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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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Kim DB, Na C, Hwang I, Lee DW. Understanding protein translocation across chloroplast membranes: Translocons and motor proteins. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2023; 65:408-416. [PMID: 36223071 DOI: 10.1111/jipb.13385] [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: 08/29/2022] [Accepted: 10/11/2022] [Indexed: 06/16/2023]
Abstract
Subcellular organelles in eukaryotes are surrounded by lipid membranes. In an endomembrane system, vesicle trafficking is the primary mechanism for the delivery of organellar proteins to specific organelles. However, organellar proteins for chloroplasts, mitochondria, the nucleus, and peroxisomes that are translated in the cytosol are directly imported into their target organelles. Chloroplasts are a plant-specific organelle with outer and inner envelope membranes, a dual-membrane structure that is similar to mitochondria. Interior chloroplast proteins translated by cytosolic ribosomes are thus translocated through TOC and TIC complexes (translocons in the outer and inner envelope of chloroplasts, respectively), with stromal ATPase motor proteins playing a critical role in pulling pre-proteins through these import channels. Over the last three decades, the identity and function of TOC/TIC components and stromal motor proteins have been actively investigated, which has shed light on the action mechanisms at a molecular level. However, there remains some disagreement over the exact composition of TIC complexes and genuine stromal motor proteins. In this review, we discuss recent findings on the mechanisms by which proteins are translocated through TOC/TIC complexes and discuss future prospects for this field of research.
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Affiliation(s)
- Da Been Kim
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju, 61186, Korea
| | - Changhee Na
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju, 61186, Korea
| | - Inhwan Hwang
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, 37673, Korea
| | - Dong Wook Lee
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju, 61186, Korea
- Department of Bioenergy Science and Technology, Chonnam National University, Gwangju, 61186, Korea
- Kumho Life Science Laboratory, Chonnam National University, Gwangju, 61186, Korea
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Schuhmann P, Engstler C, Klöpfer K, Gügel IL, Abbadi A, Dreyer F, Leckband G, Bölter B, Hagn F, Soll J, Carrie C. Two wrongs make a right: heat stress reversion of a male-sterile Brassica napus line. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:3531-3551. [PMID: 35226731 PMCID: PMC9162185 DOI: 10.1093/jxb/erac082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 02/28/2022] [Indexed: 06/14/2023]
Abstract
Male-sterile lines play important roles in plant breeding to obtain hybrid vigour. The male sterility Lembke (MSL) system is a thermosensitive genic male sterility system of Brassica napus and is one of the main systems used in European rapeseed breeding. Interestingly, the MSL system shows high similarity to the 9012AB breeding system from China, including the ability to revert to fertile in high temperature conditions. Here we demonstrate that the MSL system is regulated by the same restorer of fertility gene BnaC9-Tic40 as the 9012AB system, which is related to the translocon at the inner envelope membrane of chloroplasts 40 (TIC40) from Arabidopsis. The male sterility gene of the MSL system was also identified to encode a chloroplast-localized protein which we call BnChimera; this gene shows high sequence similarity to the sterility gene previously described for the 9012AB system. For the first time, a direct protein interaction between BnaC9-Tic40 and the BnChimera could be demonstrated. In addition, we identify the corresponding amino acids that mediate this interaction and suggest how BnaC9-Tic40 acts as the restorer of fertility. Using an RNA-seq approach, the effects of heat treatment on the male fertility restoration of the C545 MSL system line were investigated. These data demonstrate that many pollen developmental pathways are affected by higher temperatures. It is hypothesized that heat stress reverses the male sterility via a combination of slower production of cell wall precursors in plastids and a slower flower development, which ultimately results in fertile pollen. The potential breeding applications of these results are discussed regarding the use of the MSL system in producing thermotolerant fertile plants.
