151
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Danquah A, de Zelicourt A, Colcombet J, Hirt H. The role of ABA and MAPK signaling pathways in plant abiotic stress responses. Biotechnol Adv 2013; 32:40-52. [PMID: 24091291 DOI: 10.1016/j.biotechadv.2013.09.006] [Citation(s) in RCA: 319] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 09/14/2013] [Accepted: 09/20/2013] [Indexed: 01/12/2023]
Abstract
As sessile organisms, plants have developed specific mechanisms that allow them to rapidly perceive and respond to stresses in the environment. Among the evolutionarily conserved pathways, the ABA (abscisic acid) signaling pathway has been identified as a central regulator of abiotic stress response in plants, triggering major changes in gene expression and adaptive physiological responses. ABA induces protein kinases of the SnRK family to mediate a number of its responses. Recently, MAPK (mitogen activated protein kinase) cascades have also been shown to be implicated in ABA signaling. Therefore, besides discussing the role of ABA in abiotic stress signaling, we will also summarize the evidence for a role of MAPKs in the context of abiotic stress and ABA signaling.
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Affiliation(s)
- Agyemang Danquah
- URGV Plant Genomics, INRA-CNRS-UEVE, Saclay Plant Sciences, 2 rue Gaston Cremieux, 91000 Evry, France
| | - Axel de Zelicourt
- URGV Plant Genomics, INRA-CNRS-UEVE, Saclay Plant Sciences, 2 rue Gaston Cremieux, 91000 Evry, France
| | - Jean Colcombet
- URGV Plant Genomics, INRA-CNRS-UEVE, Saclay Plant Sciences, 2 rue Gaston Cremieux, 91000 Evry, France
| | - Heribert Hirt
- URGV Plant Genomics, INRA-CNRS-UEVE, Saclay Plant Sciences, 2 rue Gaston Cremieux, 91000 Evry, France
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152
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Leljak-Levanić D, Juranić M, Sprunck S. De novo zygotic transcription in wheat (Triticum aestivum L.) includes genes encoding small putative secreted peptides and a protein involved in proteasomal degradation. PLANT REPRODUCTION 2013; 26:267-85. [PMID: 23912470 DOI: 10.1007/s00497-013-0229-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 07/10/2013] [Indexed: 05/12/2023]
Abstract
Wheat is one of the world's most important crops, and increasing grain yield is a major challenge for the future. Still, our knowledge about the molecular machineries responsible for early post-fertilization events such as zygotic reprogramming, the initial cell-specification events during embryogenesis, and the intercellular communication between the early embryo and the developing endosperm is very limited. Here, we describe the identification of de novo transcribed genes in the wheat zygote. We used wheat ovaries of defined post-fertilization stages to isolate zygotes and early embryos, and identified genes that are specifically induced in these particular stages. Importantly, we observed that some of the zygotic-induced genes encode proteins with similarity to secreted signaling peptides such as TAPETUM DETERMINANT 1 and EGG APPARATUS 1, and to MATH-BTB proteins which are known substrate-binding adaptors for the Cullin3-based ubiquitin E3 ligase. This suggests that both cell-cell signaling and targeted proteasomal degradation may be important molecular events during zygote formation and the progression of early embryogenesis.
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Affiliation(s)
- Dunja Leljak-Levanić
- Department of Molecular Biology, Faculty of Science and Mathematics, University of Zagreb, Horvatovac 102a, 10000, Zagreb, Croatia
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153
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Ortiz JPA, Quarin CL, Pessino SC, Acuña C, Martínez EJ, Espinoza F, Hojsgaard DH, Sartor ME, Cáceres ME, Pupilli F. Harnessing apomictic reproduction in grasses: what we have learned from Paspalum. ANNALS OF BOTANY 2013; 112:767-87. [PMID: 23864004 PMCID: PMC3747805 DOI: 10.1093/aob/mct152] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Accepted: 05/13/2013] [Indexed: 05/19/2023]
Abstract
BACKGROUND Apomixis is an alternative route of plant reproduction that produces individuals genetically identical to the mother plant through seeds. Apomixis is desirable in agriculture, because it guarantees the perpetuation of superior genotypes (i.e. heterotic hybrid seeds) by self-seeding without loss of hybrid vigour. The Paspalum genus, an archetypal model system for mining apomixis gene(s), is composed of about 370 species that have extremely diverse reproductive systems, including self-incompatibility, self-fertility, full sexual reproduction, and facultative or obligate apomixis. Barriers to interspecific hybridization are relaxed in this genus, allowing the production of new hybrids from many different parental combinations. Paspalum is also tolerant to various parental genome contributions to the endosperm, allowing analyses of how sexually reproducing crop species might escape from dosage effects in the endosperm. SCOPE In this article, the available literature characterizing apomixis in Paspalum spp. and its use in breeding is critically reviewed. In particular, a comparison is made across species of the structure and function of the genomic region controlling apomixis in order to identify a common core region shared by all apomictic Paspalum species and where apomixis genes are likely to be localized. Candidate genes are discussed, either as possible genetic determinants (including homologs to signal transduction and RNA methylation genes) or as downstream factors (such as cell-to-cell signalling and auxin response genes) depending, respectively, on their co-segregation with apomixis or less. Strategies to validate the role of candidate genes in apomictic process are also discussed, with special emphasis on plant transformation in natural apomictic species.
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Affiliation(s)
- Juan Pablo A. Ortiz
- Instituto de Botánica del Nordeste (IBONE-CONICET), Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste, Corrientes, Argentina
- Laboratorio de Biología Molecular, Facultad de Ciencias Agrarias, Universidad Nacional de Rosario, Zavalla, Argentina
| | - Camilo L. Quarin
- Instituto de Botánica del Nordeste (IBONE-CONICET), Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste, Corrientes, Argentina
| | - Silvina C. Pessino
- Laboratorio de Biología Molecular, Facultad de Ciencias Agrarias, Universidad Nacional de Rosario, Zavalla, Argentina
| | - Carlos Acuña
- Instituto de Botánica del Nordeste (IBONE-CONICET), Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste, Corrientes, Argentina
| | - Eric J. Martínez
- Instituto de Botánica del Nordeste (IBONE-CONICET), Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste, Corrientes, Argentina
| | - Francisco Espinoza
- Instituto de Botánica del Nordeste (IBONE-CONICET), Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste, Corrientes, Argentina
| | - Diego H. Hojsgaard
- Albrecht-von-Haller Institute for Plant Sciences, Department of Systematic Botany, Georg-August-University of Göttingen, Göttingen, Germany
| | - Maria E. Sartor
- Instituto de Botánica del Nordeste (IBONE-CONICET), Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste, Corrientes, Argentina
| | - Maria E. Cáceres
- CNR-Istituto di Genetica Vegetale, Research Division: Perugia, Via della Madonna alta 130, I-06128 Perugia, Italy
| | - Fulvio Pupilli
- CNR-Istituto di Genetica Vegetale, Research Division: Perugia, Via della Madonna alta 130, I-06128 Perugia, Italy
- For correspondence. E-mail
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154
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Martínez-Navarro AC, Galván-Gordillo SV, Xoconostle-Cázares B, Ruiz-Medrano R. Vascular gene expression: a hypothesis. FRONTIERS IN PLANT SCIENCE 2013; 4:261. [PMID: 23882276 PMCID: PMC3713349 DOI: 10.3389/fpls.2013.00261] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 06/26/2013] [Indexed: 05/05/2023]
Abstract
The phloem is the conduit through which photoassimilates are distributed from autotrophic to heterotrophic tissues and is involved in the distribution of signaling molecules that coordinate plant growth and responses to the environment. Phloem function depends on the coordinate expression of a large array of genes. We have previously identified conserved motifs in upstream regions of the Arabidopsis genes, encoding the homologs of pumpkin phloem sap mRNAs, displaying expression in vascular tissues. This tissue-specific expression in Arabidopsis is predicted by the overrepresentation of GA/CT-rich motifs in gene promoters. In this work we have searched for common motifs in upstream regions of the homologous genes from plants considered to possess a "primitive" vascular tissue (a lycophyte), as well as from others that lack a true vascular tissue (a bryophyte), and finally from chlorophytes. Both lycophyte and bryophyte display motifs similar to those found in Arabidopsis with a significantly low E-value, while the chlorophytes showed either a different conserved motif or no conserved motif at all. These results suggest that these same genes are expressed coordinately in non-vascular plants; this coordinate expression may have been one of the prerequisites for the development of conducting tissues in plants. We have also analyzed the phylogeny of conserved proteins that may be involved in phloem function and development. The presence of CmPP16, APL, FT, and YDA in chlorophytes suggests the recruitment of ancient regulatory networks for the development of the vascular tissue during evolution while OPS is a novel protein specific to vascular plants.
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155
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Wendrich JR, Weijers D. The Arabidopsis embryo as a miniature morphogenesis model. THE NEW PHYTOLOGIST 2013; 199:14-25. [PMID: 23590679 DOI: 10.1111/nph.12267] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 03/12/2013] [Indexed: 05/06/2023]
Abstract
Four basic ingredients of morphogenesis, oriented cell division and expansion, cell-cell communication and cell fate specification allow plant cells to develop into a wide variety of organismal architectures. A central question in plant biology is how these cellular processes are regulated and orchestrated. Here, we present the advantages of the early Arabidopsis embryo as a model for studying the control of morphogenesis. All ingredients of morphogenesis converge during embryogenesis, and the highly predictable nature of embryo development offers unprecedented opportunities for understanding their regulation in time and space. In this review we describe the morphogenetic principles underlying embryo patterning and discuss recent advances in their regulation. Morphogenesis is under tight transcriptional control and most genes that were identified as important regulators of embryo patterning encode transcription factors or components of signaling pathways. There exists, therefore, a large gap between the transcriptional control of embryo morphogenesis and the cellular execution. We describe the first such connections, and propose future directions that should help bridge this gap and generate comprehensive understanding of the control of morphogenesis.
