1
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Li N, Jarvis RP. Recruitment of Cdc48 to chloroplasts by a UBX-domain protein in chloroplast-associated protein degradation. NATURE PLANTS 2024:10.1038/s41477-024-01769-x. [PMID: 39160348 DOI: 10.1038/s41477-024-01769-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 07/20/2024] [Indexed: 08/21/2024]
Abstract
The translocon at the outer chloroplast membrane (TOC) is the gateway for chloroplast protein import and so is vital for photosynthetic establishment and plant growth. Chloroplast-associated protein degradation (CHLORAD) is a ubiquitin-dependent proteolytic system that regulates TOC. In CHLORAD, cytosolic Cdc48 provides motive force for the retrotranslocation of ubiquitinated TOC proteins to the cytosol but how Cdc48 is recruited is unknown. Here, we identify plant UBX-domain protein PUX10 as a component of the CHLORAD machinery. We show that PUX10 is an integral chloroplast outer membrane protein that projects UBX and ubiquitin-associated domains into the cytosol. It interacts with Cdc48 via its UBX domain, bringing it to the chloroplast surface, and with ubiquitinated TOC proteins via its ubiquitin-associated domain. Genetic analyses in Arabidopsis revealed a requirement for PUX10 during CHLORAD-mediated regulation of TOC function and plant development. Thus, PUX10 coordinates ubiquitination and retrotranslocation activities of CHLORAD to enable efficient TOC turnover.
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Affiliation(s)
- Na Li
- Section of Molecular Plant Biology, Department of Biology, University of Oxford, Oxford, UK
| | - R Paul Jarvis
- Section of Molecular Plant Biology, Department of Biology, University of Oxford, Oxford, UK.
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2
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Schwenkert S, Lo WT, Szulc B, Yip CK, Pratt AI, Cusack SA, Brandt B, Leister D, Kunz HH. Probing the physiological role of the plastid outer-envelope membrane using the oemiR plasmid collection. G3 (BETHESDA, MD.) 2023; 13:jkad187. [PMID: 37572358 PMCID: PMC10542568 DOI: 10.1093/g3journal/jkad187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 07/20/2023] [Accepted: 08/04/2023] [Indexed: 08/14/2023]
Abstract
Plastids are the site of complex biochemical pathways, most prominently photosynthesis. The organelle evolved through endosymbiosis with a cyanobacterium, which is exemplified by the outer envelope membrane that harbors more than 40 proteins in Arabidopsis. Their evolutionary conservation indicates high significance for plant cell function. While a few proteins are well-studied as part of the protein translocon complex the majority of outer envelope protein functions is unclear. Gaining a deeper functional understanding has been complicated by the lack of observable loss-of-function mutant phenotypes, which is often rooted in functional genetic redundancy. Therefore, we designed outer envelope-specific artificial micro RNAs (oemiRs) capable of downregulating transcripts from several loci simultaneously. We successfully tested oemiR function by performing a proof-of-concept screen for pale and cold-sensitive mutants. An in-depth analysis of pale mutant alleles deficient in the translocon component TOC75 using proteomics provided new insights into putative compensatory import pathways. The cold stress screen not only recapitulated 3 previously known phenotypes of cold-sensitive mutants but also identified 4 mutants of additional oemiR outer envelope loci. Altogether our study revealed a role of the outer envelope to tolerate cold conditions and showcasts the power of the oemiR collection to research the significance of outer envelope proteins.
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Affiliation(s)
- Serena Schwenkert
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität Munich, 82152 Planegg-Martinsried, Germany
| | - Wing Tung Lo
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität Munich, 82152 Planegg-Martinsried, Germany
| | - Beata Szulc
- Plant Biochemistry, Faculty of Biology, Ludwig-Maximilians-Universität Munich, 82152 Planegg-Martinsried, Germany
| | - Chun Kwan Yip
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität Munich, 82152 Planegg-Martinsried, Germany
| | - Anna I Pratt
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA 99164-4236, USA
| | | | - Benjamin Brandt
- Plant Biochemistry, Faculty of Biology, Ludwig-Maximilians-Universität Munich, 82152 Planegg-Martinsried, Germany
| | - Dario Leister
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität Munich, 82152 Planegg-Martinsried, Germany
| | - Hans-Henning Kunz
- Plant Biochemistry, Faculty of Biology, Ludwig-Maximilians-Universität Munich, 82152 Planegg-Martinsried, Germany
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA 99164-4236, USA
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3
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Nellaepalli S, Lau AS, Jarvis RP. Chloroplast protein translocation pathways and ubiquitin-dependent regulation at a glance. J Cell Sci 2023; 136:jcs241125. [PMID: 37732520 PMCID: PMC10546890 DOI: 10.1242/jcs.241125] [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] [Indexed: 09/22/2023] Open
Abstract
Chloroplasts conduct photosynthesis and numerous metabolic and signalling processes that enable plant growth and development. Most of the ∼3000 proteins in chloroplasts are nucleus encoded and must be imported from the cytosol. Thus, the protein import machinery of the organelle (the TOC-TIC apparatus) is of fundamental importance for chloroplast biogenesis and operation. Cytosolic factors target chloroplast precursor proteins to the TOC-TIC apparatus, which drives protein import across the envelope membranes into the organelle, before various internal systems mediate downstream routing to different suborganellar compartments. The protein import system is proteolytically regulated by the ubiquitin-proteasome system (UPS), enabling centralized control over the organellar proteome. In addition, the UPS targets a range of chloroplast proteins directly. In this Cell Science at a Glance article and the accompanying poster, we present mechanistic details of these different chloroplast protein targeting and translocation events, and of the UPS systems that regulate chloroplast proteins.
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Affiliation(s)
- Sreedhar Nellaepalli
- Section of Molecular Plant Biology, Department of Biology, University of Oxford, Oxford OX1 3RB, UK
| | - Anne Sophie Lau
- Section of Molecular Plant Biology, Department of Biology, University of Oxford, Oxford OX1 3RB, UK
- Department of Plant Physiology, Faculty of Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - R. Paul Jarvis
- Section of Molecular Plant Biology, Department of Biology, University of Oxford, Oxford OX1 3RB, UK
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4
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Wan C, Zhang H, Cheng H, Sowden RG, Cai W, Jarvis RP, Ling Q. Selective autophagy regulates chloroplast protein import and promotes plant stress tolerance. EMBO J 2023; 42:e112534. [PMID: 37248861 PMCID: PMC10350842 DOI: 10.15252/embj.2022112534] [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: 09/05/2022] [Revised: 03/26/2023] [Accepted: 05/09/2023] [Indexed: 05/31/2023] Open
Abstract
Chloroplasts are plant organelles responsible for photosynthesis and environmental sensing. Most chloroplast proteins are imported from the cytosol through the translocon at the outer envelope membrane of chloroplasts (TOC). Previous work has shown that TOC components are regulated by the ubiquitin-proteasome system (UPS) to control the chloroplast proteome, which is crucial for the organelle's function and plant development. Here, we demonstrate that the TOC apparatus is also subject to K63-linked polyubiquitination and regulation by selective autophagy, potentially promoting plant stress tolerance. We identify NBR1 as a selective autophagy adaptor targeting TOC components, and mediating their relocation into vacuoles for autophagic degradation. Such selective autophagy is shown to control TOC protein levels and chloroplast protein import and to influence photosynthetic activity as well as tolerance to UV-B irradiation and heat stress in Arabidopsis plants. These findings uncover the vital role of selective autophagy in the proteolytic regulation of specific chloroplast proteins, and how dynamic control of chloroplast protein import is critically important for plants to cope with challenging environments.
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Affiliation(s)
- Chen Wan
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and EcologyChinese Academy of SciencesShanghaiChina
- University of Chinese Academy of SciencesBeijingChina
| | - Hui Zhang
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and EcologyChinese Academy of SciencesShanghaiChina
| | - Hongying Cheng
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and EcologyChinese Academy of SciencesShanghaiChina
- University of Chinese Academy of SciencesBeijingChina
| | - Robert G Sowden
- Department of Plant Sciences and Section of Molecular Plant Biology (Department of Biology)University of OxfordOxfordUK
| | - Wenjuan Cai
- Core Facility Center, CAS Centre for Excellence in Molecular Plant SciencesChinese Academy of SciencesShanghaiChina
| | - R Paul Jarvis
- Department of Plant Sciences and Section of Molecular Plant Biology (Department of Biology)University of OxfordOxfordUK
| | - Qihua Ling
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and EcologyChinese Academy of SciencesShanghaiChina
- University of Chinese Academy of SciencesBeijingChina
- CAS‐JIC Center of Excellence for Plant and Microbial Sciences (CEPAMS), Institute of Plant Physiology and EcologyChinese Academy of SciencesShanghaiChina
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5
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Ballabani G, Forough M, Kessler F, Shanmugabalaji V. The journey of preproteins across the chloroplast membrane systems. Front Physiol 2023; 14:1213866. [PMID: 37324391 PMCID: PMC10267391 DOI: 10.3389/fphys.2023.1213866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 05/22/2023] [Indexed: 06/17/2023] Open
Abstract
The photosynthetic capacity of chloroplasts is vital for autotrophic growth in algae and plants. The origin of the chloroplast has been explained by the endosymbiotic theory that proposes the engulfment of a cyanobacterium by an ancestral eukaryotic cell followed by the transfer of many cyanobacterial genes to the host nucleus. As a result of the gene transfer, the now nuclear-encoded proteins acquired chloroplast targeting peptides (known as transit peptides; transit peptide) and are translated as preproteins in the cytosol. Transit peptides contain specific motifs and domains initially recognized by cytosolic factors followed by the chloroplast import components at the outer and inner envelope of the chloroplast membrane. Once the preprotein emerges on the stromal side of the chloroplast protein import machinery, the transit peptide is cleaved by stromal processing peptidase. In the case of thylakoid-localized proteins, cleavage of the transit peptides may expose a second targeting signal guiding the protein to the thylakoid lumen or allow insertion into the thylakoid membrane by internal sequence information. This review summarizes the common features of targeting sequences and describes their role in routing preproteins to and across the chloroplast envelope as well as the thylakoid membrane and lumen.
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Affiliation(s)
| | | | - Felix Kessler
- *Correspondence: Felix Kessler, ; Venkatasalam Shanmugabalaji,
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6
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Srinivasan K, Erramilli SK, Chakravarthy S, Gonzalez A, Kossiakoff A, Noinaj N. Characterization of synthetic antigen binding fragments targeting Toc75 for the isolation of TOC in A. thaliana and P. sativum. Structure 2023; 31:595-606.e5. [PMID: 36977410 PMCID: PMC10164082 DOI: 10.1016/j.str.2023.03.002] [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: 07/15/2022] [Revised: 12/21/2022] [Accepted: 03/02/2023] [Indexed: 03/29/2023]
Abstract
Roughly 95% of the proteins that make up the chloroplast must be imported from the cytoplasm. The machinery responsible for the translocation of these cargo proteins is called the translocon at the outer membrane of chloroplast (TOC). The TOC core consists of three proteins, Toc34, Toc75, and Toc159; no high-resolution structure has been solved of fully assembled TOC from plants. Efforts toward determining the structure of the TOC have been hindered almost entirely by difficulties in producing sufficient yields for structural studies. In this study, we introduce an innovative method that utilizes synthetic antigen binding fragments (sABs) to isolate TOC directly from wild-type plant biomass including A. thaliana and P. sativum. Binding between the sABs and the POTRA domains was characterized by size-exclusion chromatography coupled with small-angle X-ray scattering (SEC-SAXS), X-ray crystallography, and isothermal titration calorimetry. We also demonstrate the isolation of the TOC from P. sativum, laying the framework for large-scale isolation and purification of TOC for functional and structural studies.
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Affiliation(s)
- Karthik Srinivasan
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Satchal K Erramilli
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Srinivas Chakravarthy
- The Biophysics Collaborative Access Team (BioCAT), Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL, USA
| | - Adrian Gonzalez
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Anthony Kossiakoff
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Nicholas Noinaj
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA.
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7
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Christian R, Labbancz J, Usadel B, Dhingra A. Understanding protein import in diverse non-green plastids. Front Genet 2023; 14:969931. [PMID: 37007964 PMCID: PMC10063809 DOI: 10.3389/fgene.2023.969931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 02/24/2023] [Indexed: 03/19/2023] Open
Abstract
The spectacular diversity of plastids in non-green organs such as flowers, fruits, roots, tubers, and senescing leaves represents a Universe of metabolic processes in higher plants that remain to be completely characterized. The endosymbiosis of the plastid and the subsequent export of the ancestral cyanobacterial genome to the nuclear genome, and adaptation of the plants to all types of environments has resulted in the emergence of diverse and a highly orchestrated metabolism across the plant kingdom that is entirely reliant on a complex protein import and translocation system. The TOC and TIC translocons, critical for importing nuclear-encoded proteins into the plastid stroma, remain poorly resolved, especially in the case of TIC. From the stroma, three core pathways (cpTat, cpSec, and cpSRP) may localize imported proteins to the thylakoid. Non-canonical routes only utilizing TOC also exist for the insertion of many inner and outer membrane proteins, or in the case of some modified proteins, a vesicular import route. Understanding this complex protein import system is further compounded by the highly heterogeneous nature of transit peptides, and the varying transit peptide specificity of plastids depending on species and the developmental and trophic stage of the plant organs. Computational tools provide an increasingly sophisticated means of predicting protein import into highly diverse non-green plastids across higher plants, which need to be validated using proteomics and metabolic approaches. The myriad plastid functions enable higher plants to interact and respond to all kinds of environments. Unraveling the diversity of non-green plastid functions across the higher plants has the potential to provide knowledge that will help in developing climate resilient crops.
