Plants and animals rely on immune sensory complexes to detect infection by recognizing evolutionarily conserved pathogen components. Plant immune senor FLS2, a structural and functional ortholog of mammalian Toll-like receptors (TLR), recognizes bacterial flagellin and initiates immune signaling by association with a receptor-like kinase BAK1. It remains unknown how FLS2/BAK1 receptor complex activates intracellular signaling cascades. We have identified two important phosphorylation substrates of BAK1 kinase. BIK1, an FLS2/BAK1-associated cytosolic kinase, is rapidly phosphorylated and released from FLS2/BAK1 receptor complex upon flagellin perception to propagate immune signaling. FCU, an E3 ubiquitin ligase, associates with FLS2 upon flagellin stimulation and ubiquitinates FLS2 receptor. BIK1 transphosphorylates BAK1/FLS2, which in turn enhances BAK1 phosphorylation on FCU. The objective of this application is to examine the role of BIK1 and FCU as convergent components in transducing innate immune signaling from receptor complexes to downstream intracellular events, and the biological significance of phosphorylation and ubiquitination in activating and regulating immune sensory complexes.
Three specific aims are 1) Elucidate the role of receptor-associated kinase in innate immune signaling. 2) Determine the function of E3 ubiquitin ligase in innate immune signaling. 3) Characterize the ubiquitination of PAMP receptor complexes. Recent advance on the molecular architecture of nonself recognition has revealed remarkable conservation in the mechanisms of microbial perception and innate immune signaling in multicellular eukaryotes. Phosphorylation and ubiquitination are two key mechanisms in regulating many cellular and organismal processes, including innate immunity. The power of Arabidopsis genetics and genomics provides an excellent model to understand the functions of these two universal regulatory mechanisms at the whole organism level. Thus, the proposed research will provide new insight on signal transduction in general and contribute to the understanding of innate immune signaling and immune sensory complex function.

Public Health Relevance

Phosphorylation and ubiquitination are two key mechanisms in regulating many cellular and organismal processes in different organisms. Deciphering the molecular and biochemical mechanisms of immune sensory complex regulation and activation by phosphorylation and ubiquitination will contribute to our general understanding of cellular signaling and host innate immunity. Given the considerable similarities of innate immunity among multicellular eukaryotes, we anticipate that our research will have broad impact on the study of innate immunity and signal transduction in general.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Cellular Signaling and Regulatory Systems Study Section (CSRS)
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Dunsmore, Sarah
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Texas A&M University
Other Basic Sciences
Schools of Earth Sciences/Natur
College Station
United States
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Wan, Wei-Lin; Zhang, Lisha; Pruitt, Rory et al. (2018) Comparing Arabidopsis receptor kinase and receptor protein-mediated immune signaling reveals BIK1-dependent differences. New Phytol :
Jamieson, Pierce A; Shan, Libo; He, Ping (2018) Plant cell surface molecular cypher: Receptor-like proteins and their roles in immunity and development. Plant Sci 274:242-251
Shan, Libo; He, Ping (2018) Pipped at the Post: Pipecolic Acid Derivative Identified as SAR Regulator. Cell 173:286-287
Lal, Neeraj K; Nagalakshmi, Ugrappa; Hurlburt, Nicholas K et al. (2018) The Receptor-like Cytoplasmic Kinase BIK1 Localizes to the Nucleus and Regulates Defense Hormone Expression during Plant Innate Immunity. Cell Host Microbe 23:485-497.e5
Zhou, Jinggeng; Liu, Derui; Wang, Ping et al. (2018) Regulation of Arabidopsis brassinosteroid receptor BRI1 endocytosis and degradation by plant U-box PUB12/PUB13-mediated ubiquitination. Proc Natl Acad Sci U S A 115:E1906-E1915
Fan, Jiangbo; Bai, Pengfei; Ning, Yuese et al. (2018) The Monocot-Specific Receptor-like Kinase SDS2 Controls Cell Death and Immunity in Rice. Cell Host Microbe 23:498-510.e5
He, Yunxia; Zhou, Jinggeng; Shan, Libo et al. (2018) Plant cell surface receptor-mediated signaling - a common theme amid diversity. J Cell Sci 131:
Huang, Yanyan; Jamieson, Pierce; Shan, Libo (2018) The APEX Approaches: A Unified LRR-RK Network Revealed. Trends Plant Sci 23:372-374
Yu, Xiao; Feng, Baomin; He, Ping et al. (2017) From Chaos to Harmony: Responses and Signaling upon Microbial Pattern Recognition. Annu Rev Phytopathol 55:109-137
Mang, Hyunggon; Feng, Baomin; Hu, Zhangjian et al. (2017) Differential Regulation of Two-Tiered Plant Immunity and Sexual Reproduction by ANXUR Receptor-Like Kinases. Plant Cell 29:3140-3156

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