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Tian H, Zhang H, Huang H, Zhang Y, Xue Y. Phase separation of S-RNase promotes self-incompatibility in Petunia hybrida. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2024; 66:986-1006. [PMID: 37963073 DOI: 10.1111/jipb.13584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 11/12/2023] [Indexed: 11/16/2023]
Abstract
Self-incompatibility (SI) is an intraspecific reproductive barrier widely present in angiosperms. The SI system with the broadest occurrence in angiosperms is based on an S-RNase linked to a cluster of multiple S-locus F-box (SLF) genes found in the Solanaceae, Plantaginaceae, Rosaceae, and Rutaceae. Recent studies reveal that non-self S-RNase is degraded by the Skip Cullin F-box (SCF)SLF-mediated ubiquitin-proteasome system in a collaborative manner in Petunia, but how self-RNase functions largely remains mysterious. Here, we show that S-RNases form S-RNase condensates (SRCs) in the self-pollen tube cytoplasm through phase separation and the disruption of SRC formation breaks SI in self-incompatible Petunia hybrida. We further find that the pistil SI factors of a small asparagine-rich protein HT-B and thioredoxin h together with a reduced state of the pollen tube all promote the expansion of SRCs, which then sequester several actin-binding proteins, including the actin polymerization factor PhABRACL, the actin polymerization activity of which is reduced by S-RNase in vitro. Meanwhile, we find that S-RNase variants lacking condensation ability fail to recruit PhABRACL and are unable to induce actin foci formation required for pollen tube growth inhibition. Taken together, our results demonstrate that phase separation of S-RNase promotes SI response in P. hybrida, revealing a new mode of S-RNase action.
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Affiliation(s)
- Huayang Tian
- The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, the Chinese Academy of Sciences, Beijing, 100101, China
- University of the Chinese Academy of Sciences, Beijing, 100049, China
| | - Hongkui Zhang
- University of the Chinese Academy of Sciences, Beijing, 100049, China
- Beijing Institute of Genomics, Chinese Academy of Sciences, National Center for Bioinformation, Beijing, 100101, China
| | - Huaqiu Huang
- The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, the Chinese Academy of Sciences, Beijing, 100101, China
| | - Yu'e Zhang
- The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, the Chinese Academy of Sciences, Beijing, 100101, China
| | - Yongbiao Xue
- The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, the Chinese Academy of Sciences, Beijing, 100101, China
- University of the Chinese Academy of Sciences, Beijing, 100049, China
- Beijing Institute of Genomics, Chinese Academy of Sciences, National Center for Bioinformation, Beijing, 100101, China
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2
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Zhang R, Xu Y, Yi R, Shen J, Huang S. Actin cytoskeleton in the control of vesicle transport, cytoplasmic organization, and pollen tube tip growth. PLANT PHYSIOLOGY 2023; 193:9-25. [PMID: 37002825 DOI: 10.1093/plphys/kiad203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 03/08/2023] [Accepted: 03/17/2023] [Indexed: 06/19/2023]
Abstract
Pollen tubes extend rapidly via tip growth. This process depends on a dynamic actin cytoskeleton, which has been implicated in controlling organelle movements, cytoplasmic streaming, vesicle trafficking, and cytoplasm organization in pollen tubes. In this update review, we describe the progress in understanding the organization and regulation of the actin cytoskeleton and the function of the actin cytoskeleton in controlling vesicle traffic and cytoplasmic organization in pollen tubes. We also discuss the interplay between ion gradients and the actin cytoskeleton that regulates the spatial arrangement and dynamics of actin filaments and the organization of the cytoplasm in pollen tubes. Finally, we describe several signaling components that regulate actin dynamics in pollen tubes.
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Affiliation(s)
- Ruihui Zhang
- National Key Laboratory of Crop Genetic Improvement, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Yanan Xu
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Ran Yi
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jiangfeng Shen
- 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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3
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Wang L, Lin Z, Carli J, Gladala‐Kostarz A, Davies JM, Franklin‐Tong VE, Bosch M. Depletion plays a pivotal role in self-incompatibility, revealing a link between cellular energy status, cytosolic acidification and actin remodelling in pollen tubes. THE NEW PHYTOLOGIST 2022; 236:1691-1707. [PMID: 35775998 PMCID: PMC9796540 DOI: 10.1111/nph.18350] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 06/15/2022] [Indexed: 06/08/2023]
Abstract
Self-incompatibility (SI) involves specific interactions during pollination to reject incompatible ('self') pollen, preventing inbreeding in angiosperms. A key event observed in pollen undergoing the Papaver rhoeas SI response is the formation of punctate F-actin foci. Pollen tube growth is heavily energy-dependent, yet ATP levels in pollen tubes have not been directly measured during SI. Here we used transgenic Arabidopsis lines expressing the Papaver pollen S-determinant to investigate a possible link between ATP levels, cytosolic pH ([pH]cyt ) and alterations to the actin cytoskeleton. We identify for the first time that SI triggers a rapid and significant ATP depletion in pollen tubes. Artificial depletion of ATP triggered cytosolic acidification and formation of actin aggregates. We also identify in vivo, evidence for a threshold [pH]cyt of 5.8 for actin foci formation. Imaging revealed that SI stimulates acidic cytosolic patches adjacent to the plasma membrane. In conclusion, this study provides evidence that ATP depletion plays a pivotal role in SI upstream of programmed cell death and reveals a link between the cellular energy status, cytosolic acidification and alterations to the actin cytoskeleton in regulating Papaver SI in pollen tubes.
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Affiliation(s)
- Ludi Wang
- Institute of Biological, Environmental and Rural Sciences (IBERS)Aberystwyth UniversityPlas GogerddanAberystwythSY23 3EEUK
| | - Zongcheng Lin
- Key Laboratory of Horticultural Plant BiologyHuazhong Agricultural UniversityWuhan430070China
| | - José Carli
- Institute of Biological, Environmental and Rural Sciences (IBERS)Aberystwyth UniversityPlas GogerddanAberystwythSY23 3EEUK
| | - Agnieszka Gladala‐Kostarz
- Institute of Biological, Environmental and Rural Sciences (IBERS)Aberystwyth UniversityPlas GogerddanAberystwythSY23 3EEUK
| | - Julia M. Davies
- Department of Plant SciencesUniversity of CambridgeCambridgeCB2 3EAUK
| | - Vernonica E. Franklin‐Tong
- School of Biosciences, College of Life and Environmental SciencesUniversity of BirminghamEdgbastonBirminghamB15 2TTUK
| | - Maurice Bosch
- Institute of Biological, Environmental and Rural Sciences (IBERS)Aberystwyth UniversityPlas GogerddanAberystwythSY23 3EEUK
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4
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Xu Y, Huang S. Control of the Actin Cytoskeleton Within Apical and Subapical Regions of Pollen Tubes. Front Cell Dev Biol 2020; 8:614821. [PMID: 33344460 PMCID: PMC7744591 DOI: 10.3389/fcell.2020.614821] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 11/13/2020] [Indexed: 01/07/2023] Open
Abstract
In flowering plants, sexual reproduction involves a double fertilization event, which is facilitated by the delivery of two non-motile sperm cells to the ovule by the pollen tube. Pollen tube growth occurs exclusively at the tip and is extremely rapid. It strictly depends on an intact actin cytoskeleton, and is therefore an excellent model for uncovering the molecular mechanisms underlying dynamic actin cytoskeleton remodeling. There has been a long-term debate about the organization and dynamics of actin filaments within the apical and subapical regions of pollen tube tips. By combining state-of-the-art live-cell imaging with the usage of mutants which lack different actin-binding proteins, our understanding of the origin, spatial organization, dynamics and regulation of actin filaments within the pollen tube tip has greatly improved. In this review article, we will summarize the progress made in this area.
