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Zhao Q, Wu Y, Gao L, Ma J, Li CY, Xiang CB. Sulfur nutrient availability regulates root elongation by affecting root indole-3-acetic acid levels and the stem cell niche. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2014; 56:1151-63. [PMID: 24831283 DOI: 10.1111/jipb.12217] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 05/14/2014] [Indexed: 05/20/2023]
Abstract
Sulfur is an essential macronutrient for plants with numerous biological functions. However, the influence of sulfur nutrient availability on the regulation of root development remains largely unknown. Here, we report the response of Arabidopsis thaliana L. root development and growth to different levels of sulfate, demonstrating that low sulfate levels promote the primary root elongation. By using various reporter lines, we examined in vivo IAA level and distribution, cell division, and root meristem in response to different sulfate levels. Meanwhile the dynamic changes of in vivo cysteine, glutathione, and IAA levels were measured. Root cysteine, glutathione, and IAA levels are positively correlated with external sulfate levels in the physiological range, which eventually affect root system architecture. Low sulfate levels also downregulate the genes involved in auxin biosynthesis and transport, and elevate the accumulation of PLT1 and PLT2. This study suggests that sulfate level affects the primary root elongation by regulating the endogenous auxin level and root stem cell niche maintenance.
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Affiliation(s)
- Qing Zhao
- School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China
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202
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Sanz L, Fernández-Marcos M, Modrego A, Lewis DR, Muday GK, Pollmann S, Dueñas M, Santos-Buelga C, Lorenzo O. Nitric oxide plays a role in stem cell niche homeostasis through its interaction with auxin. PLANT PHYSIOLOGY 2014; 166:1972-84. [PMID: 25315603 PMCID: PMC4256006 DOI: 10.1104/pp.114.247445] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2014] [Accepted: 10/09/2014] [Indexed: 05/18/2023]
Abstract
Nitric oxide (NO) is a unique reactive nitrogen molecule with an array of signaling functions that modulates plant developmental processes and stress responses. To explore the mechanisms by which NO modulates root development, we used a pharmacological approach and NO-deficient mutants to unravel the role of NO in establishing auxin distribution patterns necessary for stem cell niche homeostasis. Using the NO synthase inhibitor and Arabidopsis (Arabidopsis thaliana) NO biosynthesis mutants (nitric oxide-associated1 [noa1], nitrate reductase1 [nia1] and nia2, and nia1 nia2 noa1), we show that depletion of NO in noa1 reduces primary root elongation and increases flavonol accumulation consistent with elevated reactive oxygen species levels. The elevated flavonols are required for the growth effect, because the transparent testa4 mutation reverses the noa1 mutant root elongation phenotype. In addition, noa1 and nia1 nia2 noa1 NO-deficient mutant roots display small root meristems with abnormal divisions. Concomitantly, auxin biosynthesis, transport, and signaling are perturbed. We further show that NO accumulates in cortex/endodermis stem cells and their precursor cells. In endodermal and cortical cells, the noa1 mutant acts synergistically to the effect of the wuschel-related homeobox5 mutation on the proximal meristem, suggesting that NO could play an important role in regulating stem cell decisions, which has been reported in animals.
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Affiliation(s)
- Luis Sanz
- Departamento de Fisiología Vegetal, Instituto Hispano-Luso de Investigaciones Agrarias, Facultad de Biología, Universidad de Salamanca, 37185 Salamanca, Spain (L.S., M.F.-M., A.M., O.L.);Department of Biology and Center for Molecular Communication and Signaling, Wake Forest University, Winston-Salem, North Carolina 27106 (D.R.L., G.K.M.);Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, 28223 Pozuelo de Alarcón, Madrid, Spain (S.P.); andGrupo de Investigación en Polifenoles, Unidad de Nutrición y Bromatología, Universidad de Salamanca, 37007 Salamanca, Spain (M.D., C.S.-B.)
| | - María Fernández-Marcos
- Departamento de Fisiología Vegetal, Instituto Hispano-Luso de Investigaciones Agrarias, Facultad de Biología, Universidad de Salamanca, 37185 Salamanca, Spain (L.S., M.F.-M., A.M., O.L.);Department of Biology and Center for Molecular Communication and Signaling, Wake Forest University, Winston-Salem, North Carolina 27106 (D.R.L., G.K.M.);Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, 28223 Pozuelo de Alarcón, Madrid, Spain (S.P.); andGrupo de Investigación en Polifenoles, Unidad de Nutrición y Bromatología, Universidad de Salamanca, 37007 Salamanca, Spain (M.D., C.S.-B.)
| | - Abelardo Modrego
- Departamento de Fisiología Vegetal, Instituto Hispano-Luso de Investigaciones Agrarias, Facultad de Biología, Universidad de Salamanca, 37185 Salamanca, Spain (L.S., M.F.-M., A.M., O.L.);Department of Biology and Center for Molecular Communication and Signaling, Wake Forest University, Winston-Salem, North Carolina 27106 (D.R.L., G.K.M.);Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, 28223 Pozuelo de Alarcón, Madrid, Spain (S.P.); andGrupo de Investigación en Polifenoles, Unidad de Nutrición y Bromatología, Universidad de Salamanca, 37007 Salamanca, Spain (M.D., C.S.-B.)
| | - Daniel R Lewis
- Departamento de Fisiología Vegetal, Instituto Hispano-Luso de Investigaciones Agrarias, Facultad de Biología, Universidad de Salamanca, 37185 Salamanca, Spain (L.S., M.F.-M., A.M., O.L.);Department of Biology and Center for Molecular Communication and Signaling, Wake Forest University, Winston-Salem, North Carolina 27106 (D.R.L., G.K.M.);Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, 28223 Pozuelo de Alarcón, Madrid, Spain (S.P.); andGrupo de Investigación en Polifenoles, Unidad de Nutrición y Bromatología, Universidad de Salamanca, 37007 Salamanca, Spain (M.D., C.S.-B.)
| | - Gloria K Muday
- Departamento de Fisiología Vegetal, Instituto Hispano-Luso de Investigaciones Agrarias, Facultad de Biología, Universidad de Salamanca, 37185 Salamanca, Spain (L.S., M.F.-M., A.M., O.L.);Department of Biology and Center for Molecular Communication and Signaling, Wake Forest University, Winston-Salem, North Carolina 27106 (D.R.L., G.K.M.);Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, 28223 Pozuelo de Alarcón, Madrid, Spain (S.P.); andGrupo de Investigación en Polifenoles, Unidad de Nutrición y Bromatología, Universidad de Salamanca, 37007 Salamanca, Spain (M.D., C.S.-B.)
| | - Stephan Pollmann
- Departamento de Fisiología Vegetal, Instituto Hispano-Luso de Investigaciones Agrarias, Facultad de Biología, Universidad de Salamanca, 37185 Salamanca, Spain (L.S., M.F.-M., A.M., O.L.);Department of Biology and Center for Molecular Communication and Signaling, Wake Forest University, Winston-Salem, North Carolina 27106 (D.R.L., G.K.M.);Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, 28223 Pozuelo de Alarcón, Madrid, Spain (S.P.); andGrupo de Investigación en Polifenoles, Unidad de Nutrición y Bromatología, Universidad de Salamanca, 37007 Salamanca, Spain (M.D., C.S.-B.)
| | - Montserrat Dueñas
- Departamento de Fisiología Vegetal, Instituto Hispano-Luso de Investigaciones Agrarias, Facultad de Biología, Universidad de Salamanca, 37185 Salamanca, Spain (L.S., M.F.-M., A.M., O.L.);Department of Biology and Center for Molecular Communication and Signaling, Wake Forest University, Winston-Salem, North Carolina 27106 (D.R.L., G.K.M.);Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, 28223 Pozuelo de Alarcón, Madrid, Spain (S.P.); andGrupo de Investigación en Polifenoles, Unidad de Nutrición y Bromatología, Universidad de Salamanca, 37007 Salamanca, Spain (M.D., C.S.-B.)
| | - Celestino Santos-Buelga
- Departamento de Fisiología Vegetal, Instituto Hispano-Luso de Investigaciones Agrarias, Facultad de Biología, Universidad de Salamanca, 37185 Salamanca, Spain (L.S., M.F.-M., A.M., O.L.);Department of Biology and Center for Molecular Communication and Signaling, Wake Forest University, Winston-Salem, North Carolina 27106 (D.R.L., G.K.M.);Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, 28223 Pozuelo de Alarcón, Madrid, Spain (S.P.); andGrupo de Investigación en Polifenoles, Unidad de Nutrición y Bromatología, Universidad de Salamanca, 37007 Salamanca, Spain (M.D., C.S.-B.)
| | - Oscar Lorenzo
- Departamento de Fisiología Vegetal, Instituto Hispano-Luso de Investigaciones Agrarias, Facultad de Biología, Universidad de Salamanca, 37185 Salamanca, Spain (L.S., M.F.-M., A.M., O.L.);Department of Biology and Center for Molecular Communication and Signaling, Wake Forest University, Winston-Salem, North Carolina 27106 (D.R.L., G.K.M.);Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, 28223 Pozuelo de Alarcón, Madrid, Spain (S.P.); andGrupo de Investigación en Polifenoles, Unidad de Nutrición y Bromatología, Universidad de Salamanca, 37007 Salamanca, Spain (M.D., C.S.-B.)
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203
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Zhu T, Moschou PN, Alvarez JM, Sohlberg JJ, von Arnold S. Wuschel-related homeobox 8/9 is important for proper embryo patterning in the gymnosperm Norway spruce. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:6543-52. [PMID: 25205582 PMCID: PMC4246185 DOI: 10.1093/jxb/eru371] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Proper embryo development is crucial as that is when the primary body axes are established. In Arabidopsis, AtWOX8 and AtWOX9, members of the Wuschel-related homeobox (WOX) gene family, are critical for embryo development. In Norway spruce, PaWOX8/9, which is expressed in embryos, is the homologue of AtWOX8 and AtWOX9. In this work, it is shown that the transcript abundance of PaWOX8/9 is high during early and late embryogeny and that it decreases when the maturation phase starts. To address the function of PaWOX8/9 during embryo development, RNAi lines were established to down-regulate the transcript level of PaWOX8/9, using both constitutive and inducible promoters. Embryos in the PaWOX8/9 RNAi lines show an aberrant morphology caused by disturbed orientation of the cell division plane at the basal part of the embryonal mass during early and late embryogeny. In addition, the transcript level of several key cell-cycle-regulating genes, for example, PaE2FAB-like and PaCYCLIN B-like, are affected in the PaWOX8/9 RNAi lines. Taken together, our results suggest that PaWOX8/9 may perform an evolutionarily conserved function as a regulator of the establishment of the apical-basal embryo pattern.
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Affiliation(s)
- Tianqing Zhu
- Swedish University of Agricultural Sciences, Department of Plant Biology, Uppsala BioCenter, Linnean Center of Plant Biology in Uppsala, PO-Box 7080, SE-75007 Uppsala, Sweden
| | - Panagiotis N Moschou
- Swedish University of Agricultural Sciences, Department of Plant Biology, Uppsala BioCenter, Linnean Center of Plant Biology in Uppsala, PO-Box 7080, SE-75007 Uppsala, Sweden
| | - José M Alvarez
- Swedish University of Agricultural Sciences, Department of Plant Biology, Uppsala BioCenter, Linnean Center of Plant Biology in Uppsala, PO-Box 7080, SE-75007 Uppsala, Sweden
| | - Joel J Sohlberg
- Swedish University of Agricultural Sciences, Department of Plant Biology, Uppsala BioCenter, Linnean Center of Plant Biology in Uppsala, PO-Box 7080, SE-75007 Uppsala, Sweden
| | - Sara von Arnold
- Swedish University of Agricultural Sciences, Department of Plant Biology, Uppsala BioCenter, Linnean Center of Plant Biology in Uppsala, PO-Box 7080, SE-75007 Uppsala, Sweden
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204
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Schaller GE, Street IH, Kieber JJ. Cytokinin and the cell cycle. CURRENT OPINION IN PLANT BIOLOGY 2014; 21:7-15. [PMID: 24994531 DOI: 10.1016/j.pbi.2014.05.015] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Revised: 05/22/2014] [Accepted: 05/24/2014] [Indexed: 05/22/2023]
Abstract
The phytohormone cytokinin influences many aspects of plant growth and development, including a prominent role in the regulation of cell proliferation. How the cytokinin response pathway integrates into the machinery regulating progression through the cell cycle is only beginning to be appreciated. Cytokinin is generally considered to promote mitotic cell division in the shoot, but differentiation and transition to the endocycle in the root. Here we consider recent data on the inputs by which cytokinins positively and negatively regulate transitions through the cell cycle. Cytokinin positively regulates cell division and also serves a key role in establishing organization within shoot stem cell centers. Both auxin-dependent and auxin-independent mechanisms have been uncovered by which cytokinin stimulates the endocycle in roots. We conclude with a model that reconciles the opposing effects of cytokinin on shoot and root cell division.
