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Harrell MA, Liu Z, Campbell BF, Chinsen O, Hong T, Das M. Arp2/3-dependent endocytosis ensures Cdc42 oscillations by removing Pak1-mediated negative feedback. J Cell Biol 2024; 223:e202311139. [PMID: 39012625 PMCID: PMC11259211 DOI: 10.1083/jcb.202311139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 05/10/2024] [Accepted: 07/01/2024] [Indexed: 07/17/2024] Open
Abstract
The GTPase Cdc42 regulates polarized growth in most eukaryotes. In the bipolar yeast Schizosaccharomyces pombe, Cdc42 activation cycles periodically at sites of polarized growth. These periodic cycles are caused by alternating positive feedback and time-delayed negative feedback loops. At each polarized end, negative feedback is established when active Cdc42 recruits the Pak1 kinase to prevent further Cdc42 activation. It is unclear how Cdc42 activation returns to each end after Pak1-dependent negative feedback. We find that disrupting branched actin-mediated endocytosis disables Cdc42 reactivation at the cell ends. Using experimental and mathematical approaches, we show that endocytosis-dependent Pak1 removal from the cell ends allows the Cdc42 activator Scd1 to return to that end to enable reactivation of Cdc42. Moreover, we show that Pak1 elicits its own removal via activation of endocytosis. These findings provide a deeper insight into the self-organization of Cdc42 regulation and reveal previously unknown feedback with endocytosis in the establishment of cell polarity.
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Affiliation(s)
| | - Ziyi Liu
- Department of Biochemistry and Cellular & Molecular Biology, University of Tennessee, Knoxville, TN, USA
| | | | - Olivia Chinsen
- Biology Department, Boston College, Chestnut Hill, MA, USA
| | - Tian Hong
- Department of Biochemistry and Cellular & Molecular Biology, University of Tennessee, Knoxville, TN, USA
| | - Maitreyi Das
- Biology Department, Boston College, Chestnut Hill, MA, USA
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2
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Wang Q, Xu Y, Zhao S, Jiang Y, Yi R, Guo Y, Huang S. Activation of actin-depolymerizing factor by CDPK16-mediated phosphorylation promotes actin turnover in Arabidopsis pollen tubes. PLoS Biol 2023; 21:e3002073. [PMID: 37011088 PMCID: PMC10101649 DOI: 10.1371/journal.pbio.3002073] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 04/13/2023] [Accepted: 03/11/2023] [Indexed: 04/05/2023] Open
Abstract
As the stimulus-responsive mediator of actin dynamics, actin-depolymerizing factor (ADF)/cofilin is subject to tight regulation. It is well known that kinase-mediated phosphorylation inactivates ADF/cofilin. Here, however, we found that the activity of Arabidopsis ADF7 is enhanced by CDPK16-mediated phosphorylation. We found that CDPK16 interacts with ADF7 both in vitro and in vivo, and it enhances ADF7-mediated actin depolymerization and severing in vitro in a calcium-dependent manner. Accordingly, the rate of actin turnover is reduced in cdpk16 pollen and the amount of actin filaments increases significantly at the tip of cdpk16 pollen tubes. CDPK16 phosphorylates ADF7 at Serine128 both in vitro and in vivo, and the phospho-mimetic mutant ADF7S128D has enhanced actin-depolymerizing activity compared to ADF7. Strikingly, we found that failure in the phosphorylation of ADF7 at Ser128 impairs its function in promoting actin turnover in vivo, which suggests that this phospho-regulation mechanism is biologically significant. Thus, we reveal that CDPK16-mediated phosphorylation up-regulates ADF7 to promote actin turnover in pollen.
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Affiliation(s)
- Qiannan Wang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yanan Xu
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Shuangshuang Zhao
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, China
- Key Laboratory of Plant Stress, Life Science College, Shandong Normal University, Jinan, China
| | - Yuxiang Jiang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Ran Yi
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yan Guo
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Shanjin Huang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
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3
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Zhou Z, Zheng S, Haq SIU, Zheng D, Qiu QS. Regulation of pollen tube growth by cellular pH and ions. JOURNAL OF PLANT PHYSIOLOGY 2022; 277:153792. [PMID: 35973258 DOI: 10.1016/j.jplph.2022.153792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Revised: 07/29/2022] [Accepted: 08/06/2022] [Indexed: 06/15/2023]
Abstract
Tip growth of the pollen tube is a model system for the study of cell polarity establishment in flowering plants. The tip growth of the pollen tube displays an oscillating pattern corresponding to cellular ion and pH dynamics. Therefore, cellular pH and ions play an important role in pollen growth and development. In this review, we summarized the current advances in understanding the function of cellular pH and ions in regulating pollen tube growth. We analyzed the physiological roles and underlying mechanisms of cellular pH and ions, including Ca2+, K+, and Cl-, in regulating pollen tube growth. We further examined the function of Ca2+ in regulating cytoskeletons, small G proteins, and cell wall development in relation to pollen tube growth. We also examined the regulatory roles of cellular pH in pollen tube growth as well as pH regulation of ion flow, cell wall development, auxin signaling, and cytoskeleton function in pollen. In addition, we assessed the regulation of pollen tube growth by proton pumps and the maintenance of pH homeostasis in the trans-Golgi network by ion transporters. The interplay of ion homeostasis and pH dynamics was also assessed. We discussed the unanswered questions regarding pollen tube growth that need to be addressed in the future.
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Affiliation(s)
- Zhenguo Zhou
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 73000, China.
| | - Sheng Zheng
- College of Life Sciences, Northwest Normal University, Lanzhou, Gansu, 730070, China; Academy of Plateau Science and Sustainability, Qinghai Normal University, Xining, Qinghai, 810016, China
| | - Syed Inzimam Ul Haq
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 73000, China
| | - Dianfeng Zheng
- College of Coastal Agricultural Sciences, Guangdong Ocean University, Zhanjiang, Guangdong, 524088, China
| | - Quan-Sheng Qiu
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 73000, China; Academy of Plateau Science and Sustainability, Qinghai Normal University, Xining, Qinghai, 810016, China; College of Coastal Agricultural Sciences, Guangdong Ocean University, Zhanjiang, Guangdong, 524088, China.
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4
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Guo J, He J, Dehesh K, Cui X, Yang Z. CamelliA-based simultaneous imaging of Ca2+ dynamics in subcellular compartments. PLANT PHYSIOLOGY 2022; 188:2253-2271. [PMID: 35218352 PMCID: PMC8968278 DOI: 10.1093/plphys/kiac020] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 12/17/2021] [Indexed: 06/14/2023]
Abstract
As a universal second messenger, calcium (Ca2+) transmits specific cellular signals via a spatiotemporal signature generated from its extracellular source and internal stores. Our knowledge of the mechanisms underlying the generation of a Ca2+ signature is hampered by limited tools for simultaneously monitoring dynamic Ca2+ levels in multiple subcellular compartments. To overcome the limitation and to further improve spatiotemporal resolutions, we have assembled a molecular toolset (CamelliA lines) in Arabidopsis (Arabidopsis thaliana) that enables simultaneous and high-resolution monitoring of Ca2+ dynamics in multiple subcellular compartments through imaging different single-colored genetically encoded calcium indicators. We uncovered several Ca2+ signatures in three types of Arabidopsis cells in response to internal and external cues, including rapid oscillations of cytosolic Ca2+ and apical plasma membrane Ca2+ influx in fast-growing Arabidopsis pollen tubes, the spatiotemporal relationship of Ca2+ dynamics in four subcellular compartments of root epidermal cells challenged with salt, and a shockwave-like Ca2+ wave propagating in laser-wounded leaf epidermis. These observations serve as a testimony to the wide applicability of the CamelliA lines for elucidating the subcellular sources contributing to the Ca2+ signatures in plants.
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Affiliation(s)
- Jingzhe Guo
- Institute for Integrative Genome Biology, University of California, Riverside, 92521 California, USA
- Department of Botany and Plant Sciences, University of California, Riverside, 92521 California, USA
| | - Jiangman He
- Institute for Integrative Genome Biology, University of California, Riverside, 92521 California, USA
- Department of Botany and Plant Sciences, University of California, Riverside, 92521 California, USA
| | - Katayoon Dehesh
- Institute for Integrative Genome Biology, University of California, Riverside, 92521 California, USA
- Department of Botany and Plant Sciences, University of California, Riverside, 92521 California, USA
| | - Xinping Cui
- Institute for Integrative Genome Biology, University of California, Riverside, 92521 California, USA
- Department of Statistics, University of California, Riverside, 92521 California, USA
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5
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Scheible N, Yoon GM, McCubbin AG. Calmodulin Domain Protein Kinase PiCDPK1 Regulates Pollen Tube Growth Polarity through Interaction with RhoGDI. PLANTS (BASEL, SWITZERLAND) 2022; 11:plants11030254. [PMID: 35161234 PMCID: PMC8838988 DOI: 10.3390/plants11030254] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 01/14/2022] [Accepted: 01/17/2022] [Indexed: 05/14/2023]
Abstract
The pollen-specific calcium-dependent protein kinase PiCDPK1 of Petunia inflata has previously been shown to regulate polarity in tip growth in pollen tubes. Here we report the identification of a Rho Guanine Dissociation Inhibitor (PiRhoGDI1) as a PiCDPK1 interacting protein. We demonstrate that PiRhoGDI1 and PiCDPK1 interact in a yeast 2-hybrid assay, as well as in an in vitro pull-down assay, and that PiRhoGDI1 is phosphorylated by PiCDPK1 in vitro. We further demonstrate the PiRhoGDI1 is capable of rescuing the loss of growth polarity phenotype caused by over-expressing PiCDPK1 in vivo using stable transgenic plants. We confirmed that PiRhoGDI1 interacts with a pollen-expressed ROP GTPase isoform consistent with the established role of RhoGDIs in negatively regulating GTPases through their membrane removal and locking them in an inactive cytosolic complex. ROP is a central regulator of polarity in tip growth, upstream of Ca2+, and PiCDPK1 over-expression has been previously reported to lead to dramatic elevation of cytosolic Ca2+ through a positive feedback loop. The discovery that PiCDPK1 impacts ROP regulation via PiRhoGDI1 suggests that PiCDPK1 acts as RhoGDI displacement factor and leads us to propose a model which we hypothesize regulates the rapid recycling of ROP GTPase at the pollen tube tip.