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Affiliation(s)
- Jos R Wendrich
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703HA, Wageningen, the Netherlands
| | - Dolf Weijers
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703HA, Wageningen, the Netherlands
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156
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Esteve-Bruna D, Pérez-Pérez JM, Ponce MR, Micol JL. incurvata13, a novel allele of AUXIN RESISTANT6, reveals a specific role for auxin and the SCF complex in Arabidopsis embryogenesis, vascular specification, and leaf flatness. PLANT PHYSIOLOGY 2013; 161:1303-20. [PMID: 23319550 PMCID: PMC3585598 DOI: 10.1104/pp.112.207779] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Auxin plays a pivotal role in plant development by modulating the activity of SCF ubiquitin ligase complexes. Here, we positionally cloned Arabidopsis (Arabidopsis thaliana) incurvata13 (icu13), a mutation that causes leaf hyponasty and reduces leaf venation pattern complexity and auxin responsiveness. We found that icu13 is a novel recessive allele of AUXIN RESISTANT6 (AXR6), which encodes CULLIN1, an invariable component of the SCF complex. Consistent with a role for auxin in vascular specification, the vascular defects in the icu13 mutant were accompanied by reduced expression of auxin transport and auxin perception markers in provascular cells. This observation is consistent with the expression pattern of AXR6, which we found to be restricted to vascular precursors and hydathodes in wild-type leaf primordia. AXR1, RELATED TO UBIQUITIN1-CONJUGATING ENZYME1, CONSTITUTIVE PHOTOMORPHOGENIC9 SIGNALOSOME5A, and CULLIN-ASSOCIATED NEDD8-DISSOCIATED1 participate in the covalent modification of CULLIN1 by RELATED TO UBIQUITIN. Hypomorphic alleles of these genes also display simple venation patterns, and their double mutant combinations with icu13 exhibited a synergistic, rootless phenotype reminiscent of that caused by loss of function of MONOPTEROS (MP), which forms an auxin-signaling module with BODENLOS (BDL). The phenotypes of double mutant combinations of icu13 with either a gain-of-function allele of BDL or a loss-of-function allele of MP were synergistic. In addition, a BDL:green fluorescent protein fusion protein accumulated in icu13, and BDL loss of function or MP overexpression suppressed the phenotype of icu13. Our results demonstrate that the MP-BDL module is required not only for root specification in embryogenesis and vascular postembryonic development but also for leaf flatness.
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157
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Li S, He Y, Zhao J, Zhang L, Sun MX. Polar protein transport between apical and basal cells during tobacco early embryogenesis. PLANT CELL REPORTS 2013; 32:285-91. [PMID: 23124803 DOI: 10.1007/s00299-012-1362-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 09/25/2012] [Accepted: 10/21/2012] [Indexed: 06/01/2023]
Abstract
KEY MESSAGE : We found that protein trafficking between apical and basal cell can be unidirectional, which reveals the different roles of the two cells in the cell-to-cell communication between them during early embryogenesis. In most angiosperm species, asymmetric zygote division results in an apical cell and a basal cell that have distinct cell fates. Much has been speculated about possible communication between these cell types in relation to their cell fate determination. Here, we report on the use of photoactivatable green fluorescent protein (PA-GFP) in tobacco to trace intercellular communication between apical and basal cells during early embryogenesis. We found that PA-GFP was transported between apical and basal cells of a two-celled proembryo, and that protein trafficking was unidirectional toward the apical cell, highlighting different cell communication roles. Further ultrastructural analysis showed numerous plasmodesmata in the walls connecting the apical and basal cells, which may provide channels for protein trafficking. Our data show a possible unique method of cell-to-cell communication between apical and basal cells during early embryogenesis.
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Affiliation(s)
- Shisheng Li
- State Key Laboratory of Hybrid Rice, College of Life Science, Wuhan University, Wuhan 430072, China
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158
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Khan M, Rozhon W, Bigeard J, Pflieger D, Husar S, Pitzschke A, Teige M, Jonak C, Hirt H, Poppenberger B. Brassinosteroid-regulated GSK3/Shaggy-like kinases phosphorylate mitogen-activated protein (MAP) kinase kinases, which control stomata development in Arabidopsis thaliana. J Biol Chem 2013; 288:7519-7527. [PMID: 23341468 DOI: 10.1074/jbc.m112.384453] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Brassinosteroids (BRs) are steroid hormones that coordinate fundamental developmental programs in plants. In this study we show that in addition to the well established roles of BRs in regulating cell elongation and cell division events, BRs also govern cell fate decisions during stomata development in Arabidopsis thaliana. In wild-type A. thaliana, stomatal distribution follows the one-cell spacing rule; that is, adjacent stomata are spaced by at least one intervening pavement cell. This rule is interrupted in BR-deficient and BR signaling-deficient A. thaliana mutants, resulting in clustered stomata. We demonstrate that BIN2 and its homologues, GSK3/Shaggy-like kinases involved in BR signaling, can phosphorylate the MAPK kinases MKK4 and MKK5, which are members of the MAPK module YODA-MKK4/5-MPK3/6 that controls stomata development and patterning. BIN2 phosphorylates a GSK3/Shaggy-like kinase recognition motif in MKK4, which reduces MKK4 activity against its substrate MPK6 in vitro. In vivo we show that MKK4 and MKK5 act downstream of BR signaling because their overexpression rescued stomata patterning defects in BR-deficient plants. A model is proposed in which GSK3-mediated phosphorylation of MKK4 and MKK5 enables for a dynamic integration of endogenous or environmental cues signaled by BRs into cell fate decisions governed by the YODA-MKK4/5-MPK3/6 module.
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Affiliation(s)
- Mamoona Khan
- Institute Biotechnology of Horticultural Crops, Center for Life and Food Sciences Weihenstephan, Technische Universität München, D-85354 Freising, Germany; Max F. Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria
| | - Wilfried Rozhon
- Institute Biotechnology of Horticultural Crops, Center for Life and Food Sciences Weihenstephan, Technische Universität München, D-85354 Freising, Germany; Max F. Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria
| | - Jean Bigeard
- Unité de Recherche en Génomique Végétale Plant Genomics 2, rue Gaston Cremieux, 91057 Evry, France
| | - Delphine Pflieger
- Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement, CNRS, University of Evry, Boulevard François Mitterrand, 91025 Evry, France
| | - Sigrid Husar
- Max F. Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria
| | - Andrea Pitzschke
- Department for Applied Genetics and Cell Biology, University of Natural Resources and Applied Life Sciences, A-1190 Vienna, Austria
| | - Markus Teige
- Department of Molecular Systems Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
| | - Claudia Jonak
- Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, A-1030 Vienna, Austria
| | - Heribert Hirt
- Unité de Recherche en Génomique Végétale Plant Genomics 2, rue Gaston Cremieux, 91057 Evry, France; College of Science, King Saud University, P. O. Box 2455, Riyadh 11451, Saudi Arabia
| | - Brigitte Poppenberger
- Institute Biotechnology of Horticultural Crops, Center for Life and Food Sciences Weihenstephan, Technische Universität München, D-85354 Freising, Germany; Max F. Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria.
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159
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Pillitteri LJ, Dong J. Stomatal development in Arabidopsis. THE ARABIDOPSIS BOOK 2013; 11:e0162. [PMID: 23864836 PMCID: PMC3711358 DOI: 10.1199/tab.0162] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Stomata consist of two guard cells that function as turgor-operated valves that regulate gas exchange in plants. In Arabidopsis, a dedicated cell lineage is initiated and undergoes a series of cell divisions and cell-state transitions to produce a stoma. A set of basic helix-loop-helix (bHLH) transcription factors regulates the transition and differentiation events through the lineage, while the placement of stomata relative to each other is controlled by intercellular signaling via peptide ligands, transmembrane receptors, and mitogen-activated protein kinase (MAPK) modules. Some genes involved in regulating stomatal differentiation or density are also involved in hormonal and environmental stress responses, which may provide a link between modulation of stomatal development or function in response to changes in the environment. Premitotic polarlylocalized proteins provide an added layer of regulation, which can be addressed more thoroughly with the identification of additional proteins in this pathway. Linking the networks that control stomatal development promises to bring advances to our understanding of signal transduction, cell polarity, and cell-fate specification in plants.
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Affiliation(s)
- Lynn Jo Pillitteri
- Department of Biology, Western Washington University, Bellingham, WA, 98225, USA
- Address correspondence to
| | - Juan Dong
- Waksman Institute of Microbiology, Rutgers University, Piscataway, NJ, 08854, USA
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160
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Zhang X, Zhou Y, Ding L, Wu Z, Liu R, Meyerowitz EM. Transcription repressor HANABA TARANU controls flower development by integrating the actions of multiple hormones, floral organ specification genes, and GATA3 family genes in Arabidopsis. THE PLANT CELL 2013; 25:83-101. [PMID: 23335616 PMCID: PMC3584552 DOI: 10.1105/tpc.112.107854] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Revised: 11/29/2012] [Accepted: 12/28/2012] [Indexed: 05/19/2023]
Abstract
Plant inflorescence meristems and floral meristems possess specific boundary domains that result in proper floral organ separation and specification. HANABA TARANU (HAN) encodes a boundary-expressed GATA3-type transcription factor that regulates shoot meristem organization and flower development in Arabidopsis thaliana, but the underlying mechanism remains unclear. Through time-course microarray analyses following transient overexpression of HAN, we found that HAN represses hundreds of genes, especially genes involved in hormone responses and floral organ specification. Transient overexpression of HAN also represses the expression of HAN and three other GATA3 family genes, HANL2 (HAN-LIKE 2), GNC (GATA, NITRATE-INDUCIBLE, CARBON-METABOLISM-INVOLVED), and GNL (GNC-LIKE), forming a negative regulatory feedback loop. Genetic analysis indicates that HAN and the three GATA3 family genes coordinately regulate floral development, and their expression patterns are partially overlapping. HAN can homodimerize and heterodimerize with the three proteins encoded by these genes, and HAN directly binds to its own promoter and the GNC promoter in vivo. These findings, along with the fact that constitutive overexpression of HAN produces an even stronger phenotype than the loss-of-function mutation, support the hypothesis that HAN functions as a key repressor that regulates floral development via regulatory networks involving genes in the GATA3 family, along with genes involved in hormone action and floral organ specification.
