Moreover, the non-ionic Hg evolution was directly
proportional to the mRNA of the merA gene, and RT-PCR
results provided evidence that the mercury detoxification
observed in transgenic plants was due to the action of the
introduced gene. Results of Western blot clearly indicated
the expression of merA in the transgenic tobacco lines, and
the mercury tolerance assay performed with inorganic
mercury for the transgenics clearly indicated a 5-7 times
higher tolerance towards inorganic mercury in comparison
with wild-type control plants. These results suggest that
merA-encoded mercurial reductase has abilities to reduce
mercury toxicity. The bacterial native merA gene has been
previously expressed via plastid genome [21], although
this is the first time we are reporting the expression of a
native merA gene via the nuclear genome of Nicotiana
tabacum. The key findings of the study were the expression
of bacterial native merA gene in transgenic tobacco plants
without making any change in its gene sequence, and
volatilization of increased amount of mercury (6-7 times
higher than wild-type plant) from the transgenic tobacco
plants. Based on the findings, we can say that the
expression of native merA gene via the nuclear genome of
transgenic tobacco has the potential of becoming a useful
phytoremediation system in the near future for mercurypolluted
areas. The placement of these improved plants
around pollution sources and at their point of discharge
and harvest could prevent toxic Hg2+ accumulation and
transport from these locations. Air movement will dilute
the transformed mercury (Hg0
) into nontoxic levels and
remove it from these locations. This mercury will be reoxidized
in the atmosphere and return diluted to the
terrestrial and marine sediments, bound to sulfur and
carbon compounds. Ultimately, this should lead to a more
natural distribution of mercury in the environment and
lower the mercury concentration to a nontoxic level in
polluted areas where it threatens wildlife and human
populations.