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Affiliation(s)
- G Eric Schaller
- Dartmouth College, Department of Biological Sciences, Hanover, NH 03755, USA.
| | - Ian H Street
- Dartmouth College, Department of Biological Sciences, Hanover, NH 03755, USA
| | - Joseph J Kieber
- University of North Carolina, Biology Department, Chapel Hill, NC 27599, USA.
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205
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Bennett T, van den Toorn A, Willemsen V, Scheres B. Precise control of plant stem cell activity through parallel regulatory inputs. Development 2014; 141:4055-64. [PMID: 25256342 DOI: 10.1242/dev.110148] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The regulation of columella stem cell activity in the Arabidopsis root cap by a nearby organizing centre, the quiescent centre, has been a key example of the stem cell niche paradigm in plants. Here, we investigate interactions between transcription factors that have been shown to regulate columella stem cells using a simple quantification method for stem cell activity in the root cap. Genetic and expression analyses reveal that the RETINOBLASTOMA-RELATED protein, the FEZ and SOMBRERO NAC-domain transcription factors, the ARF10 and ARF16 auxin response factors and the quiescent centre-expressed WOX5 homeodomain protein each provide independent inputs to regulate the number of columella stem cells. Given the tight control of columella development, we found that these inputs act in a surprisingly parallel manner. Nevertheless, important points of interaction exist; for example, we demonstrate the repression of SMB activity by non-autonomous action of WOX5. Our results suggest that the developmental progression of columella stem cells may be quantitatively regulated by several more broadly acting transcription factors rather than by a single intrinsic stem cell factor, which raises questions about the special nature of the stem cell state in plants.
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Affiliation(s)
- Tom Bennett
- Department of Molecular Genetics, University of Utrecht, Padualaan 8, Utrecht 3584 CH, The Netherlands
| | - Albert van den Toorn
- Department of Molecular Genetics, University of Utrecht, Padualaan 8, Utrecht 3584 CH, The Netherlands Plant Developmental Biology, Wageningen University Research, Wageningen 6708 PB, The Netherlands
| | - Viola Willemsen
- Department of Molecular Genetics, University of Utrecht, Padualaan 8, Utrecht 3584 CH, The Netherlands Plant Developmental Biology, Wageningen University Research, Wageningen 6708 PB, The Netherlands
| | - Ben Scheres
- Department of Molecular Genetics, University of Utrecht, Padualaan 8, Utrecht 3584 CH, The Netherlands Plant Developmental Biology, Wageningen University Research, Wageningen 6708 PB, The Netherlands
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206
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Tian H, De Smet I, Ding Z. Shaping a root system: regulating lateral versus primary root growth. TRENDS IN PLANT SCIENCE 2014; 19:426-31. [PMID: 24513255 DOI: 10.1016/j.tplants.2014.01.007] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 01/04/2014] [Accepted: 01/14/2014] [Indexed: 05/22/2023]
Abstract
Primary and lateral roots comprise root systems, which are vital to the growth and survival of plants. Several molecular mechanisms associated with primary and lateral root growth have been described, including some common regulatory factors for their initiation and development. However, in this opinion article, we discuss the distinct growth behavior of lateral roots in response to environmental cues, such as salinity, gravity, and nutrient availability, which are mediated via specific regulators. We propose that differential growth dynamics between primary and lateral roots are crucial for plants to adapt to the ever-changing environmental conditions.
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Affiliation(s)
- Huiyu Tian
- The Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, Shandong 250100, PR China
| | - Ive De Smet
- Department of Plant Systems Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium; Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium; Division of Plant and Crop Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UK.
| | - Zhaojun Ding
- The Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, Shandong 250100, PR China.
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207
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Yang ZB, Geng X, He C, Zhang F, Wang R, Horst WJ, Ding Z. TAA1-regulated local auxin biosynthesis in the root-apex transition zone mediates the aluminum-induced inhibition of root growth in Arabidopsis. THE PLANT CELL 2014; 26:2889-904. [PMID: 25052716 PMCID: PMC4145121 DOI: 10.1105/tpc.114.127993] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Revised: 06/18/2014] [Accepted: 06/28/2014] [Indexed: 05/02/2023]
Abstract
The transition zone (TZ) of the root apex is the perception site of Al toxicity. Here, we show that exposure of Arabidopsis thaliana roots to Al induces a localized enhancement of auxin signaling in the root-apex TZ that is dependent on TAA1, which encodes a Trp aminotransferase and regulates auxin biosynthesis. TAA1 is specifically upregulated in the root-apex TZ in response to Al treatment, thus mediating local auxin biosynthesis and inhibition of root growth. The TAA1-regulated local auxin biosynthesis in the root-apex TZ in response to Al stress is dependent on ethylene, as revealed by manipulating ethylene homeostasis via the precursor of ethylene biosynthesis 1-aminocyclopropane-1-carboxylic acid, the inhibitor of ethylene biosynthesis aminoethoxyvinylglycine, or mutant analysis. In response to Al stress, ethylene signaling locally upregulates TAA1 expression and thus auxin responses in the TZ and results in auxin-regulated root growth inhibition through a number of auxin response factors (ARFs). In particular, ARF10 and ARF16 are important in the regulation of cell wall modification-related genes. Our study suggests a mechanism underlying how environmental cues affect root growth plasticity through influencing local auxin biosynthesis and signaling.
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Affiliation(s)
- Zhong-Bao Yang
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, College of Life Science, Shandong University, Jinan 250100, People's Republic of China
| | - Xiaoyu Geng
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, College of Life Science, Shandong University, Jinan 250100, People's Republic of China
| | - Chunmei He
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, College of Life Science, Shandong University, Jinan 250100, People's Republic of China
| | - Feng Zhang
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, College of Life Science, Shandong University, Jinan 250100, People's Republic of China
| | - Rong Wang
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, College of Life Science, Shandong University, Jinan 250100, People's Republic of China
| | - Walter J Horst
- Institute of Plant Nutrition, Leibniz Universität Hannover, 30419 Hannover, Germany
| | - Zhaojun Ding
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, College of Life Science, Shandong University, Jinan 250100, People's Republic of China
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208
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Abstract
The astonishingly long lives of plants and their regeneration capacity depend on the activity of plant stem cells. As in animals, stem cells reside in stem cell niches, which produce signals that regulate the balance between self-renewal and the generation of daughter cells that differentiate into new tissues. Plant stem cell niches are located within the meristems, which are organized structures that are responsible for most post-embryonic development. The continuous organ production that is characteristic of plant growth requires a robust regulatory network to keep the balance between pluripotent stem cells and differentiating progeny. Components of this network have now been elucidated and provide a unique opportunity for comparing strategies that were developed in the animal and plant kingdoms, which underlie the logic of stem cell behaviour.
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209
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Takatsuka H, Umeda M. Hormonal control of cell division and elongation along differentiation trajectories in roots. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:2633-43. [PMID: 24474807 DOI: 10.1093/jxb/ert485] [Citation(s) in RCA: 141] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The continuous development of roots is supported by a sustainable system for cell production and growth at the root tip. In the stem cell niche that consists of a quiescent centre and surrounding stem cells, an undifferentiated state and low mitotic activity are preserved by the action of auxin and abscisic acid. Stem cell daughters divide several times in the proximal meristem, where auxin and gibberellin mainly promote cell proliferation. Cells then elongate with the help of gibberellin, and become finally differentiated as a constituent of a cell file in the elongation/differentiation zone. In the model plant Arabidopsis thaliana, the transition zone is located between the proximal meristem and the elongation/differentiation zone, and plays an important role in switching from mitosis to the endoreplication that causes DNA polyploidization. Recent studies have shown that cytokinins are essentially required for this transition by antagonizing auxin signalling and promoting degradation of mitotic regulators. In each root zone, different phytohormones interact with one another and coordinately control cell proliferation, cell elongation, cell differentiation, and endoreplication. Such hormonal networks maintain the elaborate structure of the root tip under various environmental conditions. In this review, we summarize and discuss key issues related to hormonal regulation of root growth, and describe how phytohormones are associated with the control of cell cycle machinery.
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Affiliation(s)
- Hirotomo Takatsuka
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Takayama 8916-5, Ikoma, Nara 630-0192, Japan
| | - Masaaki Umeda
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Takayama 8916-5, Ikoma, Nara 630-0192, Japan JST, CREST, Takayama 8916-5, Ikoma, Nara 630-0192, Japan
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210
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Tian H, Jia Y, Niu T, Yu Q, Ding Z. The key players of the primary root growth and development also function in lateral roots in Arabidopsis. PLANT CELL REPORTS 2014; 33:745-53. [PMID: 24504658 DOI: 10.1007/s00299-014-1575-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 12/25/2013] [Accepted: 01/20/2014] [Indexed: 05/04/2023]
Abstract
The core regulators which are required for primary root growth and development also function in lateral root development or lateral root stem cell niche maintenance. The primary root systems and the lateral root systems are the two important root systems which are vital to the survival of plants. Though the molecular mechanism of the growth and development of both the primary root systems and the lateral root systems have been extensively studied individually in Arabidopsis, there are not so much evidence to show that if both root systems share common regulatory mechanisms. AP2 family transcription factors such as PLT1 (PLETHORA1) and PLT2, GRAS family transcription factors such as SCR (SCARECROW) and SHR (SHORT ROOT) and WUSCHEL-RELATED HOMEOBOX transcription factor WOX5 have been extensively studied and found to be essential for primary root growth and development. In this study, through the expression pattern analysis and mutant examinations, we found that these core regulators also function in lateral root development or lateral root stem cell niche maintenance.
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Affiliation(s)
- Huiyu Tian
- The Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, People's Republic of China
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211
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Tanaka H, Nodzyński T, Kitakura S, Feraru MI, Sasabe M, Ishikawa T, Kleine-Vehn J, Kakimoto T, Friml J. BEX1/ARF1A1C is required for BFA-sensitive recycling of PIN auxin transporters and auxin-mediated development in Arabidopsis. PLANT & CELL PHYSIOLOGY 2014; 55:737-49. [PMID: 24369434 PMCID: PMC3982122 DOI: 10.1093/pcp/pct196] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 12/09/2013] [Indexed: 05/18/2023]
Abstract
Correct positioning of membrane proteins is an essential process in eukaryotic organisms. The plant hormone auxin is distributed through intercellular transport and triggers various cellular responses. Auxin transporters of the PIN-FORMED (PIN) family localize asymmetrically at the plasma membrane (PM) and mediate the directional transport of auxin between cells. A fungal toxin, brefeldin A (BFA), inhibits a subset of guanine nucleotide exchange factors for ADP-ribosylation factor small GTPases (ARF GEFs) including GNOM, which plays a major role in localization of PIN1 predominantly to the basal side of the PM. The Arabidopsis genome encodes 19 ARF-related putative GTPases. However, ARF components involved in PIN1 localization have been genetically poorly defined. Using a fluorescence imaging-based forward genetic approach, we identified an Arabidopsis mutant, bfa-visualized exocytic trafficking defective1 (bex1), in which PM localization of PIN1-green fluorescent protein (GFP) as well as development is hypersensitive to BFA. We found that in bex1 a member of the ARF1 gene family, ARF1A1C, was mutated. ARF1A1C localizes to the trans-Golgi network/early endosome and Golgi apparatus, acts synergistically to BEN1/MIN7 ARF GEF and is important for PIN recycling to the PM. Consistent with the developmental importance of PIN proteins, functional interference with ARF1 resulted in an impaired auxin response gradient and various developmental defects including embryonic patterning defects and growth arrest. Our results show that ARF1A1C is essential for recycling of PIN auxin transporters and for various auxin-dependent developmental processes.
