101
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Cai G, Cresti M. Microtubule motors and pollen tube growth--still an open question. PROTOPLASMA 2010; 247:131-43. [PMID: 20922548 DOI: 10.1007/s00709-010-0214-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2010] [Accepted: 09/16/2010] [Indexed: 05/24/2023]
Abstract
The growth of pollen tubes is supported by the continuous supply of secretory vesicles in the tip area. Movement and accumulation of vesicles is driven by the dynamic interplay between the actin cytoskeleton and motor proteins of the myosin family. A combination of the two protein systems is also responsible for the bidirectional movement of larger organelle classes. In contrast, the role of microtubules and microtubule-based motors is less clear and often ambiguous. Nevertheless, there is evidence which shows that the pollen tube contains a number of microtubule-based motors of the kinesin family. These motor proteins are likely to be associated with pollen tube organelles and, consequently, they have been hypothesized to participate in the distribution of organelles during pollen tube growth. Whether microtubule motor proteins take part in either the transport or positioning of organelles is not known for sure, but there is evidence for this second possibility. This review will discuss the current knowledge of microtubule-based motor proteins (including kinesins and hypothetical dyneins) and will make some hypothesis about their role in the pollen tube.
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Affiliation(s)
- Giampiero Cai
- Dipartimento Scienze Ambientali G. Sarfatti, Università di Siena, via Mattioli 4, 53100 Siena, Italy.
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102
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Liao F, Wang L, Yang LB, Peng X, Sun M. NtGNL1 plays an essential role in pollen tube tip growth and orientation likely via regulation of post-Golgi trafficking. PLoS One 2010; 5:e13401. [PMID: 20976165 PMCID: PMC2955533 DOI: 10.1371/journal.pone.0013401] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Accepted: 09/19/2010] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND Tobacco GNOM LIKE 1 (NtGNL1), a new member of the Big/GBF family, is characterized by a sec 7 domain. Thus, we proposed that NtGNL1 may function in regulating pollen tube growth for vesicle trafficking. METHODOLOGY/PRINCIPAL FINDINGS To test this hypothesis, we used an RNAi technique to down-regulate NtGNL1 expression and found that pollen tube growth and orientation were clearly inhibited. Cytological observations revealed that both timing and behavior of endocytosis was disrupted, and endosome trafficking to prevacuolar compartments (PVC) or multivesicular bodies (MVB) was altered in pollen tube tips. Moreover, NtGNL1 seemed to partially overlap with Golgi bodies, but clearly colocalized with putative late endosome compartments. We also observed that in such pollen tubes, the Golgi apparatus disassembled and fused with the endoplasmic reticulum, indicating abnormal post-Golgi trafficking. During this process, actin organization was also remodeled. CONCLUSIONS/SIGNIFICANCE Thus, we revealed that NtGNL1 is essential for pollen tube growth and orientation and it likely functions via stabilizing the structure of the Golgi apparatus and ensuring post-Golgi trafficking.
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Affiliation(s)
- Fanglei Liao
- Key Laboratory of Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan, China
- College of Chemistry and Life Science, Zhejiang Normal University, Jinhua, China
| | - Lu Wang
- Key Laboratory of Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan, China
- Biotechnology Department, Tobacco Research Institute of Chinese Academy of Agricultural Sciences, Qingdao, China
| | - Li-Bo Yang
- Key Laboratory of Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Xiongbo Peng
- Key Laboratory of Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Mengxiang Sun
- Key Laboratory of Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan, China
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103
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Liu J, Piette BMAG, Deeks MJ, Franklin-Tong VE, Hussey PJ. A compartmental model analysis of integrative and self-regulatory ion dynamics in pollen tube growth. PLoS One 2010; 5:e13157. [PMID: 20949135 PMCID: PMC2950844 DOI: 10.1371/journal.pone.0013157] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Accepted: 09/14/2010] [Indexed: 11/19/2022] Open
Abstract
Sexual reproduction in higher plants relies upon the polarised growth of pollen tubes. The growth-site at the pollen tube tip responds to signalling processes to successfully steer the tube to an ovule. Essential features of pollen tube growth are polarisation of ion fluxes, intracellular ion gradients, and oscillating dynamics. However, little is known about how these features are generated and how they are causally related. We propose that ion dynamics in biological systems should be studied in an integrative and self-regulatory way. Here we have developed a two-compartment model by integrating major ion transporters at both the tip and shank of pollen tubes. We demonstrate that the physiological features of polarised growth in the pollen tube can be explained by the localised distribution of transporters at the tip and shank. Model analysis reveals that the tip and shank compartments integrate into a self-regulatory dynamic system, however the oscillatory dynamics at the tip do not play an important role in maintaining ion gradients. Furthermore, an electric current travelling along the pollen tube contributes to the regulation of ion dynamics. Two candidate mechanisms for growth-induced oscillations are proposed: the transition of tip membrane into shank membrane, and growth-induced changes in kinetic parameters of ion transporters. The methodology and principles developed here are applicable to the study of ion dynamics and their interactions with other functional modules in any plant cellular system.
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Affiliation(s)
- Junli Liu
- School of Biological and Biomedical Sciences, University of Durham, Durham, United Kingdom
- Biophysical Sciences Institute, University of Durham, Durham, United Kingdom
| | - Bernard M. A. G. Piette
- Department of Mathematical Sciences, University of Durham, Durham, United Kingdom
- Biophysical Sciences Institute, University of Durham, Durham, United Kingdom
| | - Michael J. Deeks
- School of Biological and Biomedical Sciences, University of Durham, Durham, United Kingdom
- Biophysical Sciences Institute, University of Durham, Durham, United Kingdom
| | | | - Patrick J. Hussey
- School of Biological and Biomedical Sciences, University of Durham, Durham, United Kingdom
- Biophysical Sciences Institute, University of Durham, Durham, United Kingdom
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104
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Zhang H, Qu X, Bao C, Khurana P, Wang Q, Xie Y, Zheng Y, Chen N, Blanchoin L, Staiger CJ, Huang S. Arabidopsis VILLIN5, an actin filament bundling and severing protein, is necessary for normal pollen tube growth. THE PLANT CELL 2010; 22:2749-67. [PMID: 20807879 PMCID: PMC2947167 DOI: 10.1105/tpc.110.076257] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
A dynamic actin cytoskeleton is essential for pollen germination and tube growth. However, the molecular mechanisms underlying the organization and turnover of the actin cytoskeleton in pollen remain poorly understood. Villin plays a key role in the formation of higher-order structures from actin filaments and in the regulation of actin dynamics in eukaryotic cells. It belongs to the villin/gelsolin/fragmin superfamily of actin binding proteins and is composed of six gelsolin-homology domains at its core and a villin headpiece domain at its C terminus. Recently, several villin family members from plants have been shown to sever, cap, and bundle actin filaments in vitro. Here, we characterized a villin isovariant, Arabidopsis thaliana VILLIN5 (VLN5), that is highly and preferentially expressed in pollen. VLN5 loss-of-function retarded pollen tube growth and sensitized actin filaments in pollen grains and tubes to latrunculin B. In vitro biochemical analyses revealed that VLN5 is a typical member of the villin family and retains a full suite of activities, including barbed-end capping, filament bundling, and calcium-dependent severing. The severing activity was confirmed with time-lapse evanescent wave microscopy of individual actin filaments in vitro. We propose that VLN5 is a major regulator of actin filament stability and turnover that functions in concert with oscillatory calcium gradients in pollen and therefore plays an integral role in pollen germination and tube growth.