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Affiliation(s)
- Xiaolan Zhang
- College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, People's Republic of China.
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161
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Meng X, Wang H, He Y, Liu Y, Walker JC, Torii KU, Zhang S. A MAPK cascade downstream of ERECTA receptor-like protein kinase regulates Arabidopsis inflorescence architecture by promoting localized cell proliferation. THE PLANT CELL 2012; 24:4948-60. [PMID: 23263767 PMCID: PMC3556968 DOI: 10.1105/tpc.112.104695] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2012] [Revised: 11/08/2012] [Accepted: 12/06/2012] [Indexed: 05/18/2023]
Abstract
Spatiotemporal-specific cell proliferation and cell differentiation are critical to the formation of normal tissues, organs, and organisms. The highly coordinated cell differentiation and proliferation events illustrate the importance of cell-cell communication during growth and development. In Arabidopsis thaliana, ERECTA (ER), a receptor-like protein kinase, plays important roles in promoting localized cell proliferation, which determines inflorescence architecture, organ shape, and size. However, the downstream signaling components remain unidentified. Here, we report a mitogen-activated protein kinase (MAPK; or MPK) cascade that functions downstream of ER in regulating localized cell proliferation. Similar to an er mutant, loss of function of MPK3/MPK6 or their upstream MAPK kinases (MAPKKs; or MKKs), MKK4/MKK5, resulted in shortened pedicels and clustered inflorescences. Epistasis analysis demonstrated that the gain of function of MKK4 and MKK5 transgenes could rescue the loss-of-function er mutant phenotype at both morphological and cellular levels, suggesting that the MPK3/MPK6 cascade functions downstream of the ER receptor. Furthermore, YODA (YDA), a MAPKK kinase, was shown to be upstream of MKK4/MKK5 and downstream of ER in regulating inflorescence architecture based on both gain- and loss-of-function data. Taken together, these results suggest that the YDA-MKK4/MKK5-MPK3/MPK6 cascade functions downstream of the ER receptor in regulating localized cell proliferation, which further shapes the morphology of plant organs.
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Affiliation(s)
- Xiangzong Meng
- Division of Biochemistry, Interdisciplinary Plant Group, Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211
| | - Huachun Wang
- Division of Biochemistry, Interdisciplinary Plant Group, Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211
| | - Yunxia He
- Division of Biochemistry, Interdisciplinary Plant Group, Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211
| | - Yidong Liu
- Division of Biochemistry, Interdisciplinary Plant Group, Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211
| | - John C. Walker
- Division of Biological Sciences, Interdisciplinary Plant Group, Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211
| | - Keiko U. Torii
- Howard Hughes Medical Institute and Department of Biology, University of Washington, Seattle, Washington 98195
| | - Shuqun Zhang
- Division of Biochemistry, Interdisciplinary Plant Group, Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211
- Address correspondence to
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162
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Ueda M, Laux T. The origin of the plant body axis. CURRENT OPINION IN PLANT BIOLOGY 2012; 15:578-84. [PMID: 22921364 DOI: 10.1016/j.pbi.2012.08.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 08/01/2012] [Accepted: 08/07/2012] [Indexed: 05/11/2023]
Abstract
During embryogenesis, the basic body plan of an organism develops from a unicellular zygote. In most flowering plants, the polar zygote divides asymmetrically, making visible the apical-basal axis in the early embryo. The molecular mechanisms governing how the zygote polarizes and how this polarity is linked to embryo axis formation have been obscure, mainly owing to the difficulties to access the zygote that is deeply embedded in the maternal tissue. In this review, we summarize recent findings identifying key regulators in Arabidopsis and developing novel approaches in various plant species, which altogether set the stage for unraveling embryo axis formation.
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Affiliation(s)
- Minako Ueda
- Laboratory of Plant Growth Regulation, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Takayamacho 8916-5, Ikoma, Nara 630-0192, Japan.
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163
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Solís MT, Rodríguez-Serrano M, Meijón M, Cañal MJ, Cifuentes A, Risueño MC, Testillano PS. DNA methylation dynamics and MET1a-like gene expression changes during stress-induced pollen reprogramming to embryogenesis. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:6431-44. [PMID: 23175669 PMCID: PMC3504494 DOI: 10.1093/jxb/ers298] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Stress-induced plant cell reprogramming involves changes in global genome organization, being the epigenetic modifications key factors in the regulation of genome flexibility. DNA methylation, accomplished by DNA methyltransferases, constitutes a prominent epigenetic modification of the chromatin fibre which is locked in a transcriptionally inactive conformation. Changes in DNA methylation accompany the reorganization of the nuclear architecture during plant cell differentiation and proliferation. After a stress treatment, in vitro-cultured microspores are reprogrammed and change their gametophytic developmental pathway towards embryogenesis, the process constituting a useful system of reprogramming in isolated cells for applied and basic research. Gene expression driven by developmental and stress cues often depends on DNA methylation; however, global DNA methylation and genome-wide expression patterns relationship is still poorly understood. In this work, the dynamics of DNA methylation patterns in relation to nuclear architecture and the expression of BnMET1a-like DNA methyltransferase genes have been analysed during pollen development and pollen reprogramming to embryogenesis in Brassica napus L. by a multidisciplinary approach. Results showed an epigenetic reprogramming after microspore embryogenesis induction which involved a decrease of global DNA methylation and its nuclear redistribution with the change of developmental programme and the activation of cell proliferation, while DNA methylation increases with pollen and embryo differentiation in a cell-type-specific manner. Changes in the presence, abundance, and distribution of BnMET1a-like transcripts highly correlated with variations in DNA methylation. Mature zygotic and pollen embryos presented analogous patterns of DNA methylation and MET1a-like expression, providing new evidence of the similarities between both developmental embryogenic programmes.
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Affiliation(s)
- María-Teresa Solís
- Plant Development and Nuclear Architecture lab. Biological Research Center, CIB-CSIC, Madrid, Spain
| | - María Rodríguez-Serrano
- Plant Development and Nuclear Architecture lab. Biological Research Center, CIB-CSIC, Madrid, Spain
| | | | | | | | - María C. Risueño
- Plant Development and Nuclear Architecture lab. Biological Research Center, CIB-CSIC, Madrid, Spain
| | - Pilar S. Testillano
- Plant Development and Nuclear Architecture lab. Biological Research Center, CIB-CSIC, Madrid, Spain
- * To whom correspondence should be addressed. E-mail:
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164
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Braud C, Zheng W, Xiao W. LONO1 encoding a nucleoporin is required for embryogenesis and seed viability in Arabidopsis. PLANT PHYSIOLOGY 2012; 160:823-36. [PMID: 22898497 PMCID: PMC3461558 DOI: 10.1104/pp.112.202192] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 08/15/2012] [Indexed: 05/28/2023]
Abstract
Early embryogenesis in Arabidopsis (Arabidopsis thaliana) is distinguished by a predictable pattern of cell divisions and is a good system for investigating mechanisms of developmental pattern formation. Here, we identified a gene called LONO1 (LNO1) in Arabidopsis in which mutations can abolish the first asymmetrical cell division of the zygote, alter planes and number of cell divisions in early embryogenesis, and eventually arrest embryo development. LNO1 is highly expressed in anthers of flower buds, stigma papilla of open flowers, and embryo and endosperm during early embryogenesis, which is correlated with its functions in reproductive development. The homozygous lno1-1 seed is not viable. LNO1, a homolog of the nucleoporin NUP214 in human (Homo sapiens) and Nup159 in yeast (Saccharomyces cerevisiae), encodes a nucleoporin protein containing phenylalanine-glycine repeats in Arabidopsis. We demonstrate that LNO1 can functionally complement the defect in the yeast temperature-sensitive nucleoporin mutant nup159. We show that LNO1 specifically interacts with the Arabidopsis DEAD-box helicase/ATPase LOS4 in the yeast two-hybrid assay. Furthermore, mutations in AtGLE1, an Arabidopsis homolog of the yeast Gle1 involved in the same poly(A) mRNA export pathway as Nup159, also result in seed abortion. Our results suggest that LNO1 is a component of the nuclear pore complex required for mature mRNA export from the nucleus to the cytoplasm, which makes LNO1 essential for embryogenesis and seed viability in Arabidopsis.
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Affiliation(s)
| | | | - Wenyan Xiao
- Department of Biology, Saint Louis University, St. Louis, Missouri 63103
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165
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Prem D, Solís MT, Bárány I, Rodríguez-Sanz H, Risueño MC, Testillano PS. A new microspore embryogenesis system under low temperature which mimics zygotic embryogenesis initials, expresses auxin and efficiently regenerates doubled-haploid plants in Brassica napus. BMC PLANT BIOLOGY 2012; 12:127. [PMID: 22857779 PMCID: PMC3464609 DOI: 10.1186/1471-2229-12-127] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Accepted: 07/10/2012] [Indexed: 05/18/2023]
Abstract
BACKGROUND Microspore embryogenesis represents a unique system of single cell reprogramming in plants wherein a highly specialized cell, the microspore, by specific stress treatment, switches its fate towards an embryogenesis pathway. In Brassica napus, a model species for this phenomenon, incubation of isolated microspores at 32°C is considered to be a pre-requisite for embryogenesis induction. RESULTS We have developed a new in vitro system at lower temperature (18°C) to efficiently induce microspore embryogenesis throughout two different developmental pathways: one involving the formation of suspensor-like structures (52.4%) and another producing multicellular embryos without suspensor (13.1%); additionally, a small proportion of non-responsive microspores followed a gametophytic-like development (34.4%) leading to mature pollen. The suspensor-like pathway followed at 18°C involved the establishment of asymmetric identities from the first microspore division and an early polarity leading to different cell fates, suspensor and embryo development, which were formed by cells with different organizations and endogenous auxin distribution, similar to zygotic embryogenesis. In addition, a new strategy for germination of microspore derived embryos was developed for achieving more than 90% conversion of embryos to plantlets, with a predominance of spontaneous doubled haploids plants. CONCLUSION The present work reveals a novel mechanism for efficient microspore embryogenesis induction in B. napus using continuous low temperature treatment. Results indicated that low temperature applied for longer periods favours an embryogenesis pathway whose first division originates asymmetric cell identities, early polarity establishment and the formation of suspensor-like structures, mimicking zygotic embryogenesis. This new in vitro system provides a convenient tool to analyze in situ the mechanisms underlying different developmental pathways during the microspore reprogramming, breaking or not the cellular symmetry, the establishment of polarity and the developmental embryo patterning, which further produce mature embryos and plants.