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Affiliation(s)
- Hirokazu Tanaka
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka, 560-0043 Japan
- *Corresponding author: E-mail, ; Fax, +81-(0)6-6850-5984
| | - Tomasz Nodzyński
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology (CEITEC), Masaryk University (MU), Kamenice 5, Brno, CZ-625 00 Czech Republic
| | - Saeko Kitakura
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka, 560-0043 Japan
| | - Mugurel I. Feraru
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Science (BOKU), Vienna, 1190 Austria
| | - Michiko Sasabe
- Faculty of Agriculture and Life Science, Hirosaki University, Aomori, 036-8561 Japan
| | - Tomomi Ishikawa
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka, 560-0043 Japan
| | - Jürgen Kleine-Vehn
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Science (BOKU), Vienna, 1190 Austria
| | - Tatsuo Kakimoto
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka, 560-0043 Japan
| | - Jiří Friml
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology (CEITEC), Masaryk University (MU), Kamenice 5, Brno, CZ-625 00 Czech Republic
- Institute of Science and Technology Austria (IST Austria), Klosterneuburg, 3400 Austria
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212
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Tian H, Wabnik K, Niu T, Li H, Yu Q, Pollmann S, Vanneste S, Govaerts W, Rolcík J, Geisler M, Friml J, Ding Z. WOX5-IAA17 feedback circuit-mediated cellular auxin response is crucial for the patterning of root stem cell niches in Arabidopsis. MOLECULAR PLANT 2014; 7:277-89. [PMID: 23939433 DOI: 10.1093/mp/sst118] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
In plants, the patterning of stem cell-enriched meristems requires a graded auxin response maximum that emerges from the concerted action of polar auxin transport, auxin biosynthesis, auxin metabolism, and cellular auxin response machinery. However, mechanisms underlying this auxin response maximum-mediated root stem cell maintenance are not fully understood. Here, we present unexpected evidence that WUSCHEL-RELATED HOMEOBOX 5 (WOX5) transcription factor modulates expression of auxin biosynthetic genes in the quiescent center (QC) of the root and thus provides a robust mechanism for the maintenance of auxin response maximum in the root tip. This WOX5 action is balanced through the activity of indole-3-acetic acid 17 (IAA17) auxin response repressor. Our combined genetic, cell biology, and computational modeling studies revealed a previously uncharacterized feedback loop linking WOX5-mediated auxin production to IAA17-dependent repression of auxin responses. This WOX5-IAA17 feedback circuit further assures the maintenance of auxin response maximum in the root tip and thereby contributes to the maintenance of distal stem cell (DSC) populations. Our experimental studies and in silico computer simulations both demonstrate that the WOX5-IAA17 feedback circuit is essential for the maintenance of auxin gradient in the root tip and the auxin-mediated root DSC differentiation.
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Affiliation(s)
- Huiyu Tian
- The Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Shanda Nanlu 27, Jinan 250100, China
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Abstract
ROPs (Rho of plants) belong to a large family of plant-specific Rho-like small GTPases that function as essential molecular switches to control diverse cellular processes including cytoskeleton organization, cell polarization, cytokinesis, cell differentiation and vesicle trafficking. Although the machineries of vesicle trafficking and cell polarity in plants have been individually well addressed, how ROPs co-ordinate those processes is still largely unclear. Recent progress has been made towards an understanding of the co-ordination of ROP signalling and trafficking of PIN (PINFORMED) transporters for the plant hormone auxin in both root and leaf pavement cells. PIN transporters constantly shuttle between the endosomal compartments and the polar plasma membrane domains, therefore the modulation of PIN-dependent auxin transport between cells is a main developmental output of ROP-regulated vesicle trafficking. The present review focuses on these cellular mechanisms, especially the integration of ROP-based vesicle trafficking and plant cell polarity.
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214
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Motte H, Vereecke D, Geelen D, Werbrouck S. The molecular path to in vitro shoot regeneration. Biotechnol Adv 2014; 32:107-21. [DOI: 10.1016/j.biotechadv.2013.12.002] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 11/20/2013] [Accepted: 12/08/2013] [Indexed: 10/25/2022]
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215
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Hong LW, Yan DW, Liu WC, Chen HG, Lu YT. TIME FOR COFFEE controls root meristem size by changes in auxin accumulation in Arabidopsis. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:275-86. [PMID: 24277277 PMCID: PMC3883298 DOI: 10.1093/jxb/ert374] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Roots play important roles in plant survival and productivity as they not only anchor the plants in the soil but are also the primary organ for the uptake of nutrients from the outside. The growth and development of roots depend on the specification and maintenance of the root meristem. Here, we report a previously unknown role of TIME FOR COFFEE (TIC) in controlling root meristem size in Arabidopsis. The results showed that loss of function of TIC reduced root meristem length and cell number by decreasing the competence of meristematic cells to divide. This was due to the repressed expression of PIN genes for decreased acropetal auxin transport in tic-2, leading to low auxin accumulation in the roots responsible for reduced root meristem, which was verified by exogenous application of indole-3-acetic acid. Downregulated expression of PLETHORA1 (PLT1) and PLT2, key transcription factors in mediating the patterning of the root stem cell niche, was also assayed in tic-2. Similar results were obtained with tic-2 and wild-type plants at either dawn or dusk. We also suggested that the MYC2-mediated jasmonic acid signalling pathway may not be involved in the regulation of TIC in controlling the root meristem. Taken together, these results suggest that TIC functions in an auxin-PLTs loop for maintenance of post-embryonic root meristem.
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Affiliation(s)
- Li-Wei Hong
- College of Life Sciences, Wuhan University, Wuhan 430072, PR China
| | - Da-Wei Yan
- College of Life Sciences, Wuhan University, Wuhan 430072, PR China
| | - Wen-Cheng Liu
- College of Life Sciences, Wuhan University, Wuhan 430072, PR China
| | - Hong-Guo Chen
- College of Chemistry and Biology, Hubei University of Science and Technology, Xianning 437100, Hubei Province, PR China
| | - Ying-Tang Lu
- College of Life Sciences, Wuhan University, Wuhan 430072, PR China
- * To whom correspondence should be addressed. E-mail:
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216
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Bustos-Sanmamed P, Mao G, Deng Y, Elouet M, Khan GA, Bazin JRM, Turner M, Subramanian S, Yu O, Crespi M, Lelandais-Bri Re C. Overexpression of miR160 affects root growth and nitrogen-fixing nodule number in Medicago truncatula. FUNCTIONAL PLANT BIOLOGY : FPB 2013; 40:1208-1220. [PMID: 32481189 DOI: 10.1071/fp13123] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 08/21/2013] [Indexed: 05/13/2023]
Abstract
Auxin action is mediated by a complex signalling pathway involving transcription factors of the auxin response factor (ARF) family. In Arabidopsis, microRNA160 (miR160) negatively regulates three ARF genes (ARF10/ARF16/ARF17) and therefore controls several developmental processes, including primary and lateral root growth. Here, we analysed the role of miR160 in root development and nodulation in Medicago truncatula Gaertn. Bioinformatic analyses identified two main mtr-miR160 variants (mtr-miR160abde and mtr-miR160c) and 17 predicted ARF targets. The miR160-dependent cleavage of four predicted targets in roots was confirmed by analysis of parallel analysis of RNA ends (PARE) data and RACE-PCR experiments. Promoter-GUS analyses for mtr-miR160d and mtr-miR160c genes revealed overlapping but distinct expression profiles during root and nodule development. In addition, the early miR160 activation in roots during symbiotic interaction was not observed in mutants of the nodulation signalling or autoregulation pathways. Composite plants that overexpressed mtr-miR160a under two different promoters exhibited distinct defects in root growth and nodulation: the p35S:miR160a construct led to reduced root length associated to a severe disorganisation of the RAM, whereas pCsVMV:miR160a roots showed gravitropism defects and lower nodule numbers. Our results suggest that a regulatory loop involving miR160/ARFs governs root and nodule organogenesis in M. truncatula.
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Affiliation(s)
- Pilar Bustos-Sanmamed
- Institut des Sciences du Végétal (ISV), Centre National de la Recherche Scientifique (CNRS), Gif sur Yvette F-91198 Gif-sur-Yvette Cedex, France
| | - Guohong Mao
- Donald Danforth Plant Science Center, St Louis, MO 63132, USA
| | - Ying Deng
- Donald Danforth Plant Science Center, St Louis, MO 63132, USA
| | - Morgane Elouet
- Institut des Sciences du Végétal (ISV), Centre National de la Recherche Scientifique (CNRS), Gif sur Yvette F-91198 Gif-sur-Yvette Cedex, France
| | - Ghazanfar Abbas Khan
- Institut des Sciences du Végétal (ISV), Centre National de la Recherche Scientifique (CNRS), Gif sur Yvette F-91198 Gif-sur-Yvette Cedex, France
| | - J R Mie Bazin
- Institut des Sciences du Végétal (ISV), Centre National de la Recherche Scientifique (CNRS), Gif sur Yvette F-91198 Gif-sur-Yvette Cedex, France
| | - Marie Turner
- Department of Plant Science, Department of Biology and Microbiology, South Dakota State University, Brookings, SD 57007, USA
| | - Senthil Subramanian
- Department of Plant Science, Department of Biology and Microbiology, South Dakota State University, Brookings, SD 57007, USA
| | - Oliver Yu
- Donald Danforth Plant Science Center, St Louis, MO 63132, USA
| | - Martin Crespi
- Institut des Sciences du Végétal (ISV), Centre National de la Recherche Scientifique (CNRS), Gif sur Yvette F-91198 Gif-sur-Yvette Cedex, France
| | - Christine Lelandais-Bri Re
- Institut des Sciences du Végétal (ISV), Centre National de la Recherche Scientifique (CNRS), Gif sur Yvette F-91198 Gif-sur-Yvette Cedex, France
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217
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Moubayidin L, Di Mambro R, Sozzani R, Pacifici E, Salvi E, Terpstra I, Bao D, van Dijken A, Dello Ioio R, Perilli S, Ljung K, Benfey PN, Heidstra R, Costantino P, Sabatini S. Spatial coordination between stem cell activity and cell differentiation in the root meristem. Dev Cell 2013; 26:405-15. [PMID: 23987513 DOI: 10.1016/j.devcel.2013.06.025] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Revised: 05/20/2013] [Accepted: 06/26/2013] [Indexed: 01/06/2023]
Abstract
A critical issue in development is the coordination of the activity of stem cell niches with differentiation of their progeny to ensure coherent organ growth. In the plant root, these processes take place at opposite ends of the meristem and must be coordinated with each other at a distance. Here, we show that in Arabidopsis, the gene SCR presides over this spatial coordination. In the organizing center of the root stem cell niche, SCR directly represses the expression of the cytokinin-response transcription factor ARR1, which promotes cell differentiation, controlling auxin production via the ASB1 gene and sustaining stem cell activity. This allows SCR to regulate, via auxin, the level of ARR1 expression in the transition zone where the stem cell progeny leaves the meristem, thus controlling the rate of differentiation. In this way, SCR simultaneously controls stem cell division and differentiation, ensuring coherent root growth.