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Affiliation(s)
- Hua Zhang
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaolu Qu
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chanchan Bao
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Parul Khurana
- Department of Biological Sciences and Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907-2064
| | - Qiannan Wang
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yurong Xie
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Yiyan Zheng
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Naizhi Chen
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Laurent Blanchoin
- Institut de Recherches en Technologie et Sciences pour le Vivant, Laboratoire de Physiologie Cellulaire Végétale, Commissariat à l’Energie Atomique/Centre National de la Recherche Scientifique/Université Joseph Fourier, F38054 Grenoble, France
| | - Christopher J. Staiger
- Department of Biological Sciences and Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907-2064
| | - Shanjin Huang
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Address correspondence to
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105
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Khurana P, Henty JL, Huang S, Staiger AM, Blanchoin L, Staiger CJ. Arabidopsis VILLIN1 and VILLIN3 have overlapping and distinct activities in actin bundle formation and turnover. THE PLANT CELL 2010; 22:2727-48. [PMID: 20807878 PMCID: PMC2947172 DOI: 10.1105/tpc.110.076240] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Revised: 07/29/2010] [Accepted: 08/17/2010] [Indexed: 05/20/2023]
Abstract
Actin filament bundles are higher-order cytoskeletal structures that are crucial for the maintenance of cellular architecture and cell expansion. They are generated from individual actin filaments by the actions of bundling proteins like fimbrins, LIMs, and villins. However, the molecular mechanisms of dynamic bundle formation and turnover are largely unknown. Villins belong to the villin/gelsolin/fragmin superfamily and comprise at least five isovariants in Arabidopsis thaliana. Different combinations of villin isovariants are coexpressed in various tissues and cells. It is not clear whether these isovariants function together and act redundantly or whether they have unique activities. VILLIN1 (VLN1) is a simple filament-bundling protein and is Ca(2+) insensitive. Based on phylogenetic analyses and conservation of Ca(2+) binding sites, we predict that VLN3 is a Ca(2+)-regulated villin capable of severing actin filaments and contributing to bundle turnover. The bundling activity of both isovariants was observed directly with time-lapse imaging and total internal reflection fluorescence (TIRF) microscopy in vitro, and the mechanism mimics the "catch and zipper" action observed in vivo. Using time-lapse TIRF microscopy, we observed and quantified the severing of individual actin filaments by VLN3 at physiological calcium concentrations. Moreover, VLN3 can sever actin filament bundles in the presence of VLN1 when calcium is elevated to micromolar levels. Collectively, these results demonstrate that two villin isovariants have overlapping and distinct activities.
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Affiliation(s)
- Parul Khurana
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
| | - Jessica L. Henty
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
| | - Shanjin Huang
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
| | - Andrew M. Staiger
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
| | - Laurent Blanchoin
- Institut de Recherches en Technologie et Sciences pour le Vivant, Commissariat à l'Energie Atomique/Centre National de la Recherche Scientifique/Institut National de la Recherche Agronomique/Université Joseph Fourier, Commissariat à l’Energie Atomique Grenoble, F38054 Grenoble, France
| | - Christopher J. Staiger
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
- The Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907
- Address correspondence to
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106
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Winship LJ, Obermeyer G, Geitmann A, Hepler PK. Under pressure, cell walls set the pace. TRENDS IN PLANT SCIENCE 2010; 15:363-9. [PMID: 20483654 PMCID: PMC2999822 DOI: 10.1016/j.tplants.2010.04.005] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2010] [Revised: 04/16/2010] [Accepted: 04/21/2010] [Indexed: 05/18/2023]
Abstract
Significant controversy still swirls around the regulation of extension by tip-growing cells, particularly during stable, oscillatory growth of pollen tubes. One explanation proposes that turgor pressure is both the controlling and driving force. We refute this hypothesis on theoretical and evidentiary grounds. Direct measurement of intracellular pressure reveals constant turgor even as growth rates change. Measured ion fluxes, notably potassium, are insufficient to account for the requisite osmotic changes. Water movement, and hence pressure gradients, occur throughout the cell, unrestricted to local domains. Increases in hydrostatic pressure alone would force water out of the cell rather than cause increased growth. We have recently demonstrated concomitant changes in the apical cell wall that account fully for observed changes in growth rate.
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107
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Wei LQ, Xu WY, Deng ZY, Su Z, Xue Y, Wang T. Genome-scale analysis and comparison of gene expression profiles in developing and germinated pollen in Oryza sativa. BMC Genomics 2010; 11:338. [PMID: 20507633 PMCID: PMC2895629 DOI: 10.1186/1471-2164-11-338] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Accepted: 05/28/2010] [Indexed: 11/24/2022] Open
Abstract
Background Pollen development from the microspore involves a series of coordinated cellular events, and the resulting mature pollen has a specialized function to quickly germinate, produce a polar-growth pollen tube derived from the vegetative cell, and deliver two sperm cells into the embryo sac for double fertilization. The gene expression profiles of developing and germinated pollen have been characterised by use of the eudicot model plant Arabidopsis. Rice, one of the most important cereal crops, has been used as an excellent monocot model. A comprehensive analysis of transcriptome profiles of developing and germinated pollen in rice is important to understand the conserved and diverse mechanism underlying pollen development and germination in eudicots and monocots. Results We used Affymetrix GeneChip® Rice Genome Array to comprehensively analyzed the dynamic changes in the transcriptomes of rice pollen at five sequential developmental stages from microspores to germinated pollen. Among the 51,279 transcripts on the array, we found 25,062 pollen-preferential transcripts, among which 2,203 were development stage-enriched. The diversity of transcripts decreased greatly from microspores to mature and germinated pollen, whereas the number of stage-enriched transcripts displayed a "U-type" change, with the lowest at the bicellular pollen stage; and a transition of overrepresented stage-enriched transcript groups associated with different functional categories, which indicates a shift in gene expression program at the bicellular pollen stage. About 54% of the now-annotated rice F-box protein genes were expressed preferentially in pollen. The transcriptome profile of germinated pollen was significantly and positively correlated with that of mature pollen. Analysis of expression profiles and coexpressed features of the pollen-preferential transcripts related to cell cycle, transcription, the ubiquitin/26S proteasome system, phytohormone signalling, the kinase system and defense/stress response revealed five expression patterns, which are compatible with changes in major cellular events during pollen development and germination. A comparison of pollen transcriptomes between rice and Arabidopsis revealed that 56.6% of the rice pollen preferential genes had homologs in Arabidopsis genome, but 63.4% of these homologs were expressed, with a small proportion being expressed preferentially, in Arabidopsis pollen. Rice and Arabidopsis pollen had non-conservative transcription factors each. Conclusions Our results demonstrated that rice pollen expressed a set of reduced but specific transcripts in comparison with vegetative tissues, and the number of stage-enriched transcripts displayed a "U-type" change during pollen development, with the lowest at the bicellular pollen stage. These features are conserved in rice and Arabidopsis. The shift in gene expression program at the bicellular pollen stage may be important to the transition from earlier cell division to later pollen maturity. Pollen at maturity pre-synthesized transcripts needed for germination and early pollen tube growth. The transcription regulation associated with pollen development would have divergence between the two species. Our results also provide novel insights into the molecular program and key components of the regulatory network regulating pollen development and germination.