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6
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Bibeau JP, Galotto G, Wu M, Tüzel E, Vidali L. Quantitative cell biology of tip growth in moss. PLANT MOLECULAR BIOLOGY 2021; 107:227-244. [PMID: 33825083 PMCID: PMC8492783 DOI: 10.1007/s11103-021-01147-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 03/25/2021] [Indexed: 05/16/2023]
Abstract
KEY MESSAGE Here we review, from a quantitative point of view, the cell biology of protonemal tip growth in the model moss Physcomitrium patens. We focus on the role of the cytoskeleton, vesicle trafficking, and cell wall mechanics, including reviewing some of the existing mathematical models of tip growth. We provide a primer for existing cell biological tools that can be applied to the future study of tip growth in moss. Polarized cell growth is a ubiquitous process throughout the plant kingdom in which the cell elongates in a self-similar manner. This process is important for nutrient uptake by root hairs, fertilization by pollen, and gametophyte development by the protonemata of bryophytes and ferns. In this review, we will focus on the tip growth of moss cells, emphasizing the role of cytoskeletal organization, cytoplasmic zonation, vesicle trafficking, cell wall composition, and dynamics. We compare some of the existing knowledge on tip growth in protonemata against what is known in pollen tubes and root hairs, which are better-studied tip growing cells. To fully understand how plant cells grow requires that we deepen our knowledge in a variety of forms of plant cell growth. We focus this review on the model plant Physcomitrium patens, which uses tip growth as the dominant form of growth at its protonemal stage. Because mosses and vascular plants shared a common ancestor more than 450 million years ago, we anticipate that both similarities and differences between tip growing plant cells will provide mechanistic information of tip growth as well as of plant cell growth in general. Towards this mechanistic understanding, we will also review some of the existing mathematical models of plant tip growth and their applicability to investigate protonemal morphogenesis. We attempt to integrate the conclusions and data across cell biology and physical modeling to our current state of knowledge of polarized cell growth in P. patens and highlight future directions in the field.
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Affiliation(s)
- Jeffrey P Bibeau
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA, USA
| | - Giulia Galotto
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA, USA
| | - Min Wu
- Department of Mathematical Sciences, Worcester Polytechnic Institute, Worcester, MA, USA
- Bioinformatics and Computational Biology Program, Worcester Polytechnic Institute, Worcester, MA, USA
| | - Erkan Tüzel
- Bioengineering Department, Temple University, Philadelphia, PA, USA
| | - Luis Vidali
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA, USA.
- Bioinformatics and Computational Biology Program, Worcester Polytechnic Institute, Worcester, MA, USA.
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7
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Zhao W, Qu X, Zhuang Y, Wang L, Bosch M, Franklin-Tong VE, Xue Y, Huang S. Villin controls the formation and enlargement of punctate actin foci in pollen tubes. J Cell Sci 2020; 133:jcs237404. [PMID: 32051284 DOI: 10.1242/jcs.237404] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 02/01/2020] [Indexed: 11/20/2022] Open
Abstract
Self-incompatibility (SI) in the poppy Papaver rhoeas triggers dramatic alterations in actin within pollen tubes. However, how these actin alterations are mechanistically achieved remains largely unexplored. Here, we used treatment with the Ca2+ ionophore A23187 to mimic the SI-induced elevation in cytosolic Ca2+ and trigger formation of the distinctive F-actin foci. Live-cell imaging revealed that this remodeling involves F-actin fragmentation and depolymerization, accompanied by the rapid formation of punctate actin foci and subsequent increase in their size. We established that actin foci are generated and enlarged from crosslinking of fragmented actin filament structures. Moreover, we show that villins associate with actin structures and are involved in this actin reorganization process. Notably, we demonstrate that Arabidopsis VILLIN5 promotes actin depolymerization and formation of actin foci by fragmenting actin filaments, and controlling the enlargement of actin foci via bundling of actin filaments. Our study thus uncovers important novel insights about the molecular players and mechanisms involved in forming the distinctive actin foci in pollen tubes.
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Affiliation(s)
- Wanying Zhao
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Xiaolu Qu
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
- Key Laboratory of Horticultural Plant Biology (Ministry of Education), College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, China
| | - Yuhui Zhuang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Ludi Wang
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Plas Gogerddan, Aberystwyth, SY23 3EE, UK
| | - Maurice Bosch
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Plas Gogerddan, Aberystwyth, SY23 3EE, UK
| | - Vernonica E Franklin-Tong
- School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Yongbiao Xue
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
- Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Shanjin Huang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
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8
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Diao M, Qu X, Huang S. Calcium imaging in Arabidopsis pollen cells using G-CaMP5. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2018; 60:897-906. [PMID: 29424471 DOI: 10.1111/jipb.12642] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 02/07/2018] [Indexed: 05/18/2023]
Abstract
Calcium (Ca2+ ) signaling has been implicated in pollen germination and pollen tube growth. To date, however, we still know very little about how exactly Ca2+ signaling links to various physiological subcellular processes during pollen germination and pollen tube growth. Given that Ca2+ signaling is tightly related to the cytosolic concentration and dynamics of Ca2+ , it is vital to trace the dynamic changes in Ca2+ levels in order to decode Ca2+ signaling. Here, we demonstrate that G-CaMP5 serves well as an indicator for monitoring cytosolic Ca2+ dynamics in pollen cells. Using this probe, we show that cytosolic Ca2+ changes dramatically during pollen germination, and, as reported previously, Ca2+ forms a tip-focused gradient in the pollen tube and undergoes oscillation in the tip region during pollen tube growth. In particular, using G-CaMP5 allowed us to capture the dynamic changes in the cytosolic Ca2+ concentration ([Ca2+ ]cyt ) in pollen tubes in response to various exogenous treatments. Our data suggest that G-CaMP5 is a suitable probe for monitoring the dynamics of [Ca2+ ]cyt in pollen cells.
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Affiliation(s)
- Min Diao
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaolu Qu
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Shanjin Huang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
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9
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Barberini ML, Sigaut L, Huang W, Mangano S, Juarez SPD, Marzol E, Estevez J, Obertello M, Pietrasanta L, Tang W, Muschietti J. Calcium dynamics in tomato pollen tubes using the Yellow Cameleon 3.6 sensor. PLANT REPRODUCTION 2018; 31:159-169. [PMID: 29236154 DOI: 10.1007/s00497-017-0317-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Accepted: 12/04/2017] [Indexed: 06/07/2023]
Abstract
In vitro tomato pollen tubes show a cytoplasmic calcium gradient that oscillates with the same period as growth. Pollen tube growth requires coordination between the tip-focused cytoplasmic calcium concentration ([Ca2+]cyt) gradient and the actin cytoskeleton. This [Ca2+]cyt gradient is necessary for exocytosis of small vesicles, which contributes to the delivery of new membrane and cell wall at the pollen tube tip. The mechanisms that generate and maintain this [Ca2+]cyt gradient are not completely understood. Here, we studied calcium dynamics in tomato (Solanum lycopersicum) pollen tubes using transgenic tomato plants expressing the Yellow Cameleon 3.6 gene under the pollen-specific promoter LAT52. We use tomato as an experimental model because tomato is a Solanaceous plant that is easy to transform, and has an excellent genomic database and genetic stock center, and unlike Arabidopsis, tomato pollen is a good system to do biochemistry. We found that tomato pollen tubes showed an oscillating tip-focused [Ca2+]cyt gradient with the same period as growth. Then, we used a pharmacological approach to disturb the intracellular Ca2+ homeostasis, evaluating how the [Ca2+]cyt gradient, pollen germination and in vitro pollen tube growth were affected. We found that cyclopiazonic acid (CPA), a drug that inhibits plant PIIA-type Ca2+-ATPases, increased [Ca2+]cyt in the subapical zone, leading to the disappearance of the Ca2+ oscillations and inhibition of pollen tube growth. In contrast, 2-aminoethoxydiphenyl borate (2-APB), an inhibitor of Ca2+ released from the endoplasmic reticulum to the cytoplasm in animals cells, completely reduced [Ca2+]cyt at the tip of the tube, blocked the gradient and arrested pollen tube growth. Although both drugs have antagonistic effects on [Ca2+]cyt, both inhibited pollen tube growth triggering the disappearance of the [Ca2+]cyt gradient. When CPA and 2-APB were combined, their individual inhibitory effects on pollen tube growth were partially compensated. Finally, we found that GsMTx-4, a peptide from spider venom that blocks stretch-activated Ca2+ channels, inhibited tomato pollen germination and had a heterogeneous effect on pollen tube growth, suggesting that these channels are also involved in the maintenance of the [Ca2+]cyt gradient. All these results indicate that tomato pollen tube is an excellent model to study calcium dynamics.
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Affiliation(s)
- María Laura Barberini
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, "Dr. Héctor Torres" (INGEBI-CONICET), Vuelta de Obligado 2490, C1428ADN, Buenos Aires, Argentina
| | - Lorena Sigaut
- Instituto de Física de Buenos Aires (IFIBA-CONICET), Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, Ciudad Universitaria, Pabellón I, C1428EHA, Buenos Aires, Argentina
| | - Weijie Huang
- National Key Laboratory of Plant Molecular Genetics, Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, 200032, China
- Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, United Kingdom
| | - Silvina Mangano
- Fundación Instituto Leloir and Instituto de Investigaciones Bioquímicas de Buenos Aires (IIBBA-CONICET), Av. Patricias Argentinas 435, CP C1405BWE, Buenos Aires, Argentina
| | - Silvina Paola Denita Juarez
- Fundación Instituto Leloir and Instituto de Investigaciones Bioquímicas de Buenos Aires (IIBBA-CONICET), Av. Patricias Argentinas 435, CP C1405BWE, Buenos Aires, Argentina
| | - Eliana Marzol
- Fundación Instituto Leloir and Instituto de Investigaciones Bioquímicas de Buenos Aires (IIBBA-CONICET), Av. Patricias Argentinas 435, CP C1405BWE, Buenos Aires, Argentina
| | - José Estevez
- Fundación Instituto Leloir and Instituto de Investigaciones Bioquímicas de Buenos Aires (IIBBA-CONICET), Av. Patricias Argentinas 435, CP C1405BWE, Buenos Aires, Argentina
| | - Mariana Obertello
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, "Dr. Héctor Torres" (INGEBI-CONICET), Vuelta de Obligado 2490, C1428ADN, Buenos Aires, Argentina
| | - Lía Pietrasanta
- Instituto de Física de Buenos Aires (IFIBA-CONICET), Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, Ciudad Universitaria, Pabellón I, C1428EHA, Buenos Aires, Argentina
- Centro de Microscopías Avanzadas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, Ciudad Universitaria, Pabellón I, C1428EHA, Buenos Aires, Argentina
| | - Weihua Tang
- National Key Laboratory of Plant Molecular Genetics, Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, 200032, China
| | - Jorge Muschietti
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, "Dr. Héctor Torres" (INGEBI-CONICET), Vuelta de Obligado 2490, C1428ADN, Buenos Aires, Argentina.
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, Ciudad Universitaria, Pabellón II, C1428EGA, Buenos Aires, Argentina.
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10
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Li J, Li Y, Deng Y, Chen P, Feng F, Chen W, Zhou X, Wang Y. A calcium-dependent protein kinase, ZmCPK32, specifically expressed in maize pollen to regulate pollen tube growth. PLoS One 2018; 13:e0195787. [PMID: 29813101 PMCID: PMC5973587 DOI: 10.1371/journal.pone.0195787] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2017] [Accepted: 03/29/2018] [Indexed: 01/10/2023] Open
Abstract
Calcium-dependent protein kinases (CPKs) play an essential role in the regulation of pollen tube growth. Although CPK genes have been identified in maize, and some have been functionally characterized, the molecular function of ZmCPKs associated with pollen tube development remains less well studied. Here, we report that a pollen-specific CPK, ZmCPK32, is involved in the regulation of pollen germination and tube extension. ZmCPK32 exhibited CPK activity and was localized on the plasma membrane and punctate internal membrane compartments via N-terminal acylation. In situ hybridization and real-time PCR revealed that ZmCPK32 transcripts accumulated in pollen and expression was dramatically upregulated during shedding. To elucidate the function of this gene, we transiently expressed a ZmCPK32-GFP fusion protein in tobacco pollen using microparticle bombardment. ZmCPK32 accumulation inhibited pollen germination and reduced pollen tube growth, but this effect was abolished when the kinase-inactive variant was expressed, indicating that kinase activity is critical for its regulatory function. In addition, the plasma membrane localization of ZmCPK32 is essential for regulating polar growth, as pollen expressing the cytosol-localized kinase displayed reduced tube length but germinated well. Moreover, the constitutively active form of ZmCPK32 enhanced the reduction in the germination rate, indicating that the specific activation of ZmCPK32 via calcium ions at the cortical growth point is essential for regulating appropriate germination. The results suggest that ZmCPK32 is functionally associated with pollen tube growth, and could represent a potential target for breeding male-sterile maize.