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Affiliation(s)
- Deepak Prem
- Plant Development and Nuclear Architecture, Centro de Investigaciones Biológicas, CIB-CSIC, Ramiro de Maeztu 9, 28040, Madrid, Spain
| | - María-Teresa Solís
- Plant Development and Nuclear Architecture, Centro de Investigaciones Biológicas, CIB-CSIC, Ramiro de Maeztu 9, 28040, Madrid, Spain
| | - Ivett Bárány
- Plant Development and Nuclear Architecture, Centro de Investigaciones Biológicas, CIB-CSIC, Ramiro de Maeztu 9, 28040, Madrid, Spain
| | - Héctor Rodríguez-Sanz
- Plant Development and Nuclear Architecture, Centro de Investigaciones Biológicas, CIB-CSIC, Ramiro de Maeztu 9, 28040, Madrid, Spain
| | - María C Risueño
- Plant Development and Nuclear Architecture, Centro de Investigaciones Biológicas, CIB-CSIC, Ramiro de Maeztu 9, 28040, Madrid, Spain
| | - Pilar S Testillano
- Plant Development and Nuclear Architecture, Centro de Investigaciones Biológicas, CIB-CSIC, Ramiro de Maeztu 9, 28040, Madrid, Spain
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166
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Jeong S, Volny M, Lukowitz W. Axis formation in Arabidopsis - transcription factors tell their side of the story. CURRENT OPINION IN PLANT BIOLOGY 2012; 15:4-9. [PMID: 22079785 PMCID: PMC4629246 DOI: 10.1016/j.pbi.2011.10.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2011] [Revised: 10/05/2011] [Accepted: 10/19/2011] [Indexed: 05/06/2023]
Abstract
Apical-to-basal auxin flux is a defining feature of land plants and determines their main body axis. How is the axis first set up in the embryo? Recent studies reveal that the establishment of embryonic polarity with the asymmetric first division as well as the separation of shoot and root fates within the proembryo depend on transcriptional regulation in the zygote and early embryo. Although the functional connections need to be better defined, this transcriptional network likely provides the positional information required for initiating the machinery capable of processing the systemic signal auxin in a context-dependent manner.
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Affiliation(s)
- Sangho Jeong
- Department of Plant Biology, University of Georgia, 120 Carlton Street, Athens, GA 30602-7271, United States.
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167
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Abstract
Development of multicellular organisms requires specification of diverse cell types. In plants, development is continuous and because plant cells are surrounded by rigid cell walls, cell division and specification of daughter cell fate must be carefully orchestrated. During embryonic and postembryonic plant development, the specification of cell types is determined both by positional cues and cell lineage. The establishment of distinct transcriptional domains is a fundamental mechanism for determining different cell fates. In this review, we focus on four examples from recent literature of switches operating in cell fate decisions that are regulated by transcriptional mechanisms. First, we highlight a transcriptional mechanism involving a mobile transcription factor in formation of the two ground tissue cell types in roots. Specification of vascular cell types is then discussed, including new details about xylem cell-type specification via a mobile microRNA. Next, transcriptional regulation of two key embryonic developmental events is considered: establishment of apical-basal polarity in the single-celled zygote and specification of distinct root and shoot stem cell populations in the plant embryo. Finally, a dynamic transcriptional mechanism for lateral organ positioning that integrates spatial and temporal information into a repeating pattern is summarized.
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168
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Lau S, Slane D, Herud O, Kong J, Jürgens G. Early embryogenesis in flowering plants: setting up the basic body pattern. ANNUAL REVIEW OF PLANT BIOLOGY 2012; 63:483-506. [PMID: 22224452 DOI: 10.1146/annurev-arplant-042811-105507] [Citation(s) in RCA: 127] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Early embryogenesis is the critical developmental phase during which the basic features of the plant body are established: the apical-basal axis of polarity, different tissue layers, and both the root pole and the shoot pole. Polarization of the zygote correlates with the generation of apical and basal (embryonic and extraembryonic) cell fates. Whereas mechanisms of zygote polarization are still largely unknown, distinct expression domains of WOX family transcription factors as well as directional auxin transport and local auxin response are known to be involved in early apical-basal patterning. Radial patterning of tissue layers appears to be mediated by cell-cell communication involving both peptide signaling and transcription factor movement. Although the initiation of the shoot pole is still unclear, the apical organization of the embryo depends on both the proper establishment of transcription factor expression domains and, for cotyledon initiation, upward auxin flow in the protoderm. Here we focus on the essential patterning processes, drawing mainly on data from Arabidopsis thaliana and also including relevant data from other species if available.
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Affiliation(s)
- Steffen Lau
- Department of Cell Biology, Max Planck Institute for Developmental Biology, Tübingen, Germany
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169
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Rademacher E, Lokerse A, Schlereth A, Llavata-Peris C, Bayer M, Kientz M, Freire Rios A, Borst J, Lukowitz W, Jürgens G, Weijers D. Different Auxin Response Machineries Control Distinct Cell Fates in the Early Plant Embryo. Dev Cell 2012; 22:211-22. [DOI: 10.1016/j.devcel.2011.10.026] [Citation(s) in RCA: 123] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Revised: 08/10/2011] [Accepted: 10/26/2011] [Indexed: 10/14/2022]
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170
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Abstract
The main route for CO(2) and water vapor exchange between a plant and the environment is through small pores called stomata. The accessibility of stomata and predictable division series that characterize their development provides an excellent system to address fundamental questions in biology. Stomatal cell-state transition and specification are regulated by a suite of transcription factors controlled by positional signaling via peptide ligands and transmembrane receptors. Downstream effectors include several members of the core cell-cycle genes. Environmentally induced signals are integrated into this essential developmental program to modulate stomatal development or function in response to changes in the abiotic environment. In addition, the recent identification of premitotic polarly localized proteins from both Arabidopsis and maize has laid a foundation for the future understanding of intrinsic cell polarity in plants. This review highlights the mechanisms of stomatal development through characterization of genes controlling cell-fate specification, cell polarity, cell division, and cell-cell communication during stomatal development and discusses the genetic framework linking these molecular processes with the correct spacing, density, and differentiation of stomata.
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Affiliation(s)
- Lynn Jo Pillitteri
- Department of Biology, Western Washington University, Bellingham, WA 98225, USA.
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171
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Šamajová O, Plíhal O, Al-Yousif M, Hirt H, Šamaj J. Improvement of stress tolerance in plants by genetic manipulation of mitogen-activated protein kinases. Biotechnol Adv 2011; 31:118-28. [PMID: 22198202 DOI: 10.1016/j.biotechadv.2011.12.002] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Accepted: 12/06/2011] [Indexed: 12/28/2022]
Abstract
Plant stress tolerance depends on many factors among which signaling by mitogen-activated protein-kinase (MAPK) modules plays a crucial role. Reversible phosphorylation of MAPKs, their upstream activators and downstream targets such as transcription factors can trigger a myriad of transcriptomic, cellular and physiological responses. Genetic manipulation of abundance and/or activity of some of these modular MAPK components can lead to better stress tolerance in Arabidopsis and crop plant species such as tobacco and cereals. The main focus of this review is devoted to the MAPK-related signaling components which show the most promising biotechnological potential. Additionally, recent studies identified MAPK components to be involved both in plant development as well as in stress responses, suggesting that these processes are tightly linked in plants.
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Affiliation(s)
- Olga Šamajová
- Centre of the Region Haná for Biotechnological and Agricultural Research, Department of Cell Biology, Faculty of Science, Palacký University Olomouc, Šlechtitelů 11, 78371 Olomouc, Czech Republic
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172
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Hu TX, Yu M, Zhao J. Comparative transcriptional analysis reveals differential gene expression between asymmetric and symmetric zygotic divisions in tobacco. PLoS One 2011; 6:e27120. [PMID: 22069495 PMCID: PMC3206072 DOI: 10.1371/journal.pone.0027120] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Accepted: 10/11/2011] [Indexed: 11/24/2022] Open
Abstract
Asymmetric cell divisions occur widely during many developmental processes in plants. In most angiosperms, the first zygotic cell division is asymmetric resulting in two daughter cells of unequal size and with distinct fates. However, the critical molecular mechanisms regulating this division remain unknown. Previously we showed that treatment of tobacco zygotes with beta-glucosyl Yariv (βGlcY) could dramatically alter the first zygotic asymmetric division to produce symmetric two-celled proembryos. In the present study, we isolated zygotes and two-celled asymmetric proembryos in vivo by micromanipulation, and obtained symmetric, two-celled proembryos by in vitro cell cultures. Using suppression-subtractive hybridization (SSH) and macroarray analysis differential gene expression between the zygote and the asymmetric and symmetric two-celled proembryos was investigated. After sequencing of the differentially expressed clones, a total of 1610 EST clones representing 685 non-redundant transcripts were obtained. Gene ontology (GO) term analysis revealed that these transcripts include those involved in physiological processes such as response to stimulus, regulation of gene expression, and localization and formation of anatomical structures. A homology search against known genes from Arabidopsis indicated that some of the above transcripts are involved in asymmetric cell division and embryogenesis. Quantitative real-time PCR confirmed the up- or down-regulation of the selected candidate transcripts during zygotic division. A few of these transcripts were expressed exclusively in the zygote, or in either type of the two-celled proembryos. Expression analyses of select genes in different tissues and organs also revealed potential roles of these transcripts in fertilization, seed maturation and organ development. The putative roles of few of the identified transcripts in the regulation of zygotic division are discussed. Further functional work on these candidate transcripts will provide important information for understanding asymmetric zygotic division, generation of apical-basal polarity and cell fate decisions during early embryogenesis.