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Affiliation(s)
- Laila Moubayidin
- Dipartimento di Biologia e Biotecnologie, Laboratory of Functional Genomics and Proteomics of Model Systems, Università di Roma, Sapienza, via dei Sardi, 70-00185 Rome, Italy
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218
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Della Rovere F, Fattorini L, D'Angeli S, Veloccia A, Falasca G, Altamura MM. Auxin and cytokinin control formation of the quiescent centre in the adventitious root apex of Arabidopsis. ANNALS OF BOTANY 2013; 112:1395-407. [PMID: 24061489 PMCID: PMC3806543 DOI: 10.1093/aob/mct215] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 08/05/2013] [Indexed: 05/18/2023]
Abstract
BACKGROUND AND AIMS Adventitious roots (ARs) are part of the root system in numerous plants, and are required for successful micropropagation. In the Arabidopsis thaliana primary root (PR) and lateral roots (LRs), the quiescent centre (QC) in the stem cell niche of the meristem controls apical growth with the involvement of auxin and cytokinin. In arabidopsis, ARs emerge in planta from the hypocotyl pericycle, and from different tissues in in vitro cultured explants, e.g. from the stem endodermis in thin cell layer (TCL) explants. The aim of this study was to investigate the establishment and maintenance of the QC in arabidopsis ARs, in planta and in TCL explants, because information about this process is still lacking, and it has potential use for biotechnological applications. METHODS Expression of PR/LR QC markers and auxin influx (LAX3)/efflux (PIN1) genes was investigated in the presence/absence of exogenous auxin and cytokinin. Auxin was monitored by the DR5::GUS system and cytokinin by immunolocalization. The expression of the auxin-biosynthetic YUCCA6 gene was also investigated by in situ hybridization in planta and in AR-forming TCLs from the indole acetic acid (IAA)-overproducing superroot2-1 mutant and its wild type. KEY RESULTS The accumulation of auxin and the expression of the QC marker WOX5 characterized the early derivatives of the AR founder cells, in planta and in in vitro cultured TCLs. By determination of PIN1 auxin efflux carrier and LAX3 auxin influx carrier activities, an auxin maximum was determined to occur at the AR tip, to which WOX5 expression was restricted, establishing the positioning of the QC. Cytokinin caused a restriction of LAX3 and PIN1 expression domains, and concomitantly the auxin biosynthesis YUCCA6 gene was expressed in the apex. CONCLUSIONS In ARs formed in planta and TCLs, the QC is established in a similar way, and auxin transport and biosynthesis are involved through cytokinin tuning.
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219
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Vanneste S, Friml J. Calcium: The Missing Link in Auxin Action. PLANTS (BASEL, SWITZERLAND) 2013; 2:650-75. [PMID: 27137397 PMCID: PMC4844386 DOI: 10.3390/plants2040650] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 10/07/2013] [Accepted: 10/10/2013] [Indexed: 01/18/2023]
Abstract
Due to their sessile lifestyles, plants need to deal with the limitations and stresses imposed by the changing environment. Plants cope with these by a remarkable developmental flexibility, which is embedded in their strategy to survive. Plants can adjust their size, shape and number of organs, bend according to gravity and light, and regenerate tissues that were damaged, utilizing a coordinating, intercellular signal, the plant hormone, auxin. Another versatile signal is the cation, Ca(2+), which is a crucial second messenger for many rapid cellular processes during responses to a wide range of endogenous and environmental signals, such as hormones, light, drought stress and others. Auxin is a good candidate for one of these Ca(2+)-activating signals. However, the role of auxin-induced Ca(2+) signaling is poorly understood. Here, we will provide an overview of possible developmental and physiological roles, as well as mechanisms underlying the interconnection of Ca(2+) and auxin signaling.
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Affiliation(s)
- Steffen Vanneste
- Plant Systems Biology, VIB, and Plant Biotechnology and Bio-informatics, Ghent University, Ghent 9052, Belgium.
| | - Jiří Friml
- Plant Systems Biology, VIB, and Plant Biotechnology and Bio-informatics, Ghent University, Ghent 9052, Belgium
- Institute of Science and Technology Austria (IST Austria), Klosterneuburg 3400, Austria
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220
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Zhang W, Swarup R, Bennett M, Schaller GE, Kieber JJ. Cytokinin induces cell division in the quiescent center of the Arabidopsis root apical meristem. Curr Biol 2013; 23:1979-89. [PMID: 24120642 DOI: 10.1016/j.cub.2013.08.008] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 07/12/2013] [Accepted: 08/06/2013] [Indexed: 12/23/2022]
Abstract
BACKGROUND In the root apical meristem, which contains the stem cells that feed into root development, the phytohormones auxin and cytokinin play opposing roles, with auxin promoting cell division and cytokinin promoting cell differentiation. Cytokinin acts in the root tip in part by modulating auxin transport through regulation of the level of the PIN auxin efflux carriers. Auxin plays a key role in the specification of the quiescent center (QC), which is essential for maintaining the stem cell fate of the surrounding cells. RESULTS We demonstrate that cytokinin promotes cell division in the QC, which is generally mitotically inactive. Cytokinin downregulates the expression of several key regulatory genes in the root tip, including SCARECROW, WOX5, and the auxin influx carriers AUX1 and LAX2. The decrease in LAX2 expression in response to cytokinin requires ARR1 and ARR12, two type B ARRs that mediate the primary transcriptional response to cytokinin. ARR1 was found to bind directly to the LAX2 gene in vivo, which indicates that type B ARRs directly regulate genes that are repressed by cytokinin. Disruption of the LAX2 gene results in a phenotype similar to that observed in response to cytokinin, including increased division of the cells in the QC and decreased expression of WOX5 and the auxin response reporter DR5. CONCLUSIONS Cytokinin acts to regulate auxin distribution in the root apical meristem by regulating both the PINs and LAX2. This redistribution of auxin, potentially coupled with other auxin-independent effects of cytokinin, regulates the mitotic activity in the QC.
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Affiliation(s)
- Wenjing Zhang
- Biology Department, University of North Carolina, CB#3280, Chapel Hill, NC 27599, USA
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221
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Plant stem cell maintenance involves direct transcriptional repression of differentiation program. Mol Syst Biol 2013; 9:654. [PMID: 23549482 PMCID: PMC3658276 DOI: 10.1038/msb.2013.8] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Accepted: 02/18/2013] [Indexed: 01/16/2023] Open
Abstract
In animal systems, master regulatory transcription factors (TFs) mediate stem cell maintenance through a direct transcriptional repression of differentiation promoting TFs. Whether similar mechanisms operate in plants is not known. In plants, shoot apical meristems serve as reservoirs of stem cells that provide cells for all above ground organs. WUSCHEL, a homeodomain TF produced in cells of the niche, migrates into adjacent cells where it specifies stem cells. Through high-resolution genomic analysis, we show that WUSCHEL represses a large number of genes that are expressed in differentiating cells including a group of differentiation promoting TFs involved in leaf development. We show that WUS directly binds to the regulatory regions of differentiation promoting TFs; KANADI1, KANADI2, ASYMMETRICLEAVES2 and YABBY3 to repress their expression. Predictions from a computational model, supported by live imaging, reveal that WUS-mediated repression prevents premature differentiation of stem cell progenitors, being part of a minimal regulatory network for meristem maintenance. Our work shows that direct transcriptional repression of differentiation promoting TFs is an evolutionarily conserved logic for stem cell regulation.
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222
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de Vega-Bartol JJ, Simões M, Lorenz WW, Rodrigues AS, Alba R, Dean JFD, Miguel CM. Transcriptomic analysis highlights epigenetic and transcriptional regulation during zygotic embryo development of Pinus pinaster. BMC PLANT BIOLOGY 2013; 13:123. [PMID: 23987738 PMCID: PMC3844413 DOI: 10.1186/1471-2229-13-123] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2013] [Accepted: 08/24/2013] [Indexed: 05/18/2023]
Abstract
BACKGROUND It is during embryogenesis that the plant body plan is established and the meristems responsible for all post-embryonic growth are specified. The molecular mechanisms governing conifer embryogenesis are still largely unknown. Their elucidation may contribute valuable information to clarify if the distinct features of embryo development in angiosperms and gymnosperms result from differential gene regulation. To address this issue, we have performed the first transcriptomic analysis of zygotic embryo development in a conifer species (Pinus pinaster) focusing our study in particular on regulatory genes playing important roles during plant embryo development, namely epigenetic regulators and transcription factors. RESULTS Microarray analysis of P. pinaster zygotic embryogenesis was performed at five periods of embryo development from early developing to mature embryos. Our results show that most changes in transcript levels occurred in the first and the last embryo stage-to-stage transitions, namely early to pre-cotyledonary embryo and cotyledonary to mature embryo. An analysis of functional categories for genes that were differentially expressed through embryogenesis highlighted several epigenetic regulation mechanisms. While putative orthologs of transcripts associated with mechanisms that target transposable elements and repetitive sequences were strongly expressed in early embryogenesis, PRC2-mediated repression of genes seemed more relevant during late embryogenesis. On the other hand, functions related to sRNA pathways appeared differentially regulated across all stages of embryo development with a prevalence of miRNA functions in mid to late embryogenesis. Identification of putative transcription factor genes differentially regulated between consecutive embryo stages was strongly suggestive of the relevance of auxin responses and regulation of auxin carriers during early embryogenesis. Such responses could be involved in establishing embryo patterning. Later in development, transcripts with homology to genes acting on modulation of auxin flow and determination of adaxial-abaxial polarity were up-regulated, as were putative orthologs of genes required for meristem formation and function as well as establishment of organ boundaries. Comparative analysis with A. thaliana embryogenesis also highlighted genes involved in auxin-mediated responses, as well as epigenetic regulation, indicating highly correlated transcript profiles between the two species. CONCLUSIONS This is the first report of a time-course transcriptomic analysis of zygotic embryogenesis in a conifer. Taken together our results show that epigenetic regulation and transcriptional control related to auxin transport and response are critical during early to mid stages of pine embryogenesis and that important events during embryogenesis seem to be coordinated by putative orthologs of major developmental regulators in angiosperms.
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Affiliation(s)
- José J de Vega-Bartol
- iBET - Instituto de Biologia Experimental e Tecnológica, Apartado 12, 2780-901 Oeiras, Portugal
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, 2780-157 Oeiras, Portugal
| | - Marta Simões
- iBET - Instituto de Biologia Experimental e Tecnológica, Apartado 12, 2780-901 Oeiras, Portugal
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, 2780-157 Oeiras, Portugal
| | - W Walter Lorenz
- Warnell School of Forestry and Natural Resources, The University of Georgia, Athens, GA 30602, USA
| | - Andreia S Rodrigues
- iBET - Instituto de Biologia Experimental e Tecnológica, Apartado 12, 2780-901 Oeiras, Portugal
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, 2780-157 Oeiras, Portugal
| | - Rob Alba
- Monsanto Company, Mailstop CC4, 700 Chesterfield Parkway West, Chesterfield, MO 63017, USA
| | - Jeffrey F D Dean
- Warnell School of Forestry and Natural Resources, The University of Georgia, Athens, GA 30602, USA
| | - Célia M Miguel
- iBET - Instituto de Biologia Experimental e Tecnológica, Apartado 12, 2780-901 Oeiras, Portugal
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, 2780-157 Oeiras, Portugal
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223
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Gliwicka M, Nowak K, Balazadeh S, Mueller-Roeber B, Gaj MD. Extensive modulation of the transcription factor transcriptome during somatic embryogenesis in Arabidopsis thaliana. PLoS One 2013; 8:e69261. [PMID: 23874927 PMCID: PMC3714258 DOI: 10.1371/journal.pone.0069261] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 06/10/2013] [Indexed: 11/19/2022] Open
Abstract
Molecular mechanisms controlling plant totipotency are largely unknown and studies on somatic embryogenesis (SE), the process through which already differentiated cells reverse their developmental program and become embryogenic, provide a unique means for deciphering molecular mechanisms controlling developmental plasticity of somatic cells. Among various factors essential for embryogenic transition of somatic cells transcription factors (TFs), crucial regulators of genetic programs, are believed to play a central role. Herein, we used quantitative real-time polymerase chain reaction (qRT-PCR) to identify TF genes affected during SE induced by in vitro culture in Arabidopsis thaliana. Expression profiles of 1,880 TFs were evaluated in the highly embryogenic Col-0 accession and the non-embryogenic tanmei/emb2757 mutant. Our study revealed 729 TFs whose expression changes during the 10-days incubation period of SE; 141 TFs displayed distinct differences in expression patterns in embryogenic versus non-embryogenic cultures. The embryo-induction stage of SE occurring during the first 5 days of culture was associated with a robust and dramatic change of the TF transcriptome characterized by the drastic up-regulation of the expression of a great majority (over 80%) of the TFs active during embryogenic culture. In contrast to SE induction, the advanced stage of embryo formation showed attenuation and stabilization of transcript levels of many TFs. In total, 519 of the SE-modulated TFs were functionally annotated and transcripts related with plant development, phytohormones and stress responses were found to be most abundant. The involvement of selected TFs in SE was verified using T-DNA insertion lines and a significantly reduced embryogenic response was found for the majority of them. This study provides comprehensive data focused on the expression of TF genes during SE and suggests directions for further research on functional genomics of SE.