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Affiliation(s)
- Jie Li
- Beijing Key Laboratory of Gene Resources and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Yihao Li
- Beijing Key Laboratory of Gene Resources and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Yanling Deng
- Beijing Key Laboratory of Gene Resources and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Ping Chen
- Beijing Key Laboratory of Gene Resources and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Fen Feng
- Beijing Key Laboratory of Gene Resources and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Wanwan Chen
- Beijing Key Laboratory of Gene Resources and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Xiaojin Zhou
- Beijing Key Laboratory of Gene Resources and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
- Department of Crop Genomic & Genetic Improvement, Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
- * E-mail: (YDW); (XJZ)
| | - Yingdian Wang
- Beijing Key Laboratory of Gene Resources and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
- * E-mail: (YDW); (XJZ)
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11
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Oscillatory fungal cell growth. Fungal Genet Biol 2017; 110:10-14. [PMID: 29229585 DOI: 10.1016/j.fgb.2017.12.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Revised: 11/26/2017] [Accepted: 12/06/2017] [Indexed: 12/20/2022]
Abstract
Cells are dynamic systems, the state of which undergoes constant alteration that results in morphological changes and movement. Many dynamic cellular processes that appear continuous are driven by underlying mechanisms that oscillate with distinct periods. For example eukaryotic cells do not grow continuously, but rather by pulsed extension of the periphery. Stepwise cell extension at the hyphal tips of several filamentous fungi was discovered 20 years ago, but only a few molecular details of the mechanism have been clarified since then. A recent study has provided evidence for correlations among intracellular Ca2+ levels, actin assembly, exocytosis and cell extension in growing hyphal tips. This suggests that pulsed Ca2+ influxes coordinate the temporal control of actin assembly and exocytosis, which results in stepwise cell extension. The coordinated oscillation of these machineries are likely to be ubiquitous among all eukaryotes. Indeed, intracellular Ca2+ levels and/or actin polymerization oscillate in mammalian and plant cells. This review summarizes the mechanisms of oscillation in several systems.
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Short-term influence of interfering ion activity change on ion-selective micropipette electrode potential; another factor that can affect the time needed for imaging in potentiometric SECM. Electrochem commun 2017. [DOI: 10.1016/j.elecom.2017.02.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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13
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Mammadov T, Deniz N, Rakhimzhanova A, Kılınçarslan Ö, Mammadov R. Studies on lilium species. INTERNATIONAL JOURNAL OF SECONDARY METABOLITE 2017. [DOI: 10.21448/ijsm.282978] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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14
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Lange M, Peiter E. Cytosolic free calcium dynamics as related to hyphal and colony growth in the filamentous fungal pathogen Colletotrichum graminicola. Fungal Genet Biol 2016; 91:55-65. [PMID: 27063059 DOI: 10.1016/j.fgb.2016.04.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 04/02/2016] [Accepted: 04/04/2016] [Indexed: 01/23/2023]
Abstract
Tip growth of pollen tubes and root hairs of plants is oscillatory and orchestrated by tip-focussed variations of cytosolic free calcium ([Ca(2+)]cyt). Hyphae of filamentous fungi are also tubular tip-growing cells, and components of the Ca(2+) signalling machinery, such as Ca(2+) channels and Ca(2+) sensors, are known to be important for fungal growth. In this study, we addressed the questions if tip-focussed [Ca(2+)]cyt transients govern hyphal and whole-colony growth in the maize pathogen Colletotrichum graminicola, and whether colony-wide [Ca(2+)]cyt dynamics rely on external Ca(2+) or internal Ca(2+) stores. Ratiometric fluorescence microscopy of individual hyphae expressing the Ca(2+) reporter Yellow Cameleon 3.6 revealed that Ca(2+) spikes in hyphal tips precede the re-initiation of growth after wounding. Tip-focussed [Ca(2+)]cyt spikes were also observed in undisturbed growing hyphae. They occurred not regularly and at a higher rate in hyphae growing at a medium-glass interface than in those growing on an agar surface. Hyphal tip growth was non-pulsatile, and growth speed was not correlated with the rate of spike occurrence. A possible relationship of [Ca(2+)]cyt spike generation and growth of whole colonies was assessed by using a codon-optimized version of the luminescent Ca(2+) reporter Aequorin. Depletion of extracellular free Ca(2+) abolished [Ca(2+)]cyt spikes nearly completely, but had only a modest effect on colony growth. In a pharmacological survey, some inhibitors targeting Ca(2+) influx or release from internal stores repressed growth strongly. However, although some of those inhibitors also affected [Ca(2+)]cyt spike generation, the effects on both parameters were not correlated. Collectively, the results indicate that tip growth of C. graminicola is non-pulsatile and not mechanistically linked to tip-focused or global [Ca(2+)]cyt spikes, which are likely a response to micro-environmental parameters, such as the physical properties of the growth surface.
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Affiliation(s)
- Mario Lange
- Plant Nutrition Laboratory, Institute of Agricultural and Nutritional Sciences (IAEW), Faculty of Natural Sciences III, Martin Luther University Halle-Wittenberg, 06099 Halle (Saale), Germany
| | - Edgar Peiter
- Plant Nutrition Laboratory, Institute of Agricultural and Nutritional Sciences (IAEW), Faculty of Natural Sciences III, Martin Luther University Halle-Wittenberg, 06099 Halle (Saale), Germany.
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Cyclic nucleotide-gated channel 18 is an essential Ca2+ channel in pollen tube tips for pollen tube guidance to ovules in Arabidopsis. Proc Natl Acad Sci U S A 2016; 113:3096-101. [PMID: 26929345 DOI: 10.1073/pnas.1524629113] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In flowering plants, pollen tubes are guided into ovules by multiple attractants from female gametophytes to release paired sperm cells for double fertilization. It has been well-established that Ca(2+) gradients in the pollen tube tips are essential for pollen tube guidance and that plasma membrane Ca(2+) channels in pollen tube tips are core components that regulate Ca(2+) gradients by mediating and regulating external Ca(2+) influx. Therefore, Ca(2+) channels are the core components for pollen tube guidance. However, there is still no genetic evidence for the identification of the putative Ca(2+) channels essential for pollen tube guidance. Here, we report that the point mutations R491Q or R578K in cyclic nucleotide-gated channel 18 (CNGC18) resulted in abnormal Ca(2+) gradients and strong pollen tube guidance defects by impairing the activation of CNGC18 in Arabidopsis. The pollen tube guidance defects of cngc18-17 (R491Q) and of the transfer DNA (T-DNA) insertion mutant cngc18-1 (+/-) were completely rescued by CNGC18. Furthermore, domain-swapping experiments showed that CNGC18's transmembrane domains are indispensable for pollen tube guidance. Additionally, we found that, among eight Ca(2+) channels (including six CNGCs and two glutamate receptor-like channels), CNGC18 was the only one essential for pollen tube guidance. Thus, CNGC18 is the long-sought essential Ca(2+) channel for pollen tube guidance in Arabidopsis.
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Zhou L, Lan W, Jiang Y, Fang W, Luan S. A calcium-dependent protein kinase interacts with and activates a calcium channel to regulate pollen tube growth. MOLECULAR PLANT 2014; 7:369-76. [PMID: 24121288 DOI: 10.1093/mp/sst125] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Calcium, as a ubiquitous second messenger, plays essential roles in tip-growing cells, such as animal neurons, plant pollen tubes, and root hairs. However, little is known concerning the regulatory mechanisms that code and decode Ca(2+) signals in plants. The evidence presented here indicates that a calcium-dependent protein kinase, CPK32, controls polar growth of pollen tubes. Overexpression of CPK32 disrupted the polar growth along with excessive Ca(2+) accumulation in the tip. A search of downstream effector molecules for CPK32 led to identification of a cyclic nucleotide-gated channel, CNGC18, as an interacting partner for CPK32. Co-expression of CPK32 and CNGC18 resulted in activation of CNGC18 in Xenopus oocytes where expression of CNGC18 alone did not exhibit significant calcium channel activity. Overexpression of CNGC18 produced a growth arrest phenotype coupled with accumulation of calcium in the tip, similar to that induced by CPK32 overexpression. Co-expression of CPK32 and CNGC18 had a synergistic effect leading to more severe depolarization of pollen tube growth. These results provide a potential feed-forward mechanism in which calcium-activated CPK32 activates CNGC18, further promoting calcium entry during the elevation phase of Ca(2+) oscillations in the polar growth of pollen tubes.
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Affiliation(s)
- Liming Zhou
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA
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Boisson-Dernier A, Lituiev DS, Nestorova A, Franck CM, Thirugnanarajah S, Grossniklaus U. ANXUR receptor-like kinases coordinate cell wall integrity with growth at the pollen tube tip via NADPH oxidases. PLoS Biol 2013; 11:e1001719. [PMID: 24302886 PMCID: PMC3841104 DOI: 10.1371/journal.pbio.1001719] [Citation(s) in RCA: 205] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 10/16/2013] [Indexed: 11/19/2022] Open
Abstract
Pollen tubes grow extremely rapidly to effect fertilization in plants. ANXUR receptor-like kinases facilitate this growth by linking the intracellular growth machinery of pollen tubes to the status of the extracellular matrix via H2O2 and Ca2+ signaling. It has become increasingly apparent that the extracellular matrix (ECM), which in plants corresponds to the cell wall, can influence intracellular activities in ways that go far beyond their supposedly passive mechanical support. In plants, growing cells use mechanisms sensing cell wall integrity to coordinate cell wall performance with the internal growth machinery to avoid growth cessation or loss of integrity. How this coordination precisely works is unknown. Previously, we reported that in the tip-growing pollen tube the ANXUR receptor-like kinases (RLKs) of the CrRLK1L subfamily are essential to sustain growth without loss of cell wall integrity in Arabidopsis. Here, we show that over-expression of the ANXUR RLKs inhibits growth by over-activating exocytosis and the over-accumulation of secreted cell wall material. Moreover, the characterization of mutations in two partially redundant pollen-expressed NADPH oxidases coupled with genetic interaction studies demonstrate that the ANXUR RLKs function upstream of these NADPH oxidases. Using the H2O2-sensitive HyPer and the Ca2+-sensitive YC3.60 sensors in NADPH oxidase-deficient mutants, we reveal that NADPH oxidases generate tip-localized, pulsating H2O2 production that functions, possibly through Ca2+ channel activation, to maintain a steady tip-focused Ca2+ gradient during growth. Our findings support a model where ECM-sensing receptors regulate reactive oxygen species production, Ca2+ homeostasis, and exocytosis to coordinate ECM-performance with the internal growth machinery. Tip-growing cells, such as plant root hairs and pollen tubes or fungal hyphae, are characterized by a tip-focused Ca2+ gradient. These tip-growing cells tightly coordinate the loosening and pressure-driven deformation of their extracellular matrix (ECM)—the cell wall in plant cells—by locally adding new membrane and cell wall materials. In pollen tubes, which grow at amazing speeds to effect fertilization in plants, a class of kinases called the ANXUR receptor-like kinases (RLKs) sense perturbations in cell wall integrity, and their loss leads to pollen tube rupture. Here, we gain new insights into the mechanism of cell wall surveillance by these RLKs in the model plant Arabidopsis. We show that over-expressing ANXUR RLKs over-activates exocytosis, causing an over-accumulation of secreted cell wall material that eventually leads to growth arrest. Moreover, we find that the ANXUR RLKs function upstream of NADPH oxidases, which are membrane-anchored enzymes that produce reactive oxygen species (ROS). Using H2O2- and Ca2+-sensitive reporters, we show that NADPH oxidases generate tip-localized H2O2 production, which is required to maintain a steady, tip-focused Ca2+ gradient that is essential for pollen tube growth. We postulate that ECM-sensing receptors, such as the ANXUR RLKs, regulate ROS production, Ca2+ homeostasis, and exocytosis to coordinate the status of the ECM with the cell's internal growth machinery.