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Affiliation(s)
- Li Q Wei
- Research Center of Molecular and Developmental Biology, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
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108
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Łangowski Ł, Růžička K, Naramoto S, Kleine-Vehn J, Friml J. Trafficking to the Outer Polar Domain Defines the Root-Soil Interface. Curr Biol 2010; 20:904-8. [DOI: 10.1016/j.cub.2010.03.059] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Revised: 02/24/2010] [Accepted: 03/04/2010] [Indexed: 02/05/2023]
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109
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Ischebeck T, Seiler S, Heilmann I. At the poles across kingdoms: phosphoinositides and polar tip growth. PROTOPLASMA 2010; 240:13-31. [PMID: 20091065 PMCID: PMC2841259 DOI: 10.1007/s00709-009-0093-0] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2009] [Accepted: 11/20/2009] [Indexed: 05/20/2023]
Abstract
Phosphoinositides (PIs) are minor, but essential phospholipid constituents of eukaryotic membranes, and are involved in the regulation of various physiological processes. Recent genetic and cell biological advances indicate that PIs play important roles in the control of polar tip growth in plant cells. In root hairs and pollen tubes, PIs control directional membrane trafficking required for the delivery of cell wall material and membrane area to the growing tip. So far, the exact mechanisms by which PIs control polarity and tip growth are unresolved. However, data gained from the analysis of plant, fungal and animal systems implicate PIs in the control of cytoskeletal dynamics, ion channel activity as well as vesicle trafficking. The present review aims at giving an overview of PI roles in eukaryotic cells with a special focus on functions pertaining to the control of cell polarity. Comparative screening of plant and fungal genomes suggests diversification of the PI system with increasing organismic complexity. The evolutionary conservation of the PI system among eukaryotic cells suggests a role for PIs in tip growing cells in models where PIs so far have not been a focus of attention, such as fungal hyphae.
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Affiliation(s)
- Till Ischebeck
- Department of Plant Biochemistry, Georg-August-University Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
| | - Stephan Seiler
- Department of Microbiology and Genetics; and DFG Research Center Molecular Physiology of the Brain (CMPB), Georg-August-University Göttingen, Grisebachstraße 8, 37077 Göttingen, Germany
| | - Ingo Heilmann
- Department of Plant Biochemistry, Georg-August-University Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
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110
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Verchot-Lubicz J, Goldstein RE. Cytoplasmic streaming enables the distribution of molecules and vesicles in large plant cells. PROTOPLASMA 2010; 240:99-107. [PMID: 19937356 DOI: 10.1007/s00709-009-0088-x] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Accepted: 11/02/2009] [Indexed: 05/19/2023]
Abstract
Recent studies of aquatic and land plants show that similar phenomena determine intracellular transport of organelles and vesicles. This suggests that aspects of cell signaling involved in development and response to external stimuli are conserved across species. The movement of molecular motors along cytoskeletal filaments directly or indirectly entrains the fluid cytosol, driving cyclosis (i.e., cytoplasmic streaming) and affecting gradients of molecular species within the cell, with potentially important metabolic implications as a driving force for cell expansion. Research has shown that myosin XI functions in organelle movement driving cytoplasmic streaming in aquatic and land plants. Despite the conserved cytoskeletal machinery propelling organelle movement among aquatic and land plants, the velocities of cyclosis in plant cells varies according to cell types, developmental stage of the cell, and plant species. Here, we synthesize recent insights into cytoplasmic streaming, molecular gradients, cytoskeletal and membrane dynamics, and expand current cellular models to identify important gaps in current research.
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Affiliation(s)
- Jeanmarie Verchot-Lubicz
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA.
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111
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Kudla J, Batistic O, Hashimoto K. Calcium signals: the lead currency of plant information processing. THE PLANT CELL 2010; 22:541-63. [PMID: 20354197 PMCID: PMC2861448 DOI: 10.1105/tpc.109.072686] [Citation(s) in RCA: 634] [Impact Index Per Article: 45.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Ca(2+) signals are core transducers and regulators in many adaptation and developmental processes of plants. Ca(2+) signals are represented by stimulus-specific signatures that result from the concerted action of channels, pumps, and carriers that shape temporally and spatially defined Ca(2+) elevations. Cellular Ca(2+) signals are decoded and transmitted by a toolkit of Ca(2+) binding proteins that relay this information into downstream responses. Major transduction routes of Ca(2+) signaling involve Ca(2+)-regulated kinases mediating phosphorylation events that orchestrate downstream responses or comprise regulation of gene expression via Ca(2+)-regulated transcription factors and Ca(2+)-responsive promoter elements. Here, we review some of the remarkable progress that has been made in recent years, especially in identifying critical components functioning in Ca(2+) signal transduction, both at the single-cell and multicellular level. Despite impressive progress in our understanding of the processing of Ca(2+) signals during the past years, the elucidation of the exact mechanistic principles that underlie the specific recognition and conversion of the cellular Ca(2+) currency into defined changes in protein-protein interaction, protein phosphorylation, and gene expression and thereby establish the specificity in stimulus response coupling remain to be explored.
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Affiliation(s)
- Jörg Kudla
- Institut für Botanik, Universität Münster, 48149 Münster, Germany.
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112
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Rincón-Zachary M, Teaster ND, Sparks JA, Valster AH, Motes CM, Blancaflor EB. Fluorescence resonance energy transfer-sensitized emission of yellow cameleon 3.60 reveals root zone-specific calcium signatures in Arabidopsis in response to aluminum and other trivalent cations. PLANT PHYSIOLOGY 2010; 152:1442-58. [PMID: 20053711 PMCID: PMC2832233 DOI: 10.1104/pp.109.147256] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2009] [Accepted: 01/03/2010] [Indexed: 05/02/2023]
Abstract
Fluorescence resonance energy transfer-sensitized emission of the yellow cameleon 3.60 was used to study the dynamics of cytoplasmic calcium ([Ca(2+)](cyt)) in different zones of living Arabidopsis (Arabidopsis thaliana) roots. Transient elevations of [Ca(2+)](cyt) were observed in response to glutamic acid (Glu), ATP, and aluminum (Al(3+)). Each chemical induced a [Ca(2+)](cyt) signature that differed among the three treatments in regard to the onset, duration, and shape of the response. Glu and ATP triggered patterns of [Ca(2+)](cyt) increases that were similar among the different root zones, whereas Al(3+) evoked [Ca(2+)](cyt) transients that had monophasic and biphasic shapes, most notably in the root transition zone. The Al(3+)-induced [Ca(2+)](cyt) increases generally started in the maturation zone and propagated toward the cap, while the earliest [Ca(2+)](cyt) response after Glu or ATP treatment occurred in an area that encompassed the meristem and elongation zone. The biphasic [Ca(2+)](cyt) signature resulting from Al(3+) treatment originated mostly from cortical cells located at 300 to 500 mu m from the root tip, which could be triggered in part through ligand-gated Glu receptors. Lanthanum and gadolinium, cations commonly used as Ca(2+) channel blockers, elicited [Ca(2+)](cyt) responses similar to those induced by Al(3+). The trivalent ion-induced [Ca(2+)](cyt) signatures in roots of an Al(3+)-resistant and an Al(3+)-sensitive mutant were similar to those of wild-type plants, indicating that the early [Ca(2+)](cyt) changes we report here may not be tightly linked to Al(3+) toxicity but rather to a general response to trivalent cations.
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Affiliation(s)
- Magaly Rincón-Zachary
- Department of Biology, College of Science and Mathematics, Midwestern State University, Wichita Falls, Texas 76308, USA.
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113
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Rounds CM, Hepler PK, Fuller SJ, Winship LJ. Oscillatory growth in lily pollen tubes does not require aerobic energy metabolism. PLANT PHYSIOLOGY 2010; 152:736-46. [PMID: 20007440 PMCID: PMC2815890 DOI: 10.1104/pp.109.150896] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Accepted: 12/05/2009] [Indexed: 05/18/2023]
Abstract
Oscillatory tip growth in pollen tubes depends on prodigious amounts of energy. We have tested the hypothesis that oscillations in the electron transport chain lead to growth oscillations in lily (Lilium formosanum). Using three respiratory inhibitors, oligomycin, antimycin A, and cyanide, we find that pollen tube growth is much less sensitive to respiratory inhibition than respiration is. All three block respiration at concentrations severalfold lower than necessary to inhibit growth. Mitochondrial NAD(P)H and potentiometric JC-1 fluorescence, employed as markers for electron transport chain activity, rise rapidly in response to oligomycin, as expected. Pollen tube growth stops for several minutes before resuming. Subsequent growth has a lower mean rate, but continues to oscillate, albeit with a longer period. NAD(P)H fluorescence no longer exhibits coherent oscillations, and mitochondria no longer congregate directly behind the apex: they distribute evenly throughout the cell. Postinhibition growth relies on aerobic fermentation for energy production as revealed by an increase in ethanol in the media. These data suggest that oscillatory growth depends not on a single oscillatory pacemaker but rather is an emergent property arising from a number of stable limit cycles.
