Ribulose-1,5-bisphosphate carboxylase/oxygenase expression in melon plants infected with Colletotrichum lagenarium : Activity, content and rate of synthesis.
Ribulose-1,5-bisphosphate carboxylase/oxygelase (RuBPCase) was studied in melon leaves infected by Colletotrichum lagenarium, a fungal pathogen of melons. Electrophoretic analysis of melon leaf proteins indicated a strong effect of infection on RuBPCase, the subunits of which gradually disappeared during the different stages of infection. Enzyme activity also declined 4 d after inoculation and its content, measured by immunoelectrophoresis, decreased to a similar extent. Synthesis of the large and small subunits of RuBPCase was followed by in-vivo pulse-labeling experiments. A drastic decrease in the rate of RuBPCase-subunit synthesis occurred 3 d after inoculation and preceded the appearance of disease symptoms. There was an apparent coordination of the synthesis of the two subunits under these conditions.
Centre de Physiologie Végétale, U.A. CNRS no 241, Université Paul Sabatier, 118, route de Narbonne, F-31062, Toulouse Cédex, France.
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