Defence protein and enzyme studies in tomato - Alternaria solani interaction. | Estudios de enzimas y proteínas de defensa en la interacción con Alternaria solani en tomate.

Isozyme variations were studied during the pathogenesis process of several systems related with the antioxidant activity, signal and defence responses in tomato plants (Lycopersicon esculentum, Mill) inoculated with the Alternaria solani fungus which is the causal agent of the early blight disease. The differential expression between control and inoculated plants for all the studied enzymes and the relationship with the defence of peroxidases (PO), chitinases and lipoxygenases (LOX) were determined. Pathogenesis related proteins (PRs) were detected and also their antigenic relation with 1, 2, 3 5 PRs families respectively. The results with the three first families were specifically according to their differential behaviour in the employed varieties. It could be an active component in plant defence. Two polypeptides with LOX activity were purified from NCEBR-1 leaves by anionic exchange chromatography (DEAE- Sephadex A-25) and filtration in gel by Sephadex G- 75 and antibodies were obtained. The purified polypeptide biological activity was demonstrated in plasmatic membranes isolated from tomato cells. The activity was assayed by diluted applications of A. solani micelial solutions. The early transcript expression, following inoculation, showed the relationship of polypeptides with signal mechanisms. The expression of the transcripts resulted earlier and higher in intensity in the resistant variety than in the susceptible one. A significant interaction between the varieties and isolates used was obtained in the analysis of the main enzymatic systems studied. This demonstrates a specific relationship of these enzymes with the most resistant varieties in this pathosystem. LOX enzyme allowed a better differentiation in the assayed varieties, showing for first time its potential as an induced resistance indicator. The results established a biological model which combined the studied biochemical variables and their relationship with the pathogenic process.