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Chang W, Qiao Q, Li Q, Li X, Li Y, Huang X, Wang Y, Li J, Wang B, Wang L. Non-transcriptional regulatory activity of SMAX1 and SMXL2 mediates karrikin-regulated seedling response to red light in Arabidopsis. MOLECULAR PLANT 2024; 17:1054-1072. [PMID: 38807366 DOI: 10.1016/j.molp.2024.05.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 04/09/2024] [Accepted: 05/26/2024] [Indexed: 05/30/2024]
Abstract
Karrikins and strigolactones govern plant development and environmental responses through closely related signaling pathways. The transcriptional repressor proteins SUPPRESSOR OF MAX2 1 (SMAX1), SMAX1-like2 (SMXL2), and D53-like SMXLs mediate karrikin and strigolactone signaling by directly binding downstream genes or by inhibiting the activities of transcription factors. In this study, we characterized the non-transcriptional regulatory activities of SMXL proteins in Arabidopsis. We discovered that SMAX1 and SMXL2 with mutations in their ethylene-response factor-associated amphiphilic repression (EAR) motif had undetectable or weak transcriptional repression activities but still partially rescued the hypocotyl elongation defects and fully reversed the cotyledon epinasty defects of the smax1 smxl2 mutant. SMAX1 and SMXL2 directly interact with PHYTOCHROME INTERACTION FACTOR 4 (PIF4) and PIF5 to enhance their protein stability by interacting with phytochrome B (phyB) and suppressing the association of phyB with PIF4 and PIF5. The karrikin-responsive genes were then identified by treatment with GR24ent-5DS, a GR24 analog showing karrikin activity. Interestingly, INDOLE-3-ACETIC ACID INDUCIBLE 29 (IAA29) expression was repressed by GR24ent-5DS treatment in a PIF4- and PIF5-dependent and EAR-independent manner, whereas KARRIKIN UPREGULATED F-BOX 1 (KUF1) expression was induced in a PIF4- and PIF5-independent and EAR-dependent manner. Furthermore, the non-transcriptional regulatory activity of SMAX1, which is independent of the EAR motif, had a global effect on gene expression. Taken together, these results indicate that non-transcriptional regulatory activities of SMAX1 and SMXL2 mediate karrikin-regulated seedling response to red light.
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Affiliation(s)
- Wenwen Chang
- Key Laboratory of Seed Innovation, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang, Hebei 050021, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qiao Qiao
- Key Laboratory of Seed Innovation, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang, Hebei 050021, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qingtian Li
- Yazhouwan National Laboratory, Sanya, Hainan 572024, China
| | - Xin Li
- Key Laboratory of Seed Innovation, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang, Hebei 050021, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yanyan Li
- Key Laboratory of Seed Innovation, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang, Hebei 050021, China
| | - Xiahe Huang
- Key Laboratory of Seed Innovation, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China
| | - Yingchun Wang
- Key Laboratory of Seed Innovation, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jiayang Li
- Key Laboratory of Seed Innovation, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; Yazhouwan National Laboratory, Sanya, Hainan 572024, China
| | - Bing Wang
- Key Laboratory of Seed Innovation, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Lei Wang
- Key Laboratory of Seed Innovation, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang, Hebei 050021, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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Stirling SA, Guercio AM, Patrick RM, Huang XQ, Bergman ME, Dwivedi V, Kortbeek RWJ, Liu YK, Sun F, Tao WA, Li Y, Boachon B, Shabek N, Dudareva N. Volatile communication in plants relies on a KAI2-mediated signaling pathway. Science 2024; 383:1318-1325. [PMID: 38513014 DOI: 10.1126/science.adl4685] [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: 10/19/2023] [Accepted: 02/08/2024] [Indexed: 03/23/2024]
Abstract
Plants are constantly exposed to volatile organic compounds (VOCs) that are released during plant-plant communication, within-plant self-signaling, and plant-microbe interactions. Therefore, understanding VOC perception and downstream signaling is vital for unraveling the mechanisms behind information exchange in plants, which remain largely unexplored. Using the hormone-like function of volatile terpenoids in reproductive organ development as a system with a visual marker for communication, we demonstrate that a petunia karrikin-insensitive receptor, PhKAI2ia, stereospecifically perceives the (-)-germacrene D signal, triggering a KAI2-mediated signaling cascade and affecting plant fitness. This study uncovers the role(s) of the intermediate clade of KAI2 receptors, illuminates the involvement of a KAI2ia-dependent signaling pathway in volatile communication, and provides new insights into plant olfaction and the long-standing question about the nature of potential endogenous KAI2 ligand(s).