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Affiliation(s)
| | - Shanjin Huang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
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5
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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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6
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Chen S, Jia J, Cheng L, Zhao P, Qi D, Yang W, Liu H, Dong X, Li X, Liu G. Transcriptomic Analysis Reveals a Comprehensive Calcium- and Phytohormone-Dominated Signaling Response in Leymus chinensis Self-Incompatibility. Int J Mol Sci 2019; 20:E2356. [PMID: 31085987 PMCID: PMC6539167 DOI: 10.3390/ijms20092356] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2019] [Revised: 05/09/2019] [Accepted: 05/09/2019] [Indexed: 12/31/2022] Open
Abstract
Sheepgrass (Leymus chinensis (Trin.) Tzvel.) is an economically and ecologically important forage in the grass family. Self-incompatibility (SI) limits its seed production due to the low seed-setting rate after self-pollination. However, investigations into the molecular mechanisms of sheepgrass SI are lacking. Therefore, microscopic observation of pollen germination and pollen tube growth, as well as transcriptomic analyses of pistils after self- and cross-pollination, were performed. The results indicated that pollen tube growth was rapidly inhibited from 10 to 30 min after self-pollination and subsequently stopped but preceded normally after cross-pollination. Time course comparative transcriptomics revealed different transcriptome dynamics between self- and cross-pollination. A pool of SI-related signaling genes and pathways was generated, including genes related to calcium (Ca2+) signaling, protein phosphorylation, plant hormone, reactive oxygen species (ROS), nitric oxide (NO), cytoskeleton, and programmed cell death (PCD). A putative SI response molecular model in sheepgrass was presented. The model shows that SI may trigger a comprehensive calcium- and phytohormone-dominated signaling cascade and activate PCD, which may explain the rapid inhibition of self-pollen tube growth as observed by cytological analyses. These results provided new insight into the molecular mechanisms of sheepgrass (grass family) SI.
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Affiliation(s)
- Shuangyan Chen
- Key Laboratory of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing 100093, China.
| | - Junting Jia
- Agro-biological Gene Research Center, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China.
| | - Liqin Cheng
- Key Laboratory of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing 100093, China.
| | - Pincang Zhao
- College of management science and engineering, Hebei University of Economics and Business, Shijiazhuang 050061, China.
| | - Dongmei Qi
- Key Laboratory of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing 100093, China.
| | - Weiguang Yang
- Key Laboratory of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing 100093, China.
| | - Hui Liu
- Key Laboratory of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing 100093, China.
| | - Xiaobing Dong
- Key Laboratory of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing 100093, China.
| | - Xiaoxia Li
- Key Laboratory of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing 100093, China.
| | - Gongshe Liu
- Key Laboratory of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing 100093, China.
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7
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Qian D, Xiang Y. Actin Cytoskeleton as Actor in Upstream and Downstream of Calcium Signaling in Plant Cells. Int J Mol Sci 2019; 20:ijms20061403. [PMID: 30897737 PMCID: PMC6471457 DOI: 10.3390/ijms20061403] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Revised: 03/14/2019] [Accepted: 03/15/2019] [Indexed: 01/04/2023] Open
Abstract
In plant cells, calcium (Ca2+) serves as a versatile intracellular messenger, participating in several fundamental and important biological processes. Recent studies have shown that the actin cytoskeleton is not only an upstream regulator of Ca2+ signaling, but also a downstream regulator. Ca2+ has been shown to regulates actin dynamics and rearrangements via different mechanisms in plants, and on this basis, the upstream signaling encoded within the Ca2+ transient can be decoded. Moreover, actin dynamics have also been proposed to act as an upstream of Ca2+, adjust Ca2+ oscillations, and establish cytosolic Ca2+ ([Ca2+]cyt) gradients in plant cells. In the current review, we focus on the advances in uncovering the relationship between the actin cytoskeleton and calcium in plant cells and summarize our current understanding of this relationship.
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Affiliation(s)
- Dong Qian
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
| | - Yun Xiang
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
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8
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Simultaneous imaging and functional studies reveal a tight correlation between calcium and actin networks. Proc Natl Acad Sci U S A 2018; 115:E2869-E2878. [PMID: 29507239 DOI: 10.1073/pnas.1711037115] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Tip-growing cells elongate in a highly polarized manner via focused secretion of flexible cell-wall material. Calcium has been implicated as a vital factor in regulating the deposition of cell-wall material. However, deciphering the molecular and mechanistic calcium targets in vivo has remained challenging. Here, we investigated intracellular calcium dynamics in the moss Physcomitrella patens, which provides a system with an abundant source of genetically identical tip-growing cells, excellent cytology, and a large molecular genetic tool kit. To visualize calcium we used a genetically encoded cytosolic FRET probe, revealing a fluctuating tipward gradient with a complex oscillatory profile. Wavelet analysis coupled with a signal-sifting algorithm enabled the quantitative comparison of the calcium behavior in cells where growth was inhibited mechanically, pharmacologically, or genetically. We found that cells with suppressed growth have calcium oscillatory profiles with longer frequencies, suggesting that there is a feedback between the calcium gradient and growth. To investigate the mechanistic basis for this feedback we simultaneously imaged cytosolic calcium and actin, which has been shown to be essential for tip growth. We found that high cytosolic calcium promotes disassembly of a tip-focused actin spot, while low calcium promotes assembly. In support of this, abolishing the calcium gradient resulted in dramatic actin accumulation at the tip. Together these data demonstrate that tipward calcium is quantitatively linked to actin accumulation in vivo and that the moss P. patens provides a powerful system to uncover mechanistic links between calcium, actin, and growth.
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9
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Isolation of Actin and Actin-Binding Proteins. Methods Mol Biol 2016. [PMID: 27730620 DOI: 10.1007/978-1-4939-6533-5_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Actin-binding proteins mediate and regulate the dynamics of actin and the organization of highly ordered structures of F-actin. Villin is generally expressed in plant cells and is associated with G-actin or F-actin dependent on Ca2+ concentrations. Using a DNase I affinity column chromatography approach, the villin and the G-actin can be isolated from plant material. An outline of this method including the preparation of crude protein extract from plant material, its application on the affinity column, and the successive elution of villin with a solution containing EGTA and then of G-actin with denatured reagents is presented.
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10
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Zhao LJ, Yuan HM, Guo WD, Yang CP. Digital Gene Expression Analysis of Populus simonii × P. nigra Pollen Germination and Tube Growth. FRONTIERS IN PLANT SCIENCE 2016; 7:825. [PMID: 27379121 PMCID: PMC4908133 DOI: 10.3389/fpls.2016.00825] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 05/26/2016] [Indexed: 05/27/2023]
Abstract
Pollen tubes are an ideal model for the study of cell growth and morphogenesis because of their extreme elongation without cell division; however, the genetic basis of pollen germination and tube growth remains largely unknown. Using the Illumina/Solexa digital gene expression system, we identified 13,017 genes (representing 28.3% of the unigenes on the reference genes) at three stages, including mature pollen, hydrated pollen, and pollen tubes of Populus simonii × P. nigra. Comprehensive analysis of P. simonii × P. nigra pollen revealed dynamic changes in the transcriptome during pollen germination and pollen tube growth (PTG). Gene ontology analysis of differentially expressed genes showed that genes involved in functional categories such as catalytic activity, binding, transporter activity, and enzyme regulator activity were overrepresented during pollen germination and PTG. Some highly dynamic genes involved in pollen germination and PTG were detected by clustering analysis. Genes related to some key pathways such as the mitogen-activated protein kinase signaling pathway, regulation of the actin cytoskeleton, calcium signaling, and ubiquitin-mediated proteolysis were significantly changed during pollen germination and PTG. These data provide comprehensive molecular information toward further understanding molecular mechanisms underlying pollen germination and PTG.
