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Gao X, Yang B, Zhang J, Wang C, Ren H, Fu Y, Yang Z. PLEIOTROPIC REGULATORY LOCUS1 maintains actin microfilament integrity to regulate pavement cell morphogenesis. PLANT PHYSIOLOGY 2024; 195:356-369. [PMID: 38227494 DOI: 10.1093/plphys/kiae018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 11/28/2023] [Accepted: 11/29/2023] [Indexed: 01/17/2024]
Abstract
Actin dynamics are critical for plant cell morphogenesis, but the underlying signaling mechanisms regulating these dynamics are not well understood. Here, we established that PLEIOTROPIC REGULATORY LOCUS1 (PRL1) modulates leaf pavement cell (PC) morphogenesis in Arabidopsis (Arabidopsis thaliana) by maintaining the dynamic homeostasis of actin microfilaments (MF). Our previous studies indicated that PC shape was determined by antagonistic RHO-RELATED GTPase FROM PLANTS 2 (ROP2) and RHO-RELATED GTPase FROM PLANTS 6 (ROP6) signaling pathways that promote cortical MF and microtubule organization, respectively. Our genetic screen for additional components in ROP6-mediated signaling identified prl1 alleles. Genetic analysis confirmed that PRL1 plays a key role in PC morphogenesis. Mutations in PRL1 caused cortical MF depolymerization, resulting in defective PC morphogenesis. Further genetic analysis revealed that PRL1 is epistatic to ROP2 and ROP6 in PC morphogenesis. Mutations in PRL1 enhanced the effects of ROP2 and ROP6 in PC morphogenesis, leading to a synergistic phenotype in the PCs of ROP2 prl1 and ROP6 prl1. Furthermore, the activities of ROP2 and ROP6 were differentially altered in prl1 mutants, suggesting that ROP2 and ROP6 function downstream of PRL1. Additionally, cortical MF depolymerization in prl1 mutants occurred independently of ROP2 and ROP6, implying that these proteins impact PC morphogenesis in the prl1 mutant through other cellular processes. Our research indicates that PRL1 preserves the structural integrity of actin and facilitates pavement cell morphogenesis in Arabidopsis.
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Affiliation(s)
- Xiaowei Gao
- FAFU-UCR Joint Center for Horticultural Biology and Metabolomics, Haixia Institute of Science and Technology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Bo Yang
- College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Jingjing Zhang
- College of Life Science, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Chi Wang
- College of Life Science, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Huibo Ren
- Basic Forestry and Proteomics Research Center, Haixia Institute of Science and Technology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Ying Fu
- College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Zhenbiao Yang
- Institute for Integrative Genome Biology and Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA
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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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Stroppa N, Onelli E, Moreau P, Maneta-Peyret L, Berno V, Cammarota E, Ambrosini R, Caccianiga M, Scali M, Moscatelli A. Sterols and Sphingolipids as New Players in Cell Wall Building and Apical Growth of Nicotiana tabacum L. Pollen Tubes. PLANTS (BASEL, SWITZERLAND) 2022; 12:8. [PMID: 36616135 PMCID: PMC9824051 DOI: 10.3390/plants12010008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 12/05/2022] [Accepted: 12/12/2022] [Indexed: 06/17/2023]
Abstract
Pollen tubes are tip-growing cells that create safe routes to convey sperm cells to the embryo sac for double fertilization. Recent studies have purified and biochemically characterized detergent-insoluble membranes from tobacco pollen tubes. These microdomains, called lipid rafts, are rich in sterols and sphingolipids and are involved in cell polarization in organisms evolutionarily distant, such as fungi and mammals. The presence of actin in tobacco pollen tube detergent-insoluble membranes and the preferential distribution of these domains on the apical plasma membrane encouraged us to formulate the intriguing hypothesis that sterols and sphingolipids could be a "trait d'union" between actin dynamics and polarized secretion at the tip. To unravel the role of sterols and sphingolipids in tobacco pollen tube growth, we used squalestatin and myriocin, inhibitors of sterol and sphingolipid biosynthesis, respectively, to determine whether lipid modifications affect actin fringe morphology and dynamics, leading to changes in clear zone organization and cell wall deposition, thus suggesting a role played by these lipids in successful fertilization.
