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Irulappan V, Park HW, Han SY, Kim MH, Kim JS. Genome-wide identification of a novel Na + transporter from Bienertia sinuspersici and overexpression of BsHKT1;2 improved salt tolerance in Brassica rapa. FRONTIERS IN PLANT SCIENCE 2023; 14:1302315. [PMID: 38192689 PMCID: PMC10773568 DOI: 10.3389/fpls.2023.1302315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Accepted: 11/24/2023] [Indexed: 01/10/2024]
Abstract
Salt stress is an ever-increasing stressor that affects both plants and humans. Therefore, developing strategies to limit the undesirable effects of salt stress is essential. Sodium ion exclusion is well known for its efficient salt-tolerance mechanism. The High-affinity K+ Transporter (HKT) excludes excess Na+ from the transpiration stream. This study identified and characterized the HKT protein family in Bienertia sinuspersici, a single-cell C4 plant. The HKT and Salt Overly Sensitive 1 (SOS1) expression levels were examined in B. sinuspersici and Arabidopsis thaliana leaves under four different salt stress conditions: 0, 100, 200, and 300 mM NaCl. Furthermore, BsHKT1;2 was cloned, thereby producing stable transgenic Brassica rapa. Our results showed that, compared to A. thaliana as a glycophyte, the HKT family is expanded in B. sinuspersici as a halophyte with three paralogs. The phylogenetic analysis revealed three paralogs belonging to the HKT subfamily I. Out of three copies, the expression of BsHKT1;2 was higher in Bienertia under control and salt stress conditions than in A. thaliana. Stable transgenic plants overexpressing 35S::BsHKT1;2 showed higher salt tolerance than non-transgenic plants. Higher biomass and longer roots were observed in the transgenic plants under salt stress than in non-transgenic plants. This study demonstrates the evolutionary and functional differences in HKT proteins between glycophytes and halophytes and associates the role of BsHKT1;2 in imparting salt tolerance and productivity.
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Affiliation(s)
| | | | | | | | - Jung Sun Kim
- Genomics Division, Department of Agricultural Bio-Resources, National Institute of Agricultural Sciences, Jeonju, Republic of Korea
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Han SY, Kim WY, Kim JS, Hwang I. Comparative transcriptomics reveals the role of altered energy metabolism in the establishment of single-cell C 4 photosynthesis in Bienertia sinuspersici. FRONTIERS IN PLANT SCIENCE 2023; 14:1202521. [PMID: 37476170 PMCID: PMC10354284 DOI: 10.3389/fpls.2023.1202521] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/08/2023] [Accepted: 05/31/2023] [Indexed: 07/22/2023]
Abstract
Single-cell C4 photosynthesis (SCC4) in terrestrial plants without Kranz anatomy involves three steps: initial CO2 fixation in the cytosol, CO2 release in mitochondria, and a second CO2 fixation in central chloroplasts. Here, we investigated how the large number of mechanisms underlying these processes, which occur in three different compartments, are orchestrated in a coordinated manner to establish the C4 pathway in Bienertia sinuspersici, a SCC4 plant. Leaves were subjected to transcriptome analysis at three different developmental stages. Functional enrichment analysis revealed that SCC4 cycle genes are coexpressed with genes regulating cyclic electron flow and amino/organic acid metabolism, two key processes required for the production of energy molecules in C3 plants. Comparative gene expression profiling of B. sinuspersici and three other species (Suaeda aralocaspica, Amaranthus hypochondriacus, and Arabidopsis thaliana) showed that the direction of metabolic flux was determined via an alteration in energy supply in peripheral chloroplasts and mitochondria via regulation of gene expression in the direction of the C4 cycle. Based on these results, we propose that the redox homeostasis of energy molecules via energy metabolism regulation is key to the establishment of the SCC4 pathway in B. sinuspersici.
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Affiliation(s)
- Sang-Yun Han
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Republic of Korea
| | - Woe-Yeon Kim
- Division of Applied Life Science (BK21+) and Research Institute of Life Science, Institute of Agriculture and Life Sciences, Gyeongsang National University, Jinju, Republic of Korea
| | - Jung Sun Kim
- Genomic Division, Department of Agricultural Bio-Resources, National Institute of Agricultural Sciences, Rural Development Administration, Jeonju, Republic of Korea
| | - Inhwan Hwang
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Republic of Korea
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Liang Z, Yeung WT, Ma J, Mai KKK, Liu Z, Chong YLF, Cai X, Kang BH. Electron tomography of prolamellar bodies and their transformation into grana thylakoids in cryofixed Arabidopsis cotyledons. THE PLANT CELL 2022; 34:3830-3843. [PMID: 35876816 PMCID: PMC9516191 DOI: 10.1093/plcell/koac205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 07/05/2022] [Indexed: 06/15/2023]
Abstract
The para-crystalline structures of prolamellar bodies (PLBs) and light-induced etioplast-to-chloroplast transformation have been investigated via electron microscopy. However, such studies suffer from chemical fixation artifacts and limited volumes of 3D reconstruction. Here, we examined Arabidopsis thaliana cotyledon cells by electron tomography (ET) to visualize etioplasts and their conversion into chloroplasts. We employed scanning transmission ET to image large volumes and high-pressure freezing to improve sample preservation. PLB tubules were arranged in a zinc blende-type lattice-like carbon atoms in diamonds. Within 2 h after illumination, the lattice collapsed from the PLB exterior and the disorganized tubules merged to form thylakoid sheets (pre-granal thylakoids), which folded and overlapped with each other to create grana stacks. Since the nascent pre-granal thylakoids contained curved membranes in their tips, we examined the expression and localization of CURT1 (CURVATURE THYLAKOID1) proteins. CURT1A transcripts were most abundant in de-etiolating cotyledon samples, and CURT1A was concentrated at the PLB periphery. In curt1a etioplasts, PLB-associated thylakoids were swollen and failed to form grana stacks. In contrast, PLBs had cracks in their lattices in curt1c etioplasts. Our data provide evidence that CURT1A is required for pre-granal thylakoid assembly from PLB tubules during de-etiolation, while CURT1C contributes to cubic crystal growth in the dark.