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114
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Hepler PK, Winship LJ. Calcium at the cell wall-cytoplast interface. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2010; 52:147-60. [PMID: 20377677 DOI: 10.1111/j.1744-7909.2010.00923.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Attention is given to the role of Ca(2+) at the interface between the cell wall and the cytoplast, especially as seen in pollen tubes. While the cytoplasm directs the synthesis and deposition of the wall, it is less well appreciated that the wall exerts considerable self control and influences activities of the cytoplasm. Ca(2+) participates as a crucial factor in this two way communication. In the cytoplasm, a [Ca(2+)] above 0.1 microM, regulates myriad processes, including secretion of cell wall components. In the cell wall Ca(2+), at 10 microM to 10 mM, binds negative charges on pectins and imparts structural rigidity to the wall. The plasma membrane occupies a pivotal position between these two compartments, where selective channels regulate influx of Ca(2+), and specific carriers pump the ion back into the wall. In addition we draw attention to different factors, which either respond to the wall or are present in the wall, and usually generate elevated [Ca(2+)] in the cytoplasm. These factors include: (i) stretch activated channels; (ii) calmodulin; (iii) annexins; (iv) wall associated kinases; (v) oligogalacturonides; and (vi) extracellular adenosine 5'-triphosphate. Together they provide evidence for a rich and multifaceted system of communication between the cytoplast and cell wall, with Ca(2+) as a carrier of information.
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Affiliation(s)
- Peter K Hepler
- Department of Biology, University of Massachusetts, Amherst, MA 01003, USA.
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115
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Laohavisit A, Davies JM. Ion Channels in Plant Development. ION CHANNELS AND PLANT STRESS RESPONSES 2010. [DOI: 10.1007/978-3-642-10494-7_4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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116
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Ye J, Zheng Y, Yan A, Chen N, Wang Z, Huang S, Yang Z. Arabidopsis formin3 directs the formation of actin cables and polarized growth in pollen tubes. THE PLANT CELL 2009; 21:3868-84. [PMID: 20023198 PMCID: PMC2814512 DOI: 10.1105/tpc.109.068700] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Revised: 11/07/2009] [Accepted: 11/18/2009] [Indexed: 05/18/2023]
Abstract
Cytoplasmic actin cables are the most prominent actin structures in plant cells, but the molecular mechanism underlying their formation is unknown. The function of these actin cables, which are proposed to modulate cytoplasmic streaming and intracellular movement of many organelles in plants, has not been studied by genetic means. Here, we show that Arabidopsis thaliana formin3 (AFH3) is an actin nucleation factor responsible for the formation of longitudinal actin cables in pollen tubes. The Arabidopsis AFH3 gene encodes a 785-amino acid polypeptide, which contains a formin homology 1 (FH1) and a FH2 domain. In vitro analysis revealed that the AFH3 FH1FH2 domains interact with the barbed end of actin filaments and have actin nucleation activity in the presence of G-actin or G actin-profilin. Overexpression of AFH3 in tobacco (Nicotiana tabacum) pollen tubes induced excessive actin cables, which extended into the tubes' apices. Specific downregulation of AFH3 eliminated actin cables in Arabidopsis pollen tubes and reduced the level of actin polymers in pollen grains. This led to the disruption of the reverse fountain streaming pattern in pollen tubes, confirming a role for actin cables in the regulation of cytoplasmic streaming. Furthermore, these tubes became wide and short and swelled at their tips, suggesting that actin cables may regulate growth polarity in pollen tubes. Thus, AFH3 regulates the formation of actin cables, which are important for cytoplasmic streaming and polarized growth in pollen tubes.
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Affiliation(s)
- Jianrong Ye
- College of Biological Science, China Agricultural University, Beijing 100193, China
- China Agricultural University-University of California-Riverside Joint Center for Biological Sciences and Biotechnology, China Agricultural University, Beijing 100193, China
| | - Yiyan Zheng
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - An Yan
- China Agricultural University-University of California-Riverside Joint Center for Biological Sciences and Biotechnology, China Agricultural University, Beijing 100193, China
- Department of Botany and Plant Sciences, Center for Plant Cell Biology, Institute of Integrative Genome Biology, University of California, Riverside, California 92521
| | - Naizhi Chen
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Zhangkui Wang
- College of Biological Science, China Agricultural University, Beijing 100193, China
- China Agricultural University-University of California-Riverside Joint Center for Biological Sciences and Biotechnology, China Agricultural University, Beijing 100193, China
| | - Shanjin Huang
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Address correspondence to or
| | - Zhenbiao Yang
- China Agricultural University-University of California-Riverside Joint Center for Biological Sciences and Biotechnology, China Agricultural University, Beijing 100193, China
- Department of Botany and Plant Sciences, Center for Plant Cell Biology, Institute of Integrative Genome Biology, University of California, Riverside, California 92521
- Address correspondence to or
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Rasmusson AG, Fernie AR, van Dongen JT. Alternative oxidase: a defence against metabolic fluctuations? PHYSIOLOGIA PLANTARUM 2009; 137:371-82. [PMID: 19558416 DOI: 10.1111/j.1399-3054.2009.01252.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
An increasing number of oscillating or fluctuating cellular systems have been recently described following the adaptation of fluorescent technology. In diverse organisms, these variously involve signalling factors, heat production, central metabolism and reactive oxygen species (ROS). In response to many plant stresses and primarily via the influence of ROS, changes in mRNA and protein levels or in vivo activity of alternative oxidase are often observed. However, in several investigations, a lack of correlation between the mRNA, protein and in vivo activity has been evident. This discrepancy has made it questionable whether the induction of alternative oxidase has importance in regulating alternative pathway activity in vivo, or being diagnostic for a role of alternative oxidase in stress tolerance and ROS avoidance. Here, we suggest a role of alternative oxidase in counteracting deleterious short-term metabolic fluctuations, especially under stress conditions. This model emphasizes the importance of peak activity for establishing protein levels and allows an amalgamation of the present status of physiological, cellular and molecular knowledge.
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Affiliation(s)
- Allan G Rasmusson
- Department of Cell and Organism Biology, Lund University, Sölvegatan 35B, SE-22362 Lund, Sweden.
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118
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Lenartowska M, Lenartowski R, Smoliński DJ, Wróbel B, Niedojadło J, Jaworski K, Bednarska E. Calreticulin expression and localization in plant cells during pollen-pistil interactions. PLANTA 2009; 231:67-77. [PMID: 19820965 DOI: 10.1007/s00425-009-1024-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Accepted: 09/21/2009] [Indexed: 05/24/2023]
Abstract
In this report, the distributions of calreticulin (CRT) and its transcripts in Haemanthus pollen, pollen tubes, and somatic cells of the hollow pistil were studied. Immunoblot analysis of protein extracts from mature anthers, dry and germinated pollen, growing pollen tubes, and unpollinated/pollinated pistils revealed a strong expression of CRT. Both in vitro and in situ studies confirmed the presence of CRT mRNA and protein in pollen/pollen tubes and somatic cells of the pistil transmitting tract. The co-localization of these molecules in ER of these cells suggests that the rough ER is a site of CRT translation. In the pistil, accumulation of the protein in pollen tubes, transmitting tract epidermis (tte), and micropylar cells of the ovule (mc) was correlated with the increased level of exchangeable calcium. Therefore, CRT as a Ca(2+)-binding/buffering protein, may be involved in mechanism of regulation calcium homeostasis in these cells. The functional role of the protein in pollen-pistil interactions, apart from its postulated function in cellular Ca(2+) homeostasis, is discussed.