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Affiliation(s)
- Li-Juan Zhao
- State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry UniversityHarbin, China
- Department of Crop Molecular Breeding, Crop Breeding Institute, Heilongjiang Academy of Agricultural SciencesHarbin, China
| | - Hong-Mei Yuan
- Medical Plant Research Center, Economic Crop Institute, Heilongjiang Academy of Agricultural SciencesHarbin, China
| | - Wen-Dong Guo
- Biotechnology Research Center, Institute of Natural Resources and Ecology, Heilongjiang Academy of SciencesHarbin, China
| | - Chuan-Ping Yang
- State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry UniversityHarbin, China
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11
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Zhang M, Zhang R, Qu X, Huang S. Arabidopsis FIM5 decorates apical actin filaments and regulates their organization in the pollen tube. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:3407-17. [PMID: 27117336 PMCID: PMC4892729 DOI: 10.1093/jxb/erw160] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The actin cytoskeleton is increasingly recognized as a major regulator of pollen tube growth. Actin filaments have distinct distribution patterns and dynamic properties within different regions of the pollen tube. Apical actin filaments are highly dynamic and crucial for pollen tube growth. However, how apical actin filaments are generated and properly constructed remains an open question. Here we showed that Arabidopsis fimbrin5 (FIM5) decorates filamentous structures throughout the entire tube but is apically concentrated. Apical actin structures are disorganized to different degrees in the pollen tubes of fim5 loss-of-function mutants. Further observations suggest that apical actin structures are not constructed properly because apical actin filaments cannot be maintained at the cortex of fim5 pollen tubes. Actin filaments appeared to be more curved in fim5 pollen tubes and this was confirmed by measurements showing that the convolutedness and the rate of change of convolutedness of actin filaments was significantly increased in fim5 pollen tubes. This suggests that the rigidity of the actin filaments may be compromised in fim5 pollen tubes. Further, the apical cell wall composition is altered, implying that tip-directed vesicle trafficking events are impaired in fim5 pollen tubes. Thus, we found that FIM5 decorates apical actin filaments and regulates their organization in order to drive polarized pollen tube growth.
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Affiliation(s)
- Meng Zhang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany Chinese Academy of Sciences, Beijing 100093 China University of Chinese Academy of Sciences, Beijing 100049 China
| | - Ruihui Zhang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany Chinese Academy of Sciences, Beijing 100093 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 Tsinghua-Peking Joint Center for Life Sciences, Beijing 100084 China
| | - Shanjin Huang
- 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 National Center for Plant Gene Research, Beijing 100101 China
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12
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Qian D, Nan Q, Yang Y, Li H, Zhou Y, Zhu J, Bai Q, Zhang P, An L, Xiang Y. Gelsolin-Like Domain 3 Plays Vital Roles in Regulating the Activities of the Lily Villin/Gelsolin/Fragmin Superfamily. PLoS One 2015; 10:e0143174. [PMID: 26587673 PMCID: PMC4654503 DOI: 10.1371/journal.pone.0143174] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 11/02/2015] [Indexed: 02/08/2023] Open
Abstract
The villin/gelsolin/fragmin superfamily is a major group of Ca2+-dependent actin-binding proteins (ABPs) involved in various cellular processes. Members of this superfamily typically possess three or six tandem gelsolin-like (G) domains, and each domain plays a distinct role in actin filament dynamics. Although the activities of most G domains have been characterized, the biochemical function of the G3 domain remains poorly understood. In this study, we carefully compared the detailed biochemical activities of ABP29 (a new member of this family that contains the G1-G2 domains of lily ABP135) and ABP135G1-G3 (which contains the G1-G3 domains of lily ABP135). In the presence of high Ca2+ levels in vitro (200 and 10 μM), ABP135G1-G3 exhibited greater actin severing and/or depolymerization and nucleating activities than ABP29, and these proteins had similar actin capping activities. However, in the presence of low levels of Ca2+ (41 nM), ABP135G1-G3 had a weaker capping activity than ABP29. In addition, ABP29 inhibited F-actin depolymerization, as shown by dilution-mediated depolymerization assay, differing from the typical superfamily proteins. In contrast, ABP135G1-G3 accelerated F-actin depolymerization. All of these results demonstrate that the G3 domain plays specific roles in regulating the activities of the lily villin/gelsolin/fragmin superfamily proteins.
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Affiliation(s)
- Dong Qian
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Qiong Nan
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Yueming Yang
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Hui Li
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Yuelong Zhou
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Jingen Zhu
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Qifeng Bai
- College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, China
| | - Pan Zhang
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Lizhe An
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Yun Xiang
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
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13
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Li L, Li Y, Wang NN, Li Y, Lu R, Li XB. Cotton LIM domain-containing protein GhPLIM1 is specifically expressed in anthers and participates in modulating F-actin. PLANT BIOLOGY (STUTTGART, GERMANY) 2015; 17:528-534. [PMID: 25294521 DOI: 10.1111/plb.12243] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 06/23/2014] [Indexed: 06/03/2023]
Abstract
As one form of actin binding protein (ABP), LIM domain protein can trigger the formation of actin bundles during plant growth and development. In this study, a cDNA (designated GhPLIM1) encoding a LIM domain protein with 216 amino acid residues was identified from a cotton flower cDNA library. Quantitative RT-PCR indicated that GhPLIM1 is specifically expressed in cotton anthers, and its expression levels are regulated during anther development of cotton. GhPLIM1:eGFP transformed cotton cells display a distributed network of eGFP fluorescence, suggesting that GhPLIM1 protein is mainly localised to the cell cytoskeleton. In vitro high-speed co-sedimentation and low co-sedimentation assays indicate that GhPLIM1 protein not only directly binds actin filaments but also bundles F-actin. Further biochemical experiments verified that GhPLIM1 protein can protect F-actin against depolymerisation by Lat B. Thus, our data demonstrate that GhPLIM1 functions as an actin binding protein (ABP) in modulating actin filaments in vitro, suggesting that GhPLIM1 may be involved in regulating the actin cytoskeleton required for pollen development in cotton.
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Affiliation(s)
- L Li
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, China
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14
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Hepler PK, Winship LJ. The pollen tube clear zone: clues to the mechanism of polarized growth. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2015; 57:79-92. [PMID: 25431342 DOI: 10.1111/jipb.12315] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 11/24/2014] [Indexed: 05/08/2023]
Abstract
Pollen tubes usually exhibit a prominent region at their apex called the "clear zone" because it lacks light refracting amyloplasts. A robust, long clear zone often associates with fast growing pollen tubes, and thus serves as an indicator of pollen tube health. Nevertheless we do not understand how it arises or how it is maintained. Here we review the structure of the clear zone, and attempt to explain the factors that contribute to its formation. While amyloplasts and vacuolar elements are excluded from the clear zone, virtually all other organelles are present including secretory vesicles, mitochondria, Golgi dictyosomes, and the endoplasmic reticulum (ER). Secretory vesicles aggregate into an inverted cone appressed against the apical plasma membrane. ER elements move nearly to the extreme apex, whereas mitochondria and Golgi dictyosomes move less far forward. The cortical actin fringe assumes a central position in the control of clear zone formation and maintenance, given its role in generating cytoplasmic streaming. Other likely factors include the tip-focused calcium gradient, the apical pH gradient, the influx of water, and a host of signaling factors (small G-proteins). We think that the clear zone is an emergent property that depends on the interaction of several factors crucial for polarized growth.
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Affiliation(s)
- Peter K Hepler
- Biology Department, University of Massachusetts, Amherst, Massachusetts, 01003, USA
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15
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Cai G, Parrotta L, Cresti M. Organelle trafficking, the cytoskeleton, and pollen tube growth. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2015; 57:63-78. [PMID: 25263392 DOI: 10.1111/jipb.12289] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 09/23/2014] [Indexed: 06/03/2023]
Abstract
The pollen tube is fundamental for the reproduction of seed plants. Characteristically, it grows relatively quickly and uni-directionally ("polarized growth") to extend the male gametophyte to reach the female gametophyte. The pollen tube forms a channel through which the sperm cells move so that they can reach their targets in the ovule. To grow quickly and directionally, the pollen tube requires an intense movement of organelles and vesicles that allows the cell's contents to be distributed to sustain the growth rate. While the various organelles distribute more or less uniformly within the pollen tube, Golgi-released secretory vesicles accumulate massively at the pollen tube apex, that is, the growing region. This intense movement of organelles and vesicles is dependent on the dynamics of the cytoskeleton, which reorganizes differentially in response to external signals and coordinates membrane trafficking with the growth rate of pollen tubes.