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Affiliation(s)
| | - Wai-Tsun Yeung
- Centre for Cell and Developmental Biology, State Key Laboratory for Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Juncai Ma
- Centre for Cell and Developmental Biology, State Key Laboratory for Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Keith Ka Ki Mai
- Centre for Cell and Developmental Biology, State Key Laboratory for Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Zhongyuan Liu
- Centre for Cell and Developmental Biology, State Key Laboratory for Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Yau-Lun Felix Chong
- Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Xiaohao Cai
- School of Electronics and Computer Science, The University of Southampton, Southampton, UK
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Khoshravesh R, Hoffmann N, Hanson DT. Leaf microscopy applications in photosynthesis research: identifying the gaps. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:1868-1893. [PMID: 34986250 DOI: 10.1093/jxb/erab548] [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: 08/23/2021] [Accepted: 12/10/2021] [Indexed: 06/14/2023]
Abstract
Leaf imaging via microscopy has provided critical insights into research on photosynthesis at multiple junctures, from the early understanding of the role of stomata, through elucidating C4 photosynthesis via Kranz anatomy and chloroplast arrangement in single cells, to detailed explorations of diffusion pathways and light utilization gradients within leaves. In recent decades, the original two-dimensional (2D) explorations have begun to be visualized in three-dimensional (3D) space, revising our understanding of structure-function relationships between internal leaf anatomy and photosynthesis. In particular, advancing new technologies and analyses are providing fresh insight into the relationship between leaf cellular components and improving the ability to model net carbon fixation, water use efficiency, and metabolite turnover rate in leaves. While ground-breaking developments in imaging tools and techniques have expanded our knowledge of leaf 3D structure via high-resolution 3D and time-series images, there is a growing need for more in vivo imaging as well as metabolite imaging. However, these advances necessitate further improvement in microscopy sciences to overcome the unique challenges a green leaf poses. In this review, we discuss the available tools, techniques, challenges, and gaps for efficient in vivo leaf 3D imaging, as well as innovations to overcome these difficulties.
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Affiliation(s)
| | - Natalie Hoffmann
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
| | - David T Hanson
- Department of Biology, University of New Mexico, Albuquerque, NM, USA
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Accelerated remodeling of the mesophyll-bundle sheath interface in the maize C4 cycle mutant leaves. Sci Rep 2022; 12:5057. [PMID: 35322159 PMCID: PMC8943126 DOI: 10.1038/s41598-022-09135-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 03/14/2022] [Indexed: 11/18/2022] Open
Abstract
C4 photosynthesis in the maize leaf involves the exchange of organic acids between mesophyll (M) and the bundle sheath (BS) cells. The transport is mediated by plasmodesmata embedded in the suberized cell wall. We examined the maize Kranz anatomy with a focus on the plasmodesmata and cell wall suberization with microscopy methods. In the young leaf zone where M and BS cells had indistinguishable proplastids, plasmodesmata were simple and no suberin was detected. In leaf zones where dimorphic chloroplasts were evident, the plasmodesma acquired sphincter and cytoplasmic sleeves, and suberin was discerned. These modifications were accompanied by a drop in symplastic dye mobility at the M-BS boundary. We compared the kinetics of chloroplast differentiation and the modifications in M-BS connectivity in ppdk and dct2 mutants where C4 cycle is affected. The rate of chloroplast diversification did not alter, but plasmodesma remodeling, symplastic transport inhibition, and cell wall suberization were observed from younger leaf zone in the mutants than in wild type. Our results indicate that inactivation of the C4 genes accelerated the changes in the M-BS interface, and the reduced permeability suggests that symplastic transport between M and BS could be regulated for normal operation of C4 cycle.
