1
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Guercio AM, Gilio AK, Pawlak J, Shabek N. Structural insights into rice KAI2 receptor provide functional implications for perception and signal transduction. J Biol Chem 2024:107593. [PMID: 39032651 DOI: 10.1016/j.jbc.2024.107593] [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: 05/12/2024] [Revised: 07/10/2024] [Accepted: 07/12/2024] [Indexed: 07/23/2024] Open
Abstract
KAI2 receptors, classified as plant α/β hydrolase enzymes, are capable of perceiving smoke-derived butenolide signals and endogenous, yet unidentified KAI2-ligands (KLs). While the number of functional KAI2 receptors varies among land plant species, rice has only one KAI2 gene. Rice, a significant crop and representative of grasses, relies on KAI2-mediated Arbuscular mycorrhiza (AM) symbioses to flourish in traditionally arid and nutrient-poor environments. This study presents the first crystal structure of an active rice (Oryza sativa, Os) KAI2 hydrolase receptor. Our structural and biochemical analyses uncover grass-unique pocket residues influencing ligand sensitivity and hydrolytic activity. Through structure-guided analysis, we identify a specific residue whose mutation enables the increase or decrease of ligand perception, catalytic activity, and signal transduction. Furthermore, we investigate OsKAI2-mediated signaling by examining its ability to form a complex with its binding partner, the F-box protein DWARF3 (D3) ubiquitin ligase and subsequent degradation of the target substrate OsSMAX1, demonstrating the significant role of hydrophobic interactions in the OsKAI2-D3 interface. This study provides new insights into the diverse and pivotal roles of the OsKAI2 signaling pathway in the plant kingdom, particularly in grasses.
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Affiliation(s)
- Angelica M Guercio
- Department of Plant Biology, The College of Biological Sciences, University of California - Davis, Davis, CA 95616
| | - Amelia K Gilio
- Department of Plant Biology, The College of Biological Sciences, University of California - Davis, Davis, CA 95616
| | - Jacob Pawlak
- Department of Plant Biology, The College of Biological Sciences, University of California - Davis, Davis, CA 95616
| | - Nitzan Shabek
- Department of Plant Biology, The College of Biological Sciences, University of California - Davis, Davis, CA 95616.
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2
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Park YJ, Nam BE, Park CM. Environmentally adaptive reshaping of plant photomorphogenesis by karrikin and strigolactone signaling. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2024; 66:865-882. [PMID: 38116738 DOI: 10.1111/jipb.13602] [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: 08/06/2023] [Revised: 12/09/2023] [Accepted: 12/18/2023] [Indexed: 12/21/2023]
Abstract
Coordinated morphogenic adaptation of growing plants is critical for their survival and propagation under fluctuating environments. Plant morphogenic responses to light and warm temperatures, termed photomorphogenesis and thermomorphogenesis, respectively, have been extensively studied in recent decades. During photomorphogenesis, plants actively reshape their growth and developmental patterns to cope with changes in light regimes. Accordingly, photomorphogenesis is closely associated with diverse growth hormonal cues. Notably, accumulating evidence indicates that light-directed morphogenesis is profoundly affected by two recently identified phytochemicals, karrikins (KARs) and strigolactones (SLs). KARs and SLs are structurally related butenolides acting as signaling molecules during a variety of developmental steps, including seed germination. Their receptors and signaling mediators have been identified, and associated working mechanisms have been explored using gene-deficient mutants in various plant species. Of particular interest is that the KAR and SL signaling pathways play important roles in environmental responses, among which their linkages with photomorphogenesis are most comprehensively studied during seedling establishment. In this review, we focus on how the phytochemical and light signals converge on the optimization of morphogenic fitness. We also discuss molecular mechanisms underlying the signaling crosstalks with an aim of developing potential ways to improve crop productivity under climate changes.
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Affiliation(s)
- Young-Joon Park
- Department of Smart Farm Science, Kyung Hee University, Yongin, 17104, Korea
| | - Bo Eun Nam
- Department of Biological Sciences, Seoul National University, Seoul, 08826, Korea
| | - Chung-Mo Park
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea
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3
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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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4
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Martinez SE, Conn CE, Guercio AM, Sepulveda C, Fiscus CJ, Koenig D, Shabek N, Nelson DC. A KARRIKIN INSENSITIVE2 paralog in lettuce mediates highly sensitive germination responses to karrikinolide. PLANT PHYSIOLOGY 2022; 190:1440-1456. [PMID: 35809069 PMCID: PMC9516758 DOI: 10.1093/plphys/kiac328] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 05/26/2022] [Indexed: 06/15/2023]
Abstract
Karrikins (KARs) are chemicals in smoke that can enhance germination of many plants. Lettuce (Lactuca sativa) cv. Grand Rapids germinates in response to nanomolar karrikinolide (KAR1). Lettuce is much less responsive to KAR2 or a mixture of synthetic strigolactone analogs, rac-GR24. We investigated the molecular basis of selective and sensitive KAR1 perception in lettuce. The lettuce genome contains two copies of KARRIKIN INSENSITIVE2 (KAI2), which in Arabidopsis (Arabidopsis thaliana) encodes a receptor that is required for KAR responses. LsKAI2b is more highly expressed than LsKAI2a in dry achenes and during early stages of imbibition. Through cross-species complementation assays in Arabidopsis, we found that an LsKAI2b transgene confers robust responses to KAR1, but LsKAI2a does not. Therefore, LsKAI2b likely mediates KAR1 responses in lettuce. We compared homology models of KAI2 proteins from lettuce and a fire-follower, whispering bells (Emmenanthe penduliflora). This identified pocket residues 96, 124, 139, and 161 as candidates that influence the ligand specificity of KAI2. Further support for the importance of these residues was found through a broader comparison of pocket residues among 281 KAI2 proteins from 184 asterid species. Almost all KAI2 proteins had either Tyr or Phe identity at position 124. Genes encoding Y124-type KAI2 are more broadly distributed in asterids than in F124-type KAI2. Substitutions at residues 96, 124, 139, and 161 in Arabidopsis KAI2 produced a broad array of responses to KAR1, KAR2, and rac-GR24. This suggests that the diverse ligand preferences observed among KAI2 proteins in plants could have evolved through relatively few mutations.
