1
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de Keijzer J, van Spoordonk R, van der Meer-Verweij JE, Janson M, Ketelaar T. Kinesin-4 optimizes microtubule orientations for responsive tip growth guidance in moss. J Cell Biol 2023; 222:e202202018. [PMID: 37389658 PMCID: PMC10316633 DOI: 10.1083/jcb.202202018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 04/18/2023] [Accepted: 06/06/2023] [Indexed: 07/01/2023] Open
Abstract
Tip-growing cells of, amongst others, plants and fungi secrete wall materials in a highly polarized fashion for fast and efficient colonization of the environment. A polarized microtubule cytoskeleton, in which most microtubule ends are directed toward the growing apex, has been implicated in directing growth. Its organizing principles, in particular regarding maintenance of network unipolarity, have remained elusive. We show that a kinesin-4 protein, hitherto best known for a role in cytokinesis, suppresses encounters between antiparallel microtubules. Without this activity, microtubules hyper-aligned along the growth axis and increasingly grew away from the apex. Cells themselves displayed an overly straight growth path and a delayed gravitropic response. This result revealed conflicting systemic needs for a stable growth direction and an ability to change course in response to extracellular cues. Thus, the use of selective inhibition of microtubule growth at antiparallel overlaps constitutes a new organizing principle within a unipolar microtubule array.
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Affiliation(s)
- Jeroen de Keijzer
- Laboratory of Cell Biology, Wageningen University, Wageningen, Netherlands
| | | | | | - Marcel Janson
- Laboratory of Cell Biology, Wageningen University, Wageningen, Netherlands
| | - Tijs Ketelaar
- Laboratory of Cell Biology, Wageningen University, Wageningen, Netherlands
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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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Zhu L, Fu Y. Investigation of ROP GTPase Activity and Cytoskeleton Dynamics During Tip Growth in Root Hairs and Pollen Tubes. Methods Mol Biol 2023; 2604:227-235. [PMID: 36773237 DOI: 10.1007/978-1-0716-2867-6_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
Pollen tubes and root hairs are typical tip-growing cells and are employed as model systems to study plant cell polarity. Previous studies have shown that the Rho family ROP GTPase plays a critical role in the regulation of pollen tube and root hair growth. Periodically, activated ROP GTPase coordinates with the tip-focused calcium gradient, to regulate actin dynamics and vesicle trafficking. Moreover, microtubules are also involved in organelle movement and growth directionality. Here, we describe methods for analyzing the spatiotemporal localization and activity of ROP, cortical microtubule organization, and F-actin dynamics in pollen tubes and/or root hairs.
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Affiliation(s)
- Lei Zhu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, China.
| | - Ying Fu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, China
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4
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Li E, Zhang YL, Qin Z, Xu M, Qiao Q, Li S, Li SW, Zhang Y. Signaling network controlling ROP-mediated tip growth in Arabidopsis and beyond. PLANT COMMUNICATIONS 2023; 4:100451. [PMID: 36114666 PMCID: PMC9860187 DOI: 10.1016/j.xplc.2022.100451] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 08/24/2022] [Accepted: 09/12/2022] [Indexed: 06/15/2023]
Abstract
Cell polarity operates across a broad range of spatial and temporal scales and is essential for specific biological functions of polarized cells. Tip growth is a special type of polarization in which a single and unique polarization site is established and maintained, as for the growth of root hairs and pollen tubes in plants. Extensive studies in past decades have demonstrated that the spatiotemporal localization and activity of Rho of Plants (ROPs), the only class of Rho GTPases in plants, are critical for tip growth. ROPs are switched on or off by different factors to initiate dynamic intracellular activities, leading to tip growth. Recent studies have also uncovered several feedback modules for ROP signaling. In this review, we summarize recent progress on ROP signaling in tip growth, focusing on molecular mechanisms that underlie the dynamic distribution and activity of ROPs in Arabidopsis. We also highlight feedback modules that control ROP-mediated tip growth and provide a perspective for building a complex ROP signaling network. Finally, we provide an evolutionary perspective for ROP-mediated tip growth in Physcomitrella patens and during plant-rhizobia interaction.
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Affiliation(s)
- En Li
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, Shandong 271018, China.
| | - Yu-Ling Zhang
- College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Zheng Qin
- College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Meng Xu
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, Shandong 271018, China
| | - Qian Qiao
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, Shandong 271018, China
| | - Sha Li
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, Shandong 271018, China
| | - Shan-Wei Li
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, Shandong 271018, China
| | - Yan Zhang
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, Shandong 271018, China.
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5
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Zhou Z, Zheng S, Haq SIU, Zheng D, Qiu QS. Regulation of pollen tube growth by cellular pH and ions. JOURNAL OF PLANT PHYSIOLOGY 2022; 277:153792. [PMID: 35973258 DOI: 10.1016/j.jplph.2022.153792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Revised: 07/29/2022] [Accepted: 08/06/2022] [Indexed: 06/15/2023]
Abstract
Tip growth of the pollen tube is a model system for the study of cell polarity establishment in flowering plants. The tip growth of the pollen tube displays an oscillating pattern corresponding to cellular ion and pH dynamics. Therefore, cellular pH and ions play an important role in pollen growth and development. In this review, we summarized the current advances in understanding the function of cellular pH and ions in regulating pollen tube growth. We analyzed the physiological roles and underlying mechanisms of cellular pH and ions, including Ca2+, K+, and Cl-, in regulating pollen tube growth. We further examined the function of Ca2+ in regulating cytoskeletons, small G proteins, and cell wall development in relation to pollen tube growth. We also examined the regulatory roles of cellular pH in pollen tube growth as well as pH regulation of ion flow, cell wall development, auxin signaling, and cytoskeleton function in pollen. In addition, we assessed the regulation of pollen tube growth by proton pumps and the maintenance of pH homeostasis in the trans-Golgi network by ion transporters. The interplay of ion homeostasis and pH dynamics was also assessed. We discussed the unanswered questions regarding pollen tube growth that need to be addressed in the future.
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Affiliation(s)
- Zhenguo Zhou
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 73000, China.
| | - Sheng Zheng
- College of Life Sciences, Northwest Normal University, Lanzhou, Gansu, 730070, China; Academy of Plateau Science and Sustainability, Qinghai Normal University, Xining, Qinghai, 810016, China
| | - Syed Inzimam Ul Haq
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 73000, China
| | - Dianfeng Zheng
- College of Coastal Agricultural Sciences, Guangdong Ocean University, Zhanjiang, Guangdong, 524088, China
| | - Quan-Sheng Qiu
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 73000, China; Academy of Plateau Science and Sustainability, Qinghai Normal University, Xining, Qinghai, 810016, China; College of Coastal Agricultural Sciences, Guangdong Ocean University, Zhanjiang, Guangdong, 524088, China.
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6
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Taya K, Takeuchi S, Takahashi M, Hayashi KI, Mikami K. Auxin Regulates Apical Stem Cell Regeneration and Tip Growth in the Marine Red Alga Neopyropia yezoensis. Cells 2022; 11:cells11172652. [PMID: 36078060 PMCID: PMC9454478 DOI: 10.3390/cells11172652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 08/24/2022] [Accepted: 08/25/2022] [Indexed: 11/16/2022] Open
Abstract
The red alga Neopyropia yezoensis undergoes polarized elongation and asymmetrical cell division of the apical stem cell during tip growth in filamentous generations of its life cycle: the conchocelis and conchosporangium. Side branches are also produced via tip growth, a process involving the regeneration and asymmetrical division of the apical stem cell. Here, we demonstrate that auxin plays a crucial role in these processes by using the auxin antagonist 2-(1H-Indol-3-yl)-4-oxo-4-phenyl-butyric acid (PEO-IAA), which specifically blocks the activity of the auxin receptor TRANSPORT INHIBITOR RESPONSE1 (TIR1) in land plants. PEO-IAA repressed both the regeneration and polarized tip growth of the apical stem cell in single-celled conchocelis; this phenomenon was reversed by treatment with the auxin indole-3-acetic acid (IAA). In addition, tip growth of the conchosporangium was accelerated by IAA treatment but repressed by PEO-IAA treatment. These findings indicate that auxin regulates polarized tip cell growth and that an auxin receptor-like protein is present in N. yezoensis. The sensitivity to different 5-alkoxy-IAA analogs differs considerably between N. yezoensis and Arabidopsis thaliana. N. yezoensis lacks a gene encoding TIR1, indicating that its auxin receptor-like protein differs from the auxin receptor of terrestrial plants. These findings shed light on auxin-induced mechanisms and the regulation of tip growth in plants.
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Affiliation(s)
- Kensuke Taya
- Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate 041-8611, Japan
| | - Shunzei Takeuchi
- School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate 041-8611, Japan
| | - Megumu Takahashi
- Faculty of Bio-Industry, Tokyo University of Agriculture, 196 Yasaka, Abashiri 099-2493, Japan
| | - Ken-ichiro Hayashi
- Department of Bioscience, Okayama University of Science, 1-1 Ridaicho, Kita-ku, Okayama 700-0005, Japan
| | - Koji Mikami
- School of Food Industrial Sciences, Miyagi University, 2-2-1 Hatatate, Taihaku-ku, Sendai 982-0215, Japan
- Correspondence: ; Tel.: +81-22-245-1411
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7
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Çetinbaş-Genç A, Conti V, Cai G. Let's shape again: the concerted molecular action that builds the pollen tube. PLANT REPRODUCTION 2022; 35:77-103. [PMID: 35041045 DOI: 10.1007/s00497-022-00437-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 01/06/2022] [Indexed: 06/14/2023]
Abstract
The pollen tube is being subjected to control by a complex network of communication that regulates its shape and the misfunction of a single component causes specific deformations. In flowering plants, the pollen tube is a tubular extension of the pollen grain required for successful sexual reproduction. Indeed, maintaining the unique shape of the pollen tube is essential for the pollen tube to approach the embryo sac. Many processes and molecules (such as GTPase activity, phosphoinositides, Ca2+ gradient, distribution of reactive oxygen species and nitric oxide, nonuniform pH values, organization of the cytoskeleton, balance between exocytosis and endocytosis, and cell wall structure) play key and coordinated roles in maintaining the cylindrical shape of pollen tubes. In addition, the above factors must also interact with each other so that the cell shape is maintained while the pollen tube follows chemical signals in the pistil that guide it to the embryo sac. Any intrinsic changes (such as erroneous signals) or extrinsic changes (such as environmental stresses) can affect the above factors and thus fertilization by altering the tube morphology. In this review, the processes and molecules that enable the development and maintenance of the unique shape of pollen tubes in angiosperms are presented emphasizing their interaction with specific tube shape. Thus, the purpose of the review is to investigate whether specific deformations in pollen tubes can help us to better understand the mechanism underlying pollen tube shape.
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Affiliation(s)
- Aslıhan Çetinbaş-Genç
- Department of Biology, Marmara University, Göztepe Campus, 34722, Kadıköy, Istanbul, Turkey.
| | - Veronica Conti
- Department of Life Sciences, University of Siena, via Mattioli 4, 53100, Siena, Italy
| | - Giampiero Cai
- Department of Life Sciences, University of Siena, via Mattioli 4, 53100, Siena, Italy
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8
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Xiao Z, Brunel N, Tian C, Guo J, Yang Z, Cui X. Constrained Nonlinear and Mixed Effects Integral Differential Equation Models for Dynamic Cell Polarity Signaling. FRONTIERS IN PLANT SCIENCE 2022; 13:847671. [PMID: 35693156 PMCID: PMC9175011 DOI: 10.3389/fpls.2022.847671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 04/08/2022] [Indexed: 06/15/2023]
Abstract
Polar cell growth is a process that couples the establishment of cell polarity with growth and is extremely important in the growth, development, and reproduction of eukaryotic organisms, such as pollen tube growth during plant fertilization and neuronal axon growth in animals. Pollen tube growth requires dynamic but polarized distribution and activation of a signaling protein named ROP1 to the plasma membrane via three processes: positive feedback and negative feedback regulation of ROP1 activation and its lateral diffusion along the plasma membrane. In this paper, we introduce a mechanistic integro-differential equation (IDE) along with constrained semiparametric regression to quantitatively describe the interplay among these three processes that lead to the polar distribution of active ROP1 at a steady state. Moreover, we introduce a population variability by a constrained nonlinear mixed model. Our analysis of ROP1 activity distributions from multiple pollen tubes revealed that the equilibrium between the positive and negative feedbacks for pollen tubes with similar shapes are remarkably stable, permitting us to infer an inherent quantitative relationship between the positive and negative feedback loops that defines the tip growth of pollen tubes and the polarity of tip growth.