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Affiliation(s)
- Marta Gliwicka
- Department of Genetics, University of Silesia, Katowice, Poland
| | - Katarzyna Nowak
- Department of Genetics, University of Silesia, Katowice, Poland
| | - Salma Balazadeh
- Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
- Max-Planck Institute of Molecular Plant Physiology, Potsdam-Golm, Germany
| | - Bernd Mueller-Roeber
- Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
- Max-Planck Institute of Molecular Plant Physiology, Potsdam-Golm, Germany
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224
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Peng Y, Chen L, Lu Y, Ma W, Tong Y, Li Y. DAR2 acts as an important node connecting cytokinin, auxin, SHY2 and PLT1/2 in root meristem size control. PLANT SIGNALING & BEHAVIOR 2013; 8:e24226. [PMID: 23518585 PMCID: PMC3907457 DOI: 10.4161/psb.24226] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 03/07/2013] [Indexed: 05/20/2023]
Abstract
Cytokinin and auxin antagonistically affect cell proliferation and differentiation and thus regulate root meristem size by influencing the abundance of SHORT HYPOCOTYL2 (SHY2/IAA3). SHY2 affects auxin distribution in the root meristem by repressing the auxin-inducible expression of PIN-FORMED (PIN) auxin transport genes. The PLETHORA (PLT1/2) genes influence root meristem growth by promoting stem cells and transit-amplifying cells. However, the factors connecting cytokinin, auxin, SHY2 and PLT1/2 are largely unknown. In a recent study, we have shown that the DA1-related protein 2 (DAR2) acts downstream of cytokinin and SHY2 but upstream of PLT1/2 to affect root meristem size. Here, we discuss the possible molecular mechanisms by which Arabidopsis DAR2 controls root meristem size.
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225
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Barrio RA, Romero-Arias JR, Noguez MA, Azpeitia E, Ortiz-Gutiérrez E, Hernández-Hernández V, Cortes-Poza Y, Álvarez-Buylla ER. Cell patterns emerge from coupled chemical and physical fields with cell proliferation dynamics: the Arabidopsis thaliana root as a study system. PLoS Comput Biol 2013; 9:e1003026. [PMID: 23658505 PMCID: PMC3642054 DOI: 10.1371/journal.pcbi.1003026] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 02/25/2013] [Indexed: 11/18/2022] Open
Abstract
A central issue in developmental biology is to uncover the mechanisms by which stem cells maintain their capacity to regenerate, yet at the same time produce daughter cells that differentiate and attain their ultimate fate as a functional part of a tissue or an organ. In this paper we propose that, during development, cells within growing organs obtain positional information from a macroscopic physical field that is produced in space while cells are proliferating. This dynamical interaction triggers and responds to chemical and genetic processes that are specific to each biological system. We chose the root apical meristem of Arabidopsis thaliana to develop our dynamical model because this system is well studied at the molecular, genetic and cellular levels and has the key traits of multicellular stem-cell niches. We built a dynamical model that couples fundamental molecular mechanisms of the cell cycle to a tension physical field and to auxin dynamics, both of which are known to play a role in root development. We perform extensive numerical calculations that allow for quantitative comparison with experimental measurements that consider the cellular patterns at the root tip. Our model recovers, as an emergent pattern, the transition from proliferative to transition and elongation domains, characteristic of stem-cell niches in multicellular organisms. In addition, we successfully predict altered cellular patterns that are expected under various applied auxin treatments or modified physical growth conditions. Our modeling platform may be extended to explicitly consider gene regulatory networks or to treat other developmental systems. The emergence of tumors results from altered cell differentiation and proliferation during organ and tissue development. Understanding how such altered or normal patterns are established is still a challenge. Molecular genetic approaches to understanding pattern formation have searched for key central genetic controllers. However, biological patterns emerge as a consequence of coupled complex genetic and non-genetic sub-systems operating at various spatial and temporal scales and levels of organization. We present a two-dimensional model and simulation benchmark that considers the integrated dynamics of physical and chemical fields that result from cell proliferation. We aim at understanding how the cellular patterns of stem-cell niches emerge. In these, organizer cells with very low rates of proliferation are surrounded by stem cells with slightly higher proliferation rates that transit to a domain of active proliferation and then of elongation and differentiation. We quantified such cellular patterns in the Arabidopsis thaliana root to test our theoretical propositions. The results of our simulations closely mimic observed root cellular patterns, thus providing a proof of principle that coupled physical fields and chemical processes under active cell proliferation give rise to stem-cell patterns. Our framework may be extended to other developmental systems and to consider gene regulatory networks.
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Affiliation(s)
- Rafael A. Barrio
- Instituto de Física, Universidad Nacional Autónoma de México (UNAM), México, Distrito Federal, México
- * E-mail: (RAB); (ERAB)
| | - José Roberto Romero-Arias
- Instituto de Física, Universidad Nacional Autónoma de México (UNAM), México, Distrito Federal, México
| | - Marco A. Noguez
- Universidad Autónoma de la Ciudad de México, Mexico, Distrito Federal, México
| | - Eugenio Azpeitia
- Instituto de Ecología, Universidad Nacional Autónoma de México, México, Distrito Federal, México
- Centro de Ciencias de la Complejidad-C3, Universidad Nacional Autónoma de México, Distrito Federal, México
| | - Elizabeth Ortiz-Gutiérrez
- Instituto de Ecología, Universidad Nacional Autónoma de México, México, Distrito Federal, México
- Centro de Ciencias de la Complejidad-C3, Universidad Nacional Autónoma de México, Distrito Federal, México
| | - Valeria Hernández-Hernández
- Instituto de Ecología, Universidad Nacional Autónoma de México, México, Distrito Federal, México
- Centro de Ciencias de la Complejidad-C3, Universidad Nacional Autónoma de México, Distrito Federal, México
| | - Yuriria Cortes-Poza
- Centro de Ciencias de la Complejidad-C3, Universidad Nacional Autónoma de México, Distrito Federal, México
| | - Elena R. Álvarez-Buylla
- Instituto de Ecología, Universidad Nacional Autónoma de México, México, Distrito Federal, México
- Centro de Ciencias de la Complejidad-C3, Universidad Nacional Autónoma de México, Distrito Federal, México
- * E-mail: (RAB); (ERAB)
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226
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Kong Y, Zhu Y, Gao C, She W, Lin W, Chen Y, Han N, Bian H, Zhu M, Wang J. Tissue-specific expression of SMALL AUXIN UP RNA41 differentially regulates cell expansion and root meristem patterning in Arabidopsis. PLANT & CELL PHYSIOLOGY 2013; 54:609-21. [PMID: 23396598 DOI: 10.1093/pcp/pct028] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Among the three primary auxin-induced gene families, Auxin/Indole-3-Acetic Acid (Aux/IAA), Gretchen Hagen3 (GH3) and SMALL AUXIN UP RNA (SAUR), the function of SAUR genes remains unclear. Arabidopsis SAUR genes have been phylogenetically classified into three clades. Recent work has suggested that SAUR19 (clade II) and SAUR63 (clade I) promote cell expansion through the modulation of auxin transport. Herein, we present our work on SAUR41, a clade III SAUR gene with a distinctive expression pattern in root meristems. SAUR41 was normally expressed in the quiescent center and cortex/endodermis initials; upon auxin stimulation, the expression was provoked in the endodermal layer. During lateral root development, SAUR41 was expressed in prospective stem cell niches of lateral root primordia and in expanding endodermal cells surrounding the primordia. SAUR41-EGFP (enhanced green fluorescent protein) fusion proteins localized to the cytoplasm. Overexpression of SAUR41 from the Cauliflower mosaic virus 35S promoter led to pleiotropic auxin-related phenotypes, including long hypocotyls, increased vegetative biomass and lateral root development, expanded petals and twisted inflorescence stems. Ectopic SAUR41 proteins were able to promote auxin transport in hypocotyls. Tissue-specific expression of SAUR41 from the PIN1, WOX5, PLT2 and ACR4 promoters induced the formation of new auxin accumulation/signaling peaks above the quiescent centers, whereas tissue-specific expression of SAUR41 from the PIN2 and PLT2 promoters enhanced root gravitropic growth. Cells in the root stem cell niches of these transgenic seedlings were differentially enlarged. The distinctive expression pattern of the SAUR41 gene and the explicit function of SAUR41 proteins implied that further investigations on the loss-of-function phenotypes of this gene in root development and environmental responses are of great interest.
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Affiliation(s)
- Yingying Kong
- Institute of Genetics, College of Life Sciences, Zhejiang University, Zijingang Campus, Hangzhou 310058, China
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227
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Perturbation of auxin homeostasis by overexpression of wild-type IAA15 results in impaired stem cell differentiation and gravitropism in roots. PLoS One 2013; 8:e58103. [PMID: 23472140 PMCID: PMC3589423 DOI: 10.1371/journal.pone.0058103] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 02/03/2013] [Indexed: 12/23/2022] Open
Abstract
Aux/IAAs interact with auxin response factors (ARFs) to repress their transcriptional activity in the auxin signaling pathway. Previous studies have focused on gain-of-function mutations of domain II and little is known about whether the expression level of wild-type Aux/IAAs can modulate auxin homeostasis. Here we examined the perturbation of auxin homeostasis by ectopic expression of wild-type IAA15. Root gravitropism and stem cell differentiation were also analyzed. The transgenic lines were less sensitive to exogenous auxin and exhibited low-auxin phenotypes including failures in gravity response and defects in stem cell differentiation. Overexpression lines also showed an increase in auxin concentration and reduced polar auxin transport. These results demonstrate that an alteration in the expression of wild-type IAA15 can disrupt auxin homeostasis.
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228
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Peng Y, Ma W, Chen L, Yang L, Li S, Zhao H, Zhao Y, Jin W, Li N, Bevan MW, Li X, Tong Y, Li Y. Control of root meristem size by DA1-RELATED PROTEIN2 in Arabidopsis. PLANT PHYSIOLOGY 2013; 161:1542-56. [PMID: 23296689 PMCID: PMC3585615 DOI: 10.1104/pp.112.210237] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Accepted: 01/03/2013] [Indexed: 05/21/2023]
Abstract
The control of organ growth by coordinating cell proliferation and differentiation is a fundamental developmental process. In plants, postembryonic root growth is sustained by the root meristem. For maintenance of root meristem size, the rate of cell differentiation must equal the rate of cell division. Cytokinin and auxin interact to affect the cell proliferation and differentiation balance and thus control root meristem size. However, the genetic and molecular mechanisms that determine root meristem size still remain largely unknown. Here, we report that da1-related protein2 (dar2) mutants produce small root meristems due to decreased cell division and early cell differentiation in the root meristem of Arabidopsis (Arabidopsis thaliana). dar2 mutants also exhibit reduced stem cell niche activity in the root meristem. DAR2 encodes a Lin-11, Isl-1, and Mec-3 domain-containing protein and shows an expression peak in the border between the transition zone and the elongation zone. Genetic analyses show that DAR2 functions downstream of cytokinin and SHORT HYPOCOTYL2 to maintain normal auxin distribution by influencing auxin transport. Further results indicate that DAR2 acts through the PLETHORA pathway to influence root stem cell niche activity and therefore control root meristem size. Collectively, our findings identify the role of DAR2 in root meristem size control and provide a novel link between several key regulators influencing root meristem size.