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Affiliation(s)
- Ryan Christian
- Department of Horticulture, Washington State University, Pullman, WA, United States
| | - June Labbancz
- Department of Horticulture, Washington State University, Pullman, WA, United States
- Department of Horticultural Sciences, Texas A&M University, College Station, TX, United States
| | | | - Amit Dhingra
- Department of Horticulture, Washington State University, Pullman, WA, United States
- Department of Horticultural Sciences, Texas A&M University, College Station, TX, United States
- *Correspondence: Amit Dhingra,
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8
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Architecture of chloroplast TOC-TIC translocon supercomplex. Nature 2023; 615:349-357. [PMID: 36702157 DOI: 10.1038/s41586-023-05744-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 01/19/2023] [Indexed: 01/27/2023]
Abstract
Chloroplasts rely on the translocon complexes in the outer and inner envelope membranes (the TOC and TIC complexes, respectively) to import thousands of different nuclear-encoded proteins from the cytosol1-4. Although previous studies indicated that the TOC and TIC complexes may assemble into larger supercomplexes5-7, the overall architectures of the TOC-TIC supercomplexes and the mechanism of preprotein translocation are unclear. Here we report the cryo-electron microscopy structure of the TOC-TIC supercomplex from Chlamydomonas reinhardtii. The major subunits of the TOC complex (Toc75, Toc90 and Toc34) and TIC complex (Tic214, Tic20, Tic100 and Tic56), three chloroplast translocon-associated proteins (Ctap3, Ctap4 and Ctap5) and three newly identified small inner-membrane proteins (Simp1-3) have been located in the supercomplex. As the largest protein, Tic214 traverses the inner membrane, the intermembrane space and the outer membrane, connecting the TOC complex with the TIC proteins. An inositol hexaphosphate molecule is located at the Tic214-Toc90 interface and stabilizes their assembly. Four lipid molecules are located within or above an inner-membrane funnel formed by Tic214, Tic20, Simp1 and Ctap5. Multiple potential pathways found in the TOC-TIC supercomplex may support translocation of different substrate preproteins into chloroplasts.
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9
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Mohd Ali S, Li N, Soufi Z, Yao J, Johnson E, Ling Q, Jarvis RP. Multiple ubiquitin E3 ligase genes antagonistically regulate chloroplast-associated protein degradation. Curr Biol 2023; 33:1138-1146.e5. [PMID: 36822201 DOI: 10.1016/j.cub.2023.01.060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 12/02/2022] [Accepted: 01/26/2023] [Indexed: 02/24/2023]
Abstract
The chloroplast is the most prominent member of a diverse group of plant organelles called the plastids, and it is characterized by its vital role in photosynthesis. 1,2,3 Most of the ∼3,000 different proteins in chloroplasts are synthesized in the cytosol in precursor (preprotein) form, each with a cleavable transit peptide. 4,5,6,7,8 Preproteins are imported via translocons in the outer and inner envelope membranes of the chloroplast, termed TOC and TIC, respectively. 9,10,11,12,13 Discovery of the chloroplast-localized ubiquitin E3 ligase SUPPRESSOR OF PPI1 LOCUS1 (SP1) demonstrated that the nucleocytosolic ubiquitin-proteasome system (UPS) targets the TOC apparatus to dynamically control protein import and chloroplast biogenesis in response to developmental and environmental cues. The relevant UPS pathway is termed chloroplast-associated protein degradation (CHLORAD). 14,15,16 Two homologs of SP1 exist, SP1-like1 (SPL1) and SPL2, but their roles have remained obscure. Here, we show that SP1 is ubiquitous in the Viridiplantae and that SPL2 and SPL1 appeared early during the evolution of the Viridiplantae and land plants, respectively. Through genetic and biochemical analysis, we reveal that SPL1 functions as a negative regulator of SP1, potentially by interfering with its ability to catalyze ubiquitination. In contrast, SPL2, the more distantly related SP1 homolog, displays partial functional redundancy with SP1. Both SPL1 and SPL2 modify the extent of leaf senescence, like SP1, but do so in diametrically opposite ways. Thus, SPL1 and SPL2 are bona fide CHLORAD system components with negative and positive regulatory functions that allow for nuanced control of this vital proteolytic pathway.
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Affiliation(s)
- Sabri Mohd Ali
- Section of Molecular Plant Biology (Department of Biology) and Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
| | - Na Li
- Section of Molecular Plant Biology (Department of Biology) and Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
| | - Ziad Soufi
- Section of Molecular Plant Biology (Department of Biology) and Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
| | - Jinrong Yao
- University of Chinese Academy of Sciences, Beijing 100049, China; National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
| | - Errin Johnson
- The Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Qihua Ling
- Section of Molecular Plant Biology (Department of Biology) and Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK; National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
| | - R Paul Jarvis
- Section of Molecular Plant Biology (Department of Biology) and Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK.
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10
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Gao LL, Hong ZH, Wang Y, Wu GZ. Chloroplast proteostasis: A story of birth, life, and death. PLANT COMMUNICATIONS 2023; 4:100424. [PMID: 35964157 PMCID: PMC9860172 DOI: 10.1016/j.xplc.2022.100424] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 08/02/2022] [Accepted: 08/10/2022] [Indexed: 06/02/2023]
Abstract
Protein homeostasis (proteostasis) is a dynamic balance of protein synthesis and degradation. Because of the endosymbiotic origin of chloroplasts and the massive transfer of their genetic information to the nucleus of the host cell, many protein complexes in the chloroplasts are constituted from subunits encoded by both genomes. Hence, the proper function of chloroplasts relies on the coordinated expression of chloroplast- and nucleus-encoded genes. The biogenesis and maintenance of chloroplast proteostasis are dependent on synthesis of chloroplast-encoded proteins, import of nucleus-encoded chloroplast proteins from the cytosol, and clearance of damaged or otherwise undesired "old" proteins. This review focuses on the regulation of chloroplast proteostasis, its interaction with proteostasis of the cytosol, and its retrograde control over nuclear gene expression. We also discuss significant issues and perspectives for future studies and potential applications for improving the photosynthetic performance and stress tolerance of crops.
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Affiliation(s)
- Lin-Lin Gao
- Shanghai Collaborative Innovation Center of Agri-Seeds, School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China; Joint Center for Single Cell Biology, School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Zheng-Hui Hong
- Shanghai Collaborative Innovation Center of Agri-Seeds, School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China; Joint Center for Single Cell Biology, School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Yinsong Wang
- Shanghai Collaborative Innovation Center of Agri-Seeds, School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China; Joint Center for Single Cell Biology, School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Guo-Zhang Wu
- Shanghai Collaborative Innovation Center of Agri-Seeds, School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China; Joint Center for Single Cell Biology, School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China.
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11
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Structure of a TOC-TIC supercomplex spanning two chloroplast envelope membranes. Cell 2022; 185:4788-4800.e13. [PMID: 36413996 DOI: 10.1016/j.cell.2022.10.030] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 09/07/2022] [Accepted: 10/28/2022] [Indexed: 11/23/2022]
Abstract
The TOC and TIC complexes are essential translocons that facilitate the import of the nuclear genome-encoded preproteins across the two envelope membranes of chloroplast, but their exact molecular identities and assembly remain unclear. Here, we report a cryoelectron microscopy structure of TOC-TIC supercomplex from Chlamydomonas, containing a total of 14 identified components. The preprotein-conducting pore of TOC is a hybrid β-barrel co-assembled by Toc120 and Toc75, while the potential translocation path of TIC is formed by transmembrane helices from Tic20 and YlmG, rather than a classic model of Tic110. A rigid intermembrane space (IMS) scaffold bridges two chloroplast membranes, and a large hydrophilic cleft on the IMS scaffold connects TOC and TIC, forming a pathway for preprotein translocation. Our study provides structural insights into the TOC-TIC supercomplex composition, assembly, and preprotein translocation mechanism, and lays a foundation to interpret the evolutionary conservation and diversity of this fundamental translocon machinery.
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12
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Liebers M, Cozzi C, Uecker F, Chambon L, Blanvillain R, Pfannschmidt T. Biogenic signals from plastids and their role in chloroplast development. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:7105-7125. [PMID: 36002302 DOI: 10.1093/jxb/erac344] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 08/23/2022] [Indexed: 06/15/2023]
Abstract
Plant seeds do not contain differentiated chloroplasts. Upon germination, the seedlings thus need to gain photoautotrophy before storage energies are depleted. This requires the coordinated expression of photosynthesis genes encoded in nuclear and plastid genomes. Chloroplast biogenesis needs to be additionally coordinated with the light regulation network that controls seedling development. This coordination is achieved by nucleus to plastid signals called anterograde and plastid to nucleus signals termed retrograde. Retrograde signals sent from plastids during initial chloroplast biogenesis are also called biogenic signals. They have been recognized as highly important for proper chloroplast biogenesis and for seedling development. The molecular nature, transport, targets, and signalling function of biogenic signals are, however, under debate. Several studies disproved the involvement of a number of key components that were at the base of initial models of retrograde signalling. New models now propose major roles for a functional feedback between plastid and cytosolic protein homeostasis in signalling plastid dysfunction as well as the action of dually localized nucleo-plastidic proteins that coordinate chloroplast biogenesis with light-dependent control of seedling development. This review provides a survey of the developments in this research field, summarizes the unsolved questions, highlights several recent advances, and discusses potential new working modes.
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Affiliation(s)
- Monique Liebers
- Gottfried-Wilhelm-Leibniz-Universität Hannover, Naturwissenschaftliche Fakultät, Institut für Botanik, Pflanzenphysiologie, Herrenhäuser Str. 2, D-30419 Hannover, Germany
| | - Carolina Cozzi
- Gottfried-Wilhelm-Leibniz-Universität Hannover, Naturwissenschaftliche Fakultät, Institut für Botanik, Pflanzenphysiologie, Herrenhäuser Str. 2, D-30419 Hannover, Germany
| | - Finia Uecker
- Gottfried-Wilhelm-Leibniz-Universität Hannover, Naturwissenschaftliche Fakultät, Institut für Botanik, Pflanzenphysiologie, Herrenhäuser Str. 2, D-30419 Hannover, Germany
| | - Louise Chambon
- Université Grenoble-Alpes, CNRS, CEA, INRA, IRIG-LPCV, F-38000 Grenoble, France
| | - Robert Blanvillain
- Université Grenoble-Alpes, CNRS, CEA, INRA, IRIG-LPCV, F-38000 Grenoble, France
| | - Thomas Pfannschmidt
- Gottfried-Wilhelm-Leibniz-Universität Hannover, Naturwissenschaftliche Fakultät, Institut für Botanik, Pflanzenphysiologie, Herrenhäuser Str. 2, D-30419 Hannover, Germany
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13
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Sun Y, Yao Z, Ye Y, Fang J, Chen H, Lyu Y, Broad W, Fournier M, Chen G, Hu Y, Mohammed S, Ling Q, Jarvis RP. Ubiquitin-based pathway acts inside chloroplasts to regulate photosynthesis. SCIENCE ADVANCES 2022; 8:eabq7352. [PMID: 36383657 PMCID: PMC9668298 DOI: 10.1126/sciadv.abq7352] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Photosynthesis is the energetic basis for most life on Earth, and in plants it operates inside double membrane-bound organelles called chloroplasts. The photosynthetic apparatus comprises numerous proteins encoded by the nuclear and organellar genomes. Maintenance of this apparatus requires the action of internal chloroplast proteases, but a role for the nucleocytosolic ubiquitin-proteasome system (UPS) was not expected, owing to the barrier presented by the double-membrane envelope. Here, we show that photosynthesis proteins (including those encoded internally by chloroplast genes) are ubiquitinated and processed via the CHLORAD pathway: They are degraded by the 26S proteasome following CDC48-dependent retrotranslocation to the cytosol. This demonstrates that the reach of the UPS extends to the interior of endosymbiotically derived chloroplasts, where it acts to regulate photosynthesis, arguably the most fundamental process of life.
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Affiliation(s)
- Yi Sun
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
| | - Zujie Yao
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
| | - Yiting Ye
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Jun Fang
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
| | - Honglin Chen
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Yuping Lyu
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
- Shanghai Chenshan Plant Science Research Center, Chinese Academy of Sciences, Shanghai, China
| | - William Broad
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
| | - Marjorie Fournier
- Advanced Proteomics Facility, University of Oxford, Oxford OX1 3QU, UK
| | - Genyun Chen
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
| | - Yonghong Hu
- Shanghai Chenshan Plant Science Research Center, Chinese Academy of Sciences, Shanghai, China
| | - Shabaz Mohammed
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
- Department of Chemistry, University of Oxford, Oxford OX1 3TA, UK
- Rosalind Franklin Institute, Oxfordshire OX11 0FA, UK
| | - Qihua Ling
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
- CAS-JIC Center of Excellence for Plant and Microbial Sciences (CEPAMS), Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
- Corresponding author. (Q.L.); (R.P.J.)
| | - R. Paul Jarvis
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
- Corresponding author. (Q.L.); (R.P.J.)