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Affiliation(s)
- Tian-Xiang Hu
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Miao Yu
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Jie Zhao
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
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173
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Chevalier É, Loubert-Hudon A, Zimmerman EL, Matton DP. Cell-cell communication and signalling pathways within the ovule: from its inception to fertilization. THE NEW PHYTOLOGIST 2011; 192:13-28. [PMID: 21793830 DOI: 10.1111/j.1469-8137.2011.03836.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Cell-cell communication pervades every aspect of the life of a plant. It is particularly crucial for the development of the gametes and their subtle interaction leading to double fertilization. The ovule is composed of a funiculus, one or two integuments, and a gametophyte surrounded by nucellus tissue. Proper ovule and embryo sac development are critical to reproductive success. To allow fertilization, the correct relative positioning and differentiation of the embryo sac cells are essential. Integument development is also intimately linked with the normal development of the female gametophyte; the sporophyte and gametophyte are not fully independent tissues. Inside the gametophyte, numerous signs of cell-cell communication take place throughout development, including cell fate patterning, fertilization and the early stages of embryogenesis. This review highlights the current evidence of cell-cell communication and signalling elements based on structural and physiological observations as well as the description and characterization of mutants in structurally specific genes. By combining data from different species, models of cell-cell interactions have been built, particularly for the establishment of the germline, for the progression through megagametogenesis and for double fertilization.
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Affiliation(s)
- Éric Chevalier
- Institut de Recherche en Biologie Végétale, Département de Sciences Biologiques, Université de Montréal, 4101 rue Sherbrooke est, Montréal, QC, Canada H1X 2B2
| | - Audrey Loubert-Hudon
- Institut de Recherche en Biologie Végétale, Département de Sciences Biologiques, Université de Montréal, 4101 rue Sherbrooke est, Montréal, QC, Canada H1X 2B2
| | - Erin L Zimmerman
- Institut de Recherche en Biologie Végétale, Département de Sciences Biologiques, Université de Montréal, 4101 rue Sherbrooke est, Montréal, QC, Canada H1X 2B2
| | - Daniel P Matton
- Institut de Recherche en Biologie Végétale, Département de Sciences Biologiques, Université de Montréal, 4101 rue Sherbrooke est, Montréal, QC, Canada H1X 2B2
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174
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Heinrich M, Baldwin IT, Wu J. Two mitogen-activated protein kinase kinases, MKK1 and MEK2, are involved in wounding- and specialist lepidopteran herbivore Manduca sexta-induced responses in Nicotiana attenuata. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:4355-65. [PMID: 21610019 PMCID: PMC3153688 DOI: 10.1093/jxb/err162] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2010] [Revised: 04/14/2011] [Accepted: 04/25/2011] [Indexed: 05/18/2023]
Abstract
In a wild tobacco plant, Nicotiana attenuata, two mitogen-activated protein kinases (MAPKs), salicylic acid-induced protein kinase (SIPK) and wound-induced protein kinase (WIPK), play central roles in modulating herbivory-induced phytohormone and anti-herbivore secondary metabolites. However, the identities of their upstream MAPK kinases (MAPKKs) were elusive. Ectopic overexpression studies in N. benthamiana and N. tabacum suggested that two MAPKKs, MKK1 and MEK2, may activate SIPK and WIPK. The homologues of MKK1 and MEK2 were cloned in N. attenuata (NaMKK1 and NaMEK2) and a virus-induced gene silencing approach was used to knock-down the transcript levels of these MAPKK genes. Plants silenced in NaMKK1 and NaMEK2 were treated with wounding or simulated herbivory by applying the oral secretions of the specialist herbivore Manduca sexta to wounds. MAPK activity assay indicated that after wounding or simulated herbivory NaMKK1 is not required for the phosphorylation of NaSIPK and NaWIPK; in contrast, NaMEK2 and other unknown MAPKKs are important for simulated herbivory-elicited activation of NaSIPK and NaWIPK, and after wounding NaMEK2 probably does not activate NaWIPK but plays a minor role in activating NaSIPK. Consistently, NaMEK2 and certain other MAPKKs, but not NaMKK1, are needed for wounding- and simulated herbivory-elicited accumulation of jasmonic acid (JA), JA-isoleucine, and ethylene. Furthermore, both NaMEK2 and NaMKK1 regulate the levels of trypsin proteinase inhibitors. The findings underscore the complexity of MAPK signalling pathways and highlight the importance of MAPKKs in regulating wounding- and herbivory-induced responses.
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Affiliation(s)
| | | | - Jianqiang Wu
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Hans-Knöll Str. 8, D-07745 Jena, Germany
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175
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Waki T, Hiki T, Watanabe R, Hashimoto T, Nakajima K. The Arabidopsis RWP-RK protein RKD4 triggers gene expression and pattern formation in early embryogenesis. Curr Biol 2011; 21:1277-81. [PMID: 21802301 DOI: 10.1016/j.cub.2011.07.001] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Revised: 06/02/2011] [Accepted: 06/30/2011] [Indexed: 11/19/2022]
Abstract
Morphogenesis of seed plants commences with highly stereotypical cell division sequences in early embryogenesis [1, 2]. Although a small number of transcription factors and a mitogen-activated protein (MAP) kinase cascade have been implicated in this process [3-8], pattern formation in early embryogenesis remains poorly understood. We show here that the Arabidopsis RKD4, a member of the RWP-RK motif-containing putative transcription factors [9], is required for this process. Loss-of-function rkd4 mutants were defective in zygotic cell elongation, as well as subsequent cell division patterns. As expected from this mutant phenotype, RKD4 was transcribed preferentially in early embryos. RKD4 possessed functional characteristics of transcription factors and was able to ectopically induce early embryo-specific genes when overexpressed in seedlings. Strikingly, induced overexpression of RKD4 primed somatic cells for embryogenesis independently of external growth regulators. These results reveal that RKD4 is a novel key regulator of the earliest stage of plant development.
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Affiliation(s)
- Takamitsu Waki
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan
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176
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Jeong S, Palmer TM, Lukowitz W. The RWP-RK factor GROUNDED promotes embryonic polarity by facilitating YODA MAP kinase signaling. Curr Biol 2011; 21:1268-76. [PMID: 21802295 DOI: 10.1016/j.cub.2011.06.049] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Revised: 06/02/2011] [Accepted: 06/17/2011] [Indexed: 01/11/2023]
Abstract
BACKGROUND The division of plant zygotes is typically asymmetric, generating daughter cells with different developmental fates. In Arabidopsis, the apical daughter cell produces the proembryo, whereas the basal daughter cell forms the mostly extraembryonic suspensor. Establishment of apical and basal fates is known to depend on the YODA (YDA) mitogen-associated protein (MAP) kinase cascade and WUSCHEL-LIKE HOMEOBOX (WOX) homeodomain transcription factors. RESULTS Mutations in GROUNDED (GRD) cause anatomical defects implying a partial loss of developmental asymmetry in the first division. Subsequently, suspensor-specific WOX8 expression disappears while proembryo-specific ZLL expression expands in the mutants, revealing that basal fates are confounded. GRD encodes a small nuclear protein of the RWP-RK family and is broadly transcribed in the early embryo. Loss of GRD eliminates the dominant effects of hyperactive YDA variants, indicating that GRD is required for YDA-dependent signaling in the embryo. However, GRD function is not regulated via direct phosphorylation by MAP kinases, and forced expression of GRD does not suppress the effect of yda mutations. In a strong synthetic interaction, grd;wox8;wox9 triple mutants arrest as zygotes or one-cell embryos lacking apparent polarity. CONCLUSIONS The predicted transcription factor GRD acts cooperatively with WOX homeodomain proteins to establish embryonic polarity in the first division. Like YDA, GRD promotes zygote elongation and basal cell fates. GRD function is required for YDA-dependent signaling but apparently not regulated by the YDA MAP kinase cascade. Similarity of GRD to Chlamydomonas MID suggests a conserved role for small RWP-RK proteins in regulating the transcriptional programs of generative cells and the zygote.
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Affiliation(s)
- Sangho Jeong
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
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177
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Kim SH, Woo DH, Kim JM, Lee SY, Chung WS, Moon YH. Arabidopsis MKK4 mediates osmotic-stress response via its regulation of MPK3 activity. Biochem Biophys Res Commun 2011; 412:150-4. [PMID: 21806969 DOI: 10.1016/j.bbrc.2011.07.064] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2011] [Accepted: 07/17/2011] [Indexed: 12/19/2022]
Abstract
Plants have developed disparate regulatory pathways to adapt to environmental stresses. In this study, we identified MKK4 as an important mediator of plant response to osmotic stress. mkk4 mutants were more sensitive to high salt concentration than WT plants, exhibiting higher water-loss rates under dehydration conditions and additionally accumulating high levels of ROS. In contrast, MKK4-overexpressing transgenic plants showed tolerance to high salt as well as lower water-loss rates under dehydration conditions. In-gel kinase assays revealed that MKK4 regulates the activity of MPK3 upon NaCl exposure. Semi-quantitative RT-PCR analysis showed that expression of NCED3 and RD29A was lower and higher in mkk4 mutants and MKK4-overexpressing transgenic plants, respectively. Taken together, our results suggest that MKK4 is involved in the osmotic-stress response via its regulation of MPK3 activity.