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Affiliation(s)
- Giampiero Cai
- Department of Life Sciences, University of Siena, Siena, 53100, Italy
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16
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Huang S, Qu X, Zhang R. Plant villins: versatile actin regulatory proteins. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2015; 57:40-9. [PMID: 25294278 DOI: 10.1111/jipb.12293] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2014] [Accepted: 10/01/2014] [Indexed: 05/03/2023]
Abstract
Regulation of actin dynamics is a central theme in cell biology that is important for different aspects of cell physiology. Villin, a member of the villin/gelsolin/fragmin superfamily of proteins, is an important regulator of actin. Villins contain six gelsolin homology domains (G1-G6) and an extra headpiece domain. In contrast to their mammalian counterparts, plant villins are expressed widely, implying that plant villins play a more general role in regulating actin dynamics. Some plant villins have a defined role in modifying actin dynamics in the pollen tube; most of their in vivo activities remain to be ascertained. Recently, our understanding of the functions and mechanisms of action for plant villins has progressed rapidly, primarily due to the advent of Arabidopsis thaliana genetic approaches and imaging capabilities that can visualize actin dynamics at the single filament level in vitro and in living plant cells. In this review, we focus on discussing the biochemical activities and modes of regulation of plant villins. Here, we present current understanding of the functions of plant villins. Finally, we highlight some of the key unanswered questions regarding the functions and regulation of plant villins for future research.
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Affiliation(s)
- Shanjin Huang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, the Chinese Academy of Sciences, Beijing, 100093, China
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17
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Roldán JA, Rojas HJ, Goldraij A. In vitro inhibition of incompatible pollen tubes in Nicotiana alata involves the uncoupling of the F-actin cytoskeleton and the endomembrane trafficking system. PROTOPLASMA 2015; 252:63-75. [PMID: 24841893 DOI: 10.1007/s00709-014-0658-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 05/07/2014] [Indexed: 06/03/2023]
Abstract
In the S-RNase-based self-incompatibility system, subcellular events occurring in the apical region of incompatible pollen tubes during the pollen rejection process are poorly understood. F-actin dynamics and endomembrane trafficking are crucial for polar growth, which is temporally and spatially controlled in the tip region of pollen tubes. Thus, we developed a simple in vitro assay to study the changes in the F-actin cytoskeleton and the endomembrane system at the apical region of incompatible pollen tubes in Nicotiana alata. Growth but not germination of pollen tubes of S c₁₀-, S₇₀-, and S₇₅-haplotypes was selectively inhibited by style extracts carrying the same haplotypes. Pollen F-actin cytoskeleton and endomembrane system, visualized by fluorescent markers, were normal during the initial 60 min of pollen culture in the presence of compatible and incompatible style extracts. Additional culture resulted in complete growth arrest and critical alterations in the integrity of the F-actin cytoskeleton and the endomembrane system of incompatible pollen tubes. The F-actin ring and the V-shaped zone disappeared from the apical region, while distorted F-actin cables and progressive formation of membrane aggregates evolved in the subapical region and the shank. The vacuolar network of incompatible pollen tubes invaded the tip region, but vacuolar membrane integrity remained mostly unaffected. The polar growth machinery of incompatible pollen tubes was uncoupled, as evidenced by the severe disruption of colocalization between the F-actin cytoskeleton and the endomembrane compartments. A model of pollen rejection integrating the main subcellular events occurring in incompatible pollen is discussed.
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Affiliation(s)
- Juan A Roldán
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC-CONICET), Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, X5000HUA, Córdoba, Argentina
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18
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Onelli E, Idilli AI, Moscatelli A. Emerging roles for microtubules in angiosperm pollen tube growth highlight new research cues. FRONTIERS IN PLANT SCIENCE 2015; 6:51. [PMID: 25713579 PMCID: PMC4322846 DOI: 10.3389/fpls.2015.00051] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 01/20/2015] [Indexed: 05/21/2023]
Abstract
In plants, actin filaments have an important role in organelle movement and cytoplasmic streaming. Otherwise microtubules (MTs) have a role in restricting organelles to specific areas of the cell and in maintaining organelle morphology. In somatic plant cells, MTs also participate in cell division and morphogenesis, allowing cells to take their definitive shape in order to perform specific functions. In the latter case, MTs influence assembly of the cell wall, controlling the delivery of enzymes involved in cellulose synthesis and of wall modulation material to the proper sites. In angiosperm pollen tubes, organelle movement is generally attributed to the acto-myosin system, the main role of which is in distributing organelles in the cytoplasm and in carrying secretory vesicles to the apex for polarized growth. Recent data on membrane trafficking suggests a role of MTs in fine delivery and repositioning of vesicles to sustain pollen tube growth. This review examines the role of MTs in secretion and endocytosis, highlighting new research cues regarding cell wall construction and pollen tube-pistil crosstalk, that help unravel the role of MTs in polarized growth.
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Affiliation(s)
| | - Aurora I. Idilli
- Institute of Biophysics, National Research Council and Fondazione Bruno Kessler, Trento, Italy
| | - Alessandra Moscatelli
- Department of Biosciences, University of Milan, Milan, Italy
- *Correspondence: Alessandra Moscatelli, Department of Biosciences, University of Milan, Via Celoria, 26, 20113 Milano, Italy e-mail:
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Polyamines are common players in different facets of plant programmed cell death. Amino Acids 2014; 47:27-44. [PMID: 25399055 DOI: 10.1007/s00726-014-1865-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 10/29/2014] [Indexed: 01/16/2023]
Abstract
Programmed cell death (PCD) is a process that occurs throughout the life span of every plant life, from initial germination of the seed to the senescence of the plant. It is a normal physiological milestone during the plant's developmental process, but it can also be induced by external factors, including a variety of environmental stresses and as a response to pathogen infections. Changes in the morphology of the nucleus is one of the most noticeable during PCD but all the components of the plant cell (cytoplasm, cytoskeleton and organelles) are involved in this fascinating process. To date, relatively little is known about PCD in plants, but several factors, among which polyamines (PAs) and plant growth regulators, have been shown to play an important role in the initiation and regulation of the process. The role of PAs in plant PCD appears to be multifaceted acting in some instances as pro-survival molecules, whereas in others seem to be implicated in accelerating PCD. The molecular mechanism is still under study. Here we present some PCD plant models, focusing on the role of the enzyme responsible for PA conjugation to proteins: transglutaminase (TGase), an enzyme linked with the process of PCD also in some animal models. The role of PAs and plant TGase in the senescence and PCD in flowers, leaf and the self-incompatibility of pollen will be discussed and examined in depth.
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20
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Self-incompatibility in Papaver: advances in integrating the signalling network. Biochem Soc Trans 2014; 42:370-6. [DOI: 10.1042/bst20130248] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Self-fertilization, which results in reduced fitness of offspring, is a common problem in hermaphrodite angiosperms. To prevent this, many plants utilize SI (self-incompatibility), which is determined by the multi-allelic S-locus, that allows discrimination between self (incompatible) and non-self (compatible) pollen by the pistil. In poppy (Papaver rhoeas), the pistil S-determinant (PrsS) is a small secreted protein which interacts with the pollen S-determinant PrpS, a ~20 kDa novel transmembrane protein. Interaction of matching pollen and pistil S-determinants results in self-recognition, initiating a Ca2+-dependent signalling network in incompatible pollen. This triggers several downstream events, including alterations to the cytoskeleton, phosphorylation of sPPases (soluble inorganic pyrophosphatases) and an MAPK (mitogen-activated protein kinase), increases in ROS (reactive oxygen species) and nitric oxide (NO), and activation of several caspase-like activities. This results in the inhibition of pollen tube growth, prevention of self-fertilization and ultimately PCD (programmed cell death) in incompatible pollen. The present review focuses on our current understanding of the integration of these signals with their targets in the SI/PCD network. We also discuss our recent functional expression of PrpS in Arabidopsis thaliana pollen.