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Affiliation(s)
- Aurélien Boisson-Dernier
- Institute of Plant Biology, University of Zürich, Zürich, Switzerland
- Zürich-Basel Plant Science Center, ETH Zürich, Zürich, Switzerland
- * E-mail: (ABD); (UG)
| | - Dmytro S. Lituiev
- Institute of Plant Biology, University of Zürich, Zürich, Switzerland
- Zürich-Basel Plant Science Center, ETH Zürich, Zürich, Switzerland
| | - Anna Nestorova
- Institute of Plant Biology, University of Zürich, Zürich, Switzerland
- Zürich-Basel Plant Science Center, ETH Zürich, Zürich, Switzerland
| | - Christina Maria Franck
- Institute of Plant Biology, University of Zürich, Zürich, Switzerland
- Zürich-Basel Plant Science Center, ETH Zürich, Zürich, Switzerland
| | - Sharme Thirugnanarajah
- Institute of Plant Biology, University of Zürich, Zürich, Switzerland
- Zürich-Basel Plant Science Center, ETH Zürich, Zürich, Switzerland
| | - Ueli Grossniklaus
- Institute of Plant Biology, University of Zürich, Zürich, Switzerland
- Zürich-Basel Plant Science Center, ETH Zürich, Zürich, Switzerland
- * E-mail: (ABD); (UG)
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Shachar-Hill B, Hill AE, Powell J, Skepper JN, Shachar-Hill Y. Mercury-sensitive water channels as possible sensors of water potentials in pollen. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:5195-205. [PMID: 24098048 PMCID: PMC3830494 DOI: 10.1093/jxb/ert311] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The growing pollen tube is central to plant reproduction and is a long-standing model for cellular tip growth in biology. Rapid osmotically driven growth is maintained under variable conditions, which requires osmosensing and regulation. This study explores the mechanism of water entry and the potential role of osmosensory regulation in maintaining pollen growth. The osmotic permeability of the plasmalemma of Lilium pollen tubes was measured from plasmolysis rates to be 1.32±0.31×10(-3) cm s(-1). Mercuric ions reduce this permeability by 65%. Simulations using an osmotic model of pollen tube growth predict that an osmosensor at the cell membrane controls pectin deposition at the cell tip; inhibiting the sensor is predicted to cause tip bursting due to cell wall thinning. It was found that adding mercury to growing pollen tubes caused such a bursting of the tips. The model indicates that lowering the osmotic permeability per se does not lead to bursting but rather to thickening of the tip. The time course of induced bursting showed no time lag and was independent of mercury concentration, compatible with a surface site of action. The submaximal bursting response to intermediate mercuric ion concentration was independent of the concentration of calcium ions, showing that bursting is not due to a competitive inhibition of calcium binding or entry. Bursting with the same time course was also shown by cells growing on potassium-free media, indicating that potassium channels (implicated in mechanosensing) are not involved in the bursting response. The possible involvement of mercury-sensitive water channels as osmosensors and current knowledge of these in pollen cells are discussed.
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Affiliation(s)
| | - Adrian E. Hill
- Department of Physiology, Development and Neuroscience, Cambridge University, Cambridge, UK
- * To whom correspondence should be addressed. E-mail:
| | - Janet Powell
- Multi-Imaging Centre, Cambridge University, Cambridge, UK
| | | | - Yair Shachar-Hill
- Department of Plant Biology, Plant Biology Building, Michigan State University, East Lansing, MI 48824-1312, USA
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Abstract
Cellular organelles move within the cellular volume and the effect of the resulting drag forces on the liquid causes bulk movement in the cytosol. The movement of both organelles and cytosol leads to an overall motion pattern called cytoplasmic streaming or cyclosis. This streaming enables the active and passive transport of molecules and organelles between cellular compartments. Furthermore, the fusion and budding of vesicles with and from the plasma membrane (exo/endocytosis) allow for transport of material between the inside and the outside of the cell. In the pollen tube, cytoplasmic streaming and exo/endocytosis are very active and fulfill several different functions. In this review, we focus on the logistics of intracellular motion and transport processes as well as their biophysical underpinnings. We discuss various modeling attempts that have been performed to understand both long-distance shuttling and short-distance targeting of organelles. We show how the combination of mechanical and mathematical modeling with cell biological approaches has contributed to our understanding of intracellular transport logistics.
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Affiliation(s)
- Youssef Chebli
- Département de Sciences Biologiques, Institut de Recherche en Biologie Végétale, Université de Montréal, Montréal, Québec, Canada
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PiSCP1 and PiCDPK2 Localize to Peroxisomes and Are Involved in Pollen Tube Growth in Petunia Inflata. PLANTS 2013; 2:72-86. [PMID: 27137367 PMCID: PMC4844289 DOI: 10.3390/plants2010072] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2013] [Revised: 02/19/2013] [Accepted: 02/26/2013] [Indexed: 01/13/2023]
Abstract
Petunia inflata small CDPK-interacting protein 1 (PiSCP1) was identified as a pollen expressed PiCDPK1 interacting protein using the yeast two hybrid system and the interaction confirmed using pull-down and phosphorylation assays. PiSCP1 is pollen specific and shares amino acid homology with uncharacterized proteins from diverse species of higher plants, but no protein of known function. Expression of PiSCP1-GFP in vivo inhibited pollen tube growth and was shown to localize to peroxisomes in growing pollen tubes. As PiCDPK1 is plasma membrane localized, we investigated the localization of a second isoform, PiCDPK2, and show that it co-localizes to peroxisomes with PiSCP1 and that the two proteins interact in the yeast 2 hybrid interaction assay, suggesting that interaction with the latter CDPK isoform is likely the one of biological relevance. Both PiCDPK2 and PiSCP1 affect pollen tube growth, presumably by mediating peroxisome function, however how they do so is currently not clear.
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Agudelo CG, Sanati Nezhad A, Ghanbari M, Naghavi M, Packirisamy M, Geitmann A. TipChip: a modular, MEMS-based platform for experimentation and phenotyping of tip-growing cells. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 73:1057-68. [PMID: 23217059 DOI: 10.1111/tpj.12093] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2012] [Revised: 11/23/2012] [Accepted: 12/05/2012] [Indexed: 05/20/2023]
Abstract
Large-scale phenotyping of tip-growing cells such as pollen tubes has hitherto been limited to very crude parameters such as germination percentage and velocity of growth. To enable efficient and high-throughput execution of more sophisticated assays, an experimental platform, the TipChip, was developed based on microfluidic and microelectromechanical systems (MEMS) technology. The device allows positioning of pollen grains or fungal spores at the entrances of serially arranged microchannels equipped with microscopic experimental set-ups. The tip-growing cells (pollen tubes, filamentous yeast or fungal hyphae) may be exposed to chemical gradients, microstructural features, integrated biosensors or directional triggers within the modular microchannels. The device is compatible with Nomarski optics and fluorescence microscopy. Using this platform, we were able to answer several outstanding questions on pollen tube growth. We established that, unlike root hairs and fungal hyphae, pollen tubes do not have a directional memory. Furthermore, pollen tubes were found to be able to elongate in air, raising the question of how and where water is taken up by the cell. The platform opens new avenues for more efficient experimentation and large-scale phenotyping of tip-growing cells under precisely controlled, reproducible conditions.
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Affiliation(s)
- Carlos G Agudelo
- Optical Bio-Microsystem Laboratory, Mechanical Engineering Department, Concordia University, Montreal, QC, Canada
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Zhao LN, Shen LK, Zhang WZ, Zhang W, Wang Y, Wu WH. Ca2+-dependent protein kinase11 and 24 modulate the activity of the inward rectifying K+ channels in Arabidopsis pollen tubes. THE PLANT CELL 2013; 25:649-61. [PMID: 23449501 PMCID: PMC3608784 DOI: 10.1105/tpc.112.103184] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Revised: 01/03/2013] [Accepted: 02/07/2013] [Indexed: 05/18/2023]
Abstract
Potassium (K(+)) influx into pollen tubes via K(+) transporters is essential for pollen tube growth; however, the mechanism by which K(+) transporters are regulated in pollen tubes remains unknown. Here, we report that Arabidopsis thaliana Ca(2+)-dependent protein kinase11 (CPK11) and CPK24 are involved in Ca(2+)-dependent regulation of the inward K(+) (K(+)in) channels in pollen tubes. Using patch-clamp analysis, we demonstrated that K(+)in currents of pollen tube protoplasts were inhibited by elevated [Ca(2+)]cyt. However, disruption of CPK11 or CPK24 completely impaired the Ca(2+)-dependent inhibition of K(+)in currents and enhanced pollen tube growth. Moreover, the cpk11 cpk24 double mutant exhibited similar phenotypes as the corresponding single mutants, suggesting that these two CDPKs function in the same signaling pathway. Bimolecular fluorescence complementation and coimmunoprecipitation experiments showed that CPK11 could interact with CPK24 in vivo. Furthermore, CPK11 phosphorylated the N terminus of CPK24 in vitro, suggesting that these two CDPKs work together as part of a kinase cascade. Electrophysiological assays demonstrated that the Shaker pollen K(+)in channel is the main contributor to pollen tube K(+)in currents and acts as the downstream target of the CPK11-CPK24 pathway. We conclude that CPK11 and CPK24 together mediate the Ca(2+)-dependent inhibition of K(+)in channels and participate in the regulation of pollen tube growth in Arabidopsis.
