The interactome of BIR2 reveals a novel adapter protein potentially linking BAK1 to NB-LRR-type resistance genes
R. MANSTRETTA (1), T. Halter (2), N. Schmidt (3), S. Schulze (3), B. Kemmerling (3) (1) Department of Plant Biochemistry (ZMBP), Eberhard-Karls-University, 72076 Tübingen, Germany, Germany; (2) Institut de Biologie de l’Ecole Normale Supérieure (IBENS), 75005 Paris, France, France; (3) Department of Plant Biochemistry (ZMBP), Eberhard-Karls-University, 72076 Tübingen, Germany, Germany

BAK1 is a small Leucine-Rich Repeat Receptor Kinase (LRR-RLK), which is a co-receptor of multiple LRR-RLK-type receptors in pathogen and brassinosteroid sensing mechanisms in A. thaliana. In vivo complexes of BAK1 contain the BAK1 interacting receptor kinase 2 (BIR2), a small LRR-RLK which negatively regulates BAK1 by preventing its interaction with LRR-RLK-type receptor proteins in the absence of their ligands. Furthermore, bir2 mutants show a strong impact on cell death control. To further analyze the functions and mechanisms of BIR2 we performed MS analyses of native BIR2 co-immunoprecipitates and found an unusual TIR-protein and an adapter protein that might link the BAK1 BIR2 complex to NB-LRR-type resistance genes. The BIR2 interacting protein adapter has a coiled coil domain that can interact with NB-LRR-type resistance genes. Its interaction with BIR2 and the closest homolog of BIR2, BIR3, was confirmed by co-immunoprecipitation in planta. Mutants in this adapter protein are more resistant to necrotrophic fungal infection, a phenotype antagonistic to the one observed for BIR2 on cell death, indicating this novel adapter as a positive regulator of cell death in plant defense. Epistasis analyses with double mutants of bir2 and the adapter protein, receptor complex partners and dynamics and further analysis of the link between BAK1/BIR2 mediated cell death and NB-LRR-type resistance genes will be presented.

Abstract Number: P17-568
Session Type: Poster