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Dun EA, Brewer PB, Gillam EMJ, Beveridge CA. Strigolactones and Shoot Branching: What Is the Real Hormone and How Does It Work? Plant Cell Physiol 2023; 64:967-983. [PMID: 37526426 PMCID: PMC10504579 DOI: 10.1093/pcp/pcad088] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 07/26/2023] [Accepted: 08/01/2023] [Indexed: 08/02/2023]
Abstract
There have been substantial advances in our understanding of many aspects of strigolactone regulation of branching since the discovery of strigolactones as phytohormones. These include further insights into the network of phytohormones and other signals that regulate branching, as well as deep insights into strigolactone biosynthesis, metabolism, transport, perception and downstream signaling. In this review, we provide an update on recent advances in our understanding of how the strigolactone pathway co-ordinately and dynamically regulates bud outgrowth and pose some important outstanding questions that are yet to be resolved.
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Affiliation(s)
- Elizabeth A Dun
- ARC Centre of Excellence for Plant Success in Nature and Agriculture, The University of Queensland, St Lucia, QLD 4072, Australia
- School of Agriculture and Food Sustainability, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Philip B Brewer
- ARC Centre of Excellence for Plant Success in Nature and Agriculture, The University of Queensland, St Lucia, QLD 4072, Australia
- Waite Research Institute, School of Agriculture Food & Wine, The University of Adelaide, Adelaide, SA 5064, Australia
| | - Elizabeth M J Gillam
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Christine A Beveridge
- ARC Centre of Excellence for Plant Success in Nature and Agriculture, The University of Queensland, St Lucia, QLD 4072, Australia
- School of Agriculture and Food Sustainability, The University of Queensland, St Lucia, QLD 4072, Australia
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Cao D, Chabikwa T, Barbier F, Dun EA, Fichtner F, Dong L, Kerr SC, Beveridge CA. Auxin-independent effects of apical dominance induce changes in phytohormones correlated with bud outgrowth. Plant Physiol 2023; 192:1420-1434. [PMID: 36690819 PMCID: PMC10231355 DOI: 10.1093/plphys/kiad034] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 12/20/2022] [Accepted: 12/20/2022] [Indexed: 06/01/2023]
Abstract
The inhibition of shoot branching by the growing shoot tip of plants, termed apical dominance, was originally thought to be mediated by auxin. Recently, the importance of the shoot tip sink strength during apical dominance has re-emerged with recent studies highlighting roles for sugars in promoting branching. This raises many unanswered questions on the relative roles of auxin and sugars in apical dominance. Here we show that auxin depletion after decapitation is not always the initial trigger of rapid cytokinin (CK) increases in buds that are instead correlated with enhanced sugars. Auxin may also act through strigolactones (SLs) which have been shown to suppress branching after decapitation, but here we show that SLs do not have a significant effect on initial bud outgrowth after decapitation. We report here that when sucrose or CK is abundant, SLs are less inhibitory during the bud release stage compared to during later stages and that SL treatment rapidly inhibits CK accumulation in pea (Pisum sativum) axillary buds of intact plants. After initial bud release, we find an important role of gibberellin (GA) in promoting sustained bud growth downstream of auxin. We are, therefore, able to suggest a model of apical dominance that integrates auxin, sucrose, SLs, CKs, and GAs and describes differences in signalling across stages of bud release to sustained growth.
