PT  - JOURNAL ARTICLE
AU  - Sun, Yadong
AU  - Li, Lei
AU  - Macho, Alberto P.
AU  - Han, Zhifu
AU  - Hu, Zehan
AU  - Zipfel, Cyril
AU  - Zhou, Jian-Min
AU  - Chai, Jijie
TI  - Structural Basis for flg22-Induced Activation of the <em>Arabidopsis</em> FLS2-BAK1 Immune Complex
AID  - 10.1126/science.1243825
DP  - 2013 Nov 01
TA  - Science
PG  - 624--628
VI  - 342
IP  - 6158
4099  - http://science.sciencemag.org/content/342/6158/624.short
4100  - http://science.sciencemag.org/content/342/6158/624.full
SO  - Science2013 Nov 01; 342
AB  - In defense against bacterial infection, plants carry a cell-surface receptor, known as FLS2, that can bind to a fragment of bacterial flagellin and trigger defense responses. Y. Sun et al. (p. 624, published online 10 October) investigated the structural details that govern the binding between FLS2, its co-receptor BAK1, and the flagellin fragment flg22. The assembled complex initiates signals to activate the plant's innate immune response.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.