FIGURE 4.

The hydrolysis of PsGH7a promotes Phytophthora invasion. (A) Predicted three dimensional structure of the PsGH7a protein obtained using the homologous Phanerochaete chrysosporium cellobiohydrolase Cel7D as the template (PDB: 1z3t). The color gradient shows the sequence from the N terminus (blue) to the C terminus (red). In particular, the putative catalytic residues Glu236 and Glu241 are presented as green sticks. (B) Cellulase activity (IU) of the wild-type and the mutant form PsGH7a^E236A. One unit (U) of cellulase activity was defined as the amount of cellulase that catalyzed the liberation of reducing sugar equivalent to 1.0 μg glucose/min under assay conditions. Three independent biological replicates were used for each protein. (C) After the PsGH7a and the mutant form PsGH7a^E236A proteins were infiltrated into N. benthamiana leaves, P. sojae and P. capsici hyphal plugs were put on the infiltration sites. The buffer was infiltrated as a control (CK); the cell-free supernatant from Pichia pastoris GS115 which contains a empty vector (EV) was also infiltrated as another control. Arrow indicates enlarged lesion area. The pictures were taken at 3 days after inoculation.