Heavy metal-induced differential gene expression of metallothionein in Javanese medaka, Oryzias javanicus.

Southern Coastal Environment Research Division, Korea Ocean Research and Development Institute, Geoje, 656-830, Korea.
Marine Biotechnology (Impact Factor: 3.15). 01/2006; 8(6):654-62. DOI: 10.1007/s10126-006-6046-0
Source: PubMed

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.

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    ABSTRACT: Heavy metal, such as cadmium (Cd), lead (Pb) and copper (Cu) poses serious toxin to aquatic organisms. These exogenous materials affect biological processes including physiology, biochemistry and development. Metallothionein (MT), one of the metal-regulated genes, participates in regulating essential and detoxifying non-essential metals in living animals. In this study, MT EST in rare minnow (Gobiocypris rarus) (GrMT) was obtained from the cDNA subtraction library and the GrMT cDNA was firstly cloned by RACE with a sequence of 379 bp, which can code 60 amino acids. After Cd exposure, the GrMT expression levels dramatically changed in liver, spleen, gill, kidney, intestine, but moderately in muscle. Significantly positive relationships were found between Cd dosages and MT expression levels in liver. And there distinction existed at the GrMT transcript level in fish gender and developmental stages during Cd exposure. While Pb exposure, the expression alteration happened in spleen, gill, intestine, muscle, and moderately in liver. In the Cu treatment test, there were slight changes in intestine and kidney, but more significant changes occurred in spleen, gill, muscle, and liver. This study had investigated the effects of diverse heavy metals on GrMT expression patterns. The results suggest that GrMT would be a potentional biomarker to metal contamination monitoring in aquatic environments and rare minnow could be one of the perfect experimental fishes for surveying the freshwater pollution in China.
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    ABSTRACT: Glyphosate is globally a widely used herbicide, yet there is little information on their toxicity to marine fishes. Java medaka, a small tropical fish native to coastal areas in several Southeast Asian countries, is viewed as a suitable candidate for toxicity test and thus was used for this study. Java medaka adults were cultured in the laboratory and the fertilized eggs of the F2 generation were exposed to different concentrations of glyphosate-based herbicide (100, 200, 300, 400 and 500ppm) until they hatched. The survival and hatching rates of the embryos, changes in the heart rate and morphological impairments were recorded. Generally, survival and hatching percentage decreased as glyphosate concentration increased. Absence of pectoral fin(s) and cornea, permanently bent tail, irregular shaped abdomen, and cell disruption in the fin, head and abdomen are among the common teratogenic effects observed. Furthermore, risk factor also increased with the increased in glyphosate concentrations.
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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.
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