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Affiliation(s)
| | | | | | | | - Yi Wang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, National Plant Gene Research Centre, China Agricultural University, Beijing 100193, China
| | - Wei-Hua Wu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, National Plant Gene Research Centre, China Agricultural University, Beijing 100193, China
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Steinhorst L, Kudla J. Calcium - a central regulator of pollen germination and tube growth. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:1573-81. [PMID: 23072967 DOI: 10.1016/j.bbamcr.2012.10.009] [Citation(s) in RCA: 193] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Revised: 10/01/2012] [Accepted: 10/06/2012] [Indexed: 12/30/2022]
Abstract
Pollen tubes grow rapidly by very fast rates and reach extended lengths to bring about fertilization during plant reproduction. The pollen tube grows exclusively at its tip. Fundamental for such local, tip-focused growth are the presence of internal gradients and transmembrane fluxes of ions. Consequently, vegetative pollen tube cells are an excellent single cell model system to investigate cell biological processes of vesicle transport, cytoskeleton reorganization and regulation of ion transport. The second messenger Ca(2+) has emerged as a central and crucial modulator that not only regulates but also integrates the coordination each of these processes. In this review we reflect on recent advances in our understanding of the mechanisms of Ca(2+) function in pollen tube growth, focusing on its role in basic cellular processes such as control of cell growth, vesicular transport and intracellular signaling by localized gradients of second messengers. In particular we discuss new insights into the identity and role of Ca(2+) conductive ion channels and present experimental addressable hypotheses about their regulation. This article is part of a Special Issue entitled:12th European Symposium on Calcium.
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Affiliation(s)
- Leonie Steinhorst
- Institut für Biologie und Biotechnologie der Pflanzen, Universität Münster, Münster, Germany
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Kim HS, Czymmek KJ, Patel A, Modla S, Nohe A, Duncan R, Gilroy S, Kang S. Expression of the Cameleon calcium biosensor in fungi reveals distinct Ca(2+) signatures associated with polarized growth, development, and pathogenesis. Fungal Genet Biol 2012; 49:589-601. [PMID: 22683653 DOI: 10.1016/j.fgb.2012.05.011] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Revised: 05/22/2012] [Accepted: 05/24/2012] [Indexed: 11/19/2022]
Abstract
Calcium is a universal messenger that translates diverse environmental stimuli and developmental cues into specific cellular and developmental responses. While individual fungal species have evolved complex and often unique biochemical and structural mechanisms to exploit specific ecological niches and to adjust growth and development in response to external stimuli, one universal feature to all is that Ca(2+)-mediated signaling is involved. The lack of a robust method for imaging spatial and temporal dynamics of subcellular Ca(2+) (i.e., "Ca(2+) signature"), readily available in the plant and animal systems, has severely limited studies on how this signaling pathway controls fungal growth, development, and pathogenesis. Here, we report the first successful expression of a FRET (Förster Resonance Energy Transfer)-based Ca(2+) biosensor in fungi. Time-lapse imaging of Magnaporthe oryzae, Fusarium oxysporum, and Fusarium graminearum expressing this sensor showed that instead of a continuous gradient, the cytoplasmic Ca(2+) ([Ca(2+)](c)) change occurred in a pulsatile manner with no discernable gradient between pulses, and each species exhibited a distinct Ca(2+) signature. Furthermore, occurrence of pulsatile Ca(2+) signatures was age and development dependent, and major [Ca(2+)](c) transients were observed during hyphal branching, septum formation, differentiation into specialized plant infection structures, cell-cell contact and in planta growth. In combination with the sequenced genomes and ease of targeted gene manipulation of these and many other fungal species, the data, materials and methods developed here will help understand the mechanism underpinning Ca(2+)-mediated control of cellular and developmental changes, its role in polarized growth forms and the evolution of Ca(2+) signaling across eukaryotic kingdoms.
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Affiliation(s)
- Hye-Seon Kim
- Department of Plant Pathology, The Pennsylvania State University, University Park, PA 16802, United States
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Analysis of calcium signaling pathways in plants. Biochim Biophys Acta Gen Subj 2011; 1820:1283-93. [PMID: 22061997 DOI: 10.1016/j.bbagen.2011.10.012] [Citation(s) in RCA: 213] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Revised: 10/19/2011] [Accepted: 10/21/2011] [Indexed: 11/20/2022]
Abstract
BACKGROUND Calcium serves as a versatile messenger in many adaptation and developmental processes in plants. Ca2+ signals are represented by stimulus-specific spatially and temporally defined Ca2+ signatures. These Ca2+ signatures are detected, decoded and transmitted to downstream responses by a complex toolkit of Ca2+ binding proteins that function as Ca2+ sensors. SCOPE OF REVIEW This review will reflect on advancements in monitoring Ca2+ dynamics in plants. Moreover, it will provide insights in the extensive and complex toolkit of plant Ca2+ sensor proteins that relay the information presented in the Ca2+ signatures into phosphorylation events, changes in protein-protein interaction or regulation of gene expression. MAJOR CONCLUSIONS Plants' response to signals is encoded by different Ca2+ signatures. The plant decoding Ca2+ toolkit encompasses different families of Ca2+ sensors like Calmodulins (CaM), Calmodulin-like proteins (CMLs), Ca2+-dependent protein kinases (CDPKs), Calcineurin B-like proteins (CBLs) and their interacting kinases (CIPKs). These Ca2+ sensors are encoded by complex gene families and form intricate signaling networks in plants that enable specific, robust and flexible information processing. GENERAL SIGNIFICANCE This review provides new insights about the biochemical regulation, physiological functions and of newly identified target proteins of the major plant Ca2+ sensor families. This article is part of a Special Issue entitled Biochemical, biophysical and genetic approaches to intracellular calcium signaling.
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Tavares B, Dias PN, Domingos P, Moura TF, Feijó JA, Bicho A. Calcium-regulated anion channels in the plasma membrane of Lilium longiflorum pollen protoplasts. THE NEW PHYTOLOGIST 2011; 192:45-60. [PMID: 21668885 DOI: 10.1111/j.1469-8137.2011.03780.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
• Currents through anion channels in the plasma membrane of Lilium longiflorum pollen grain protoplasts were studied under conditions of symmetrical anionic concentrations by means of patch-clamp whole-cell configuration. • With Cl(-) -based intra- and extracellular solutions, three outward-rectifying anion conductances, I(Cl1) , I(Cl2) and I(Cl3) , were identified. These three activities were discriminated by differential rundown behaviour and sensitivity to 5-nitro-2-(phenylpropylamino)-benzoate (NPPB), which could not be attributed to one or more channel types. All shared strong outward rectification, activated instantaneously and displayed a slow time-dependent activation for positive potentials. All showed modulation by intracellular calcium ([Ca(2+) ](in) ), increasing intensity from 6.04 nM up to 0.5 mM (I(Cl1) ), or reaching a maximum value with 8.50 μM (I(Cl2) and I(Cl3) ). • After rundown, the anionic currents measured using NO(3) (-) -based solutions were indistinguishable, indicating that the permeabilities of the channels for Cl(-) and NO(3) (-) are similar. Additionally, unitary anionic currents were measured from outside-out excised patches, confirming the presence of individual anionic channels. • This study shows for the first time the presence of a large anionic conductance across the membrane of pollen protoplasts, resulting from the presence of Ca(2+) -regulated channels. A similar conductance was also found in germinated pollen. We hypothesize that these putative channels may be responsible for the large anionic fluxes previously detected by means of self-referencing vibrating probes.
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Affiliation(s)
- Bárbara Tavares
- REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
- Instituto Gulbenkian de Ciência, Oeiras, 2780-156 Oeiras, Portugal
- Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, C2, 1749-016 Lisboa, Portugal
| | - Pedro Nuno Dias
- REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
- Instituto Gulbenkian de Ciência, Oeiras, 2780-156 Oeiras, Portugal
- Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, C2, 1749-016 Lisboa, Portugal
| | - Patrícia Domingos
- REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
- Instituto Gulbenkian de Ciência, Oeiras, 2780-156 Oeiras, Portugal
- Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, C2, 1749-016 Lisboa, Portugal
| | - Teresa Fonseca Moura
- REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - José Alberto Feijó
- Instituto Gulbenkian de Ciência, Oeiras, 2780-156 Oeiras, Portugal
- Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, C2, 1749-016 Lisboa, Portugal
| | - Ana Bicho
- REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
- Instituto Gulbenkian de Ciência, Oeiras, 2780-156 Oeiras, Portugal
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Swanson SJ, Choi WG, Chanoca A, Gilroy S. In vivo imaging of Ca2+, pH, and reactive oxygen species using fluorescent probes in plants. ANNUAL REVIEW OF PLANT BIOLOGY 2011; 62:273-97. [PMID: 21370977 DOI: 10.1146/annurev-arplant-042110-103832] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Changes in the levels of Ca(2+), pH, and reactive oxygen species (ROS) are recognized as key cellular regulators involved in diverse physiological and developmental processes in plants. Critical to understanding how they exert such widespread control is an appreciation of their spatial and temporal dynamics at levels from organ to organelle and from seconds to many hours. With appropriate controls, fluorescent sensors can provide a robust approach with which to quantify such changes in Ca(2+), pH, and ROS in real time, in vivo. The fluorescent cellular probes available for visualization split into two broad classes: (a) dyes and (b) an increasingly diverse set of genetically encoded sensors based around green fluorescent proteins (GFPs). The GFP probes in particular can be targeted to well-defined subcellular locales, offering the possibility of high-resolution mapping of these signals within the cell.
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Affiliation(s)
- Sarah J Swanson
- Department of Botany, University of Wisconsin, Madison, Wisconsin 53706, USA.
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Papuga J, Hoffmann C, Dieterle M, Moes D, Moreau F, Tholl S, Steinmetz A, Thomas C. Arabidopsis LIM proteins: a family of actin bundlers with distinct expression patterns and modes of regulation. THE PLANT CELL 2010; 22:3034-52. [PMID: 20817848 PMCID: PMC2965535 DOI: 10.1105/tpc.110.075960] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Revised: 07/04/2010] [Accepted: 08/19/2010] [Indexed: 05/18/2023]
Abstract
Recently, a number of two LIM-domain containing proteins (LIMs) have been reported to trigger the formation of actin bundles, a major higher-order cytoskeletal assembly. Here, we analyzed the six Arabidopsis thaliana LIM proteins. Promoter-β-glucuronidase reporter studies revealed that WLIM1, WLIM2a, and WLIM2b are widely expressed, whereas PLIM2a, PLIM2b, and PLIM2c are predominantly expressed in pollen. LIM-green fluorescent protein (GFP) fusions all decorated the actin cytoskeleton and increased actin bundle thickness in transgenic plants and in vitro, although with different affinities and efficiencies. Remarkably, the activities of WLIMs were calcium and pH independent, whereas those of PLIMs were inhibited by high pH and, in the case of PLIM2c, by high [Ca(2+)]. Domain analysis showed that the C-terminal domain is key for the responsiveness of PLIM2c to pH and calcium. Regulation of LIM by pH was further analyzed in vivo by tracking GFP-WLIM1 and GFP-PLIM2c during intracellular pH modifications. Cytoplasmic alkalinization specifically promoted release of GFP-PLIM2c but not GFP-WLIM1, from filamentous actin. Consistent with these data, GFP-PLIM2c decorated long actin bundles in the pollen tube shank, a region of relatively low pH. Together, our data support a prominent role of Arabidopsis LIM proteins in the regulation of actin cytoskeleton organization and dynamics in sporophytic tissues and pollen.