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14
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Wang Q, Yue J, Zhang C, Yan J. Split-Ubiquitin Two-Hybrid Screen for Proteins Interacting with slToc159-1 and slToc159-2, Two Chloroplast Preprotein Import Receptors in Tomato ( Solanum lycopersicum). PLANTS (BASEL, SWITZERLAND) 2022; 11:2923. [PMID: 36365376 PMCID: PMC9654457 DOI: 10.3390/plants11212923] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 10/24/2022] [Accepted: 10/26/2022] [Indexed: 06/16/2023]
Abstract
The post-translational import of nuclear-encoded chloroplast preproteins is critical for chloroplast biogenesis, and the Toc159 family of proteins is the receptor for this process. Our previous work identified and analyzed the Toc GTPase in tomato; however, the tomato-specific transport substrate for Toc159 is still unknown, which limits the study of the function of the TOC receptor in tomato. In this study, we expand the number of preprotein substrates of slToc159 receptor family members using slToc159-1 and slToc159-2 as bait via a split-ubiquitin yeast two-hybrid membrane system. Forty-one specific substrates were identified in tomato for the first time. Using slToc159-1GM and slToc159-2GM as bait, we compared the affinity of the two bait proteins, with and without the A domain, to the precursor protein, which suggested that the A domain endowed the proproteins with subclass specificity. The presence of the A domain enhanced the interaction intensity of slToc159-1 with the photosynthetic preprotein but decreased the interaction intensity of slToc159-2 with the photosynthetic preprotein. Similarly, the presence of the A domain also altered the affinity of slToc159 to non-photosynthetic preproteins. Bimolecular fluorescence complementation (BiFC) analysis showed that A domain had the ability to recognize the preprotein, and the interaction occurred in the chloroplast. Further, the localization of the A domain in Arabidopsis protoplasts showed that the A domain did not contain chloroplast membrane targeting signals. Our data demonstrate the importance of a highly non-conserved A domain, which endows the slToc159 receptor with specificity for different protein types. However, the domain containing the information on targeting the chloroplast needs further study.
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Affiliation(s)
- Qi Wang
- College of Agriculture, Guizhou University, Guiyang 550025, China
- Vegetable Research Academy, Guizhou University, Guiyang 550025, China
| | - Jiang Yue
- College of Agriculture, Guizhou University, Guiyang 550025, China
- Vegetable Research Academy, Guizhou University, Guiyang 550025, China
| | - Chaozhong Zhang
- College of Agriculture, Guizhou University, Guiyang 550025, China
- Vegetable Research Academy, Guizhou University, Guiyang 550025, China
| | - Jianmin Yan
- College of Agriculture, Guizhou University, Guiyang 550025, China
- Vegetable Research Academy, Guizhou University, Guiyang 550025, China
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15
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Zhao X, Higa T, Nakai M. Tic12, a 12-kDa essential component of the translocon at the inner envelope membrane of chloroplasts in Arabidopsis. THE PLANT CELL 2022; 34:4569-4582. [PMID: 35929083 PMCID: PMC9614449 DOI: 10.1093/plcell/koac240] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 07/15/2022] [Indexed: 06/15/2023]
Abstract
The complexes translocon at the outer envelope membrane of chloroplasts and translocon at the inner envelope membrane of chloroplasts (TIC) mediate preprotein translocation across the chloroplast outer and inner envelope membranes, respectively. Tic20, Tic56, Tic100, and Tic214 form a stable one-megadalton TIC whose function is essential for Arabidopsis thaliana and Chlamydomonas reinhardtii. Tic20 plays a central role in preprotein translocation by forming a protein-conducting channel. Tic56, Tic100, and Tic214 are also indispensable for TIC function, but whether other components are required for this process remain unclear. Here, we demonstrate that a 12-kDa protein named Tic12 is part of the TIC in A. thaliana and participates in preprotein translocation across the inner envelope membrane. Tic12 was tightly associated with the TIC but disassociated under high-salt conditions in combination with Triton X-100. Site-specific UV crosslinking experiments revealed that Tic12 and Tic20 directly interact with the transit peptide of a translocating preprotein. The tic12 null mutants are albino and seedling lethal, similar to the other tic null mutants. Tic12 and Tic20 were also involved in preprotein translocation in (Pisum sativum) pea chloroplasts. Thus, Tic12 is an essential constituent that forms the functional core together with Tic20 in the one-megadalton TIC.
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Affiliation(s)
- Xueyang Zhao
- Institute for Protein Research, Osaka University, Suita, 565-0871, Japan
| | - Takeshi Higa
- Institute for Protein Research, Osaka University, Suita, 565-0871, Japan
| | - Masato Nakai
- Institute for Protein Research, Osaka University, Suita, 565-0871, Japan
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16
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Rodamilans B, Oliveros JC, San León D, Martínez-García PJ, Martínez-Gómez P, García JA, Rubio M. sRNA Analysis Evidenced the Involvement of Different Plant Viruses in the Activation of RNA Silencing-Related Genes and the Defensive Response Against Plum pox virus of 'GF305' Peach Grafted with 'Garrigues' Almond. PHYTOPATHOLOGY 2022; 112:2012-2021. [PMID: 35302895 DOI: 10.1094/phyto-01-22-0032-r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Plum pox virus (PPV) causes sharka disease in Prunus trees. Peach (P. persica) trees are severely affected by PPV, and no definitive source of genetic resistance has been identified. However, previous results showed that PPV-resistant 'Garrigues' almond (P. dulcis) was able to transfer its resistance to 'GF305' peach through grafting, reducing symptoms and viral load in PPV-infected plants. A recent study tried to identify genes responsible for this effect by studying messenger RNA expression through RNA sequencing in peach and almond plants, before and after grafting and before and after PPV infection. In this work, we used the same peach and almond samples but focused the high-throughput analyses on small RNA (sRNA) expression. We studied massive sequencing data and found an interesting pattern of sRNA overexpression linked to antiviral defense genes that suggested activation of these genes followed by downregulation to basal levels. We also discovered that 'Garrigues' almond plants were infected by different plant viruses that were transferred to peach plants. The large amounts of viral sRNA found in grafted peaches indicated a strong RNA silencing antiviral response and led us to postulate that these plant viruses could be collaborating in the observed "Garrigues effect."
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Affiliation(s)
| | - Juan C Oliveros
- Department of Plant Molecular Genetics, CNB-CSIC, 28049 Madrid, Spain
| | - David San León
- Department of Plant Molecular Genetics, CNB-CSIC, 28049 Madrid, Spain
| | | | | | - Juan A García
- Department of Plant Molecular Genetics, CNB-CSIC, 28049 Madrid, Spain
| | - Manuel Rubio
- Department of Plant Breeding, CEBAS-CSIC, 30100 Murcia, Spain
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17
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Jeong J, Moon B, Hwang I, Lee DW. GREEN FLUORESCENT PROTEIN variants with enhanced folding are more efficiently imported into chloroplasts. PLANT PHYSIOLOGY 2022; 190:238-249. [PMID: 35699510 PMCID: PMC9434181 DOI: 10.1093/plphys/kiac291] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 06/05/2022] [Indexed: 06/15/2023]
Abstract
Chloroplasts and mitochondria are subcellular organelles that evolved from cyanobacteria and α-proteobacteria, respectively. Although they have their own genomes, the majority of their proteins are encoded by nuclear genes, translated by cytosolic ribosomes, and imported via outer and inner membrane translocon complexes. The unfolding of mature regions of proteins is thought to be a prerequisite for the import of the proteins into these organelles. However, it is not fully understood how protein folding properties affect their import into these organelles. In this study, we examined the import behavior of chloroplast and mitochondrial reporters with normal green fluorescent protein (GFP) and two GFP variants with enhanced folding propensity, superfolder GFP (sfGFP) and extra-superfolder GFP (esGFP), which is folded better than sfGFP. sfGFP and esGFP were less dependent on the sequence motifs of the transit peptide (TP) and import machinery during protein import into Arabidopsis (Arabidopsis thaliana) chloroplasts, compared with normal GFP. sfGFP and esGFP were efficiently imported into chloroplasts by a mutant TP with an alanine substitution in the N-terminal MLM motif, whereas the same mutant TP showed a defect in importing normal GFP into chloroplasts. Moreover, sfGFP and esGFP were efficiently imported into plastid protein import 2 (ppi2) and heat shock protein 93-V (hsp93-V) plants, which have mutations in atToc159 and Hsp93-V, respectively. In contrast, the presequence-mediated mitochondrial import of sfGFP and esGFP was severely impaired. Based on these results, we propose that the chloroplast import machinery is more tolerant to different folding states of preproteins, whereas the mitochondrial machinery is more specialized in the translocation of unfolded preproteins.
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Affiliation(s)
- Jinseung Jeong
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju 61186, South Korea
| | - Byeongho Moon
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, South Korea
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18
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Chloroplasts Protein Quality Control and Turnover: A Multitude of Mechanisms. Int J Mol Sci 2022; 23:ijms23147760. [PMID: 35887108 PMCID: PMC9319218 DOI: 10.3390/ijms23147760] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 07/11/2022] [Accepted: 07/12/2022] [Indexed: 11/16/2022] Open
Abstract
As the organelle of photosynthesis and other important metabolic pathways, chloroplasts contain up to 70% of leaf proteins with uniquely complex processes in synthesis, import, assembly, and turnover. Maintaining functional protein homeostasis in chloroplasts is vitally important for the fitness and survival of plants. Research over the past several decades has revealed a multitude of mechanisms that play important roles in chloroplast protein quality control and turnover under normal and stress conditions. These mechanisms include: (i) endosymbiotically-derived proteases and associated proteins that play a vital role in maintaining protein homeostasis inside the chloroplasts, (ii) the ubiquitin-dependent turnover of unimported chloroplast precursor proteins to prevent their accumulation in the cytosol, (iii) chloroplast-associated degradation of the chloroplast outer-membrane translocon proteins for the regulation of chloroplast protein import, (iv) chloroplast unfolded protein response triggered by accumulated unfolded and misfolded proteins inside the chloroplasts, and (v) vesicle-mediated degradation of chloroplast components in the vacuole. Here, we provide a comprehensive review of these diverse mechanisms of chloroplast protein quality control and turnover and discuss important questions that remain to be addressed in order to better understand and improve important chloroplast functions.
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19
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New Insights into the Chloroplast Outer Membrane Proteome and Associated Targeting Pathways. Int J Mol Sci 2022; 23:ijms23031571. [PMID: 35163495 PMCID: PMC8836251 DOI: 10.3390/ijms23031571] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 01/24/2022] [Accepted: 01/27/2022] [Indexed: 12/04/2022] Open
Abstract
Plastids are a dynamic class of organelle in plant cells that arose from an ancient cyanobacterial endosymbiont. Over the course of evolution, most genes encoding plastid proteins were transferred to the nuclear genome. In parallel, eukaryotic cells evolved a series of targeting pathways and complex proteinaceous machinery at the plastid surface to direct these proteins back to their target organelle. Chloroplasts are the most well-characterized plastids, responsible for photosynthesis and other important metabolic functions. The biogenesis and function of chloroplasts rely heavily on the fidelity of intracellular protein trafficking pathways. Therefore, understanding these pathways and their regulation is essential. Furthermore, the chloroplast outer membrane proteome remains relatively uncharted territory in our understanding of protein targeting. Many key players in the cytosol, receptors at the organelle surface, and insertases that facilitate insertion into the chloroplast outer membrane remain elusive for this group of proteins. In this review, we summarize recent advances in the understanding of well-characterized chloroplast outer membrane protein targeting pathways as well as provide new insights into novel targeting signals and pathways more recently identified using a bioinformatic approach. As a result of our analyses, we expand the known number of chloroplast outer membrane proteins from 117 to 138.
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20
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Hirosawa Y, Tada A, Matsuura T, Mori IC, Ogura Y, Hayashi T, Uehara S, Ito-Inaba Y, Inaba T. Salicylic Acid Acts Antagonistically to Plastid Retrograde Signaling by Promoting the Accumulation of Photosynthesis-associated Proteins in Arabidopsis. PLANT & CELL PHYSIOLOGY 2021; 62:1728-1744. [PMID: 34410430 DOI: 10.1093/pcp/pcab128] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 08/14/2021] [Accepted: 08/18/2021] [Indexed: 06/13/2023]
Abstract
Plastids are involved in phytohormone metabolism as well as photosynthesis. However, the mechanism by which plastid retrograde signals and phytohormones cooperatively regulate plastid biogenesis remains elusive. Here, we investigated the effects of an inhibitor and a mutation that generate biogenic plastid signals on phytohormones and vice versa. Inhibition of plastid biogenesis by norflurazon (NF) treatment and the plastid protein import2 (ppi2) mutation caused a decrease in salicylic acid (SA) and jasmonic acid (JA). This effect can be attributed in part to the altered expression of genes involved in the biosynthesis and the metabolism of SA and JA. However, SA-dependent induction of the PATHOGENESIS-RELATED1 gene was virtually unaffected in NF-treated plants and the ppi2 mutant. Instead, the level of chlorophyll in these plants was partially restored by the exogenous application of SA. Consistent with this observation, the levels of some photosynthesis-associated proteins increased in the ppi2 and NF-treated plants in response to SA treatment. This regulation in true leaves seems to occur at the posttranscriptional level since SA treatment did not induce the expression of photosynthesis-associated genes. In salicylic acid induction deficient 2 and lesions simulating disease resistance 1 mutants, endogenous SA regulates the accumulation of photosynthesis-associated proteins through transcriptional and posttranscriptional mechanisms. These data indicate that SA acts antagonistically to the inhibition of plastid biogenesis by promoting the accumulation of photosynthesis-associated proteins in Arabidopsis, suggesting a possible link between SA and biogenic plastid signaling.
