Pathogen-inspired engineering of plant protease enhances late blight resistance

The apoplast is an important battlefield in plant-pathogen interactions. The late blight oomycete pathogen <i>Phytophthora infestans,</i> for instance, secretes cystatin-like protease inhibitors EpiC1 and EpiC2B to suppress C14, a papain-like immune protease secreted by tomato. Here, we found that <i>P. infestans</i> also secretes two distinct papain-like proteases termed Pain1 and Pain2, which are transcriptionally induced during infection. Both Pains promote <i>P. infestans</i> infection, but not when their catalytic residues are mutated. Strikingly, EpiC1 and EpiC2B preferentially inhibit tomato C14 rather than self-produced Pains, suggesting that they coevolved with Pains to avoid self-inhibition. To mimic the avoidance of inhibition by EpiCs, we engineered C14 (eC14) with seven Pain1 residues that potentially disturb the EpiCs-C14 interface. This eC14 is less sensitive to inhibition by EpiCs and enhances resistance to <i>P. infestans</i> infection. This strategy demonstrates that a pathogen-inspired protein engineering approach can increase crop resistance to plant pathogens.