The Arabidopsis leucine-rich repeat receptor kinase BIR3 has a dual function in the negative regulation of BAK1 receptor complex formation and stabilization of BAK1
S. SCHULZE (1), T. Halter (2), J. Imkampe (3), S. Huang (4), S. Manzotta (5), N. Schmidt (3), R. Manstretta (3), S. Postel (6), F. Tax (7), S. de Vries (8), S. Clouse (9), C. Zipfel (10), X. Wang (11), B. Kemmerling (3) (1) ZMBP-Centre for Plant Molecular Biology, Germany; (10) The Sainsbury Laboratory, Norwich Research Park, Norwich, England; (11) State Key Laboratory of Crop Stress Biology in Arid Areas, College of Horticulture, China; (2) Institut de Biologie de l’Ecole Normale Supérieure (IBENS), France; (3) ZMBP-Centre for Plant Molecular Biology, Germany; (4) State Key Laboratory of Crop Stress Biology in Arid Areas, College of Horticulture, Northwest A&FUniversity, China; (5) Plant Science Company GmbH, Germany; (6) Institute of Human Virology, University of Maryland School of Medicine, U.S.A.; (7) Department of Molecular and Cellular Biology, University of Arizona, U.S.A.; (8) Laboratory of Biochemistry, Wageningen University, Netherlands; (9) Department of Horticultural Science, North Carolina State University, U.S.A.

BAK1 is a multi-functional small leucine-rich repeat receptor kinase (LRR-RLK) acting as a co-receptor of multiple ligand-binding receptors. It is involved in signal perception complexes for various pathways including brassinosteroid signaling, pathogen perception and cell death control. To understand how BAK1 exerts these multiple functions Co-IP-MS-analyses were performed to reveal the nature of BAK1 in vivo complexes. Two novel BAK1-interacting receptor kinases BIR2 and 3 have been identified. Both, BIR2 and BIR3 negatively regulate BAK1 mediated processes by preventing BAK1 interaction with ligand-binding receptors. Additionally, BIR3 directly binds to ligand-binding receptors such as Brassinosteroid Insensitive 1 (BRI1) and Flagellin-Sensitive 2 (FLS2) and thereby competitively inhibits downstream signaling. Co-IP MS analyses with functional BIR3-GFP expressing plants revealed several additional LRR-RLKs indicating that BIR3, as BAK1, is a general interactor of this receptor-type. Furthermore, bir3 bak1 double mutants show a severe autoimmune-dwarf phenotype. A TIR-NBS-LRR protein was identified as a BIR3 interacting protein that could function as a guard of the BAK1 BIR3 complex and explain the mechanism of BAK1 and BIR3 mediated cell death control. Here, we present latest results on the interactome of BIR3 and the impact of the candidates on BAK1-regulated processes.

Abstract Number: C9-5, P17-655
Session Type: Concurrent