallothionein (MT) was amplified from livers of white sturgeon (WS-MT) and lake sturgeon (LS-MT), and expression in response to Cu, Cd, or Zn was characterized in liver explants from each species. The primary structure of WS-MT and LS-MT contained 20 cysteine residues, which is the same as MTs of teleost fishes. However, the primary structure of WS-MT and LS-MT contained 63 amino acids, which is longer than any MT identified in teleost fishes. Abundance of transcripts of WS-MT in explants exposed to 0.3, 3, 30, or 100 μg/L of Cu was 1.7-, 1.7-, 2.1-, and 2.6-fold less than in controls, respectively. In contrast, abundances of transcripts of WS-MT were 3.3- and 2.4-fold greater in explants exposed to 30 μg/L of Cd and 1000 μg/L of Zn, respectively. Abundance of transcripts of LS-MT was not significantly different at any concentration of Cu, Cd, or Zn. It is not known if expression of MT is a critical mechanism underlying sensitivity of fishes to metals. However, if it is, results of this study suggest that sensitivity of sturgeons to exposure to Cu, Cd, and Zn might be a result of the relatively lesser maximal response of MT to metals. The study also suggests lake sturgeon might be more sensitive than white sturgeon to metals. Copyright © 2015. Published by Elsevier Inc.Comparative Biochemistry and Physiology Part C Toxicology & Pharmacology 03/2015; 171. DOI:10.1016/j.cbpc.2015.03.002 · 2.83 Impact Factor
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ABSTRACT: Southeast Asia is known as a center of biodiversity of the earth. As economic growth of this region is remarkable, conservation of biodiversity is a top priority issue. For this purpose, it is important to monitor the environmental condition in effective ways. We are trying to detect pollutants in coastal and estuary waters through the expression level of pollutant-responsive genes of rice fishes of the genus Oryzias, widely distributed in Asia. Japanese medaka O. latipes is a useful model because whole genome sequence is available. Javanese medaka O. javanicus and Indian medaka O. dancena, both of which are widely distributed in Southeast Asia and adaptable to seawater, are also potential models. One possible method for pollution monitoring is the use of transgenic fish bearing artificial gene construct containing the pollutant-responsive promoter and a reporter gene. For example, transgenic strains that can detect estrogen-like substances have already been established. It is also probable to detect pollutants by quantifying mRNA or proteins expressed from the pollutant-responsive gene. In any case, the most important point is to identify the gene that responds to specific pollutants. Comprehensive transcriptomic analyses are powerful tool for this purpose. Organotin-responsive genes are being screened at present.