DASSI, BARBARA1,2, ELIANE DUMAS-GAUDOT2 & SILVIO GIANINAZZI2.
1Istituto di Patologia Vegetale, Università degli Studi di Milano, via Celoria 2, 20133 Milano, ITALY . 2Laboratoire de Phytoparasitologie, INRA/CNRS, CMSE-INRA, BV 1540, 21034 Dijon cédex, FRANCE.
Protein modifications in tomato roots from control, Glomus mosseae -colonized, Phytophthora parasitica -infected plants and from mycorrhizal plants post-infected with the pathogen were analyzed with the aim of finding protein modifications which could play a role in biological control of soil-borne pathogens. Two approaches were undertaken for identifying modifications in root protein expression: (i) a targeted approach centred on serological identification of Pathogenesis-Related (PR) proteins, known to be involved in plant defence responses to pathogens, and (ii) an untargeted approach using two-dimensional gel electrophoresis (2D-PAGE). Western blotting using antibodies against PR-proteins belonging to groups 1, 2, 3 and 5 showed that whatever the antibody tested, PR-protein expression was only faintly induced in mycorrhizal roots, while with the pathogenic fungus, the level of these proteins was greatly increased. In contrast, in a situation of bioprotection PR-proteins were only weakly expressed in mycorrhizal roots post-infected with the pathogen. This result demonstrats that PR-proteins are not directly implicated in bioprotection by mycorrhiza against P. parasitica in tomato. By 2D-PAGE, we observed that several modifications were induced by mycorrhizal or pathogenic root infection, as compared to control roots. A group of polypeptides which were up-regulated by mycorrhizal colonization and down-regulated by P. parasitica infection was more closely investigated. In a situation of bioprotection the expression of this group of polypeptides was maintained. Although it is premature to speculate that these polypeptides are implicated in bioprotection, they could play a role in interactions between mycorrhizal tomato roots and P. parasitica.
Key words: bioprotection, one- and two-dimensional electrophoresis, Western blotting