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Affiliation(s)
- Marta Lenartowska
- Laboratory of Developmental Biology, Nicolaus Copernicus University, Gagarina 9, 87-100, Toruń, Poland.
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119
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Thomas C, Tholl S, Moes D, Dieterle M, Papuga J, Moreau F, Steinmetz A. Actin bundling in plants. ACTA ACUST UNITED AC 2009; 66:940-57. [DOI: 10.1002/cm.20389] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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120
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Domozych DS, Sørensen I, Willats WGT. The distribution of cell wall polymers during antheridium development and spermatogenesis in the Charophycean green alga, Chara corallina. ANNALS OF BOTANY 2009; 104:1045-56. [PMID: 19696037 PMCID: PMC2766190 DOI: 10.1093/aob/mcp193] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Revised: 05/27/2009] [Accepted: 07/08/2009] [Indexed: 05/19/2023]
Abstract
BACKGROUND AND AIMS The production of multicellular gametangia in green plants represents an early evolutionary development that is found today in all land plants and advanced clades of the Charophycean green algae. The processing of cell walls is an integral part of this morphogenesis yet very little is known about cell wall dynamics in early-divergent green plants such as the Charophycean green algae. This study represents a comprehensive analysis of antheridium development and spermatogenesis in the green alga, Chara corallina. METHODS Microarrays of cell wall components and immunocytochemical methods were employed in order to analyse cell wall macromolecules during antheridium development. KEY RESULTS Cellulose and pectic homogalacturonan epitopes were detected throughout all cell types of the developing antheridium including the unique cell wall protuberances of the shield cells and the cell walls of sperm cell initials. Arabinogalactan protein epitopes were distributed only in the epidermal shield cell layers and anti-xyloglucan antibody binding was only observed in the capitulum region that initially yields the sperm filaments. During the terminal stage of sperm development, no cell wall polymers recognized by the probes employed were found on the scale-covered sperm cells. CONCLUSIONS Antheridium development in C. corallina is a rapid event that includes the production of cell walls that contain polymers similar to those found in land plants. While pectic and cellulosic epitopes are ubiquitous in the antheridium, the distribution of arabinogalactan protein and xyloglucan epitopes is restricted to specific zones. Spermatogenesis also includes a major switch in the production of extracellular matrix macromolecules from cell walls to scales, the latter being a primitive extracellular matrix characteristic of green plants.
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Affiliation(s)
- David S Domozych
- Department of Biology and Skidmore Microscopy Imaging Center, Skidmore College, 815 North Broadway, Saratoga Springs, NY 12866, USA.
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McKenna ST, Kunkel JG, Bosch M, Rounds CM, Vidali L, Winship LJ, Hepler PK. Exocytosis precedes and predicts the increase in growth in oscillating pollen tubes. THE PLANT CELL 2009; 21:3026-40. [PMID: 19861555 PMCID: PMC2782290 DOI: 10.1105/tpc.109.069260] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2009] [Revised: 09/28/2009] [Accepted: 10/14/2009] [Indexed: 05/18/2023]
Abstract
We examined exocytosis during oscillatory growth in lily (Lilium formosanum and Lilium longiflorum) and tobacco (Nicotiana tabacum) pollen tubes using three markers: (1) changes in cell wall thickness by Nomarski differential interference contrast (DIC), (2) changes in apical cell wall fluorescence in cells stained with propidium iodide (PI), and (3) changes in apical wall fluorescence in cells expressing tobacco pectin methyl esterase fused to green fluorescent protein (PME-GFP). Using PI fluorescence, we quantified oscillatory changes in the amount of wall material from both lily and tobacco pollen tubes. Measurement of wall thickness by DIC was only possible with lily due to limitations of microscope resolution. PME-GFP, a direct marker for exocytosis, only provides information in tobacco because its expression in lily causes growth inhibition and cell death. We show that exocytosis in pollen tubes oscillates and leads the increase in growth rate; the mean phase difference between exocytosis and growth is -98 degrees +/- 3 degrees in lily and -124 degrees +/- 4 degrees in tobacco. Statistical analyses reveal that the anticipatory increase in wall material predicts, to a high degree, the rate and extent of the subsequent growth surge. Exocytosis emerges as a prime candidate for the initiation and regulation of oscillatory pollen tube growth.
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Affiliation(s)
| | - Joseph G. Kunkel
- Department of Biology, University of Massachusetts, Amherst, Massachusetts 01003
| | - Maurice Bosch
- Institute of Biological, Environmental, and Rural Sciences, Aberystwyth University Plas Gogerddan, Aberystwyth, SY23 3EB, United Kingdom
| | - Caleb M. Rounds
- Department of Biology, University of Massachusetts, Amherst, Massachusetts 01003
| | - Luis Vidali
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609
| | | | - Peter K. Hepler
- Department of Biology, University of Massachusetts, Amherst, Massachusetts 01003
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Qin Y, Leydon AR, Manziello A, Pandey R, Mount D, Denic S, Vasic B, Johnson MA, Palanivelu R. Penetration of the stigma and style elicits a novel transcriptome in pollen tubes, pointing to genes critical for growth in a pistil. PLoS Genet 2009; 5:e1000621. [PMID: 19714218 PMCID: PMC2726614 DOI: 10.1371/journal.pgen.1000621] [Citation(s) in RCA: 260] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Accepted: 07/29/2009] [Indexed: 12/03/2022] Open
Abstract
Pollen tubes extend through pistil tissues and are guided to ovules where they release sperm for fertilization. Although pollen tubes can germinate and elongate in a synthetic medium, their trajectory is random and their growth rates are slower compared to growth in pistil tissues. Furthermore, interaction with the pistil renders pollen tubes competent to respond to guidance cues secreted by specialized cells within the ovule. The molecular basis for this potentiation of the pollen tube by the pistil remains uncharacterized. Using microarray analysis in Arabidopsis, we show that pollen tubes that have grown through stigma and style tissues of a pistil have a distinct gene expression profile and express a substantially larger fraction of the Arabidopsis genome than pollen grains or pollen tubes grown in vitro. Genes involved in signal transduction, transcription, and pollen tube growth are overrepresented in the subset of the Arabidopsis genome that is enriched in pistil-interacted pollen tubes, suggesting the possibility of a regulatory network that orchestrates gene expression as pollen tubes migrate through the pistil. Reverse genetic analysis of genes induced during pollen tube growth identified seven that had not previously been implicated in pollen tube growth. Two genes are required for pollen tube navigation through the pistil, and five genes are required for optimal pollen tube elongation in vitro. Our studies form the foundation for functional genomic analysis of the interactions between the pollen tube and the pistil, which is an excellent system for elucidation of novel modes of cell–cell interaction. For successful reproduction in flowering plants, a single-celled pollen tube must rapidly extend through female pistil tissue, locate female gametes, and deliver sperm. Pollen tubes undergo a dramatic transformation while growing in the pistil; they grow faster compared to tubes grown in vitro and become competent to perceive and respond to navigation cues secreted by the pistil. The genes expressed by pollen tubes in response to growth in the pistil have not been characterized. We used a surgical procedure to obtain large quantities of uncontaminated pollen tubes that grew through the pistil and defined their transcriptome by microarray analysis. Importantly, we identify a set of genes that are specifically expressed in pollen tubes in response to their growth in the pistil and are not expressed during other stages of pollen or plant development. We analyzed mutants in 33 pollen tube–expressed genes using a sensitive series of pollen function assays and demonstrate that seven of these genes are critical for pollen tube growth; two specifically disrupt growth in the pistil. By identifying pollen tube genes induced by the pistil and describing a mutant analysis scheme to understand their function, we lay the foundation for functional genomic analysis of pollen–pistil interactions.