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Wilkins KA, Poulter NS, Franklin-Tong VE. Taking one for the team: self-recognition and cell suicide in pollen. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:1331-42. [PMID: 24449385 DOI: 10.1093/jxb/ert468] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Self-incompatibility (SI) is an important genetically controlled mechanism used by many angiosperms to prevent self-fertilization and inbreeding. A multiallelic S-locus allows discrimination between 'self' (incompatible) pollen from 'nonself' pollen at the pistil. Interaction of matching pollen and pistil S-determinants allows 'self' recognition and triggers rejection of incompatible pollen. The S-determinants for Papaver rhoeas (poppy) are PrsS and PrpS. PrsS is a small secreted protein that acts as a signalling ligand to interact with its cognate pollen S-determinant PrpS, a small novel transmembrane protein. Interaction of PrsS with incompatible pollen stimulates increases in cytosolic free Ca(2+) and involves influx of Ca(2+) and K(+). Data implicate involvement of reactive oxygen species and nitric oxide signalling in the SI response. Downstream targets include the cytoskeleton, a soluble inorganic pyrophosphatase, Pr-p26.1, and a MAP kinase, PrMPK9-1. A major focus for SI-induced signalling is to initiate programmed cell death (PCD). In this review we provide an overview of our understanding of SI, with focus on how the signals and components are integrated, in particular, how reactive oxygen species, nitric oxide, and the actin cytoskeleton feed into a PCD network. We also discuss our recent functional expression of PrpS in Arabidopsis thaliana pollen in the context of understanding how PCD signalling systems may have evolved.
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Affiliation(s)
- Katie A Wilkins
- School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
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22
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Jiang X, Gao Y, Zhou H, Chen J, Wu J, Zhang S. Apoplastic calmodulin promotes self-incompatibility pollen tube growth by enhancing calcium influx and reactive oxygen species concentration in Pyrus pyrifolia. PLANT CELL REPORTS 2014; 33:255-63. [PMID: 24145911 DOI: 10.1007/s00299-013-1526-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2013] [Revised: 10/03/2013] [Accepted: 10/09/2013] [Indexed: 05/17/2023]
Abstract
Calmodulin (CaM) has been associated with various physiological and developmental processes in plants, including pollen tube growth. In this study, we showed that CaM regulated the pear pollen tube growth in a concentration-dependent bi-phasic response. Using a whole-cell patch-clamp configuration, we showed that apoplastic CaM induced a hyperpolarization-activated calcium ion (Ca²⁺) current, and anti-CaM largely inhibited this type of Ca²⁺ current. Moreover, upon anti-CaM treatment, the reactive oxygen species (ROS) concentration decreased and actin filaments depolymerized in the pollen tube. Interestingly, CaM could partially rescue the inhibition of self-incompatible pear pollen tube growth. This phenotype could be mediated by CaM-enhanced pollen plasma membrane Ca²⁺ current, tip-localized ROS concentration and stabilized actin filaments. These data indicated that Ca²⁺, ROS and actin filaments were involved with CaM in regulating pollen tube growth and provide a potential way for overcoming pear self-incompatibility.
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Affiliation(s)
- Xueting Jiang
- College of Horticulture, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, No 6. Tongwei Road, Nanjing, 210095, China
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23
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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: 78] [Impact Index Per Article: 7.8] [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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24
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Guo Z, Stephenson R, Qiu J, Zheng S, Luo ZQ. A Legionella effector modulates host cytoskeletal structure by inhibiting actin polymerization. Microbes Infect 2013; 16:225-36. [PMID: 24286927 DOI: 10.1016/j.micinf.2013.11.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 11/18/2013] [Accepted: 11/18/2013] [Indexed: 12/21/2022]
Abstract
Successful infection by the opportunistic pathogen Legionella pneumophila requires the collective activity of hundreds of virulence proteins delivered into the host cell by the Dot/Icm type IV secretion system. These virulence proteins, also called effectors modulate distinct host cellular processes to create a membrane-bound niche called the Legionella containing vacuole (LCV) supportive of bacterial growth. We found that Ceg14 (Lpg0437), a Dot/Icm substrate is toxic to yeast and such toxicity can be alleviated by overexpression of profilin, a protein involved in cytoskeletal structure in eukaryotes. We further showed that mutations in profilin affect actin binding but not other functions such as interactions with poly-l-proline or phosphatidylinositol, abolish its suppressor activity. Consistent with the fact the profilin suppresses its toxicity, expression of Ceg14 but not its non-toxic mutants in yeast affects actin distribution and budding of daughter cells. Although Ceg14 does not detectably interact with profilin, it co-sediments with filamentous actin and inhibits actin polymerization, causing the accumulation of short actin filaments. Together with earlier studies, these results reveal that multiple L. pneumophila effectors target components of the host cytoskeleton.
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Affiliation(s)
- Zhenhua Guo
- State Key Laboratory of Agrobiotechnology, Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, and College of Veterinary Medicine, China Agricultural University, Beijing 100193, China; Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Robert Stephenson
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Jiazhang Qiu
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Shijun Zheng
- State Key Laboratory of Agrobiotechnology, Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, and College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Zhao-Qing Luo
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
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25
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Ghoshdastider U, Popp D, Burtnick LD, Robinson RC. The expanding superfamily of gelsolin homology domain proteins. Cytoskeleton (Hoboken) 2013; 70:775-95. [DOI: 10.1002/cm.21149] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 10/11/2013] [Accepted: 10/02/2013] [Indexed: 12/29/2022]
Affiliation(s)
- Umesh Ghoshdastider
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science; Technology and Research); Biopolis 138673 Singapore
| | - David Popp
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science; Technology and Research); Biopolis 138673 Singapore
| | - Leslie D. Burtnick
- Department of Chemistry and Centre for Blood Research; Life Sciences Institute; University of British Columbia; Vancouver British Columbia V6T 1Z1 Canada
| | - Robert C. Robinson
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science; Technology and Research); Biopolis 138673 Singapore
- Department of Biochemistry; National University of Singapore; Singapore 117597 Singapore
- School of Biological Sciences; Nanyang Technological University; Singapore 637551 Singapore
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Cao LJ, Zhao MM, Liu C, Dong HJ, Li WC, Ren HY. LlSR28 is involved in pollen germination by affecting filamentous actin dynamics. MOLECULAR PLANT 2013; 6:1163-1175. [PMID: 23741063 DOI: 10.1093/mp/sst097] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Alternative splicing plays important roles in gene regulation and contributes to protein complexity. Previous studies suggest that alternative splicing exists in members of the villin/gelsolin/fragmin superfamily. In this study, a serine/argine-rich (SR) protein cDNA with 28 kDa protein (LlSR28) was isolated from a lily (Lilium longiflorum) expression library. Protein domain analysis showed that LlSR28 had similar structures to Arabidopsis SR45 (AtSR45), and LlSR28 could complement the phenotype of loss of AtSR45 function. Therefore, overexpression of LlSR28 and AtSR45 mutant (atsr45-1) were used in the following experiments. Overexpression of LlSR28 in Arabidopsis completely inhibited pollen germination. In contrast, the pollen germination of atsr45-1 was earlier than that of wild-type. In addition, pollen of atsr45-1 contained less F-actin at the corresponding hydration stage during pollen germination compared to that of wild-type. Alternative splicing analysis showed that Arabidopsis villin1 (AtVLN1) transcript encoding the full-length protein was increased, and that encoding the truncated protein was decreased in atst45-1. Moreover, the mRNA expression level of other actin-binding proteins (ABPs) abundant in Arabidopsis pollen was also changed in atsr45-1. In conclusion, we hypothesize that LlSR28 alters F-actin dynamics probably through its alternative splicing activities to affect directly or indirectly the alternative splicing of AtVLN1 and the expression of different ABPs, which then affects the pollen germination.
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Affiliation(s)
- Li-Juan Cao
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Science, Beijing Normal University, Beijing 100875, China
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Shi M, Xie Y, Zheng Y, Wang J, Su Y, Yang Q, Huang S. Oryza sativa actin-interacting protein 1 is required for rice growth by promoting actin turnover. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 73:747-60. [PMID: 23134061 DOI: 10.1111/tpj.12065] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Revised: 10/18/2012] [Accepted: 11/01/2012] [Indexed: 05/03/2023]
Abstract
Rapid actin turnover is essential for numerous actin-based processes. However, how it is precisely regulated remains poorly understood. Actin-interacting protein 1 (AIP1) has been shown to be an important factor by acting coordinately with actin-depolymerizing factor (ADF)/cofilin in promoting actin depolymerization, the rate-limiting factor in actin turnover. However, the molecular mechanism by which AIP1 promotes actin turnover remains largely unknown in plants. Here, we provide a demonstration that AIP1 promotes actin turnover, which is required for optimal growth of rice plants. Specific down-regulation of OsAIP1 increased the level of filamentous actin and reduced actin turnover, whereas over-expression of OsAIP1 induced fragmentation and depolymerization of actin filaments and enhanced actin turnover. In vitro biochemical characterization showed that, although OsAIP1 alone does not affect actin dynamics, it enhances ADF-mediated actin depolymerization. It also caps the filament barbed end in the presence of ADF, but the capping activity is not required for their coordinated action. Real-time visualization of single filament dynamics showed that OsAIP1 enhanced ADF-mediated severing and dissociation of pointed end subunits. Consistent with this, the filament severing frequency and subunit off-rate were enhanced in OsAIP1 over-expressors but decreased in RNAi protoplasts. Importantly, OsAIP1 acts coordinately with ADF and profilin to induce massive net actin depolymerization, indicating that AIP1 plays a major role in the turnover of actin, which is required to optimize F-actin levels in plants.