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Affiliation(s)
| | | | | | | | | | | | | | - Clément Thomas
- Centre de Recherche Public-Santé, L-1526 Luxembourg, Luxembourg
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Staiger CJ, Poulter NS, Henty JL, Franklin-Tong VE, Blanchoin L. Regulation of actin dynamics by actin-binding proteins in pollen. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:1969-86. [PMID: 20159884 DOI: 10.1093/jxb/erq012] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
A dynamic network of polymers, the actin cytoskeleton, co-ordinates numerous fundamental cellular processes. In pollen tubes, organelle movements and cytoplasmic streaming, organization of the tip zone, vesicle trafficking, and tip growth have all been linked to actin-based function. Further, during the self-incompatibility response of Papaver rhoeas, destruction of the cytoskeleton is a primary target implicated in the rapid cessation of pollen tube growth and alterations in actin dynamics are associated with the initiation of programmed cell death. Surprisingly, these diverse cellular processes are accomplished with only a small amount of filamentous actin and a huge pool of polymerizable monomers. These observations hint at incredibly fast and complex actin dynamics in pollen. To understand the molecular mechanisms regulating actin dynamics in plant cells, the abundant actin monomer-binding proteins, a major filament nucleator, a family of bundling and severing proteins, and a modulator of growth at the barbed-end of actin filaments have been characterized biochemically. The activities of these proteins are generally consistent with textbook models for actin turnover. For example, the three monomer-binding proteins, profilin, ADF, and CAP, are thought to function synergistically to enhance turnover and the exchange of subunits between monomer and polymer pools. How individual actin filaments behave in living cells, however, remains largely unexplored. Actin dynamics were examined using variable angle epifluorescence microscopy (VAEM) in expanding hypocotyl epidermal cells. Our observations of single filament behaviour are not consistent with filament turnover by treadmilling, but rather represent a novel property called stochastic dynamics. A new model for the dynamic control of actin filament turnover in plant cells is presented.
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Affiliation(s)
- Christopher J Staiger
- Department of Biological Sciences and Bindley Bioscience Center, Purdue University, West Lafayette, IN 47907-2064, USA.
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Song LF, Zou JJ, Zhang WZ, Wu WH, Wang Y. Ion transporters involved in pollen germination and pollen tube tip-growth. PLANT SIGNALING & BEHAVIOR 2009; 4:1193-5. [PMID: 20514245 PMCID: PMC2819455 DOI: 10.4161/psb.4.12.10063] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Accepted: 09/11/2009] [Indexed: 05/08/2023]
Abstract
Pollen germination (PG) and pollen tube growth (PTG) play crucial roles in sexual reproduction of flowering plants by sending sperm cells to the ovule. These two processes are regarded as ideal model system for the study of cell signaling and cell polarized growth. It has been considered for a long time that ion transports across the pollen tube membranes are essential for pollen tube navigation and growth. Previous transcriptome analyses for Arabidopsis have shown that the transcripts related to cellular transport are correspondingly overrepresented during the process of pollen tube growth. Here, we showed that 459 transporter genes expressed during PG and PTG in Arabidopsis. In addition, the gene expression profiles of ion (including Ca(2+), H(+), K(+), Cl(-)) channels and transporters were further analyzed. This analysis provides novel information for the potential candidate genes involving in ion fluxes across the pollen tube membranes and in regulation of pollen tube tip growth.
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Affiliation(s)
- Lian-Fen Song
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, National Plant Gene Research Centre (Beijing), China Agricultural University, Beijing, China
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Shi YY, Tao WJ, Liang SP, Lü Y, Zhang L. Analysis of the tip-to-base gradient of CaM in pollen tube pulsant growth using in vivo CaM-GFP system. PLANT CELL REPORTS 2009; 28:1253-64. [PMID: 19536549 DOI: 10.1007/s00299-009-0725-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: 05/08/2009] [Revised: 05/26/2009] [Accepted: 05/27/2009] [Indexed: 05/27/2023]
Abstract
Ca(2+)-CaM signaling is involved in pollen tube development. However, the distribution and function of CaM and the downstream components of Ca(2+)-CaM signal in pollen tube development still need more exploration. Here we obtained the CaM-GFP fusion protein transgenic line of Nicotiana tobacum SRI, which allowed us to monitor CaM distribution pattern in vivo and provided a useful tool to observe CaM response to various exogenous stimulations and afforded solid evidences of the essential functions of CaM in pollen tube growth. CaM-GFP fusion gene was constructed under the control of Lat52-7 pollen-specific promoter and transformed into Nicotiana tobacum SRI. High level of CaM-GFP fluorescence was detected at the germinal pores and the tip-to-base gradient of fluorescence was observed in developing pollen tubes. The distribution of CaM at apical dome had close relationship with the pulsant growth mode of pollen tubes: when CaM aggregated at the apical dome, pollen tubes stepped into growth state; When CaM showed non-polarized distribution, pollen tubes stopped growing. In addition, after affording exogenous Ca(2+), calmidazolium (antagonism of CaM) or Brefeldin A (an inhibitor of membrane trafficking), CaM turned to a uniform distribution at the apical dome and pollen tube growth was held back. Taken together, our results showed that CaM played a vital role in pollen tube elongation and growth rate, and the oscillation of tip-to-base gradient of CaM was required for the normal pulsant growth of pollen tube.
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Affiliation(s)
- Ya-Ya Shi
- Key Lab of MOE for Plant Developmental Biology, Wuhan University, 430072, Wuhan, People's Republic of China
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Iwano M, Entani T, Shiba H, Kakita M, Nagai T, Mizuno H, Miyawaki A, Shoji T, Kubo K, Isogai A, Takayama S. Fine-tuning of the cytoplasmic Ca2+ concentration is essential for pollen tube growth. PLANT PHYSIOLOGY 2009; 150:1322-34. [PMID: 19474213 PMCID: PMC2705041 DOI: 10.1104/pp.109.139329] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Accepted: 05/20/2009] [Indexed: 05/17/2023]
Abstract
Pollen tube growth is crucial for the delivery of sperm cells to the ovule during flowering plant reproduction. Previous in vitro imaging of Lilium longiflorum and Nicotiana tabacum has shown that growing pollen tubes exhibit a tip-focused Ca(2+) concentration ([Ca(2+)]) gradient and regular oscillations of the cytosolic [Ca(2+)] ([Ca(2+)](cyt)) in the tip region. Whether this [Ca(2+)] gradient and/or [Ca(2+)](cyt) oscillations are present as the tube grows through the stigma (in vivo condition), however, is still not clear. We monitored [Ca(2+)](cyt) dynamics in pollen tubes under various conditions using Arabidopsis (Arabidopsis thaliana) and N. tabacum expressing yellow cameleon 3.60, a fluorescent calcium indicator with a large dynamic range. The tip-focused [Ca(2+)](cyt) gradient was always observed in growing pollen tubes. Regular oscillations of the [Ca(2+)](cyt), however, were rarely identified in Arabidopsis or N. tabacum pollen tubes grown under the in vivo condition or in those placed in germination medium just after they had grown through a style (semi-in vivo condition). On the other hand, regular oscillations were observed in vitro in both growing and nongrowing pollen tubes, although the oscillation amplitude was 5-fold greater in the nongrowing pollen tubes compared with growing pollen tubes. These results suggested that a submicromolar [Ca(2+)](cyt) in the tip region is essential for pollen tube growth, whereas a regular [Ca(2+)] oscillation is not. Next, we monitored [Ca(2+)] dynamics in the endoplasmic reticulum ([Ca(2+)](ER)) in relation to Arabidopsis pollen tube growth using yellow cameleon 4.60, which has a lower affinity for Ca(2+) compared with yellow cameleon 3.60. The [Ca(2+)](ER) in pollen tubes grown under the semi-in vivo condition was between 100 and 500 microm. In addition, cyclopiazonic acid, an inhibitor of ER-type Ca(2+)-ATPases, inhibited growth and decreased the [Ca(2+)](ER). Our observations suggest that the ER serves as one of the Ca(2+) stores in the pollen tube and cyclopiazonic acid-sensitive Ca(2+)-ATPases in the ER are required for pollen tube growth.
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Affiliation(s)
- Megumi Iwano
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara 630-0101, Japan.
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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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Monshausen GB, Messerli MA, Gilroy S. Imaging of the Yellow Cameleon 3.6 indicator reveals that elevations in cytosolic Ca2+ follow oscillating increases in growth in root hairs of Arabidopsis. PLANT PHYSIOLOGY 2008; 147:1690-8. [PMID: 18583529 PMCID: PMC2492656 DOI: 10.1104/pp.108.123638] [Citation(s) in RCA: 183] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Accepted: 06/17/2008] [Indexed: 05/17/2023]
Abstract
In tip-growing cells, the tip-high Ca(2+) gradient is thought to regulate the activity of components of the growth machinery, including the cytoskeleton, Ca(2+)-dependent regulatory proteins, and the secretory apparatus. In pollen tubes, both the Ca(2+) gradient and cell elongation show oscillatory behavior, reinforcing the link between the two. We report that in growing root hairs of Arabidopsis (Arabidopsis thaliana), an oscillating tip-focused Ca(2+) gradient can be resolved through imaging of a cytosolically expressed Yellow Cameleon 3.6 fluorescence resonance energy transfer-based Ca(2+) sensor. Both elongation of the root hairs and the associated tip-focused Ca(2+) gradient show a similar dynamic character, oscillating with a frequency of 2 to 4 min(-1). Cross-correlation analysis indicates that the Ca(2+) oscillations lag the growth oscillations by 5.3 +/- 0.3 s. However, growth never completely stops, even during the slow cycle of an oscillation, and the concomitant tip Ca(2+) level is always slightly elevated compared with the resting Ca(2+) concentration along the distal shaft, behind the growing tip. Artificially increasing Ca(2+) using the Ca(2+) ionophore A23187 leads to immediate cessation of elongation and thickening of the apical cell wall. In contrast, dissipating the Ca(2+) gradient using either the Ca(2+) channel blocker La(3+) or the Ca(2+) chelator EGTA is accompanied by an increase in the rate of cell expansion and eventual bursting of the root hair tip. These observations are consistent with a model in which the maximal oscillatory increase in cytosolic Ca(2+) is triggered by cell expansion associated with tip growth and plays a role in the subsequent restriction of growth.
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Michard E, Dias P, Feijó JA. Tobacco pollen tubes as cellular models for ion dynamics: improved spatial and temporal resolution of extracellular flux and free cytosolic concentration of calcium and protons using pHluorin and YC3.1 CaMeleon. ACTA ACUST UNITED AC 2008. [DOI: 10.1007/s00497-008-0076-x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Sardet C, Roegiers F, Dumollard R, Rouviere C, McDougall A. Calcium waves and oscillations in eggs. Biophys Chem 2007; 72:131-40. [PMID: 17029706 DOI: 10.1016/s0301-4622(98)00129-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 01/16/1998] [Accepted: 02/13/1998] [Indexed: 11/24/2022]
Abstract
Eggs from several protostomes (molluscs, annelids, nemerteans, etc.) and two deuterostomes (mammals and ascidians) display repetitive calcium signals. Oscillations in the level of intracellular calcium concentration are occasionally triggered by maturing hormones (as in some molluscs) and mostly observed after fertilization which occurs at different stages of the meiotic cell cycle (oocytes are arrested in prophase, metaphase I or metaphase II). In most eggs examined so far, calcium oscillations last until the end of meiosis just before male and female pronuclei form. This ability depends on the sensitivity of InsP3 channels and on the permeability of the plasma membrane to extracellular calcium. In eggs that undergo cytoplasmic reorganization at fertilization (annelids, nemerteans, ascidians, etc.) the repetitive calcium signals are waves that originate from localized cortical sites that become calcium waves pacemakers. In ascidians we have identified the site of initiation of repetitive calcium waves as an accumulation of endoplasmic reticulum sandwiched between the plasma membrane and an accumulation of mitochondria. We compare and discuss the generation of calcium signals in the different eggs, their relationship with the cell cycle and the possible roles they play during development.