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Affiliation(s)
- Da Cao
- ARC Centre of Excellence for Plant Success in Nature and Agriculture, School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
- School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Tinashe Chabikwa
- School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Francois Barbier
- ARC Centre of Excellence for Plant Success in Nature and Agriculture, School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
- School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Elizabeth A Dun
- ARC Centre of Excellence for Plant Success in Nature and Agriculture, School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
- School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Franziska Fichtner
- ARC Centre of Excellence for Plant Success in Nature and Agriculture, School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
- School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Lili Dong
- School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Stephanie C Kerr
- School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Christine A Beveridge
- ARC Centre of Excellence for Plant Success in Nature and Agriculture, School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
- School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
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Kerr SC, Patil SB, de Saint Germain A, Pillot JP, Saffar J, Ligerot Y, Aubert G, Citerne S, Bellec Y, Dun EA, Beveridge CA, Rameau C. Integration of the SMXL/D53 strigolactone signalling repressors in the model of shoot branching regulation in Pisum sativum. Plant J 2021; 107:1756-1770. [PMID: 34245626 DOI: 10.1111/tpj.15415] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 06/24/2021] [Accepted: 07/04/2021] [Indexed: 05/08/2023]
Abstract
DWARF53 (D53) in rice (Oryza sativa) and its homologs in Arabidopsis (Arabidopsis thaliana), SUPPRESSOR OF MAX2-LIKE 6 (SMXL6), SMXL7 and SMXL8, are well established negative regulators of strigolactone (SL) signalling in shoot branching regulation. Little is known of pea (Pisum sativum) homologs and whether D53 and related SMXLs are specific to SL signalling pathways. Here, we identify two allelic pea mutants, dormant3 (dor3), and demonstrate through gene mapping and sequencing that DOR3 corresponds to a homolog of D53 and SMXL6/SMXL7, designated PsSMXL7. Phenotype analysis, gene expression, protein and hormone quantification assays were performed to determine the role of PsSMXL7 in regulation of bud outgrowth and the role of PsSMXL7 and D53 in integrating SL and cytokinin (CK) responses. Like D53 and related SMXLs, we show that PsSMXL7 can be degraded by SL and induces feedback upregulation of PsSMXL7 transcript. Here we reveal a system conserved in pea and rice, whereby CK also upregulates PsSMXL7/D53 transcripts, providing a clear mechanism for SL and CK cross-talk in the regulation of branching. To further deepen our understanding of the branching network in pea, we provide evidence that SL acts via PsSMXL7 to modulate auxin content via PsAFB5, which itself regulates expression of SL biosynthesis genes. We therefore show that PsSMXL7 is key to a triple hormone network involving an auxin-SL feedback mechanism and SL-CK cross-talk.
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Affiliation(s)
- Stephanie C Kerr
- ARC Centre for Plant Success in Nature and Agriculture, School of Biological Sciences, The University of Queensland, St Lucia, Qld, 4072, Australia
| | - Suyash B Patil
- National Key Facility for Crop Gene Resources and Genetic Improvement, ICS, CAAS, Beijing, 100081, China
| | | | - Jean-Paul Pillot
- Institut Jean-Pierre Bourgin, INRAE, AgroParisTech, Université Paris-Saclay, 78000, Versailles, France
| | - Julie Saffar
- Institut Jean-Pierre Bourgin, INRAE, AgroParisTech, Université Paris-Saclay, 78000, Versailles, France
| | - Yasmine Ligerot
- Institut Jean-Pierre Bourgin, INRAE, AgroParisTech, Université Paris-Saclay, 78000, Versailles, France
- Université Paris-Sud, Université Paris-Saclay, 91405, Orsay, France
| | - Grégoire Aubert
- Agroécologie, AgroSup Dijon, INRAE, Univ. Bourgogne, Univ. Bourgogne Franche-Comté, F-21000, Dijon, France
| | - Sylvie Citerne
- Institut Jean-Pierre Bourgin, INRAE, AgroParisTech, Université Paris-Saclay, 78000, Versailles, France
| | - Yannick Bellec
- Institut Jean-Pierre Bourgin, INRAE, AgroParisTech, Université Paris-Saclay, 78000, Versailles, France
| | - Elizabeth A Dun
- ARC Centre for Plant Success in Nature and Agriculture, School of Biological Sciences, The University of Queensland, St Lucia, Qld, 4072, Australia
| | - Christine A Beveridge
- ARC Centre for Plant Success in Nature and Agriculture, School of Biological Sciences, The University of Queensland, St Lucia, Qld, 4072, Australia
| | - Catherine Rameau
- Institut Jean-Pierre Bourgin, INRAE, AgroParisTech, Université Paris-Saclay, 78000, Versailles, France
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Barbier FF, Dun EA, Kerr SC, Chabikwa TG, Beveridge CA. An Update on the Signals Controlling Shoot Branching. Trends Plant Sci 2019; 24:220-236. [PMID: 30797425 DOI: 10.1016/j.tplants.2018.12.001] [Citation(s) in RCA: 140] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 12/11/2018] [Accepted: 12/20/2018] [Indexed: 05/21/2023]
Abstract
Many new questions on the regulation of shoot branching have been raised in recent years, prompting a review and reassessment of the role of each signal involved. Sugars and their signaling networks have been attributed a major role in the early events of axillary bud outgrowth, whereas cytokinin appears to play a critical role in the modulation of this process in response to the environment. Perception of the recently discovered hormone strigolactone is now quite well understood, while the downstream targets remain largely unknown. Recent literature has highlighted that auxin export from a bud is important for its subsequent growth.
