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Zhu M, Tang Y, Xie Y, He B, Ding G, Zhou X. Research progress on differentiation and regulation of plant chromoplasts. Mol Biol Rep 2024; 51:810. [PMID: 39001942 DOI: 10.1007/s11033-024-09753-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2024] [Accepted: 06/24/2024] [Indexed: 07/15/2024]
Abstract
Carotenoids, natural tetraterpenoids found abundantly in plants, contribute to the diverse colors of plant non-photosynthetic tissues and provide fragrance through their cleavage products, which also play crucial roles in plant growth and development. Understanding the synthesis, degradation, and storage pathways of carotenoids and identifying regulatory factors represents a significant strategy for enhancing plant quality. Chromoplasts serve as the primary plastids responsible for carotenoid accumulation, and their differentiation is linked to the levels of carotenoids, rendering them a subject of substantial research interest. The differentiation of chromoplasts involves alterations in plastid structure and protein import machinery. Additionally, this process is influenced by factors such as the ORANGE (OR) gene, Clp proteases, xanthophyll esterification, and environmental factors. This review shows the relationship between chromoplast and carotenoid accumulation by presenting recent advances in chromoplast structure, the differentiation process, and key regulatory factors, which can also provide a reference for rational exploitation of chromoplasts to enhance plant quality.
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Affiliation(s)
- Mengyao Zhu
- College of Landscape Architecture and Art, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Yunxia Tang
- College of Landscape Architecture and Art, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Yiqing Xie
- Institute of Economic Forestry, Fujian Academy of Forestry, Fuzhou, 350012, China
| | - BingBing He
- College of Landscape Architecture and Art, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Guochang Ding
- College of Landscape Architecture and Art, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
| | - Xingwen Zhou
- College of Architecture and Planning, Fujian University of Technology, Fuzhou, 350118, China.
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2
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Akter S, Castaneda-Méndez O, Beltrán J. Synthetic reprogramming of plant developmental and biochemical pathways. Curr Opin Biotechnol 2024; 87:103139. [PMID: 38691988 DOI: 10.1016/j.copbio.2024.103139] [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: 03/02/2024] [Revised: 04/16/2024] [Accepted: 04/16/2024] [Indexed: 05/03/2024]
Abstract
Plant synthetic biology (Plant SynBio) is an emerging field with the potential to enhance agriculture, human health, and sustainability. Integrating genetic tools and engineering principles, Plant SynBio aims to manipulate cellular functions and construct novel biochemical pathways to develop plants with new phenotypic traits, enhanced yield, and be able to produce natural products and pharmaceuticals. This review compiles research efforts in reprogramming plant developmental and biochemical pathways. We highlight studies leveraging new gene expression toolkits to alter plant architecture for improved performance in model and crop systems and to produce useful metabolites in plant tissues. Furthermore, we provide insights into the challenges and opportunities associated with the adoption of Plant SynBio in addressing complex issues impacting agriculture and human health.
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Affiliation(s)
- Shammi Akter
- Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716, USA; Delaware Biotechnology Institute, University of Delaware, 590 Avenue 1743, Newark, DE 19713, USA
| | - Oscar Castaneda-Méndez
- Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716, USA; Delaware Biotechnology Institute, University of Delaware, 590 Avenue 1743, Newark, DE 19713, USA
| | - Jesús Beltrán
- Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716, USA; Delaware Biotechnology Institute, University of Delaware, 590 Avenue 1743, Newark, DE 19713, USA.
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3
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Li Y, Perez-Gil J, Lois LM, Varejão N, Reverter D. Broad-spectrum ubiquitin/ubiquitin-like deconjugation activity of the rhizobial effector NopD from Bradyrhizobium (sp. XS1150). Commun Biol 2024; 7:644. [PMID: 38802699 PMCID: PMC11130253 DOI: 10.1038/s42003-024-06344-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Accepted: 05/16/2024] [Indexed: 05/29/2024] Open
Abstract
The post-translational modification of proteins by ubiquitin-like modifiers (UbLs), such as SUMO, ubiquitin, and Nedd8, regulates a vast array of cellular processes. Dedicated UbL deconjugating proteases families reverse these modifications. During bacterial infection, effector proteins, including deconjugating proteases, are released to disrupt host cell defenses and promote bacterial survival. NopD, an effector protein from rhizobia involved in legume nodule symbiosis, exhibits deSUMOylation activity and, unexpectedly, also deubiquitination and deNeddylation activities. Here, we present two crystal structures of Bradyrhizobium (sp. XS1150) NopD complexed with either Arabidopsis SUMO2 or ubiquitin at 1.50 Å and 1.94 Å resolution, respectively. Despite their low sequence similarity, SUMO and ubiquitin bind to a similar NopD interface, employing a unique loop insertion in the NopD sequence. In vitro binding and activity assays reveal specific residues that distinguish between deubiquitination and deSUMOylation. These unique multifaceted deconjugating activities against SUMO, ubiquitin, and Nedd8 exemplify an optimized bacterial protease that disrupts distinct UbL post-translational modifications during host cell infection.