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Affiliation(s)
- C Sardet
- Unité de Biologie Cellulaire Marine, URA 671, CNRS/UPMC, Observatoire, Station Zoologique, 06230 Villefranche-sur-Mer, France.
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Xiang Y, Huang X, Wang T, Zhang Y, Liu Q, Hussey PJ, Ren H. ACTIN BINDING PROTEIN 29 from Lilium pollen plays an important role in dynamic actin remodeling. THE PLANT CELL 2007; 19:1930-46. [PMID: 17586658 PMCID: PMC1955736 DOI: 10.1105/tpc.106.048413] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Villin/gelsolin/fragmin superfamily proteins have been shown to function in tip-growing plant cells. However, genes encoding gelsolin/fragmin do not exist in the Arabidopsis thaliana and rice (Oryza sativa) databases, and it is possible that these proteins are encoded by villin mRNA splicing variants. We cloned a 1006-bp full-length cDNA from Lilium longiflorum that encodes a 263-amino acid predicted protein sharing 100% identity with the N terminus of 135-ABP (Lilium villin) except for six C-terminal amino acids. The deduced 29-kD protein, Lilium ACTIN BINDING PROTEIN29 (ABP29), contains only the G1 and G2 domains and is the smallest identified member of the villin/gelsolin/fragmin superfamily. The purified recombinant ABP29 accelerates actin nucleation, blocks barbed ends, and severs actin filaments in a Ca(2+)- and/or phosphatidylinositol 4,5-bisphosphate-regulated manner in vitro. Microinjection of the protein into stamen hair cells disrupted transvacuolar strands whose backbone is mainly actin filament bundles. Transient expression of ABP29 by microprojectile bombardment of lily pollen resulted in actin filament fragmentation and inhibited pollen germination and tube growth. Our results suggest that ABP29 is a splicing variant of Lilium villin and a member of the villin/gelsolin/fragmin superfamily, which plays important roles in rearrangement of the actin cytoskeleton during pollen germination and tube growth.
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Affiliation(s)
- Yun Xiang
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education and College of Life Science, Beijing Normal University, Beijing, PR China
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Lovy-Wheeler A, Cárdenas L, Kunkel JG, Hepler PK. Differential organelle movement on the actin cytoskeleton in lily pollen tubes. ACTA ACUST UNITED AC 2007; 64:217-32. [PMID: 17245769 DOI: 10.1002/cm.20181] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We have examined the arrangement and movement of three major compartments, the endoplasmic reticulum (ER), mitochondria, and the vacuole during oscillatory, polarized growth in lily pollen tubes. These movements are dependent on the actin cytoskeleton, because they are strongly perturbed by the anti-microfilament drug, latrunculin-B, and unaffected by the anti-microtubule agent, oryzalin. The ER, which has been labeled with mGFP5-HDEL or cytochalasin D tetramethylrhodamine, displays an oscillatory motion in the pollen tube apex. First it moves apically in the cortical region, presumably along the cortical actin fringe, and then periodically folds inward creating a platform that transects the apical domain in a plate-like structure. Finally, the ER reverses its direction and moves basipetally through the central core of the pollen tube. When subjected to cross-correlation analysis, the formation of the platform precedes maximal growth rates by an average of 3 s (35-40 degrees ). Mitochondria, labeled with Mitotracker Green, are enriched in the subapical region, and their movement closely resembles that of the ER. The vacuole, labeled with carboxy-dichlorofluorescein diacetate, consists of thin tubules arranged longitudinally in a reticulate network, which undergoes active motion. In contrast to the mitochondria and ER, the vacuole is located back from the apex, and never extends into the apical clear zone. We have not been able to decipher an oscillatory pattern in vacuole motion. Because this motion is dependent on actin and not tubulin, we think this is due to a different myosin from that which drives the ER and mitochondria.
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Affiliation(s)
- Alenka Lovy-Wheeler
- Department of Biology and Plant Biology Graduate Program, Morrill Science Center III, University of Massachusetts, Amherst, Massachusetts 01003, USA
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40
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MS Channels in Tip‐Growing Systems. CURRENT TOPICS IN MEMBRANES 2007. [DOI: 10.1016/s1063-5823(06)58015-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/15/2023]
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Qu HY, Shang ZL, Zhang SL, Liu LM, Wu JY. Identification of hyperpolarization-activated calcium channels in apical pollen tubes of Pyrus pyrifolia. THE NEW PHYTOLOGIST 2007; 174:524-536. [PMID: 17447909 DOI: 10.1111/j.1469-8137.2007.02069.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The pollen tube has been widely used to study the mechanisms underlying polarized tip growth in plants. A steep tip-to-base gradient of free cytosolic calcium ([Ca(2+)](cyt)) is essential for pollen-tube growth. Local Ca(2+) influx mediated by Ca(2+)-permeable channels plays a key role in maintaining this [Ca(2+)](cyt) gradient. Here, we developed a protocol for successful isolation of spheroplasts from pollen tubes of Pyrus pyrifolia and identified a hyperpolarization-activated cation channel using the patch-clamp technique. We showed that the cation channel conductance displayed a strong selectivity for divalent cations, with a relative permeability sequence of barium (Ba(2+)) approximately Ca(2+) > magnesium (Mg(2+)) > strontium (Sr(2+)) > manganese (Mn(2+)). This channel conductance was selective for Ca(2+) over chlorine (Cl(-)) (relative permeability P(Ca)/P(Cl) = 14 in 10 mm extracellular Ca(2+)). We also showed that the channel was inhibited by the Ca(2+) channel blockers lanthanum (La(3+)) and gadolinium (Gd(3+)). Furthermore, channel activity depended on extracellular pH and pollen viability. We propose that the Ca(2+)-permeable channel is likely to play a role in mediating Ca(2+) influx into the growing pollen tubes to maintain the [Ca(2+)](cyt) gradient.
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Affiliation(s)
- Hai-Yong Qu
- College of Horticulture, NanJing Agricultural University, NanJing, China
- HuaiYin Institute of Technology, HuaiAn, China
| | - Zhong-Lin Shang
- College of Life Sciences, HeBei Normal University, Shi Jia Zhuang, China
| | - Shao-Ling Zhang
- College of Horticulture, NanJing Agricultural University, NanJing, China
| | | | - Ju-You Wu
- College of Horticulture, NanJing Agricultural University, NanJing, China
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Levin M. Is the early left-right axis like a plant, a kidney, or a neuron? The integration of physiological signals in embryonic asymmetry. ACTA ACUST UNITED AC 2006; 78:191-223. [PMID: 17061264 DOI: 10.1002/bdrc.20078] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Embryonic morphogenesis occurs along three orthogonal axes. While the patterning of the anterior-posterior and dorsal-ventral axes has been increasingly well-characterized, the left-right (LR) axis has only relatively recently begun to be understood at the molecular level. The mechanisms that ensure invariant LR asymmetry of the heart, viscera, and brain involve fundamental aspects of cell biology, biophysics, and evolutionary biology, and are important not only for basic science but also for the biomedicine of a wide range of birth defects and human genetic syndromes. The LR axis links biomolecular chirality to embryonic development and ultimately to behavior and cognition, revealing feedback loops and conserved functional modules occurring as widely as plants and mammals. This review focuses on the unique and fascinating physiological aspects of LR patterning in a number of vertebrate and invertebrate species, discusses several profound mechanistic analogies between biological regulation in diverse systems (specifically proposing a nonciliary parallel between kidney cells and the LR axis based on subcellular regulation of ion transporter targeting), highlights the possible importance of early, highly-conserved intracellular events that are magnified to embryo-wide scales, and lays out the most important open questions about the function, evolutionary origin, and conservation of mechanisms underlying embryonic asymmetry.
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Affiliation(s)
- Michael Levin
- Forsyth Center for Regenerative and Developmental Biology, The Forsyth Institute, and the Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115, USA.
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Malhó R, Liu Q, Monteiro D, Rato C, Camacho L, Dinis A. Signalling pathways in pollen germination and tube growth. PROTOPLASMA 2006; 228:21-30. [PMID: 16937051 DOI: 10.1007/s00709-006-0162-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2005] [Accepted: 06/08/2005] [Indexed: 05/11/2023]
Abstract
Signalling is an integral component in the establishment and maintenance of cellular identity. In plants, tip-growing cells represent an ideal system to investigate signal transduction mechanisms, and among these, pollen tubes (PTs) are one of the favourite models. Many signalling pathways have been identified during germination and tip growth, namely, Ca(2+), calmodulin, phosphoinositides, protein kinases, cyclic AMP, and GTPases. These constitute a large and complex web of signalling networks that intersect at various levels such as the control of vesicle targeting and fusion and the physical state of the actin cytoskeleton. Here we discuss some of the most recent advances made in PT signal transduction cascades and their implications for our future research. For reasons of space, emphasis was given to signalling mechanisms that control PT reorientation, so naturally many other relevant works have not been cited.
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Affiliation(s)
- R Malhó
- Departamento de Biologia Vegetal, Instituto de Ciência Aplicada e Tecnologia, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal.
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44
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Yoon GM, Dowd PE, Gilroy S, McCubbin AG. Calcium-dependent protein kinase isoforms in Petunia have distinct functions in pollen tube growth, including regulating polarity. THE PLANT CELL 2006; 18:867-78. [PMID: 16531501 PMCID: PMC1425858 DOI: 10.1105/tpc.105.037135] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2005] [Revised: 02/07/2006] [Accepted: 02/15/2006] [Indexed: 05/07/2023]
Abstract
Calcium is a key regulator of pollen tube growth, but little is known concerning the downstream components of the signaling pathways involved. We identified two pollen-expressed calmodulin-like domain protein kinases from Petunia inflata, CALMODULIN-LIKE DOMAIN PROTEIN KINASE1 (Pi CDPK1) and Pi CDPK2. Transient overexpression or expression of catalytically modified Pi CDPK1 disrupted pollen tube growth polarity, whereas expression of Pi CDPK2 constructs inhibited tube growth but not polarity. Pi CDPK1 exhibited plasma membrane localization most likely mediated by acylation, and we present evidence that suggests this localization is critical to the biological function of this kinase. Pi CDPK2 substantially localized to as yet unidentified internal membrane compartments, and this localization was again, at least partially, mediated by acylation. In contrast with Pi CDPK1, altering the localization of Pi CDPK2 did not noticeably alter the effect of overexpressing this isoform on pollen tube growth. Ca(2+) requirements for Pi CDPK1 activation correlated closely with Ca(2+) concentrations measured in the growth zone at the pollen tube apex. Interestingly, loss of polarity associated with overexpression of Pi CDPK1 was associated with elevated cytosolic Ca(2+) throughout the bulging tube tip, suggesting that Pi CDPK1 may participate in maintaining Ca(2+) homeostasis. These results are discussed in relation to previous models for Ca(2+) regulation of pollen tube growth.