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Affiliation(s)
- Zhen Xiao
- Department of Statistics, University of California, Riverside, Riverside, CA, United States
| | - Nicolas Brunel
- Laboratoire de Mathématiques et Modélisation d'Evry, UMR CNRS 8071, ENSIIE, Évry-Courcouronnes, France
| | - Chenwei Tian
- Department of Statistics, University of California, Riverside, Riverside, CA, United States
| | - Jingzhe Guo
- Department of Botany and Plant Sciences, University of California, Riverside, Riverside, CA, United States
- Institute for Integrative Genome Biology, University of California, Riverside, Riverside, CA, United States
| | - Zhenbiao Yang
- Department of Botany and Plant Sciences, University of California, Riverside, Riverside, CA, United States
- Institute for Integrative Genome Biology, University of California, Riverside, Riverside, CA, United States
| | - Xinping Cui
- Department of Statistics, University of California, Riverside, Riverside, CA, United States
- Institute for Integrative Genome Biology, University of California, Riverside, Riverside, CA, United States
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9
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Zhao H, Wang Y, Zhao S, Fu Y, Zhu L. HOMEOBOX PROTEIN 24 mediates the conversion of indole-3-butyric acid to indole-3-acetic acid to promote root hair elongation. THE NEW PHYTOLOGIST 2021; 232:2057-2070. [PMID: 34480752 DOI: 10.1111/nph.17719] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 08/26/2021] [Indexed: 06/13/2023]
Abstract
Indole-3-acetic acid (IAA) is a predominant form of active auxin in plants. In addition to de novo biosynthesis and release from its conjugate forms, IAA can be converted from its precursor indole-3-butyric acid (IBA). The IBA-derived IAA may help drive root hair elongation in Arabidopsis thaliana seedlings, but how the IBA-to-IAA conversion is regulated and affects IAA function requires further investigation. In this study, HOMEOBOX PROTEIN 24 (HB24), a transcription factor in the zinc finger-homeodomain family (ZF-HD family) of proteins, was identified. With loss of HB24 function, defective growth occurred in root hairs. INDOLE-3-BUTYRIC ACID RESPONSE 1 (IBR1), which encodes an enzyme involved in the IBA-to-IAA conversion, was identified as a direct target of HB24 for the control of root hair elongation. The exogenous IAA or auxin analogue 1-naphthalene acetic acid (NAA) both rescued the root hair growth phenotype of hb24 mutants, but IBA did not, suggesting a role for HB24 in the IBA-to-IAA conversion. Therefore, HB24 participates in root hair elongation by upregulating the expression of IBR1 and subsequently promoting the IBA-to-IAA conversion. Moreover, IAA also elevated the expression of HB24, suggesting a feedback loop is involved in IBA-to-IAA conversion-mediated root hair elongation.
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Affiliation(s)
- Huan Zhao
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Yutao Wang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Shuai Zhao
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Ying Fu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Lei Zhu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
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10
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Tian X, Wang X, Li Y. Myosin XI-B is involved in the transport of vesicles and organelles in pollen tubes of Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 108:1145-1161. [PMID: 34559914 DOI: 10.1111/tpj.15505] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 09/09/2021] [Accepted: 09/14/2021] [Indexed: 06/13/2023]
Abstract
The movement of organelles and vesicles in pollen tubes depends on F-actin. However, the molecular mechanism through which plant myosin XI drives the movement of organelles is still controversial, and the relationship between myosin XI and vesicle movement in pollen tubes is also unclear. In this study, we found that the siliques of the myosin xi-b/e mutant were obviously shorter than those of the wild-type (WT) and that the seed set of the mutant was severely deficient. The pollen tube growth of myosin xi-b/e was significantly inhibited both in vitro and in vivo. Fluorescence recovery after photobleaching showed that the velocity of vesicle movement in the pollen tube tip of the myosin xi-b/e mutant was lower than that of the WT. It was also found that peroxisome movement was significantly inhibited in the pollen tubes of the myosin xi-b/e mutant, while the velocities of the Golgi stack and mitochondrial movement decreased relatively less in the pollen tubes of the mutant. The endoplasmic reticulum streaming in the pollen tube shanks was not significantly different between the WT and the myosin xi-b/e mutant. In addition, we found that myosin XI-B-GFP colocalized obviously with vesicles and peroxisomes in the pollen tubes of Arabidopsis. Taken together, these results indicate that myosin XI-B may bind mainly to vesicles and peroxisomes, and drive their movement in pollen tubes. These results also suggest that the mechanism by which myosin XI drives organelle movement in plant cells may be evolutionarily conserved compared with other eukaryotic cells.
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Affiliation(s)
- Xiulin Tian
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Xingjuan Wang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Yan Li
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
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11
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Hayashi M, Palmgren M. The quest for the central players governing pollen tube growth and guidance. PLANT PHYSIOLOGY 2021; 185:682-693. [PMID: 33793904 PMCID: PMC8133568 DOI: 10.1093/plphys/kiaa092] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 12/06/2020] [Indexed: 05/02/2023]
Abstract
Recent insights into the mechanism of pollen tube growth and guidance point to the importance of H+ dynamics, which are regulated by the plasma membrane H+-ATPase.
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Affiliation(s)
- Maki Hayashi
- Department for Plant and Environmental Sciences, University of Copenhagen, Frederiksberg C, Copenhagen, Denmark
| | - Michael Palmgren
- Department for Plant and Environmental Sciences, University of Copenhagen, Frederiksberg C, Copenhagen, Denmark
- International Research Centre for Environmental Membrane Biology, Foshan University, Foshan 528000,China
- Author for communication:
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12
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Li H, Hu J, Pang J, Zhao L, Yang B, Kang X, Wang A, Xu T, Yang Z. Rho GTPase ROP1 Interactome Analysis Reveals Novel ROP1-Associated Pathways for Pollen Tube Polar Growth in Arabidopsis. Int J Mol Sci 2020; 21:ijms21197033. [PMID: 32987815 PMCID: PMC7582345 DOI: 10.3390/ijms21197033] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 09/09/2020] [Accepted: 09/10/2020] [Indexed: 12/27/2022] Open
Abstract
ROP (Rho-like GTPases from plants) GTPases are polarly localized key regulators of polar growth in pollen tubes and other cells in plants. However, how ROP GTPases are regulated and how they control polar growth remains to be fully understood. To gain new insights into ROP-dependent mechanisms underlying polar cell growth, we characterized the interactome of ROP1 GTPase that controls Arabidopsis pollen tube (PT) tip growth, an extreme form of polar cell growth. We established an efficient method for culturing Arabidopsis pollen tubes in liquid medium, which was used for immunoprecipitation/mass spectrometry-based identification of ROP1-associated proteins. A total of 654 candidates were isolated from the ROP1 interactome in Arabidopsis pollen tubes, and GO (Gene Ontology) classification and pathway analysis revealed multiple uncharacterized ROP1-dependent processes including translation, cell wall modification, post transcriptional modification, and ion homeostasis, in addition to known ROP1-dependent pathways. The ROP1-interactome data was further supported by the co-expression of the candidate interactors in highly mature pollen with PT germination and growth defects being discovered in 25% (8/32) of the candidate mutant genes. Taken together, our work uncovers valuable information for the identification and functional elucidation of ROP-associated proteins in the regulation of polar growth, and provides a reliable reference to identify critical regulators of polar cell growth in the future.
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Affiliation(s)
- Hui Li
- CAS Center for Excellence in Molecular Plant Sciences/Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 201602, China; (J.H.); (L.Z.); (B.Y.); (X.K.); (T.X.)
- Center for Plant Cell Biology, Institute of Integrative Genome Biology, and Department of Botany and Plant Sciences, University of California, Riverside, CA 92508, USA;
- Correspondence:
| | - Jinbo Hu
- CAS Center for Excellence in Molecular Plant Sciences/Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 201602, China; (J.H.); (L.Z.); (B.Y.); (X.K.); (T.X.)
- Shanghai Institute of Plant Physiology and Ecology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jing Pang
- School of Life Sciences, Jiangsu Normal University, Xuzhou 221116, China; (J.P.); (A.W.)
| | - Liangtao Zhao
- CAS Center for Excellence in Molecular Plant Sciences/Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 201602, China; (J.H.); (L.Z.); (B.Y.); (X.K.); (T.X.)
| | - Bing Yang
- CAS Center for Excellence in Molecular Plant Sciences/Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 201602, China; (J.H.); (L.Z.); (B.Y.); (X.K.); (T.X.)
| | - Xinlei Kang
- CAS Center for Excellence in Molecular Plant Sciences/Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 201602, China; (J.H.); (L.Z.); (B.Y.); (X.K.); (T.X.)
| | - Aimin Wang
- School of Life Sciences, Jiangsu Normal University, Xuzhou 221116, China; (J.P.); (A.W.)
| | - Tongda Xu
- CAS Center for Excellence in Molecular Plant Sciences/Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 201602, China; (J.H.); (L.Z.); (B.Y.); (X.K.); (T.X.)
- FAFU-UCR Joint Center for Horticultural Biology and Metabolomics, Institute of Science and Technology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Zhenbiao Yang
- Center for Plant Cell Biology, Institute of Integrative Genome Biology, and Department of Botany and Plant Sciences, University of California, Riverside, CA 92508, USA;
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13
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Engelhardt S, Trutzenberg A, Hückelhoven R. Regulation and Functions of ROP GTPases in Plant-Microbe Interactions. Cells 2020; 9:E2016. [PMID: 32887298 PMCID: PMC7565977 DOI: 10.3390/cells9092016] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 08/28/2020] [Accepted: 08/31/2020] [Indexed: 02/07/2023] Open
Abstract
Rho proteins of plants (ROPs) form a specific clade of Rho GTPases, which are involved in either plant immunity or susceptibility to diseases. They are intensively studied in grass host plants, in which ROPs are signaling hubs downstream of both cell surface immune receptor kinases and intracellular nucleotide-binding leucine-rich repeat receptors, which activate major branches of plant immune signaling. Additionally, invasive fungal pathogens may co-opt the function of ROPs for manipulation of the cytoskeleton, cell invasion and host cell developmental reprogramming, which promote pathogenic colonization. Strikingly, mammalian bacterial pathogens also initiate both effector-triggered susceptibility for cell invasion and effector-triggered immunity via Rho GTPases. In this review, we summarize central concepts of Rho signaling in disease and immunity of plants and briefly compare them to important findings in the mammalian research field. We focus on Rho activation, downstream signaling and cellular reorganization under control of Rho proteins involved in disease progression and pathogen resistance.
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Affiliation(s)
| | | | - Ralph Hückelhoven
- Phytopathology, TUM School of Life Sciences Weihenstephan, Technical University of Munich, Emil-Ramann-Straße 2, 85354 Freising, Germany; (S.E.); (A.T.)
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14
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Orr RG, Cheng X, Vidali L, Bezanilla M. Orchestrating cell morphology from the inside out - using polarized cell expansion in plants as a model. Curr Opin Cell Biol 2019; 62:46-53. [PMID: 31546159 DOI: 10.1016/j.ceb.2019.08.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 07/30/2019] [Accepted: 08/02/2019] [Indexed: 12/16/2022]
Abstract
Intracellular organization forms the basis of changes in the extracellular matrix. In walled cells, these changes are essential for morphogenesis and growth. The highly polarized cells of mosses and liverworts together with root hairs and pollen tubes are geometrically simple cells that develop in the absence of complex tissue-scale signaling, providing an excellent model to study cell polarity. Recent advances present a unifying theme where the cytoskeleton and its associated motors work in coordination with vesicle trafficking. This coordination results in a recycling system near the cell tip, where endocytosed molecules are sorted and combined with exocytic cargo driving growth. Interestingly, functional similarities between filamentous fungi and plants promise to advance our understanding of cell polarization and growth across kingdoms.
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Affiliation(s)
- Robert G Orr
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester MA, 01609, United States
| | - Xiaohang Cheng
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, United States
| | - Luis Vidali
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester MA, 01609, United States
| | - Magdalena Bezanilla
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, United States.