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229
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Ballesteros I, Domínguez T, Sauer M, Paredes P, Duprat A, Rojo E, Sanmartín M, Sánchez-Serrano JJ. Specialized functions of the PP2A subfamily II catalytic subunits PP2A-C3 and PP2A-C4 in the distribution of auxin fluxes and development in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 73:862-72. [PMID: 23167545 DOI: 10.1111/tpj.12078] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 11/12/2012] [Accepted: 11/16/2012] [Indexed: 05/09/2023]
Abstract
Protein phosphorylation is a key molecular switch used to transmit information in biological signalling networks. The output of these signalling circuits is governed by the counteracting activities of protein kinases and phosphatases that determine the direction of the switch. Whereas many kinases have been functionally characterized, it has been difficult to ascribe precise cellular roles to plant phosphatases, which are encoded by enlarged gene families that may provide a high degree of genetic redundancy. In this work we have analysed the role in planta of catalytic subunits of protein phosphatase 2A (PP2A), a family encoded by five genes in Arabidopsis. Our results indicate that the two members of subfamily II, PP2A-C3 and PP2A-C4, have redundant functions in controlling embryo patterning and root development, processes that depend on auxin fluxes. Moreover, polarity of the auxin efflux carrier PIN1 and auxin distribution, determined with the DR5(pro) :GFP proxy, are affected by mutations in PP2A-C3 and PP2A-C4. Previous characterization of mutants in putative PP2A regulatory subunits had established a link between this class of phosphatases and PIN dephosphorylation and subcellular distribution. Building on those findings, the results presented here suggest that PP2A-C3 and PP2A-C4 catalyse this reaction and contribute critically to the establishment of auxin gradients for proper plant development.
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Affiliation(s)
- Isabel Ballesteros
- Departamento de Genética Molecular de Plantas, Centro Nacional de Biotecnología CSIC, Campus Universidad Autónoma de Madrid, Cta. Colmenar Viejo km. 15,500, 28049 Madrid, Spain
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230
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Lee Y, Lee WS, Kim SH. Hormonal regulation of stem cell maintenance in roots. JOURNAL OF EXPERIMENTAL BOTANY 2013. [PMID: 23183258 DOI: 10.1093/jxb/ers331] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
During plant embryogenesis, the apical-basal axis is established and both the shoot apical meristem (SAM) and the root apical meristem (RAM) are formed. In both meristems, there are slowly dividing cells which control the differentiation of their surrounding cells called the organizing centre (OC) and the quiescent centre (QC) in the shoot and root, respectively. These centres with their surrounding initial cells form a 'stem cell niche'. The initial cells eventually differentiate into various plant tissues, giving rise to plant organs such as lateral shoots, flowers, leaves, and lateral roots. Plant hormones are important factors involved in the balance between cell division and differentiation such that plant growth and development are tightly controlled in space and time. No single hormone acts by itself in regulating the meristematic activity in the root meristem. Division and differentiation are controlled by interactions between several hormones. Intensive research on plant stem cells has focused on how cell division is regulated to form specific plant organs and tissues, how differentiation is controlled, and how stem cell fate is coordinated. In this review, recent knowledge pertaining to the role of plant hormones in maintaining root stem cells including the QC is summarized and discussed. Furthermore, we suggest diverse approaches to answering the main question of how root stem cells are regulated and maintained by plant hormones.
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Affiliation(s)
- Yew Lee
- Division of Biological Science and Technology, Yonsei University, Wonju 220-710, Republic of Korea
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231
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Shen C, Wang S, Zhang S, Xu Y, Qian Q, Qi Y, Jiang DA. OsARF16, a transcription factor, is required for auxin and phosphate starvation response in rice (Oryza sativa L.). PLANT, CELL & ENVIRONMENT 2013; 36:607-20. [PMID: 22913536 DOI: 10.1111/pce.12001] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Plant responses to auxin and phosphate (Pi) starvation are closely linked. However, the underlying mechanisms connecting auxin to phosphate starvation (-Pi) responses are largely unclear. Here, we show that OsARF16, an auxin response factor, functions in both auxin and -Pi responses in rice (Oryza sativa L.). The knockout of OsARF16 led to primary roots (PR), lateral roots (LR) and root hair losing sensitivity to auxin and -Pi response. OsARF16 expression and OsARF16::GUS staining in PR and LR of rice Nipponbare (NIP) were induced by indole acetic acid and -Pi treatments. In -Pi conditions, the shoot biomass of osarf16 was slightly reduced, and neither root growth nor iron content was induced, indicating that the knockout of OsARF16 led to loss of response to Pi deficiency in rice. Six phosphate starvation-induced genes (PSIs) were less induced by -Pi in osarf16 and these trends were similar to a knockdown mutant of OsPHR2 or AtPHR1, which was a key regulator under -Pi. These data first reveal the biological function of OsARF16, provide novel evidence of a linkage between auxin and -Pi responses and facilitate the development of new strategies for the efficient utilization of Pi in rice.
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Affiliation(s)
- Chenjia Shen
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
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232
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Yao X, Feng H, Yu Y, Dong A, Shen WH. SDG2-mediated H3K4 methylation is required for proper Arabidopsis root growth and development. PLoS One 2013; 8:e56537. [PMID: 23483879 PMCID: PMC3585709 DOI: 10.1371/journal.pone.0056537] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Accepted: 01/10/2013] [Indexed: 01/25/2023] Open
Abstract
Trithorax group (TrxG) proteins are evolutionarily conserved in eukaryotes and play critical roles in transcriptional activation via deposition of histone H3 lysine 4 trimethylation (H3K4me3) in chromatin. Several Arabidopsis TrxG members have been characterized, and among them SET DOMAIN GROUP 2 (SDG2) has been shown to be necessary for global genome-wide H3K4me3 deposition. Although pleiotropic phenotypes have been uncovered in the sdg2 mutants, SDG2 function in the regulation of stem cell activity has remained largely unclear. Here, we investigate the sdg2 mutant root phenotype and demonstrate that SDG2 is required for primary root stem cell niche (SCN) maintenance as well as for lateral root SCN establishment. Loss of SDG2 results in drastically reduced H3K4me3 levels in root SCN and differentiated cells and causes the loss of auxin gradient maximum in the root quiescent centre. Elevated DNA damage is detected in the sdg2 mutant, suggesting that impaired genome integrity may also have challenged the stem cell activity. Genetic interaction analysis reveals that SDG2 and CHROMATIN ASSEMBLY FACTOR-1 act synergistically in root SCN and genome integrity maintenance but not in telomere length maintenance. We conclude that SDG2-mediated H3K4me3 plays a distinctive role in the regulation of chromatin structure and genome integrity, which are key features in pluripotency of stem cells and crucial for root growth and development.
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Affiliation(s)
- Xiaozhen Yao
- State Key Laboratory of Genetic Engineering, International Associated Laboratory of CNRS-Fudan-HUNAU on Plant Epigenome Research, School of Life Sciences, Fudan University, Shanghai, PR China
| | - Haiyang Feng
- State Key Laboratory of Genetic Engineering, International Associated Laboratory of CNRS-Fudan-HUNAU on Plant Epigenome Research, School of Life Sciences, Fudan University, Shanghai, PR China
| | - Yu Yu
- State Key Laboratory of Genetic Engineering, International Associated Laboratory of CNRS-Fudan-HUNAU on Plant Epigenome Research, School of Life Sciences, Fudan University, Shanghai, PR China
| | - Aiwu Dong
- State Key Laboratory of Genetic Engineering, International Associated Laboratory of CNRS-Fudan-HUNAU on Plant Epigenome Research, School of Life Sciences, Fudan University, Shanghai, PR China
| | - Wen-Hui Shen
- State Key Laboratory of Genetic Engineering, International Associated Laboratory of CNRS-Fudan-HUNAU on Plant Epigenome Research, School of Life Sciences, Fudan University, Shanghai, PR China
- Institut de Biologie Moléculaire des Plantes du CNRS, Université de Strasbourg, Strasbourg Cedex, France
- * E-mail:
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233
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Abstract
Organogenesis is the developmental process for producing new organs from undifferentiated cells. In plants, most organs are formed during postembryonic development. Shoot lateral organs are generated in the shoot apical meristem whereas lateral roots develop outside the root apical meristem. While lateral organ formation at the shoot and root might seem quite different, recent genetic studies have highlighted numerous parallels between these processes. In particular, the dynamic accumulation of auxin has been shown to play a crucial role both as a "morphogenetic trigger" and as a morphogen in both phenomena. This suggests that a unique model system could be adopted to study organogenesis in plants. In this chapter we describe the conceptual and technical advantages that support lateral root development as a good model system for studying organogenesis in plants.
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234
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Tian H, Niu T, Yu Q, Quan T, Ding Z. Auxin gradient is crucial for the maintenance of root distal stem cell identity in Arabidopsis. PLANT SIGNALING & BEHAVIOR 2013; 8:e26429. [PMID: 24056047 PMCID: PMC4106507 DOI: 10.4161/psb.26429] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The plant hormone auxin plays a critical role in the maintenance of root stem cell niches in Arabidopsis. We have recently reported that WUSCHEL-RELATED HOMEOBOX 5 (WOX5) transcription factor modulates free auxin production in the quiescent center (QC) of the root and its expression is inhibited in a feedback-dependent manner by canonical auxin signaling that involves indole-3-acetic acid 17 (IAA17) auxin response repressor. WOX5-IAA17 feedback circuit assures the maintenance of auxin response maximum in the root tip and thereby contributes to the maintenance of distal stem cell (DSC) populations. Here, we provide evidence to show that an optimal auxin maximum in QC guided auxin signaling gradient in root tips is crucial for maintaining root DSC identity.
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235
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Moriwaki T, Miyazawa Y, Kobayashi A, Takahashi H. Molecular mechanisms of hydrotropism in seedling roots of Arabidopsis thaliana (Brassicaceae). AMERICAN JOURNAL OF BOTANY 2013; 100:25-34. [PMID: 23263156 DOI: 10.3732/ajb.1200419] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Roots show positive hydrotropism in response to moisture gradients, which is believed to contribute to plant water acquisition. This article reviews the recent advances of the physiological and molecular genetic studies on hydrotropism in seedling roots of Arabidopsis thaliana. We identified MIZU-KUSSEI1 (MIZ1) and MIZ2, essential genes for hydrotropism in roots; the former encodes a protein of unknown function, and the latter encodes an ARF-GEF (GNOM) protein involved in vesicle trafficking. Because both mutants are defective in hydrotropism but not in gravitropism, these mutations might affect a molecular mechanism unique to hydrotropism. MIZ1 is expressed in the lateral root cap and cortex of the root proper. It is localized as a soluble protein in the cytoplasm and in association with the cytoplasmic face of endoplasmic reticulum (ER) membranes in root cells. Light and ABA independently regulate MIZ1 expression, which influences the ultimate hydrotropic response. In addition, MIZ1 overexpression results in an enhancement of hydrotropism and an inhibition of lateral root formation. This phenotype is likely related to the alteration of auxin content in roots. Specifically, the auxin level in the roots decreases in the MIZ1 overexpressor and increases in the miz1 mutant. Unlike most gnom mutants, miz2 displays normal morphology, growth, and gravitropism, with normal localization of PIN proteins. It is probable that MIZ1 plays a crucial role in hydrotropic response by regulating the endogenous level of auxin in Arabidopsis roots. Furthermore, the role of GNOM/MIZ2 in hydrotropism is distinct from that of gravitropism.
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Affiliation(s)
- Teppei Moriwaki
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
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236
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Bargmann BOR, Vanneste S, Krouk G, Nawy T, Efroni I, Shani E, Choe G, Friml J, Bergmann DC, Estelle M, Birnbaum KD. A map of cell type-specific auxin responses. Mol Syst Biol 2013; 9:688. [PMID: 24022006 PMCID: PMC3792342 DOI: 10.1038/msb.2013.40] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 07/23/2013] [Indexed: 12/31/2022] Open
Abstract
In plants, changes in local auxin concentrations can trigger a range of developmental processes as distinct tissues respond differently to the same auxin stimulus. However, little is known about how auxin is interpreted by individual cell types. We performed a transcriptomic analysis of responses to auxin within four distinct tissues of the Arabidopsis thaliana root and demonstrate that different cell types show competence for discrete responses. The majority of auxin-responsive genes displayed a spatial bias in their induction or repression. The novel data set was used to examine how auxin influences tissue-specific transcriptional regulation of cell-identity markers. Additionally, the data were used in combination with spatial expression maps of the root to plot a transcriptomic auxin-response gradient across the apical and basal meristem. The readout revealed a strong correlation for thousands of genes between the relative response to auxin and expression along the longitudinal axis of the root. This data set and comparative analysis provide a transcriptome-level spatial breakdown of the response to auxin within an organ where this hormone mediates many aspects of development.
