Abstract: It has been reported that the Fl generation of tobaccos (Nicotiana tabacurn L. 90082) transformed with 35S mMT- 1: NOS chimaric gene was significantly different from the control plants with respect to Cd2 + intolerance. Growth of transgenic tobaccos was uneffected by Cd2+ even with concentration as high as 100 μmol/L in the medium, whereas that of control plants was severely hampered in the medium containing only 20 μmol/L Cd2+, indicating a stronger tolerance to Cd2+ in the transgenic tobaccos than the control plants. The total Cd2+, binding Cd2+, and free Cd2+ contents in the transgenic tobaccos were obviously more than those in the control plants, and the rate of root growth and index of mitosis were increased as well. In contrast, much less the frequency of chromosomal aberrations was found in the transgenic tobaccos. These suggested that MT as a membrane protein could function as a channel protein or an ion pump which direetively transport Cd2+ into a structure (e. g. vacuole), except MT formed binding Cd2+. The mMT expresion revealed from Southern blot, Western blot, and Cd2+/haemoglobin saturation analysis all indicated that the transformation was succeeded. The MT protein was found in roots and leaves of the transgenic plants grown in the medium containing 100 μmol/L Cd2+, whereas it was not detected in control and transgenic plants grown in medium without Cd2+.

Key words: mMT- 1 gene, Nicotiana tabacurn, Rate of root growth, Index of mitosis, Frequency of chromosomal aberrations