title: Heterotrimeric G proteins serve as a converging point in plant defense signaling activated by multiple receptor-like kinases.
abstract: In fungi and metazoans, extracellular signals are often perceived by G-protein-coupled receptors (GPCRs) and transduced through heterotrimeric G-protein complexes to downstream targets. Plant heterotrimeric G proteins are also involved in diverse biological processes, but little is known about their upstream receptors. Moreover, the presence of bona fide GPCRs in plants is yet to be established. In Arabidopsis (Arabidopsis thaliana), heterotrimeric G protein consists of one Gα subunit (G protein α-subunit1), one Gβ subunit (Arabidopsis G protein β-subunit1 [AGB1]), and three Gγs subunits (Arabidopsis G protein γ-subunit1 [AGG1], AGG2, and AGG3). We identified AGB1 from a suppressor screen of BAK1-interacting receptor-like kinase1-1 (bir1-1), a mutant that activates cell death and defense responses mediated by the receptor-like kinase (RLK) suppressor of BIR1-1. Mutations in AGB1 suppress the cell death and defense responses in bir1-1 and transgenic plants overexpressing suppressor of BIR1-1. In addition, agb1 mutant plants were severely compromised in immunity mediated by three other RLKs, flagellin-sensitive2 (FLS2), Elongation Factor-TU RECEPTOR (EFR), and chitin elicitor receptor kinase1 (CERK1), respectively. By contrast, G protein α-subunit1 is not required for either cell death in bir1-1 or pathogen-associated molecular pattern-triggered immunity mediated by FLS2, EFR, and CERK1. Further analysis of agg1 and agg2 mutant plants indicates that AGG1 and AGG2 are also required for pathogen-associated molecular pattern-triggered immune responses mediated by FLS2, EFR, and CERK1, as well as cell death and defense responses in bir1-1. We hypothesize that the Arabidopsis heterotrimeric G proteins function as a converging point of plant defense signaling by mediating responses initiated by multiple RLKs, which may fulfill equivalent roles to GPCRs in fungi and animals.
authors: National Institute of Biological Sciences, Zhongguancun Life Science Park, Beijing 102206, China.
authors: Jinman
authors: J
authors: Liu
authors: Pingtao
authors: P
authors: Ding
authors: Tongjun
authors: T
authors: Sun
authors: Yukino
authors: Y
authors: Nitta
authors: Oliver
authors: O
authors: Dong
authors: Xingchuan
authors: X
authors: Huang
authors: Wei
authors: W
authors: Yang
authors: Xin
authors: X
authors: Li
authors: José Ramón
authors: JR
authors: Botella
authors: Yuelin
authors: Y
authors: Zhang
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology* / Q000276:immunology* / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000378:metabolism*; D016923:Cell Death; D003001:Cloning, Molecular; D060467:Disease Resistance / Q000276:immunology; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology; D057865:Plant Immunity; D030821:Plants, Genetically Modified; D011494:Protein Kinases / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D044224:Pseudomonas syringae / Q000502:physiology; D011956:Receptors, Cell Surface / Q000378:metabolism*; D051192:Receptors, Pattern Recognition; D015398:Signal Transduction / Q000276:immunology*; D013489:Suppression, Genetic
chemical_list: D029681:Arabidopsis Proteins; D021122:Protein Subunits; D011956:Receptors, Cell Surface; D051192:Receptors, Pattern Recognition; D011494:Protein Kinases; D020962:Heterotrimeric GTP-Binding Proteins