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15
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Kato M, Tsuge T, Maeshima M, Aoyama T. Arabidopsis PCaP2 modulates the phosphatidylinositol 4,5-bisphosphate signal on the plasma membrane and attenuates root hair elongation. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2019; 99:610-625. [PMID: 30604455 DOI: 10.1111/tpj.14226] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 12/12/2018] [Accepted: 12/17/2018] [Indexed: 05/22/2023]
Abstract
Phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2 ] serves as a subcellular signal on the plasma membrane, mediating various cell-polarized phenomena including polar cell growth. Here, we investigated the involvement of Arabidopsis thaliana PCaP2, a plant-unique plasma membrane protein with phosphoinositide-binding activity, in PtdIns(4,5)P2 signaling for root hair tip growth. The long-root-hair phenotype of the pcap2 knockdown mutant was found to stem from its higher average root hair elongation rate compared with the wild type and to counteract the low average rate caused by a defect in the PtdIns(4,5)P2 -producing enzyme gene PIP5K3. On the plasma membrane of elongating root hairs, the PCaP2 promoter-driven PCaP2-green fluorescent protein (GFP), which complemented the pcap2 mutant phenotype, overlapped with the PtdIns(4,5)P2 marker 2xCHERRY-2xPHPLC in the subapical region, but not at the apex, suggesting that PCaP2 attenuates root hair elongation via PtdIns(4,5)P2 signaling on the subapical plasma membrane. Consistent with this, a GFP fusion with the PCaP2 phosphoinositide-binding domain PCaP2N23 , root hair-specific overexpression of which caused a low average root hair elongation rate, localized more intense to the subapical plasma membrane than to the apical plasma membrane similar to PCaP2-GFP. Inducibly overexpressed PCaP2-GFP, but not its derivative lacking the PCaP2N23 domain, replaced 2xCHERRY-2xPHPLC on the plasma membrane in root meristematic epidermal cells, and suppressed FM4-64 internalization in elongating root hairs. Moreover, inducibly overexpressed PCaP2 arrested an endocytic process of PIN2-GFP recycling. Based on these results, we conclude that PCaP2 functions as a negative modulator of PtdIns(4,5)P2 signaling on the subapical plasma membrane probably through competitive binding to PtdIns(4,5)P2 and attenuates root hair elongation.
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Affiliation(s)
- Mariko Kato
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
| | - Tomohiko Tsuge
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
| | - Masayoshi Maeshima
- Laboratory of Cell Dynamics, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Nagoya, Aichi, 464-8601, Japan
| | - Takashi Aoyama
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
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16
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Johnson MA, Harper JF, Palanivelu R. A Fruitful Journey: Pollen Tube Navigation from Germination to Fertilization. ANNUAL REVIEW OF PLANT BIOLOGY 2019; 70:809-837. [PMID: 30822112 DOI: 10.1146/annurev-arplant-050718-100133] [Citation(s) in RCA: 134] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
In flowering plants, pollen tubes undergo tip growth to deliver two nonmotile sperm to the ovule where they fuse with an egg and central cell to achieve double fertilization. This extended journey involves rapid growth and changes in gene activity that manage compatible interactions with at least seven different cell types. Nearly half of the genome is expressed in haploid pollen, which facilitates genetic analysis, even of essential genes. These unique attributes make pollen an ideal system with which to study plant cell-cell interactions, tip growth, cell migration, the modulation of cell wall integrity, and gene expression networks. We highlight the signaling systems required for pollen tube navigation and the potential roles of Ca2+ signals. The dynamics of pollen development make sexual reproduction highly sensitive to heat stress. Understanding this vulnerability may generate strategies to improve seed crop yields that are under threat from climate change.
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Affiliation(s)
- Mark A Johnson
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912, USA;
| | - Jeffrey F Harper
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Nevada 89557, USA;
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17
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Zhang S, Wang C, Xie M, Liu J, Kong Z, Su H. Actin Bundles in The Pollen Tube. Int J Mol Sci 2018; 19:ijms19123710. [PMID: 30469514 PMCID: PMC6321563 DOI: 10.3390/ijms19123710] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2018] [Revised: 11/18/2018] [Accepted: 11/19/2018] [Indexed: 12/31/2022] Open
Abstract
The angiosperm pollen tube delivers two sperm cells into the embryo sac through a unique growth strategy, named tip growth, to accomplish fertilization. A great deal of experiments have demonstrated that actin bundles play a pivotal role in pollen tube tip growth. There are two distinct actin bundle populations in pollen tubes: the long, rather thick actin bundles in the shank and the short, highly dynamic bundles near the apex. With the development of imaging techniques over the last decade, great breakthroughs have been made in understanding the function of actin bundles in pollen tubes, especially short subapical actin bundles. Here, we tried to draw an overall picture of the architecture, functions and underlying regulation mechanism of actin bundles in plant pollen tubes.
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Affiliation(s)
- Shujuan Zhang
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education College of Life Science, Northwest University, Xi'an 710069, China.
| | - Chunbo Wang
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education College of Life Science, Northwest University, Xi'an 710069, China.
| | - Min Xie
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education College of Life Science, Northwest University, Xi'an 710069, China.
| | - Jinyu Liu
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education College of Life Science, Northwest University, Xi'an 710069, China.
| | - Zhe Kong
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education College of Life Science, Northwest University, Xi'an 710069, China.
| | - Hui Su
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education College of Life Science, Northwest University, Xi'an 710069, China.
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18
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Golgi-localized LOT regulates trans-Golgi network biogenesis and pollen tube growth. Proc Natl Acad Sci U S A 2018; 115:12307-12312. [PMID: 30413616 DOI: 10.1073/pnas.1809206115] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The trans-Golgi network (TGN) is an essential tubular-vesicular organelle derived from the Golgi and functions as an independent sorting and trafficking hub within the cell. However, the molecular regulation of TGN biogenesis remains enigmatic. Here we identified an Arabidopsis mutant loss of TGN (lot) that is defective in TGN formation and sterile due to impaired pollen tube growth in the style. The mutation leads to overstacking of the Golgi cisternae and significant reduction in the number of TGNs and vesicles surrounding the Golgi in pollen, which is corroborated by the dispersed cytosolic distribution of TGN-localized proteins. Consistently, deposition of extracellular pectin and plasma membrane localization of kinases and phosphoinositide species are also impaired. Subcellular localization analysis suggests that LOT is localized on the periphery of the Golgi cisternae, but the mutation does not affect the localization of Golgi-resident proteins. Furthermore, the yeast complementation result suggests that LOT could functionally act as a component of the guanine nucleotide exchange factor (GEF) complex of small Rab GTPase Ypt6. Taken together, these findings suggest that LOT is a critical player for TGN biogenesis in the plant lineage.
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19
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Li G, Yang X, Zhang X, Song Y, Liang W, Zhang D. Rice Morphology Determinant-Mediated Actin Filament Organization Contributes to Pollen Tube Growth. PLANT PHYSIOLOGY 2018; 177:255-270. [PMID: 29581178 PMCID: PMC5933118 DOI: 10.1104/pp.17.01759] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 03/19/2018] [Indexed: 05/25/2023]
Abstract
For successful fertilization in angiosperms, rapid tip growth in pollen tubes delivers the male gamete into the ovules. The actin-binding protein-mediated organization of the actin cytoskeleton within the pollen tube plays a crucial role in this polarized process. However, the mechanism underlying the polarity of the actin filament (F-actin) array and behaviors in pollen tube growth remain largely unknown. Here, we demonstrate that an actin-organizing protein, Rice Morphology Determinant (RMD), a type II formin from rice (Oryza sativa), controls pollen tube growth by modulating the polarity and distribution of the F-actin array. The rice rmd mutant exhibits abnormal pollen tube growth and a decreased germination rate of the pollen grain in vitro and in vivo. The rmd pollen tubes display a disorganized F-actin pattern with disrupted apical actin density and shank longitudinal cable direction/arrangement, indicating the novel role of RMD in F-actin polarity during tip growth. Consistent with this role, RMD localizes at the tip of the rice pollen tube, which is essential for pollen tube growth and polarity as well as F-actin organization. Furthermore, the direction and characteristics of the RMD-guided F-actin array positively regulate the deposition of cell wall components and the pattern and velocity of cytoplasmic streaming during rice pollen tube growth. Collectively, our results suggest that RMD is essential for the spatial regulation of pollen tube growth via modulating F-actin organization and array orientation in rice. This work provides insights into tip-focused cell growth and polarity.
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Affiliation(s)
- Gang Li
- University of Adelaide-Shanghai Jiao Tong University Joint Laboratory for Plant Science and Breeding, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus, Urrbrae, South Australia 5064, Australia
| | - Xiujuan Yang
- University of Adelaide-Shanghai Jiao Tong University Joint Laboratory for Plant Science and Breeding, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus, Urrbrae, South Australia 5064, Australia
| | - Xiaoqing Zhang
- Joint International Research Laboratory of Metabolic and Developmental Sciences, Shanghai Jiao Tong University-University of Adelaide Joint Centre for Agriculture and Health, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yu Song
- Joint International Research Laboratory of Metabolic and Developmental Sciences, Shanghai Jiao Tong University-University of Adelaide Joint Centre for Agriculture and Health, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Wanqi Liang
- Joint International Research Laboratory of Metabolic and Developmental Sciences, Shanghai Jiao Tong University-University of Adelaide Joint Centre for Agriculture and Health, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Dabing Zhang
- University of Adelaide-Shanghai Jiao Tong University Joint Laboratory for Plant Science and Breeding, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus, Urrbrae, South Australia 5064, Australia
- Joint International Research Laboratory of Metabolic and Developmental Sciences, Shanghai Jiao Tong University-University of Adelaide Joint Centre for Agriculture and Health, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
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20
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Bibeau JP, Kingsley JL, Furt F, Tüzel E, Vidali L. F-Actin Mediated Focusing of Vesicles at the Cell Tip Is Essential for Polarized Growth. PLANT PHYSIOLOGY 2018; 176:352-363. [PMID: 28972078 PMCID: PMC5761772 DOI: 10.1104/pp.17.00753] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 09/26/2017] [Indexed: 05/18/2023]
Abstract
F-actin has been shown to be essential for tip growth in an array of plant models, including Physcomitrella patens One hypothesis is that diffusion can transport secretory vesicles, while actin plays a regulatory role during secretion. Alternatively, it is possible that actin-based transport is necessary to overcome vesicle transport limitations to sustain secretion. Therefore, a quantitative analysis of diffusion, secretion kinetics, and cell geometry is necessary to clarify the role of actin in polarized growth. Using fluorescence recovery after photobleaching analysis, we first show that secretory vesicles move toward and accumulate at the tip in an actin-dependent manner. We then depolymerized F-actin to decouple vesicle diffusion from actin-mediated transport and measured the diffusion coefficient and concentration of vesicles. Using these values, we constructed a theoretical diffusion-based model for growth, demonstrating that with fast-enough vesicle fusion kinetics, diffusion could support normal cell growth rates. We further refined our model to explore how experimentally extrapolated vesicle fusion kinetics and the size of the secretion zone limit diffusion-based growth. This model predicts that diffusion-mediated growth is dependent on the size of the region of exocytosis at the tip and that diffusion-based growth would be significantly slower than normal cell growth. To further explore the size of the secretion zone, we used a cell wall degradation enzyme cocktail and determined that the secretion zone is smaller than 6 μm in diameter at the tip. Taken together, our results highlight the requirement for active transport in polarized growth and provide important insight into vesicle secretion during tip growth.
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Affiliation(s)
- Jeffrey P Bibeau
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609
| | - James L Kingsley
- Department of Physics, Worcester Polytechnic Institute, Worcester, Massachusetts 01609
| | - Fabienne Furt
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609
| | - Erkan Tüzel
- Department of Physics, Worcester Polytechnic Institute, Worcester, Massachusetts 01609
| | - Luis Vidali
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609
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21
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Kf de Campos M, Schaaf G. The regulation of cell polarity by lipid transfer proteins of the SEC14 family. CURRENT OPINION IN PLANT BIOLOGY 2017; 40:158-168. [PMID: 29017091 DOI: 10.1016/j.pbi.2017.09.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 09/07/2017] [Accepted: 09/11/2017] [Indexed: 06/07/2023]
Abstract
SEC14 lipid transfer proteins are important regulators of phospholipid metabolism. Structural, genetic and cell biological studies in yeast suggest that they help phosphatidylinositol (PtdIns)/phosphoinositide (PIP) kinases to overcome their intrinsic inefficiency to recognize membrane-embedded substrate, thereby playing a key role in PIP homeostasis. Genomes of higher plants encode a high number and diversity of SEC14 proteins, often in combination with other domains. The Arabidopsis SEC14-Nlj16 protein AtSFH1, an important regulator of root hair development, plays an important role in the establishment of PIP microdomains. Key to this mechanism is a highly specific interaction of the Nlj16 domain with PtdIns(4,5)P2 and an interaction-triggered oligomerization of the protein. Nlj16/PtdIns(4,5)P2 interaction depends on a polybasic motif similar to those identified in other regulatory proteins.
