生物谷：植物含有各种不同的、结构类似于动物体内的类固醇激素的类固醇和固醇。经过艰苦研究，油菜素内酯（brassinosteroids）已被普遍接受为一种重要的植物激素。这个通道的一个关键部分是通过BRI1受体及其共受体BAK1对油菜素内酯的识别。但关于BAK1具有一个完全出乎意料的不同功能的消息可能会使问题复杂化。当先天免疫受体FLS2被其已知配体flagellin 刺激时，BAK1被发现专门与该受体结合。在bak1基因发生突变的拟南芥中，先天免疫响应大大削弱。因此，BAK1似乎在发育和先天免疫中有双重作用，同果蝇中著名的TOLL受体一样。
原始出处:
Nature 448, 497-500 (26 July 2007) | doi:10.1038/nature05999; Received 27 April 2007; Accepted 7 June 2007; Published online 11 July 2007
A flagellin-induced complex of the receptor FLS2 and BAK1 initiates plant defence
Delphine Chinchilla1, Cyril Zipfel1,2, Silke Robatzek1,3, Birgit Kemmerling4, Thorsten Nürnberger4, Jonathan D. G. Jones2, Georg Felix1,4 & Thomas Boller1
Zurich-Basel Plant Science Center, Botanical Institute, University of Basel, Hebelstrasse 1, 4056 Basel, Switzerland
The Sainsbury Laboratory, Colney Lane, Norwich, Norfolk NR4 7UH, UK
Max-Planck-Institute for Plant Breeding Research, Carl-von-Linné Weg 10, 50829 Cologne, Germany
Institute of Plant Biochemistry, ZMBP, University of Tuebingen, 72076 Tuebingen, Germany
Correspondence to: Delphine Chinchilla1Thomas Boller1 Correspondence and requests for materials should be addressed to D.C. (Email: delphine.chinchilla@unibas.ch) or T.B. (Email: thomas.boller@unibas.ch).
Plants sense potential microbial invaders by using pattern-recognition receptors to recognize pathogen-associated molecular patterns (PAMPs)1. In Arabidopsis thaliana, the leucine-rich repeat receptor kinases flagellin-sensitive 2 (FLS2) (ref. 2) and elongation factor Tu receptor (EFR) (ref. 3) act as pattern-recognition receptors for the bacterial PAMPs flagellin4 and elongation factor Tu (EF-Tu) (ref. 5) and contribute to resistance against bacterial pathogens. Little is known about the molecular mechanisms that link receptor activation to intracellular signal transduction. Here we show that BAK1 (BRI1-associated receptor kinase 1), a leucine-rich repeat receptor-like kinase that has been reported to regulate the brassinosteroid receptor BRI1 (refs 6,7), is involved in signalling by FLS2 and EFR. Plants carrying bak1 mutations show normal flagellin binding but abnormal early and late flagellin-triggered responses, indicating that BAK1 acts as a positive regulator in signalling. The bak1-mutant plants also show a reduction in early, but not late, EF-Tu-triggered responses. The decrease in responses to PAMPs is not due to reduced sensitivity to brassinosteroids. We provide evidence that FLS2 and BAK1 form a complex in vivo, in a specific ligand-dependent manner, within the first minutes of stimulation with flagellin. Thus, BAK1 is not only associated with developmental regulation through the plant hormone receptor BRI1 (refs 6,7), but also has a functional role in PRR-dependent signalling, which initiates innate immunity.
图：bak1 mutants show reduced sensitivity to flagellin in growth assays.
