ER-Quality Control is required for Cf-protein function

PO-22 ER-Quality Control is required for Cf-protein function Thomas Liebrand1, Jan Cordewener2, Antoine America2, and Matthieu Joosten1 1 Laboratory of Phytopathology, Wageningen University, The Netherlands 2 Plant Research International, Business Unit Bioscience, Wageningen University and Research Centre, The Netherlands The plasma membrane-resident tomato (Solanum lycopersicum) Cf receptor-like proteins recognize Avr effectors of the fungal pathogen Cladosporium fulvum. To date, few host components involved in Cf-biogenesis and signaling have been identified. We perform affinity purification from plant extracts to identify Cf-interacting proteins. We transiently expressed a Cf-4-eGFP fusion protein in Nicotiana benthamiana by agroinfiltration. Immunoprecipitation of Cf-4-eGFP and subsequent mass spectrometry analysis revealed the endoplasmic reticulum (ER)-resident HSP70 chaperone Binding Protein 1 BiP1 as co-purifying protein. Co-Immunoprecipitation assays revealed that BiP also interacts with transiently expressed eGFP tagged Cf-2, Cf-9, Cf-4E and Peru2 (a Cf homolog). BiP is part of an ER-chaperone complex together with ERdj3b and SDF2. Besides the BiP chaperone complex, the N-linked glycosylation pathway including the ER-localized lectin-like chaperone calreticulins (CRTs) are involved in ER-quality control (ER-QC). Using Virus-Induced Gene Silencing in transgenic N. benthamiana:Cf-4 plants we studied the role of ER-QC for Cf-4 functioning. We discovered that silencing of specifically CRT3-likes reduced the Avr4-triggred HR, but not the HR triggered by the CC-NB-LRR autoactive mutant Rx(D460V) or the apoptotic factor BAX. Silencing of NbBiP1 did not reduce Avr4-triggered HR, which may be explained by redundancy with one of the other two BiPs. Acknowledgements This work is supported by CBSG2012 PG6 and CBSG Hotel project TD8-08.