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Affiliation(s)
- Marília Kf de Campos
- Institute of Crop Science and Resource Conservation, Department of Plant Nutrition, University of Bonn, Karlrobert-Kreiten-Strasse 13, 53115 Bonn, Germany.
| | - Gabriel Schaaf
- Institute of Crop Science and Resource Conservation, Department of Plant Nutrition, University of Bonn, Karlrobert-Kreiten-Strasse 13, 53115 Bonn, Germany.
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22
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Jung JY, Lee DW, Ryu SB, Hwang I, Schachtman DP. SCYL2 Genes Are Involved in Clathrin-Mediated Vesicle Trafficking and Essential for Plant Growth. PLANT PHYSIOLOGY 2017; 175:194-209. [PMID: 28751315 PMCID: PMC5580775 DOI: 10.1104/pp.17.00824] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Accepted: 07/24/2017] [Indexed: 05/10/2023]
Abstract
Protein transport between organelles is an essential process in all eukaryotic cells and is mediated by the regulation of processes such as vesicle formation, transport, docking, and fusion. In animals, SCY1-LIKE2 (SCYL2) binds to clathrin and has been shown to play roles in trans-Golgi network-mediated clathrin-coated vesicle trafficking. Here, we demonstrate that SCYL2A and SCYL2B, which are Arabidopsis (Arabidopsis thaliana) homologs of animal SCYL2, are vital for plant cell growth and root hair development. Studies of the SCYL2 isoforms using multiple single or double loss-of-function alleles show that SCYL2B is involved in root hair development and that SCYL2A and SCYL2B are essential for plant growth and development and act redundantly in those processes. Quantitative reverse transcription-polymerase chain reaction and a β-glucuronidase-aided promoter assay show that SCYL2A and SCYL2B are differentially expressed in various tissues. We also show that SCYL2 proteins localize to the Golgi, trans-Golgi network, and prevacuolar compartment and colocalize with Clathrin Heavy Chain1 (CHC1). Furthermore, bimolecular fluorescence complementation and coimmunoprecipitation data show that SCYL2B interacts with CHC1 and two Soluble NSF Attachment Protein Receptors (SNAREs): Vesicle Transport through t-SNARE Interaction11 (VTI11) and VTI12. Finally, we present evidence that the root hair tip localization of Cellulose Synthase-Like D3 is dependent on SCYL2B. These findings suggest the role of SCYL2 genes in plant cell developmental processes via clathrin-mediated vesicle membrane trafficking.
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Affiliation(s)
- Ji-Yul Jung
- Department of Plant Molecular Biology, University of Lausanne, Lausanne 1015, Switzerland
| | - Dong Wook Lee
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Stephen Beungtae Ryu
- Plant Systems Engineering Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-806, Korea
| | - Inhwan Hwang
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Daniel P Schachtman
- Department of Agronomy and Horticulture, University of Nebraska, Lincoln, Nebraska 68588
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23
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Hirano T, Stecker K, Munnik T, Xu H, Sato MH. Visualization of Phosphatidylinositol 3,5-Bisphosphate Dynamics by a Tandem ML1N-Based Fluorescent Protein Probe in Arabidopsis. PLANT & CELL PHYSIOLOGY 2017; 58:1185-1195. [PMID: 28158631 PMCID: PMC5921506 DOI: 10.1093/pcp/pcx011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2016] [Accepted: 01/13/2017] [Indexed: 05/24/2023]
Abstract
Phosphatidylinositol 3,5-bisphosphate [PI(3,5)P2] is a low-abundance phospholipid known to be associated with a wide variety of physiological functions in plants. However, the localization and dynamics of PI(3,5)P2 in plant cells remain largely unknown, partially due to the lack of an effective fluorescent probe. Using Arabidopsis transgenic plant expressing the PI(3,5)P2-labeling fluorescent probe (tagRFP-ML1N*2) developed based on a tandem repeat of the cytosolic phosphoinositide-interacting domain (ML1N) of the mammalian lysosomal transient receptor potential cation channel, Mucolipin 1 (TRPML1), here we show that PI(3,5)P2 is predominantly localized on the limited membranes of the FAB1- and SNX1-positive late endosomes, but rarely localized on the membranes of plant vacuoles or trans-Golgi network/early endosomes of cortical cells of the root differentiation zone. The late endosomal localization of tagRFP-ML1N*2 is reduced or abolished by pharmacological inhibition or genetic knockdown of expression of genes encoding PI(3,5)P2-synthesizing enzymes, FAB1A/B, but markedly increased with FAB1A overexpression. Notably, reactive oxygen species (ROS) significantly increase late endosomal levels of PI(3,5)P2. Thus, tandem ML1N-based PI(3,5)P2 probes can reliably monitor intracellular dynamics of PI(3,5)P2 in Arabidopsis cells with less binding activity to other endomembrane organelles.
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Affiliation(s)
- Tomoko Hirano
- Laboratory of Cellular Dynamics, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Shimogamo-nakaragi-cho, Sakyo-ku, Kyoto, 606-8522 Japan
| | - Kelly Stecker
- Biotechnology Center, University of Wisconsin, Madison, WI 53706, USA
| | - Teun Munnik
- Section of Plant Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Science park 904, 1098 XH Amsterdam 94216, The Netherlands
| | - Haoxing Xu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Masa H. Sato
- Laboratory of Cellular Dynamics, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Shimogamo-nakaragi-cho, Sakyo-ku, Kyoto, 606-8522 Japan
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24
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Kang E, Zheng M, Zhang Y, Yuan M, Yalovsky S, Zhu L, Fu Y. The Microtubule-Associated Protein MAP18 Affects ROP2 GTPase Activity during Root Hair Growth. PLANT PHYSIOLOGY 2017; 174:202-222. [PMID: 28314794 PMCID: PMC5411128 DOI: 10.1104/pp.16.01243] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 03/14/2017] [Indexed: 05/24/2023]
Abstract
Establishment and maintenance of the polar site are important for root hair tip growth. We previously reported that Arabidopsis (Arabidopsis thaliana) MICROTUBULE-ASSOCIATED PROTEIN18 (MAP18) functions in controlling the direction of pollen tube growth and root hair elongation. Additionally, the Rop GTPase ROP2 was reported as a positive regulator of both root hair initiation and tip growth in Arabidopsis. Both loss of function of ROP2 and knockdown of MAP18 lead to a decrease in root hair length, whereas overexpression of either MAP18 or ROP2 causes multiple tips or a branching hair phenotype. However, it is unclear whether MAP18 and ROP2 coordinately regulate root hair growth. In this study, we demonstrate that MAP18 and ROP2 interact genetically and functionally. MAP18 interacts physically with ROP2 in vitro and in vivo and preferentially binds to the inactive form of the ROP2 protein. MAP18 promotes ROP2 activity during root hair tip growth. Further investigation revealed that MAP18 competes with RhoGTPase GDP DISSOCIATION INHIBITOR1/SUPERCENTIPEDE1 for binding to ROP2, in turn affecting the localization of active ROP2 in the plasma membrane of the root hair tip. These results reveal a novel function of MAP18 in the regulation of ROP2 activation during root hair growth.
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Affiliation(s)
- Erfang Kang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China (E.K., M.Z., Y.Z., L.Z., Y.F.); and
- Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel (S.Y.)
| | - Mingzhi Zheng
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China (E.K., M.Z., Y.Z., L.Z., Y.F.); and
- Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel (S.Y.)
| | - Yan Zhang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China (E.K., M.Z., Y.Z., L.Z., Y.F.); and
- Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel (S.Y.)
| | - Ming Yuan
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China (E.K., M.Z., Y.Z., L.Z., Y.F.); and
- Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel (S.Y.)
| | - Shaul Yalovsky
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China (E.K., M.Z., Y.Z., L.Z., Y.F.); and
- Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel (S.Y.)
| | - Lei Zhu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China (E.K., M.Z., Y.Z., L.Z., Y.F.); and
- Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel (S.Y.)
| | - Ying Fu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China (E.K., M.Z., Y.Z., L.Z., Y.F.); and
- Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel (S.Y.)
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25
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Wang H, Lan P, Shen RF. Integration of transcriptomic and proteomic analysis towards understanding the systems biology of root hairs. Proteomics 2016; 16:877-93. [PMID: 26749523 DOI: 10.1002/pmic.201500265] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 12/28/2015] [Accepted: 01/05/2016] [Indexed: 11/11/2022]
Abstract
Plants and other multicellular organisms consist of many types of specialized cells. Systems-wide exploration of large-scale information from singe cell level is essential to understand how cell works. Root hairs, tubular-shaped outgrowths from root epidermal cells, play important roles in the acquisition of nutrients and water, in the interaction with microbe, and in plant anchorage, and represent an ideal model to study the biology of a single cell type. Single cell sampling combined with omics approaches has been applied to study plant root hairs. This review emphasizes the integration of omics approaches towards understanding the systems biology of root hairs, unraveling the common and plant species-specific properties of root hairs, as well as the concordance of protein and transcript abundance. Understanding plant root hair biology by mining the integrated omics data will provide a way to know how a single cell differentiates, elongates, and functions, which might help molecularly modify crops for developing sustainable agriculture practices.
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Affiliation(s)
- Han Wang
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, P. R. China
| | - Ping Lan
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, P. R. China
| | - Ren Fang Shen
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, P. R. China
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Galindo-Trigo S, Gray JE, Smith LM. Conserved Roles of CrRLK1L Receptor-Like Kinases in Cell Expansion and Reproduction from Algae to Angiosperms. FRONTIERS IN PLANT SCIENCE 2016; 7:1269. [PMID: 27621737 PMCID: PMC5002434 DOI: 10.3389/fpls.2016.01269] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 08/10/2016] [Indexed: 05/20/2023]
Abstract
Receptor-like kinases (RLKs) are regulators of plant development through allowing cells to sense their extracellular environment. They facilitate detection of local endogenous signals, in addition to external biotic and abiotic stimuli. The Catharanthus roseus RLK1-like (CrRLK1L) protein kinase subfamily, which contains FERONIA, plays a central role in regulating fertilization and in cell expansion mechanisms such as cell elongation and tip growth, as well as having indirect links to plant-pathogen interactions. Several components of CrRLK1L signaling pathways have been identified, including an extracellular ligand, coreceptors, and downstream signaling elements. The presence and abundance of the CrRLK1L proteins in the plant kingdom suggest an origin within the Streptophyta lineage, with a notable increase in prevalence in the seeded land plants. Given the function of the sole CrRLK1L protein in a charophycean alga, the possibility of a conserved role in detection and/or regulation of cell wall integrity throughout the Strephtophytes is discussed. Orthologs of signaling pathway components are also present in extant representatives of non-vascular land plants and early vascular land plants including the liverwort Marchantia polymorpha, the moss Physcomitrella patens and the lycophyte Selaginella moellendorffii. Deciphering the roles in development of the CrRLK1L protein kinases in early diverging land plants will provide insights into their ancestral function, furthering our understanding of this diversified subfamily of receptors in higher plants.
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Affiliation(s)
| | - Julie E. Gray
- Department of Molecular Biology and Biotechnology, University of SheffieldSheffield, UK
| | - Lisa M. Smith
- Department of Animal and Plant Sciences, University of SheffieldSheffield, UK
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Zhao YL, Zhou TT, Guo HS. Hyphopodium-Specific VdNoxB/VdPls1-Dependent ROS-Ca2+ Signaling Is Required for Plant Infection by Verticillium dahliae. PLoS Pathog 2016; 12:e1005793. [PMID: 27463643 PMCID: PMC4962994 DOI: 10.1371/journal.ppat.1005793] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 07/06/2016] [Indexed: 11/18/2022] Open
Abstract
Verticillium dahliae is a phytopathogenic fungus obligate in root infection. A few hyphopodia differentiate from large numbers of hyphae after conidia germination on the root surface for further infection. However, the molecular features and role of hyphopodia in the pathogenicity of V. dahliae remain elusive. In this study, we found that the VdPls1, a tetraspanin, and the VdNoxB, a catalytic subunit of membrane-bound NADPH oxidases for reactive oxygen species (ROS) production, were specifically expressed in hyphopodia. VdPls1 and VdNoxB highly co-localize with the plasma membrane at the base of hyphopodia, where ROS and penetration pegs are generated. Mutant strains, VdΔnoxb and VdΔpls1, in which VdPls1 and VdNoxB were deleted, respectively, developed defective hyphpodia incapable of producing ROS and penetration pegs. Defective plasma membrane localization of VdNoxB in VdΔpls1 demonstrates that VdPls1 functions as an adaptor protein for the recruitment and activation of the VdNoxB. Furthermore, in VdΔnoxb and VdΔpls1, tip-high Ca2+ accumulation was impaired in hyphopodia, but not in vegetative hyphal tips. Moreover, nuclear targeting of VdCrz1 and activation of calcineurin-Crz1 signaling upon hyphopodium induction in wild-type V. dahliae was impaired in both knockout mutants, indicating that VdPls1/VdNoxB-dependent ROS was specifically required for tip-high Ca2+ elevation in hyphopodia to activate the transcription factor VdCrz1 in the regulation of penetration peg formation. Together with the loss of virulence of VdΔnoxb and VdΔpls1, which are unable to initiate colonization in cotton plants, our data demonstrate that VdNoxB/VdPls1-mediated ROS production activates VdCrz1 signaling through Ca2+ elevation in hyphopodia, infectious structures of V. dahliae, to regulate penetration peg formation during the initial colonization of cotton roots.
