Plants including tomato produce
several kinds of chelator proteins such as
metallothioneins (MTs) for protection against
Hg2+ toxicity. However, the mechanism of
protection from Hg2+ is not perfectly clear. Hg2+
content subsequently was plateaued from days 1
to 7. Cell death and DNA digestion were not
observed in the primary root in the presence of
Hg2+ over the 7 days. The predicted protein
sequences of 5 tomato type 2 MT-like (MT2-like)
proteins were compared. The coding sequences
of accession number Z68185 had no Cys-Cys
motif in the N-terminal. However, the Z68185
cDNA genetic recombinant showed high
resistance to Hg2+ in bacteria. In tomato, the
expression was observed in the roots, but not in
the leaves or stems. mRNA of the MT2-like
protein was measured in tomato seedlings
exposed to 1 μM Hg2+. The expression level did
not increase until day 3, but increased
expression was observed after day 5. These
results suggest that new Metallothionein2-like
protein express in root specific and it may trap
mercury. Our results indicate that functional
identification of an MT2-like protein will be useful
for molecular breeding designed to improve plant
tolerance to Hg2+.