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Affiliation(s)
- Francois F Barbier
- The University of Queensland, School of Biological Sciences, St. Lucia, QLD 4072, Australia
| | - Elizabeth A Dun
- The University of Queensland, School of Biological Sciences, St. Lucia, QLD 4072, Australia; These authors contributed equally to this publication
| | - Stephanie C Kerr
- The University of Queensland, School of Biological Sciences, St. Lucia, QLD 4072, Australia; These authors contributed equally to this publication
| | - Tinashe G Chabikwa
- The University of Queensland, School of Biological Sciences, St. Lucia, QLD 4072, Australia
| | - Christine A Beveridge
- The University of Queensland, School of Biological Sciences, St. Lucia, QLD 4072, Australia.
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Abstract
Barbier et al. give a quick guide to apical dominance, whereby a plant's main shoot dominates and inhibits the outgrowth of other shoots.
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Affiliation(s)
- Francois F Barbier
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia
| | - Elizabeth A Dun
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia
| | - Christine A Beveridge
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia.
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Kameoka H, Dun EA, Lopez-Obando M, Brewer PB, de Saint Germain A, Rameau C, Beveridge CA, Kyozuka J. Phloem Transport of the Receptor DWARF14 Protein Is Required for Full Function of Strigolactones. Plant Physiol 2016; 172:1844-1852. [PMID: 27670819 PMCID: PMC5100793 DOI: 10.1104/pp.16.01212] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 09/24/2016] [Indexed: 05/06/2023]
Abstract
The cell-to-cell transport of signaling molecules is essential for multicellular organisms to coordinate the action of their cells. Recent studies identified DWARF14 (D14) as a receptor of strigolactones (SLs), molecules that act as plant hormones and inhibit shoot branching. Here, we demonstrate that RAMOSUS3, a pea ortholog of D14, works as a graft-transmissible signal to suppress shoot branching. In addition, we show that D14 protein is contained in phloem sap and transported through the phloem to axillary buds in rice. SLs are not required for the transport of D14 protein. Disruption of D14 transport weakens the suppression of axillary bud outgrowth of rice. Taken together, we conclude that the D14 protein works as an intercellular signaling molecule to fine-tune SL function. Our findings provide evidence that the intercellular transport of a receptor can regulate the action of plant hormones.
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Affiliation(s)
- Hiromu Kameoka
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan (H.K., J.K.)
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia (E.A.D., P.B.B., C.A.B.)
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles Cedex, France (M.L.-O., A.d.S.G., C.R.)
| | - Elizabeth A Dun
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan (H.K., J.K.)
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia (E.A.D., P.B.B., C.A.B.)
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles Cedex, France (M.L.-O., A.d.S.G., C.R.)
| | - Mauricio Lopez-Obando
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan (H.K., J.K.)
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia (E.A.D., P.B.B., C.A.B.)
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles Cedex, France (M.L.-O., A.d.S.G., C.R.)
| | - Philip B Brewer
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan (H.K., J.K.)
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia (E.A.D., P.B.B., C.A.B.)
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles Cedex, France (M.L.-O., A.d.S.G., C.R.)
| | - Alexandre de Saint Germain
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan (H.K., J.K.)
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia (E.A.D., P.B.B., C.A.B.)
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles Cedex, France (M.L.-O., A.d.S.G., C.R.)
| | - Catherine Rameau
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan (H.K., J.K.)
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia (E.A.D., P.B.B., C.A.B.)
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles Cedex, France (M.L.-O., A.d.S.G., C.R.)
| | - Christine A Beveridge
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan (H.K., J.K.)
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia (E.A.D., P.B.B., C.A.B.)
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles Cedex, France (M.L.-O., A.d.S.G., C.R.)
| | - Junko Kyozuka
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan (H.K., J.K.)
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia (E.A.D., P.B.B., C.A.B.)
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles Cedex, France (M.L.-O., A.d.S.G., C.R.)