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Affiliation(s)
- Yuan Qin
- Department of Plant Sciences, University of Arizona, Tucson, Arizona, United States of America
| | - Alexander R. Leydon
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island, United States of America
| | - Ann Manziello
- Arizona Cancer Center and Southwest Environmental Health Sciences Center, University of Arizona, Tucson, Arizona, United States of America
| | - Ritu Pandey
- Arizona Cancer Center and Southwest Environmental Health Sciences Center, University of Arizona, Tucson, Arizona, United States of America
| | - David Mount
- Arizona Cancer Center and Southwest Environmental Health Sciences Center, University of Arizona, Tucson, Arizona, United States of America
| | - Stojan Denic
- Department of Electrical and Computer Engineering, University of Arizona, Tucson, Arizona, United States of America
| | - Bane Vasic
- Department of Electrical and Computer Engineering, University of Arizona, Tucson, Arizona, United States of America
| | - Mark A. Johnson
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island, United States of America
- * E-mail: (MAJ); (RP)
| | - Ravishankar Palanivelu
- Department of Plant Sciences, University of Arizona, Tucson, Arizona, United States of America
- * E-mail: (MAJ); (RP)
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Moscatelli A, Idilli AI. Pollen tube growth: a delicate equilibrium between secretory and endocytic pathways. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2009; 51:727-39. [PMID: 19686370 DOI: 10.1111/j.1744-7909.2009.00842.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Although pollen tube growth is a prerequisite for higher plant fertilization and seed production, the processes leading to pollen tube emission and elongation are crucial for understanding the basic mechanisms of tip growth. It was generally accepted that pollen tube elongation occurs by accumulation and fusion of Golgi-derived secretory vesicles (SVs) in the apical region, or clear zone, where they were thought to fuse with a restricted area of the apical plasma membrane (PM), defining the apical growth domain. Fusion of SVs at the tip reverses outside cell wall material and provides new segments of PM. However, electron microscopy studies have clearly shown that the PM incorporated at the tip greatly exceeds elongation and a mechanism of PM retrieval was already postulated in the mid-nineteenth century. Recent studies on endocytosis during pollen tube growth showed that different endocytic pathways occurred in distinct zones of the tube, including the apex, and led to a new hypothesis to explain vesicle accumulation at the tip; namely, that endocytic vesicles contribute substantially to V-shaped vesicle accumulation in addition to SVs and that exocytosis does not involve the entire apical domain. New insights suggested the intriguing hypothesis that modulation between exo- and endocytosis in the apex contributes to maintain PM polarity in terms of lipid/protein composition and showed distinct degradation pathways that could have different functions in the physiology of the cell. Pollen tube growth in vivo is closely regulated by interaction with style molecules. The study of endocytosis and membrane recycling in pollen tubes opens new perspectives to studying pollen tube-style interactions in vivo.
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Affiliation(s)
- Alessandra Moscatelli
- Dipartimento di Biologia L. Gorini, Università degli Studi di Milano, Milano, Italy.
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Wang Y, Chen T, Zhang C, Hao H, Liu P, Zheng M, Baluška F, Šamaj J, Lin J. Nitric oxide modulates the influx of extracellular Ca2+ and actin filament organization during cell wall construction in Pinus bungeana pollen tubes. THE NEW PHYTOLOGIST 2009; 182:851-862. [PMID: 19646068 DOI: 10.1111/j.1469-8137.2009.02820.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Nitric oxide (NO) plays a key role in many physiological processes in plants, including pollen tube growth. Here, effects of NO on extracellular Ca(2+) flux and microfilaments during cell wall construction in Pinus bungeana pollen tubes were investigated. Extracellular Ca(2+) influx, the intracellular Ca(2+) gradient, patterns of actin organization, vesicle trafficking and cell wall deposition upon treatment with the NO donor S-nitroso-N-acetylpenicillamine (SNAP), the NO synthase (NOS) inhibitor N(omega)-nitro-L-arginine (L-NNA) or the NO scavenger 2-(4-carboxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) were analyzed. SNAP enhanced pollen tube growth in a dose-dependent manner, while L-NNA and cPTIO inhibited NO production and arrested pollen tube growth. Noninvasive detection and microinjection of a Ca(2+) indicator revealed that SNAP promoted extracellular Ca(2+) influx and increased the steepness of the tip-focused Ca(2+) gradient, while cPTIO and L-NNA had the opposite effect. Fluorescence labeling indicated that SNAP, cPTIO and L-NNA altered actin organization, which subsequently affected vesicle trafficking. Finally, the configuration and/or distribution of cell wall components such as pectins and callose were significantly altered in response to L-NNA. Fourier transform infrared (FTIR) microspectroscopy confirmed the changes in the chemical composition of walls. Our results indicate that NO affects the configuration and distribution of cell wall components in pollen tubes by altering extracellular Ca(2+) influx and F-actin organization.
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Affiliation(s)
- Yuhua Wang
- Key Laboratory of Photosynthesis and Molecular Environmental Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing 100049, China
- The College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China
| | - Tong Chen
- Key Laboratory of Photosynthesis and Molecular Environmental Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Chunyang Zhang
- Key Laboratory of Photosynthesis and Molecular Environmental Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing 100049, China
| | - Huaiqing Hao
- Key Laboratory of Photosynthesis and Molecular Environmental Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Peng Liu
- Key Laboratory of Photosynthesis and Molecular Environmental Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing 100049, China
| | - Maozhong Zheng
- Key Laboratory of Photosynthesis and Molecular Environmental Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing 100049, China
| | - František Baluška
- Institute of Cellular and Molecular Botany, Rheinische Friedrich-Wilhelms-University Bonn, Department of Plant Cell Biology, Kirschallee 1, D-53115 Bonn, Germany
| | - Jozef Šamaj
- Institute of Cellular and Molecular Botany, Rheinische Friedrich-Wilhelms-University Bonn, Department of Plant Cell Biology, Kirschallee 1, D-53115 Bonn, Germany
- Institute of Plant Genetics and Biotechnology, Slovak Academy of Sciences, Akademicka 2, SK-95007, Nitra, Slovak Republic
- Palacky University Olomouc, Faculty of Natural Science, Olomouc 771 46, Czech Republic
| | - Jinxing Lin
- Key Laboratory of Photosynthesis and Molecular Environmental Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
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Vidali L, Rounds CM, Hepler PK, Bezanilla M. Lifeact-mEGFP reveals a dynamic apical F-actin network in tip growing plant cells. PLoS One 2009; 4:e5744. [PMID: 19478943 PMCID: PMC2684639 DOI: 10.1371/journal.pone.0005744] [Citation(s) in RCA: 174] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Accepted: 05/06/2009] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Actin is essential for tip growth in plants. However, imaging actin in live plant cells has heretofore presented challenges. In previous studies, fluorescent probes derived from actin-binding proteins often alter growth, cause actin bundling and fail to resolve actin microfilaments. METHODOLOGY/PRINCIPAL FINDINGS In this report we use Lifeact-mEGFP, an actin probe that does not affect the dynamics of actin, to visualize actin in the moss Physcomitrella patens and pollen tubes from Lilium formosanum and Nicotiana tobaccum. Lifeact-mEGFP robustly labels actin microfilaments, particularly in the apex, in both moss protonemata and pollen tubes. Lifeact-mEGFP also labels filamentous actin structures in other moss cell types, including cells of the gametophore. CONCLUSIONS/SIGNIFICANCE Lifeact-mEGFP, when expressed at optimal levels does not alter moss protonemal or pollen tube growth. We suggest that Lifeact-mEGFP represents an exciting new versatile probe for further studies of actin's role in tip growing plant cells.