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Affiliation(s)
- Ying Li
- Institut de Biotecnologia i de Biomedicina and Dept. de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, 08193, Bellaterra, Barcelona, Spain
- Qingdao University, 266071, Qingdao, China
| | - Jordi Perez-Gil
- Center for Research in Agricultural Genomics-CRAG, Edifici CRAG-Campus UAB, 08193, Bellaterra, Barcelona, Spain
- ARC Centre of Excellence in Synthetic Biology and Centre for Agriculture and the Bioeconomy, Queensland University of Technology, Brisbane, QLD, 4000, Australia
| | - L Maria Lois
- Center for Research in Agricultural Genomics-CRAG, Edifici CRAG-Campus UAB, 08193, Bellaterra, Barcelona, Spain
- Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Nathalia Varejão
- Institut de Biotecnologia i de Biomedicina and Dept. de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, 08193, Bellaterra, Barcelona, Spain.
| | - David Reverter
- Institut de Biotecnologia i de Biomedicina and Dept. de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, 08193, Bellaterra, Barcelona, Spain.
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.
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4
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Bibik JD, Hamberger B. Plant Engineering to Enable Platforms for Sustainable Bioproduction of Terpenoids. Methods Mol Biol 2024; 2760:3-20. [PMID: 38468079 DOI: 10.1007/978-1-0716-3658-9_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
Abstract
Terpenoids represent the most diverse class of natural products, with a broad spectrum of industrial relevance including applications in green solvents, flavors and fragrances, nutraceuticals, colorants, and therapeutics. They are typically challenging to extract from their natural sources, where they occur in small amounts and mixtures of related but unwanted byproducts. Formal chemical synthesis, where established, is reliant on petrochemistry. Hence, there is great interest in developing sustainable solutions to assemble biosynthetic pathways in engineered host organisms. Metabolic engineering for chemical production has largely focused on microbial hosts, yet plants offer a sustainable production platform. In addition to containing the precursor pathways that generate the terpenoid building blocks as well as the cell structures and compartments required, or tractable localization for the enzymes involved, plants may provide a low input system to produce these chemicals using carbon dioxide and sunlight only. There have been significant recent advancements in the discovery of pathways to terpenoids of interest as well as strategies to boost yields in host plants. While part of the phytochemical field is focusing on the discovery of biosynthetic pathways, this review will focus on advancements using the pathway toolbox and toward engineering plants for the production of terpenoids. We will highlight strategies currently used to produce target products, optimization of known pathways to improve yields, compartmentalization of pathways within cells, and genetic tools developed to facilitate complex engineering of biosynthetic pathways. These advancements in Synthetic Biology are bringing engineered plant systems closer to commercially relevant hosts for the bioproduction of terpenoids.
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Affiliation(s)
- Jacob D Bibik
- Department of Biochemistry, Michigan State University, East Lansing, MI, USA
- MelaTech, LLC, Baltimore, MD, USA
| | - Björn Hamberger
- Department of Biochemistry, Michigan State University, East Lansing, MI, USA.
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5
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Basallo O, Perez L, Lucido A, Sorribas A, Marin-Saguino A, Vilaprinyo E, Perez-Fons L, Albacete A, Martínez-Andújar C, Fraser PD, Christou P, Capell T, Alves R. Changing biosynthesis of terpenoid percursors in rice through synthetic biology. FRONTIERS IN PLANT SCIENCE 2023; 14:1133299. [PMID: 37465386 PMCID: PMC10350630 DOI: 10.3389/fpls.2023.1133299] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Accepted: 05/30/2023] [Indexed: 07/20/2023]
Abstract
Many highly valued chemicals in the pharmaceutical, biotechnological, cosmetic, and biomedical industries belong to the terpenoid family. Biosynthesis of these chemicals relies on polymerization of Isopentenyl di-phosphate (IPP) and/or dimethylallyl diphosphate (DMAPP) monomers, which plants synthesize using two alternative pathways: a cytosolic mevalonic acid (MVA) pathway and a plastidic methyleritritol-4-phosphate (MEP) pathway. As such, developing plants for use as a platform to use IPP/DMAPP and produce high value terpenoids is an important biotechnological goal. Still, IPP/DMAPP are the precursors to many plant developmental hormones. This creates severe challenges in redirecting IPP/DMAPP towards production of non-cognate plant metabolites. A potential solution to this problem is increasing the IPP/DMAPP production flux in planta. Here, we aimed at discovering, understanding, and predicting the effects of increasing IPP/DMAPP production in plants through modelling. We used synthetic biology to create rice lines containing an additional ectopic MVA biosynthetic pathway for producing IPP/DMAPP. The rice lines express three alternative versions of the additional MVA pathway in the plastid, in addition to the normal endogenous pathways. We collected data for changes in macroscopic and molecular phenotypes, gene expression, isoprenoid content, and hormone abundance in those lines. To integrate the molecular and macroscopic data and develop a more in depth understanding of the effects of engineering the exogenous pathway in the mutant rice lines, we developed and analyzed data-centric, line-specific, multilevel mathematical models. These models connect the effects of variations in hormones and gene expression to changes in macroscopic plant phenotype and metabolite concentrations within the MVA and MEP pathways of WT and mutant rice lines. Our models allow us to predict how an exogenous IPP/DMAPP biosynthetic pathway affects the flux of terpenoid precursors. We also quantify the long-term effect of plant hormones on the dynamic behavior of IPP/DMAPP biosynthetic pathways in seeds, and predict plant characteristics, such as plant height, leaf size, and chlorophyll content from molecular data. In addition, our models are a tool that can be used in the future to help in prioritizing re-engineering strategies for the exogenous pathway in order to achieve specific metabolic goals.