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Affiliation(s)
- Meng Shi
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
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Poulter NS, Bosch M, Franklin-Tong VE. Proteins implicated in mediating self-incompatibility-induced alterations to the actin cytoskeleton of Papaver pollen. ANNALS OF BOTANY 2011; 108:659-75. [PMID: 21320881 PMCID: PMC3170148 DOI: 10.1093/aob/mcr022] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Accepted: 01/04/2011] [Indexed: 05/20/2023]
Abstract
BACKGROUND AND AIMS Sexual reproduction in angiosperms involves a network of signalling and interactions between pollen and pistil. To promote out-breeding, an additional layer of interactions, involving self-incompatibility (SI), is used to prevent self-fertilization. SI is generally controlled by the S-locus, and comprises allelic pollen and pistil S-determinants. This provides the basis of recognition, and consequent rejection, of incompatible pollen. In Papaver rhoeas, SI involves interaction of pistil PrsS and pollen PrpS, triggering a Ca(2+)-dependent signalling network. This results in rapid and distinctive alterations to both the actin and microtubule cytoskeleton being triggered in 'self' pollen. Some of these alterations are implicated in mediating programmed cell death, involving activation of several caspase-like proteases. SCOPE Here we review and discuss our current understanding of the cytoskeletal alterations induced in incompatible pollen during SI and their relationship with programmed cell death. We focus on data relating to the formation of F-actin punctate foci, which have, to date, not been well characterized. The identification of two actin-binding proteins that interact with these structures are reviewed. Using an approach that enriched for F-actin from SI-induced pollen tubes using affinity purification followed by mass spectrometry, further proteins were identified as putative interactors with the F-actin foci in an SI situation. KEY RESULTS Previously two important actin-binding proteins, CAP and ADF, had been identified whose localization altered with SI, both showing co-localization with the F-actin punctate foci based on immunolocalization studies. Further analysis has identified differences between proteins associated with F-actin from SI-induced pollen samples and those associated with F-actin in untreated pollen. This provides candidate proteins implicated in either the formation or stabilization of the punctate actin structures formed during SI. CONCLUSIONS This review brings together for the first time, our current understanding of proteins and events involved in SI-induced signalling to the actin cytoskeleton in incompatible Papaver pollen.
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Bou Daher F, Geitmann A. Actin is Involved in Pollen Tube Tropism Through Redefining the Spatial Targeting of Secretory Vesicles. Traffic 2011; 12:1537-51. [DOI: 10.1111/j.1600-0854.2011.01256.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Smertenko A, Franklin-Tong VE. Organisation and regulation of the cytoskeleton in plant programmed cell death. Cell Death Differ 2011; 18:1263-70. [PMID: 21566662 PMCID: PMC3172095 DOI: 10.1038/cdd.2011.39] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Revised: 03/15/2011] [Accepted: 03/16/2011] [Indexed: 12/26/2022] Open
Abstract
Programmed cell death (PCD) involves precise integration of cellular responses to extracellular and intracellular signals during both stress and development. In recent years much progress in our understanding of the components involved in PCD in plants has been made. Signalling to PCD results in major reorganisation of cellular components. The plant cytoskeleton is known to play a major role in cellular organisation, and reorganization and alterations in its dynamics is a well known consequence of signalling. There are considerable data that the plant cytoskeleton is reorganised in response to PCD, with remodelling of both microtubules and microfilaments taking place. In the majority of cases, the microtubule network depolymerises, whereas remodelling of microfilaments can follow two scenarios, either being depolymerised and then forming stable foci, or forming distinct bundles and then depolymerising. Evidence is accumulating that demonstrate that these cytoskeletal alterations are not just a consequence of signals mediating PCD, but that they also may have an active role in the initiation and regulation of PCD. Here we review key data from higher plant model systems on the roles of the actin filaments and microtubules during PCD and discuss proteins potentially implicated in regulating these alterations.
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Affiliation(s)
- A Smertenko
- School of Biological and Biomedical Sciences, Durham University, Durham, DH1 3LE, UK
| | - V E Franklin-Tong
- School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, UK
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Chen C, Zhang Y, Zhu L, Yuan M. The actin cytoskeleton is involved in the regulation of the plasmodesmal size exclusion limit. PLANT SIGNALING & BEHAVIOR 2010; 5:1663-1665. [PMID: 21150300 PMCID: PMC3115129 DOI: 10.4161/psb.5.12.14018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Accepted: 10/26/2010] [Indexed: 05/29/2023]
Abstract
Plasmodesmata (PD) are the communication channels which allow the trafficking of macromolecules between neighboring cells. Such cell-to-cell movement of macromolecules is regulated during plant growth and development; however, little is known about the regulation mechanism of PD size exclusion limit (SEL). Plant viral movement proteins (MPs) enhance the invasion of viruses from cell to cell by increasing the SEL of the PD and are therefore a powerful means for the study of the plasmodesmal regulation mechanisms. In a recent study, we reported that the actin cytoskeleton is involved in the increase of the PD SEL induced by MPs. Microinjection experiments demonstrated that actin depolymerization was required for the Cucumber mosaic virus (CMV) MP-induced increase in the PD SEL. In vitro experiments showed that CMV MP severs actin filaments (F-actin). Furthermore, through the analyses of two CMV MP mutants, we demonstrated that the F-actin severing ability of CMV MP was required to increase the PD SEL. These results are similar to what has been found in Tobacco mosaic virus MP. Thus, our data suggests that actin dynamics may participate in the regulations of the PD SEL.
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Affiliation(s)
- Cheng Chen
- State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing, China
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Blanchoin L, Boujemaa-Paterski R, Henty JL, Khurana P, Staiger CJ. Actin dynamics in plant cells: a team effort from multiple proteins orchestrates this very fast-paced game. CURRENT OPINION IN PLANT BIOLOGY 2010; 13:714-23. [PMID: 20970372 DOI: 10.1016/j.pbi.2010.09.013] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 08/27/2010] [Accepted: 09/23/2010] [Indexed: 05/21/2023]
Abstract
Gazing at a giant redwood tree in the Pacific Northwest, that has grown to enormous heights over centuries, does little to convince one that plants are built for speed and versatility. Even at the cellular level, a system of polymers-the cell skeleton or cytoskeleton-integrates signals and generates subcellular structures spanning scales of a few nanometers to hundreds of micrometers that coordinate cell growth. The term cytoskeleton itself connotes a stable structure. Clearly, this is not the case. Recent studies using advanced imaging modalities reveal the plant actin cytoskeleton to be a highly dynamic, ever changing assemblage of polymers. These insights along with growing evidence about the biochemical/biophysical properties of plant cytoskeletal polymers, especially those obtained by single filament imaging and reconstituted systems of purified proteins analyzed by total internal reflection fluorescence microscopy, allow the generation of a unique model for the dynamic turnover of actin filaments, termed stochastic dynamics. Here, we review several significant advances and highlight opportunities that will position plants at the vanguard of research on actin organization and turnover. A challenge for the future will be to apply the power of reverse-genetics in several model organisms to test the molecular details of this new model.
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Affiliation(s)
- Laurent Blanchoin
- Institut de Recherches en Technologies et Sciences pour le Vivant - iRTSV, Laboratoire de Phyiologie Cellulaire et Végétale, Commissariat à l'Energie Atomique /Centre National de la Recherche Scientifique/Institut National de la Recherche Agronomique/Université Joseph Fourier, CEA Grenoble, F38054, Grenoble, France.