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Affiliation(s)
- Luis Vidali
- Department of Biology, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Caleb M. Rounds
- Department of Biology, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Peter K. Hepler
- Department of Biology, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Magdalena Bezanilla
- Department of Biology, University of Massachusetts, Amherst, Massachusetts, United States of America
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126
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Stock C, Schwab A. Protons make tumor cells move like clockwork. Pflugers Arch 2009; 458:981-92. [PMID: 19437033 DOI: 10.1007/s00424-009-0677-8] [Citation(s) in RCA: 181] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2009] [Accepted: 04/28/2009] [Indexed: 01/10/2023]
Abstract
Cancer accounts for 13% of the yearly total mortality worldwide. Most cancer deaths are the sequel of metastatic diseases rather than of primary tumor growth. Thus, the major challenge in tumor therapy is the tumor cells' ability to metastasize. The extent to which a tumor metastasizes correlates with the tumor cells' migratory activity. Tumor cell migration requires a coordinated formation and release of cell adhesion contacts, a controlled cytoskeletal dynamics, the digestion and reorganization of the extracellular matrix, and local ion and water transport across the plasma membrane. All of these operations depend on intracellular pH (pH(i)) and extracellular pH (pH(e)). Numerous H(+), HCO (3) (-) , and monocarboxylate transporters as well as different carbonic anhydrase isozymes have considerable impact on pH(i) and pH(e) which spotlights them as possible, potential targets for anticancer therapeutics. Especially in solid tumors whose vascularization is often not sufficient, tumor cells cope with hypoxia and the resulting glycolysis by overexpressing the Na(+)/H(+) exchanger NHE1, monocarboxylate transporters MCT1 and/or MCT4, and the carbonic anhydrase CA IX. NHE1, MCT, and CA IX activity lead to an acidification of the extracellular space in order to maintain the cytosolic pH homeostasis stable. The present article gives a review on how this characteristic, acidic tumor micro- and nanoenvironment controls tumor cell migration.
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Affiliation(s)
- Christian Stock
- Institut für Physiologie II, University of Münster, Robert-Koch-Str. 27b, 48149, Münster, Germany.
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127
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Sinclair A, Schenkel M, Mathur J. Signaling to the Actin Cytoskeleton During Cell Morphogenesis and Patterning. SIGNALING IN PLANTS 2009. [DOI: 10.1007/978-3-540-89228-1_7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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128
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Cai G, Cresti M. Organelle motility in the pollen tube: a tale of 20 years. JOURNAL OF EXPERIMENTAL BOTANY 2009; 60:495-508. [PMID: 19112169 DOI: 10.1093/jxb/ern321] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Organelle movement is an evident feature of pollen tubes and is essential for the process of tube growth because it enables the proper distribution of organelles and the accumulation of secretory vesicles in the tube apex. Organelles move along the actin filaments through dynamic interactions with myosin but other proteins are probably responsible for control of this activity. The role of microtubules and microtubule-based motors is less clear and somewhat enigmatic. Nevertheless, the pollen tube is an excellent cell model in which to study and analyse the molecular mechanisms that drive and control organelle motility in relation to plant cell expansion. Current knowledge and the main scientific discoveries in this field of research over the last 20 years are summarized here. Future prospects in the study of the molecular mechanisms that mediate organelle transport and vesicle accumulation during pollen tube elongation are also discussed.
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Affiliation(s)
- Giampiero Cai
- Dipartimento Scienze Ambientali, Università di Siena, via Mattioli 4, I-53100 Siena, Italy.
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129
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Cárdenas L. New findings in the mechanisms regulating polar growth in root hair cells. PLANT SIGNALING & BEHAVIOR 2009; 4:4-8. [PMID: 19568333 PMCID: PMC2634060 DOI: 10.4161/psb.4.1.7341] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Accepted: 11/03/2008] [Indexed: 05/07/2023]
Abstract
Root hairs cells are highly polarized cellular structures resulting from tip growth of specific root epidermal cells. Root-hair morphogenesis involves many aspects regulating tip growth such as exocytosis, ion flux, calcium homeostasis, reactive oxygen species (ROS), and cytoskeleton. These cells are excellent models for studying polar growth and can be challenged with many extracellular factors affecting the pattern of growth named Nod factors, elicitors, hormones, etc. The general scenery is that the well described tip-high intracellular Ca(2+) gradient plays a central role in regulating tip growth. On the other hand, ROS plays a key role in various processes, for example hypersensitive response, root hair development, hormone action, gravitropism and stress responses. However, ROS has recently emerged as a key player together with calcium in regulating polar growth, not only in root hair cells but also in pollen tubes, filamentous fungi and fucoid cells. Furthermore, Ca(2+)-permeable channel modulation by ROS has been demonstrated in Vicia faba guard cells and Arabidopsis root hairs. Recently, root hair cells were shown to experiment ROS, pH and calcium oscillations coupled to growth oscillation. These recent findings allow considering that root hair cells present a similar pattern of growth as described for pollen tubes.
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Affiliation(s)
- Luis Cárdenas
- Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México.
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130
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Ischebeck T, Stenzel I, Heilmann I. Type B phosphatidylinositol-4-phosphate 5-kinases mediate Arabidopsis and Nicotiana tabacum pollen tube growth by regulating apical pectin secretion. THE PLANT CELL 2008; 20:3312-30. [PMID: 19060112 PMCID: PMC2630452 DOI: 10.1105/tpc.108.059568] [Citation(s) in RCA: 147] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Revised: 11/13/2008] [Accepted: 11/21/2008] [Indexed: 05/18/2023]
Abstract
Phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P(2)] occurs in the apical plasma membrane of growing pollen tubes. Because enzymes responsible for PtdIns(4,5)P(2) production at that location are uncharacterized, functions of PtdIns(4,5)P(2) in pollen tube tip growth are unresolved. Two candidate genes encoding pollen-expressed Arabidopsis thaliana phosphatidylinositol-4-phosphate 5-kinases (PI4P 5-kinases) of Arabidopsis subfamily B were identified (PIP5K4 and PIP5K5), and their recombinant proteins were characterized as being PI4P 5-kinases. Pollen of T-DNA insertion lines deficient in both PIP5K4 and PIP5K5 exhibited reduced pollen germination and defects in pollen tube elongation. Fluorescence-tagged PIP5K4 and PIP5K5 localized to an apical plasma membrane microdomain in Arabidopsis and tobacco (Nicotiana tabacum) pollen tubes, and overexpression of either PIP5K4 or PIP5K5 triggered multiple tip branching events. Further studies using the tobacco system revealed that overexpression caused massive apical pectin deposition accompanied by plasma membrane invaginations. By contrast, callose deposition and cytoskeletal structures were unaltered in the overexpressors. Morphological effects depended on PtdIns(4,5)P(2) production, as an inactive enzyme variant did not produce any effects. The data indicate that excessive PtdIns(4,5)P(2) production by type B PI4P 5-kinases disturbs the balance of membrane trafficking and apical pectin deposition. Polar tip growth of pollen tubes may thus be modulated by PtdIns(4,5)P(2) via regulatory effects on membrane trafficking and/or apical pectin deposition.
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Affiliation(s)
- Till Ischebeck
- Department of Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University, 37077 Göttingen, Germany
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131
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Geisler DA, Sampathkumar A, Mutwil M, Persson S. Laying down the bricks: logistic aspects of cell wall biosynthesis. CURRENT OPINION IN PLANT BIOLOGY 2008; 11:647-52. [PMID: 18818118 DOI: 10.1016/j.pbi.2008.08.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2008] [Revised: 08/08/2008] [Accepted: 08/12/2008] [Indexed: 05/08/2023]
Abstract
Plant cell wall polysaccharides are synthesised at the plasma membrane and in the Golgi apparatus. Current research efforts mainly try to address how these molecules are synthesised or modified. However, it is clear that polysaccharide synthesis in the two compartments needs to be carried out in a coordinated fashion, and that carbohydrates and proteins that are delivered from the Golgi to the cell surface have to undergo a range of modifications. Consequently, there appears to be a need for a fine-tuned system that coalesces signals from the wall, synthesis of carbohydrate-based molecules and vesicle shuttling. Several recent papers have scratched the surface for an initial understanding of these linked processes. For example, the impairment of the proton pumping activity in the trans-Golgi network, which is part of the cell's trafficking system, results in growth defects, changes in Golgi stack morphology and cellulose deficiency. An increased understanding of how cell wall synthesis is coordinated with the secretory machinery may facilitate avenues for modulating cell wall contents and therefore overall plant biomass.