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Affiliation(s)
- Bastiaan O R Bargmann
- Biology Department, Center for Genomics and Systems Biology, New York University, New York, NY, USA
- Department of Cell and Developmental Biology, UCSD, La Jolla, CA, USA
| | - Steffen Vanneste
- Department of Plant Systems Biology, VIB, Ghent, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
| | - Gabriel Krouk
- Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, Institut de Biologie Intégrative des Plantes—Claude Grignon, Montpellier, France
| | - Tal Nawy
- Biology Department, Center for Genomics and Systems Biology, New York University, New York, NY, USA
| | - Idan Efroni
- Biology Department, Center for Genomics and Systems Biology, New York University, New York, NY, USA
| | - Eilon Shani
- Department of Cell and Developmental Biology, UCSD, La Jolla, CA, USA
| | - Goh Choe
- Department of Cell and Developmental Biology, UCSD, La Jolla, CA, USA
| | - Jiří Friml
- Department of Plant Systems Biology, VIB, Ghent, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
- Institute of Science and Technology Austria (IST Austria), Klosterneuburg, Austria
| | | | - Mark Estelle
- Department of Cell and Developmental Biology, UCSD, La Jolla, CA, USA
| | - Kenneth D Birnbaum
- Biology Department, Center for Genomics and Systems Biology, New York University, New York, NY, USA
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237
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Azpeitia E, Alvarez-Buylla ER. A complex systems approach to Arabidopsis root stem-cell niche developmental mechanisms: from molecules, to networks, to morphogenesis. PLANT MOLECULAR BIOLOGY 2012; 80:351-63. [PMID: 22945341 DOI: 10.1007/s11103-012-9954-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Accepted: 08/15/2012] [Indexed: 05/11/2023]
Abstract
Recent reports have shown that the molecular mechanisms involved in root stem-cell niche development in Arabidopsis thaliana are complex and contain several feedback loops and non-additive interactions that need to be analyzed using computational and formal approaches. Complex systems cannot be understood in terms of the behavior of their isolated components, but they emerge as a consequence of largely non-linear interactions among their components. The study of complex systems has provided a useful approach for the exploration of system-level characteristics and behaviors of the molecular networks involved in cell differentiation and morphogenesis during development. We analyzed the complex molecular networks underlying stem-cell niche patterning in the A. thaliana root in terms of some of the key dynamic traits of complex systems: self-organization, modularity and structural properties. We use these analyses to integrate the available root stem-cell niche molecular mechanisms data and postulate novel hypotheses, missing components and interactions and explain apparent contradictions in the literature.
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Affiliation(s)
- Eugenio Azpeitia
- Laboratorio de Genética Molecular, Desarrollo y Evolución de Plantas, Centro de Ciencias de la Complejidad (C3), Universidad Nacional Autónoma de México, Coyoacán, Mexico, DF, Mexico
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238
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Garay-Arroyo A, De La Paz Sánchez M, García-Ponce B, Azpeitia E, Álvarez-Buylla ER. Hormone symphony during root growth and development. Dev Dyn 2012; 241:1867-85. [DOI: 10.1002/dvdy.23878] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/17/2012] [Indexed: 01/29/2023] Open
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239
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Bassa C, Mila I, Bouzayen M, Audran-Delalande C. Phenotypes associated with down-regulation of Sl-IAA27 support functional diversity among Aux/IAA family members in tomato. PLANT & CELL PHYSIOLOGY 2012; 53:1583-95. [PMID: 22764281 DOI: 10.1093/pcp/pcs101] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The phytohormone auxin is known to regulate several aspects of plant development, and Aux/IAA transcription factors play a pivotal role in auxin signaling. To extend our understanding of the multiple functions of Aux/IAAs further, the present study describes the functional characterization of Sl-IAA27, a member of the tomato Aux/IAA gene family. Sl-IAA27 displays a distinct behavior compared with most Aux/IAA genes regarding the regulation of its expression by auxin, and the Sl-IAA27-encoded protein harbors a unique motif of unknown function also present in Sl-IAA9 and remarkably conserved in monocot and dicot species. Tomato transgenic plants underexpressing the Sl-IAA27 gene revealed multiple phenotypes related to vegetative and reproductive growth. Silencing of Sl-IAA27 results in higher auxin sensitivity, altered root development and reduced Chl content in leaves. Both ovule and pollen display a dramatic loss of fertility in Sl-IAA27 down-regulated lines, and the internal anatomy of the flower and the fruit are modified, with an enlarged placenta in smaller fruits. In line with the reduced Chl content in Sl-IAA27 RNA interference (RNAi) leaves, genes involved in Chl synthesis display lower expression at the level of transcript accumulation. Even though Sl-IAA27 is closely related to Sl-IAA9 in terms of sequence homology and the encoded proteins share common structural features, the data indicate that the two genes regulate tomato fruit initiation and development in a distinct manner.
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Affiliation(s)
- Carole Bassa
- Université de Toulouse, INP-ENSA Toulouse, Génomique et Biotechnologie des Fruits, Avenue de l'Agrobiopole BP 32607, Castanet-Tolosan F-31326, France
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240
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Kinoshita N, Wang H, Kasahara H, Liu J, Macpherson C, Machida Y, Kamiya Y, Hannah MA, Chua NH. IAA-Ala Resistant3, an evolutionarily conserved target of miR167, mediates Arabidopsis root architecture changes during high osmotic stress. THE PLANT CELL 2012; 24:3590-602. [PMID: 22960911 PMCID: PMC3480289 DOI: 10.1105/tpc.112.097006] [Citation(s) in RCA: 136] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The functions of microRNAs and their target mRNAs in Arabidopsis thaliana development have been widely documented; however, roles of stress-responsive microRNAs and their targets are not as well understood. Using small RNA deep sequencing and ATH1 microarrays to profile mRNAs, we identified IAA-Ala Resistant3 (IAR3) as a new target of miR167a. As expected, IAR3 mRNA was cleaved at the miR167a complementary site and under high osmotic stress miR167a levels decreased, whereas IAR3 mRNA levels increased. IAR3 hydrolyzes an inactive form of auxin (indole-3-acetic acid [IAA]-alanine) and releases bioactive auxin (IAA), a central phytohormone for root development. In contrast with the wild type, iar3 mutants accumulated reduced IAA levels and did not display high osmotic stress-induced root architecture changes. Transgenic plants expressing a cleavage-resistant form of IAR3 mRNA accumulated high levels of IAR3 mRNAs and showed increased lateral root development compared with transgenic plants expressing wild-type IAR3. Expression of an inducible noncoding RNA to sequester miR167a by target mimicry led to an increase in IAR3 mRNA levels, further confirming the inverse relationship between the two partners. Sequence comparison revealed the miR167 target site on IAR3 mRNA is conserved in evolutionarily distant plant species. Finally, we showed that IAR3 is required for drought tolerance.
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MESH Headings
- Amidohydrolases/genetics
- Amidohydrolases/metabolism
- Arabidopsis/genetics
- Arabidopsis/growth & development
- Arabidopsis/physiology
- Arabidopsis Proteins/genetics
- Arabidopsis Proteins/metabolism
- Biological Evolution
- Droughts
- Gene Expression Profiling
- Gene Expression Regulation, Plant/genetics
- High-Throughput Nucleotide Sequencing
- Hydroponics
- Indoleacetic Acids/metabolism
- MicroRNAs/genetics
- MicroRNAs/metabolism
- Models, Biological
- Oligonucleotide Array Sequence Analysis
- Osmosis
- Phenotype
- Plant Growth Regulators/metabolism
- Plant Leaves/genetics
- Plant Leaves/growth & development
- Plant Leaves/physiology
- Plant Roots/genetics
- Plant Roots/growth & development
- Plant Roots/physiology
- Plants, Genetically Modified/genetics
- Plants, Genetically Modified/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Plant/genetics
- RNA, Plant/metabolism
- Sequence Analysis, DNA
- Stress, Physiological/genetics
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Affiliation(s)
- Natsuko Kinoshita
- Laboratory of Plant Molecular Biology, The Rockefeller University, New York, NY 10065, USA
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241
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ER-localized auxin transporter PIN8 regulates auxin homeostasis and male gametophyte development in Arabidopsis. Nat Commun 2012; 3:941. [PMID: 22760640 DOI: 10.1038/ncomms1941] [Citation(s) in RCA: 204] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 05/31/2012] [Indexed: 02/02/2023] Open
Abstract
Auxin is a key coordinative signal required for many aspects of plant development and its levels are controlled by auxin metabolism and intercellular auxin transport. Here we find that a member of PIN auxin transporter family, PIN8 is expressed in male gametophyte of Arabidopsis thaliana and has a crucial role in pollen development and functionality. Ectopic expression in sporophytic tissues establishes a role of PIN8 in regulating auxin homoeostasis and metabolism. PIN8 co-localizes with PIN5 to the endoplasmic reticulum (ER) where it acts as an auxin transporter. Genetic analyses reveal an antagonistic action of PIN5 and PIN8 in the regulation of intracellular auxin homoeostasis and gametophyte as well as sporophyte development. Our results reveal a role of the auxin transport in male gametophyte development in which the distinct actions of ER-localized PIN transporters regulate cellular auxin homoeostasis and maintain the auxin levels optimal for pollen development and pollen tube growth.
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242
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Du J, Yin H, Zhang S, Wei Z, Zhao B, Zhang J, Gou X, Lin H, Li J. Somatic embryogenesis receptor kinases control root development mainly via brassinosteroid-independent actions in Arabidopsis thaliana. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2012; 54:388-399. [PMID: 22525267 DOI: 10.1111/j.1744-7909.2012.01124.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Brassinosteroids (BRs), a group of plant steroidal hormones, play critical roles in many aspects of plant growth and development. Previous studies showed that BRI1-mediated BR signaling regulates cell division and differentiation during Arabidopsis root development via interplaying with auxin and other phytohormones. Arabidopsis somatic embryogenesis receptor-like kinases (SERKs), as co-receptors of BRI1, were found to play a fundamental role in an early activation step of BR signaling pathway. Here we report a novel function of SERKs in regulating Arabidopsis root development. Genetic analyses indicated that SERKs control root growth mainly via a BR-independent pathway. Although BR signaling pathway is completely disrupted in the serk1 bak1 bkk1 triple mutant, the root growth of the triple mutant is much severely damaged than the BR deficiency or signaling null mutants. More detailed analyses indicated that the triple mutant exhibited drastically reduced expression of a number of genes critical to polar auxin transport, cell cycle, endodermis development and root meristem differentiation, which were not observed in null BR biosynthesis mutant cpd and null BR signaling mutant bri1-701.