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Affiliation(s)
- Stephanie E Martinez
- Department of Botany and Plant Sciences, University of California, Riverside, California 92521, USA
| | - Caitlin E Conn
- Department of Biology, Berry College, Mount Berry, Georgia 30149, USA
| | - Angelica M Guercio
- Department of Plant Biology, University of California, Davis, California 95616, USA
| | - Claudia Sepulveda
- Department of Botany and Plant Sciences, University of California, Riverside, California 92521, USA
| | - Christopher J Fiscus
- Department of Botany and Plant Sciences, University of California, Riverside, California 92521, USA
| | - Daniel Koenig
- Department of Botany and Plant Sciences, University of California, Riverside, California 92521, USA
| | - Nitzan Shabek
- Department of Plant Biology, University of California, Davis, California 95616, USA
| | - David C Nelson
- Department of Botany and Plant Sciences, University of California, Riverside, California 92521, USA
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5
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Park YJ, Kim JY, Park CM. SMAX1 potentiates phytochrome B-mediated hypocotyl thermomorphogenesis. THE PLANT CELL 2022; 34:2671-2687. [PMID: 35478037 PMCID: PMC9252492 DOI: 10.1093/plcell/koac124] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 03/16/2022] [Indexed: 05/19/2023]
Abstract
Plant thermosensors help optimize plant development and architecture for ambient temperatures, and morphogenic adaptation to warm temperatures has been extensively studied in recent years. Phytochrome B (phyB)-mediated thermosensing and the gene regulatory networks governing thermomorphogenic responses are well understood at the molecular level. However, it is unknown how plants manage their responsiveness to fluctuating temperatures in inducing thermomorphogenic behaviors. Here, we demonstrate that SUPPRESSOR OF MAX2 1 (SMAX1), known as a karrikin signaling repressor, enhances the thermosensitivity of hypocotyl morphogenesis in Arabidopsis thaliana. Hypocotyl thermomorphogenesis was largely disrupted in SMAX1-deficient mutants. SMAX1 interacts with phyB to alleviate its suppressive effects on the transcription factor activity of PHYTOCHROME-INTERACTING FACTOR 4 (PIF4), promoting hypocotyl thermomorphogenesis. Interestingly, the SMAX1 protein is slowly destabilized at warm temperatures, preventing hypocotyl overgrowth. Our findings indicate that the thermodynamic control of SMAX1 abundance serves as a molecular gatekeeper for phyB function in thermosensitizing PIF4-mediated hypocotyl morphogenesis.
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Affiliation(s)
- Young-Joon Park
- Department of Chemistry, Seoul National University, Seoul 08826, Korea
| | - Jae Young Kim
- Department of Chemistry, Seoul National University, Seoul 08826, Korea
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6
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Liu X, Zhang J. In Silico Investigation on KAR Signaling Reveals the Significant Dynamic Change of Its Receptor's Structure. J Chem Inf Model 2022; 62:1933-1941. [PMID: 35389657 DOI: 10.1021/acs.jcim.2c00004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Karrikins (KARs) have been identified as a class of smoke-derived plant growth regulators widely functioning among angiosperms. However, little is known about the mechanism by which these molecules trigger the relevant signal transduction. In this research, conventional molecular dynamics simulations were used to investigate the dynamical behavior of the apo- and holo-forms of the KAR receptor KAI2. The results show that the dynamic binding conformation of KAR1 in the active site is not completely consistent with that in the static crystal and is largely affected by the residue segment of the receptor, Tyr150-Asn180. The binding of the ligand with KAI2 changes the distribution of the electrostatic potential near the active site and drives the conformational transition of the Tyr150-Asn180 segment with strong internal positive correlation. A "dual induction" signaling mechanism is proposed in view of the present calculations. Our work paves way for in-depth understanding of the KAR signal transduction mechanism and sheds light on further experimental and theoretical exploration.
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Affiliation(s)
- Xiaoting Liu
- Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun 130023, Jilin, People's Republic of China.,College of Food Science and Engineering, National Engineering Laboratory of Wheat and Corn Deep Processing, Jilin Agricultural University, Changchun 130118, Jilin, People's Republic of China
| | - Jilong Zhang
- Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun 130023, Jilin, People's Republic of China
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7
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Sepulveda C, Guzmán MA, Li Q, Villaécija-Aguilar JA, Martinez SE, Kamran M, Khosla A, Liu W, Gendron JM, Gutjahr C, Waters MT, Nelson DC. KARRIKIN UP-REGULATED F-BOX 1 (KUF1) imposes negative feedback regulation of karrikin and KAI2 ligand metabolism in Arabidopsis thaliana. Proc Natl Acad Sci U S A 2022; 119:e2112820119. [PMID: 35254909 PMCID: PMC8931227 DOI: 10.1073/pnas.2112820119] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 01/28/2022] [Indexed: 12/13/2022] Open
Abstract
SignificanceKarrikins are chemicals in smoke that stimulate regrowth of many plants after fire. However, karrikin responses are not limited to species from fire-prone environments and can affect growth after germination. Putatively, this is because karrikins mimic an unknown signal in plants, KAI2 ligand (KL). Karrikins likely require modification in plants to become bioactive. We identify a gene, KUF1, that appears to negatively regulate biosynthesis of KL and metabolism of a specific karrikin. KUF1 expression increases in response to karrikin or KL signaling, thus forming a negative feedback loop that limits further activation of the signaling pathway. This discovery will advance understanding of how karrikins are perceived and how smoke-activated germination evolved. It will also aid identification of the elusive KL.