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Affiliation(s)
- Sun-Ho Kim
- Department of Molecular Biology, Pusan National University, Busan 609-735, Republic of Korea
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178
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Malcos JL, Cyr RJ. An ungrouped plant kinesin accumulates at the preprophase band in a cell cycle-dependent manner. Cytoskeleton (Hoboken) 2011; 68:247-58. [PMID: 21387573 DOI: 10.1002/cm.20508] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Past phylogenic studies have identified a plant-specific, ungrouped family of kinesins in which the motor domain does not group to one of the fourteen recognized families. Members of this family contain an N-terminal motor domain, a C-terminal armadillo repeat domain and a conserved destruction box (D-BOX) motif. This domain architecture is unique to plants and to a subset of protists. Further characterization of one representative member from Arabidopsis, Arabidopsis thaliana KINESIN ungrouped clade, gene A (AtKINUa), was completed to ascertain its functional role in plants. Fluorescence confocal microscopy revealed an accumulation of ATKINUA:GFP at the preprophase band (PPB) in a cell cycle-dependent manner in Arabidopsis epidermal cells and tobacco BY-2 cells. Fluorescence accumulation was highest during prophase and decreased after nuclear envelope breakdown. A conserved D-BOX motif was identified through alignment of AtKINU homologous sequences. Mutagenesis work with D-BOX revealed that conserved residues were necessary for the observed degradation pattern of ATKINUA:GFP, as well as the targeted accumulation at the PPB. Overall results suggest that AtKINUa is necessary for normal plant growth and/or development and is likely involved with PPB organization through microtubule association and specific cell cycle regulation. The D-BOX motif may function to bridge microtubule organization with changes that occur during progression through mitosis and may represent a novel regulatory motif in plant microtubule motor proteins.
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Affiliation(s)
- Jennelle L Malcos
- Department of Biology, The Pennsylvania State University, 208 Mueller Laboratory, University Park, Pennsylvania, USA
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179
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Ueda M, Zhang Z, Laux T. Transcriptional activation of Arabidopsis axis patterning genes WOX8/9 links zygote polarity to embryo development. Dev Cell 2011; 20:264-70. [PMID: 21316593 DOI: 10.1016/j.devcel.2011.01.009] [Citation(s) in RCA: 184] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Revised: 01/05/2011] [Accepted: 01/24/2011] [Indexed: 11/26/2022]
Abstract
In most flowering plants, the apical-basal body axis is established by an asymmetric division of the polarized zygote. In Arabidopsis, early embryo patterning is regulated by WOX homeobox genes, which are coexpressed in the zygote but become restricted to apical (WOX2) and basal (WOX8/9) cells. How the asymmetry of zygote division is regulated and connected to the daughter cell fates is largely unknown. Here, we show that expression of WOX8 is independent of the axis patterning signal auxin, but, together with the redundant gene WOX9, is activated in the zygote, its basal daughter cell, and the hypophysis by the zinc-finger transcription factor WRKY2. In wrky2 mutants, egg cells polarize normally but zygotes fail to reestablish polar organelle positioning from a transient symmetric state, resulting in equal cell division and distorted embryo development. Both defects are rescued by overexpressing WOX8, indicating that WRKY2-dependent WOX8 transcription links zygote polarization with embryo patterning.
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Affiliation(s)
- Minako Ueda
- BIOSS Centre for Biological Signalling Studies, Faculty of Biology, Albert-Ludwigs University Freiburg, Freiburg, Germany
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180
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MacAlister CA, Bergmann DC. Sequence and function of basic helix-loop-helix proteins required for stomatal development in Arabidopsis are deeply conserved in land plants. Evol Dev 2011; 13:182-92. [PMID: 21410874 PMCID: PMC3139685 DOI: 10.1111/j.1525-142x.2011.00468.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Stomata are a broadly conserved feature of land plants with a crucial role regulating transpiration and gas exchange between the plant and atmosphere. Stereotyped cell divisions within a specialized cell lineage of the epidermis generate stomata and define the pattern of their distribution. The behavior of the stomatal lineage varies in its detail among different plant groups, but general features include asymmetric cell divisions and an immediate precursor (the guard mother cell [GMC]) that divides symmetrically to form the pair of cells that will differentiate into the guard cells. In Arabidopsis, the closely related basic helix-loop-helix (bHLH) subgroup Ia transcription factors SPEECHLESS, MUTE, and FAMA promote asymmetric divisions, the acquisition of GMC identity and guard cell differentiation, respectively. Genome sequence data indicate that these key positive regulators of stomatal development are broadly conserved among land plants. While orthologies can be established among individual family members within the angiosperms, more distantly related groups contain subgroup Ia bHLHs of unclear affinity. We demonstrate group Ia members from the moss Physcomitrella patens can partially complement MUTE and FAMA and recapitulate gain of function phenotypes of group Ia genes in multiple steps in the stomatal lineage in Arabidopsis. Our data are consistent with a mechanism whereby a multifunctional transcription factor underwent duplication followed by specialization to provide the three (now nonoverlapping) functions of the angiosperm stomatal bHLHs.
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Affiliation(s)
- Cora A MacAlister
- Department of Biology, Stanford University, Stanford, CA 94305-5020, USA.
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181
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Takeda S, Aida M. Establishment of the embryonic shoot apical meristem in Arabidopsis thaliana. JOURNAL OF PLANT RESEARCH 2011; 124:211-219. [PMID: 21104289 DOI: 10.1007/s10265-010-0390-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2010] [Accepted: 10/25/2010] [Indexed: 05/30/2023]
Abstract
In higher plants, shoot organs such as leaves, branches, and flowers are generated from the shoot apical meristem (SAM), a small group of undifferentiated cells located at the tip of the shoot. The SAM maintains its pluripotency and simultaneously produces lateral organs at its periphery. The SAM arises during embryogenesis and its positioning requires axis-dependent embryo patterning and compartmentalization of the embryo apex. Here, we introduce major factors involved in these processes in Arabidopsis thaliana and discuss how the embryonic SAM is established.
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Affiliation(s)
- Seiji Takeda
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 6300192, Japan.
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182
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De Smet I, Beeckman T. Asymmetric cell division in land plants and algae: the driving force for differentiation. Nat Rev Mol Cell Biol 2011; 12:177-88. [PMID: 21346731 DOI: 10.1038/nrm3064] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Asymmetric cell division generates two cells with different fates and has an important role in plant development. It produces distinct cell types and new organs, and maintains stem cell niches. To handle the constraints of having immobile cells, plants possess numerous unique features to obtain asymmetry, such as specific regulators of intrinsic polarity. Although several components have not yet been identified, new findings, together with knowledge from different developmental systems, now allow us to take an important step towards a mechanistic overview of asymmetric cell division in plants and algae. Strikingly, several key regulators are used for different developmental processes, and common mechanisms can be recognized.
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Affiliation(s)
- Ive De Smet
- Plant and Crop Sciences Division, School of Biosciences, University of Nottingham, Loughborough LE12 5RD, UK.
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183
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Jeong S, Bayer M, Lukowitz W. Taking the very first steps: from polarity to axial domains in the early Arabidopsis embryo. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:1687-97. [PMID: 21172809 DOI: 10.1093/jxb/erq398] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Arabidopsis embryos follow a predictable sequence of cell divisions, facilitating a genetic analysis of their early development. Both asymmetric divisions and cell-to-cell communication are probably involved in generating specific gene expression domains along the main axis within the first few division cycles. The function of these domains is not always understood, but recent work suggests that they may serve as a basis for organizing polar auxin flux. Auxin acts as systemic signal throughout the life cycle and, in the embryo, has been demonstrated to direct formation of the main axis and root initiation at the globular stage. At about the same time, root versus shoot fates are imposed on the incipient meristems by the expression of antagonistic regulators at opposite poles of the embryo. Some of the key features of the embryonic patterning process have emerged over the past few years and may provide the elements of a coherent conceptual framework.
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Affiliation(s)
- Sangho Jeong
- Department of Plant Biology, University of Georgia, Athens, GA 30602-7271, USA
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184
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The Arabidopsis peptide kiss of death is an inducer of programmed cell death. EMBO J 2011; 30:1173-83. [PMID: 21326210 DOI: 10.1038/emboj.2011.14] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Accepted: 01/05/2011] [Indexed: 12/20/2022] Open
Abstract
Programmed cell death (PCD) has a key role in defence and development of all multicellular organisms. In plants, there is a large gap in our knowledge of the molecular machinery involved at the various stages of PCD, especially the early steps. Here, we identify kiss of death (KOD) encoding a 25-amino-acid peptide that activates a PCD pathway in Arabidopsis thaliana. Two mutant alleles of KOD exhibited a reduced PCD of the suspensor, a single file of cells that support embryo development, and a reduced PCD of root hairs after a 55°C heat shock. KOD expression was found to be inducible by biotic and abiotic stresses. Furthermore, KOD expression was sufficient to cause death in leaves or seedlings and to activate caspase-like activities. In addition, KOD-induced PCD required light in leaves and was repressed by the PCD-suppressor genes AtBax inhibitor 1 and p35. KOD expression resulted in depolarization of the mitochondrial membrane, placing KOD above mitochondria dysfunction, an early step in plant PCD. A KOD∷GFP fusion, however, localized in the cytosol of cells and not mitochondria.
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185
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Zhao P, Shi DQ, Yang WC. Patterning the embryo in higher plants: Emerging pathways and challenges. ACTA ACUST UNITED AC 2011. [DOI: 10.1007/s11515-011-1119-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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186
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The asymmetric division of the Arabidopsis zygote: from cell polarity to an embryo axis. ACTA ACUST UNITED AC 2011; 24:161-9. [PMID: 21225434 DOI: 10.1007/s00497-010-0160-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Accepted: 12/22/2010] [Indexed: 12/29/2022]
Abstract
During plant embryogenesis, a simple body plan consisting of shoot and root meristem that are connected by the embryo axis is set up by the first few rounds of cell divisions after fertilization. Postembryonically, the elaborate architecture of plants is created from stem cell populations of both meristems. Here, we address how the main axis (apical-basal) of the plant embryo is established from the single-celled zygote and the role that the asymmetric division of the zygote plays in this process. We will mainly draw on examples from the model plant Arabidopsis, for which several key regulators have been identified during the last years.