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Affiliation(s)
- Orio Basallo
- Systems Biology Group, Department Ciències Mèdiques Bàsiques, Faculty of Medicine, Universitat de Lleida, Lleida, Spain
- Institut de Recerca Biomedica de Lleida (IRBLleida), Lleida, Spain
| | - Lucia Perez
- Applied Plant Biotechnology Group, Department de Producció Vegetal I Ciència Florestal, Escola Tècnica Superior d'Enginyeria Agroalimentària i Forestal i de Veterinària (ETSEAFiV), Universitat de Lleida, Lleida, Spain
- Agrotecnio Centres de Recerca de Catalunya (CERCA) Center, Lleida, Spain
| | - Abel Lucido
- Systems Biology Group, Department Ciències Mèdiques Bàsiques, Faculty of Medicine, Universitat de Lleida, Lleida, Spain
- Institut de Recerca Biomedica de Lleida (IRBLleida), Lleida, Spain
| | - Albert Sorribas
- Systems Biology Group, Department Ciències Mèdiques Bàsiques, Faculty of Medicine, Universitat de Lleida, Lleida, Spain
- Institut de Recerca Biomedica de Lleida (IRBLleida), Lleida, Spain
| | - Alberto Marin-Saguino
- Systems Biology Group, Department Ciències Mèdiques Bàsiques, Faculty of Medicine, Universitat de Lleida, Lleida, Spain
- Institut de Recerca Biomedica de Lleida (IRBLleida), Lleida, Spain
| | - Ester Vilaprinyo
- Systems Biology Group, Department Ciències Mèdiques Bàsiques, Faculty of Medicine, Universitat de Lleida, Lleida, Spain
- Institut de Recerca Biomedica de Lleida (IRBLleida), Lleida, Spain
| | - Laura Perez-Fons
- School of Biological Sciences, Royal Holloway University of London, Egham Hill, United Kingdom
| | - Alfonso Albacete
- Departament of Plant Nutrition, Center of Edaphology and Applied Biology of the Segura (CEBAS), Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Murcia, Murcia, Spain
- Department of Plant Production and Agrotechnology, Institute for Agri-Food Research and Development of Murcia, Murcia, Spain
| | - Cristina Martínez-Andújar
- Departament of Plant Nutrition, Center of Edaphology and Applied Biology of the Segura (CEBAS), Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Murcia, Murcia, Spain
| | - Paul D. Fraser
- School of Biological Sciences, Royal Holloway University of London, Egham Hill, United Kingdom
| | - Paul Christou
- Applied Plant Biotechnology Group, Department de Producció Vegetal I Ciència Florestal, Escola Tècnica Superior d'Enginyeria Agroalimentària i Forestal i de Veterinària (ETSEAFiV), Universitat de Lleida, Lleida, Spain
- Agrotecnio Centres de Recerca de Catalunya (CERCA) Center, Lleida, Spain
- ICREA, Catalan Institute for Research and Advanced Studies, Barcelona, Spain
| | - Teresa Capell
- Applied Plant Biotechnology Group, Department de Producció Vegetal I Ciència Florestal, Escola Tècnica Superior d'Enginyeria Agroalimentària i Forestal i de Veterinària (ETSEAFiV), Universitat de Lleida, Lleida, Spain
- Agrotecnio Centres de Recerca de Catalunya (CERCA) Center, Lleida, Spain
| | - Rui Alves
- Systems Biology Group, Department Ciències Mèdiques Bàsiques, Faculty of Medicine, Universitat de Lleida, Lleida, Spain
- Institut de Recerca Biomedica de Lleida (IRBLleida), Lleida, Spain
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6
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Di X, Ortega-Alarcon D, Kakumanu R, Iglesias-Fernandez J, Diaz L, Baidoo EEK, Velazquez-Campoy A, Rodríguez-Concepción M, Perez-Gil J. MEP pathway products allosterically promote monomerization of deoxy-D-xylulose-5-phosphate synthase to feedback-regulate their supply. PLANT COMMUNICATIONS 2023; 4:100512. [PMID: 36575800 DOI: 10.1016/j.xplc.2022.100512] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 12/11/2022] [Accepted: 12/22/2022] [Indexed: 05/11/2023]
Abstract
Isoprenoids are a very large and diverse family of metabolites required by all living organisms. All isoprenoids derive from the double-bond isomers isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), which are produced by the methylerythritol 4-phosphate (MEP) pathway in bacteria and plant plastids. It has been reported that IPP and DMAPP feedback-regulate the activity of deoxyxylulose 5-phosphate synthase (DXS), a dimeric enzyme that catalyzes the main flux-controlling step of the MEP pathway. Here we provide experimental insights into the underlying mechanism. Isothermal titration calorimetry and dynamic light scattering approaches showed that IPP and DMAPP can allosterically bind to DXS in vitro, causing a size shift. In silico ligand binding site analysis and docking calculations identified a potential allosteric site in the contact region between the two monomers of the active DXS dimer. Modulation of IPP and DMAPP contents in vivo followed by immunoblot analyses confirmed that high IPP/DMAPP levels resulted in monomerization and eventual aggregation of the enzyme in bacterial and plant cells. Loss of the enzymatically active dimeric conformation allows a fast and reversible reduction of DXS activity in response to a sudden increase or decrease in IPP/DMAPP supply, whereas aggregation and subsequent removal of monomers that would otherwise be available for dimerization appears to be a more drastic response in the case of persistent IPP/DMAPP overabundance (e.g., by a blockage in their conversion to downstream isoprenoids). Our results represent an important step toward understanding the regulation of the MEP pathway and rational design of biotechnological endeavors aimed at increasing isoprenoid contents in microbial and plant systems.