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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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Zhang H, Qu X, Bao C, Khurana P, Wang Q, Xie Y, Zheng Y, Chen N, Blanchoin L, Staiger CJ, Huang S. Arabidopsis VILLIN5, an actin filament bundling and severing protein, is necessary for normal pollen tube growth. THE PLANT CELL 2010; 22:2749-67. [PMID: 20807879 PMCID: PMC2947167 DOI: 10.1105/tpc.110.076257] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
A dynamic actin cytoskeleton is essential for pollen germination and tube growth. However, the molecular mechanisms underlying the organization and turnover of the actin cytoskeleton in pollen remain poorly understood. Villin plays a key role in the formation of higher-order structures from actin filaments and in the regulation of actin dynamics in eukaryotic cells. It belongs to the villin/gelsolin/fragmin superfamily of actin binding proteins and is composed of six gelsolin-homology domains at its core and a villin headpiece domain at its C terminus. Recently, several villin family members from plants have been shown to sever, cap, and bundle actin filaments in vitro. Here, we characterized a villin isovariant, Arabidopsis thaliana VILLIN5 (VLN5), that is highly and preferentially expressed in pollen. VLN5 loss-of-function retarded pollen tube growth and sensitized actin filaments in pollen grains and tubes to latrunculin B. In vitro biochemical analyses revealed that VLN5 is a typical member of the villin family and retains a full suite of activities, including barbed-end capping, filament bundling, and calcium-dependent severing. The severing activity was confirmed with time-lapse evanescent wave microscopy of individual actin filaments in vitro. We propose that VLN5 is a major regulator of actin filament stability and turnover that functions in concert with oscillatory calcium gradients in pollen and therefore plays an integral role in pollen germination and tube growth.
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Affiliation(s)
- Hua Zhang
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaolu Qu
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chanchan Bao
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Parul Khurana
- Department of Biological Sciences and Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907-2064
| | - Qiannan Wang
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yurong Xie
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Yiyan Zheng
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Naizhi Chen
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Laurent Blanchoin
- Institut de Recherches en Technologie et Sciences pour le Vivant, Laboratoire de Physiologie Cellulaire Végétale, Commissariat à l’Energie Atomique/Centre National de la Recherche Scientifique/Université Joseph Fourier, F38054 Grenoble, France
| | - Christopher J. Staiger
- Department of Biological Sciences and Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907-2064
| | - Shanjin Huang
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Address correspondence to
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Khurana P, Henty JL, Huang S, Staiger AM, Blanchoin L, Staiger CJ. Arabidopsis VILLIN1 and VILLIN3 have overlapping and distinct activities in actin bundle formation and turnover. THE PLANT CELL 2010; 22:2727-48. [PMID: 20807878 PMCID: PMC2947172 DOI: 10.1105/tpc.110.076240] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Revised: 07/29/2010] [Accepted: 08/17/2010] [Indexed: 05/20/2023]
Abstract
Actin filament bundles are higher-order cytoskeletal structures that are crucial for the maintenance of cellular architecture and cell expansion. They are generated from individual actin filaments by the actions of bundling proteins like fimbrins, LIMs, and villins. However, the molecular mechanisms of dynamic bundle formation and turnover are largely unknown. Villins belong to the villin/gelsolin/fragmin superfamily and comprise at least five isovariants in Arabidopsis thaliana. Different combinations of villin isovariants are coexpressed in various tissues and cells. It is not clear whether these isovariants function together and act redundantly or whether they have unique activities. VILLIN1 (VLN1) is a simple filament-bundling protein and is Ca(2+) insensitive. Based on phylogenetic analyses and conservation of Ca(2+) binding sites, we predict that VLN3 is a Ca(2+)-regulated villin capable of severing actin filaments and contributing to bundle turnover. The bundling activity of both isovariants was observed directly with time-lapse imaging and total internal reflection fluorescence (TIRF) microscopy in vitro, and the mechanism mimics the "catch and zipper" action observed in vivo. Using time-lapse TIRF microscopy, we observed and quantified the severing of individual actin filaments by VLN3 at physiological calcium concentrations. Moreover, VLN3 can sever actin filament bundles in the presence of VLN1 when calcium is elevated to micromolar levels. Collectively, these results demonstrate that two villin isovariants have overlapping and distinct activities.
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Affiliation(s)
- Parul Khurana
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
| | - Jessica L. Henty
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
| | - Shanjin Huang
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
| | - Andrew M. Staiger
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
| | - Laurent Blanchoin
- Institut de Recherches en Technologie et Sciences pour le Vivant, Commissariat à l'Energie Atomique/Centre National de la Recherche Scientifique/Institut National de la Recherche Agronomique/Université Joseph Fourier, Commissariat à l’Energie Atomique Grenoble, F38054 Grenoble, France
| | - Christopher J. Staiger
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
- The Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907
- Address correspondence to
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Self-incompatibility in Papaver: identification of the pollen S-determinant PrpS. Biochem Soc Trans 2010; 38:588-92. [PMID: 20298226 DOI: 10.1042/bst0380588] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Many flowering plants are hermaphrodite, posing the problem of self-fertilization and the subsequent loss of the genetic fitness of the offspring. To prevent this, many plants have developed a genetically controlled mechanism called self-incompatibility (SI). When the male and female S-determinants match, self (incompatible) pollen is recognized and rejected before fertilization can occur. In poppy (Papaver rhoeas), the pistil S-determinant (PrsS) is a small secreted protein that interacts with incompatible pollen, initiating a Ca(2+)-dependent signalling network. SI triggers several downstream events, including depolymerization of the cytoskeleton, phosphorylation of two soluble inorganic pyrophosphatases and an MAPK (mitogen-activated protein kinase). This culminates in PCD (programmed cell death) involving several caspase-like activities. The recent discovery of the Papaver pollen S-determinant PrpS marks a significant step forward in the understanding of the Papaver SI system. PrpS encodes a ~20 kDa predicted transmembrane protein which has no homology with known proteins. It is specifically expressed in pollen, linked to the pistil S-determinant, and displays the high polymorphism expected of an S-locus determinant. The present review focuses on the discovery and characterization of PrpS which strongly support the hypothesis that Papaver SI is triggered by the interaction of PrsS and PrpS.
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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: 75] [Impact Index Per Article: 5.4] [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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Su S, Liu Z, Chen C, Zhang Y, Wang X, Zhu L, Miao L, Wang XC, Yuan M. Cucumber mosaic virus movement protein severs actin filaments to increase the plasmodesmal size exclusion limit in tobacco. THE PLANT CELL 2010; 22:1373-87. [PMID: 20435906 PMCID: PMC2879750 DOI: 10.1105/tpc.108.064212] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Revised: 03/27/2010] [Accepted: 04/08/2010] [Indexed: 05/19/2023]
Abstract
Plant viral movement proteins (MPs) enable viruses to pass through cell walls by increasing the size exclusion limit (SEL) of plasmodesmata (PD). Here, we report that the ability of Cucumber mosaic virus (CMV) MP to increase the SEL of the PD could be inhibited by treatment with the actin filament (F-actin)-stabilizing agent phalloidin but not by treatment with the F-actin-destabilizing agent latrunculin A. In vitro studies showed that CMV MP bound globular and F-actin, inhibited actin polymerization, severed F-actin, and participated in plus end capping of F-actin. Analyses of two CMV MP mutants, one with and one without F-actin severing activities, demonstrated that the F-actin severing ability was required to increase the PD SEL. Furthermore, the Tobacco mosaic virus MP also exhibited F-actin severing activity, and its ability to increase the PD SEL was inhibited by treatment with phalloidin. Our data provide evidence to support the hypothesis that F-actin severing is required for MP-induced increase in the SEL of PD. This may have broad implications in the study of the mechanisms of actin dynamics that regulate cell-to-cell transport of viral and endogenous proteins.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Ming Yuan
- State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China
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Poulter NS, Staiger CJ, Rappoport JZ, Franklin-Tong VE. Actin-binding proteins implicated in the formation of the punctate actin foci stimulated by the self-incompatibility response in Papaver. PLANT PHYSIOLOGY 2010; 152:1274-83. [PMID: 20081043 PMCID: PMC2832276 DOI: 10.1104/pp.109.152066] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Accepted: 01/13/2010] [Indexed: 05/21/2023]
Abstract
The actin cytoskeleton is a key target for signaling networks and plays a central role in translating signals into cellular responses in eukaryotic cells. Self-incompatibility (SI) is an important mechanism responsible for preventing self-fertilization. The SI system of Papaver rhoeas pollen involves a Ca(2+)-dependent signaling network, including massive actin depolymerization as one of the earliest cellular responses, followed by the formation of large actin foci. However, no analysis of these structures, which appear to be aggregates of filamentous (F-)actin based on phalloidin staining, has been carried out to date. Here, we characterize and quantify the formation of F-actin foci in incompatible Papaver pollen tubes over time. The F-actin foci increase in size over time, and we provide evidence that their formation requires actin polymerization. Once formed, these SI-induced structures are unusually stable, being resistant to treatments with latrunculin B. Furthermore, their formation is associated with changes in the intracellular localization of two actin-binding proteins, cyclase-associated protein and actin-depolymerizing factor. Two other regulators of actin dynamics, profilin and fimbrin, do not associate with the F-actin foci. This study provides, to our knowledge, the first insights into the actin-binding proteins and mechanisms involved in the formation of these intriguing structures, which appear to be actively formed during the SI response.