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Affiliation(s)
- Yoshihiro Hirosawa
- Department of Agricultural and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, 1-1 Gakuenkibanadai-nishi, Miyazaki 889-2192, Japan
| | - Akari Tada
- Department of Agricultural and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, 1-1 Gakuenkibanadai-nishi, Miyazaki 889-2192, Japan
| | - Takakazu Matsuura
- Institute of Plant Science and Resources (IPSR), Okayama University, 2-20-1 Chuo, Kurashiki 710-0046, Japan
| | - Izumi C Mori
- Institute of Plant Science and Resources (IPSR), Okayama University, 2-20-1 Chuo, Kurashiki 710-0046, Japan
| | - Yoshitoshi Ogura
- Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
- Division of Microbiology, Department of Infectious Medicine, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan
| | - Tetsuya Hayashi
- Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Susumu Uehara
- Department of Agricultural and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, 1-1 Gakuenkibanadai-nishi, Miyazaki 889-2192, Japan
- Center for Gene Research, Nagoya University, Nagoya 464-8602, Japan
| | - Yasuko Ito-Inaba
- Department of Agricultural and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, 1-1 Gakuenkibanadai-nishi, Miyazaki 889-2192, Japan
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Takehito Inaba
- Department of Agricultural and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, 1-1 Gakuenkibanadai-nishi, Miyazaki 889-2192, Japan
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21
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Watson SJ, Li N, Ye Y, Wu F, Ling Q, Jarvis RP. Crosstalk between the chloroplast protein import and SUMO systems revealed through genetic and molecular investigation in Arabidopsis. eLife 2021; 10:60960. [PMID: 34473053 PMCID: PMC8497055 DOI: 10.7554/elife.60960] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Accepted: 09/01/2021] [Indexed: 11/19/2022] Open
Abstract
The chloroplast proteome contains thousands of different proteins that are encoded by the nuclear genome. These proteins are imported into the chloroplast via the action of the TOC translocase and associated downstream systems. Our recent work has revealed that the stability of the TOC complex is dynamically regulated by the ubiquitin-dependent chloroplast-associated protein degradation pathway. Here, we demonstrate that the TOC complex is also regulated by the small ubiquitin-like modifier (SUMO) system. Arabidopsis mutants representing almost the entire SUMO conjugation pathway can partially suppress the phenotype of ppi1, a pale-yellow mutant lacking the Toc33 protein. This suppression is linked to increased abundance of TOC proteins and improvements in chloroplast development. Moreover, data from molecular and biochemical experiments support a model in which the SUMO system directly regulates TOC protein stability. Thus, we have identified a regulatory link between the SUMO system and the chloroplast protein import machinery. All green plants grow by converting light energy into chemical energy. They do this using a process called photosynthesis, which happens inside compartments in plant cells called chloroplasts. Chloroplasts use thousands of different proteins to make chemical energy. Some of these proteins allow the chloroplasts to absorb light energy using chlorophyll, the pigment that makes leaves green. The vast majority of these proteins are transported into the chloroplasts through a protein machine called the TOC complex. When plants lack parts of the TOC complex, their chloroplasts develop abnormally, and their leaves turn yellow. Photosynthesis can make toxic by-products, so cells need a way to turn it off when they are under stress; for example, by lowering the number of TOC complexes on the chloroplasts. This is achieved by tagging TOC complexes with a molecule called ubiquitin, which will lead to their removal from chloroplasts, slowing photosynthesis down. It is unknown whether another, similar, molecular tag called SUMO aids in this destruction process. To find out, Watson et al. examined a mutant of the plant Arabidopsis thaliana. This mutant had low levels of the TOC complex, turning its leaves pale yellow. A combination of genetic, molecular, and biochemical experiments showed that SUMO molecular tags control the levels of TOC complex on chloroplasts. Increasing the amount of SUMO in the mutant plants made their leaves turn yellower, while interfering with the genes responsible for depositing SUMO tags turned the leaves green. This implies that in plants with less SUMO tags, cells stopped destroying their TOC complexes, allowing the chloroplasts to develop better, and changing the colour of the leaves. The SUMO tagging of TOC complexes shares a lot of genetic similarities with the ubiquitin tag system. It is possible that SUMO tags may help to control the CHLORAD pathway, which destroys TOC complexes marked with ubiquitin. Understanding this relationship, and how to influence it, could help to improve the performance of crops. The next step is to understand exactly how SUMO tags promote the destruction of the TOC complex.
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Affiliation(s)
| | - Na Li
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
| | - Yiting Ye
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Feijie Wu
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.,Department of Biology, University of Leicester, Leicester, United Kingdom
| | - Qihua Ling
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom.,National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.,Department of Biology, University of Leicester, Leicester, United Kingdom
| | - R Paul Jarvis
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom.,Department of Biology, University of Leicester, Leicester, United Kingdom
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22
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Liu XJ, Sun J, Huang Y, Li C, Zheng P, Yuan Y, Chen H, Jan M, Zheng H, Du H, Tu J. Osj10gBTF3-Mediated Import of Chloroplast Protein Is Essential for Pollen Development in Rice. FRONTIERS IN PLANT SCIENCE 2021; 12:713544. [PMID: 34421965 PMCID: PMC8377413 DOI: 10.3389/fpls.2021.713544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Accepted: 07/13/2021] [Indexed: 06/13/2023]
Abstract
Chloroplasts are crucial organelles for the generation of fatty acids and starch required for plant development. Nascent polypeptide-associated complex (NAC) proteins have been implicated in development as transcription factors. However, their chaperone roles in chloroplasts and their relationship with pollen development in plants remain to be elucidated. Here, we demonstrated that Osj10gBTF3, a NAC protein, regulates pollen and chloroplast development in rice by coordinating with a Hsp90 family chaperone OsHSP82 to mediate chloroplast import. Knockout of Osj10gBTF3 affects pollen and chloroplast development and significantly reduces the accumulation of fertility-related chloroplast protein OsPPR676. Both Osj10gBTF3 and OsHSP82 interact with OsPPR676. Interestingly, the interaction between OsHSP82 and OsPPR676 is only found in the cytoplasm, while the interaction between Osj10gBTF3 and OsPPR676 also occurs inside the chloroplast. The chloroplast stroma chaperone OsCpn60 can also be co-precipitated with Osj10gBTF3, but not with OsHSP82. Further investigation indicates that Osj10gBTF3 enters the chloroplast stroma possibly through the inner chloroplast membrane channel protein Tic110 and then recruits OsCpn60 for the folding or assembly of OsPPR676. Our results reveal a chaperone role of Osj10gBTF3 in chloroplast import different from Hsp90 and provide a link between chloroplast transport and pollen development in rice.
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Affiliation(s)
- Xue-jiao Liu
- Institute of Crop Science, Zhejiang University, Hangzhou, China
| | - Jiaqi Sun
- Department of Biology, McGill University, Montreal, QC, Canada
| | - Yuqing Huang
- Institute of Crop Science, Zhejiang University, Hangzhou, China
| | - Chao Li
- Institute of Crop Science, Zhejiang University, Hangzhou, China
| | - Peng Zheng
- Institute of Crop Science, Zhejiang University, Hangzhou, China
| | - Yue Yuan
- Institute of Crop Science, Zhejiang University, Hangzhou, China
| | - Hao Chen
- Institute of Crop Science, Zhejiang University, Hangzhou, China
| | - Mehmood Jan
- Institute of Crop Science, Zhejiang University, Hangzhou, China
| | - Huanquan Zheng
- Department of Biology, McGill University, Montreal, QC, Canada
| | - Hao Du
- Institute of Crop Science, Zhejiang University, Hangzhou, China
- Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, China
| | - Jumin Tu
- Institute of Crop Science, Zhejiang University, Hangzhou, China
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23
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Li M, Ruwe H, Melzer M, Junker A, Hensel G, Tschiersch H, Schwenkert S, Chamas S, Schmitz-Linneweber C, Börner T, Stein N. The Arabidopsis AAC Proteins CIL and CIA2 Are Sub-functionalized Paralogs Involved in Chloroplast Development. FRONTIERS IN PLANT SCIENCE 2021; 12:681375. [PMID: 34163512 PMCID: PMC8215611 DOI: 10.3389/fpls.2021.681375] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 05/06/2021] [Indexed: 05/22/2023]
Abstract
The Arabidopsis gene Chloroplast Import Apparatus 2 (CIA2) encodes a transcription factor that positively affects the activity of nuclear genes for chloroplast ribosomal proteins and chloroplast protein import machineries. CIA2-like (CIL) is the paralogous gene of CIA2. We generated a cil mutant by site-directed mutagenesis and compared it with cia2 and cia2cil double mutant. Phenotype of the cil mutant did not differ from the wild type under our growth conditions, except faster growth and earlier time to flowering. Compared to cia2, the cia2cil mutant showed more impaired chloroplast functions and reduced amounts of plastid ribosomal RNAs. In silico analyses predict for CIA2 and CIL a C-terminal CCT domain and an N-terminal chloroplast transit peptide (cTP). Chloroplast (and potentially nuclear) localization was previously shown for HvCMF3 and HvCMF7, the homologs of CIA2 and CIL in barley. We observed nuclear localization of CIL after transient expression in Arabidopsis protoplasts. Surprisingly, transformation of cia2 with HvCMF3, HvCMF7, or with a truncated CIA2 lacking the predicted cTP could partially rescue the pale-green phenotype of cia2. These data are discussed with respect to potentially overlapping functions between CIA2, CIL, and their barley homologs and to the function of the putative cTPs of CIA2 and CIL.
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Affiliation(s)
- Mingjiu Li
- Genomics of Genetic Resources, Department of Genebank, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany
| | - Hannes Ruwe
- Molecular Genetics, Institute of Biology, Humboldt University, Rhoda Erdmann Haus, Berlin, Germany
| | - Michael Melzer
- Structural Cell Biology, Department of Physiology and Cell Biology, IPK, Gatersleben, Germany
| | - Astrid Junker
- Acclimation Dynamics and Phenotyping, Department of Molecular Genetics, IPK, Gatersleben, Germany
| | - Goetz Hensel
- Plant Reproductive Biology, Department of Physiology and Cell Biology, IPK, Gatersleben, Germany
| | - Henning Tschiersch
- Acclimation Dynamics and Phenotyping, Department of Molecular Genetics, IPK, Gatersleben, Germany
| | - Serena Schwenkert
- Department of Biology I, Ludwig-Maximilians University of Munich, Munich, Germany
| | - Sindy Chamas
- Plant Reproductive Biology, Department of Physiology and Cell Biology, IPK, Gatersleben, Germany
| | | | - Thomas Börner
- Molecular Genetics, Institute of Biology, Humboldt University, Rhoda Erdmann Haus, Berlin, Germany
| | - Nils Stein
- Genomics of Genetic Resources, Department of Genebank, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany
- Department of Crop Sciences, Center for Integrated Breeding Research (CiBreed), Georg-August-Universität Göttingen, Göttingen, Germany
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24
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PRAT Proteins Operate in Organellar Protein Import and Export in Arabidopsis thaliana. PLANTS 2021; 10:plants10050958. [PMID: 34064964 PMCID: PMC8151980 DOI: 10.3390/plants10050958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Revised: 04/25/2021] [Accepted: 04/29/2021] [Indexed: 11/17/2022]
Abstract
Chloroplasts need to import preproteins and amino acids from the cytosol during their light-induced differentiation. Similarly, chloroplasts have to export organic matter including proteins and amino acids during leaf senescence. Members of the PRAT (preprotein and amino acid transporter) family are candidate transporters for both processes. Here, we defined the role of two small PRAT gene families, At4g26670 and At5g55510 (HP20 subfamily) versus At3g49560 and At5g24650 (HP30 subfamily) during greening of etiolated plants and during leaf senescence. Using a combination of reverse genetics, protein biochemistry and physiological tools, evidence was obtained for a role of chloroplast HP20, HP30 and HP30-2 in protein, but not amino acid, import into chloroplasts. HP20, HP30 and HP30-2 form larger complexes involved in the uptake of transit sequence-less cytosolic precursors. In addition, we identified a fraction of HP30-2 in mitochondria where it served a similar function as found for chloroplasts and operated in the uptake of transit sequence-less cytosolic precursor proteins. By contrast, HP22 was found to act in the export of proteins from chloroplasts during leaf senescence, and thus its role is entirely different from that of its orthologue, HP20. HP22 is part of a unique protein complex in the envelope of senescing chloroplasts that comprises at least 11 proteins and contains with HP65b (At5g55220) a protein that is related to the bacterial trigger factor chaperone. An ortholog of HP65b exists in the cyanobacterium Synechocystis and has previously been implicated in protein secretion. Whereas plants depleted of either HP22 or HP65b or even both were increasingly delayed in leaf senescence and retained much longer stromal chloroplast constituents than wild-type plants, HP22 overexpressors showed premature leaf senescence that was associated with accelerated losses of stromal chloroplast proteins. Together, our results identify the PRAT protein family as a unique system for importing and exporting proteins from chloroplasts.
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25
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Afitlhile M, Worthington R, Baldric J. The toc132toc120 heterozygote mutant of Arabidopsis thaliana accumulates decreased levels of the major chloroplast lipids. PHYTOCHEMISTRY 2021; 184:112652. [PMID: 33535085 DOI: 10.1016/j.phytochem.2020.112652] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 12/28/2020] [Accepted: 12/29/2020] [Indexed: 06/12/2023]
Abstract
We used ESI-MS/MS to profile glycerolipids in a mutant of Arabidopsis thaliana that is null and heterozygous for the TOC132 and TOC120 genes, and is referred to as the toc132toc120± mutant. The goal was to assess the impact of a defective atToc132/120 receptor on the accumulation of chloroplast lipids. The mutant accumulated decreased amounts of monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) and phosphatidylglycerol (PG). In the cold-acclimated mutant, PG accumulated at the control levels. However, 34:4-PG (18:3/16:1Δ3trans) was significantly decreased, which indicates that the mutant was impaired in synthesis of the chloroplast-derived PG. Major molecular species of MGDG and DGDG were significantly decreased, which was indicative of the decreased levels of triunsaturated fatty acids in galactolipids. The cold-acclimated mutant accumulated increased levels of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS), which indicate that defect in the atToc132/120 receptor did not impair the ER pathway of lipid synthesis. Both cold-acclimated wildtype and mutant plants accumulated increased levels of phosphatidic acid (PA). The increased levels of major molecular species of PA suggest that some pool of PA was derived from degradation of both the chloroplast and extra-chloroplast lipids. The cold-acclimated mutant had decreased double bond index (DBI) and increased acyl chain length (ACL), which was indicative of decreased membrane fluidity. However, a decrease in the ratio of MGDG to DGDG indicate that the mutant was capable of remodeling membrane lipids in response to low temperatures. We conclude that the defective Toc132/120 receptor resulted in decreased synthesis of chloroplast lipids and decreased membrane fluidity.
