Effect of different metals on protease activity in sunflower cotyledons

LB PENA; ML TOMARO; SM GALLEGO

Buenos Aires

Congreso; Congreso Internacional BAIRESBIOTEC2005; 2005

REDBIO

Proteolysis is crucial for all living cells. Two different proteolytic pathways mediate plant proteolysis: the selective breakdown of proteins by the ubiquitin/proteasome pathway (ATP-dependent) controls key aspects of plant growth, development, and defense. On the other hand, proteases (ATP-independent) are thought to be involved in a range of processes, including germination, senescence, defense responses, programmed cell death. Peptidases are classified based on their catalytic mechanisms. Five catalytic classes (serine, cysteine, aspartic, threonine and metallopeptidases) can been identified within the Arabidopsis genome sequence. In addition or alternatively to a physiological function in cell, proteases might also play a role in the plant adaptation to changing environmental conditions. Extreme environmental conditions (heavy metals, chilling, high temperature, drought, flood, anoxia, high light intensity, etc) that induce oxidative stress has been associated to an increase carbonyl group content and with induction in protease activity. The protein modification promoted by oxidative stress is characterized by production of carbonyl groups in the molecules. Sunflower is a plant that dramatically reduces the levels of metals in the soil so is suitable for phytoremediation. To understand the role of the proteolysis in response to metal stress, sunflower plants were treated with 100 µM of different metals (cadmium, copper, aluminum, cobalt, lead, chromium, nickel, mercury, zinc). Changes in proteolytic activity, gelatinase profile and protein oxidation have been examined in sunflower cotyledons, a tissue where proteolysis is essential for supplying amino acids for protein synthesis mobilizing protein reserves.