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Affiliation(s)
- Claudia Sepulveda
- Department of Botany and Plant Sciences, University of California, Riverside, CA 92521
| | - Michael A. Guzmán
- Department of Botany and Plant Sciences, University of California, Riverside, CA 92521
| | - Qingtian Li
- Department of Botany and Plant Sciences, University of California, Riverside, CA 92521
| | | | - Stephanie E. Martinez
- Department of Botany and Plant Sciences, University of California, Riverside, CA 92521
| | - Muhammad Kamran
- School of Molecular Sciences, University of Western Australia, Perth, WA 6009, Australia
| | - Aashima Khosla
- Department of Botany and Plant Sciences, University of California, Riverside, CA 92521
| | - Wei Liu
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06511
| | - Joshua M. Gendron
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06511
| | - Caroline Gutjahr
- Plant Genetics, TUM School of Life Sciences, Technical University of Munich, Freising, 85354 Germany
| | - 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
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8
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Meng Y, Varshney K, Incze N, Badics E, Kamran M, Davies SF, Oppermann LMF, Magne K, Dalmais M, Bendahmane A, Sibout R, Vogel J, Laudencia-Chingcuanco D, Bond CS, Soós V, Gutjahr C, Waters MT. KARRIKIN INSENSITIVE2 regulates leaf development, root system architecture and arbuscular-mycorrhizal symbiosis in Brachypodium distachyon. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 109:1559-1574. [PMID: 34953105 DOI: 10.1111/tpj.15651] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 12/20/2021] [Indexed: 06/14/2023]
Abstract
KARRIKIN INSENSITIVE2 (KAI2) is an α/β-hydrolase required for plant responses to karrikins, which are abiotic butenolides that can influence seed germination and seedling growth. Although represented by four angiosperm species, loss-of-function kai2 mutants are phenotypically inconsistent and incompletely characterised, resulting in uncertainties about the core functions of KAI2 in plant development. Here we characterised the developmental functions of KAI2 in the grass Brachypodium distachyon using molecular, physiological and biochemical approaches. Bdkai2 mutants exhibit increased internode elongation and reduced leaf chlorophyll levels, but only a modest increase in water loss from detached leaves. Bdkai2 shows increased numbers of lateral roots and reduced root hair growth, and fails to support normal root colonisation by arbuscular-mycorrhizal (AM) fungi. The karrikins KAR1 and KAR2 , and the strigolactone (SL) analogue rac-GR24, each elicit overlapping but distinct changes to the shoot transcriptome via BdKAI2. Finally, we show that BdKAI2 exhibits a clear ligand preference for desmethyl butenolides and weak responses to methyl-substituted SL analogues such as GR24. Our findings suggest that KAI2 has multiple roles in shoot development, root system development and transcriptional regulation in grasses. Although KAI2-dependent AM symbiosis is likely conserved within monocots, the magnitude of the effect of KAI2 on water relations may vary across angiosperms.
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Affiliation(s)
- Yongjie Meng
- School of Molecular Sciences, The University of Western Australia, Perth, WA, 6009, Australia
- College of Agronomy, Sichuan Agricultural University, Chengdu, 611130, China
| | - Kartikye Varshney
- Plant Genetics, TUM School of Life Sciences, Technical University of Munich, Freising, 85354, Germany
| | - Norbert Incze
- Department of Biological Resources, Agricultural Institute, Centre for Agricultural Research, Martonvásár, 2462, Hungary
- Doctoral School of Biology, Institute of Biology, ELTE Eötvös Loránd University, Budapest, 1117, Hungary
| | - Eszter Badics
- Department of Biological Resources, Agricultural Institute, Centre for Agricultural Research, Martonvásár, 2462, Hungary
- Doctoral School of Biology, Institute of Biology, ELTE Eötvös Loránd University, Budapest, 1117, Hungary
| | - Muhammad Kamran
- School of Molecular Sciences, The University of Western Australia, Perth, WA, 6009, Australia
| | - Sabrina F Davies
- School of Molecular Sciences, The University of Western Australia, Perth, WA, 6009, Australia
| | - Larissa M F Oppermann
- School of Molecular Sciences, The University of Western Australia, Perth, WA, 6009, Australia
| | - Kévin Magne
- Université Paris-Saclay, CNRS, INRAE, Univ Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Orsay, 91405, France
- Université de Paris, CNRS, INRAE, Institute of Plant Sciences Paris-Saclay (IPS2), Orsay, 91405, France
| | - Marion Dalmais
- Université Paris-Saclay, CNRS, INRAE, Univ Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Orsay, 91405, France
- Université de Paris, CNRS, INRAE, Institute of Plant Sciences Paris-Saclay (IPS2), Orsay, 91405, France
| | - Abdel Bendahmane
- Université Paris-Saclay, CNRS, INRAE, Univ Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Orsay, 91405, France
- Université de Paris, CNRS, INRAE, Institute of Plant Sciences Paris-Saclay (IPS2), Orsay, 91405, France
| | - Richard Sibout
- Institut Jean-Pierre Bourgin, UMR1318 INRAE-AgroParisTech, Versailles Cedex, F-78026, France
- UR1268 BIA, INRAE, Nantes, 44300, France
| | - John Vogel
- DOE Joint Genome Institute, Berkeley, California, 94720, USA
| | | | - Charles S Bond
- School of Molecular Sciences, The University of Western Australia, Perth, WA, 6009, Australia
| | - Vilmos Soós
- Department of Biological Resources, Agricultural Institute, Centre for Agricultural Research, Martonvásár, 2462, Hungary
| | - Caroline Gutjahr
- Plant Genetics, TUM School of Life Sciences, Technical University of Munich, Freising, 85354, Germany
| | - Mark T Waters
- School of Molecular Sciences, The University of Western Australia, Perth, WA, 6009, Australia
- College of Agronomy, Sichuan Agricultural University, Chengdu, 611130, China
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9
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Chen J, Nelson DC, Shukla D. Activation Mechanism of Strigolactone Receptors and Its Impact on Ligand Selectivity between Host and Parasitic Plants. J Chem Inf Model 2022; 62:1712-1722. [PMID: 35192364 DOI: 10.1021/acs.jcim.1c01258] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Parasitic weeds such as Striga have led to significant losses in agricultural productivity worldwide. These weeds use the plant hormone strigolactone as a germination stimulant. Strigolactone signaling involves substrate hydrolysis followed by a conformational change of the receptor to a "closed" or "active" state that associates with a signaling partner, MAX2/D3. Crystal structures of active and inactive AtD14 receptors have helped elucidate the structural changes involved in activation. However, the mechanism by which the receptor activates remains unknown. The ligand dependence of AtD14 activation has been disputed by mutagenesis studies showing that enzymatically inactive receptors are able to associate with MAX2 proteins. Furthermore, activation differences between strigolactone receptor in Striga, ShHTL7, and AtD14 could contribute to the high sensitivity to strigolactones exhibited by parasitic plants. Using molecular dynamics simulations, we demonstrate that both AtD14 and ShHTL7 could adopt an active conformation in the absence of ligand. However, ShHTL7 exhibits a higher population in the inactive apo state as compared to the AtD14 receptor. We demonstrate that this difference in inactive state population is caused by sequence differences between their D-loops and interactions with the catalytic histidine that prevent full binding pocket closure in ShHTL7. These results indicate that ligand hydrolysis would enhance the active state population by destabilizing the inactive state in ShHTL7 as compared to AtD14. We also show that the mechanism of activation is more concerted in AtD14 than in ShHTL7 and that the main barrier to activation in ShHTL7 is closing of the binding pocket.