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Affiliation(s)
- Meshack Afitlhile
- Department of Biological Sciences, Western Illinois University, Waggoner Hall 311, 1 University Circle, Macomb, IL, 61455, USA.
| | - Rebecca Worthington
- Department of Biological Sciences, Western Illinois University, Waggoner Hall 311, 1 University Circle, Macomb, IL, 61455, USA
| | - Jeashelle Baldric
- Department of Biological Sciences, Western Illinois University, Waggoner Hall 311, 1 University Circle, Macomb, IL, 61455, USA
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26
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Pipitone R, Eicke S, Pfister B, Glauser G, Falconet D, Uwizeye C, Pralon T, Zeeman SC, Kessler F, Demarsy E. A multifaceted analysis reveals two distinct phases of chloroplast biogenesis during de-etiolation in Arabidopsis. eLife 2021; 10:e62709. [PMID: 33629953 PMCID: PMC7906606 DOI: 10.7554/elife.62709] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 02/04/2021] [Indexed: 11/18/2022] Open
Abstract
Light triggers chloroplast differentiation whereby the etioplast transforms into a photosynthesizing chloroplast and the thylakoid rapidly emerges. However, the sequence of events during chloroplast differentiation remains poorly understood. Using Serial Block Face Scanning Electron Microscopy (SBF-SEM), we generated a series of chloroplast 3D reconstructions during differentiation, revealing chloroplast number and volume and the extent of envelope and thylakoid membrane surfaces. Furthermore, we used quantitative lipid and whole proteome data to complement the (ultra)structural data, providing a time-resolved, multi-dimensional description of chloroplast differentiation. This showed two distinct phases of chloroplast biogenesis: an initial photosynthesis-enabling 'Structure Establishment Phase' followed by a 'Chloroplast Proliferation Phase' during cell expansion. Moreover, these data detail thylakoid membrane expansion during de-etiolation at the seedling level and the relative contribution and differential regulation of proteins and lipids at each developmental stage. Altogether, we establish a roadmap for chloroplast differentiation, a critical process for plant photoautotrophic growth and survival.
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Affiliation(s)
- Rosa Pipitone
- Plant Physiology Laboratory, University of NeuchâtelNeuchâtelSwitzerland
| | - Simona Eicke
- Institute of Molecular Plant Biology, Department of Biology, ETH ZurichZurichSwitzerland
| | - Barbara Pfister
- Institute of Molecular Plant Biology, Department of Biology, ETH ZurichZurichSwitzerland
| | - Gaetan Glauser
- Neuchâtel Platform of Analytical Chemistry, University of NeuchâtelNeuchâtelSwitzerland
| | - Denis Falconet
- Université Grenoble Alpes, CNRS, CEA, INRAE, IRIG-DBSCI-LPCVGrenobleFrance
| | - Clarisse Uwizeye
- Université Grenoble Alpes, CNRS, CEA, INRAE, IRIG-DBSCI-LPCVGrenobleFrance
| | - Thibaut Pralon
- Plant Physiology Laboratory, University of NeuchâtelNeuchâtelSwitzerland
| | - Samuel C Zeeman
- Institute of Molecular Plant Biology, Department of Biology, ETH ZurichZurichSwitzerland
| | - Felix Kessler
- Plant Physiology Laboratory, University of NeuchâtelNeuchâtelSwitzerland
| | - Emilie Demarsy
- Plant Physiology Laboratory, University of NeuchâtelNeuchâtelSwitzerland
- Department of Botany and Plant Biology, University of GenevaGenevaSwitzerland
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27
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Afitlhile M, Worthington R, Heda G, Brown L. The TOC159 null mutant of Arabidopsis thaliana is impaired in the accumulation of plastid lipids and phosphatidylcholine. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2021; 159:148-159. [PMID: 33360238 DOI: 10.1016/j.plaphy.2020.12.011] [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: 09/06/2020] [Accepted: 12/10/2020] [Indexed: 06/12/2023]
Abstract
We used electrospray ionization tandem mass spectrometry to profile glycerolipids in the TOC159 null mutant of Arabidopsis, which is referred to as plastid protein import 2, or ppi2. The goal was to evaluate the impact of a defective atToc159 receptor in the accumulation of plastid lipids. The ppi2 mutant is severely impaired in the accumulation of monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) and phosphatidylglycerol (PG), which are major components of the thylakoid membranes. Major molecular species of MGDG and DGDG are drastically decreased, which is consistent with our previous findings of decreased levels of hexadecatrienoic and linolenic acids. Under normal growth conditions, the ppi2 mutant accumulated significantly lower levels of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylinositol (PI). In the cold-acclimated mutant, the amounts of PE and PI were similar to the wildtype level, which indicates that the ER pathway of lipid synthesis was functional in the mutant. The cold-acclimated ppi2 mutant accumulated increased amounts of phosphatidic acid (PA), which was mirrored by an increase in phospholipase Dα (PLDα) transcript levels. These data suggest that PLDα activity contributed to the accumulation of cold-induced PA in the ppi2 mutant. The accumulation of major molecular species in PA indicates that cold-induced PA originated from the degradation of both plastidial and extraplastidial lipids. Compared with the wildtype, the ppi2 mutant had a low double bond index and high acyl chain length, which is indicative of decreased membrane fluidity. Taken together, these data indicate that a defective atToc159 receptor severely impaired the plastid pathway of lipid synthesis, which negatively affected the synthesis and/or accumulation of PC.
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Affiliation(s)
- Meshack Afitlhile
- Department of Biological Sciences, Western Illinois University, Waggoner Hall 311, 1 University Circle, Macomb, IL, 61455, USA.
| | - Rebecca Worthington
- Department of Biological Sciences, Western Illinois University, Waggoner Hall 311, 1 University Circle, Macomb, IL, 61455, USA
| | - Ghanshyam Heda
- Department of Sciences and Mathematics, Mississippi University for Women, 1100 College Street, Columbus, MS, 39701, USA
| | - Logan Brown
- Department of Biological Sciences, Western Illinois University, Waggoner Hall 311, 1 University Circle, Macomb, IL, 61455, USA
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28
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Afitlhile M, Worthington R, Banigan E, Jirik J, Hildebrand D. Ozone-induced lipid changes in the wildtype and toc132toc120 heterozygote mutant of Arabidopsis thaliana. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2021; 158:13-20. [PMID: 33291051 DOI: 10.1016/j.plaphy.2020.11.050] [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: 08/09/2020] [Accepted: 11/27/2020] [Indexed: 06/12/2023]
Abstract
We measured the fatty acids and lipid content in the wildtype and toc132toc120 heterozygote mutant of Arabidopsis thaliana that were exposed to elevated levels of ozone. The goal was to assess whether a defective atToc132/120 receptor would alter the mutant's response to ozone-induced stress. Increased malondialdehyde (MDA) levels were measured in wildtype plants that were exposed to ozone for 3 h and left in an ozone-free environment for 21 h. The increased levels of MDA were not positively correlated with changes in the levels of triunsaturated fatty acids from which MDA is derived. In both the wildtype and mutant plants, absolute amounts of the glycerolipids were not altered by ozone treatment. The untreated mutant, however, accumulated decreased levels of chloroplast lipids and triunsaturated fatty acids. In ozone-treated wildtype, the levels of 16:3 were significantly decreased and this was mirrored by decreased levels of TOC132 and FAD5 transcripts, and increased levels of SP1 E3 ligase transcripts. These data suggest a possible increase in protein ubiquitination under ozone-induced stress. In contrast, in ozone-treated mutant, the FAD5 transcripts accumulated at the control level. The untreated mutant, however, accumulated significantly increased levels of CAT1 and FAD7 transcripts, which indicates that a defective chloroplast receptor induced cellular stress. In ozone-treated wildtype, there was a small increase in 34:6-phosphatidic acid, which indicates that a small amount of the chloroplast-derived MGDG was degraded in response to ozone-induced stress. Overall, these data indicate that the wildtype and mutant responded differently in lipid composition and oxidation to ozone-induced stress.
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Affiliation(s)
- Meshack Afitlhile
- Western Illinois University, Department of Biological Sciences, 1 University Circle, Waggoner Hall 311 Macomb, IL, 61455, USA.
| | - Rebecca Worthington
- Western Illinois University, Department of Biological Sciences, 1 University Circle, Waggoner Hall 311 Macomb, IL, 61455, USA
| | - Emily Banigan
- Western Illinois University, Department of Biological Sciences, 1 University Circle, Waggoner Hall 311 Macomb, IL, 61455, USA
| | - Jessica Jirik
- Western Illinois University, Department of Biological Sciences, 1 University Circle, Waggoner Hall 311 Macomb, IL, 61455, USA
| | - David Hildebrand
- University of Kentucky, Department of Plant Sciences, 1405 Veterans Drive, Office 403 PSB, Lexington, KY, 40546, USA
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29
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Accossato S, Kessler F, Shanmugabalaji V. SUMOylation contributes to proteostasis of the chloroplast protein import receptor TOC159 during early development. eLife 2020; 9:60968. [PMID: 33350382 PMCID: PMC8497054 DOI: 10.7554/elife.60968] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Accepted: 12/22/2020] [Indexed: 01/30/2023] Open
Abstract
Chloroplast biogenesis describes the transition of non-photosynthetic proplastids to photosynthetically active chloroplasts in the cells of germinating seeds. Chloroplast biogenesis requires the import of thousands of nuclear-encoded preproteins by essential import receptor TOC159. We demonstrate that the small ubiquitin-related modifier (SUMO) pathway crosstalks with the ubiquitin-proteasome pathway to affect TOC159 stability during early plant development. We identified a SUMO3-interacting motif (SIM) in the TOC159 GTPase domain and a SUMO3 covalent SUMOylation site in the membrane domain. A single K to R substitution (K1370R) in the M-domain disables SUMOylation. Compared to wild-type TOC159, TOC159K1370R was destabilized under UPS-inducing stress conditions. However, TOC159K1370R recovered to same protein level as wild-type TOC159 in the presence of a proteasome inhibitor. Thus, SUMOylation partially stabilizes TOC159 against UPS-dependent degradation under stress conditions. Our data contribute to the evolving model of tightly controlled proteostasis of the TOC159 import receptor during proplastid to chloroplast transition.
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Affiliation(s)
- Sonia Accossato
- Laboratory of Plant Physiology, University of Neuchâtel, Neuchâtel, Switzerland
| | - Felix Kessler
- Laboratory of Plant Physiology, University of Neuchâtel, Neuchâtel, Switzerland
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30
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Ramundo S, Asakura Y, Salomé PA, Strenkert D, Boone M, Mackinder LCM, Takafuji K, Dinc E, Rahire M, Crèvecoeur M, Magneschi L, Schaad O, Hippler M, Jonikas MC, Merchant S, Nakai M, Rochaix JD, Walter P. Coexpressed subunits of dual genetic origin define a conserved supercomplex mediating essential protein import into chloroplasts. Proc Natl Acad Sci U S A 2020; 117:32739-32749. [PMID: 33273113 PMCID: PMC7768757 DOI: 10.1073/pnas.2014294117] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In photosynthetic eukaryotes, thousands of proteins are translated in the cytosol and imported into the chloroplast through the concerted action of two translocons-termed TOC and TIC-located in the outer and inner membranes of the chloroplast envelope, respectively. The degree to which the molecular composition of the TOC and TIC complexes is conserved over phylogenetic distances has remained controversial. Here, we combine transcriptomic, biochemical, and genetic tools in the green alga Chlamydomonas (Chlamydomonas reinhardtii) to demonstrate that, despite a lack of evident sequence conservation for some of its components, the algal TIC complex mirrors the molecular composition of a TIC complex from Arabidopsis thaliana. The Chlamydomonas TIC complex contains three nuclear-encoded subunits, Tic20, Tic56, and Tic100, and one chloroplast-encoded subunit, Tic214, and interacts with the TOC complex, as well as with several uncharacterized proteins to form a stable supercomplex (TIC-TOC), indicating that protein import across both envelope membranes is mechanistically coupled. Expression of the nuclear and chloroplast genes encoding both known and uncharacterized TIC-TOC components is highly coordinated, suggesting that a mechanism for regulating its biogenesis across compartmental boundaries must exist. Conditional repression of Tic214, the only chloroplast-encoded subunit in the TIC-TOC complex, impairs the import of chloroplast proteins with essential roles in chloroplast ribosome biogenesis and protein folding and induces a pleiotropic stress response, including several proteins involved in the chloroplast unfolded protein response. These findings underscore the functional importance of the TIC-TOC supercomplex in maintaining chloroplast proteostasis.