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Affiliation(s)
- Xueni Di
- Institute for Plant Molecular and Cell Biology (IBMCP), CSIC-Universitat Politècnica de València, 46022 Valencia, Spain; Centre for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, 08193 Barcelona, Spain
| | - David Ortega-Alarcon
- Institute for Biocomputation and Physics of Complex Systems (BIFI), Joint Unit GBsC-CSIC-BIFI, Universidad de Zaragoza, 50009 Zaragoza, Spain; Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, 50009 Zaragoza, Spain
| | - Ramu Kakumanu
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA 94608, USA; Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | | | - Lucia Diaz
- Nostrum Biodiscovery SL, 08029 Barcelona, Spain
| | - Edward E K Baidoo
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA 94608, USA; Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Adrian Velazquez-Campoy
- Institute for Biocomputation and Physics of Complex Systems (BIFI), Joint Unit GBsC-CSIC-BIFI, Universidad de Zaragoza, 50009 Zaragoza, Spain; Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, 50009 Zaragoza, Spain; Instituto de Investigación Sanitaria de Aragón (IIS Aragon), 50009 Zaragoza, Spain; Centro de Investigación Biomédica en Red en el Área Temática de Enfermedades Hepáticas y Digestivas (CIBERehd), 28029 Madrid, Spain
| | - Manuel Rodríguez-Concepción
- Institute for Plant Molecular and Cell Biology (IBMCP), CSIC-Universitat Politècnica de València, 46022 Valencia, Spain; Centre for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, 08193 Barcelona, Spain.
| | - Jordi Perez-Gil
- Centre for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, 08193 Barcelona, Spain.
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Morelli L, Torres-Montilla S, Glauser G, Shanmugabalaji V, Kessler F, Rodriguez-Concepcion M. Novel insights into the contribution of plastoglobules and reactive oxygen species to chromoplast differentiation. THE NEW PHYTOLOGIST 2023; 237:1696-1710. [PMID: 36307969 DOI: 10.1111/nph.18585] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 10/24/2022] [Indexed: 06/16/2023]
Abstract
Plant tissues can be enriched in phytonutrients not only by stimulating their biosynthesis but also by providing appropriate sink structures for their sequestering and storage. In the case of carotenoids, they accumulate at high levels in chromoplasts naturally found in flowers and fruit. Chromoplasts can also be artificially differentiated from leaf chloroplasts by boosting carotenoid production with the bacterial protein crtB. Here we used electron and confocal microscopy together with subplastidial fractionation and transcript, protein and metabolite analyses to analyze the structural and biochemical changes occurring in crtB-induced artificial chromoplasts and their impact on the accumulation of health-related isoprenoids. We show that leaf chromoplasts develop plastoglobules (PG) harboring high levels of carotenoids (mainly phytoene and pro-vitamin A β-carotene) but also other nutritionally relevant isoprenoids, such as tocopherols (vitamin E) and phylloquinone (vitamin K1). Further promoting PG proliferation by exposure to intense (high) light resulted in a higher accumulation of these health-related metabolites but also an acceleration of the chloroplast-to-chromoplast conversion. We further show that the production of reactive oxygen species (ROS) stimulates chromoplastogenesis. Our data suggest that carotenoid accumulation and ROS production are not just consequences but promoters of the chromoplast differentiation process.
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Affiliation(s)
- Luca Morelli
- Institute for Plant Molecular and Cell Biology (IBMCP), CSIC-Universitat Politècnica de València, 46022, Valencia, Spain
- Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, 08193, Barcelona, Spain
| | - Salvador Torres-Montilla
- Institute for Plant Molecular and Cell Biology (IBMCP), CSIC-Universitat Politècnica de València, 46022, Valencia, Spain
| | - Gaétan Glauser
- Neuchâtel Platform of Analytical Chemistry, Faculty of Sciences, University of Neuchâtel, 2000, Neuchâtel, Switzerland
| | | | - Felix Kessler
- Laboratory of Plant Physiology, Faculty of Sciences, University of Neuchâtel, 2000, Neuchâtel, Switzerland
| | - Manuel Rodriguez-Concepcion
- Institute for Plant Molecular and Cell Biology (IBMCP), CSIC-Universitat Politècnica de València, 46022, Valencia, Spain
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8
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Morelli L, Torres-Montilla S, Glauser G, Shanmugabalaji V, Kessler F, Rodriguez-Concepcion M. Novel insights into the contribution of plastoglobules and reactive oxygen species to chromoplast differentiation. THE NEW PHYTOLOGIST 2023. [PMID: 36307969 DOI: 10.1101/2022.06.20.496796] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Plant tissues can be enriched in phytonutrients not only by stimulating their biosynthesis but also by providing appropriate sink structures for their sequestering and storage. In the case of carotenoids, they accumulate at high levels in chromoplasts naturally found in flowers and fruit. Chromoplasts can also be artificially differentiated from leaf chloroplasts by boosting carotenoid production with the bacterial protein crtB. Here we used electron and confocal microscopy together with subplastidial fractionation and transcript, protein and metabolite analyses to analyze the structural and biochemical changes occurring in crtB-induced artificial chromoplasts and their impact on the accumulation of health-related isoprenoids. We show that leaf chromoplasts develop plastoglobules (PG) harboring high levels of carotenoids (mainly phytoene and pro-vitamin A β-carotene) but also other nutritionally relevant isoprenoids, such as tocopherols (vitamin E) and phylloquinone (vitamin K1). Further promoting PG proliferation by exposure to intense (high) light resulted in a higher accumulation of these health-related metabolites but also an acceleration of the chloroplast-to-chromoplast conversion. We further show that the production of reactive oxygen species (ROS) stimulates chromoplastogenesis. Our data suggest that carotenoid accumulation and ROS production are not just consequences but promoters of the chromoplast differentiation process.