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Affiliation(s)
- Jiming Chen
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - David C Nelson
- Department of Botany and Plant Sciences, University of California, Riverside, Riverside, California 92521, United States
| | - Diwakar Shukla
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,NIH Center for Macromolecular Modeling and Bioinformatics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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10
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Guercio AM, Torabi S, Cornu D, Dalmais M, Bendahmane A, Le Signor C, Pillot JP, Le Bris P, Boyer FD, Rameau C, Gutjahr C, de Saint Germain A, Shabek N. Structural and functional analyses explain Pea KAI2 receptor diversity and reveal stereoselective catalysis during signal perception. Commun Biol 2022; 5:126. [PMID: 35149763 PMCID: PMC8837635 DOI: 10.1038/s42003-022-03085-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 01/28/2022] [Indexed: 11/10/2022] Open
Abstract
KAI2 proteins are plant α/β hydrolase receptors which perceive smoke-derived butenolide signals and endogenous, yet unidentified KAI2-ligands (KLs). The number of functional KAI2 receptors varies among species and KAI2 gene duplication and sub-functionalization likely plays an adaptative role by altering specificity towards different KLs. Legumes represent one of the largest families of flowering plants and contain many agronomic crops. Prior to their diversification, KAI2 underwent duplication resulting in KAI2A and KAI2B. Here we demonstrate that Pisum sativum KAI2A and KAI2B are active receptors and enzymes with divergent ligand stereoselectivity. KAI2B has a higher affinity for and hydrolyses a broader range of substrates including strigolactone-like stereoisomers. We determine the crystal structures of PsKAI2B in apo and butenolide-bound states. The biochemical, structural, and mass spectra analyses of KAI2s reveal a transient intermediate on the catalytic serine and a stable adduct on the catalytic histidine, confirming its role as a bona fide enzyme. Our work uncovers the stereoselectivity of ligand perception and catalysis by diverged KAI2 receptors and proposes adaptive sensitivity to KAR/KL and strigolactones by KAI2B.
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Affiliation(s)
- Angelica M Guercio
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA, 95616, USA
| | - Salar Torabi
- Plant Genetics, TUM School of Life Sciences, Technical University of Munich (TUM), 85354, Freising, Germany
| | - David Cornu
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Marion Dalmais
- Institute of Plant Sciences Paris-Saclay, INRAE, CNRS, Université Paris-Saclay, 91405, Orsay, France
| | - Abdelhafid Bendahmane
- Institute of Plant Sciences Paris-Saclay, INRAE, CNRS, Université Paris-Saclay, 91405, Orsay, France
| | - Christine Le Signor
- Agroecologie, AgroSup Dijon, INRAE, Université Bourgogne Franche Comte, 21000, Dijon, France
| | - Jean-Paul Pillot
- Institut Jean-Pierre Bourgin, INRAE, AgroParisTech, Université Paris-Saclay, 78000, Versailles, France
| | - Philippe Le Bris
- Institut Jean-Pierre Bourgin, INRAE, AgroParisTech, Université Paris-Saclay, 78000, Versailles, France
| | - François-Didier Boyer
- Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, 91198, Gif-sur-Yvette, France
| | - Catherine Rameau
- Institut Jean-Pierre Bourgin, INRAE, AgroParisTech, Université Paris-Saclay, 78000, Versailles, France
| | - Caroline Gutjahr
- Plant Genetics, TUM School of Life Sciences, Technical University of Munich (TUM), 85354, Freising, Germany
| | | | - Nitzan Shabek
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA, 95616, USA.
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11
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Nelson DC. The mechanism of host-induced germination in root parasitic plants. PLANT PHYSIOLOGY 2021; 185:1353-1373. [PMID: 33793958 PMCID: PMC8133615 DOI: 10.1093/plphys/kiab043] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 01/25/2021] [Indexed: 05/25/2023]
Abstract
Chemical signals known as strigolactones (SLs) were discovered more than 50 years ago as host-derived germination stimulants of parasitic plants in the Orobanchaceae. Strigolactone-responsive germination is an essential adaptation of obligate parasites in this family, which depend upon a host for survival. Several species of obligate parasites, including witchweeds (Striga, Alectra spp.) and broomrapes (Orobanche, Phelipanche spp.), are highly destructive agricultural weeds that pose a significant threat to global food security. Understanding how parasites sense SLs and other host-derived stimulants will catalyze the development of innovative chemical and biological control methods. This review synthesizes the recent discoveries of strigolactone receptors in parasitic Orobanchaceae, their signaling mechanism, and key steps in their evolution.
