Extracellular proteolytic cascade in tomato activates immune protease Rcr3
Judith K. Paulus, Jiorgos Kourelis, Selva Kumari Ramasubramanian, Felix Homma, Alice Godson, Anja C. Hörger, Tram Ngoc Hong, Daniel Krahn, Laura Ossorio Carballo, Shuaishuai Wang, Joe Win, Matthew Smoker, Sophien Kamoun, Suomeng Dong, Renier A. L. van der Hoorn
Abstract
Significance The secretion of papain-like cysteine proteases (PLCPs) is an important component of the immune response across the plant kingdom. Here we show that immune protease Rcr3, a secreted PLCP of tomato, is activated by secreted subtilisins, which are common serine proteases in plants. Subtilase P69B activates proRcr3 by cleaving after aspartates in the junction between the autoinhibitory prodomain and the protease domain of the Rcr3 precursor, thereby activating Rcr3. Subtilases of a different subfamily facilitate proRcr3 processing in a tobacco relative, indicating that this proteolytic cascade might be common in plants. Thus, pathogens that secrete subtilisin inhibitors may indirectly prevent the activation of immune proteases.