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Affiliation(s)
- Yun-Long Zhao
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Microbiology, Beijing, China
- University of the Chinese Academy of Sciences, Beijing, China
| | - Ting-Ting Zhou
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Microbiology, Beijing, China
- University of the Chinese Academy of Sciences, Beijing, China
| | - Hui-Shan Guo
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Microbiology, Beijing, China
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Qiu A, Liu Z, Li J, Chen Y, Guan D, He S. The Ectopic Expression of CaRop1 Modulates the Response of Tobacco Plants to Ralstonia solanacearum and Aphids. FRONTIERS IN PLANT SCIENCE 2016; 7:1177. [PMID: 27551287 PMCID: PMC4976107 DOI: 10.3389/fpls.2016.01177] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 07/21/2016] [Indexed: 05/07/2023]
Abstract
In plants, Rho-related GTPases (Rops) are versatile molecular switches that regulate various biological processes, although their exact roles are not fully understood. Herein, we provide evidence that the ectopic expression of a Rop derived from Capsicum annuum, designated CaRop1, in tobacco plants modulates the response of these plants to Ralstonia solanacearum or aphid attack. The deduced amino acid sequence of CaRop1 harbors a conserved Rho domain and is highly homologous to Rops of other plant species. Transient expression of a CaRop1-GFP fusion protein in Nicotiana benthamiana leaf epidermal cells revealed localization of the GFP signal to the plasma membrane, cytoplasm, and nucleus. Overexpression (OE) of the wild-type CaRop1 or its dominant-negative mutant (DN-CaRop1) conferred substantial resistance to R. solanacearum infection and aphid attack, and this effect was accompanied by enhanced transcriptional expression of the hypersensitive-reaction marker gene HSR201; the jasmonic acid (JA)-responsive PR1b and LOX1; the insect resistance-associated NtPI-I, NtPI-II, and NtTPI; the ethylene (ET) production-associated NtACS1; and NPK1, a mitogen-activated protein kinase kinase kinase (MAPKKK) that interferes with N-, Bs2-, and Rx-mediated disease resistance. In contrast, OE of the constitutively active mutant of CaRop1(CA-CaRop1) enhanced susceptibility of the transgenic tobacco plants to R. solanacearum infection and aphid attack and downregulated or sustained the expression of HSR201, PR1b, NPK1, NtACS1, NtPI-I, NtPI-II, and NtTPI. These results collectively suggest that CaRop1 acts as a signaling switch in the crosstalk between Solanaceaes's response to R. solanacearum infection and aphid attack possibly via JA/ET-mediated signaling machinery.
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Affiliation(s)
- Ailian Qiu
- College of Life Science, Fujian Agriculture and Forestry University, FuzhouChina
- Key Laboratory of Crop Genetics and Breeding and Comprehensive Utilization, Ministry of Education/Fujian Agriculture and Forestry University, FuzhouChina
| | - Zhiqin Liu
- College of Life Science, Fujian Agriculture and Forestry University, FuzhouChina
- Key Laboratory of Crop Genetics and Breeding and Comprehensive Utilization, Ministry of Education/Fujian Agriculture and Forestry University, FuzhouChina
- College of Crop Science, Fujian Agriculture and Forestry University, FuzhouChina
| | - Jiazhi Li
- College of Life Science, Fujian Agriculture and Forestry University, FuzhouChina
- Key Laboratory of Crop Genetics and Breeding and Comprehensive Utilization, Ministry of Education/Fujian Agriculture and Forestry University, FuzhouChina
| | - Yanshen Chen
- College of Life Science, Fujian Agriculture and Forestry University, FuzhouChina
- Key Laboratory of Crop Genetics and Breeding and Comprehensive Utilization, Ministry of Education/Fujian Agriculture and Forestry University, FuzhouChina
| | - Deyi Guan
- Key Laboratory of Crop Genetics and Breeding and Comprehensive Utilization, Ministry of Education/Fujian Agriculture and Forestry University, FuzhouChina
- College of Crop Science, Fujian Agriculture and Forestry University, FuzhouChina
| | - Shuilin He
- College of Life Science, Fujian Agriculture and Forestry University, FuzhouChina
- Key Laboratory of Crop Genetics and Breeding and Comprehensive Utilization, Ministry of Education/Fujian Agriculture and Forestry University, FuzhouChina
- College of Crop Science, Fujian Agriculture and Forestry University, FuzhouChina
- *Correspondence: Shuilin He,
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Jiménez-Quesada MJ, Traverso JÁ, Alché JDD. NADPH Oxidase-Dependent Superoxide Production in Plant Reproductive Tissues. FRONTIERS IN PLANT SCIENCE 2016; 7:359. [PMID: 27066025 PMCID: PMC4815025 DOI: 10.3389/fpls.2016.00359] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Accepted: 03/07/2016] [Indexed: 05/02/2023]
Abstract
In the life cycle of a flowering plant, the male gametophyte (pollen grain) produced in the anther reaches the stigmatic surface and initiates the pollen-pistil interaction, an important step in plant reproduction, which ultimately leads to the delivery of two sperm cells to the female gametophyte (embryo sac) inside the ovule. The pollen tube undergoes a strictly apical expansion characterized by a high growth rate, whose targeting should be tightly regulated. A continuous exchange of signals therefore takes place between the haploid pollen and diploid tissue of the pistil until fertilization. In compatible interactions, theses processes result in double fertilization to form a zygote (2n) and the triploid endosperm. Among the large number of signaling mechanisms involved, the redox network appears to be particularly important. Respiratory burst oxidase homologs (Rbohs) are superoxide-producing enzymes involved in a broad range of processes in plant physiology. In this study, we review the latest findings on understanding Rboh activity in sexual plant reproduction, with a particular focus on the male gametophyte from the anther development stages to the crowning point of fertilization. Rboh isoforms have been identified in both the male and female gametophyte and have proven to be tightly regulated. Their role at crucial points such as proper growth of pollen tube, self-incompatibility response and eventual fertilization is discussed.
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Affiliation(s)
- María J. Jiménez-Quesada
- Plant Reproductive Biology Laboratory, Department of Biochemistry, Cell and Molecular Biology of Plants, Estación Experimental del Zaidín, Spanish National Research Council (CSIC)Granada, Spain
| | - José Á. Traverso
- Department of Cell Biology, Faculty of Sciences, University of GranadaGranada, Spain
| | - Juan de Dios Alché
- Plant Reproductive Biology Laboratory, Department of Biochemistry, Cell and Molecular Biology of Plants, Estación Experimental del Zaidín, Spanish National Research Council (CSIC)Granada, Spain
- *Correspondence: Juan de Dios Alché,
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Zhang Y, Kang E, Yuan M, Fu Y, Zhu L. PCaP2 regulates nuclear positioning in growing Arabidopsis thaliana root hairs by modulating filamentous actin organization. PLANT CELL REPORTS 2015; 34:1317-30. [PMID: 25929794 DOI: 10.1007/s00299-015-1789-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2015] [Revised: 03/23/2015] [Accepted: 03/31/2015] [Indexed: 05/10/2023]
Abstract
PCaP2 plays a key role in maintaining the nucleus at a relatively fixed distance from the apex during root hair growth by modulating actin filaments. During root hair growth, the nucleus localizes at a relatively fixed distance from the apex. In Arabidopsis thaliana, the position of the nucleus is mainly dependent on the configuration of microfilaments (filamentous actin). However, the mechanisms underlying the regulation of actin dynamics and organization for nuclear positioning are largely unknown. In the present study, we demonstrated that plasma membrane-associated Ca(2+) binding protein 2 (PCaP2) influences the position of the nucleus during root hair growth. Abnormal expression of PCaP2 in pcap2 and PCaP2 over-expression plants led to the disorganization of actin filaments, rather than microtubules, in the apex and sub-apical regions of root hairs, which resulted in aberrant root hair growth patterns and misplaced nuclei. Analyses using a PCaP2 mutant protein revealed that actin-severing activity is essential for the function of PCaP2 in root hairs. We demonstrated that PCaP2 plays a key role in maintaining nuclear position in growing root hairs by modulating actin filaments.
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Affiliation(s)
- Yan Zhang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
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31
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Sundaresan S, Philosoph-Hadas S, Riov J, Belausov E, Kochanek B, Tucker ML, Meir S. Abscission of flowers and floral organs is closely associated with alkalization of the cytosol in abscission zone cells. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:1355-68. [PMID: 25504336 PMCID: PMC4339595 DOI: 10.1093/jxb/eru483] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
In vivo changes in the cytosolic pH of abscission zone (AZ) cells were visualized using confocal microscopic detection of the fluorescent pH-sensitive and intracellularly trapped dye, 2',7'-bis-(2-carboxyethyl)-5(and-6)-carboxyfluorescein (BCECF), driven by its acetoxymethyl ester. A specific and gradual increase in the cytosolic pH of AZ cells was observed during natural abscission of flower organs in Arabidopsis thaliana and wild rocket (Diplotaxis tenuifolia), and during flower pedicel abscission induced by flower removal in tomato (Solanum lycopersicum Mill). The alkalization pattern in the first two species paralleled the acceleration or inhibition of flower organ abscission induced by ethylene or its inhibitor 1-methylcyclopropene (1-MCP), respectively. Similarly, 1-MCP pre-treatment of tomato inflorescence explants abolished the pH increase in AZ cells and pedicel abscission induced by flower removal. Examination of the pH changes in the AZ cells of Arabidopsis mutants defective in both ethylene-induced (ctr1, ein2, eto4) and ethylene-independent (ida, nev7, dab5) abscission pathways confirmed these results. The data indicate that the pH changes in the AZ cells are part of both the ethylene-sensitive and -insensitive abscission pathways, and occur concomitantly with the execution of organ abscission. pH can affect enzymatic activities and/or act as a signal for gene expression. Changes in pH during abscission could occur via regulation of transporters in AZ cells, which might affect cytosolic pH. Indeed, four genes associated with pH regulation, vacuolar H(+)-ATPase, putative high-affinity nitrate transporter, and two GTP-binding proteins, were specifically up-regulated in tomato flower AZ following abscission induction, and 1-MCP reduced or abolished the increased expression.
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Affiliation(s)
- Srivignesh Sundaresan
- Department of Postharvest Science of Fresh Produce, Agricultural Research Organization (ARO), The Volcani Center, Bet-Dagan 5025001, Israel The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 7610001, Israel
| | - Sonia Philosoph-Hadas
- Department of Postharvest Science of Fresh Produce, Agricultural Research Organization (ARO), The Volcani Center, Bet-Dagan 5025001, Israel
| | - Joseph Riov
- The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 7610001, Israel
| | - Eduard Belausov
- Department of Ornamental Horticulture, Agricultural Research Organization (ARO), The Volcani Center, Bet-Dagan 5025001, Israel
| | - Betina Kochanek
- Department of Postharvest Science of Fresh Produce, Agricultural Research Organization (ARO), The Volcani Center, Bet-Dagan 5025001, Israel
| | - Mark L Tucker
- Soybean Genomics and Improvement Laboratory, USDA-ARS, Beltsville, MD 20705, USA
| | - Shimon Meir
- Department of Postharvest Science of Fresh Produce, Agricultural Research Organization (ARO), The Volcani Center, Bet-Dagan 5025001, Israel
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Vogler F, Konrad SSA, Sprunck S. Knockin' on pollen's door: live cell imaging of early polarization events in germinating Arabidopsis pollen. FRONTIERS IN PLANT SCIENCE 2015; 6:246. [PMID: 25954283 PMCID: PMC4404733 DOI: 10.3389/fpls.2015.00246] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 03/27/2015] [Indexed: 05/20/2023]
Abstract
Pollen tubes are an excellent system for studying the cellular dynamics and complex signaling pathways that coordinate polarized tip growth. Although several signaling mechanisms acting in the tip-growing pollen tube have been described, our knowledge on the subcellular and molecular events during pollen germination and growth site selection at the pollen plasma membrane is rather scarce. To simultaneously track germinating pollen from up to 12 genetically different plants we developed an inexpensive and easy mounting technique, suitable for every standard microscope setup. We performed high magnification live-cell imaging during Arabidopsis pollen activation, germination, and the establishment of pollen tube tip growth by using fluorescent marker lines labeling either the pollen cytoplasm, vesicles, the actin cytoskeleton or the sperm cell nuclei and membranes. Our studies revealed distinctive vesicle and F-actin polarization during pollen activation and characteristic growth kinetics during pollen germination and pollen tube formation. Initially, the germinating Arabidopsis pollen tube grows slowly and forms a uniform roundish bulge, followed by a transition phase with vesicles heavily accumulating at the growth site before switching to rapid tip growth. Furthermore, we found the two sperm cells to be transported into the pollen tube after the phase of rapid tip growth has been initiated. The method presented here is suitable to quantitatively study subcellular events during Arabidopsis pollen germination and growth, and for the detailed analysis of pollen mutants with respect to pollen polarization, bulging, or growth site selection at the pollen plasma membrane.