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Affiliation(s)
- David C Nelson
- Department of Botany and Plant Sciences, University of California, Riverside, CA 92521 USA
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12
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A Raf-like kinase is required for smoke-induced seed dormancy in Arabidopsis thaliana. Proc Natl Acad Sci U S A 2021; 118:2020636118. [PMID: 33795513 DOI: 10.1073/pnas.2020636118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Plants sense and integrate diverse stimuli to determine the timing for germination. A smoke compound, 3,4,5-trimethylfuran-2(5H)-one (trimethylbutenolide, TMB), has been identified to inhibit the seed germination of higher plants. To understand the mode of action, we examined various physiological and molecular aspects of the TMB-dependent inhibition of seed germination in Arabidopsis thaliana The results indicated that the effect of TMB is due to the enhanced physiological dormancy, which is modulated by other dormancy regulatory cues such as after-ripening, stratification, and ABA/GA signaling. In addition, gene expression profiling showed that TMB caused genome-wide transcriptional changes, altering the expression of a series of dormancy-related genes. Based on the TMB-responsive physiological contexts in Arabidopsis, we performed mutant screening to isolate genetic components that underpin the TMB-induced seed dormancy. As a result, the TMB-RESISTANT1 (TES1) gene in Arabidopsis, encoding a B2 group Raf-like kinase, was identified. Phenotypic analysis of the tes1 mutant implicated that TES1 has a critical role in the TMB-responsive gene expression and the inhibition of seed germination. Taken together, we propose that plants have been equipped with a TMB sensory pathway through which the TMB induces the seed dormancy in a TES1-dependent way.
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13
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Zhang JL, Liu X, Zhang HX. Interaction Mechanism of the Germination Stimulants Karrikins and Their Receptor ShKAI2iB. J Phys Chem B 2020; 124:9812-9819. [PMID: 33089685 DOI: 10.1021/acs.jpcb.0c06734] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The significance of karrikins (KARs) in plant physiology opens a door for their application in the agricultural production. As the first event of the whole signaling pathway, the binding of smoke-derived signal molecules KARs to the receptor protein KAI2 triggers the germination of the primary dormant seeds of all angiosperms, not just the "fire-prone" taxa. In the present study, all-atom molecular dynamics simulations, along with the accurate estimation of the ligand-receptor binding free energy, were used to investigate the atomic level interaction of all the members of the KARs family (from KAR1 to KAR6) with the receptor ShKAI2iB, an intermediate-evolving KAI2 from Striga hermonthica. The calculated binding energy value of KAR1 to ShKAI2iB, -5.64 kcal/mol, is in good agreement with the available experimental data, -5.67 kcal/mol. The further analysis of the detailed interaction between each KAR and the protein reveals the primary reasons for the difference of the affinity of the diverse ligands with the receptor and displays the regional characteristics of the protein's active site. Our research will not only provide clues for the study of equivalent endogenous phytohormone, but also contribute to the development of synthetic germinating chemicals.
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Affiliation(s)
- Ji-Long Zhang
- International Joint Research Laboratory of Nano-Micro Architecture Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, Jilin, People's Republic of China
| | - Xiaoting Liu
- College of Food Science and Engineering, National Engineering Laboratory of Wheat and Corn Deep Processing, Jilin Agricultural University, Changchun 130118, Jilin, People's Republic of China
| | - Hong-Xing Zhang
- International Joint Research Laboratory of Nano-Micro Architecture Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, Jilin, People's Republic of China
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14
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Khosla A, Morffy N, Li Q, Faure L, Chang SH, Yao J, Zheng J, Cai ML, Stanga J, Flematti GR, Waters MT, Nelson DC. Structure-Function Analysis of SMAX1 Reveals Domains That Mediate Its Karrikin-Induced Proteolysis and Interaction with the Receptor KAI2. THE PLANT CELL 2020; 32:2639-2659. [PMID: 32434855 PMCID: PMC7401016 DOI: 10.1105/tpc.19.00752] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 04/13/2020] [Accepted: 05/14/2020] [Indexed: 05/18/2023]
Abstract
Karrikins (KARs) are butenolides found in smoke that can influence germination and seedling development of many plants. The KAR signaling mechanism is hypothesized to be very similar to that of the plant hormone strigolactone (SL). Both pathways require the F-box protein MORE AXILLARY GROWTH2 (MAX2), and other core signaling components have shared ancestry. Putatively, KAR activates the receptor KARRIKIN INSENSITIVE2 (KAI2), triggering its association with the E3 ubiquitin ligase complex SCFMAX2 and downstream targets SUPPRESSOR OF MAX2 1 (SMAX1) and SMAX1-LIKE2 (SMXL2). Polyubiquitination and proteolysis of SMAX1 and SMXL2 then enable growth responses to KAR. However, many of the assumptions of this model have not been demonstrated. Therefore, we investigated the posttranslational regulation of SMAX1 from the model plant Arabidopsis (Arabidopsis thaliana). We find evidence that SMAX1 is degraded by KAI2-SCFMAX2 but is also subject to MAX2-independent turnover. We identify SMAX1 domains that are responsible for its nuclear localization, KAR-induced degradation, association with KAI2, and ability to interact with other SMXL proteins. KAI2 undergoes MAX2-independent degradation after KAR treatment, which we propose results from its association with SMAX1 and SMXL2. Finally, we discover an SMXL domain that mediates receptor-target interaction preferences in KAR and SL signaling, laying the foundation for understanding how these highly similar pathways evolved to fulfill different roles.
