TY - JOUR T1 - <em>Epichloƫ festucae</em> in mutualistic association with <em>Lolium perenne</em> suppresses host apoplastic cysteine protease activity JF - bioRxiv DO - 10.1101/2020.11.06.371211 SP - 2020.11.06.371211 AU - Andrea Passarge AU - Fatih Demir AU - Kimberly Green AU - Jasper R.L. Depotter AU - Barry Scott AU - Pitter F. Huesgen AU - Gunther Doehlemann AU - Johana C. Misas Villamil Y1 - 2020/01/01 UR - http://biorxiv.org/content/early/2020/11/08/2020.11.06.371211.abstract N2 - Plants secrete various defence-related proteins into the apoplast, including proteases. Papain-like cysteine proteases (PLCPs) are central components of the plant immune system. To overcome plant immunity and successfully colonise their hosts, several plant pathogens secrete effector proteins inhibiting plant PLCPs. We hypothesized that not only pathogens but also mutualistic microorganisms interfere with PLCP-meditated plant defences to maintain endophytic colonisation with their hosts. Epichloƫ festucae forms mutualist associations with cool season grasses and produces a range of secondary metabolites that protect the host against herbivores. In this study, we performed a genome wide identification of Lolium perenne PLCPs, analysed their evolutionary relationship and classified them into nine PLCP subfamilies. Using activity-based protein profiling, we identified four active PLCPs in the apoplast of L. perenne leaves that are inhibited during endophyte interactions. We characterized the L. perenne cystatin LpCys1 for its inhibitory capacity against ryegrass PLCPs. LpCys1 inhibits LpCP2, indicating that LpCys1 might play a role in the suppression of PLCP activity during the interaction with E. festucae. However, since the activity of other L. perenne PLCPs is not sensitive to LpCys1 we propose that additional inhibitors are involved in the suppression of apoplastic PLCPs during E. festucae infection.Competing Interest StatementThe authors have declared no competing interest. ER -