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Affiliation(s)
- Luca Morelli
- Institute for Plant Molecular and Cell Biology (IBMCP), CSIC-Universitat Politècnica de València, 46022, Valencia, Spain
- Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, 08193, Barcelona, Spain
| | - Salvador Torres-Montilla
- Institute for Plant Molecular and Cell Biology (IBMCP), CSIC-Universitat Politècnica de València, 46022, Valencia, Spain
| | - Gaétan Glauser
- Neuchâtel Platform of Analytical Chemistry, Faculty of Sciences, University of Neuchâtel, 2000, Neuchâtel, Switzerland
| | | | - Felix Kessler
- Laboratory of Plant Physiology, Faculty of Sciences, University of Neuchâtel, 2000, Neuchâtel, Switzerland
| | - Manuel Rodriguez-Concepcion
- Institute for Plant Molecular and Cell Biology (IBMCP), CSIC-Universitat Politècnica de València, 46022, Valencia, Spain
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9
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Morelli L, García Romañach L, Glauser G, Shanmugabalaji V, Kessler F, Rodriguez-Concepcion M. Nutritional Enrichment of Plant Leaves by Combining Genes Promoting Tocopherol Biosynthesis and Storage. Metabolites 2023; 13:metabo13020193. [PMID: 36837812 PMCID: PMC9965820 DOI: 10.3390/metabo13020193] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 01/18/2023] [Accepted: 01/25/2023] [Indexed: 01/31/2023] Open
Abstract
The enrichment of plant tissues in tocochromanols (tocopherols and tocotrienols) is an important biotechnological goal due to their vitamin E and antioxidant properties. Improvements based on stimulating tocochromanol biosynthesis have repeatedly been achieved, however, enhancing sequestering and storage in plant plastids remains virtually unexplored. We previously showed that leaf chloroplasts can be converted into artificial chromoplasts with a proliferation of plastoglobules by overexpression of the bacterial crtB gene. Here we combined coexpression of crtB with genes involved in tocopherol biosynthesis to investigate the potential of artificial leaf chromoplasts for vitamin E accumulation in Nicotiana benthamiana leaves. We show that this combination improves tocopherol levels compared to controls without crtB and confirm that VTE1, VTE5, VTE6 and tyrA genes are useful to increase the total tocopherol levels, while VTE4 further leads to enrichment in α-tocopherol (the tocochromanol showing highest vitamin E activity). Additionally, we show that treatments that further promote plastoglobule formation (e.g., exposure to intense light or dark-induced senescence) result in even higher improvements in the tocopherol content of the leaves. An added advantage of our strategy is that it also results in increased levels of other related plastidial isoprenoids such as carotenoids (provitamin A) and phylloquinones (vitamin K1).
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Affiliation(s)
- Luca Morelli
- Institute for Plant Molecular and Cell Biology (IBMCP), CSIC-Universitat Politècnica de València, 46022 Valencia, Spain
- Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, 08193 Barcelona, Spain
- Correspondence: (L.M.); (M.R.-C.)
| | - Laura García Romañach
- Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, 08193 Barcelona, Spain
| | - Gaetan Glauser
- Neuchâtel Platform of Analytical Chemistry, Faculty of Sciences, University of Neuchâtel, 2000 Neuchâtel, Switzerland
| | | | - Felix Kessler
- Laboratory of Plant Physiology, Faculty of Sciences, University of Neuchâtel, 2000 Neuchâtel, Switzerland
| | - Manuel Rodriguez-Concepcion
- Institute for Plant Molecular and Cell Biology (IBMCP), CSIC-Universitat Politècnica de València, 46022 Valencia, Spain
- Correspondence: (L.M.); (M.R.-C.)
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10
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Stra A, Almarwaey LO, Alagoz Y, Moreno JC, Al-Babili S. Carotenoid metabolism: New insights and synthetic approaches. FRONTIERS IN PLANT SCIENCE 2023; 13:1072061. [PMID: 36743580 PMCID: PMC9891708 DOI: 10.3389/fpls.2022.1072061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 12/29/2022] [Indexed: 06/18/2023]
Abstract
Carotenoids are well-known isoprenoid pigments naturally produced by plants, algae, photosynthetic bacteria as well as by several heterotrophic microorganisms. In plants, they are synthesized in plastids where they play essential roles in light-harvesting and in protecting the photosynthetic apparatus from reactive oxygen species (ROS). Carotenoids are also precursors of bioactive metabolites called apocarotenoids, including vitamin A and the phytohormones abscisic acid (ABA) and strigolactones (SLs). Genetic engineering of carotenogenesis made possible the enhancement of the nutritional value of many crops. New metabolic engineering approaches have recently been developed to modulate carotenoid content, including the employment of CRISPR technologies for single-base editing and the integration of exogenous genes into specific "safe harbors" in the genome. In addition, recent studies revealed the option of synthetic conversion of leaf chloroplasts into chromoplasts, thus increasing carotenoid storage capacity and boosting the nutritional value of green plant tissues. Moreover, transient gene expression through viral vectors allowed the accumulation of carotenoids outside the plastid. Furthermore, the utilization of engineered microorganisms allowed efficient mass production of carotenoids, making it convenient for industrial practices. Interestingly, manipulation of carotenoid biosynthesis can also influence plant architecture, and positively impact growth and yield, making it an important target for crop improvements beyond biofortification. Here, we briefly describe carotenoid biosynthesis and highlight the latest advances and discoveries related to synthetic carotenoid metabolism in plants and microorganisms.