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Brewer PB, Dun EA, Gui R, Mason MG, Beveridge CA. Strigolactone Inhibition of Branching Independent of Polar Auxin Transport. Plant Physiol 2015; 168:1820-9. [PMID: 26111543 PMCID: PMC4528729 DOI: 10.1104/pp.15.00014] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 06/24/2015] [Indexed: 05/20/2023]
Abstract
The outgrowth of axillary buds into branches is regulated systemically via plant hormones and the demand of growing shoot tips for sugars. The plant hormone auxin is thought to act via two mechanisms. One mechanism involves auxin regulation of systemic signals, cytokinins and strigolactones, which can move into axillary buds. The other involves suppression of auxin transport/canalization from axillary buds into the main stem and is enhanced by a low sink for auxin in the stem. In this theory, the relative ability of the buds and stem to transport auxin controls bud outgrowth. Here, we evaluate whether auxin transport is required or regulated during bud outgrowth in pea (Pisum sativum). The profound, systemic, and long-term effects of the auxin transport inhibitor N-1-naphthylphthalamic acid had very little inhibitory effect on bud outgrowth in strigolactone-deficient mutants. Strigolactones can also inhibit bud outgrowth in N-1-naphthylphthalamic acid-treated shoots that have greatly diminished auxin transport. Moreover, strigolactones can inhibit bud outgrowth despite a much diminished auxin supply in in vitro or decapitated plants. These findings demonstrate that auxin sink strength in the stem is not important for bud outgrowth in pea. Consistent with alternative mechanisms of auxin regulation of systemic signals, enhanced auxin biosynthesis in Arabidopsis (Arabidopsis thaliana) can suppress branching in yucca1D plants compared with wild-type plants, but has no effect on bud outgrowth in a strigolactone-deficient mutant background.
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Affiliation(s)
- Philip B Brewer
- The University of Queensland, School of Biological Sciences, St. Lucia, Queensland 4072, Australia
| | - Elizabeth A Dun
- The University of Queensland, School of Biological Sciences, St. Lucia, Queensland 4072, Australia
| | - Renyi Gui
- The University of Queensland, School of Biological Sciences, St. Lucia, Queensland 4072, Australia
| | - Michael G Mason
- The University of Queensland, School of Biological Sciences, St. Lucia, Queensland 4072, Australia
| | - Christine A Beveridge
- The University of Queensland, School of Biological Sciences, St. Lucia, Queensland 4072, Australia
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de Saint Germain A, Ligerot Y, Dun EA, Pillot JP, Ross JJ, Beveridge CA, Rameau C. Strigolactones stimulate internode elongation independently of gibberellins. Plant Physiol 2013; 163:1012-25. [PMID: 23943865 PMCID: PMC3793021 DOI: 10.1104/pp.113.220541] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Accepted: 08/08/2013] [Indexed: 05/18/2023]
Abstract
Strigolactone (SL) mutants in diverse species show reduced stature in addition to their extensive branching. Here, we show that this dwarfism in pea (Pisum sativum) is not attributable to the strong branching of the mutants. The continuous supply of the synthetic SL GR24 via the root system using hydroponics can restore internode length of the SL-deficient rms1 mutant but not of the SL-response rms4 mutant, indicating that SLs stimulate internode elongation via RMS4. Cytological analysis of internode epidermal cells indicates that SLs control cell number but not cell length, suggesting that SL may affect stem elongation by stimulating cell division. Consequently, SLs can repress (in axillary buds) or promote (in the stem) cell division in a tissue-dependent manner. Because gibberellins (GAs) increase internode length by affecting both cell division and cell length, we tested if SLs stimulate internode elongation by affecting GA metabolism or signaling. Genetic analyses using SL-deficient and GA-deficient or DELLA-deficient double mutants, together with molecular and physiological approaches, suggest that SLs act independently from GAs to stimulate internode elongation.
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Affiliation(s)
| | | | - Elizabeth A. Dun
- Institut Jean-Pierre Bourgin, INRA UMR1318, INRA-AgroParisTech, F–78000 Versailles, France (A.d.S.G., Y.L., J-P.P., C.R.)
- University of Queensland, School of Biological Sciences, St. Lucia, Queensland 4072 Australia (E.A.D., C.A.B.); and
- School of Plant Science, University of Tasmania, Sandy Bay, Tasmania 7005 Australia (J.J.R.)
| | - Jean-Paul Pillot
- Institut Jean-Pierre Bourgin, INRA UMR1318, INRA-AgroParisTech, F–78000 Versailles, France (A.d.S.G., Y.L., J-P.P., C.R.)