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187
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Okamoto T. In vitro fertilization with rice gametes: production of zygotes and zygote and embryo culture. Methods Mol Biol 2011; 710:17-27. [PMID: 21207258 DOI: 10.1007/978-1-61737-988-8_2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
In vitro fertilization (IVF) systems using isolated male and female gametes have been utilized to dissect fertilization-induced events in angiosperms, such as egg activation, zygote development, and early embryogenesis, since the female gametophytes of plants are deeply embedded within ovaries. A rice IVF system was established to take advantage of the abundant resources stemming from rice research for investigations into the mechanisms of fertilization and early embryogenesis. Fusion of gametes can be performed using electrofusion and the fusion product, a zygote, forms a cell wall and an additional nucleolus. The zygote divides into an asymmetric two-celled embryo and develops into an early globular embryo, as in planta. The embryo further develops into irregularly shaped cell masses and fertile plants can be regenerated from the cell masses. This rice IVF system is a powerful tool for studying the molecular mechanisms involved in the early embryogenesis of angiosperms and for making new cultivars.
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Affiliation(s)
- Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan.
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188
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Xie Z, Li D, Wang L, Sack FD, Grotewold E. Role of the stomatal development regulators FLP/MYB88 in abiotic stress responses. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 64:731-9. [PMID: 21105921 DOI: 10.1111/j.1365-313x.2010.04364.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Stomata are vital for the adaptation of plants to abiotic stress, and in turn stomatal density is modulated by environmental factors. Less clear, however, is whether regulators of stomatal development themselves participate in the sensing or response of stomata to abiotic stress. FOUR LIPS (FLP) and its paralog MYB88 encode MYB proteins that establish stomatal patterning by permitting only a single symmetric division before stomata differentiate. Hence, flp-1 myb88 double mutants have an excess of stomata, which are often misplaced in direct contact. Here, we investigate the consequences of loss of FLP/MYB88 function on the ability of Arabidopsis plants to respond to abiotic stress. While flp-1 myb88 double mutants are viable and display no obvious aerial phenotypes under normal greenhouse growth conditions, we show that flp-1 myb88 plants are significantly more susceptible to drought and high salt, and have increased rates of water loss. To determine whether flp-1 myb88 plants are already challenged under normal growth conditions, we compared genome-wide transcript levels between flp-1 myb88 and wild-type green tissues. Unexpectedly, uninduced flp-1 myb88 plants showed a reduced accumulation of many typical abiotic stress gene transcripts. Moreover, the induction of many of these stress genes under high-salt conditions was significantly lower in flp-1 myb88 plants. Our results provide evidence for a new function of FLP/MYB88 in sensing and/or transducing abiotic stress, which is severely compromised in flp-1 myb88 mutants.
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Affiliation(s)
- Zidian Xie
- Department of Plant Cellular and Molecular Biology, Ohio State University, Columbus, OH 43210, USA
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189
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Kelliher T, Walbot V. Emergence and patterning of the five cell types of the Zea mays anther locule. Dev Biol 2010; 350:32-49. [PMID: 21070762 DOI: 10.1016/j.ydbio.2010.11.005] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2010] [Revised: 11/02/2010] [Accepted: 11/02/2010] [Indexed: 01/02/2023]
Abstract
One fundamental difference between plants and animals is the existence of a germ-line in animals and its absence in plants. In flowering plants, the sexual organs (stamens and carpels) are composed almost entirely of somatic cells, a small subset of which switch to meiosis; however, the mechanism of meiotic cell fate acquisition is a long-standing botanical mystery. In the maize (Zea mays) anther microsporangium, the somatic tissues consist of four concentric cell layers that surround and support reproductive cells as they progress through meiosis and pollen maturation. Male sterility, defined as the absence of viable pollen, is a common phenotype in flowering plants, and many male sterile mutants have defects in somatic and reproductive cell fate acquisition. However, without a robust model of anther cell fate acquisition based on careful observation of wild-type anther ontogeny, interpretation of cell fate mutants is limited. To address this, the pattern of cell proliferation, expansion, and differentiation was tracked in three dimensions over 30 days of wild-type (W23) anther development, using anthers stained with propidium iodide (PI) and/or 5-ethynyl-2'-deoxyuridine (EdU) (S-phase label) and imaged by confocal microscopy. The pervading lineage model of anther development claims that new cell layers are generated by coordinated, oriented cell divisions in transient precursor cell types. In reconstructing anther cell division patterns, however, we can only confirm this for the origin of the middle layer (ml) and tapetum, while young anther development appears more complex. We find that each anther cell type undergoes a burst of cell division after specification with a characteristic pattern of both cell expansion and division. Comparisons between two inbreds lines and between ab- and adaxial anther florets indicated near identity: anther development is highly canalized and synchronized. Three classical models of plant organ development are tested and ruled out; however, local clustering of developmental events was identified for several processes, including the first evidence for a direct relationship between the development of ml and tapetal cells. We speculate that small groups of ml and tapetum cells function as a developmental unit dedicated to the development of a single pollen grain.
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Affiliation(s)
- Timothy Kelliher
- Stanford University, Department of Biology, 385 Serra Mall, Stanford, CA 94305-5020, USA.
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190
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Okamoto T. Gamete fusion site on the egg cell and autonomous establishment of cell polarity in the zygote. PLANT SIGNALING & BEHAVIOR 2010; 5:1464-7. [PMID: 21051936 PMCID: PMC3115256 DOI: 10.4161/psb.5.11.13468] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Gamete fusion activates the egg in animals and plants, and the gamete fusion site on the zygote might provide a possible cue for zygotic development and/or embryonic patterning. In angiosperms, a zygote generally divides into a two-celled proembryo consisting of an apical and a basal cell with different cell fates. This is a putative step in the formation of the apical-basal axis of the proembryo. We observed the positional relationship between the gamete fusion site and the division plane formed by zygotic cleavage using an in vitro fertilization system with rice gametes. There was no relationship between the gamete fusion site and the division plane leading to the two-celled proembryo. Thus, the gamete fusion site on the rice zygote does not appear to function as a determinant for positioning the zygote division plane, and the zygote apparently possesses autonomous potential to establish cell polarity along the apical-basal axis for its first cleavage.
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Affiliation(s)
- Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan.
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191
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Liu YK, Liu YB, Zhang MY, Li DQ. Stomatal development and movement: the roles of MAPK signaling. PLANT SIGNALING & BEHAVIOR 2010; 5:1176-80. [PMID: 20855958 PMCID: PMC3115344 DOI: 10.4161/psb.5.10.12757] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Stomata are epidermal pores on plant surface used for gas exchange with the atmosphere. Stomatal development and movement are regulated by environmental and internal signals. Mitogen-activated protein kinase (MAPK) cascades are universal transducers of extracellular signals among all eukaryotes. In plant, MAPK cascades regulate diverse cellular processes occurring during the whole ontogenetic plant life and ranging from normal cell proliferation to stress-inducing plant-to-environment interactions. Recent reports reveal that MAPK signaling is involved in both stomatal development and movement. This mini-review summarizes the roles of MAPK signaling in stomatal development and movement. How MAPK specificity is maintained in stomatal development and movement is also discussed.
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Affiliation(s)
- Yu-Kun Liu
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, Shandong, China
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192
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Petricka JJ, Van Norman JM, Benfey PN. Symmetry breaking in plants: molecular mechanisms regulating asymmetric cell divisions in Arabidopsis. Cold Spring Harb Perspect Biol 2010; 1:a000497. [PMID: 20066115 DOI: 10.1101/cshperspect.a000497] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Asymmetric cell division generates cell types with different specialized functions or fates. This type of division is critical to the overall cellular organization and development of many multicellular organisms. In plants, regulated asymmetric cell divisions are of particular importance because cell migration does not occur. The influence of extrinsic cues on asymmetric cell division in plants is well documented. Recently, candidate intrinsic factors have been identified and links between intrinsic and extrinsic components are beginning to be elucidated. A novel mechanism in breaking symmetry was revealed that involves the movement of typically intrinsic factors between plant cells. As we learn more about the regulation of asymmetric cell divisions in plants, we can begin to reflect on the similarities and differences between the strategies used by plants and animals. Focusing on the underlying molecular mechanisms, this article describes three selected cases of symmetry-breaking events in the model plant Arabidopsis thaliana. These examples occur in early embryogenesis, stomatal development, and ground tissue formation in the root.
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Affiliation(s)
- Jalean J Petricka
- Department of Biology and IGSP Center for Systems Biology, Duke University, Durham, North Carolina 27708, USA
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193
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Li HJ, Liu NY, Shi DQ, Liu J, Yang WC. YAO is a nucleolar WD40-repeat protein critical for embryogenesis and gametogenesis in Arabidopsis. BMC PLANT BIOLOGY 2010; 10:169. [PMID: 20699009 PMCID: PMC3095302 DOI: 10.1186/1471-2229-10-169] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2010] [Accepted: 08/11/2010] [Indexed: 05/18/2023]
Abstract
BACKGROUND In flowering plants, gametogenesis generates multicellular male and female gametophytes. In the model system Arabidopsis, the male gametophyte or pollen grain contains two sperm cells and a vegetative cell. The female gametophyte or embryo sac contains seven cells, namely one egg, two synergids, one central cell and three antipodal cells. Double fertilization of the central cell and egg produces respectively a triploid endosperm and a diploid zygote that develops further into an embryo. The genetic control of the early embryo patterning, especially the initiation of the first zygotic division and the positioning of the cell plate, is largely unknown. RESULTS Here we report the characterization of a mutation, yaozhe (yao), that causes zygote arrest and misplacement of cell plate of the zygote, leading to early embryo lethality. In addition, gametophyte development is partially impaired. A small portion of the mutant embryo sacs are arrested at four-nucleate stage with aberrant nuclear positioning. Furthermore, the competence of male gametophytes is also compromised. YAO encodes a nucleolar protein with seven WD-repeats. Its homologues in human and yeast have been shown to be components of the U3 snoRNP complex and function in 18S rRNA processing. YAO is expressed ubiquitously, with high level of expression in tissues under active cell divisions, including embryo sacs, pollen, embryos, endosperms and root tips. CONCLUSIONS Phenotypic analysis indicated that YAO is required for the correct positioning of the first zygotic division plane and plays a critical role in gametogenesis in Arabidopsis. Since YAO is a nucleolar protein and its counterparts in yeast and human are components of the U3 snoRNP complex, we therefore postulate that YAO is most likely involved in rRNA processing in plants as well.
