Proteases are crucial for living
cells and
play a
role in
plant cell adaptation to environmental conditions.
Oxidative stress produced oxidized
proteins which are selectively degraded by
proteases. To understand the
role of
proteolysis in response to
metal stress,
sunflower plants (a
plant suitable for
phytoremediation) were treated with 100 µM of
CdCl2, CuCl2,
AlCl3, CoCl2, PbCl2, CrCl3, NiCl2,
HgCl2 or ZnCl2. Changes in
protease activity,
gelatinase profile and
protein oxidation were examined in
sunflower cotyledons. Our results indicate that this
tissue has mainly
acid proteases belonging to different classes. Although all
metals (except Zn) increased
protein oxidation (62, 57, 112, 74, 74, 68, 64 and 40 percent for Pb, Al, Ni, Cd, Hg, Co, Cr and Cu over the control), they altered
proteolysis in different ways. Pb, Al and Ni
treatment decreased
protease activity 22, 28 and 30 percent
respect to control while Cd and Hg increased this activity in 23 and 27 percent. In Zn, Cu and Co
treatments protease activity remained
similar to control
treatment. These results indicate that different
proteases are involved in
plant defence against
metal toxicity. However, the identification of specific oxidized
proteins involved in this process and the
metal effect on class specific
proteases should provide greater information.