- University of Queensland, School of Biological Sciences, St. Lucia, Queensland 4072 Australia (E.A.D., C.A.B.); and
- School of Plant Science, University of Tasmania, Sandy Bay, Tasmania 7005 Australia (J.J.R.)
| | - John J. Ross
- Institut Jean-Pierre Bourgin, INRA UMR1318, INRA-AgroParisTech, F–78000 Versailles, France (A.d.S.G., Y.L., J-P.P., C.R.)
- University of Queensland, School of Biological Sciences, St. Lucia, Queensland 4072 Australia (E.A.D., C.A.B.); and
- School of Plant Science, University of Tasmania, Sandy Bay, Tasmania 7005 Australia (J.J.R.)
| | - Christine A. Beveridge
- Institut Jean-Pierre Bourgin, INRA UMR1318, INRA-AgroParisTech, F–78000 Versailles, France (A.d.S.G., Y.L., J-P.P., C.R.)
- University of Queensland, School of Biological Sciences, St. Lucia, Queensland 4072 Australia (E.A.D., C.A.B.); and
- School of Plant Science, University of Tasmania, Sandy Bay, Tasmania 7005 Australia (J.J.R.)
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Dun EA, de Saint Germain A, Rameau C, Beveridge CA. Dynamics of strigolactone function and shoot branching responses in Pisum sativum. Mol Plant 2013; 6:128-40. [PMID: 23220942 DOI: 10.1093/mp/sss131] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Strigolactones (SLs), or their metabolites, were recently identified as endogenous inhibitors of shoot branching. However, certain key features and dynamics of SL action remained to be physiologically characterized. Here we show that successive direct application of SL to axillary buds at every node along the stem can fully inhibit branching. The SL inhibition of early outgrowth did not require inhibitory signals from other growing buds or the shoot tip. In addition to this very early or initial suppression of outgrowth, we also found SL to be effective, up to a point, at moderating the continuing growth of axillary branches. The effectiveness of SL at affecting bud and branch growth correlated with the ability of SL to regulate expression of PsBRC1. PsBRC1 is a transcription factor that is expressed strongly in axillary buds and is required for SL inhibition of shoot branching. Consistent with a dynamic role of the hormone, SL inhibition of bud growth did not prevent buds from later responding to a decapitation treatment, even though SL treatment immediately after decapitation inhibits the outgrowth response. Also, as expected from the hypothesized branching control network in plants, treatment of exogenous SL caused feedback down-regulation of SL biosynthesis genes within 2 h. Altogether, these results reveal new insights into the dynamics of SL function and support the premise that SLs or SL-derived metabolites function dynamically as a shoot branching hormone and that they act directly in axillary buds.
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Affiliation(s)
- Elizabeth A Dun
- The University of Queensland, School of Biological Sciences, St Lucia, QLD, 4072 Australia
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10
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Dun EA, de Saint Germain A, Rameau C, Beveridge CA. Antagonistic action of strigolactone and cytokinin in bud outgrowth control. Plant Physiol 2012; 158:487-98. [PMID: 22042819 PMCID: PMC3252097 DOI: 10.1104/pp.111.186783] [Citation(s) in RCA: 265] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Accepted: 10/28/2011] [Indexed: 05/18/2023]
Abstract
Cytokinin (CK) has long been implicated as a promoter of bud outgrowth in plants, but exactly how this is achieved in coordination with other plant hormones is unclear. The recent discovery of strigolactones (SLs) as the long-sought branch-inhibiting hormone allowed us to test how CK and SL coordinately regulate bud outgrowth in pea (Pisum sativum). We found that SL-deficient plants are more sensitive to stimulation of bud growth by low concentrations of locally applied CK than wild-type plants. Furthermore, in contrast with SL mutant plants, buds of wild-type plants are almost completely resistant to stimulation by CK supplied to the vasculature. Regardless of whether the exogenous hormones were supplied locally or to the xylem stream, SL and CK acted antagonistically on bud outgrowth. These data suggest that SLs do not affect the delivery of CK to axillary buds and vice versa. Rather, these data combined with dose-response experiments suggest that SLs and CK can act directly in buds to control their outgrowth. These hormones may converge at a common point in the bud outgrowth regulatory pathway. The expression of pea BRANCHED1, a TCP transcription factor expressed strongly in buds and thought to act downstream of SLs in shoot branching, is regulated by CK and SL without a requirement for protein synthesis and in a manner that correlates with observed bud growth responses.
