Towards identification of active root-secreted proteases of Arabidopsis thaliana.

Besides traditional production systems, such as bacteria, yeasts and mammal cells, plants can now be used to produce eukaryotic recombinant proteins. Their advantages as hosts for proteins production include correct post-translational modifications, low cost of maintenance and no risk of contamination by human pathogens. Targeting heterologous proteins to the extracellular space is required for the correct folding of complex proteins and makes harvesting and purification easier. However, the quantity and the quality of recombinant proteins have been proved to be reduced by the action of endogenous co-secreted proteases.
In this study, we characterized root-secreted proteases in the model plant Arabidopsis thaliana, at the activity and expression levels. Their activity was analyzed by in vitro degradation of a target protein (Bovine Serum Albumine, BSA) in a range of pH and in the presence of several proteases inhibitors. Serine proteases were identified as the major protease class involved in the degradation of BSA under all tested conditions. As a first step towards the identification of the key players, the expression level of selected members of this class was analyzed by quantitative RT-PCR in roots and leaves.