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Affiliation(s)
- Frank Vogler
- Cell Biology and Plant Biochemistry, Biochemie-Zentrum RegensburgUniversity of Regensburg, Regensburg Germany
| | - Sebastian S. A. Konrad
- Faculty of Biology, Institute of Genetics, Ludwig-Maximilians-University of MunichMartinsried, Germany
| | - Stefanie Sprunck
- Cell Biology and Plant Biochemistry, Biochemie-Zentrum RegensburgUniversity of Regensburg, Regensburg Germany
- *Correspondence: Stefanie Sprunck, Department of Cell Biology and Plant Biochemistry, University of Regensburg, Universitaetsstrasse 31, 93053 Regensburg, Germany
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Nagawa S, Xu T, Yang Z. RHO GTPase in plants: Conservation and invention of regulators and effectors. Small GTPases 2014; 1:78-88. [PMID: 21686259 DOI: 10.4161/sgtp.1.2.14544] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Revised: 12/13/2010] [Accepted: 12/20/2010] [Indexed: 12/30/2022] Open
Abstract
Plants possess a single subfamily of Rho GTPases, ROP, which does usual things as do Rho-family GTPases in animal and fungal systems, namely participating in the spatial control of cellular processes by signaling to the cytoskeleton and vesicular trafficking. As one would expect, ROPs are modulated by conserved regulators such as DHR2-type GEFs, RhoGAPs and Rho GDIs. What is surprising is that plants have invented new regulators such as PRONE-type GEFs (known as RopGEFs) and effectors such as RICs and ICRs/RIPs in the regulation of the cytoskeleton and vesicular trafficking. This review will discuss recent work on characterizing ROP regulators and effectors as well as addressing why and how a mixture of conserved and novel Rho signaling mechanisms is utilized to modulate fundamental cellular processes such as cytoskeletal dynamics/reorganization and vesicular trafficking.
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Affiliation(s)
- Shingo Nagawa
- Center for Plant Cell Biology; Department of Botany and Plant Sciences; University of California; Riverside, CA USA
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Rishmawi L, Sun H, Schneeberger K, Hülskamp M, Schrader A. Rapid identification of a natural knockout allele of ARMADILLO REPEAT-CONTAINING KINESIN1 that causes root hair branching by mapping-by-sequencing. PLANT PHYSIOLOGY 2014; 166:1280-7. [PMID: 25248719 PMCID: PMC4226369 DOI: 10.1104/pp.114.244046] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
In Arabidopsis (Arabidopsis thaliana), branched root hairs are an indicator of defects in root hair tip growth. Among 62 accessions, one accession (Heiligkreuztal2 [HKT2.4]) displayed branched root hairs, suggesting that this accession carries a mutation in a gene of importance for tip growth. We determined 200- to 300-kb mapping intervals using a mapping-by-sequencing approach of F2 pools from crossings of HKT2.4 with three different accessions. The intersection of these mapping intervals was 80 kb in size featuring not more than 36 HKT2.4-specific single nucleotide polymorphisms, only two of which changed the coding potential of genes. Among them, we identified the causative single nucleotide polymorphism changing a splicing site in ARMADILLO REPEAT-CONTAINING KINESIN1. The applied strategies have the potential to complement statistical methods in high-throughput phenotyping studies using different natural accessions to identify causative genes for distinct phenotypes represented by only one or a few accessions.
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Affiliation(s)
- Louai Rishmawi
- Botanical Institute (L.R., M.H., A.S.) and Cluster of Excellence on Plant Sciences (L.R., M.H.), University of Cologne, Cologne Biocenter, D-50674 Cologne, Germany; andDepartment for Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany (H.S., K.S.)
| | - Hequan Sun
- Botanical Institute (L.R., M.H., A.S.) and Cluster of Excellence on Plant Sciences (L.R., M.H.), University of Cologne, Cologne Biocenter, D-50674 Cologne, Germany; andDepartment for Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany (H.S., K.S.)
| | - Korbinian Schneeberger
- Botanical Institute (L.R., M.H., A.S.) and Cluster of Excellence on Plant Sciences (L.R., M.H.), University of Cologne, Cologne Biocenter, D-50674 Cologne, Germany; andDepartment for Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany (H.S., K.S.)
| | - Martin Hülskamp
- Botanical Institute (L.R., M.H., A.S.) and Cluster of Excellence on Plant Sciences (L.R., M.H.), University of Cologne, Cologne Biocenter, D-50674 Cologne, Germany; andDepartment for Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany (H.S., K.S.)
| | - Andrea Schrader
- Botanical Institute (L.R., M.H., A.S.) and Cluster of Excellence on Plant Sciences (L.R., M.H.), University of Cologne, Cologne Biocenter, D-50674 Cologne, Germany; andDepartment for Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany (H.S., K.S.)
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Becker JD, Takeda S, Borges F, Dolan L, Feijó JA. Transcriptional profiling of Arabidopsis root hairs and pollen defines an apical cell growth signature. BMC PLANT BIOLOGY 2014; 14:197. [PMID: 25080170 PMCID: PMC4236730 DOI: 10.1186/s12870-014-0197-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Accepted: 07/14/2014] [Indexed: 05/20/2023]
Abstract
BACKGROUND Current views on the control of cell development are anchored on the notion that phenotypes are defined by networks of transcriptional activity. The large amounts of information brought about by transcriptomics should allow the definition of these networks through the analysis of cell-specific transcriptional signatures. Here we test this principle by applying an analogue to comparative anatomy at the cellular level, searching for conserved transcriptional signatures, or conserved small gene-regulatory networks (GRNs) on root hairs (RH) and pollen tubes (PT), two filamentous apical growing cells that are a striking example of conservation of structure and function in plants. RESULTS We developed a new method for isolation of growing and mature root hair cells, analysed their transcriptome by microarray analysis, and further compared it with pollen and other single cell transcriptomics data. Principal component analysis shows a statistical relation between the datasets of RHs and PTs which is suggestive of a common transcriptional profile pattern for the apical growing cells in a plant, with overlapping profiles and clear similarities at the level of small GTPases, vesicle-mediated transport and various specific metabolic responses. Furthermore, cis-regulatory element analysis of co-regulated genes between RHs and PTs revealed conserved binding sequences that are likely required for the expression of genes comprising the apical signature. This included a significant occurrence of motifs associated to a defined transcriptional response upon anaerobiosis. CONCLUSIONS Our results suggest that maintaining apical growth mechanisms synchronized with energy yielding might require a combinatorial network of transcriptional regulation. We propose that this study should constitute the foundation for further genetic and physiological dissection of the mechanisms underlying apical growth of plant cells.
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Affiliation(s)
- Jörg D Becker
- Instituto Gulbenkian de Ciência, 2780-156, Oeiras, Portugal
| | - Seiji Takeda
- Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, UK
- Present address: Cell and Genome Biology, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kitaina-Yazuma Oji 74, Seika-cho, Soraku-gun, Kyoto 619-0244, Japan
| | - Filipe Borges
- Instituto Gulbenkian de Ciência, 2780-156, Oeiras, Portugal
- Present address: Cold Spring Harbor Laboratory, Cold Spring Harbor 11724, NY, USA
| | - Liam Dolan
- Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, UK
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
| | - José A Feijó
- Instituto Gulbenkian de Ciência, 2780-156, Oeiras, Portugal
- Department of Cell Biology and Molecular Genetics, University of Maryland, 0118 BioScience Research Bldg, College Park 20742-5815, MD, USA
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Kawano Y, Fujiwara T, Yao A, Housen Y, Hayashi K, Shimamoto K. Palmitoylation-dependent membrane localization of the rice resistance protein pit is critical for the activation of the small GTPase OsRac1. J Biol Chem 2014; 289:19079-88. [PMID: 24841201 DOI: 10.1074/jbc.m114.569756] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Nucleotide binding domain and leucine-rich repeat (NLR)-containing family proteins function as intracellular immune sensors in both plants and animals. In plants, the downstream components activated by NLR family proteins and the immune response mechanisms induced by these downstream molecules are largely unknown. We have previously found that the small GTPase OsRac1, which acts as a molecular switch in rice immunity, is activated by Pit, an NLR-type resistance (R) protein to rice blast fungus, and this activation plays critical roles in Pit-mediated immunity. However, the sites and mechanisms of activation of Pit in vivo remain unknown. To clarify the mechanisms involved in the localization of Pit, we searched for consensus sequences in Pit that specify membrane localization and found a pair of potential palmitoylation sites in the N-terminal coiled-coil region. Although wild-type Pit was localized mainly to the plasma membrane, this membrane localization was compromised in a palmitoylation-deficient mutant of Pit. The palmitoylation-deficient Pit displayed significantly lower affinity for OsRac1 on the plasma membrane, thereby resulting in failures of the Pit-mediated cell death, the production of reactive oxygen species, and disease resistance to rice blast fungus. These results indicate that palmitoylation-dependent membrane localization of Pit is required for the interaction with and the activation of OsRac1 and that OsRac1 activation by Pit is vital for Pit-mediated disease resistance to rice blast fungus.
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Affiliation(s)
- Yoji Kawano
- From the Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan and
| | - Tadashi Fujiwara
- From the Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan and
| | - Ai Yao
- From the Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan and
| | - Yusuke Housen
- From the Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan and
| | - Keiko Hayashi
- National Agricultural Research Center, National Agriculture and Food Research Organization, 3-1-1 Kannondai, Tsukuba, Ibaraki 305-8666, Japan
| | - Ko Shimamoto
- From the Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan and
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Abstract
ROPs (Rho of plants) belong to a large family of plant-specific Rho-like small GTPases that function as essential molecular switches to control diverse cellular processes including cytoskeleton organization, cell polarization, cytokinesis, cell differentiation and vesicle trafficking. Although the machineries of vesicle trafficking and cell polarity in plants have been individually well addressed, how ROPs co-ordinate those processes is still largely unclear. Recent progress has been made towards an understanding of the co-ordination of ROP signalling and trafficking of PIN (PINFORMED) transporters for the plant hormone auxin in both root and leaf pavement cells. PIN transporters constantly shuttle between the endosomal compartments and the polar plasma membrane domains, therefore the modulation of PIN-dependent auxin transport between cells is a main developmental output of ROP-regulated vesicle trafficking. The present review focuses on these cellular mechanisms, especially the integration of ROP-based vesicle trafficking and plant cell polarity.
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Braidwood L, Breuer C, Sugimoto K. My body is a cage: mechanisms and modulation of plant cell growth. THE NEW PHYTOLOGIST 2014; 201:388-402. [PMID: 24033322 DOI: 10.1111/nph.12473] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2013] [Accepted: 08/01/2013] [Indexed: 05/19/2023]
Abstract
388 I. 388 II. 389 III. 389 IV. 390 V. 391 VI. 393 VII. 394 VIII. 398 399 References 399 SUMMARY: The wall surrounding plant cells provides protection from abiotic and biotic stresses, and support through the action of turgor pressure. However, the presence of this strong elastic wall also prevents cell movement and resists cell growth. This growth can be likened to extending a house from the inside, using extremely high pressures to push out the walls. Plants must increase cell volume in order to explore their environment, acquire nutrients and reproduce. Cell wall material must stretch and flow in a controlled manner and, concomitantly, new cell wall material must be deposited at the correct rate and site to prevent wall and cell rupture. In this review, we examine biomechanics, cell wall structure and growth regulatory networks to provide a 'big picture' of plant cell growth.
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Affiliation(s)
- Luke Braidwood
- RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro, Tsurumi, Yokohama, Kanagawa, 230-0045, Japan
| | - Christian Breuer
- RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro, Tsurumi, Yokohama, Kanagawa, 230-0045, Japan
| | - Keiko Sugimoto
- RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro, Tsurumi, Yokohama, Kanagawa, 230-0045, Japan
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Qin T, Liu X, Li J, Sun J, Song L, Mao T. Arabidopsis microtubule-destabilizing protein 25 functions in pollen tube growth by severing actin filaments. THE PLANT CELL 2014; 26:325-39. [PMID: 24424096 PMCID: PMC3963579 DOI: 10.1105/tpc.113.119768] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The formation of distinct actin filament arrays in the subapical region of pollen tubes is crucial for pollen tube growth. However, the molecular mechanisms underlying the organization and dynamics of the actin filaments in this region remain to be determined. This study shows that Arabidopsis thaliana MICROTUBULE-DESTABILIZING PROTEIN25 (MDP25) has the actin filament-severing activity of an actin binding protein. This protein negatively regulated pollen tube growth by modulating the organization and dynamics of actin filaments in the subapical region of pollen tubes. MDP25 loss of function resulted in enhanced pollen tube elongation and inefficient fertilization. MDP25 bound directly to actin filaments and severed individual actin filaments, in a manner that was dramatically enhanced by Ca(2+), in vitro. Analysis of a mutant that bears a point mutation at the Ca(2+) binding sites demonstrated that the subcellular localization of MDP25 was determined by cytosolic Ca(2+) level in the subapical region of pollen tubes, where MDP25 was disassociated from the plasma membrane and moved into the cytosol. Time-lapse analysis showed that the F-actin-severing frequency significantly decreased and a high density of actin filaments was observed in the subapical region of mdp25-1 pollen tubes. This study reveals a mechanism whereby calcium enhances the actin filament-severing activity of MDP25 in the subapical region of pollen tubes to modulate pollen tube growth.
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Boisson-Dernier A, Lituiev DS, Nestorova A, Franck CM, Thirugnanarajah S, Grossniklaus U. ANXUR receptor-like kinases coordinate cell wall integrity with growth at the pollen tube tip via NADPH oxidases. PLoS Biol 2013; 11:e1001719. [PMID: 24302886 PMCID: PMC3841104 DOI: 10.1371/journal.pbio.1001719] [Citation(s) in RCA: 205] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 10/16/2013] [Indexed: 11/19/2022] Open
Abstract
Pollen tubes grow extremely rapidly to effect fertilization in plants. ANXUR receptor-like kinases facilitate this growth by linking the intracellular growth machinery of pollen tubes to the status of the extracellular matrix via H2O2 and Ca2+ signaling. It has become increasingly apparent that the extracellular matrix (ECM), which in plants corresponds to the cell wall, can influence intracellular activities in ways that go far beyond their supposedly passive mechanical support. In plants, growing cells use mechanisms sensing cell wall integrity to coordinate cell wall performance with the internal growth machinery to avoid growth cessation or loss of integrity. How this coordination precisely works is unknown. Previously, we reported that in the tip-growing pollen tube the ANXUR receptor-like kinases (RLKs) of the CrRLK1L subfamily are essential to sustain growth without loss of cell wall integrity in Arabidopsis. Here, we show that over-expression of the ANXUR RLKs inhibits growth by over-activating exocytosis and the over-accumulation of secreted cell wall material. Moreover, the characterization of mutations in two partially redundant pollen-expressed NADPH oxidases coupled with genetic interaction studies demonstrate that the ANXUR RLKs function upstream of these NADPH oxidases. Using the H2O2-sensitive HyPer and the Ca2+-sensitive YC3.60 sensors in NADPH oxidase-deficient mutants, we reveal that NADPH oxidases generate tip-localized, pulsating H2O2 production that functions, possibly through Ca2+ channel activation, to maintain a steady tip-focused Ca2+ gradient during growth. Our findings support a model where ECM-sensing receptors regulate reactive oxygen species production, Ca2+ homeostasis, and exocytosis to coordinate ECM-performance with the internal growth machinery. Tip-growing cells, such as plant root hairs and pollen tubes or fungal hyphae, are characterized by a tip-focused Ca2+ gradient. These tip-growing cells tightly coordinate the loosening and pressure-driven deformation of their extracellular matrix (ECM)—the cell wall in plant cells—by locally adding new membrane and cell wall materials. In pollen tubes, which grow at amazing speeds to effect fertilization in plants, a class of kinases called the ANXUR receptor-like kinases (RLKs) sense perturbations in cell wall integrity, and their loss leads to pollen tube rupture. Here, we gain new insights into the mechanism of cell wall surveillance by these RLKs in the model plant Arabidopsis. We show that over-expressing ANXUR RLKs over-activates exocytosis, causing an over-accumulation of secreted cell wall material that eventually leads to growth arrest. Moreover, we find that the ANXUR RLKs function upstream of NADPH oxidases, which are membrane-anchored enzymes that produce reactive oxygen species (ROS). Using H2O2- and Ca2+-sensitive reporters, we show that NADPH oxidases generate tip-localized H2O2 production, which is required to maintain a steady, tip-focused Ca2+ gradient that is essential for pollen tube growth. We postulate that ECM-sensing receptors, such as the ANXUR RLKs, regulate ROS production, Ca2+ homeostasis, and exocytosis to coordinate the status of the ECM with the cell's internal growth machinery.
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Affiliation(s)
- Aurélien Boisson-Dernier
- Institute of Plant Biology, University of Zürich, Zürich, Switzerland
- Zürich-Basel Plant Science Center, ETH Zürich, Zürich, Switzerland
- * E-mail: (ABD); (UG)
| | - Dmytro S. Lituiev
- Institute of Plant Biology, University of Zürich, Zürich, Switzerland
- Zürich-Basel Plant Science Center, ETH Zürich, Zürich, Switzerland
| | - Anna Nestorova
- Institute of Plant Biology, University of Zürich, Zürich, Switzerland
- Zürich-Basel Plant Science Center, ETH Zürich, Zürich, Switzerland
| | - Christina Maria Franck
- Institute of Plant Biology, University of Zürich, Zürich, Switzerland
- Zürich-Basel Plant Science Center, ETH Zürich, Zürich, Switzerland
| | - Sharme Thirugnanarajah
- Institute of Plant Biology, University of Zürich, Zürich, Switzerland
- Zürich-Basel Plant Science Center, ETH Zürich, Zürich, Switzerland
| | - Ueli Grossniklaus
- Institute of Plant Biology, University of Zürich, Zürich, Switzerland
- Zürich-Basel Plant Science Center, ETH Zürich, Zürich, Switzerland
- * E-mail: (ABD); (UG)
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41
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Wang H, Zhuang X, Cai Y, Cheung AY, Jiang L. Apical F-actin-regulated exocytic targeting of NtPPME1 is essential for construction and rigidity of the pollen tube cell wall. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 76:367-79. [PMID: 23906068 DOI: 10.1111/tpj.12300] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 07/15/2013] [Accepted: 07/18/2013] [Indexed: 05/03/2023]
Abstract
In tip-confined growing pollen tubes, delivery of newly synthesized cell wall materials to the rapidly expanding apical surface requires spatial organization and temporal regulation of the apical F-actin filament and exocytosis. In this study, we demonstrate that apical F-actin is essential for the rigidity and construction of the pollen tube cell wall by regulating exocytosis of Nicotiana tabacum pectin methylesterase (NtPPME1). Wortmannin disrupts the spatial organization of apical F-actin in the pollen tube tip and inhibits polar targeting of NtPPME1, which subsequently alters the rigidity and pectic composition of the pollen tube cell wall, finally causing growth arrest of the pollen tube. In addition to mechanistically linking cell wall construction and apical F-actin, wortmannin can be used as a useful tool for studying endomembrane trafficking and cytoskeletal organization in pollen tubes.
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Affiliation(s)
- Hao Wang
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
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42
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Vanneste S, Friml J. Calcium: The Missing Link in Auxin Action. PLANTS (BASEL, SWITZERLAND) 2013; 2:650-75. [PMID: 27137397 PMCID: PMC4844386 DOI: 10.3390/plants2040650] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 10/07/2013] [Accepted: 10/10/2013] [Indexed: 01/18/2023]
Abstract
Due to their sessile lifestyles, plants need to deal with the limitations and stresses imposed by the changing environment. Plants cope with these by a remarkable developmental flexibility, which is embedded in their strategy to survive. Plants can adjust their size, shape and number of organs, bend according to gravity and light, and regenerate tissues that were damaged, utilizing a coordinating, intercellular signal, the plant hormone, auxin. Another versatile signal is the cation, Ca(2+), which is a crucial second messenger for many rapid cellular processes during responses to a wide range of endogenous and environmental signals, such as hormones, light, drought stress and others. Auxin is a good candidate for one of these Ca(2+)-activating signals. However, the role of auxin-induced Ca(2+) signaling is poorly understood. Here, we will provide an overview of possible developmental and physiological roles, as well as mechanisms underlying the interconnection of Ca(2+) and auxin signaling.
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Affiliation(s)
- Steffen Vanneste
- Plant Systems Biology, VIB, and Plant Biotechnology and Bio-informatics, Ghent University, Ghent 9052, Belgium.
| | - Jiří Friml
- Plant Systems Biology, VIB, and Plant Biotechnology and Bio-informatics, Ghent University, Ghent 9052, Belgium
- Institute of Science and Technology Austria (IST Austria), Klosterneuburg 3400, Austria
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43
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Park E, Nebenführ A. Myosin XIK of Arabidopsis thaliana accumulates at the root hair tip and is required for fast root hair growth. PLoS One 2013; 8:e76745. [PMID: 24116145 PMCID: PMC3792037 DOI: 10.1371/journal.pone.0076745] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2013] [Accepted: 08/28/2013] [Indexed: 11/19/2022] Open
Abstract
Myosin motor proteins are thought to carry out important functions in the establishment and maintenance of cell polarity by moving cellular components such as organelles, vesicles, or protein complexes along the actin cytoskeleton. In Arabidopsis thaliana, disruption of the myosin XIK gene leads to reduced elongation of the highly polar root hairs, suggesting that the encoded motor protein is involved in this cell growth. Detailed live-cell observations in this study revealed that xik root hairs elongated more slowly and stopped growth sooner than those in wild type. Overall cellular organization including the actin cytoskeleton appeared normal, but actin filament dynamics were reduced in the mutant. Accumulation of RabA4b-containing vesicles, on the other hand, was not significantly different from wild type. A functional YFP-XIK fusion protein that could complement the mutant phenotype accumulated at the tip of growing root hairs in an actin-dependent manner. The distribution of YFP-XIK at the tip, however, did not match that of the ER or several tip-enriched markers including CFP-RabA4b. We conclude that the myosin XIK is required for normal actin dynamics and plays a role in the subapical region of growing root hairs to facilitate optimal growth.
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Affiliation(s)
- Eunsook Park
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee, United States of America
| | - Andreas Nebenführ
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee, United States of America
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44
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Gu F, Nielsen E. Targeting and regulation of cell wall synthesis during tip growth in plants. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2013; 55:835-46. [PMID: 23758901 DOI: 10.1111/jipb.12077] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Accepted: 05/20/2013] [Indexed: 05/20/2023]
Abstract
Root hairs and pollen tubes are formed through tip growth, a process requiring synthesis of new cell wall material and the precise targeting and integration of these components to a selected apical plasma membrane domain in the growing tips of these cells. Presence of a tip-focused calcium gradient, control of actin cytoskeleton dynamics, and formation and targeting of secretory vesicles are essential to tip growth. Similar to cells undergoing diffuse growth, cellulose, hemicelluloses, and pectins are also deposited in the growing apices of tip-growing cells. However, differences in the manner in which these cell wall components are targeted and inserted in the expanding portion of tip-growing cells is reflected by the identification of elements of the plant cell wall synthesis machinery which have been shown to play unique roles in tip-growing cells. In this review, we summarize our current understanding of the tip growth process, with a particular focus on the subcellular targeting of newly synthesized cell wall components, and their roles in this form of plant cell expansion.