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Affiliation(s)
- Nadia Stroppa
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy
| | - Elisabetta Onelli
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy
| | - Patrick Moreau
- CNRS, Laboratoire de Biogenèse Membranaire, University of Bordeaux, UMR 5200, 71 Avenue Edouard Bourlaux, 33140 Villenave d’Ornon, France
| | - Lilly Maneta-Peyret
- CNRS, Laboratoire de Biogenèse Membranaire, University of Bordeaux, UMR 5200, 71 Avenue Edouard Bourlaux, 33140 Villenave d’Ornon, France
| | - Valeria Berno
- ALEMBIC Advanced Light and Electron Microscopy BioImaging Center, San Raffaele Scientific Institute, DIBIT 1, Via Olgettina 58, 20132 Milan, Italy
| | - Eugenia Cammarota
- ALEMBIC Advanced Light and Electron Microscopy BioImaging Center, San Raffaele Scientific Institute, DIBIT 1, Via Olgettina 58, 20132 Milan, Italy
| | - Roberto Ambrosini
- Dipartimento di Scienze e Politiche Ambientali, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy
| | - Marco Caccianiga
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy
| | - Monica Scali
- Dipartimento di Scienze della Vita, Università degli Studi di Siena, Via Aldo Moro 2, 53100 Siena, Italy
| | - Alessandra Moscatelli
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy
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Jiang Y, Lu Q, Huang S. Functional non-equivalence of pollen ADF isovariants in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 110:1068-1081. [PMID: 35233873 DOI: 10.1111/tpj.15723] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 02/24/2022] [Accepted: 02/26/2022] [Indexed: 06/14/2023]
Abstract
ADF/cofilin is a central regulator of actin dynamics. We previously demonstrated that two closely related Arabidopsis class IIa ADF isovariants, ADF7 and ADF10, are involved in the enhancement of actin turnover in pollen, but whether they have distinct functions remains unknown. Here, we further demonstrate that they exhibit distinct functions in regulating actin turnover both in vitro and in vivo. We found that ADF7 binds to ADP-G-actin with lower affinity, and severs and depolymerizes actin filaments less efficiently in vitro than ADF10. Accordingly, in pollen grains, ADF7 more extensively decorates actin filaments and is less freely distributed in the cytoplasm compared to ADF10. We further demonstrate that ADF7 and ADF10 show distinct intracellular localizations during pollen germination, and they have non-equivalent functions in promoting actin turnover in pollen. We thus propose that cooperation and labor division of ADF7 and ADF10 enable pollen cells to achieve exquisite control of the turnover of different actin structures to meet different cellular needs.
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Affiliation(s)
- Yuxiang Jiang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Qiaonan Lu
- 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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Kollárová E, Baquero Forero A, Cvrčková F. The Arabidopsis thaliana Class II Formin FH13 Modulates Pollen Tube Growth. FRONTIERS IN PLANT SCIENCE 2021; 12:599961. [PMID: 33679824 PMCID: PMC7929981 DOI: 10.3389/fpls.2021.599961] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 01/29/2021] [Indexed: 05/10/2023]
Abstract
Formins are a large, evolutionarily conserved family of actin-nucleating proteins with additional roles in regulating microfilament, microtubule, and membrane dynamics. Angiosperm formins, expressed in both sporophytic and gametophytic tissues, can be divided into two subfamilies, Class I and Class II, each often exhibiting characteristic domain organization. Gametophytically expressed Class I formins have been documented to mediate plasma membrane-based actin assembly in pollen grains and pollen tubes, contributing to proper pollen germination and pollen tube tip growth, and a rice Class II formin, FH5/RMD, has been proposed to act as a positive regulator of pollen tube growth based on mutant phenotype and overexpression data. Here we report functional characterization of the Arabidopsis thaliana pollen-expressed typical Class II formin FH13 (At5g58160). Consistent with published transcriptome data, live-cell imaging in transgenic plants expressing fluorescent protein-tagged FH13 under the control of the FH13 promoter revealed expression in pollen and pollen tubes with non-homogeneous signal distribution in pollen tube cytoplasm, suggesting that this formin functions in the male gametophyte. Surprisingly, fh13 loss of function mutations do not affect plant fertility but result in stimulation of in vitro pollen tube growth, while tagged FH13 overexpression inhibits pollen tube elongation. Pollen tubes of mutants expressing a fluorescent actin marker exhibited possible minor alterations of actin organization. Our results thus indicate that FH13 controls or limits pollen tube growth, or, more generally, that typical Class II formins should be understood as modulators of pollen tube elongation rather than merely components of the molecular apparatus executing tip growth.