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Affiliation(s)
- Alice Stra
- The Bioactives Laboratory, Center for Desert Agriculture, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
- Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Lamyaa O. Almarwaey
- The Bioactives Laboratory, Center for Desert Agriculture, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
- Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Yagiz Alagoz
- The Bioactives Laboratory, Center for Desert Agriculture, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
- Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Juan C. Moreno
- The Bioactives Laboratory, Center for Desert Agriculture, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
- Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Salim Al-Babili
- The Bioactives Laboratory, Center for Desert Agriculture, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
- Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
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Morelli L, Rodriguez-Concepcion M. Open avenues for carotenoid biofortification of plant tissues. PLANT COMMUNICATIONS 2023; 4:100466. [PMID: 36303429 PMCID: PMC9860184 DOI: 10.1016/j.xplc.2022.100466] [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: 08/29/2022] [Revised: 10/18/2022] [Accepted: 10/21/2022] [Indexed: 06/16/2023]
Abstract
Plant carotenoids are plastidial isoprenoids that function as photoprotectants, pigments, and precursors of apocarotenoids such as the hormones abscisic acid and strigolactones. Humans do not produce carotenoids but need to obtain them from their diet as precursors of retinoids, including vitamin A. Carotenoids also provide numerous other health benefits. Multiple attempts to improve the carotenoid profile of different crops have been carried out by manipulating carotenoid biosynthesis, degradation, and/or storage. Here, we will focus on open questions and emerging subjects related to the use of biotechnology for carotenoid biofortification. After impressive achievements, new efforts should be directed to extend the use of genome-editing technologies to overcome regulatory constraints and improve consumer acceptance of the carotenoid-enriched products. Another challenge is to prevent off-target effects like those resulting from altered hormone levels and metabolic homeostasis. Research on biofortification of green tissues should also look for new ways to deal with the negative impact that altered carotenoid contents may have on photosynthesis. Once a carotenoid-enriched product has been obtained, additional effort should be devoted to confirming that carotenoid intake from the engineered food is also improved. This work involves ensuring post-harvest stability and assessing bioaccessibility of the biofortified product to confirm that release of carotenoids from the food matrix has not been negatively affected. Successfully addressing these challenges will ensure new milestones in carotenoid biotechnology and biofortification.
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Affiliation(s)
- Luca Morelli
- Institute for Plant Molecular and Cell Biology (IBMCP), CSIC-Universitat Politècnica de València, 46022 Valencia, Spain
| | - Manuel Rodriguez-Concepcion
- Institute for Plant Molecular and Cell Biology (IBMCP), CSIC-Universitat Politècnica de València, 46022 Valencia, Spain.
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Hao DL, Zhou JY, Huang YN, Wang HR, Li XH, Guo HL, Liu JX. Roles of plastid-located phosphate transporters in carotenoid accumulation. FRONTIERS IN PLANT SCIENCE 2022; 13:1059536. [PMID: 36589064 PMCID: PMC9798012 DOI: 10.3389/fpls.2022.1059536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Accepted: 11/28/2022] [Indexed: 06/17/2023]
Abstract
Enhanced carotenoid accumulation in plants is crucial for the nutritional and health demands of the human body since these beneficial substances are acquired through dietary intake. Plastids are the major organelles to accumulate carotenoids in plants and it is reported that manipulation of a single plastid phosphate transporter gene enhances carotenoid accumulation. Amongst all phosphate transport proteins including phosphate transporters (PHTs), plastidial phosphate translocators (pPTs), PHOSPHATE1 (PHO1), vacuolar phosphate efflux transporter (VPE), and Sulfate transporter [SULTR]-like phosphorus distribution transporter (SPDT) in plants, plastidic PHTs (PHT2 & PHT4) are found as the only clade that is plastid located, and manipulation of which affects carotenoid accumulation. Manipulation of a single chromoplast PHT (PHT4;2) enhances carotenoid accumulation, whereas manipulation of a single chloroplast PHT has no impact on carotenoid accumulation. The underlying mechanism is mainly attributed to their different effects on plastid orthophosphate (Pi) concentration. PHT4;2 is the only chromoplast Pi efflux transporter, and manipulating this single chromoplast PHT significantly regulates chromoplast Pi concentration. This variation subsequently modulates the carotenoid accumulation by affecting the supply of glyceraldehyde 3-phosphate, a substrate for carotenoid biosynthesis, by modulating the transcript abundances of carotenoid biosynthesis limited enzyme genes, and by regulating chromoplast biogenesis (facilitating carotenoid storage). However, at least five orthophosphate influx PHTs are identified in the chloroplast, and manipulating one of the five does not substantially modulate the chloroplast Pi concentration in a long term due to their functional redundancy. This stable chloroplast Pi concentration upon one chloroplast PHT absence, therefore, is unable to modulate Pi-involved carotenoid accumulation processes and finally does affect carotenoid accumulation in photosynthetic tissues. Despite these advances, several cases including the precise location of plastid PHTs, the phosphate transport direction mediated by these plastid PHTs, the plastid PHTs participating in carotenoid accumulation signal pathway, the potential roles of these plastid PHTs in leaf carotenoid accumulation, and the roles of these plastid PHTs in other secondary metabolites are waiting for further research. The clarification of the above-mentioned cases is beneficial for breeding high-carotenoid accumulation plants (either in photosynthetic or non-photosynthetic edible parts of plants) through the gene engineering of these transporters.
