The Arabidopsis Malectin-Like/LRR-RLK IOS1 Is Critical for BAK1-Dependent and BAK1-Independent Pattern-Triggered Immunity.
Plasma membrane-localized pattern recognition receptors (PRRs) such as FLAGELLIN SENSING2 (FLS2), EF-TU RECEPTOR (EFR), and CHITIN ELICITOR RECEPTOR KINASE1 (CERK1) recognize microbe-associated molecular patterns (MAMPs) to activate pattern-triggered immunity (PTI). A reverse genetics approach on genes responsive to the priming agent β-aminobutyric acid (BABA) revealed IMPAIRED OOMYCETE SUSCEPTIBILITY1 (IOS1) as a critical PTI player. Arabidopsis thaliana ios1 mutants were hypersusceptible to Pseudomonas syringae bacteria. Accordingly, ios1 mutants showed defective PTI responses, notably delayed upregulation of the PTI marker gene FLG22-INDUCED RECEPTOR-LIKE KINASE1, reduced callose deposition, and mitogen-activated protein kinase activation upon MAMP treatment. Moreover, Arabidopsis lines overexpressing IOS1 were more resistant to bacteria and showed a primed PTI response. In vitro pull-down, bimolecular fluorescence complementation, coimmunoprecipitation, and mass spectrometry analyses supported the existence of complexes between the membrane-localized IOS1 and BRASSINOSTEROID INSENSITIVE1-ASSOCIATED KINASE1 (BAK1)-dependent PRRs FLS2 and EFR, as well as with the BAK1-independent PRR CERK1. IOS1 also associated with BAK1 in a ligand-independent manner and positively regulated FLS2-BAK1 complex formation upon MAMP treatment. In addition, IOS1 was critical for chitin-mediated PTI. Finally, ios1 mutants were defective in BABA-induced resistance and priming. This work reveals IOS1 as a novel regulatory protein of FLS2-, EFR-, and CERK1-mediated signaling pathways that primes PTI activation.
Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan.
Yu-Hung
0000-0002-5520-3206
YH
Yeh
Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan.
Dario
0000-0003-3058-7482
D
Panzeri
The Sainsbury Laboratory, Norwich NR4 7UH, United Kingdom.
Yasuhiro
Y
Kadota
Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan.
Yi-Chun
0000-0002-7487-4443
YC
Huang
Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan.
Pin-Yao
PY
Huang
Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan.
Chia-Nan
0000-0001-8405-0088
CN
Tao
The Sainsbury Laboratory, Norwich NR4 7UH, United Kingdom.
Milena
0000-0002-1993-4802
M
Roux
Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan.
Hsiao-Chiao
HC
Chien
Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan.
Tzu-Chuan
0000-0003-4597-8742
TC
Chin
Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan.
Po-Wei
PW
Chu
The Sainsbury Laboratory, Norwich NR4 7UH, United Kingdom.
Cyril
0000-0003-4935-8583
C
Zipfel
Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan lauzim2@ntu.edu.tw.
Laurent
L
Zimmerli
D000613:Aminobutyrates / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D057865:Plant Immunity / Q000235:genetics / Q000502:physiology; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D044224:Pseudomonas syringae / Q000472:pathogenicity
D000613:Aminobutyrates; D029681:Arabidopsis Proteins; C047667:3-aminobutyric acid; C569619:At1g51800 protein, Arabidopsis; D011494:Protein Kinases; C463660:BAK1 protein, Arabidopsis; C411853:FLS2 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases