Effect of azospirillum lectins on the activity of proteolytic enzymes and their inhibitors in wheat seedling roots

Azospirillum brasilense, which has the potential to stimulate plant growth, belongs to the group of plant-growth-promoting bacteria. The lectin found on the surface of A. brasilense strain Sp7 and Sp245 have the ability to bind specific carbohydrates and ensures adhesion of the bacteria to the root surface. The aim of this work was to investigate possible effects of the Sp7 and Sp245 lectins on the activities of proteases and their inhibitors in wheat seedling roots. Spectrophotometry was used to determine the activities of proteolytic enzymes and trypsin inhibitors in the cells of wheat root seedlings. The Sp7 lectin decreased the activities of acidic (pH 3.5), neutral (6.8), and alkaline (pH 7.8) proteinases, whereas the Sp245 lectin activated all enzymes but acidic proteinases, whose activity remained unchanged. The lectins changed the ratio between the activities of different protease types in germinating seeds. The trypsin-inhibiting activity in wheat seedling roots increased in the presence of the lectins under study. The results of the study suggest that the range of effects of Azospirillum lectins on host plant metabolism is wider then previously thought. Together with the already existing evidence, they allow correction of the current views of the mechanisms responsible for the plant-bacterial interaction during the formation of an association.