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Affiliation(s)
| | | | | | - Christine A. Beveridge
- University of Queensland, School of Biological Sciences, St Lucia, Queensland, 4072 Australia (E.A.D., C.A.B.); Institut Jean-Pierre Bourgin, INRA UMR1318 INRA-AgroParisTech, F–78000 Versailles, France (A.d.S.G., C.R.)
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Dun EA, Hanan J, Beveridge CA. Computational modeling and molecular physiology experiments reveal new insights into shoot branching in pea. Plant Cell 2009; 21:3459-72. [PMID: 19948786 PMCID: PMC2798318 DOI: 10.1105/tpc.109.069013] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2009] [Revised: 09/17/2009] [Accepted: 11/02/2009] [Indexed: 05/20/2023]
Abstract
Bud outgrowth is regulated by the interplay of multiple hormones, including auxin, cytokinin, strigolactones, and an unidentified long-distance feedback signal that moves from shoot to root. The model of bud outgrowth regulation in pea (Pisum sativum) includes these signals and a network of five RAMOSUS (RMS) genes that operate in a shoot-root-shoot loop to regulate the synthesis of, and response to, strigolactones. The number of components in this network renders the integration of new and existing hypotheses both complex and cumbersome. A hypothesis-driven computational model was therefore developed to help understand regulation of shoot branching. The model evolved in parallel with stepwise laboratory research, helping to define and test key hypotheses. The computational model was used to verify new mechanisms involved in the regulation of shoot branching by confirming that the new hypotheses captured all relevant biological data sets. Based on cytokinin and RMS1 expression analyses, this model is extended to include subtle but important differences in the function of RMS3 and RMS4 genes in the shoot and rootstock. Additionally, this research indicates that a branch-derived signal upregulates RMS1 expression independent of the other feedback signal. Furthermore, we propose xylem-sap cytokinin promotes sustained bud outgrowth, rather than acting at the earlier stage of bud release.
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Affiliation(s)
- Elizabeth A. Dun
- The University of Queensland, Australian Research Council Centre of Excellence for Integrative Legume Research and School of Biological Sciences, St. Lucia, 4072 Australia
| | - Jim Hanan
- The University of Queensland, Centre for Biological Information Technology, St. Lucia, 4072 Australia
| | - Christine A. Beveridge
- The University of Queensland, Australian Research Council Centre of Excellence for Integrative Legume Research and School of Biological Sciences, St. Lucia, 4072 Australia
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Beveridge CA, Dun EA, Rameau C. Pea has its tendrils in branching discoveries spanning a century from auxin to strigolactones. Plant Physiol 2009; 151:985-90. [PMID: 19767387 PMCID: PMC2773098 DOI: 10.1104/pp.109.143909] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Accepted: 09/15/2009] [Indexed: 05/09/2023]
Affiliation(s)
- Christine A Beveridge
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia.
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Abstract
During plant development, the transition from a vegetative to reproductive state is a critical event. For decades, pea (Pisum sativum) has been used as a model species to study this transition. These studies have led to a conceptual, qualitative model for the control of flower initiation, referred to as the 'classical' model. This model involves many inputs, namely photoperiod, genetic states and two mobile signals which interact to determine the first node of flowering. Here, we developed a computational model based on the hypotheses of the classical model. Accordingly, we converted qualitative hypotheses into quantitative rules. We found that new hypotheses, in addition to those already described for the classical model, were required that explicitly described the signals. In particular, we hypothesized that the key flowering gene HR interacts with the photoperiod pathway to control flowering. The computational model was tested against a wide range of biological data, including pre-existing and new experimental results presented here, and was found to be accurate. This computational model, together with ongoing experimental advances, will assist future modelling efforts to increase our understanding of flowering in pea.
