Structural Basis for flg22-Induced Activation of the Arabidopsis FLS2-BAK1 Immune Complex

作者：Yadong Sun, Lei Li, Alberto P. Macho, Zhifu Han, Zehan Hu, Cyril Zipfel, Jian‐Min Zhou, Jijie Chai · 发表于：Science · 年份：2013 · DOI：10.1126/science.1243825 · 被引用次数：807 · 研究领域：Plant-Microbe Interactions and Immunity、Legume Nitrogen Fixing Symbiosis、Plant Pathogenic Bacteria Studies

Flagellin perception in Arabidopsis is through recognition of its highly conserved N-terminal epitope (flg22) by flagellin-sensitive 2 (FLS2). Flg22 binding induces FLS2 heteromerization with BRASSINOSTEROID INSENSITIVE 1-associated kinase 1 (BAK1) and their reciprocal activation followed by plant immunity. Here, we report the crystal structure of FLS2 and BAK1 ectodomains complexed with flg22 at 3.06 angstroms. A conserved and a nonconserved site from the inner surface of the FLS2 solenoid recognize the C- and N-terminal segment of flg22, respectively, without oligomerization or conformational changes in the FLS2 ectodomain. Besides directly interacting with FLS2, BAK1 acts as a co-receptor by recognizing the C terminus of the FLS2-bound flg22. Our data reveal the molecular mechanisms underlying FLS2-BAK1 complex recognition of flg22 and provide insight into the immune receptor complex activation.