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Affiliation(s)
- Aashima Khosla
- Department of Botany and Plant Sciences, University of California, Riverside, California 92521
| | - Nicholas Morffy
- Department of Genetics, University of Georgia, Athens, Georgia 30602
| | - Qingtian Li
- Department of Botany and Plant Sciences, University of California, Riverside, California 92521
| | - Lionel Faure
- Department of Genetics, University of Georgia, Athens, Georgia 30602
- Department of Biology, Texas Woman's University, Denton, Texas 76204
| | - Sun Hyun Chang
- Department of Botany and Plant Sciences, University of California, Riverside, California 92521
| | - Jiaren Yao
- School of Molecular Sciences, University of Western Australia Perth, Crawley, Western Australia 6009, Australia
- Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia Perth, Crawley, Western Australia 6009, Australia
| | - Jiameng Zheng
- Department of Botany and Plant Sciences, University of California, Riverside, California 92521
| | - Mei L Cai
- Department of Botany and Plant Sciences, University of California, Riverside, California 92521
| | - John Stanga
- Department of Genetics, University of Georgia, Athens, Georgia 30602
- Department of Biology, Mercer University, Macon, Georgia 31207
| | - Gavin R Flematti
- School of Molecular Sciences, University of Western Australia Perth, Crawley, Western Australia 6009, Australia
| | - Mark T Waters
- School of Molecular Sciences, University of Western Australia Perth, Crawley, Western Australia 6009, Australia
- Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia Perth, Crawley, Western Australia 6009, Australia
| | - David C Nelson
- Department of Botany and Plant Sciences, University of California, Riverside, California 92521
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15
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Yao J, Waters MT. Perception of karrikins by plants: a continuing enigma. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:1774-1781. [PMID: 31836893 PMCID: PMC7242065 DOI: 10.1093/jxb/erz548] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 12/09/2019] [Indexed: 05/28/2023]
Abstract
Karrikins are small butenolide molecules with the capacity to promote germination and enhance seedling establishment. Generated abiotically from partial combustion of vegetation, karrikins are comparatively rare in the environment, but studying their mode of action has been most informative in revealing a new regulatory pathway for plant development that uses the karrikin perception machinery. Recent studies suggest that the karrikin receptor protein KAI2 and downstream transcriptional co-repressors in the SMXL family influence seed germination, seedling photomorphogenesis, root morphology, and responses to abiotic stress such as drought. Based on taxonomic distribution, this pathway is ubiquitous and likely to be evolutionarily ancient, originating prior to land plants. However, we still do not have a good grasp on how karrikins actually activate the receptor protein, and we have yet to discover the assumed endogenous ligand for KAI2 that karrikins are thought to mimic. This review covers recent progress in this field, as well as current gaps in our knowledge.
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Affiliation(s)
- Jiaren Yao
- School of Molecular Sciences, The University of Western Australia, Perth, WA, Australia
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16
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Divergent receptor proteins confer responses to different karrikins in two ephemeral weeds. Nat Commun 2020; 11:1264. [PMID: 32152287 PMCID: PMC7062792 DOI: 10.1038/s41467-020-14991-w] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 02/12/2020] [Indexed: 11/08/2022] Open
Abstract
Wildfires can encourage the establishment of invasive plants by releasing potent germination stimulants, such as karrikins. Seed germination of Brassica tournefortii, a noxious weed of Mediterranean climates, is strongly stimulated by KAR1, the archetypal karrikin produced from burning vegetation. In contrast, the closely-related yet non-fire-associated ephemeral Arabidopsisthaliana is unusual because it responds preferentially to KAR2. The α/β-hydrolase KARRIKIN INSENSITIVE 2 (KAI2) is the putative karrikin receptor identified in Arabidopsis. Here we show that B. tournefortii expresses three KAI2 homologues, and the most highly-expressed homologue is sufficient to confer enhanced responses to KAR1 relative to KAR2 when expressed in Arabidopsis. We identify two amino acid residues near the KAI2 active site that explain the ligand selectivity, and show that this combination has arisen independently multiple times within dicots. Our results suggest that duplication and diversification of KAI2 proteins could confer differential responses to chemical cues produced by environmental disturbance, including fire. Karrikins are germination stimulants perceived by KAI2 in Arabidopsis. Here the authors show that Brassica tournefortii, a close relative to Arabidopsis, has multiple copies of KAI2 with amino acid substitutions that confer responsiveness to the specific karrikin compounds found in wildfire smoke.
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17
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Machin DC, Hamon-Josse M, Bennett T. Fellowship of the rings: a saga of strigolactones and other small signals. THE NEW PHYTOLOGIST 2020; 225:621-636. [PMID: 31442309 DOI: 10.1111/nph.16135] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2019] [Accepted: 08/08/2019] [Indexed: 05/25/2023]
Abstract
Strigolactones are an important class of plant signalling molecule with both external rhizospheric and internal hormonal functions in flowering plants. The past decade has seen staggering progress in strigolactone biology, permitting highly detailed understanding of their signalling, synthesis and biological roles - or so it seems. However, phylogenetic analyses show that strigolactone signalling mediated by the D14-SCFMAX2 -SMXL7 complex is only one of a number of closely related signalling pathways, and is much less ubiquitous in land plants than might be expected. The existence of closely related pathways, such as the KAI2-SMAX1 module, challenges many of our assumptions about strigolactones, and in particular emphasises how little we understand about the specificity of strigolactone signalling with respect to related signalling pathways. In this review, we examine recent advances in strigolactone signalling, taking a holistic evolutionary view to identify the ambiguities and uncertainties in our understanding. We highlight that while we now have highly detailed molecular models for the core mechanism of D14-SMXL7 signalling, we still do not understand the ligand specificity of D14, the specificity of its interaction with SMXL7, nor the specificity of SMXL7 function. Our analysis therefore identifies key areas requiring further study.
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Affiliation(s)
- Darren C Machin
- School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Maxime Hamon-Josse
- School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Tom Bennett
- School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
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18
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Potential of Karrikins as Novel Plant Growth Regulators in Agriculture. PLANTS 2019; 9:plants9010043. [PMID: 31888087 PMCID: PMC7020145 DOI: 10.3390/plants9010043] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 12/19/2019] [Accepted: 12/24/2019] [Indexed: 01/30/2023]
Abstract
Karrikins (KARs) have been identified as molecules derived from plant material smoke, which have the capacity to enhance seed germination for a wide range of plant species. However, KARs were observed to not only impact seed germination but also observed to influence several biological processes. The plants defected in the KARs signaling pathway were observed to grow differently with several morphological changes. The observation of KARs as a growth regulator in plants leads to the search for an endogenous KAR-like molecule. Due to its simple genomic structure, Arabidopsis (Arabidopsis thaliana L.) helps to understand the signaling mechanism of KARs and phenotypic responses caused by them. However, different species have a different phenotypic response to KARs treatment. Therefore, in the current work, updated information about the KARs effect is presented. Results of research on agricultural and horticultural crops are summarized and compared with the findings of Arabidopsis studies. In this article, we suggested that KARs may be more important in coping with modern problems than one could imagine.