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Affiliation(s)
- Bénédicte Wenden
- INRA, Institut JP Bourgin, UR 254 Station de Génétique et d'Amélioration des Plantes, 78026 Versailles, France
| | - Elizabeth A Dun
- The University of Queensland, Australian Research Council Centre of Excellence for Integrative Legume Research, St. Lucia, Qld 4072, Australia
- The University of Queensland, School of Biological Sciences, St. Lucia, Qld 4072, Australia
| | - Jim Hanan
- The University of Queensland, Australian Research Council Centre of Excellence for Integrative Legume Research, St. Lucia, Qld 4072, Australia
- The University of Queensland, Centre for Biological Information Technology, St. Lucia, Qld 4072, Australia
| | - Bruno Andrieu
- INRA, UMR 1091 Environnement et Grandes Cultures, 78850 Thiverval-Grignon, France
| | - James L Weller
- School of Plant Science, University of Tasmania, Hobart, Tas. 7001, Australia
| | - Christine A Beveridge
- The University of Queensland, Australian Research Council Centre of Excellence for Integrative Legume Research, St. Lucia, Qld 4072, Australia
- The University of Queensland, School of Biological Sciences, St. Lucia, Qld 4072, Australia
| | - Catherine Rameau
- INRA, Institut JP Bourgin, UR 254 Station de Génétique et d'Amélioration des Plantes, 78026 Versailles, France
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Dun EA, Brewer PB, Beveridge CA. Strigolactones: discovery of the elusive shoot branching hormone. Trends Plant Sci 2009; 14:364-72. [PMID: 19540149 DOI: 10.1016/j.tplants.2009.04.003] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Revised: 04/09/2009] [Accepted: 04/09/2009] [Indexed: 05/21/2023]
Abstract
The control of axillary bud outgrowth involves a network of hormonal signals and feedback regulation. A repressor of bud outgrowth that is central to the story has been missing since it was first postulated more than 70 years ago. This hormone moves upward in plant stems and can act as a long-distance messenger for auxin. Strigolactones, previously known as carotenoid-derived signals exuded from roots, fit the role of this elusive hormone. The discovery of branching inhibition by strigolactones will help solve many confusing aspects of branch control, including interactions with other signals, and is a great step forward toward uncovering the links between environment, genetics and plant form.
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Affiliation(s)
- Elizabeth A Dun
- The University of Queensland, Australian Research Council Centre of Excellence for Integrative Legume Research, St Lucia, QLD 4072, Australia
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Brewer PB, Dun EA, Ferguson BJ, Rameau C, Beveridge CA. Strigolactone acts downstream of auxin to regulate bud outgrowth in pea and Arabidopsis. Plant Physiol 2009; 150:482-93. [PMID: 19321710 PMCID: PMC2675716 DOI: 10.1104/pp.108.134783] [Citation(s) in RCA: 245] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Accepted: 03/23/2009] [Indexed: 05/18/2023]
Abstract
During the last century, two key hypotheses have been proposed to explain apical dominance in plants: auxin promotes the production of a second messenger that moves up into buds to repress their outgrowth, and auxin saturation in the stem inhibits auxin transport from buds, thereby inhibiting bud outgrowth. The recent discovery of strigolactone as the novel shoot-branching inhibitor allowed us to test its mode of action in relation to these hypotheses. We found that exogenously applied strigolactone inhibited bud outgrowth in pea (Pisum sativum) even when auxin was depleted after decapitation. We also found that strigolactone application reduced branching in Arabidopsis (Arabidopsis thaliana) auxin response mutants, suggesting that auxin may act through strigolactones to facilitate apical dominance. Moreover, strigolactone application to tiny buds of mutant or decapitated pea plants rapidly stopped outgrowth, in contrast to applying N-1-naphthylphthalamic acid (NPA), an auxin transport inhibitor, which significantly slowed growth only after several days. Whereas strigolactone or NPA applied to growing buds reduced bud length, only NPA blocked auxin transport in the bud. Wild-type and strigolactone biosynthesis mutant pea and Arabidopsis shoots were capable of instantly transporting additional amounts of auxin in excess of endogenous levels, contrary to predictions of auxin transport models. These data suggest that strigolactone does not act primarily by affecting auxin transport from buds. Rather, the primary repressor of bud outgrowth appears to be the auxin-dependent production of strigolactones.