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Affiliation(s)
- Gyeong Mee Yoon
- School of Biological Sciences and Center for Reproductive Biology, Washington State University, Pullman, Washington 99164, USA
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45
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Hwang JU, Gu Y, Lee YJ, Yang Z. Oscillatory ROP GTPase activation leads the oscillatory polarized growth of pollen tubes. Mol Biol Cell 2005; 16:5385-99. [PMID: 16148045 PMCID: PMC1266434 DOI: 10.1091/mbc.e05-05-0409] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Revised: 07/12/2005] [Accepted: 08/30/2005] [Indexed: 11/11/2022] Open
Abstract
Oscillation regulates a wide variety of processes ranging from chemotaxis in Dictyostelium through segmentation in vertebrate development to circadian rhythms. Most studies on the molecular mechanisms underlying oscillation have focused on processes requiring a rhythmic change in gene expression, which usually exhibit a periodicity of >10 min. Mechanisms that control oscillation with shorter periods (<10 min), presumably independent of gene expression changes, are poorly understood. Oscillatory pollen tube tip growth provides an excellent model to investigate such mechanisms. It is well established that ROP1, a Rho-like GTPase from plants, plays an essential role in polarized tip growth in pollen tubes. In this article, we demonstrate that tip-localized ROP1 GTPase activity oscillates in the same frequency with growth oscillation, and leads growth both spatially and temporally. Tip growth requires the coordinate action of two ROP1 downstream pathways that promote the accumulation of tip-localized Ca2+ and actin microfilaments (F-actin), respectively. We show that the ROP1 activity oscillates in a similar phase with the apical F-actin but apparently ahead of tip-localized Ca2+. Furthermore, our observations support the hypothesis that the oscillation of tip-localized ROP activity and ROP-dependent tip growth in pollen tubes is modulated by the two temporally coordinated downstream pathways, an early F-actin assembly pathway and a delayed Ca2+ gradient-forming pathway. To our knowledge, our report is the first to demonstrate the oscillation of Rho GTPase signaling, which may be a common mechanism underlying the oscillation of actin-dependent processes such as polar growth, cell movement, and chemotaxis.
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Affiliation(s)
- Jae-Ung Hwang
- College of Life Sciences, China Agricultural University, Beijing 100094, China
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46
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McGraw PN, Menzinger M. Flow-distributed oscillation, flow-velocity modulation, and resonance. Phys Rev E 2005; 72:027202. [PMID: 16196756 DOI: 10.1103/physreve.72.027202] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Indexed: 11/07/2022]
Abstract
We examine the effects of a periodically varying flow velocity on the standing- and traveling-wave patterns formed by the flow-distributed oscillation mechanism. In the kinematic (or diffusionless) limit, the phase fronts undergo a simple, spatiotemporally periodic longitudinal displacement. On the other hand, when the diffusion is significant, periodic modulation of the velocity can disrupt the wave pattern, giving rise in the downstream region to traveling waves whose frequency is a rational multiple of the velocity perturbation frequency. We observe frequency locking at ratios of 1:1, 2:1, and 3:1, depending on the amplitude and frequency of the velocity modulation. This phenomenon can be viewed as a novel, rather subtle type of resonant forcing.
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Affiliation(s)
- Patrick N McGraw
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6
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Yokota E, Tominaga M, Mabuchi I, Tsuji Y, Staiger CJ, Oiwa K, Shimmen T. Plant villin, lily P-135-ABP, possesses G-actin binding activity and accelerates the polymerization and depolymerization of actin in a Ca2+-sensitive manner. PLANT & CELL PHYSIOLOGY 2005; 46:1690-703. [PMID: 16100394 DOI: 10.1093/pcp/pci185] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
From germinating pollen of lily, two types of villins, P-115-ABP and P-135-ABP, have been identified biochemically. Ca(2+)-CaM-dependent actin-filament binding and bundling activities have been demonstrated for both villins previously. Here, we examined the effects of lily villins on the polymerization and depolymerization of actin. P-115-ABP and P-135-ABP present in a crude protein extract prepared from germinating pollen bound to a DNase I affinity column in a Ca(2+)-dependent manner. Purified P-135-ABP reduced the lag period that precedes actin filament polymerization from monomers in the presence of either Ca(2+) or Ca(2+)-CaM. These results indicated that P-135-ABP can form a complex with G-actin in the presence of Ca(2+) and this complex acts as a nucleus for polymerization of actin filaments. However, the nucleation activity of P-135-ABP is probably not relevant in vivo because the assembly of G-actin saturated with profilin, a situation that mimics conditions found in pollen, was not accelerated in the presence of P-135-ABP. P-135-ABP also enhanced the depolymerization of actin filaments during dilution-mediated disassembly. Growth from filament barbed ends in the presence of Ca(2+)-CaM was also prevented, consistent with filament capping activity. These results suggested that lily villin is involved not only in the arrangement of actin filaments into bundles in the basal and shank region of the pollen tube, but also in regulating and modulating actin dynamics through its capping and depolymerization (or fragmentation) activities in the apical region of the pollen tube, where there is a relatively high concentration of Ca(2+).
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Affiliation(s)
- Etsuo Yokota
- Department of Life Science, Graduate School of Life Science, University of Hyogo, Harima Science Park City, Kamigoricho, Akogun, Japan
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Monteiro D, Castanho Coelho P, Rodrigues C, Camacho L, Quader H, Malhó R. Modulation of endocytosis in pollen tube growth by phosphoinositides and phospholipids. PROTOPLASMA 2005; 226:31-8. [PMID: 16231099 DOI: 10.1007/s00709-005-0102-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2005] [Accepted: 03/30/2005] [Indexed: 05/04/2023]
Abstract
In plants, tip-growing cells represent an ideal system to investigate signal transduction mechanisms, and among those, pollen tubes are one of the favourite models. Many signalling pathways have been identified during germination and tip growth, namely, Ca2+, calmodulin, phosphoinositides, cyclic AMP, and GTPases. Not surprisingly, the apical secretory machinery, essential for tip growth, seems to be an intersection point for all these pathways. Recently, the phospholipid phosphatidic acid was also suggested to actively participate in the control of endo- and exocytosis and to interfere with the correct positioning of the actin cytoskeleton. Phosphatidic acid seems to act concertedly with the phosphoinositides phosphatidylinositol 4,5-bisphosphate and D-myo-inositol 1,4,5-trisphosphate. Here we review previous data and discuss additional evidence that these three molecules have a combined action modulating both the actin cytoskeleton and the apical secretory machinery. We further discuss how these findings can be integrated into a working model for pollen tube apical secretion that contemplates the existence of a rapid endocytosis mechanism.
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Affiliation(s)
- D Monteiro
- Instituto de Ciência Aplicada e Tecnologia, Faculdade de Ciências, Universidade de Lisboa, Lisboa, Portugal
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Cárdenas L, Lovy-Wheeler A, Wilsen KL, Hepler PK. Actin polymerization promotes the reversal of streaming in the apex of pollen tubes. ACTA ACUST UNITED AC 2005; 61:112-27. [PMID: 15849722 DOI: 10.1002/cm.20068] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Actin polymerization is important in the control of pollen tube growth. Thus, treatment of pollen tubes with low concentrations of latrunculin B (Lat-B), which inhibits actin polymerization, permits streaming but reversibly blocks oscillatory growth. In the current study, we employ Jasplakinolide (Jas), a sponge cyclodepsipeptide that stabilizes actin microfilaments and promotes polymerization. Uniquely, Jas (2 microM) blocks streaming in the shank of the tube, but induces the formation of a toroidal-shaped domain in the swollen apex, of which longitudinal optical sections exhibit circles of motion. The polarity of this rotary motion is identical to that of reverse fountain motility in control pollen tubes, with the forward direction occurring at the edge of the cell and the rearward direction in the cell interior. Support for the idea that actin polymerization in the apical domain contributes to the formation of this rotary motility activity derives from the appearance therein of aggregates and flared cables of F-actin, using immunofluorescence, and by the reduction in G-actin as indicated with fluorescent DNAse. In addition, Jas reduces the tip-focused Ca2+ gradient. However, the alkaline band appears in the swollen apex and is spatially localized with the reverse fountain streaming activity. Taken together, our results support the idea that actin polymerization promotes reversal of streaming in the apex of the lily pollen tube.
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Affiliation(s)
- Luis Cárdenas
- Biology Department, and the Plant Biology Graduate Program, Morrill Science Center, University of Massachusetts, Amherst, USA.
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Xu J, Brearley CA, Lin WH, Wang Y, Ye R, Mueller-Roeber B, Xu ZH, Xue HW. A role of Arabidopsis inositol polyphosphate kinase, AtIPK2alpha, in pollen germination and root growth. PLANT PHYSIOLOGY 2005; 137:94-103. [PMID: 15618435 PMCID: PMC548841 DOI: 10.1104/pp.104.045427] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2004] [Revised: 09/17/2004] [Accepted: 09/20/2004] [Indexed: 05/20/2023]
Abstract
Inositol polyphosphates, such as inositol trisphosphate, are pivotal intracellular signaling molecules in eukaryotic cells. In higher plants the mechanism for the regulation of the type and the level of these signaling molecules is poorly understood. In this study we investigate the physiological function of an Arabidopsis (Arabidopsis thaliana) gene encoding inositol polyphosphate kinase (AtIPK2alpha), which phosphorylates inositol 1,4,5-trisphosphate successively at the D-6 and D-3 positions, and inositol 1,3,4,5-tetrakisphosphate at D-6, resulting in the generation of inositol 1,3,4,5,6-pentakisphosphate. Semiquantitative reverse transcription-PCR and promoter-beta-glucuronidase reporter gene analyses showed that AtIPK2alpha is expressed in various tissues, including roots and root hairs, stem, leaf, pollen grains, pollen tubes, the flower stigma, and siliques. Transgenic Arabidopsis plants expressing the AtIPK2alpha antisense gene under its own promoter were generated. Analysis of several independent transformants exhibiting strong reduction in AtIPK2alpha transcript levels showed that both pollen germination and pollen tube growth were enhanced in the antisense lines compared to wild-type plants, especially in the presence of nonoptimal low Ca(2+) concentrations in the culture medium. Furthermore, root growth and root hair development were also stimulated in the antisense lines, in the presence of elevated external Ca(2+) concentration or upon the addition of EGTA. In addition, seed germination and early seedling growth was stimulated in the antisense lines. These observations suggest a general and important role of AtIPK2alpha, and hence inositol polyphosphate metabolism, in the regulation of plant growth most likely through the regulation of calcium signaling, consistent with the well-known function of inositol trisphosphate in the mobilization of intracellular calcium stores.
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Affiliation(s)
- Jun Xu
- National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Science, Chinese Academy of Sciences, 200032 Shanghai, China
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