Heavy metal pollution has become the major concern of many countries, and the key to control the matter calls for good model organisms as early-warning indicators, effective target genes as molecular markers, and a sensitive method studying differential expressions of the genes. To study the potential molecular mechanisms of cadmium and copper combined toxicity, the unicellular protozoa Tetrahymena thermophila was chosen for its fast growth and sensitivity to pollutants in water ecosystem, and a method of real-time fluorescent quantitative PCR (Q-PCR) was applied which is effective, accurate and has been widely used in molecular field. In this article, the Q-PCR method was optimized, on the basis of which tests were designed to study the relative expression of metallothionein gene (MTT1) in T. thermophila treated with different concentrations of heavy metals cadmium and copper. The results suggested that: MTT1 gene was more sensitive to cadmium induction compared to copper, and in a certain threshold scale (<= 35.2 mu mol/L), raising the cadmium concentrations increased the MTT1 expression level, but made it decreased while beyond the threshold; the expression rule of MTT1 induced by both cadmium and copper was similar to that treated with cadmium only, but then the threshold down to 22 mu mol/L, indicating that combined toxicity of cadmium and copper in T. thermophila were synergism. When treating concentration was lower than 22 mu mol/L, cadmium cooperated with 244 [mu mol/L copper greatly increased the expression level of MTT1, hence enhancing the detoxification ability of Tetrahymena.
Yu Ting; Miao Wei (email@example.com) ; Wan Ming-Liang; Shen Yun-Fen; Fu Cheng-Jie.Expression of metallothionein gene induced by cadmium and copper in Tetrahymena thermophila,Acta Zoologica Sinica,2005,51(6):1115-1121