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Affiliation(s)
- Silvia Ramundo
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143
- Howard Hughes Medical Institute, Chevy Chase, MD 20815
| | - Yukari Asakura
- Laboratory of Organelle Biology, Institute for Protein Research, Osaka University, Osaka 565-0871, Japan
| | - Patrice A Salomé
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095
| | - Daniela Strenkert
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095
| | - Morgane Boone
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143
- Howard Hughes Medical Institute, Chevy Chase, MD 20815
| | - Luke C M Mackinder
- Department of Biology, University of York, York YO10 5DD, United Kingdom
| | - Kazuaki Takafuji
- Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Emine Dinc
- Department of Molecular Biology, University of Geneva, Geneva CH-1211, Switzerland
- Department of Plant Biology, University of Geneva, Geneva CH-1211, Switzerland
| | - Michèle Rahire
- Department of Molecular Biology, University of Geneva, Geneva CH-1211, Switzerland
- Department of Plant Biology, University of Geneva, Geneva CH-1211, Switzerland
| | - Michèle Crèvecoeur
- Department of Molecular Biology, University of Geneva, Geneva CH-1211, Switzerland
- Department of Plant Biology, University of Geneva, Geneva CH-1211, Switzerland
| | - Leonardo Magneschi
- Institute of Plant Biology and Biotechnology, University of Münster, Münster 48143, Germany
| | - Olivier Schaad
- Department of Biochemistry, University of Geneva, Geneva CH-1211, Switzerland
| | - Michael Hippler
- Institute of Plant Biology and Biotechnology, University of Münster, Münster 48143, Germany
- Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan
| | - Martin C Jonikas
- Department of Molecular Biology, Princeton University, Princeton, NJ 08540
- Howard Hughes Medical Institute, Chevy Chase, MD 20815
| | - Sabeeha Merchant
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095
| | - Masato Nakai
- Laboratory of Organelle Biology, Institute for Protein Research, Osaka University, Osaka 565-0871, Japan;
| | - Jean-David Rochaix
- Department of Molecular Biology, University of Geneva, Geneva CH-1211, Switzerland;
- Department of Plant Biology, University of Geneva, Geneva CH-1211, Switzerland
| | - Peter Walter
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143;
- Howard Hughes Medical Institute, Chevy Chase, MD 20815
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31
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Hertle AP, García-Cerdán JG, Armbruster U, Shih R, Lee JJ, Wong W, Niyogi KK. A Sec14 domain protein is required for photoautotrophic growth and chloroplast vesicle formation in Arabidopsis thaliana. Proc Natl Acad Sci U S A 2020; 117:9101-9111. [PMID: 32245810 PMCID: PMC7183190 DOI: 10.1073/pnas.1916946117] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
In eukaryotic photosynthetic organisms, the conversion of solar into chemical energy occurs in thylakoid membranes in the chloroplast. How thylakoid membranes are formed and maintained is poorly understood. However, previous observations of vesicles adjacent to the stromal side of the inner envelope membrane of the chloroplast suggest a possible role of membrane transport via vesicle trafficking from the inner envelope to the thylakoids. Here we show that the model plant Arabidopsis thaliana has a chloroplast-localized Sec14-like protein (CPSFL1) that is necessary for photoautotrophic growth and vesicle formation at the inner envelope membrane of the chloroplast. The cpsfl1 mutants are seedling lethal, show a defect in thylakoid structure, and lack chloroplast vesicles. Sec14 domain proteins are found only in eukaryotes and have been well characterized in yeast, where they regulate vesicle budding at the trans-Golgi network. Like the yeast Sec14p, CPSFL1 binds phosphatidylinositol phosphates (PIPs) and phosphatidic acid (PA) and acts as a phosphatidylinositol transfer protein in vitro, and expression of Arabidopsis CPSFL1 can complement the yeast sec14 mutation. CPSFL1 can transfer PIP into PA-rich membrane bilayers in vitro, suggesting that CPSFL1 potentially facilitates vesicle formation by trafficking PA and/or PIP, known regulators of membrane trafficking between organellar subcompartments. These results underscore the role of vesicles in thylakoid biogenesis and/or maintenance. CPSFL1 appears to be an example of a eukaryotic cytosolic protein that has been coopted for a function in the chloroplast, an organelle derived from endosymbiosis of a cyanobacterium.
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Affiliation(s)
- Alexander P Hertle
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720;
| | - José G García-Cerdán
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102
- Howard Hughes Medical Institute, University of California, Berkeley, CA 94720
| | - Ute Armbruster
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102
| | - Robert Shih
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Jimmy J Lee
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102
| | - Winnie Wong
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Krishna K Niyogi
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720;
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102
- Howard Hughes Medical Institute, University of California, Berkeley, CA 94720
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32
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Richardson LGL, Schnell DJ. Origins, function, and regulation of the TOC-TIC general protein import machinery of plastids. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:1226-1238. [PMID: 31730153 PMCID: PMC7031061 DOI: 10.1093/jxb/erz517] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 11/14/2019] [Indexed: 05/11/2023]
Abstract
The evolution of chloroplasts from the original endosymbiont involved the transfer of thousands of genes from the ancestral bacterial genome to the host nucleus, thereby combining the two genetic systems to facilitate coordination of gene expression and achieve integration of host and organelle functions. A key element of successful endosymbiosis was the evolution of a unique protein import system to selectively and efficiently target nuclear-encoded proteins to their site of function within the chloroplast after synthesis in the cytoplasm. The chloroplast TOC-TIC (translocon at the outer chloroplast envelope-translocon at the inner chloroplast envelope) general protein import system is conserved across the plant kingdom, and is a system of hybrid origin, with core membrane transport components adapted from bacterial protein targeting systems, and additional components adapted from host genes to confer the specificity and directionality of import. In vascular plants, the TOC-TIC system has diversified to mediate the import of specific, functionally related classes of plastid proteins. This functional diversification occurred as the plastid family expanded to fulfill cell- and tissue-specific functions in terrestrial plants. In addition, there is growing evidence that direct regulation of TOC-TIC activities plays an essential role in the dynamic remodeling of the organelle proteome that is required to coordinate plastid biogenesis with developmental and physiological events.
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Affiliation(s)
- Lynn G L Richardson
- Department of Plant Biology, Michigan State University, East Lansing, MI, USA
| | - Danny J Schnell
- Department of Plant Biology, Michigan State University, East Lansing, MI, USA
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33
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Khan A, Asaf S, Khan AL, Shehzad T, Al-Rawahi A, Al-Harrasi A. Comparative Chloroplast Genomics of Endangered Euphorbia Species: Insights into Hotspot Divergence, Repetitive Sequence Variation, and Phylogeny. PLANTS 2020; 9:plants9020199. [PMID: 32033491 PMCID: PMC7076480 DOI: 10.3390/plants9020199] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 01/16/2020] [Accepted: 01/17/2020] [Indexed: 11/30/2022]
Abstract
Euphorbia is one of the largest genera in the Euphorbiaceae family, comprising 2000 species possessing commercial, medicinal, and ornamental importance. However, there are very little data available on their molecular phylogeny and genomics, and uncertainties still exist at a taxonomic level. Herein, we sequence the complete chloroplast (cp) genomes of two species, E. larica and E. smithii, of the genus Euphorbia through next-generation sequencing and perform a comparative analysis with nine related genomes in the family. The results revealed that the cp genomes had similar quadripartite structure, gene content, and genome organization with previously reported genomes from the same family. The size of cp genomes ranged from 162,172 to 162,358 bp with 132 and 133 genes, 8 rRNAs, 39 tRNA in E. smithii and E. larica, respectively. The numbers of protein-coding genes were 85 and 86, with each containing 19 introns. The four-junction regions were studied and results reveal that rps19 was present at JLB (large single copy region and inverted repeat b junction) in E. larica where its complete presence was located in the IRb (inverted repeat b) region in E. smithii. The sequence comparison revealed that highly divergent regions in rpoC1, rpocB, ycf3, clpP, petD, ycf1, and ndhF of the cp genomes might provide better understanding of phylogenetic inferences in the Euphorbiaceae and order Malpighiales. Phylogenetic analyses of this study illustrate sister clades of E. smithii with E. tricullii and these species form a monophyletic clade with E. larica. The current study might help us to understand the genome architecture, genetic diversity among populations, and evolutionary depiction in the genera.
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Affiliation(s)
- Arif Khan
- Natural and Medical Sciences Research Center, University of Nizwa, Nizwa 616, Oman; (A.K.); (S.A.); (A.A.-R.)
- Genomics Group, Faculty of Biosciences and Aquaculture, Nord University, 8049 Bodø, Norway
| | - Sajjad Asaf
- Natural and Medical Sciences Research Center, University of Nizwa, Nizwa 616, Oman; (A.K.); (S.A.); (A.A.-R.)
| | - Abdul Latif Khan
- Natural and Medical Sciences Research Center, University of Nizwa, Nizwa 616, Oman; (A.K.); (S.A.); (A.A.-R.)
- Correspondence: (A.L.K.); (A.A.-H.)
| | - Tariq Shehzad
- Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, 2713 Doha, Qatar;
| | - Ahmed Al-Rawahi
- Natural and Medical Sciences Research Center, University of Nizwa, Nizwa 616, Oman; (A.K.); (S.A.); (A.A.-R.)
| | - Ahmed Al-Harrasi
- Natural and Medical Sciences Research Center, University of Nizwa, Nizwa 616, Oman; (A.K.); (S.A.); (A.A.-R.)
- Correspondence: (A.L.K.); (A.A.-H.)
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Schnell DJ. The TOC GTPase Receptors: Regulators of the Fidelity, Specificity and Substrate Profiles of the General Protein Import Machinery of Chloroplasts. Protein J 2020; 38:343-350. [PMID: 31201619 PMCID: PMC6589150 DOI: 10.1007/s10930-019-09846-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
More than 2500 nuclear encoded preproteins are required for the function of chloroplasts in terrestrial plants. These preproteins are imported into chloroplasts via the concerted action of two multi-subunit translocons of the outer (TOC) and inner (TIC) membranes of the chloroplast envelope. This general import machinery functions to recognize and import proteins with high fidelity and efficiency to ensure that organelle biogenesis is properly coordinated with developmental and physiological events. Two components of the TOC machinery, Toc34 and Toc159, act as the primary receptors for preproteins at the chloroplast surface. They interact with the intrinsic targeting signals (transit peptides) of preproteins to mediate the selectivity of targeting, and they contribute to the quality control of import by constituting a GTP-dependent checkpoint in the import reaction. The TOC receptor family has expanded to regulate the import of distinct classes of preproteins that are required for remodeling of organelle proteomes during plastid-type transitions that accompany developmental changes. As such, the TOC receptors function as central regulators of the fidelity, specificity and selectivity of the general import machinery, thereby contributing to the integration of protein import with plastid biogenesis.
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Affiliation(s)
- Danny J Schnell
- Department of Plant Biology, Michigan State University, East Lansing, MI, USA.
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35
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Ling Q, Broad W, Trösch R, Töpel M, Demiral Sert T, Lymperopoulos P, Baldwin A, Jarvis RP. Ubiquitin-dependent chloroplast-associated protein degradation in plants. Science 2019; 363:363/6429/eaav4467. [PMID: 30792274 DOI: 10.1126/science.aav4467] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 01/15/2019] [Indexed: 12/11/2022]
Abstract
Chloroplasts contain thousands of nucleus-encoded proteins that are imported from the cytosol by translocases in the chloroplast envelope membranes. Proteolytic regulation of the translocases is critically important, but little is known about the underlying mechanisms. We applied forward genetics and proteomics in Arabidopsis to identify factors required for chloroplast outer envelope membrane (OEM) protein degradation. We identified SP2, an Omp85-type β-barrel channel of the OEM, and CDC48, a cytosolic AAA+ (ATPase associated with diverse cellular activities) chaperone. Both proteins acted in the same pathway as the ubiquitin E3 ligase SP1, which regulates OEM translocase components. SP2 and CDC48 cooperated to bring about retrotranslocation of ubiquitinated substrates from the OEM (fulfilling conductance and motor functions, respectively), enabling degradation of the substrates by the 26S proteasome in the cytosol. Such chloroplast-associated protein degradation (CHLORAD) is vital for organellar functions and plant development.
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Affiliation(s)
- Qihua Ling
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
| | - William Broad
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
| | - Raphael Trösch
- Department of Biology, University of Leicester, Leicester LE1 7RH, UK
| | - Mats Töpel
- Department of Biology, University of Leicester, Leicester LE1 7RH, UK
| | | | | | - Amy Baldwin
- Department of Biology, University of Leicester, Leicester LE1 7RH, UK
| | - R Paul Jarvis
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK. .,Department of Biology, University of Leicester, Leicester LE1 7RH, UK
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36
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Sadali NM, Sowden RG, Ling Q, Jarvis RP. Differentiation of chromoplasts and other plastids in plants. PLANT CELL REPORTS 2019; 38:803-818. [PMID: 31079194 PMCID: PMC6584231 DOI: 10.1007/s00299-019-02420-2] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 04/29/2019] [Indexed: 05/17/2023]
Abstract
Plant cells are characterized by a unique group of interconvertible organelles called plastids, which are descended from prokaryotic endosymbionts. The most studied plastid type is the chloroplast, which carries out the ancestral plastid function of photosynthesis. During the course of evolution, plastid activities were increasingly integrated with cellular metabolism and functions, and plant developmental processes, and this led to the creation of new types of non-photosynthetic plastids. These include the chromoplast, a carotenoid-rich organelle typically found in flowers and fruits. Here, we provide an introduction to non-photosynthetic plastids, and then review the structures and functions of chromoplasts in detail. The role of chromoplast differentiation in fruit ripening in particular is explored, and the factors that govern plastid development are examined, including hormonal regulation, gene expression, and plastid protein import. In the latter process, nucleus-encoded preproteins must pass through two successive protein translocons in the outer and inner envelope membranes of the plastid; these are known as TOC and TIC (translocon at the outer/inner chloroplast envelope), respectively. The discovery of SP1 (suppressor of ppi1 locus1), which encodes a RING-type ubiquitin E3 ligase localized in the plastid outer envelope membrane, revealed that plastid protein import is regulated through the selective targeting of TOC complexes for degradation by the ubiquitin-proteasome system. This suggests the possibility of engineering plastid protein import in novel crop improvement strategies.
