PT  - JOURNAL ARTICLE
AU  - Shuaishuai Wang
AU  - Rongkang Xing
AU  - Yan Wang
AU  - Haidong Shu
AU  - Shenggui Fu
AU  - Judith K. Paulus
AU  - Mariana Schuster
AU  - Diane G.O. Saunders
AU  - Joe Win
AU  - Vivianne Vleeshouwers
AU  - Xiaobo Zheng
AU  - Renier A. L. van der Hoorn
AU  - Sophien Kamoun
AU  - Suomeng Dong
TI  - Cleavage of a pathogen apoplastic protein by plant subtilases activates immunity
AID  - 10.1101/2019.12.16.878272
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 2019.12.16.878272
4099  - http://biorxiv.org/content/early/2019/12/17/2019.12.16.878272.short
4100  - http://biorxiv.org/content/early/2019/12/17/2019.12.16.878272.full
AB  - The plant apoplast is a harsh environment in which hydrolytic enzymes, especially proteases, accumulate during pathogen infection. However, the defense functions of most apoplastic proteases remains largely elusive. Here, we show that a newly identified small cysteine-rich secreted protein PC2 from the potato late blight pathogen Phytophthora infestans induces immunity in Solanum plant species only after cleavage by plant apoplastic subtilisin-like proteases, such as tomato P69B. A minimal 61-amino-acid core peptide carrying two key cysteines and widely conserved among most oomycete species is sufficient for PC2 activity. Kazal-like protease inhibitors, such as EPI1 produced by P. infestans can prevent PC2 cleavage and dampen PC2 elicited host immunity. This study reveals that cleavage of pathogen proteins to release immunogenic peptides is an important function of apoplastic proteases but that pathogens interfere with these functions using protease inhibitor effectors.