Arabidopsis heterotrimeric G proteins regulate immunity by directly coupling to the FLS2 receptor

• Published in: eLife 2016-04, Vol.5, p.e13568-e13568
• Main Authors: Liang, Xiangxiu, Ding, Pingtao, Lian, Kehui, Wang, Jinlong, Ma, Miaomiao, Li, Lin, Li, Lei, Li, Meng, Zhang, Xiaojuan, Chen, She, Zhang, Yuelin, Zhou, Jian-Min
• Format: Article
• Language: English
• Subjects: Antigens, Bacterial - immunology; Arabidopsis; Arabidopsis - immunology; Arabidopsis Proteins - metabolism; Biodegradation; Cell Biology; Cell division; Epitopes; Flagellin; Flagellin - immunology; Gene expression; heterotrimeric G proteins; Heterotrimeric GTP-Binding Proteins - metabolism; Immune response; Immunoglobulins; Kinases; NAD(P)H oxidase; oxidative burst; Phosphorylation; Plant Biology; Plant diseases; plant immunity; Proteasomes; Protein Binding; Protein Kinases - metabolism; Proteins; Reactive oxygen species; Reactive Oxygen Species - metabolism; Signal Transduction
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/elife.13568

The Arabidopsis immune receptor FLS2 perceives bacterial flagellin epitope flg22 to activate defenses through the central cytoplasmic kinase BIK1. The heterotrimeric G proteins composed of the non-canonical Gα protein XLG2, the Gβ protein AGB1, and the Gγ proteins AGG1 and AGG2 are required for FLS2-mediated immune responses through an unknown mechanism. Here we show that in the pre-activation state, XLG2 directly interacts with FLS2 and BIK1, and it functions together with AGB1 and AGG1/2 to attenuate proteasome-mediated degradation of BIK1, allowing optimum immune activation. Following the activation by flg22, XLG2 dissociates from AGB1 and is phosphorylated by BIK1 in the N terminus. The phosphorylated XLG2 enhances the production of reactive oxygen species (ROS) likely by modulating the NADPH oxidase RbohD. The study demonstrates that the G proteins are directly coupled to the FLS2 receptor complex and regulate immune signaling through both pre-activation and post-activation mechanisms.