Copper Removal by SCMT II Transgenic and Wild Type Tobacco in Hydroponic System - a Comparative Study

Saccharomyces cerevisiae metallothionein-II (ScMT-II) genes expressed in Nicotiana tabacum and wild tobacco were grown for 14 days in growth chamber as hydroponics containing 0, 5, and 10 Cu mg L-1 to determine their Cu accumulation ability and to study Cu compartmentation in shoots and roots. Wild type (Nicotiana tabacum L., cv. Petite Havana SRI) and transgenic tobacco (p-S-ScMTII) plants wilted severely, showed stunted root growth with structural deformation. Shoot dry weight, Cu, and free sulphydryl (-SH) groups showed significant differences between transgenic and wild type tobacco plants. Copper accumulation in roots was 7.78 and 10.8 g kg(-1) for transgenic and wild type tobacco, respectively. The study revealed that despite high Cu accumulation in roots, its translocation from roots to shoots was inhibited probably due to blockage and dieback in the root collar. It can be concluded that the main cause of failure in MTII gene induced Cu accumulation in shoots was collapse of root collars due to Cu toxicity. Thus it was not possible to judge the real effect of the MT gene.