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Affiliation(s)
- Hong-Ju Li
- Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, the Chinese Academy of Sciences, Beijing 100101, China
- Gradute University, the Chinese Academy of Sciences, Beijing 100049, China
| | - Nai-You Liu
- Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, the Chinese Academy of Sciences, Beijing 100101, China
| | - Dong-Qiao Shi
- Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, the Chinese Academy of Sciences, Beijing 100101, China
| | - Jie Liu
- Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, the Chinese Academy of Sciences, Beijing 100101, China
| | - Wei-Cai Yang
- Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, the Chinese Academy of Sciences, Beijing 100101, China
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194
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Hu TX, Yu M, Zhao J. Comparative transcriptional profiling analysis of the two daughter cells from tobacco zygote reveals the transcriptome differences in the apical and basal cells. BMC PLANT BIOLOGY 2010; 10:167. [PMID: 20699003 PMCID: PMC3095300 DOI: 10.1186/1471-2229-10-167] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2010] [Accepted: 08/11/2010] [Indexed: 05/19/2023]
Abstract
BACKGROUND In angiosperm, after the first asymmetric zygotic cell division, the apical and basal daughter cells follow distinct development pathways. Global transcriptome analysis of these two cells is essential in understanding their developmental differences. However, because of the difficulty to isolate the in vivo apical and basal cells of two-celled proembryo from ovule and ovary in higher plants, the transcriptome analysis of them hasn't been reported. RESULTS In this study, we developed a procedure for isolating the in vivo apical and basal cells of the two-celled proembryo from tobacco (Nicotiana tabacum), and then performed a comparative transcriptome analysis of the two cells by suppression subtractive hybridization (SSH) combined with macroarray screening. After sequencing, we identified 797 differentially expressed ESTs corresponding to 299 unigenes. Library sequence analysis successfully identified tobacco homologies of genes involved in embryogenesis and seed development. By quantitative real-time PCR, we validated the differential expression of 40 genes, with 6 transcripts of them specifically expressed in the apical or basal cell. Expression analysis also revealed some transcripts displayed cell specific activation in one of the daughter cells after zygote division. These differential expressions were further validated by in situ hybridization (ISH). Tissue expression pattern analysis also revealed some potential roles of these candidate genes in development. CONCLUSIONS The results show that some differential or specific transcripts in the apical and basal cells of two-celled proembryo were successfully isolated, and the identification of these transcripts reveals that these two daughter cells possess distinct transcriptional profiles after zygote division. Further functional work on these differentially or specifically expressed genes will promote the elucidation of molecular mechanism controlling early embryogenesis.
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Affiliation(s)
- Tian-Xiang Hu
- Key Laboratory of the Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Miao Yu
- Key Laboratory of the Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Jie Zhao
- Key Laboratory of the Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan 430072, China
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195
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Nawy T, Bayer M, Mravec J, Friml J, Birnbaum KD, Lukowitz W. The GATA Factor HANABA TARANU Is Required to Position the Proembryo Boundary in the Early Arabidopsis Embryo. Dev Cell 2010; 19:103-13. [DOI: 10.1016/j.devcel.2010.06.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Revised: 04/07/2010] [Accepted: 04/23/2010] [Indexed: 12/22/2022]
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196
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Guseman JM, Lee JS, Bogenschutz NL, Peterson KM, Virata RE, Xie B, Kanaoka MM, Hong Z, Torii KU. Dysregulation of cell-to-cell connectivity and stomatal patterning by loss-of-function mutation in Arabidopsis chorus (glucan synthase-like 8). Development 2010; 137:1731-41. [PMID: 20430748 DOI: 10.1242/dev.049197] [Citation(s) in RCA: 144] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Patterning of stomata, valves on the plant epidermis, requires the orchestrated actions of signaling components and cell-fate determinants. To understand the regulation of stomatal patterning, we performed a genetic screen using a background that partially lacks stomatal signaling receptors. Here, we report the isolation and characterization of chorus (chor), which confers excessive proliferation of stomatal-lineage cells mediated by SPEECHLESS (SPCH). chor breaks redundancy among three ERECTA family genes and strongly enhances stomatal patterning defects caused by loss-of-function in TOO MANY MOUTHS. chor seedlings also exhibit incomplete cytokinesis and growth defects, including disruptions in root tissue patterning and root hair cell morphogenesis. CHOR encodes a putative callose synthase, GLUCAN SYNTHASE-LIKE 8 (GSL8), that is required for callose deposition at the cell plate, cell wall and plasmodesmata. Consistently, symplastic macromolecular diffusion between epidermal cells is significantly increased in chor, and proteins that do not normally move cell-to-cell, including a fluorescent protein-tagged SPCH, diffuse to neighboring cells. Such a phenotype is not a general trait caused by cytokinesis defects. Our findings suggest that the restriction of symplastic movement might be an essential step for the proper segregation of cell-fate determinants during stomatal development.
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Affiliation(s)
- Jessica M Guseman
- Department of Biology, University of Washington, Seattle, WA 98195, USA
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197
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Correia SM, Canhoto JM. Characterization of somatic embryo attached structures in Feijoa sellowiana Berg. (Myrtaceae). PROTOPLASMA 2010; 242:95-107. [PMID: 20336358 DOI: 10.1007/s00709-010-0130-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Accepted: 02/23/2010] [Indexed: 05/25/2023]
Abstract
The presence of an attached organ to somatic embryos of angiosperms connecting the embryo to the supporting tissue has been a subject of controversy. This study shows that 67% of the morphologically normal somatic embryos of Feijoa sellowiana possess this type of organ and that its formation was not affected by culture media composition. Histological and ultrastructural analysis indicated that the attached structures of somatic embryos displayed a great morphological diversity ranging from a few cells to massive and columnar structures. This contrast with the simple suspensors observed in zygotic embryos which were only formed by five cells. As well as the suspensor of zygotic embryos, somatic embryo attached structures undergo a process of degeneration in later stages of embryo development. Other characteristic shared by zygotic suspensors and somatic embryo attached structures was the presence of thick cell walls surrounding the cells. Elongated thin filaments were often associated with the structures attached to somatic embryos, whereas in other cases, tubular cells containing starch grains connected the embryo to the supporting tissue. These characteristics associated with the presence of plasmodesmata in the cells of the attached structures seem to indicate a role on embryo nutrition. However, cell proliferation in the attached structures resulting into new somatic embryos may also suggest a more complex relationship between the embryo and the structures connecting it to the supporting tissue.
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Affiliation(s)
- Sandra M Correia
- Laboratory of Plant Biotechnology, Centre for Pharmaceutical Studies, Department of Life Sciences, University of Coimbra, Ap. 3046, 3001-401, Coimbra, Portugal
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198
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Nakajima K, Uchiumi T, Okamoto T. Positional relationship between the gamete fusion site and the first division plane in the rice zygote. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:3101-5. [PMID: 20462944 PMCID: PMC2892148 DOI: 10.1093/jxb/erq131] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 04/26/2010] [Accepted: 04/27/2010] [Indexed: 05/20/2023]
Abstract
In angiosperms, a zygote generally divides into a two-celled proembryo consisting of an apical and a basal cell that possess different cell fates. This first division of the zygote is a putative step in the formation of the apical-basal axis of the proembryo. The gamete fusion activates the egg, and the gamete fusion site on the zygote has been reported to provide a possible cue for subsequent zygotic development and/or embryonic patterning in animals and plants. In this study, the gamete fusion site on the rice zygote was labelled by in vitro fertilization of a rice egg cell with a fluorescence-stained sperm cell. The positional relationship between the gamete fusion site and the division plane formed by zygotic cleavage was monitored using a fixed culture of the fusion site-labelled zygote until the two-celled proembryo stage. The results indicate that gamete fusion sites exist on two-celled proembryos with no relation to the position of the first division plane, and that the gamete fusion site on the rice zygote does not function as a determinant for positioning the zygote division plane.
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Affiliation(s)
| | | | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, 1-1 Minami-osawa Hachioji, Tokyo 192-0397, Japan
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199
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Rao KP, Richa T, Kumar K, Raghuram B, Sinha AK. In silico analysis reveals 75 members of mitogen-activated protein kinase kinase kinase gene family in rice. DNA Res 2010; 17:139-53. [PMID: 20395279 PMCID: PMC2885274 DOI: 10.1093/dnares/dsq011] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Mitogen-Activated Protein Kinase Kinase Kinases (MAPKKKs) are important components of MAPK cascades, which are universal signal transduction modules and play important role in plant growth and development. In the sequenced Arabidopsis genome 80 MAPKKKs were identified and currently being analysed for its role in different stress. In rice, economically important monocot cereal crop only five MAPKKKs were identified so far. In this study using computational analysis of sequenced rice genome we have identified 75 MAPKKKs. EST hits and full-length cDNA sequences (from KOME or Genbank database) of 75 MAPKKKs supported their existence. Phylogenetic analyses of MAPKKKs from rice and Arabidopsis have classified them into three subgroups, which include Raf, ZIK and MEKK. Conserved motifs in the deduced amino acid sequences of rice MAPKKKs strongly supported their identity as members of Raf, ZIK and MEKK subfamilies. Further expression analysis of the MAPKKKs in MPSS database revealed that their transcripts were differentially regulated in various stress and tissue-specific libraries.
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200
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Metzinger CA, Bergmann DC. Plant asymmetric cell division regulators: pinch-hitting for PARs? F1000 BIOLOGY REPORTS 2010; 2. [PMID: 20948808 PMCID: PMC2948360 DOI: 10.3410/b2-25] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Like animals, plants use asymmetric cell divisions to create pattern and diversity. Due to a rigid cell wall and lack of cell migrations, these asymmetric divisions incur the additional constraints of being locked into their initial orientations. How do plants specify and carry out asymmetric divisions? Intercellular communication has been suspected for some time and recent developments identify these signals as well as point to segregated determinants and proteins with PAR-like functions as parts of the answer.
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Affiliation(s)
- Carrie A Metzinger
- Department of Biology, 371 Serra Mall, Stanford University Stanford, CA, 94305-5020 USA
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