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Kim Y, Castroverde CDM, Kim JH. Natural allelic diversity of the calcium signaling regulators in plants. Mol Cells 2024:100104. [PMID: 39098739 DOI: 10.1016/j.mocell.2024.100104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2024] [Revised: 07/09/2024] [Accepted: 07/29/2024] [Indexed: 08/06/2024] Open
Abstract
Calcium ions act as secondary messengers in diverse signaling pathways in plants throughout their life cycle. Studies have revealed that calcium is involved in developmental events and in responses to external stimuli, such as biotic and abiotic stresses. Cellular calcium ion levels are tightly controlled by intricate molecular machinery such as calcium channels and pumps. Transient and spatial fluctuations in calcium levels are subsequently recognized by diverse calcium-decoding molecules, resulting in signal transduction. In this review, we highlight recent findings on natural variations in genes controlling calcium signaling in diverse plant biological processes. We then show how the calcium ion context is utilized by fine-tuning the natural variation in centrally important genes.
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Affiliation(s)
- Yejin Kim
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, Korea
| | | | - Jong Hum Kim
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, Korea; Institute for Convergence Research and Education in Advanced Technology, Yonsei University, Seoul 03722, Korea.
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Liu F, Yang Z, Wang C, You Z, Martin R, Qiao W, Huang J, Jacob P, Dangl JL, Carette JE, Luan S, Nogales E, Staskawicz BJ. Activation of the helper NRC4 immune receptor forms a hexameric resistosome. Cell 2024:S0092-8674(24)00773-6. [PMID: 39094568 DOI: 10.1016/j.cell.2024.07.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Revised: 06/06/2024] [Accepted: 07/07/2024] [Indexed: 08/04/2024]
Abstract
Innate immune responses to microbial pathogens are regulated by intracellular receptors known as nucleotide-binding leucine-rich repeat receptors (NLRs) in both the plant and animal kingdoms. Across plant innate immune systems, "helper" NLRs (hNLRs) work in coordination with "sensor" NLRs (sNLRs) to modulate disease resistance signaling pathways. Activation mechanisms of hNLRs based on structures are unknown. Our research reveals that the hNLR, known as NLR required for cell death 4 (NRC4), assembles into a hexameric resistosome upon activation by the sNLR Bs2 and the pathogenic effector AvrBs2. This conformational change triggers immune responses by facilitating the influx of calcium ions (Ca2+) into the cytosol. The activation mimic alleles of NRC2, NRC3, or NRC4 alone did not induce Ca2+ influx and cell death in animal cells, suggesting that unknown plant-specific factors regulate NRCs' activation in plants. These findings significantly advance our understanding of the regulatory mechanisms governing plant immune responses.
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Affiliation(s)
- Furong Liu
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA; Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA, USA
| | - Zhenlin Yang
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, Berkeley, CA, USA; Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA, USA.
| | - Chao Wang
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Zhang You
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Raoul Martin
- Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA, USA
| | - Wenjie Qiao
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA
| | - Jian Huang
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Pierre Jacob
- Department of Biology and Howard Hughes Medical Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jeffery L Dangl
- Department of Biology and Howard Hughes Medical Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jan E Carette
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA
| | - Sheng Luan
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Eva Nogales
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, Berkeley, CA, USA; Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA, USA; Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA; Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Brian J Staskawicz
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA; Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA, USA.
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Wang C, Tang RJ, Kou S, Xu X, Lu Y, Rauscher K, Voelker A, Luan S. Mechanisms of calcium homeostasis orchestrate plant growth and immunity. Nature 2024; 627:382-388. [PMID: 38418878 DOI: 10.1038/s41586-024-07100-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 01/22/2024] [Indexed: 03/02/2024]
Abstract
Calcium (Ca2+) is an essential nutrient for plants and a cellular signal, but excessive levels can be toxic and inhibit growth1,2. To thrive in dynamic environments, plants must monitor and maintain cytosolic Ca2+ homeostasis by regulating numerous Ca2+ transporters3. Here we report two signalling pathways in Arabidopsis thaliana that converge on the activation of vacuolar Ca2+/H+ exchangers (CAXs) to scavenge excess cytosolic Ca2+ in plants. One mechanism, activated in response to an elevated external Ca2+ level, entails calcineurin B-like (CBL) Ca2+ sensors and CBL-interacting protein kinases (CIPKs), which activate CAXs by phosphorylating a serine (S) cluster in the auto-inhibitory domain. The second pathway, triggered by molecular patterns associated with microorganisms, engages the immune receptor complex FLS2-BAK1 and the associated cytoplasmic kinases BIK1 and PBL1, which phosphorylate the same S-cluster in CAXs to modulate Ca2+ signals in immunity. These Ca2+-dependent (CBL-CIPK) and Ca2+-independent (FLS2-BAK1-BIK1/PBL1) mechanisms combine to balance plant growth and immunity by regulating cytosolic Ca2+ homeostasis.
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Affiliation(s)
- Chao Wang
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Ren-Jie Tang
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Senhao Kou
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Xiaoshu Xu
- Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Yi Lu
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Kenda Rauscher
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Angela Voelker
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Sheng Luan
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA.
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Liu F, Yang Z, Wang C, Martin R, Qiao W, Carette JE, Luan S, Nogales E, Staskawicz B. The activated plant NRC4 immune receptor forms a hexameric resistosome. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.12.18.571367. [PMID: 38187616 PMCID: PMC10769213 DOI: 10.1101/2023.12.18.571367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
Innate immune responses against microbial pathogens in both plants and animals are regulated by intracellular receptors known as Nucleotide-binding Leucine-rich Repeats (NLR) proteins. In plants, these NLRs play a crucial role in recognizing pathogen effectors, thereby initiating the activation of immune defense mechanisms. Notably, certain NLRs serve as "helper" NLR immune receptors (hNLR), working in tandem with "sensor" NLR immune receptors (sNLR) counterparts to orchestrate downstream signaling events to express disease resistance. In this study, we reconstituted and determined the cryo-EM structure of the hNLR required for cell death 4 (NRC4) resistosome. The auto-active NRC4 formed a previously unanticipated hexameric configuration, triggering immune responses associated with Ca 2+ influx into the cytosol. Furthermore, we uncovered a dodecameric state of NRC4, where the coil-coil (CC) domain is embedded within the complex, suggesting an inactive state, and expanding our understanding of the regulation of plant immune responses. One Sentence Summary The hexameric NRC4 resistosome mediates cell death associated with cytosolic Ca 2+ influx.
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