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Affiliation(s)
- Daniela A Geisler
- Max Planck Institute for Molecular Plant Physiology, Am Muehlenberg 1, 14476 Potsdam, Germany
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132
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Zhang D, Wengier D, Shuai B, Gui CP, Muschietti J, McCormick S, Tang WH. The pollen receptor kinase LePRK2 mediates growth-promoting signals and positively regulates pollen germination and tube growth. PLANT PHYSIOLOGY 2008; 148:1368-79. [PMID: 18799662 PMCID: PMC2577252 DOI: 10.1104/pp.108.124420] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Accepted: 09/10/2008] [Indexed: 05/03/2023]
Abstract
In flowering plants, the process of pollen germination and tube growth is required for successful fertilization. A pollen receptor kinase from tomato (Solanum lycopersicum), LePRK2, has been implicated in signaling during pollen germination and tube growth as well as in mediating pollen (tube)-pistil communication. Here we show that reduced expression of LePRK2 affects four aspects of pollen germination and tube growth. First, the percentage of pollen that germinates is reduced, and the time window for competence to germinate is also shorter. Second, the pollen tube growth rate is reduced both in vitro and in the pistil. Third, tip-localized superoxide production by pollen tubes cannot be increased by exogenous calcium ions. Fourth, pollen tubes have defects in responses to style extract component (STIL), an extracellular growth-promoting signal from the pistil. Pollen tubes transiently overexpressing LePRK2-fluorescent protein fusions had slightly wider tips, whereas pollen tubes coexpressing LePRK2 and its cytoplasmic partner protein KPP (a Rop-GEF) had much wider tips. Together these results show that LePRK2 positively regulates pollen germination and tube growth and is involved in transducing responses to extracellular growth-promoting signals.
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Affiliation(s)
- Dong Zhang
- Shanghai Institutes for Biological Sciences-University of California at Berkeley Center of Molecular Life Sciences, National Key Laboratory of Plant Molecular Genetics, Chinese Academy of Sciences, Shanghai, China
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133
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Lenartowska M, Michalska A. Actin filament organization and polarity in pollen tubes revealed by myosin II subfragment 1 decoration. PLANTA 2008; 228:891-896. [PMID: 18696106 DOI: 10.1007/s00425-008-0802-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2008] [Accepted: 07/29/2008] [Indexed: 05/26/2023]
Abstract
The actin cytoskeleton plays a crucial role in pollen tube growth. In elongating pollen tubes the organization and arrangement of actin filaments (AFs) differs between the shank and apical region. However, the orientation of AFs in pollen tubes has not yet been successfully demonstrated. In the present work we have used myosin II subfragment 1 (S1) decoration to determine the polarity of AFs in pollen tubes. Electron microscopy studies revealed that in the shank of the tube bundles of AFs exhibit uniform polarity with those close to the cell cortex having their barbed ends oriented towards the tip of the pollen tube while those in the cell center have their barbed ends oriented toward the base of the tube. At the subapex, some AFs are organized in closely packed and longitudinally oriented bundles and some form curved bundles adjacent to the cell membrane. In contrast, few AFs are dispersed with random orientation in the extreme apex of the pollen tube. Our results confirm that the direction of cytoplasmic streaming within pollen tubes is determined by the polarity of AFs in the bundles.
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Affiliation(s)
- Marta Lenartowska
- Laboratory of Developmental Biology, Faculty of Biology and Earth Sciences, Nicolaus Copernicus University, Gagarina 9, 87-100, Torun, Poland.
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134
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Yalovsky S, Bloch D, Sorek N, Kost B. Regulation of membrane trafficking, cytoskeleton dynamics, and cell polarity by ROP/RAC GTPases. PLANT PHYSIOLOGY 2008; 147:1527-43. [PMID: 18678744 PMCID: PMC2492628 DOI: 10.1104/pp.108.122150] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2008] [Accepted: 06/12/2008] [Indexed: 05/18/2023]
Affiliation(s)
- Shaul Yalovsky
- Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
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135
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Bove J, Vaillancourt B, Kroeger J, Hepler PK, Wiseman PW, Geitmann A. Magnitude and direction of vesicle dynamics in growing pollen tubes using spatiotemporal image correlation spectroscopy and fluorescence recovery after photobleaching. PLANT PHYSIOLOGY 2008; 147:1646-58. [PMID: 18508956 PMCID: PMC2492615 DOI: 10.1104/pp.108.120212] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Accepted: 05/19/2008] [Indexed: 05/17/2023]
Abstract
The delivery of cell wall material and membrane to growing plant cell surfaces requires the spatial and temporal coordination of secretory vesicle trafficking. Given the small size of vesicles, their dynamics is difficult to quantify. To quantitatively analyze vesicle dynamics in growing pollen tubes labeled with the styryl dye FM1-43, we applied spatiotemporal correlation spectroscopy on time-lapse series obtained with high-speed confocal laser scanning microscopy recordings. The resulting vector maps revealed that vesicles migrate toward the apex in the cell cortex and that they accumulate in an annulus-shaped region adjacent to the extreme tip and then turn back to flow rearward in the center of the tube. Fluorescence recovery after photobleaching confirmed vesicle accumulation in the shoulder of the apex, and it revealed that the extreme apex never recovers full fluorescence intensity. This is consistent with endocytotic activity occurring in this region. Fluorescence recovery after photobleaching analysis also allowed us to measure the turnover rate of the apical vesicle population, which was significantly more rapid than the theoretical rate computed based on requirements for new cell wall material. This may indicate that a significant portion of the vesicles delivered to the apex does not succeed in contacting the plasma membrane for delivery of their contents. Therefore, we propose that more than one passage into the apex may be needed for many vesicles before they fuse to the plasma membrane and deliver their contents.
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Affiliation(s)
- Jérôme Bove
- Département de sciences biologiques, Université de Montréal, Montreal, Quebec, Canada H1X 2B2
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136
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Hiscock SJ, Allen AM. Diverse cell signalling pathways regulate pollen-stigma interactions: the search for consensus. THE NEW PHYTOLOGIST 2008; 179:286-317. [PMID: 19086285 DOI: 10.1111/j.1469-8137.2008.02457.x] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Siphonogamy, the delivery of nonmotile sperm to the egg via a pollen tube, was a key innovation that allowed flowering plants (angiosperms) to carry out sexual reproduction on land without the need for water. This process begins with a pollen grain (male gametophyte) alighting on and adhering to the stigma of a flower. If conditions are right, the pollen grain germinates to produce a pollen tube. The pollen tube invades the stigma and grows through the style towards the ovary, where it enters an ovule, penetrates the embryo sac (female gametophyte) and releases two sperm cells, one of which fertilizes the egg, while the other fuses with the two polar nuclei of the central cell to form the triploid endosperm. The events before fertilization (pollen-pistil interactions) comprise a series of complex cellular interactions involving a continuous exchange of signals between the haploid pollen and the diploid maternal tissue of the pistil (sporophyte). In recent years, significant progress has been made in elucidating the molecular identity of these signals and the cellular interactions that they regulate. Here we review our current understanding of the cellular and molecular interactions that mediate the earliest of these interactions between the pollen and the pistil that occur on or within the stigma - the 'pollen-stigma interaction'.
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Affiliation(s)
- Simon J Hiscock
- School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK
| | - Alexandra M Allen
- School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK
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