Modifications in endopeptidase and 20S proteasome expression and activities in cadmium treated tomato (<Emphasis Type="Italic">Solanum lycopersicum</Emphasis> L.) plants |
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Authors: | Wahbi Djebali Philippe Gallusci Cécile Polge Latifa Boulila Nathalie Galtier Philippe Raymond Wided Chaibi Renaud Brouquisse |
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Institution: | (1) Département de Biologie, Faculté des Sciences de Tunis El Manar, Unité de Recherche de Biologie et Physiologie Cellulaires Végétales, 1060 Tunis, Tunisia;(2) UMR de Biologie des Fruits, INRA, Universités de Bordeaux 1 et Bordeaux 2, BP 81, 33883 Villenave d’Ornon, Bordeaux, France;(3) UMR5168 Physiologie Cellulaire Végétale, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble, France;(4) UMR1064 Interactions Plantes-Microorganismes & Santé Végétale, INRA, Centre de Recherche de Sophia-Antipolis, 400 route des Chappes, BP 167, 06903 Sophia Antipolis Cedex, France |
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Abstract: | The effects of cadmium (Cd) on cellular proteolytic responses were investigated in the roots and leaves of tomato (Solanum lycopersicum L., var Ibiza) plants. Three-week-old plants were grown for 3 and 10 days in the presence of 0.3–300 μM Cd and compared to
control plants grown in the absence of Cd. Roots of Cd treated plants accumulated four to fivefold Cd as much as mature leaves.
Although 10 days of culture at high Cd concentrations inhibited plant growth, tomato plants recovered and were still able
to grow again after Cd removal. Tomato roots and leaves are not modified in their proteolytic response with low Cd concentrations
(≤3 μM) in the incubation medium. At higher Cd concentration, protein oxidation state and protease activities are modified
in roots and leaves although in different ways. The soluble protein content of leaves decreased and protein carbonylation
level increased indicative of an oxidative stress. Conversely, protein content of roots increased from 30 to 50%, but the
amount of oxidized proteins decreased by two to threefold. Proteolysis responded earlier in leaves than in root to Cd stress.
Additionally, whereas cysteine- and metallo-endopeptidase activities, as well as proteasome chymotrypsin activity and subunit
expression level, increased in roots and leaves, serine-endopeptidase activities increased only in leaves. This contrasted
response between roots and leaves may reflect differences in Cd compartmentation and/or complexation, antioxidant responses
and metabolic sensitivity to Cd between plant tissues. The up-regulation of the 20S proteasome gene expression and proteolytic
activity argues in favor of the involvement of the 20S proteasome in the degradation of oxidized proteins in plants.
This paper is dedicated to Nathalie Galtier (1964–2005), who was senior researcher at the INRA Research Center, Villenave
d’Ornon, France. |
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Keywords: | Cadmium Endopeptidase Oxidative Stress Protease 20S Proteasome Tomato |
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