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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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Mechanism of CAP1-mediated apical actin polymerization in pollen tubes. Proc Natl Acad Sci U S A 2019; 116:12084-12093. [PMID: 31123151 DOI: 10.1073/pnas.1821639116] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Srv2p/CAP1 is an essential regulator of actin turnover, but its exact function in regulating actin polymerization, particularly the contribution of its actin nucleotide exchange activity, remains incompletely understood. We found that, although Arabidopsis CAP1 is distributed uniformly in the cytoplasm, its loss of function has differential effects on the actin cytoskeleton within different regions of the pollen tube. Specifically, the F-actin level increases in the shank but decreases in the apical region of cap1 pollen tubes. The reduction in apical F-actin results mainly from impaired polymerization of membrane-originated actin within cap1 pollen tubes. The actin nucleotide exchange activity of CAP1 is involved in apical actin polymerization. CAP1 acts synergistically with pollen ADF and profilin to promote actin turnover in vitro, and it can overcome the inhibitory effects of ADF and synergize with profilin to promote actin nucleotide exchange. Consistent with its role as a shuttle molecule between ADF and profilin, the cytosolic concentration of CAP1 is much lower than that of ADF and profilin in pollen. Thus, CAP1 synergizes with ADF and profilin to drive actin turnover in pollen and promote apical actin polymerization in pollen tubes in a manner that involves its actin nucleotide exchange activity.
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Wang Y, Clevenger JP, Illa-Berenguer E, Meulia T, van der Knaap E, Sun L. A Comparison of sun, ovate, fs8.1 and Auxin Application on Tomato Fruit Shape and Gene Expression. PLANT & CELL PHYSIOLOGY 2019; 60:1067-1081. [PMID: 30753610 DOI: 10.1093/pcp/pcz024] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 02/07/2019] [Indexed: 05/04/2023]
Abstract
Elongated tomato fruit shape is the result of the action of the fruit shape genes possibly in coordination with the phytohormone auxin. To investigate the possible link between auxin and the fruit shape genes, a series of auxin (2,4-D) treatments were performed on the wild-type and the fruit shape near-isogenic lines (NILs) in Solanum pimpinellifolium accession LA1589 background. Morphological and histological analyses indicated that auxin application approximately 3 weeks before anthesis led to elongated pear-shaped ovaries and fruits, which was mainly attributed to the increase of ovary/fruit proximal end caused by the increase of both cell number and cell size. Fruit shape changes caused by SUN, OVATE and fs8.1 were primarily due to the alterations of cell number along different growth axes. Particularly, SUN caused elongation by extending cell number along the entire proximal-distal axis, whereas OVATE caused fruit elongation in the proximal area, which was most similar to the effect of auxin on ovary shape. Expression analysis of flower buds at different stages in fruit shape NILs indicated that SUN had a stronger impact on the transcriptome than OVATE and fs8.1. The sun NIL differentially expressed genes were enriched in several biological processes, such as lipid metabolism, ion transmembrane and actin cytoskeleton organization. Additionally, SUN also shifted the expression of the auxin-related genes, including those involved in auxin biosynthesis, homeostasis, signal transduction and polar transport, indicating that SUN may regulate ovary/fruit shape through modifying the expression of auxin-related genes very early during the formation of the ovary in the developing flower.
