Induction of a putative metallothionein gene in the blood cockle, Anadara granosa, exposed to cadmium.
The relationship between a putative metallothionein gene (MT) and exposure to cadmium (Cd) in blood cockles (Anadara granosa) is reported. In a 96-h dose-response experiment, mortality of cockles was found to proportionately increase in the range of 0.2-5.0 mg/l Cd with a calculated LC(50) of 2.94 mg/l. Exposure to 0.25 mg/l Cd for 16 days caused significant increases (P<0.05) in Cd concentrations in whole tissues, gills and hepatopancreas, and the accumulation of Cd in these tissues increased with the duration of exposure. Two cDNA libraries constructed using the hepatopancreas from control and Cd-treated cockles gave titres of 5.62 x 10(5) and 1.94 x 10(5) pfu/microg vector, respectively. A putative MT gene, AnaMT, of 510 nucleotides in length, was isolated from the treated cDNA library using a heterologous probe MT20 from the blue mussel, Mytilus edulis. Northern analyses using AnaMT as a probe indicated low expression of the MT mRNA in control animals. In cockles treated with 0.25 mg/l Cd for 4 days, MT mRNA level increased to approximately 168%, but declined to 108% at day 8. After 12 and 16 days of Cd treatment, expression of the MT gene was 138% and 187%, respectively, compared to the controls. These observations suggest that induction of the MT gene by a sublethal dose of Cd is rapid, occurring within 4 days of treatment.
Chan
M K
MK
School of Environmental Science and Natural Resources, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia.
Othman
R
R
Zubir
D
D
Salmijah
S
S
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002104:Cadmium / Q000378:metabolism / Q000494:pharmacology*; D003062:Codon; D004064:Digestive System / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects / Q000235:genetics*; D005786:Gene Expression Regulation; D005880:Gills / Q000187:drug effects; D008668:Metallothionein / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*; D008969:Molecular Sequence Data; D008974:Mollusca / Q000235:genetics*; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000302:isolation & purification; D013997:Time Factors; D014018:Tissue Distribution
D003062:Codon; D020033:Protein Isoforms; D012333:RNA, Messenger; D002104:Cadmium; D008668:Metallothionein