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Affiliation(s)
- Dong-Li Hao
- The National Forestry and Grassland Administration Engineering Research Center for Germplasm Innovation and Utilization of Warm-Season Turfgrasses, Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing, China
| | - Jin-Yan Zhou
- Department of Agronomy and Horticulture, Jiangsu Vocational College of Agriculture and Forest, Jurong, China
| | - Ya-Nan Huang
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Nanjing, China
| | - Hao-Ran Wang
- The National Forestry and Grassland Administration Engineering Research Center for Germplasm Innovation and Utilization of Warm-Season Turfgrasses, Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing, China
| | - Xiao-Hui Li
- The National Forestry and Grassland Administration Engineering Research Center for Germplasm Innovation and Utilization of Warm-Season Turfgrasses, Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing, China
| | - Hai-Lin Guo
- The National Forestry and Grassland Administration Engineering Research Center for Germplasm Innovation and Utilization of Warm-Season Turfgrasses, Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing, China
| | - Jian-Xiu Liu
- The National Forestry and Grassland Administration Engineering Research Center for Germplasm Innovation and Utilization of Warm-Season Turfgrasses, Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing, China
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Rodriguez-Concepcion M, Daròs JA. Transient expression systems to rewire plant carotenoid metabolism. CURRENT OPINION IN PLANT BIOLOGY 2022; 66:102190. [PMID: 35183926 DOI: 10.1016/j.pbi.2022.102190] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Revised: 01/11/2022] [Accepted: 01/14/2022] [Indexed: 06/14/2023]
Abstract
Enrichment of foodstuffs with health-promoting metabolites such as carotenoids is a powerful tool to fight against unhealthy eating habits. Dietary carotenoids are vitamin A precursors and reduce risk of several chronical diseases. Additionally, carotenoids and their cleavage products (apocarotenoids) are used as natural pigments and flavors by the agrofood industry. In the last few years, major advances have been made in our understanding of how plants make and store carotenoids in their natural compartments, the plastids. In part, this knowledge has been acquired by using transient expression systems, notably agroinfiltration and viral vectors. These techniques allow profound changes in the carotenoid profile of plant tissues at the desired developmental stage, hence preventing interference with normal plant growth and development. Here we review how transient expression approaches have contributed to learn about the structure and regulation of plant carotenoid biosynthesis and to rewire carotenoid metabolism and storage for efficient biofortification of plant tissues.
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Affiliation(s)
- Manuel Rodriguez-Concepcion
- Institute for Plant Molecular and Cell Biology (IBMCP), Agencia Estatal Consejo Superior de Investigaciones Cientificas - Universitat Politècnica de València, 46022 Valencia, Spain.
| | - José-Antonio Daròs
- Institute for Plant Molecular and Cell Biology (IBMCP), Agencia Estatal Consejo Superior de Investigaciones Cientificas - Universitat Politècnica de València, 46022 Valencia, Spain
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Kapoor L, Simkin AJ, George Priya Doss C, Siva R. Fruit ripening: dynamics and integrated analysis of carotenoids and anthocyanins. BMC PLANT BIOLOGY 2022; 22:27. [PMID: 35016620 PMCID: PMC8750800 DOI: 10.1186/s12870-021-03411-w] [Citation(s) in RCA: 36] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 12/21/2021] [Indexed: 05/06/2023]
Abstract
BACKGROUND Fruits are vital food resources as they are loaded with bioactive compounds varying with different stages of ripening. As the fruit ripens, a dynamic color change is observed from green to yellow to red due to the biosynthesis of pigments like chlorophyll, carotenoids, and anthocyanins. Apart from making the fruit attractive and being a visual indicator of the ripening status, pigments add value to a ripened fruit by making them a source of nutraceuticals and industrial products. As the fruit matures, it undergoes biochemical changes which alter the pigment composition of fruits. RESULTS The synthesis, degradation and retention pathways of fruit pigments are mediated by hormonal, genetic, and environmental factors. Manipulation of the underlying regulatory mechanisms during fruit ripening suggests ways to enhance the desired pigments in fruits by biotechnological interventions. Here we report, in-depth insight into the dynamics of a pigment change in ripening and the regulatory mechanisms in action. CONCLUSIONS This review emphasizes the role of pigments as an asset to a ripened fruit as they augment the nutritive value, antioxidant levels and the net carbon gain of fruits; pigments are a source for fruit biofortification have tremendous industrial value along with being a tool to predict the harvest. This report will be of great utility to the harvesters, traders, consumers, and natural product divisions to extract the leading nutraceutical and industrial potential of preferred pigments biosynthesized at different fruit ripening stages.
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Affiliation(s)
- Leepica Kapoor
- Department of Biotechnology, School of Biosciences and Technology, Vellore Institute of Technology, Vellore, Tamil Nadu, 632014, India
| | - Andrew J Simkin
- School of Biosciences, University of Kent, United Kingdom, Canterbury, CT2 7NJ, UK
| | - C George Priya Doss
- Department of Biotechnology, School of Biosciences and Technology, Vellore Institute of Technology, Vellore, Tamil Nadu, 632014, India
| | - Ramamoorthy Siva
- Department of Biotechnology, School of Biosciences and Technology, Vellore Institute of Technology, Vellore, Tamil Nadu, 632014, India.
