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under stress. Proteomic fi ndings suggest that translocation of
cadmium from the root to the aerial parts might be prevented by
the increased xylem lignifi cation. To further dissect the protein
networks involved in cadmium stress response in soybean, we per-
formed a comparative proteomic study among contrasting
cadmium accumulating soybean cultivars [
35
]. Study revealed that
both high (Harosoy) and low (Fukuyutaka) cadmium accumulat-
ing cultivars and their recombinant inbred line CDH-80 share
some common defense strategies to cope with the cadmium stress.
High abundance of enzymes involved in glycolysis and TCA cycle
was evident, that might help cadmium challenged cells to produce
more energy necessary to meet the high energy demand. Moreover,
enhanced expression of glutamine synthetase might be involved in
phytochelatin-mediated detoxifi cation of cadmium ions. Increased
abundance of antioxidant enzymes (SOD, APX, CAT) further
ensures cellular protection from ROS mediated damages under
cadmium stress.
Role of stress-responsive proteins in conferring aluminum
resistance in soybean has been elucidated by Zhen et al. [
17
]. To
induce stress, 1-week-old soybean seedlings were exposed to
50
M AlCl
3
for 24, 48 and 72 h. 2-DE analysis of root proteins
revealed 39 differentially expressed protein spots, with 21 increased,
13 newly induced and 5 decreased. The heat shock protein, gluta-
thione
S
-transferase, chalcone-related synthetase, GTP-binding
protein, and ABC transporter ATP-binding protein were identifi ed
as aluminum-responsive proteins. Results indicate that plants
stress/defense, signal transduction, transport, protein folding,
gene regulation, and primary metabolisms are primarily affected
under aluminum stress.
ÎĽ
To reveal the stress-induced changes in protein expression, in vitro
grown cells offer advantages over the young seedlings as all the
cultured cells grow in uniform environment and uniform stress
pressure can be applied. Sobkowiak and Deckert [
36
] studied the
cadmium-induced changes in protein pattern in soybean cell sus-
pension culture. Synthesis of [
35
S]-labeled proteins and their accu-
mulation were analyzed by SDS-PAGE and identifi cation of selected
protein bands was performed by mass spectrometry. Cadmium was
found to induce superoxide dismutase, histone H2B, chalcone syn-
thase and glutathione transferase in soybean cells.
As compared to root, root hair offers an excellent single-cell
plant tissue for the proteomic study. Root hair proteome analysis
following the establishment of soybean-
Rhizobium
symbiotic
interaction led to identify novel proteins—phospholipase D and
phosphoglucomutase that appeared to respond to
Bradyrhizobium
japonicum
inoculation [
37
]. In addition, differential protein
expressions in roots and root hairs of soybean were evident.
Chitinase class I and a stress-induced gene H4 were found to be
3.3
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