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Affiliation(s)
- Yanping Wang
- College of Horticulture, China Agricultural University, Beijing, P.R. China
- Department of Horticulture and Crop Science, The Ohio State University/OARDC, Wooster, OH, USA
- National Engineering Research Center for Vegetables, Beijing Academy of Agriculture and Forestry Sciences, Beijing, P.R. China
| | - Josh P Clevenger
- Department of Horticulture and Crop Science, The Ohio State University/OARDC, Wooster, OH, USA
- Institute of Plant Breeding, Genetics & Genomics, University of Georgia, Athens, GA, USA
- Center for Applied Genetic Technologies, Mars Wrigley Confectionery, Athens, GA, USA
| | | | - Tea Meulia
- Department of Plant Pathology, Molecular and Cellular Imaging Center, The Ohio State University/OARDC, Wooster, OH, USA
| | - Esther van der Knaap
- Department of Horticulture and Crop Science, The Ohio State University/OARDC, Wooster, OH, USA
- Institute of Plant Breeding, Genetics & Genomics, University of Georgia, Athens, GA, USA
- Center for Applied Genetic Technologies, University of Georgia, Athens, GA, USA
| | - Liang Sun
- College of Horticulture, China Agricultural University, Beijing, P.R. China
- Department of Horticulture and Crop Science, The Ohio State University/OARDC, Wooster, OH, USA
- Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, Department of Vegetable Science, College of Horticulture, China Agricultural University, Beijing, P.R. China
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Arabidopsis class I formins control membrane-originated actin polymerization at pollen tube tips. PLoS Genet 2018; 14:e1007789. [PMID: 30418966 PMCID: PMC6258422 DOI: 10.1371/journal.pgen.1007789] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 11/26/2018] [Accepted: 10/25/2018] [Indexed: 12/17/2022] Open
Abstract
A population of dynamic apical actin filaments is required for rapid polarized pollen tube growth. However, the cellular mechanisms driving their assembly remain incompletely understood. It was postulated that formin is a major player in nucleating apical actin assembly, but direct genetic and cytological evidence remains to be firmly established. Here we found that both Arabidopsis formin 3 (AtFH3) and formin 5 (AtFH5) are involved in the regulation of apical actin polymerization and actin array construction in pollen tubes, with AtFH3 playing a more dominant role. We found that both formins have plasma membrane (PM) localization signals but exhibit distinct PM localization patterns in the pollen tube, and loss of their function reduces the amount of apical actin filaments. Live-cell imaging revealed that the reduction in filamentous actin is very likely due to the decrease in filament elongation. Furthermore, we found that the rate of tip-directed vesicle transport is reduced and the pattern of apical vesicle accumulation is altered in formin loss-of-function mutant pollen tubes, which explains to some extent the reduction in pollen tube elongation. Thus, we provide direct genetic and cytological evidence showing that formin is an important player in nucleating actin assembly from the PM at pollen tube tips. Actin polymerization has been implicated in the regulation of rapid polarized pollen tube growth. The important role of actin polymerization is well appreciated, but the mechanisms that regulate rapid actin polymerization in pollen tubes remain incompletely understood. It was postulated that one of the major actin polymerization pathways in pollen tubes involves formin/profilin modules. However, direct genetic and cytological evidence is still required to support the role of formin in this framework. Using state-of-the-art live-cell imaging in combination with reverse genetic approaches, we demonstrate here that two class I formins, Arabidopsis formin 3 (AtFH3) and formin 5 (AtFH5), are involved in the regulation of apical actin polymerization and actin array construction in pollen tubes. In support of the role of AtFH3 and AtFH5 in regulating membrane-originated apical actin polymerization, we found that both of them are localized to the plasma membrane (PM) at pollen tube tips. Live-cell imaging revealed that the reduction in filamentous actin is very likely due to the decrease in elongation of actin filaments originating from the apical membrane. We also found that AtFH3 and AtFH5 exhibit distinct PM localization patterns in the pollen tube, suggesting that they might have distinct roles in regulating actin polymerization in pollen tubes. Our study provides direct genetic and cytological evidence that formins act as important players in regulating apical actin assembly in pollen tubes.
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