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Affiliation(s)
- Shannon A Stirling
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907, USA
| | - Angelica M Guercio
- Department of Plant Biology, College of Biological Sciences, University of California-Davis, Davis, CA 95616, USA
| | - Ryan M Patrick
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907, USA
- Purdue Center for Plant Biology, Purdue University, West Lafayette, IN 47907, USA
| | - Xing-Qi Huang
- Purdue Center for Plant Biology, Purdue University, West Lafayette, IN 47907, USA
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Matthew E Bergman
- Purdue Center for Plant Biology, Purdue University, West Lafayette, IN 47907, USA
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Varun Dwivedi
- Purdue Center for Plant Biology, Purdue University, West Lafayette, IN 47907, USA
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Ruy W J Kortbeek
- Purdue Center for Plant Biology, Purdue University, West Lafayette, IN 47907, USA
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Yi-Kai Liu
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Fuai Sun
- Department of Plant Biology, College of Biological Sciences, University of California-Davis, Davis, CA 95616, USA
| | - W Andy Tao
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
- Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA
- Purdue Institute for Cancer Research, Purdue University, West Lafayette, IN 47907, USA
| | - Ying Li
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907, USA
- Purdue Center for Plant Biology, Purdue University, West Lafayette, IN 47907, USA
| | - Benoît Boachon
- Purdue Center for Plant Biology, Purdue University, West Lafayette, IN 47907, USA
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
- Université Jean Monnet Saint-Etienne, CNRS, LBVpam UMR 5079, F-42023 Saint-Etienne, France
| | - Nitzan Shabek
- Department of Plant Biology, College of Biological Sciences, University of California-Davis, Davis, CA 95616, USA
| | - Natalia Dudareva
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907, USA
- Purdue Center for Plant Biology, Purdue University, West Lafayette, IN 47907, USA
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
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Kamran M, Melville KT, Waters MT. Karrikin signalling: impacts on plant development and abiotic stress tolerance. JOURNAL OF EXPERIMENTAL BOTANY 2024; 75:1174-1186. [PMID: 38001035 PMCID: PMC10860534 DOI: 10.1093/jxb/erad476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 11/23/2023] [Indexed: 11/26/2023]
Abstract
Plants rely upon a diverse range of metabolites to control growth and development, and to overcome stress that results from suboptimal conditions. Karrikins (KARs) are a class of butenolide compounds found in smoke that stimulate seed germination and regulate various developmental processes in plants. KARs are perceived via a plant α/β-hydrolase called KARRIKIN INSENSITIVE2 (KAI2), which also functions as a receptor for a postulated phytohormone, provisionally termed KAI2 ligand (KL). Considered natural analogues of KL, KARs have been extensively studied for their effects on plant growth and their crosstalk with plant hormones. The perception and response pathway for KAR-KL signalling is closely related to that of strigolactones, another class of butenolides with numerous functions in regulating plant growth. KAR-KL signalling influences seed germination, seedling photomorphogenesis, root system architecture, abiotic stress responses, and arbuscular mycorrhizal symbiosis. Here, we summarize current knowledge of KAR-KL signalling, focusing on its role in plant development, its effects on stress tolerance, and its interaction with other signalling mechanisms.