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A fast and simplified method to estimate bioaccessibility of carotenoids from plant tissues. Methods Enzymol 2022; 674:329-341. [DOI: 10.1016/bs.mie.2021.10.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Wu Q, Fu J, Sun J, Wang X, Tang X, Lu W, Tan C, Li L, Deng X, Xu Q. A plant CitPITP1 protein-coding exon sequence serves as a promoter in bacteria. J Biotechnol 2021; 339:1-13. [PMID: 34298024 DOI: 10.1016/j.jbiotec.2021.07.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 07/17/2021] [Accepted: 07/18/2021] [Indexed: 11/19/2022]
Abstract
Genetic manipulation of plant genes in prokaryotes has been widely used in molecular biology, but the function of a DNA sequence is far from being fully known. Here, we discovered that a plant protein-coding gene containing the CRAL_TRIO domain serves as a promoter in bacteria. We firstly characterized CitPITP1 from Citrus, which contains the CRAL_TRIO domain, and identified a 64-bp sequence (key64) that is critical for prokaryotic promoter activity. In vitro experiments indicated that the bacterial RNA polymerase subunit RpoD specifically binds to key64. We then expanded our research to fungi, plant and animal species to identify key64-like sequences. Five such prokaryotic promoters were isolated from Amborella, Rice, Arabidopsis and Citrus. Two conserved motifs were identified, and mutation analysis indicated that the nucleotides at positions 7, 29 and 30 are crucial for key64-like transcription activity. We detected full-length recombinant CitPITP1 from E. coli, and visualized a CitPITP1-GFP fusion protein in plant cells, supporting the idea that CitPITP1 encodes a protein. However, although exon 4 of CitPITP1 contained key64, it did not demonstrate promoter activity in plants. Our study describes a new basal promoter, provides evidence for neofunction of gene elements across different kingdoms, and provides new knowledge for the modular design of promoters.
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Affiliation(s)
- Qingjiang Wu
- Key Laboratory of Horticultural Plant Biology of Ministry of Education, Huazhong Agricultural University, Wuhan, 430000, China
| | - Jialing Fu
- Key Laboratory of Horticultural Plant Biology of Ministry of Education, Huazhong Agricultural University, Wuhan, 430000, China
| | - Juan Sun
- Key Laboratory of Horticultural Plant Biology of Ministry of Education, Huazhong Agricultural University, Wuhan, 430000, China
| | - Xia Wang
- Key Laboratory of Horticultural Plant Biology of Ministry of Education, Huazhong Agricultural University, Wuhan, 430000, China
| | - Xiaomei Tang
- Key Laboratory of Horticultural Plant Biology of Ministry of Education, Huazhong Agricultural University, Wuhan, 430000, China
| | - Wenjia Lu
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430000, China
| | - Chen Tan
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430000, China
| | - Li Li
- Plant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University, Ithaca, NY, 14853, USA; Robert W. Holley Center for Agriculture and Health, USDA-Agricultural Research Service, Cornell University, Ithaca, NY, 14853, USA
| | - Xiuxin Deng
- Key Laboratory of Horticultural Plant Biology of Ministry of Education, Huazhong Agricultural University, Wuhan, 430000, China
| | - Qiang Xu
- Key Laboratory of Horticultural Plant Biology of Ministry of Education, Huazhong Agricultural University, Wuhan, 430000, China.
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Dhami N. Chloroplast-to-chromoplast transition envisions provitamin A biofortification in green vegetables. PLANT CELL REPORTS 2021; 40:799-804. [PMID: 33754204 DOI: 10.1007/s00299-021-02684-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 03/15/2021] [Indexed: 06/12/2023]
Abstract
The carotenoids available in food are vital dietary micronutrients for human health. Plants synthesize and accumulate different carotenoids in plastids in a tissue-specific manner. The level of β-carotene (provitamin A) and other nutritionally important carotenoids is substantially low in the green tissues such as leaves compared to the fruits and roots. In photosynthetic tissues, chloroplasts can accumulate a moderate level of carotenoids, mainly to facilitate photosynthesis and environmental stress tolerance. However, chromoplasts from the storage tissues such as tomato fruit and carrot root can synthesize and accumulate carotenoids to a substantially higher level. A synthetic biology approach that utilizes a transient expression of bacterial phytoene synthase (crtB) gene in the photosynthetic leaves can induce the transition of chloroplasts into chromoplasts. The plastid-localized heterologous expression of crtB in leaves can induce the overaccumulation of phytoene, triggering the chloroplast-to-chromoplast transition; therefore, enhancing the biosynthesis and accumulation of carotenoids, including provitamin A. The transition of chloroplasts into chromoplasts, however, altered the photosynthetic thylakoids, consequently reducing the photosynthetic efficiency and plant growth. An efficient metabolic engineering strategy is desirable to enhance the production of targeted carotenoids in leaves without perturbing the photosynthetic efficiency and plant growth. Collectively, a synthetic biology strategy that triggers the transformation of chloroplasts into chromoplasts in photosynthetic tissues unfolds new avenues for carotenoid biofortification in the leafy food and vegetable crops, which can increase the dietary intake of carotenoids, therefore, combating the crisis of vitamin A deficiency.
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Affiliation(s)
- Namraj Dhami
- School of Health and Allied Sciences, Pokhara University, Pokhara 30, Dhungepatan, Pokhara, Gandaki, 33700, Nepal.
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