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Fu Y. The actin cytoskeleton and signaling network during pollen tube tip growth. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2010; 52:131-7. [PMID: 20377675 DOI: 10.1111/j.1744-7909.2010.00922.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The organization and dynamics of the actin cytoskeleton play key roles in many aspects of plant cell development. The actin cytoskeleton responds to internal developmental cues and environmental signals and is involved in cell division, subcellular organelle movement, cell polarity and polar cell growth. The tip-growing pollen tubes provide an ideal model system to investigate fundamental mechanisms of underlying polarized cell growth. In this system, most signaling cascades required for tip growth, such as Ca(2+)-, small GTPases- and lipid-mediated signaling have been found to be involved in transmitting signals to a large group of actin-binding proteins. These actin-binding proteins subsequently regulate the structure of the actin network, as well as the rapid turnover of actin filaments (F-actin), thereby eventually controlling tip growth. The actin cytoskeleton acts as an integrator in which multiple signaling pathways converge, providing a general growth and regulatory mechanism that applies not only for tip growth but also for polarized diffuse growth in plants.
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Affiliation(s)
- Ying Fu
- State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing, China.
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Blanchoin L, Staiger CJ. Plant formins: Diverse isoforms and unique molecular mechanism. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1803:201-6. [PMID: 18977251 DOI: 10.1016/j.bbamcr.2008.09.015] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 07/03/2008] [Accepted: 09/26/2008] [Indexed: 10/21/2022]
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Yang B, Thorogood D, Armstead IP, Franklin FCH, Barth S. Identification of genes expressed during the self-incompatibility response in perennial ryegrass (Lolium perenne L.). PLANT MOLECULAR BIOLOGY 2009; 70:709-23. [PMID: 19484189 DOI: 10.1007/s11103-009-9501-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2008] [Accepted: 05/16/2009] [Indexed: 05/25/2023]
Abstract
Self-incompatibility (SI) in Lolium perenne is controlled gametophytically by the S-Z two-locus system. S and Z loci mapped to L. perenne linkage groups 1 and 2, respectively, with their corresponding putative-syntenic regions on rice chromosome 5 (R5) and R4. None of the gene products of S and Z have yet been identified. SI cDNA libraries were developed to enrich for SI expressed genes in L. perenne. Transcripts were identified from the SI libraries that were orthologous to sequences on rice R4 and R5. These represent potential SI candidate genes. Altogether ten expressed SI candidate genes were identified. A rapid increase in gene expression within two minutes after pollen-stigma contact was revealed, reaching a maximum between 2 and 10 min. The potential involvement of these genes in the SI reactions is discussed.
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Affiliation(s)
- Bicheng Yang
- Teagasc Crops Research Centre, Oak Park, Carlow, Ireland
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Sinclair A, Schenkel M, Mathur J. Signaling to the Actin Cytoskeleton During Cell Morphogenesis and Patterning. SIGNALING IN PLANTS 2009. [DOI: 10.1007/978-3-540-89228-1_7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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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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Wang T, Xiang Y, Hou J, Ren HY. ABP41 is involved in the pollen tube development via fragmenting actin filaments. MOLECULAR PLANT 2008; 1:1048-55. [PMID: 19825602 DOI: 10.1093/mp/ssn073] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
ABP41 is identified as a novel member of plant villin/gelsolin/fragmin superfamily proteins from lily pollen, which binds stoichiometrically to actin filaments and severs them in vitro. To further understand its in-vivo function and the potential molecular mechanisms, biochemical analysis, fluorescence microscopic observation and microinjection assays were performed. Different biochemical measurements showed that ABP41 maintained actin filaments in forms of short F-actin in vitro. Microinjection of ABP41 into pollen tubes could fragment the pre-existing actin filaments, inhibit the velocity of cytoplasmic streaming, and shorten the length of the clear zone of pollen tube. In addition, it was found that the endogenous ABP41 expressing level was dynamically corresponding to the short actin filament structure in pollen at different stages of pollen germination. Our results suggest that ABP41 is involved in the regulation of actin dynamics during the pollen germination process via maintenance of short dynamic actin filaments.
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Affiliation(s)
- Ting Wang
- Beijing Normal University, Beijing 100875, People's Republic of China
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49
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Bosch M, Poulter NS, Vatovec S, Franklin-Tong VE. Initiation of programmed cell death in self-incompatibility: role for cytoskeleton modifications and several caspase-like activities. MOLECULAR PLANT 2008; 1:879-87. [PMID: 19825589 DOI: 10.1093/mp/ssn053] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Programmed cell death (PCD) is an important and universal process regulating precise death of unwanted cells in eukaryotes. In plants, the existence of PCD has been firmly established for about a decade, and many components shown to be involved in apoptosis/PCD in mammalian systems are found in plant cells undergoing PCD. Here, we review work from our lab demonstrating the involvement of PCD in the self-incompatibility response in Papaver rhoeas pollen. This utilization of PCD as a consequence of a specific pollen-pistil interaction provides a very neat way to destroy unwanted 'self', but not 'non-self' pollen. We discuss recent data providing evidence for SI-induced activation of several caspase-like activities and suggest that an acidification of the cytosol may be a key turning point in the activation of caspase-like proteases executing PCD. We also review data showing the involvement of the actin and microtubule cytoskeletons as well as that of a MAPK in signalling to caspase-mediated PCD. Potential links between these various components in signalling to PCD are discussed. Together, this begins to build a picture of PCD in a single cell system, triggered by a receptor-ligand interaction.
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Affiliation(s)
- Maurice Bosch
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham. B15 2TT, UK
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50
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A role for actin in regulating apoptosis/programmed cell death: evidence spanning yeast, plants and animals. Biochem J 2008; 413:389-404. [PMID: 18613816 DOI: 10.1042/bj20080320] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Achieving an understanding of how apoptosis/PCD (programmed cell death) is integrated within cellular responses to environmental and intracellular signals is a daunting task. From the sensation of a stimulus to the point of no return, a programme of cell death must engage specific pro-death components, whose effects can in turn be enhanced or repressed by downstream regulatory factors. In recent years, considerable progress has been made in our understanding of how components involved in these processes function. We now know that some of the factors involved in PCD networks have ancient origins that pre-date multicellularity and, indeed, eukaryotes themselves. A subject attracting much attention is the role that the actin cytoskeleton, itself a cellular component with ancient origins, plays in cell death regulation. Actin, a key cellular component, has an established role as a cellular sensor, with reorganization and alterations in actin dynamics being a well known consequence of signalling. A range of studies have revealed that actin also plays a key role in apoptosis/PCD regulation. Evidence implicating actin as a regulator of eukaryotic cell death has emerged from studies from the Animal, Plant and Fungal Kingdoms. Here we review recent data that provide evidence for an active, functional role for actin in determining whether PCD is triggered and executed, and discuss these findings within the context of regulation of actin dynamics.
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