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Affiliation(s)
- Philip B Brewer
- University of Queensland, Australian Research Council Centre of Excellence for Integrative Legume Research and School of Biological Sciences, St. Lucia, Queensland 4072, Australia
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Gomez-Roldan V, Fermas S, Brewer PB, Puech-Pagès V, Dun EA, Pillot JP, Letisse F, Matusova R, Danoun S, Portais JC, Bouwmeester H, Bécard G, Beveridge CA, Rameau C, Rochange SF. Strigolactone inhibition of shoot branching. Nature 2008; 455:189-94. [PMID: 18690209 DOI: 10.1038/nature07271] [Citation(s) in RCA: 1263] [Impact Index Per Article: 78.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2008] [Accepted: 07/18/2008] [Indexed: 11/09/2022]
Abstract
A carotenoid-derived hormonal signal that inhibits shoot branching in plants has long escaped identification. Strigolactones are compounds thought to be derived from carotenoids and are known to trigger the germination of parasitic plant seeds and stimulate symbiotic fungi. Here we present evidence that carotenoid cleavage dioxygenase 8 shoot branching mutants of pea are strigolactone deficient and that strigolactone application restores the wild-type branching phenotype to ccd8 mutants. Moreover, we show that other branching mutants previously characterized as lacking a response to the branching inhibition signal also lack strigolactone response, and are not deficient in strigolactones. These responses are conserved in Arabidopsis. In agreement with the expected properties of the hormonal signal, exogenous strigolactone can be transported in shoots and act at low concentrations. We suggest that endogenous strigolactones or related compounds inhibit shoot branching in plants. Furthermore, ccd8 mutants demonstrate the diverse effects of strigolactones in shoot branching, mycorrhizal symbiosis and parasitic weed interaction.
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Affiliation(s)
- Victoria Gomez-Roldan
- Université de Toulouse, UPS, CNRS, Surface Cellulaire et Signalisation chez les Végétaux, 24 chemin de Borde Rouge, F-31326 Castanet-Tolosan, France
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Johnson X, Brcich T, Dun EA, Goussot M, Haurogné K, Beveridge CA, Rameau C. Branching genes are conserved across species. Genes controlling a novel signal in pea are coregulated by other long-distance signals. Plant Physiol 2006; 142:1014-26. [PMID: 16980559 PMCID: PMC1630745 DOI: 10.1104/pp.106.087676] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Accepted: 09/04/2006] [Indexed: 05/11/2023]
Abstract
Physiological and genetic studies with the ramosus (rms) mutants in garden pea (Pisum sativum) and more axillary shoots (max) mutants in Arabidopsis (Arabidopsis thaliana) have shown that shoot branching is regulated by a network of long-distance signals. Orthologous genes RMS1 and MAX4 control the synthesis of a novel graft-transmissible branching signal that may be a carotenoid derivative and acts as a branching inhibitor. In this study, we demonstrate further conservation of the branching control system by showing that MAX2 and MAX3 are orthologous to RMS4 and RMS5, respectively. This is consistent with the long-standing hypothesis that branching in pea is regulated by a novel long-distance signal produced by RMS1 and RMS5 and that RMS4 is implicated in the response to this signal. We examine RMS5 expression and show that it is more highly expressed relative to RMS1, but under similar transcriptional regulation as RMS1. Further expression studies support the hypothesis that RMS4 functions in shoot and rootstock and participates in the feedback regulation of RMS1 and RMS5 expression. This feedback involves a second novel long-distance signal that is lacking in rms2 mutants. RMS1 and RMS5 are also independently regulated by indole-3-acetic acid. RMS1, rather than RMS5, appears to be a key regulator of the branching inhibitor. This study presents new interactions between RMS genes and provides further evidence toward the ongoing elucidation of a model of axillary bud outgrowth in pea.
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Affiliation(s)
- Xenie Johnson
- Station de Génétique et d'Amélioration des Plantes, Institut J.P. Bourgin, Institut National de la Recherche Agronomique, 78026 Versailles, France
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Golovchenko AP, Dun EA, Filatova TG. [Lymphoid cell blast reaction and mitotic activity of the blood in leukemia]. Veterinariia 1980:29-30. [PMID: 7395072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Dun EA, Pozdniakov AA, Filatova TG. [Karyologic studies of cultures of lymphoid tissue]. Veterinariia 1978:41-3. [PMID: 569390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Burba LG, Dun EA, Simonian GA. [Changes in the bone marrow cell karyotype in the young of cows with leukemia]. Veterinariia 1978:43-6. [PMID: 644867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Burba LG, Golovchenko AP, Dun EA, Naletova LV. [Transformation of lymph node cells of cattle]. Veterinariia 1975:42-4. [PMID: 1216492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Dun EA, Golovchenko AP, Naletova LV. [Chromosome sets in the cells of hematopoietic organs in leukemia]. Veterinariia 1975:35-8. [PMID: 1114665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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