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Affiliation(s)
- Najiah M Sadali
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
- Centre for Research in Biotechnology for Agriculture (CEBAR), University of Malaya, 50603, Kuala Lumpur, Malaysia
| | - Robert G Sowden
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | - Qihua Ling
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | - R Paul Jarvis
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK.
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Lee DW, Lee S, Lee J, Woo S, Razzak MA, Vitale A, Hwang I. Molecular Mechanism of the Specificity of Protein Import into Chloroplasts and Mitochondria in Plant Cells. MOLECULAR PLANT 2019; 12:951-966. [PMID: 30890495 DOI: 10.1016/j.molp.2019.03.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 02/19/2019] [Accepted: 03/10/2019] [Indexed: 05/04/2023]
Abstract
Plants possess both types of endosymbiotic organelles, chloroplasts and mitochondria. Transit peptides and presequences function as signal sequences for specific import into chloroplasts and mitochondria, respectively. However, how these highly similar signal sequences confer the protein import specificity remains elusive. Here, we show that mitochondrial- or chloroplast-specific import involves two distinct steps, specificity determination and translocation across envelopes, which are mediated by the N-terminal regions and functionally interchangeable C-terminal regions, respectively, of transit peptides and presequences. A domain harboring multiple-arginine and hydrophobic sequence motifs in the N-terminal regions of presequences was identified as the mitochondrial specificity factor. The presence of this domain and the absence of arginine residues in the N-terminal regions of otherwise common targeting signals confers specificity of protein import into mitochondria and chloroplasts, respectively. AtToc159, a chloroplast import receptor, also contributes to determining chloroplast import specificity. We propose that common ancestral sequences were functionalized into mitochondrial- and chloroplast-specific signal sequences by the presence and absence, respectively, of multiple-arginine and hydrophobic sequence motifs in the N-terminal region.
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Affiliation(s)
- Dong Wook Lee
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Sumin Lee
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Junho Lee
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Seungjin Woo
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Md Abdur Razzak
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Alessandro Vitale
- Istituto di Biologia e Biotecnologia Agraria, Consiglio Nazionale Delle Ricerche, Milano, Italy
| | - Inhwan Hwang
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 37673, Korea; Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, Korea.
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38
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Shanmugabalaji V, Kessler F. CHLORAD: Eradicating Translocon Components from the Outer Membrane of the Chloroplast. MOLECULAR PLANT 2019; 12:467-469. [PMID: 30890496 DOI: 10.1016/j.molp.2019.03.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Revised: 03/07/2019] [Accepted: 03/08/2019] [Indexed: 06/09/2023]
Affiliation(s)
| | - Felix Kessler
- Laboratory of Plant Physiology, University of Neuchatel, 2000 Neuchâtel, Switzerland.
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Reinbothe S, Bartsch S, Rossig C, Davis MY, Yuan S, Reinbothe C, Gray J. A Protochlorophyllide (Pchlide) a Oxygenase for Plant Viability. FRONTIERS IN PLANT SCIENCE 2019; 10:593. [PMID: 31156665 PMCID: PMC6530659 DOI: 10.3389/fpls.2019.00593] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 04/24/2019] [Indexed: 05/19/2023]
Abstract
Higher plants contain a small, 5-member family of Rieske non-heme oxygenases that comprise the inner plastid envelope protein TIC55, phaeophorbide a oxygenasee (PAO), chlorophyllide a oxygenase (CAO), choline monooxygenase, and a 52 kDa protein (PTC52) associated with the precursor NADPH:protochlorophyllide (Pchlide) oxidoreductase A (pPORA) A translocon (PTC). Some of these chloroplast proteins have documented roles in chlorophyll biosynthesis (CAO) and degradation (PAO and TIC55), whereas the function of PTC52 remains unresolved. Biochemical evidence provided here identifies PTC52 as Pchlide a oxygenase of the inner plastid envelope linking Pchlide b synthesis to pPORA import. Protochlorophyllide b is the preferred substrate of PORA and its lack no longer allows pPORA import. The Pchlide b-dependent import pathway of pPORA thus operates in etiolated seedlings and is switched off during greening. Using dexamethasone-induced RNA interference (RNAi) we tested if PTC52 is involved in controlling both, pPORA import and Pchlide homeostasis in planta. As shown here, RNAi plants deprived of PTC52 transcript and PTC52 protein were unable to import pPORA and died as a result of excess Pchlide a accumulation causing singlet oxygen formation during greening. In genetic studies, no homozygous ptc52 knock-out mutants could be obtained presumably as a result of embryo lethality, suggesting a role for PTC52 in the initial greening of plant embryos. Phylogenetic studies identified PTC52-like genes amongst unicellular photosynthetic bacteria and higher plants, suggesting that the biochemical function associated with PTC52 may have an ancient evolutionary origin. PTC52 also harbors conserved motifs with bacterial oxygenases such as the terminal oxygenase component of 3-ketosteroid 9-alpha-hydroxylase (KshA) from Rhodococcus rhodochrous. 3D-modeling of PTC52 structure permitted the prediction of amino acid residues that contribute to the substrate specificity of this enzyme. In vitro-mutagenesis was used to test the predicted PTC52 model and provide insights into the reaction mechanism of this Rieske non-heme oxygenase.
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Affiliation(s)
- Steffen Reinbothe
- Laboratoire de Génétique Moléculaire des Plantes and Biologie Environnementale et Systémique (BEeSy), Université Grenoble Alpes, Grenoble, France
- *Correspondence: Steffen Reinbothe, John Gray,
| | - Sandra Bartsch
- Laboratoire de Génétique Moléculaire des Plantes and Biologie Environnementale et Systémique (BEeSy), Université Grenoble Alpes, Grenoble, France
| | - Claudia Rossig
- Laboratoire de Génétique Moléculaire des Plantes and Biologie Environnementale et Systémique (BEeSy), Université Grenoble Alpes, Grenoble, France
| | | | - Shu Yuan
- College of Resources, Sichuan Agricultural University, Chengdu, China
| | - Christiane Reinbothe
- Laboratoire de Génétique Moléculaire des Plantes and Biologie Environnementale et Systémique (BEeSy), Université Grenoble Alpes, Grenoble, France
| | - John Gray
- Department of Biological Sciences, The University of Toledo, Toledo, OH, United States
- *Correspondence: Steffen Reinbothe, John Gray,
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40
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Bölter B. En route into chloroplasts: preproteins' way home. PHOTOSYNTHESIS RESEARCH 2018; 138:263-275. [PMID: 29943212 DOI: 10.1007/s11120-018-0542-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 06/20/2018] [Indexed: 06/08/2023]
Abstract
Chloroplasts are the characteristic endosymbiotic organelles of plant cells which during the course of evolution lost most of their genetic information to the nucleus. Thus, they critically depend on the host cell for allocation of nearly their complete protein supply. This includes gene expression, translation, protein targeting, and transport-all of which need to be tightly regulated and perfectly coordinated to accommodate the cells' needs. To this end, multiple signaling pathways have been implemented that interchange information between the different cellular compartments. One of the most complex and energy consuming processes is the translocation of chloroplast-destined proteins into their target organelle. It is a concerted effort from chaperones, receptor proteins, channels, and regulatory elements to ensure correct targeting, efficient transport, and subsequent folding. Although we have discovered and learned a lot about protein import into chloroplasts in the last decades, there are still many open questions and debates about the roles of individual proteins as well as the mechanistic details. In this review, I will summarize and discuss the published data with a focus on the translocation complex in the chloroplast inner envelope membrane.
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Affiliation(s)
- Bettina Bölter
- Department Biologie I, Botanik, Ludwig-Maximilians-Universität, Planegg-Martinsried, Germany.
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41
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Chu CC, Li HM. Developmental regulation of protein import into plastids. PHOTOSYNTHESIS RESEARCH 2018; 138:327-334. [PMID: 29943361 DOI: 10.1007/s11120-018-0546-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 06/20/2018] [Indexed: 06/08/2023]
Abstract
The plastid proteome changes according to developmental stages. Accruing evidence shows that, in addition to transcriptional and translational controls, preprotein import into plastids is also part of the process regulating plastid proteomes. Different preproteins have distinct preferences for plastids of different tissues. Preproteins are also divided into at least three age-selective groups based on their import preference for chloroplasts of different ages. Both tissue and age selectivity are determined by the transit peptide of each preprotein, and a transit-peptide motif for older-chloroplast preference has been identified. Future challenges lie in identifying other motifs for tissue and age selectivity, as well as in identifying the receptor components that decipher these motifs. Developmental regulation also suggests that caution should be exercised when comparing protein import data generated with plastids isolated from different tissues or with chloroplasts isolated from plants of different ages.
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Affiliation(s)
- Chiung-Chih Chu
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei, 11529, Taiwan
| | - Hsou-Min Li
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei, 11529, Taiwan.
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42
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Shanmugabalaji V, Chahtane H, Accossato S, Rahire M, Gouzerh G, Lopez-Molina L, Kessler F. Chloroplast Biogenesis Controlled by DELLA-TOC159 Interaction in Early Plant Development. Curr Biol 2018; 28:2616-2623.e5. [PMID: 30078560 DOI: 10.1016/j.cub.2018.06.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 04/23/2018] [Accepted: 06/06/2018] [Indexed: 11/28/2022]
Abstract
Chloroplast biogenesis, visible as greening, is the key to photoautotrophic growth in plants. At the organelle level, it requires the development of non-photosynthetic, color-less proplastids to photosynthetically active, green chloroplasts at early stages of plant development, i.e., in germinating seeds. This depends on the import of thousands of different preproteins into the developing organelle by the chloroplast protein import machinery [1]. The preprotein import receptor TOC159 is essential in the process, its mutation blocking chloroplast biogenesis and resulting in albino plants [2]. The molecular mechanisms controlling the onset of chloroplast biogenesis during germination are largely unknown. Germination depends on the plant hormone gibberellic acid (GA) and is repressed by DELLA when GA concentrations are low [3, 4]. Here, we show that DELLA negatively regulates TOC159 protein abundance under low GA. The direct DELLA-TOC159 interaction promotes TOC159 degradation by the ubiquitin/proteasome system (UPS). Moreover, the accumulation of photosynthesis-associated proteins destined for the chloroplast is downregulated posttranscriptionally. Analysis of a model import substrate indicates that it is targeted for removal by the UPS prior to import. Thus, under low GA, the UPS represses chloroplast biogenesis by a dual mechanism comprising the DELLA-dependent destruction of the import receptor TOC159, as well as that of its protein cargo. In conclusion, our data provide a molecular framework for the GA hormonal control of proplastid to chloroplast transition during early plant development.
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Affiliation(s)
| | - Hicham Chahtane
- Department of Plant Biology, University of Geneva, Geneva, Switzerland; Institute for Genetics and Genomics in Geneva (iGE3), University of Geneva, Geneva, Switzerland
| | - Sonia Accossato
- Laboratory of Plant Physiology, University of Neuchâtel, 2000 Neuchâtel, Switzerland
| | - Michèle Rahire
- Department of Plant Biology, University of Geneva, Geneva, Switzerland; Institute for Genetics and Genomics in Geneva (iGE3), University of Geneva, Geneva, Switzerland
| | - Guillaume Gouzerh
- Laboratory of Plant Physiology, University of Neuchâtel, 2000 Neuchâtel, Switzerland
| | - Luis Lopez-Molina
- Department of Plant Biology, University of Geneva, Geneva, Switzerland; Institute for Genetics and Genomics in Geneva (iGE3), University of Geneva, Geneva, Switzerland.
| | - Felix Kessler
- Laboratory of Plant Physiology, University of Neuchâtel, 2000 Neuchâtel, Switzerland.
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43
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Sandhu D, Coleman Z, Atkinson T, Rai KM, Mendu V. Genetics and Physiology of the Nuclearly Inherited Yellow Foliar Mutants in Soybean. FRONTIERS IN PLANT SCIENCE 2018; 9:471. [PMID: 29696030 PMCID: PMC5904354 DOI: 10.3389/fpls.2018.00471] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 03/26/2018] [Indexed: 05/27/2023]
Abstract
Plant photosynthetic pigments are important in harvesting the light energy and transfer of energy during photosynthesis. There are several yellow foliar mutants discovered in soybean and chromosomal locations for about half of them have been deduced. Viable-yellow mutants are capable of surviving with decreased photosynthesis, while lethal-yellow mutants die shortly after germination. In addition to the decreased chlorophyll content, other features associated with yellow mutants include altered Chl a and Chl b ratio, reduction in chloroplast size and number, lower levels of other photosynthetic pigments, inability of thylakoids to stack into granum, lack of lamellae to interconnect granum and reduced size of the light harvesting complex. For some yellow mutants, temperature and/or light play a critical role in the manifestation of phenotype. Although yellow foliar mutants are viewed as undesirable for crop production, there is the possibility of these mutants to create a positive impact by reducing the total amount of chlorophyll and diverting resources toward increased biochemical photosynthetic capacity leading to increased yield. Recent advances in model plants led to the isolation and characterization of various genes associated with yellow foliar phenotype. Knowledge gained from the model plants can be applied using homology based cloning approach to isolate genes in soybean and understanding the modes of actions of the involved proteins. Identifying and characterizing yellow foliar mutants will not only aid in understanding the biosynthetic pathways involved in the photosynthetic machinery, but may also provide ways to increase soybean productivity.