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Affiliation(s)
- Fangwei Gu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109, USA
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45
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Heilmann M, Heilmann I. Arranged marriage in lipid signalling? The limited choices of PtdIns(4,5)P2 in finding the right partner. PLANT BIOLOGY (STUTTGART, GERMANY) 2013; 15:789-797. [PMID: 23627419 DOI: 10.1111/plb.12025] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 02/07/2013] [Indexed: 06/02/2023]
Abstract
Inositol-containing phospholipids (phosphoinositides, PIs) control numerous cellular processes in eukaryotic cells. For plants, a key involvement of PIs has been demonstrated in the regulation of membrane trafficking, cytoskeletal dynamics and in processes mediating the adaptation to changing environmental conditions. Phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P(2)) mediates its cellular functions via binding to various alternative target proteins. Such downstream targets of PtdIns(4,5)P(2) are characterised by the possession of specific lipid-binding domains, and binding of the PtdIns(4,5)P(2) ligand exerts effects on their activity or localisation. The large number of potential alternative binding partners - and associated cellular processes - raises the question how alternative or even contrapuntal effects of PtdIns(4,5)P(2) are orchestrated to enable cellular function. This article aims to provide an overview of recent insights and new views on how distinct functional pools of PtdIns(4,5)P(2) are generated and maintained. The emerging picture suggests that PtdIns(4,5)P(2) species containing different fatty acids influence the lateral mobility of the lipids in the membrane, possibly enabling specific interactions of PtdIns(4,5)P(2) pools with certain downstream targets. PtdIns(4,5)P(2) pools with certain functions might also be defined by protein-protein interactions of PI4P 5-kinases, which pass PtdIns(4,5)P(2) only to certain downstream partners. Individually or in combination, PtdIns(4,5)P(2) species and specific protein-protein interactions of PI4P 5-kinases might contribute to the channelling of PtdIns(4,5)P(2) signals towards specific functional effects. The dynamic nature of PI-dependent signalling complexes with specific functions is an added challenge for future studies of plant PI signalling.
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Affiliation(s)
- M Heilmann
- Department of Cellular Biochemistry, Institute for Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany.
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46
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Sewelam N, Kazan K, Thomas-Hall SR, Kidd BN, Manners JM, Schenk PM. Ethylene response factor 6 is a regulator of reactive oxygen species signaling in Arabidopsis. PLoS One 2013; 8:e70289. [PMID: 23940555 PMCID: PMC3734174 DOI: 10.1371/journal.pone.0070289] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 06/18/2013] [Indexed: 11/18/2022] Open
Abstract
Reactive oxygen species (ROS) are produced in plant cells in response to diverse biotic and abiotic stresses as well as during normal growth and development. Although a large number of transcription factor (TF) genes are up- or down-regulated by ROS, currently very little is known about the functions of these TFs during oxidative stress. In this work, we examined the role of ERF6 (ETHYLENE RESPONSE FACTOR6), an AP2/ERF domain-containing TF, during oxidative stress responses in Arabidopsis. Mutant analyses showed that NADPH oxidase (RbohD) and calcium signaling are required for ROS-responsive expression of ERF6. erf6 insertion mutant plants showed reduced growth and increased H2O2 and anthocyanin levels. Expression analyses of selected ROS-responsive genes during oxidative stress identified several differentially expressed genes in the erf6 mutant. In particular, a number of ROS responsive genes, such as ZAT12, HSFs, WRKYs, MAPKs, RBOHs, DHAR1, APX4, and CAT1 were more strongly induced by H2O2 in erf6 plants than in wild-type. In contrast, MDAR3, CAT3, VTC2 and EX1 showed reduced expression levels in the erf6 mutant. Taken together, our results indicate that ERF6 plays an important role as a positive antioxidant regulator during plant growth and in response to biotic and abiotic stresses.
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Affiliation(s)
- Nasser Sewelam
- Plant-Microbe Interactions Laboratory, School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Kemal Kazan
- Commonwealth Scientific and Industrial Research Organization Plant Industry, Queensland Bioscience Precinct, Brisbane, Queensland, Australia
| | - Skye R. Thomas-Hall
- Plant-Microbe Interactions Laboratory, School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Brendan N. Kidd
- Plant-Microbe Interactions Laboratory, School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Queensland, Australia
- Commonwealth Scientific and Industrial Research Organization Plant Industry, Queensland Bioscience Precinct, Brisbane, Queensland, Australia
| | - John M. Manners
- Commonwealth Scientific and Industrial Research Organization Plant Industry, Queensland Bioscience Precinct, Brisbane, Queensland, Australia
| | - Peer M. Schenk
- Plant-Microbe Interactions Laboratory, School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Queensland, Australia
- * E-mail:
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47
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Guan Y, Guo J, Li H, Yang Z. Signaling in pollen tube growth: crosstalk, feedback, and missing links. MOLECULAR PLANT 2013; 6:1053-64. [PMID: 23873928 PMCID: PMC3842152 DOI: 10.1093/mp/sst070] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Accepted: 04/25/2013] [Indexed: 05/19/2023]
Abstract
Pollen tubes elongate rapidly at their tips through highly polarized cell growth known as tip growth. Tip growth requires intensive exocytosis at the tip, which is supported by a dynamic cytoskeleton and vesicle trafficking. Several signaling pathways have been demonstrated to coordinate pollen tube growth by regulating cellular activities such as actin dynamics, exocytosis, and endocytosis. These signaling pathways crosstalk to form a signaling network that coordinates the cellular processes required for tip growth. The homeostasis of key signaling molecules is critical for the proper elongation of the pollen tube tip, and is commonly fine-tuned by positive and negative regulations. In addition to the major signaling pathways, emerging evidence implies the roles of other signals in the regulation of pollen tube growth. Here we review and discuss how these signaling networks modulate the rapid growth of pollen tubes.
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Affiliation(s)
- Yuefeng Guan
- Shanghai Center for Plant Stress Biology and Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
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48
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Chang F, Gu Y, Ma H, Yang Z. AtPRK2 promotes ROP1 activation via RopGEFs in the control of polarized pollen tube growth. MOLECULAR PLANT 2013; 6:1187-201. [PMID: 23024212 PMCID: PMC3888354 DOI: 10.1093/mp/sss103] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Accepted: 09/06/2012] [Indexed: 05/19/2023]
Abstract
The ROP1 GTPase-based signaling network controls tip growth in Arabidopsis pollen tubes. Our previous studies imply that ROP1 might be directly activated by RopGEF1, which belongs to a plant-specific family of Rho guanine nucleotide exchange factors (RopGEFs) and in turn may be activated by an unknown factor through releasing RopGEF1's auto-inhibition. In this study, we found that RopGEF1 forms a complex with ROP1 and AtPRK2, a receptor-like protein kinase previously shown to interact with RopGEFs. AtPRK2 phosphorylated RopGEF1 in vitro and the atprk1,2,5 triple mutant showed defective pollen tube growth, similar to the phenotype of the ropgef1,9,12,14 quadruple mutant. Overexpression of a dominant negative form of AtPRK2 (DN-PRK2) inhibited pollen germination in Arabidopsis and reduced pollen elongation in tobacco. The DN-PRK2-induced pollen germination defect was rescued by overexpressing a constitutively active form of RopGEF1, RopGEF1(90-457), implying that RopGEF1 acts downstream of AtPRK2. Moreover, AtPRK2 increased ROP1 activity at the apical plasma membrane whereas DN-PRK2 reduced ROP1 activity. Finally, two mutations at the C-terminal putative phosphorylation sites of RopGEF1 (RopGEF1S460A and RopGEF1S480A) eliminated the function of RopGEF1 in vivo. Taken together, our results support the hypothesis that AtPRK2 acts as a positive regulator of the ROP1 signaling pathway most likely by activating RopGEF1 through phosphorylation.
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Affiliation(s)
- Fang Chang
- State Key Laboratory of Genetic Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200433, China
- National Key Laboratory of Plant Physiology and Biochemistry, China Agricultural University, Beijing 100094, China
- Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA
- These authors contributed equally to this work
| | - Ying Gu
- Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA
- Present address: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA
- These authors contributed equally to this work
| | - Hong Ma
- State Key Laboratory of Genetic Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200433, China
- Center for Evolutionary Biology, School of Life Sciences, Fudan University, Shanghai 200433, China
| | - Zhenbiao Yang
- Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA
- To whom correspondence should be addressed. E-mail , tel. 951–827–7351, fax 951–827–4437
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49
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McDowell SC, López-Marqués RL, Poulsen LR, Palmgren MG, Harper JF. Loss of the Arabidopsis thaliana P₄-ATPase ALA3 reduces adaptability to temperature stresses and impairs vegetative, pollen, and ovule development. PLoS One 2013; 8:e62577. [PMID: 23667493 PMCID: PMC3646830 DOI: 10.1371/journal.pone.0062577] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Accepted: 03/20/2013] [Indexed: 12/28/2022] Open
Abstract
Members of the P4 subfamily of P-type ATPases are thought to help create asymmetry in lipid bilayers by flipping specific lipids between the leaflets of a membrane. This asymmetry is believed to be central to the formation of vesicles in the secretory and endocytic pathways. In Arabidopsis thaliana, a P4-ATPase associated with the trans-Golgi network (ALA3) was previously reported to be important for vegetative growth and reproductive success. Here we show that multiple phenotypes for ala3 knockouts are sensitive to growth conditions. For example, ala3 rosette size was observed to be dependent upon both temperature and soil, and varied between 40% and 80% that of wild-type under different conditions. We also demonstrate that ala3 mutants have reduced fecundity resulting from a combination of decreased ovule production and pollen tube growth defects. In-vitro pollen tube growth assays showed that ala3 pollen germinated ∼2 h slower than wild-type and had approximately 2-fold reductions in both maximal growth rate and overall length. In genetic crosses under conditions of hot days and cold nights, pollen fitness was reduced by at least 90-fold; from ∼18% transmission efficiency (unstressed) to less than 0.2% (stressed). Together, these results support a model in which ALA3 functions to modify endomembranes in multiple cell types, enabling structural changes, or signaling functions that are critical in plants for normal development and adaptation to varied growth environments.
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Affiliation(s)
- Stephen C. McDowell
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Nevada, United States of America
| | - Rosa L. López-Marqués
- Department of Plant Biology and Biotechnology, Centre for Membrane Pumps in Cells and Disease (PUMPKIN), University of Copenhagen, Danish National Research Foundation, Frederiksberg, Denmark
| | - Lisbeth R. Poulsen
- Department of Plant Biology and Biotechnology, Centre for Membrane Pumps in Cells and Disease (PUMPKIN), University of Copenhagen, Danish National Research Foundation, Frederiksberg, Denmark
| | - Michael G. Palmgren
- Department of Plant Biology and Biotechnology, Centre for Membrane Pumps in Cells and Disease (PUMPKIN), University of Copenhagen, Danish National Research Foundation, Frederiksberg, Denmark
| | - Jeffrey F. Harper
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Nevada, United States of America
- * E-mail:
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Del Duca S, Faleri C, Iorio RA, Cresti M, Serafini-Fracassini D, Cai G. Distribution of transglutaminase in pear pollen tubes in relation to cytoskeleton and membrane dynamics. PLANT PHYSIOLOGY 2013; 161:1706-21. [PMID: 23396835 PMCID: PMC3613450 DOI: 10.1104/pp.112.212225] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Transglutaminases (TGases) are ubiquitous enzymes that take part in a variety of cellular functions. In the pollen tube, cytoplasmic TGases are likely to be involved in the incorporation of primary amines at selected peptide-bound glutamine residues of cytosolic proteins (including actin and tubulin), while cell wall-associated TGases are believed to regulate pollen tube growth. Using immunological probes, we identified TGases associated with different subcellular compartments (cytosol, membranes, and cell walls). Binding of cytosolic TGase to actin filaments was shown to be Ca(2+) dependent. The membrane TGase is likely associated with both Golgi-derived structures and the plasma membrane, suggesting a Golgi-based exocytotic delivery of TGase. Association of TGase with the plasma membrane was also confirmed by immunogold transmission electron microscopy. Immunolocalization of TGase indicated that the enzyme was present in the growing region of pollen tubes and that the enzyme colocalizes with cell wall markers. Bidimensional electrophoresis indicated that different TGase isoforms were present in distinct subcellular compartments, suggesting either different roles or different regulatory mechanisms of enzyme activity. The application of specific inhibitors showed that the distribution of TGase in different subcellular compartments was regulated by both membrane dynamics and cytoskeleton integrity, suggesting that delivery of TGase to the cell wall requires the transport of membranes along cytoskeleton filaments. Taken together, these data indicate that a cytoplasmic TGase interacts with the cytoskeleton, while a different TGase isoform, probably delivered via a membrane/cytoskeleton-based transport system, is secreted in the cell wall of pear (Pyrus communis) pollen tubes, where it might play a role in the regulation of apical growth.
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