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Weiner E, Pinskey JM, Nicastro D, Otegui MS. Electron microscopy for imaging organelles in plants and algae. PLANT PHYSIOLOGY 2022; 188:713-725. [PMID: 35235662 PMCID: PMC8825266 DOI: 10.1093/plphys/kiab449] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 08/23/2021] [Indexed: 05/31/2023]
Abstract
Recent developments in both instrumentation and image analysis algorithms have allowed three-dimensional electron microscopy (3D-EM) to increase automated image collections through large tissue volumes using serial block-face scanning EM (SEM) and to achieve near-atomic resolution of macromolecular complexes using cryo-electron tomography (cryo-ET) and sub-tomogram averaging. In this review, we discuss applications of cryo-ET to cell biology research on plant and algal systems and the special opportunities they offer for understanding the organization of eukaryotic organelles with unprecedently resolution. However, one of the most challenging aspects for cryo-ET is sample preparation, especially for multicellular organisms. We also discuss correlative light and electron microscopy (CLEM) approaches that have been developed for ET at both room and cryogenic temperatures.
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Affiliation(s)
- Ethan Weiner
- Department of Botany, University of Wisconsin, Madison 53706, Wisconsin
- Center for Quantitative Cell Imaging, University of Wisconsin, Madison 53706, Wisconsin
| | - Justine M Pinskey
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas 75390, Texas
| | - Daniela Nicastro
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas 75390, Texas
| | - Marisa S Otegui
- Department of Botany, University of Wisconsin, Madison 53706, Wisconsin
- Center for Quantitative Cell Imaging, University of Wisconsin, Madison 53706, Wisconsin
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Li C, Liu Y, Liu X, Mai KKK, Li J, Guo X, Zhang C, Li H, Kang BH, Hwang I, Lu H. Chloroplast thylakoid ascorbate peroxidase PtotAPX plays a key role in chloroplast development by decreasing hydrogen peroxide in Populus tomentosa. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:4333-4354. [PMID: 33884422 DOI: 10.1093/jxb/erab173] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 04/17/2021] [Indexed: 06/12/2023]
Abstract
Chloroplast development is a complex process that is critical to the growth and development of plants. However, the detailed mechanism of chloroplast development in woody plants remains unclear. In this study, we showed that chloroplasts with elaborate thylakoids could develop from proplastids in the cells of calli derived from leaf tissues of Populus tomentosa upon exposure to light. Chloroplast development was confirmed at the molecular and cellular levels. Transcriptome analysis revealed that genes related to photoreceptors and photosynthesis were significantly up-regulated during chloroplast development in a time-dependent manner. In light-induced chloroplast development, a key process was the removal of hydrogen peroxide, in which thylakoid-localized PtotAPX played a major role; light-induced chloroplast development was enhanced in PtotAPX-overexpressing transgenic P. tomentosa callus with lower levels of hydrogen peroxide, but was suppressed in PtotAPX antisense transgenic callus with higher levels of hydrogen peroxide. Moreover, the suppression of light-induced chloroplast development in PtotAPX antisense transgenic callus was relieved by the exogenous reactive oxygen species scavenging agent N,N'-dimethylthiourea (DMTU). Based on these results, we propose that PtotAPX-mediated removal of reactive oxygen species plays a key role in chloroplast development from proplastids upon exposure to light in P. tomentosa.
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Affiliation(s)
- Conghui Li
- Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, China
- College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing, China
| | - Yadi Liu
- Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, China
- College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing, China
| | - Xiatong Liu
- Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, China
- College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing, China
| | - Keith Ka Ki Mai
- Centre for Cell and Developmental Biology, State Key Laboratory for Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Jiaxin Li
- College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing, China
| | - Xiaorui Guo
- Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, China
- College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing, China
| | - Chong Zhang
- College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing, China
| | - Hui Li
- Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, China
- College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing, China
| | - Byung-Ho Kang
- Centre for Cell and Developmental Biology, State Key Laboratory for Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Inhwan Hwang
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang, South Korea
| | - Hai Lu
- Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, China
- College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing, China
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Mai KKK, Gao P, Kang BH. Electron Microscopy Views of Dimorphic Chloroplasts in C4 Plants. FRONTIERS IN PLANT SCIENCE 2020; 11:1020. [PMID: 32719711 PMCID: PMC7350421 DOI: 10.3389/fpls.2020.01020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Accepted: 06/22/2020] [Indexed: 05/02/2023]
Abstract
C4 plants enhance photosynthesis efficiency by concentrating CO2 to the site of Rubisco action. Chloroplasts in C4 plants exhibit structural dimorphism because thylakoid architectures vary depending on energy requirements. Advances in electron microscopy imaging capacity and sample preparation technologies allowed characterization of thylakoid structures and their macromolecular arrangements with unprecedented precision mostly in C3 plants. The thylakoid is assembled during chloroplast biogenesis through collaboration between the plastid and nuclear genomes. Recently, the membrane dynamics involved in the assembly process has been investigated with 3D electron microscopy, and molecular factors required for thylakoid construction have been characterized. The two classes of chloroplasts in C4 plants arise from common precursors, but little is known about how a single type of chloroplasts grow, divide, and differentiate to mature into distinct chloroplasts. Here, we outline the thylakoid structure and its assembly processes in C3 plants to discuss ultrastructural analyses of dimorphic chloroplast biogenesis in C4 plant species. Future directions for electron microscopy research of C4 photosynthetic systems are also proposed.
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