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Affiliation(s)
- Muhammad Kamran
- School of Molecular Sciences, The University of Western Australia, Perth, WA 6009, Australia
| | - Kim T Melville
- School of Molecular Sciences, The University of Western Australia, Perth, WA 6009, Australia
| | - Mark T Waters
- School of Molecular Sciences, The University of Western Australia, Perth, WA 6009, Australia
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Melville KT, Kamran M, Yao J, Costa M, Holland M, Taylor NL, Fritz G, Flematti GR, Waters MT. Perception of butenolides by Bacillus subtilis via the α/β hydrolase RsbQ. Curr Biol 2024; 34:623-631.e6. [PMID: 38183985 DOI: 10.1016/j.cub.2023.12.035] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 12/06/2023] [Accepted: 12/12/2023] [Indexed: 01/08/2024]
Abstract
The regulation of behavioral and developmental decisions by small molecules is common to all domains of life. In plants, strigolactones and karrikins are butenolide growth regulators that influence several aspects of plant growth and development, as well as interactions with symbiotic fungi.1,2,3 DWARF14 (D14) and KARRIKIN INSENSITIVE2 (KAI2) are homologous enzyme-receptors that perceive strigolactones and karrikins, respectively, and that require hydrolase activity to effect signal transduction.4,5,6,7 RsbQ, a homolog of D14 and KAI2 from the gram-positive bacterium Bacillus subtilis, regulates growth responses to nutritional stress via the alternative transcription factor SigmaB (σB).8,9 However, the molecular function of RsbQ is unknown. Here, we show that RsbQ perceives butenolide compounds that are bioactive in plants. RsbQ is thermally destabilized by the synthetic strigolactone GR24 and its desmethyl butenolide equivalent dGR24. We show that, like D14 and KAI2, RsbQ is a functional butenolide hydrolase that undergoes covalent modification of the catalytic histidine residue. Exogenous application of both GR24 and dGR24 inhibited the endogenous signaling function of RsbQ in vivo, with dGR24 being 10-fold more potent. Application of dGR24 to B. subtilis phenocopied loss-of-function rsbQ mutations and led to a significant downregulation of σB-regulated transcripts. We also discovered that exogenous butenolides promoted the transition from planktonic to biofilm growth. Our results suggest that butenolides may serve as inter-kingdom signaling compounds between plants and bacteria to help shape rhizosphere communities.
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Affiliation(s)
- Kim T Melville
- School of Molecular Sciences, The University of Western Australia, Perth WA 6009, Australia
| | - Muhammad Kamran
- School of Molecular Sciences, The University of Western Australia, Perth WA 6009, Australia
| | - Jiaren Yao
- School of Molecular Sciences, The University of Western Australia, Perth WA 6009, Australia
| | - Marianne Costa
- School of Molecular Sciences, The University of Western Australia, Perth WA 6009, Australia
| | - Madeleine Holland
- School of Molecular Sciences, The University of Western Australia, Perth WA 6009, Australia
| | - Nicolas L Taylor
- School of Molecular Sciences, The University of Western Australia, Perth WA 6009, Australia; Institute of Agriculture, The University of Western Australia, Perth WA 6009, Australia
| | - Georg Fritz
- School of Molecular Sciences, The University of Western Australia, Perth WA 6009, Australia
| | - Gavin R Flematti
- School of Molecular Sciences, The University of Western Australia, Perth WA 6009, Australia
| | - Mark T Waters
- School of Molecular Sciences, The University of Western Australia, Perth WA 6009, Australia.
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Waters MT, Nelson DC. Karrikin perception and signalling. THE NEW PHYTOLOGIST 2023; 237:1525-1541. [PMID: 36333982 DOI: 10.1111/nph.18598] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Accepted: 09/29/2022] [Indexed: 06/16/2023]
Abstract
Karrikins (KARs) are a class of butenolide compounds found in smoke that were first identified as seed germination stimulants for fire-following species. Early studies of KARs classified the germination and postgermination responses of many plant species and investigated crosstalk with plant hormones that regulate germination. The discovery that Arabidopsis thaliana responds to KARs laid the foundation for identifying mutants with altered KAR responses. Genetic analysis of KAR signalling revealed an unexpected link to strigolactones (SLs), a class of carotenoid-derived plant hormones. Substantial progress has since been made towards understanding how KARs are perceived and regulate plant growth, in no small part due to advances in understanding SL perception. KAR and SL signalling systems are evolutionarily related and retain a high degree of similarity. There is strong evidence that KARs are natural analogues of an endogenous signal(s), KAI2 ligand (KL), which remains unknown. KAR/KL signalling regulates many developmental processes in plants including germination, seedling photomorphogenesis, and root and root hair growth. KAR/KL signalling also affects abiotic stress responses and arbuscular mycorrhizal symbiosis. Here, we summarise the current knowledge of KAR/KL signalling and discuss current controversies and unanswered questions in this field.
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Affiliation(s)
- Mark T Waters
- School of Molecular Sciences, University of Western Australia, Perth, WA, 6009, Australia
| | - David C Nelson
- Department of Botany and Plant Sciences, University of California, Riverside, CA, 92521, USA
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