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Affiliation(s)
- Junbo Du
- School of Life Sciences, Sichuan University, Sichuan 610064, China
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243
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Lee M, Jung JH, Han DY, Seo PJ, Park WJ, Park CM. Activation of a flavin monooxygenase gene YUCCA7 enhances drought resistance in Arabidopsis. PLANTA 2012; 235:923-38. [PMID: 22109847 DOI: 10.1007/s00425-011-1552-3] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Accepted: 11/07/2011] [Indexed: 05/18/2023]
Abstract
Auxin regulates diverse molecular and physiological events at the cellular and organismal levels during plant growth and development in response to environmental stimuli. It acts either through distinct signaling pathways or in concert with other growth hormones. Its biological functions are adjusted by modulating biosynthesis, conjugate formation, and polar transport and distribution. Several tryptophan-dependent and -independent auxin biosynthetic pathways have been proposed. Recent studies have shown that a few flavin monooxygenase enzymes contribute to the tryptophan-dependent auxin biosynthesis. Here, we show that activation of a flavin monooxygenase gene YUCCA7 (YUC7), which belongs to the tryptophan-dependent auxin biosynthetic pathway, enhances drought resistance. An Arabidopsis activation-tagged mutant yuc7-1D exhibited phenotypic changes similar to those observed in auxin-overproducing mutants, such as tall, slender stems and curled, narrow leaves. Accordingly, endogenous levels of total auxin were elevated in the mutant. The YUC7 gene was induced by drought, primarily in the roots, in an abscisic acid (ABA)-dependent manner. The yuc7-1D mutant was resistant to drought, and drought-responsive genes, such as RESPONSIVE TO DESSICATION 29A (RD29A) and COLD-REGULATED 15A (COR15A), were up-regulated in the mutant. Interestingly, whereas stomatal aperture and production of osmoprotectants were not discernibly altered, lateral root growth was significantly promoted in the yuc7-1D mutant when grown under drought conditions. These observations support that elevation of auxin levels in the roots enhances drought resistance possibly by promoting root growth.
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Affiliation(s)
- Minyoung Lee
- Department of Chemistry, Seoul National University, Seoul, 151-742, Korea
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244
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Hendelman A, Buxdorf K, Stav R, Kravchik M, Arazi T. Inhibition of lamina outgrowth following Solanum lycopersicum AUXIN RESPONSE FACTOR 10 (SlARF10) derepression. PLANT MOLECULAR BIOLOGY 2012; 78:561-76. [PMID: 22287097 DOI: 10.1007/s11103-012-9883-4] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2011] [Accepted: 01/12/2012] [Indexed: 05/04/2023]
Abstract
Auxin response factors (ARFs) are plant transcription factors that activate or repress the expression of auxin-responsive genes and accordingly, play key roles in auxin-mediated developmental processes. Here we identified and characterized the Solanum lycopersicum (tomato) ARF10 homolog (SlARF10), demonstrated that it is posttranscriptionally regulated by Sl-miR160, and investigated the significance of this regulation for tomato development. In wild-type tomato, SlARF10 is primarily expressed in the pericarp of mature and ripened fruit, showing an expression profile complementary to that of Sl-miR160. Constitutive expression of wild-type SlARF10 did not alter tomato development. However, transgenic tomato plants that constitutively expressed the Sl-miR160a-resistant version (mSlARF10) developed narrow leaflet blades, sepals and petals, and abnormally shaped fruit. During compound leaf development, mSlARF10 accumulation specifically inhibited leaflet blade outgrowth without affecting other auxin-driven processes such as leaflet initiation and lobe formation. Moreover, blade size was inversely correlated with mSlARF10 transcript levels, strongly implying that the SlARF10 protein, which was localized to the nucleus, can function as a transcriptional repressor of leaflet lamina outgrowth. Accordingly, known auxin-responsive genes, which promote cell growth, were downregulated in shoot apices that accumulated increased mSlARF10 levels. Taken together, we propose that repression of SlARF10 by Sl-miR160 is essential for auxin-mediated blade outgrowth and early fruit development.
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Affiliation(s)
- A Hendelman
- Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, P.O. Box 6, 50250 Bet Dagan, Israel
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245
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Durbak A, Yao H, McSteen P. Hormone signaling in plant development. CURRENT OPINION IN PLANT BIOLOGY 2012; 15:92-6. [PMID: 22244082 DOI: 10.1016/j.pbi.2011.12.004] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 12/23/2011] [Accepted: 12/23/2011] [Indexed: 05/20/2023]
Abstract
Hormone signaling plays diverse and critical roles during plant development. In particular, hormone interactions regulate meristem function and therefore control formation of all organs in the plant. Recent advances have dissected commonalities and differences in the interaction of auxin and cytokinin in the regulation of shoot and root apical meristem function. In addition, brassinosteroid hormones have recently been discovered to regulate root apical meristem size. Further insights have also been made into our understanding of the mechanism of crosstalk among auxin, cytokinin, and strigolactone in axillary meristems.
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Affiliation(s)
- Amanda Durbak
- Division of Biological Sciences, Interdisciplinary Plant Group, Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, United States
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246
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Qi Y, Wang S, Shen C, Zhang S, Chen Y, Xu Y, Liu Y, Wu Y, Jiang D. OsARF12, a transcription activator on auxin response gene, regulates root elongation and affects iron accumulation in rice (Oryza sativa). THE NEW PHYTOLOGIST 2012; 193:109-120. [PMID: 21973088 DOI: 10.1111/j.1469-8137.2011.03910.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
• Auxin has an important role in maintaining optimal root system architecture (RSA) that can cope with growth reductions of crops caused by water or nutrient shortages. However, the mechanism of controlling RSA remains largely unclear. Here, we found a limiting factor of RSA--OsARF12--an auxin response factor whose knockout led to decreased primary root length in rice (Oryza sativa). • OsARF12 as a transcription activator can facilitate the expression of the auxin response element DR5::GFP, and OsARF12 was inhibited by osa-miRNA167d by transient expression in tobacco and rice callus. • The root elongation zones of osarf12 and osarf12/25, which had lower auxin concentrations, were distinctly shorter than for the wild-type, possibly as a result of decreased expression of auxin synthesis genes OsYUCCAs and auxin efflux carriers OsPINs and OsPGPs. The knockout of OsARF12 also altered the abundance of mitochondrial iron-regulated (OsMIR), iron (Fe)-regulated transporter1 (OsIRT1) and short postembryonic root1 (OsSPR1) in roots of rice, and resulted in lower Fe content. • The data provide evidence for the biological function of OsARF12, which is implicated in regulating root elongation. Our investigation contributes a novel insight for uncovering regulation of RSA and the relationship between auxin response and Fe acquisition.
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Affiliation(s)
| | | | - ChenJia Shen
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - SaiNa Zhang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Yue Chen
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - YanXia Xu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Yu Liu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - YunRong Wu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - DeAn Jiang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
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247
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Abstract
Multicellular organisms possess pluripotent stem cells to form new organs, replenish the daily loss of cells, or regenerate organs after injury. Stem cells are maintained in specific environments, the stem cell niches, that provide signals to block differentiation. In plants, stem cell niches are situated in the shoot, root, and vascular meristems-self-perpetuating units of organ formation. Plants' lifelong activity-which, as in the case of trees, can extend over more than a thousand years-requires that a robust regulatory network keep the balance between pluripotent stem cells and differentiating descendants. In this review, we focus on current models in plant stem cell research elaborated during the past two decades, mainly in the model plant Arabidopsis thaliana. We address the roles of mobile signals on transcriptional modules involved in balancing cell fates. In addition, we discuss shared features of and differences between the distinct stem cell niches of Arabidopsis.
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Affiliation(s)
- Ernst Aichinger
- BIOSS Centre for Biological Signalling Studies, Faculty of Biology, University of Freiburg, Freiburg, Germany
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248
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Gu XL, Wang H, Huang H, Cui XF. SPT6L encoding a putative WG/GW-repeat protein regulates apical-basal polarity of embryo in Arabidopsis. MOLECULAR PLANT 2012; 5:249-259. [PMID: 21948524 DOI: 10.1093/mp/ssr073] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In eukaryotes, a protein motif consisting of WG/GW repeats, also called the Argonaute (AGO) hook, is thought to be essential for binding AGO proteins to fulfill their functions in RNA-mediated gene silencing. Although a number of WG/GW-containing proteins have been computationally identified in Arabidopsis, their roles in plant growth and development are unknown. Here, we show that the Arabidopsis Suppressor of Ty insertion 6-like (SPT6L) gene, which encodes a protein with C-terminal WG/GW repeats, plays critical roles in embryonic development. SPT6L is evolutionarily conserved only in vascular plants, with varying numbers of C-terminal WG/GW repeats, which are plant-species specific. spt6l mutants formed embryos with an aberrant apical-basal axis, showing insufficient development of the basal domain and embryonic lethality. Expression domains of the class-III homeodomain-leucine zipper (HD-ZIP III) genes PHABULOSA (PHB) and PHAVOLUTA (PHV) were expanded in the spt6l embryo. In contrast, the PLETHORA1 (PLT1) gene, which acts antagonistically to the HD-ZIP III genes in specification of basal fate, was severely down-regulated in the spt6l mutant. Furthermore, the phb phv double mutations partially rescued aberrant basal development in the spt6l background and restored PLT1 expression. Collectively, our results indicate that SPT6L is essential for specification of the apical-basal axis, partly by controlling the HD-ZIP III genes in embryos.
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Affiliation(s)
- Xiao-Lu Gu
- National Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
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249
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Hernández-Barrera A, Ugartechea-Chirino Y, Shishkova S, Napsucialy-Mendivil S, Soukup A, Reyes-Hernández BJ, Lira-Ruan V, Dong G, Dubrovsky JG. Apical meristem exhaustion during determinate primary root growth in the moots koom 1 mutant of Arabidopsis thaliana. PLANTA 2011; 234:1163-1177. [PMID: 21744091 DOI: 10.1007/s00425-011-1470-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Accepted: 06/22/2011] [Indexed: 05/31/2023]
Abstract
An indeterminate developmental program allows plant organs to grow continuously by maintaining functional meristems over time. The molecular mechanisms involved in the maintenance of the root apical meristem are not completely understood. We have identified a new Arabidopsis thaliana mutant named moots koom 1 (mko1) that showed complete root apical meristem exhaustion of the primary root by 9 days post-germination. MKO1 is essential for maintenance of root cell proliferation. In the mutant, cell division is uncoupled from cell growth in the region corresponding to the root apical meristem. We established the sequence of cellular events that lead to meristem exhaustion in this mutant. Interestingly, the SCR and WOX5 promoters were active in the mko1 quiescent center at all developmental stages. However, during meristem exhaustion, the mutant root tip showed defects in starch accumulation in the columella and changes in auxin response pattern. Therefore, contrary to many described mutants, the determinate growth in mko1 seedlings does not appear to be a consequence of incorrect establishment or affected maintenance of the quiescent center but rather of cell proliferation defects both in stem cell niche and in the rest of the apical meristem. Our results support a model whereby the MKO1 gene plays an important role in the maintenance of the root apical meristem proliferative capacity and indeterminate root growth, which apparently acts independently of the SCR/SHR and WOX5 regulatory pathways.
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Affiliation(s)
- Alejandra Hernández-Barrera
- Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, 62250, Cuernavaca, Morelos, Mexico
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250
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Suer S, Agusti J, Sanchez P, Schwarz M, Greb T. WOX4 imparts auxin responsiveness to cambium cells in Arabidopsis. THE PLANT CELL 2011; 23:3247-59. [PMID: 21926336 PMCID: PMC3203433 DOI: 10.1105/tpc.111.087874] [Citation(s) in RCA: 182] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 08/04/2011] [Accepted: 09/06/2011] [Indexed: 05/18/2023]
Abstract
Multipotent stem cell populations, the meristems, are fundamental for the indeterminate growth of plant bodies. One of these meristems, the cambium, is responsible for extended root and stem thickening. Strikingly, although the pivotal role of the plant hormone auxin in promoting cambium activity has been known for decades, the molecular basis of auxin responsiveness on the level of cambium cells has so far been elusive. Here, we reveal that auxin-dependent cambium stimulation requires the homeobox transcription factor WOX4. In Arabidopsis thaliana inflorescence stems, 1-N-naphthylphthalamic acid-induced auxin accumulation stimulates cambium activity in the wild type but not in wox4 mutants, although basal cambium activity is not abolished. This conclusion is confirmed by the analysis of cellular markers and genome-wide transcriptional profiling, which revealed only a small overlap between WOX4-dependent and cambium-specific genes. Furthermore, the receptor-like kinase PXY is required for a stable auxin-dependent increase in WOX4 mRNA abundance and the stimulation of cambium activity, suggesting a concerted role of PXY and WOX4 in auxin-dependent cambium stimulation. Thus, in spite of large anatomical differences, our findings uncover parallels between the regulation of lateral and apical plant meristems by demonstrating the requirement for a WOX family member for auxin-dependent regulation of lateral plant growth.
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