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19
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Swarbreck SM, Guerringue Y, Matthus E, Jamieson FJC, Davies JM. Impairment in karrikin but not strigolactone sensing enhances root skewing in Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2019; 98:607-621. [PMID: 30659713 PMCID: PMC6563046 DOI: 10.1111/tpj.14233] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 12/20/2018] [Accepted: 01/08/2019] [Indexed: 05/20/2023]
Abstract
Roots form highly complex systems varying in growth direction and branching pattern to forage for nutrients efficiently. Here mutations in the KAI2 (KARRIKIN INSENSITIVE) α/β-fold hydrolase and the MAX2 (MORE AXILLARY GROWTH 2) F-box leucine-rich protein, which together perceive karrikins (smoke-derived butenolides), caused alteration in root skewing in Arabidopsis thaliana. This phenotype was independent of endogenous strigolactones perception by the D14 α/β-fold hydrolase and MAX2. Thus, KAI2/MAX2 effect on root growth may be through the perception of endogenous KAI2-ligands (KLs), which have yet to be identified. Upon perception of a ligand, a KAI2/MAX2 complex is formed together with additional target proteins before ubiquitination and degradation through the 26S proteasome. Using a genetic approach, we show that SMAX1 (SUPPRESSOR OF MAX2-1)/SMXL2 and SMXL6,7,8 (SUPPRESSOR OF MAX2-1-LIKE) are also likely degradation targets for the KAI2/MAX2 complex in the context of root skewing. In A. thaliana therefore, KAI2 and MAX2 act to limit root skewing, while kai2's gravitropic and mechano-sensing responses remained largely unaffected. Many proteins are involved in root skewing, and we investigated the link between MAX2 and two members of the SKS/SKU family. Though KLs are yet to be identified in plants, our data support the hypothesis that they are present and can affect root skewing.
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Affiliation(s)
| | - Yannick Guerringue
- Department of Plant SciencesUniversity of CambridgeCambridgeCB2 3EAUK
- ENS de Lyon ‐ Site MonodLyon69007France
| | - Elsa Matthus
- Department of Plant SciencesUniversity of CambridgeCambridgeCB2 3EAUK
| | - Fiona J. C. Jamieson
- Department of Plant SciencesUniversity of CambridgeCambridgeCB2 3EAUK
- Department of Plant SciencesUniversity of OxfordSouth Parks RoadOxfordOX1 3RBUK
| | - Julia M. Davies
- Department of Plant SciencesUniversity of CambridgeCambridgeCB2 3EAUK
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20
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Hu F, Liu XT, Zhang JL, Zheng QC, Eglitis RI, Zhang HX. MD Simulation Investigation on the Binding Process of Smoke-Derived Germination Stimulants to Its Receptor. J Chem Inf Model 2019; 59:1554-1562. [PMID: 30884225 DOI: 10.1021/acs.jcim.8b00844] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Karrikins (KARs) are a class of smoke-derived seed germination stimulants with great significance in both agriculture and plant biology. By means of direct binding to the receptor protein KAI2, the compounds can initiate the KAR signal transduction pathway, hence triggering germination of the dormant seeds in the soil. In the research, several molecular dynamics (MD) simulation techniques were properly integrated to investigate the binding process of KAR1 to KAI2 and reveal the details of the whole binding event. The calculated binding free energy, -7.00 kcal/mol, is in good agreement with the experimental measurement, -6.83 kcal/mol. The obtained PMF profile indicates the existence of three intermediate states in the binding process. The analysis of the simulation trajectories demonstrates that, in the intermediate structures, KAR1 is stabilized by some hydrophobic residues (Phe26, Phe134, Leu142, Trp153, Phe157, Leu160, Phe194), along with several bridging water molecules, and meanwhile, the significant shifting occurs in the local conformation of the protein as the ligand's binding. A series of the residues (Gln141-Phe157) on the so-called "cap domain" are proposed to be responsible for capturing the ligand at the initial stage of the binding. Besides, the changes of the ligand's poses are also quantitatively characterized by the proper choice of the coordinate system. Our work will contribute to the more penetrating understanding of the ligand binding process and the receptor affinity difference between several members in the KAR family and help design new, more effective germination stimulants.