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Affiliation(s)
| | - Zachary Coleman
- Department of Biology, University of Wisconsin-Stevens Point, Stevens Point, WI, United States
| | - Taylor Atkinson
- Department of Biology, University of Wisconsin-Stevens Point, Stevens Point, WI, United States
| | - Krishan M. Rai
- Fiber and Biopolymer Research Institute, Department of Plant and Soil Science, Texas Tech University, Lubbock, TX, United States
| | - Venugopal Mendu
- Fiber and Biopolymer Research Institute, Department of Plant and Soil Science, Texas Tech University, Lubbock, TX, United States
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44
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Structural components involved in plastid protein import. Essays Biochem 2018; 62:65-75. [DOI: 10.1042/ebc20170093] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 01/24/2018] [Accepted: 01/29/2018] [Indexed: 02/04/2023]
Abstract
Import of preproteins into chloroplasts is an essential process, requiring two major multisubunit protein complexes that are embedded in the outer and inner chloroplast envelope membrane. Both the translocon of the outer chloroplast membrane (Toc), as well as the translocon of the inner chloroplast membrane (Tic) have been studied intensively with respect to their individual subunit compositions, functions and regulations. Recent advances in crystallography have increased our understanding of the operation of these proteins in terms of their interactions and regulation by conformational switching. Several subdomains of components of the Toc translocon have been studied at the structural level, among them the polypeptide transport-associated (POTRA) domain of the channel protein Toc75 and the GTPase domain of Toc34. In this review, we summarize and discuss the insight that has been gained from these structural analyses. In addition, we present the crystal structure of the Toc64 tetratrico-peptide repeat (TPR) domain in complex with the C-terminal domains of the heat-shock proteins (Hsp) Hsp90 and Hsp70.
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45
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Abstract
The plastids, including chloroplasts, are a group of interrelated organelles that confer photoautotrophic growth and the unique metabolic capabilities that are characteristic of plant systems. Plastid biogenesis relies on the expression, import, and assembly of thousands of nuclear encoded preproteins. Plastid proteomes undergo rapid remodeling in response to developmental and environmental signals to generate functionally distinct plastid types in specific cells and tissues. In this review, we will highlight the central role of the plastid protein import system in regulating and coordinating the import of functionally related sets of preproteins that are required for plastid-type transitions and maintenance.
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46
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Sofer L, Cabanillas DG, Gayral M, Téplier R, Pouzoulet J, Ducousso M, Dufin L, Bréhélin C, Ziegler-Graff V, Brault V, Revers F. Identification of host factors potentially involved in RTM-mediated resistance during potyvirus long distance movement. Arch Virol 2017; 162:1855-1865. [PMID: 28251380 DOI: 10.1007/s00705-017-3292-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 01/29/2017] [Indexed: 12/28/2022]
Abstract
The long distance movement of potyviruses is a poorly understood step of the viral cycle. Only factors inhibiting this process, referred to as "Restricted TEV Movement" (RTM), have been identified in Arabidopsis thaliana. On the virus side, the potyvirus coat protein (CP) displays determinants required for long-distance movement and for RTM-based resistance breaking. However, the potyvirus CP was previously shown not to interact with the RTM proteins. We undertook the identification of Arabidopsis factors which directly interact with either the RTM proteins or the CP of lettuce mosaic virus (LMV). An Arabidopsis cDNA library generated from companion cells was screened with LMV CP and RTM proteins using the yeast two-hybrid system. Fourteen interacting proteins were identified. Two of them were shown to interact with CP and the RTM proteins suggesting that a multiprotein complex could be formed between the RTM proteins and virions or viral ribonucleoprotein complexes. Co-localization experiments in Nicotiana benthamiana showed that most of the viral and cellular protein pairs co-localized at the periphery of chloroplasts which suggests a putative role for plastids in this process.
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Affiliation(s)
- Luc Sofer
- BFP, INRA, University of Bordeaux, 33140, Villenave d'Ornon, France
| | - Daniel Garcia Cabanillas
- BFP, INRA, University of Bordeaux, 33140, Villenave d'Ornon, France
- Institut National de la Recherche Scientifique-Institut Armand-Frappier, Laval, QC, H7V 1B7, Canada
| | - Mathieu Gayral
- BFP, INRA, University of Bordeaux, 33140, Villenave d'Ornon, France
| | - Rachèle Téplier
- BFP, INRA, University of Bordeaux, 33140, Villenave d'Ornon, France
| | - Jérôme Pouzoulet
- BFP, INRA, University of Bordeaux, 33140, Villenave d'Ornon, France
- Department of Botany and Plant Sciences, University of California, Riverside, CA, 92521, USA
| | - Marie Ducousso
- BFP, INRA, University of Bordeaux, 33140, Villenave d'Ornon, France
- UMR 0385 BGPI, Virus Insecte Plante, INRA, Campus international de Bailllarguet, Montpellier, France
| | - Laurène Dufin
- BFP, INRA, University of Bordeaux, 33140, Villenave d'Ornon, France
| | - Claire Bréhélin
- UMR 5200, Laboratory of Membrane Biogenesis, CNRS, University of Bordeaux, 33140, Villenave d'Ornon, France
| | - Véronique Ziegler-Graff
- Institut de Biologie Moléculaire des Plantes, Laboratoire propre du CNRS conventionné avec l'Université de Strasbourg, 12 rue du Général Zimmer, 67084, Strasbourg, France
| | | | - Frédéric Revers
- BFP, INRA, University of Bordeaux, 33140, Villenave d'Ornon, France.
- BIOGECO, INRA, University of Bordeaux, 33615, Pessac, France.
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47
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Zufferey M, Montandon C, Douet V, Demarsy E, Agne B, Baginsky S, Kessler F. The novel chloroplast outer membrane kinase KOC1 is a required component of the plastid protein import machinery. J Biol Chem 2017; 292:6952-6964. [PMID: 28283569 DOI: 10.1074/jbc.m117.776468] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 02/28/2017] [Indexed: 11/06/2022] Open
Abstract
The biogenesis and maintenance of cell organelles such as mitochondria and chloroplasts require the import of many proteins from the cytosol, a process that is controlled by phosphorylation. In the case of chloroplasts, the import of hundreds of different proteins depends on translocons at the outer and inner chloroplast membrane (TOC and TIC, respectively) complexes. The essential protein TOC159 functions thereby as an import receptor. It has an N-terminal acidic (A-) domain that extends into the cytosol, controls receptor specificity, and is highly phosphorylated in vivo However, kinases that phosphorylate the TOC159 A-domain to enable protein import have remained elusive. Here, using co-purification with TOC159 from Arabidopsis, we discovered a novel component of the chloroplast import machinery, the regulatory kinase at the outer chloroplast membrane 1 (KOC1). We found that KOC1 is an integral membrane protein facing the cytosol and stably associates with TOC. Moreover, KOC1 phosphorylated the A-domain of TOC159 in vitro, and in mutant koc1 chloroplasts, preprotein import efficiency was diminished. koc1 Arabidopsis seedlings had reduced survival rates after transfer from the dark to the light in which protein import into plastids is required to rapidly complete chloroplast biogenesis. In summary, our data indicate that KOC1 is a functional component of the TOC machinery that phosphorylates import receptors, supports preprotein import, and contributes to efficient chloroplast biogenesis.
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Affiliation(s)
- Mónica Zufferey
- From the Laboratory of Plant Physiology, University of Neuchâtel, 2000 Neuchâtel, Switzerland
| | - Cyrille Montandon
- the College of Agriculture and Life Sciences, Cornell University, Ithaca, New York 14853
| | - Véronique Douet
- From the Laboratory of Plant Physiology, University of Neuchâtel, 2000 Neuchâtel, Switzerland
| | - Emilie Demarsy
- the Department of Botany and Plant Biology, University of Geneva, 1211 Geneva, Switzerland, and
| | - Birgit Agne
- Institut für Biochemie und Biotechnologie, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle (Saale), Germany
| | - Sacha Baginsky
- Institut für Biochemie und Biotechnologie, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle (Saale), Germany
| | - Felix Kessler
- From the Laboratory of Plant Physiology, University of Neuchâtel, 2000 Neuchâtel, Switzerland,
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Wimmer D, Bohnhorst P, Shekhar V, Hwang I, Offermann S. Transit peptide elements mediate selective protein targeting to two different types of chloroplasts in the single-cell C4 species Bienertia sinuspersici. Sci Rep 2017; 7:41187. [PMID: 28112241 PMCID: PMC5253730 DOI: 10.1038/srep41187] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 12/16/2016] [Indexed: 01/23/2023] Open
Abstract
Bienertia sinuspersici is a terrestrial plant that performs C4 photosynthesis within individual cells through operating a carbon concentrating mechanism between different subcellular domains including two types of chloroplasts. It is currently unknown how differentiation of two highly specialized chloroplasts within the same cell occurs as no similar cases have been reported. Here we show that this differentiation in photosynthetic cells of B. sinuspersici is enabled by a transit peptide (TP) mediated selective protein targeting mechanism. Mutations in the TPs cause loss of selectivity but not general loss of chloroplast import, indicating the mechanism operates by specifically blocking protein accumulation in one chloroplast type. Hybrid studies indicate that this selectivity is transferable to transit peptides of plants which perform C4 by cooperative function of chloroplasts between two photosynthetic cells. Codon swap experiments as well as introducing an artificial bait mRNA show that RNA affects are not crucial for the sorting process. In summary, our analysis shows how the mechanism of subcellular targeting to form two types of chloroplast within the same cell can be achieved. This information is not only crucial for understanding single-cell C4 photosynthesis; it provides new insights in control of subcellular protein targeting in cell biology.
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Affiliation(s)
- Diana Wimmer
- Institute for Botany, Leibniz University Hannover, Herrenhaeuser Strasse 2, Hannover 30419, Germany
| | - Philipp Bohnhorst
- Institute for Botany, Leibniz University Hannover, Herrenhaeuser Strasse 2, Hannover 30419, Germany
| | - Vinay Shekhar
- Faculty of Biology, Department Biology I – Botany, Ludwig-Maximilians-University Muenchen, Grosshaderner Strasse 2-4, 82152 Planegg-Martinsried, Germany
| | - Inhwan Hwang
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790–784, Korea
| | - Sascha Offermann
- Institute for Botany, Leibniz University Hannover, Herrenhaeuser Strasse 2, Hannover 30419, Germany
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Sjuts I, Soll J, Bölter B. Import of Soluble Proteins into Chloroplasts and Potential Regulatory Mechanisms. FRONTIERS IN PLANT SCIENCE 2017; 8:168. [PMID: 28228773 PMCID: PMC5296341 DOI: 10.3389/fpls.2017.00168] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 01/26/2017] [Indexed: 05/20/2023]
Abstract
Chloroplasts originated from an endosymbiotic event in which a free-living cyanobacterium was engulfed by an ancestral eukaryotic host. During evolution the majority of the chloroplast genetic information was transferred to the host cell nucleus. As a consequence, proteins formerly encoded by the chloroplast genome are now translated in the cytosol and must be subsequently imported into the chloroplast. This process involves three steps: (i) cytosolic sorting procedures, (ii) binding to the designated receptor-equipped target organelle and (iii) the consecutive translocation process. During import, proteins have to overcome the two barriers of the chloroplast envelope, namely the outer envelope membrane (OEM) and the inner envelope membrane (IEM). In the majority of cases, this is facilitated by two distinct multiprotein complexes, located in the OEM and IEM, respectively, designated TOC and TIC. Plants are constantly exposed to fluctuating environmental conditions such as temperature and light and must therefore regulate protein composition within the chloroplast to ensure optimal functioning of elementary processes such as photosynthesis. In this review we will discuss the recent models of each individual import stage with regard to short-term strategies that plants might use to potentially acclimate to changes in their environmental conditions and preserve the chloroplast protein homeostasis.
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Affiliation(s)
- Inga Sjuts
- Department Biologie I-Botanik, Ludwig-Maximilians-UniversitätPlanegg-Martinsried, Germany
| | - Jürgen Soll
- Department Biologie I-Botanik, Ludwig-Maximilians-UniversitätPlanegg-Martinsried, Germany
- Munich Center for Integrated Protein Science CiPSM, Ludwig-Maximilians-UniversitätMunich, Germany
| | - Bettina Bölter
- Department Biologie I-Botanik, Ludwig-Maximilians-UniversitätPlanegg-Martinsried, Germany
- Munich Center for Integrated Protein Science CiPSM, Ludwig-Maximilians-UniversitätMunich, Germany
- *Correspondence: Bettina Bölter,
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Fine mapping of a dominant gene conferring chlorophyll-deficiency in Brassica napus. Sci Rep 2016; 6:31419. [PMID: 27506952 PMCID: PMC4979034 DOI: 10.1038/srep31419] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 07/20/2016] [Indexed: 11/21/2022] Open
Abstract
Leaf colour regulation is important in photosynthesis and dry material production. Most of the reported chlorophyll-deficient loci are recessive. The dominant locus is rarely reported, although it may be more important than the recessive locus in the regulation of photosynthesis efficiency. During the present study, we mapped a chlorophyll-deficient dominant locus (CDE1) from the ethyl methanesulfonate-mutagenized Brassica napus line NJ7982. Using an F2 population derived from the chlorophyll-deficient mutant (cde1) and the canola variety ‘zhongshuang11’, a high-density linkage map was constructed, consisting of 19 linkage groups with 2,878 bins containing 13,347 SNP markers, with a total linkage map length of 1,968.6 cM. Next, the CDE1 locus was mapped in a 0.9-cM interval of chromosome C08 of B. napus, co-segregating with nine SNP markers. In the following fine-mapping of the gene using the inherited F2:3 populations of 620 individuals, the locus was identified in an interval with a length of 311 kb. A bioinformatics analysis revealed that the mapping interval contained 22 genes. These results produced a good foundation for continued research on the dominant locus involved in chlorophyll content regulation.
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