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Affiliation(s)
- Fei Hu
- International Joint Research Laboratory of Nano-Micro Architecture Chemistry, Institute of Theoretical Chemistry , Jilin University , Changchun 130023 , Jilin , People's Republic of China
| | - Xiao-Ting Liu
- International Joint Research Laboratory of Nano-Micro Architecture Chemistry, Institute of Theoretical Chemistry , Jilin University , Changchun 130023 , Jilin , People's Republic of China
| | - Ji-Long Zhang
- International Joint Research Laboratory of Nano-Micro Architecture Chemistry, Institute of Theoretical Chemistry , Jilin University , Changchun 130023 , Jilin , People's Republic of China
| | - Qing-Chuan Zheng
- International Joint Research Laboratory of Nano-Micro Architecture Chemistry, Institute of Theoretical Chemistry , Jilin University , Changchun 130023 , Jilin , People's Republic of China
| | - Roberts I Eglitis
- Institute of Solid State Physics , University of Latvia , 8 Kengaraga Str. , Riga LV1067 , Latvia
| | - Hong-Xing Zhang
- International Joint Research Laboratory of Nano-Micro Architecture Chemistry, Institute of Theoretical Chemistry , Jilin University , Changchun 130023 , Jilin , People's Republic of China
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21
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Lee I, Choi S, Lee S, Soh MS. KAI2-KL signaling intersects with light-signaling for photomorphogenesis. PLANT SIGNALING & BEHAVIOR 2019; 14:e1588660. [PMID: 30829108 PMCID: PMC6512941 DOI: 10.1080/15592324.2019.1588660] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Light is an important environmental cue, causing a high degree of developmental plasticity in higher plants. The outcome of light-regulated developmental response is determined by not only photo-sensory systems but also endogenous physiological contexts in plants. KARRIKIN-INSENSITIVE2 (KAI2) functions as a receptor of karrikin and endogenous, as yet to be identified, KAI2 ligand (KL). The loss-of-function of KAI2 caused light-hyposensitive photomorphogenesis, affecting the expression light-responsive genes under the light conditions. However, it remains still unclear how KAI2-KL signaling interacts with light-signaling. Here, we show that the ply2 mutation, a severe loss-of-function allele of KAI2 affected the expression of a subset of light-responsive genes, irrespectively of light condition. The results implied that the overlapping set of light- and KAI2-responsive genes may serve as an integrating node between light- and KAI2-KL signaling. Further, the results of double mutant analyses between the ply2 mutant and mutants of CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) or LONG HYPOCOTYL IN FAR-RED (HFR1) implicated that KAI2-KL signaling acts at downstream of COP1, largely independently of HFR1. Together, these results suggest that KAI2-KL signaling intersects with a subset of the light-regulatory network, by which plants adjust their photomorphogenic development.
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Affiliation(s)
- Inhye Lee
- Division of Integrative Bioscience and Biotechnology, College of Life Science, Sejong University, Seoul, Republic of Korea
| | - Soobin Choi
- Division of Integrative Bioscience and Biotechnology, College of Life Science, Sejong University, Seoul, Republic of Korea
| | - Sumin Lee
- Division of Integrative Bioscience and Biotechnology, College of Life Science, Sejong University, Seoul, Republic of Korea
- Sumin Lee Division of Integrative Bioscience and Biotechnology, College of Life Science, Sejong University, Seoul 143-747, Republic of Korea
| | - Moon-Soo Soh
- Division of Integrative Bioscience and Biotechnology, College of Life Science, Sejong University, Seoul, Republic of Korea
- CONTACT Moon-Soo Soh
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22
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Yao J, Mashiguchi K, Scaffidi A, Akatsu T, Melville KT, Morita R, Morimoto Y, Smith SM, Seto Y, Flematti GR, Yamaguchi S, Waters MT. An allelic series at the KARRIKIN INSENSITIVE 2 locus of Arabidopsis thaliana decouples ligand hydrolysis and receptor degradation from downstream signalling. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 96:75-89. [PMID: 29982999 DOI: 10.1111/tpj.14017] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 06/14/2018] [Accepted: 06/20/2018] [Indexed: 05/25/2023]
Abstract
Karrikins are butenolide compounds present in post-fire environments that can stimulate seed germination in many species, including Arabidopsis thaliana. Plants also produce endogenous butenolide compounds that serve as hormones, namely strigolactones (SLs). The receptor for karrikins (KARRIKIN INSENSITIVE 2; KAI2) and the receptor for SLs (DWARF14; D14) are homologous proteins that share many similarities. The mode of action of D14 as a dual enzyme receptor protein is well established, but the nature of KAI2-dependent signalling and its function as a receptor are not fully understood. To expand our knowledge of how KAI2 operates, we screened ethyl methanesulphonate (EMS)-mutagenized populations of A. thaliana for mutants with kai2-like phenotypes and isolated 13 new kai2 alleles. Among these alleles, kai2-10 encoded a D184N protein variant that was stable in planta. Differential scanning fluorimetry assays indicated that the KAI2 D184N protein could interact normally with bioactive ligands. We developed a KAI2-active version of the fluorescent strigolactone analogue Yoshimulactone Green to show that KAI2 D184N exhibits normal rates of ligand hydrolysis. KAI2 D184N degraded in response to treatment with exogenous ligands, suggesting that receptor degradation is a consequence of ligand binding and hydrolysis, but is insufficient for signalling activity. Remarkably, KAI2 D184N degradation was hypersensitive to karrikins, but showed a normal response to strigolactone analogues, implying that these butenolides may interact differently with KAI2. These results demonstrate that the enzymatic and signalling functions of KAI2 can be decoupled, and provide important insights into the mechanistic events that underpin butenolide signalling in plants.
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Affiliation(s)
- Jiaren Yao
- School of Molecular Sciences, The University of Western Australia Perth, 35 Stirling Hwy, Crawley, WA, 6009, Australia
- The ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia Perth, 35 Stirling Hwy, Crawley, WA, 6009, Australia
| | - Kiyoshi Mashiguchi
- Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan
| | - Adrian Scaffidi
- School of Molecular Sciences, The University of Western Australia Perth, 35 Stirling Hwy, Crawley, WA, 6009, Australia
| | - Tomoki Akatsu
- The ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia Perth, 35 Stirling Hwy, Crawley, WA, 6009, Australia
| | - Kim T Melville
- School of Molecular Sciences, The University of Western Australia Perth, 35 Stirling Hwy, Crawley, WA, 6009, Australia
- The ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia Perth, 35 Stirling Hwy, Crawley, WA, 6009, Australia
| | - Ryo Morita
- Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan
| | - Yu Morimoto
- Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan
| | - Steven M Smith
- School of Natural Sciences, The University of Tasmania, Hobart, TAS, 7000, Australia
| | - Yoshiya Seto
- Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan
| | - Gavin R Flematti
- School of Molecular Sciences, The University of Western Australia Perth, 35 Stirling Hwy, Crawley, WA, 6009, Australia
| | - Shinjiro Yamaguchi
- Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan
| | - Mark T Waters
- School of Molecular Sciences, The University of Western Australia Perth, 35 Stirling Hwy, Crawley, WA, 6009, Australia
- The ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia Perth, 35 Stirling Hwy, Crawley, WA, 6009, Australia
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