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Affiliation(s)
- Petra Schuhmann
- Department Biologie I–Botanik, Ludwig-Maximilians-Universität München, Großhadernerstr. 2–4, D-82152 Planegg-Martinsried, Germany
| | - Carina Engstler
- Department Biologie I–Botanik, Ludwig-Maximilians-Universität München, Großhadernerstr. 2–4, D-82152 Planegg-Martinsried, Germany
| | - Kai Klöpfer
- Bavarian NMR Center (BNMRZ) at the Department of Chemistry, Technical University of Munich, Lichtenbergstrasse 4, D-85748 Garching, Germany
| | - Irene L Gügel
- Department Biologie I–Botanik, Ludwig-Maximilians-Universität München, Großhadernerstr. 2–4, D-82152 Planegg-Martinsried, Germany
- Center of Advanced European Studies and Research (caesar), Ludwig-Erhard-Allee 2, D-53175 Bonn, Germany
| | - Amine Abbadi
- NPZ Innovation GmbH, Hohenlieth-Hof, D-24363 Holtsee, Germany
| | - Felix Dreyer
- NPZ Innovation GmbH, Hohenlieth-Hof, D-24363 Holtsee, Germany
| | - Gunhild Leckband
- Norddeutsche Pflanzenzucht Hans-Georg Lembke KG, Hohenlieth-Hof 1, D-24363 Holtsee, Germany
| | - Bettina Bölter
- Department Biologie I–Botanik, Ludwig-Maximilians-Universität München, Großhadernerstr. 2–4, D-82152 Planegg-Martinsried, Germany
| | - Franz Hagn
- Bavarian NMR Center (BNMRZ) at the Department of Chemistry, Technical University of Munich, Lichtenbergstrasse 4, D-85748 Garching, Germany
- Institute of Structural Biology, Helmholtz Zentrum München, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany
| | - Jürgen Soll
- Department Biologie I–Botanik, Ludwig-Maximilians-Universität München, Großhadernerstr. 2–4, D-82152 Planegg-Martinsried, Germany
- Munich Centre for Integrated Protein Science, CIPSM, Ludwig-Maximilians-Universität München, Feodor-Lynen-Str. 25, D-81377 Munich, Germany
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Yu H, Wang Q, Zhang Z, Wu T, Yang X, Zhu X, Ye Y, Leng J, Yang S, Feng X. Genetic Mapping of the Gmpgl3 Mutant Reveals the Function of GmTic110a in Soybean Chloroplast Development. FRONTIERS IN PLANT SCIENCE 2022; 13:892077. [PMID: 35693168 PMCID: PMC9178232 DOI: 10.3389/fpls.2022.892077] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 05/09/2022] [Indexed: 06/15/2023]
Abstract
The generation of oxygen and organic matter in plants mainly depends on photosynthesis, which directly affects plant growth and development. The chloroplast is the main organelle in which photosynthesis occurs. In this study, a Glycine max pale green leaf 3-1 (Gmpgl3-1) mutant was isolated from the soybean mutagenized population. The Gmpgl3-1 mutant presented with decreased chlorophyll contents, reduced chloroplast stroma thylakoids, reduced yields, and decreased numbers of pods per plant. Bulked segregant analysis (BSA) together with map-based cloning revealed a single-nucleotide non-synonymous mutation at the 341st nucleotide of the first exon of the chloroplast development-related GmTic110a gene. The phenotype of the knockout plants was the same as that of the mutant. The GmTic110a gene was highly expressed in the leaves at various developmental stages, and its protein was localized to the inner chloroplast membrane. Split luciferase complementation assays and coimmunoprecipitation (co-IP) experiments revealed that GmTic110a interacted with GmTic20, GmTic40a, and GmTic40b in tobacco leaves. These results indicated that the GmTic110a gene plays an important role in chloroplast development.
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Affiliation(s)
- Hui Yu
- Key Laboratory of Soybean Molecular Design Breeding, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China
| | - Qiushi Wang
- Key Laboratory of Soybean Molecular Design Breeding, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China
| | - Zhirui Zhang
- Key Laboratory of Soybean Molecular Design Breeding, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Tao Wu
- Key Laboratory of Soybean Molecular Design Breeding, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Xinjing Yang
- Key Laboratory of Soybean Molecular Design Breeding, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Xiaobin Zhu
- Key Laboratory of Soybean Molecular Design Breeding, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Yongheng Ye
- Key Laboratory of Soybean Molecular Design Breeding, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Jiantian Leng
- Key Laboratory of Soybean Molecular Design Breeding, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China
| | - Suxin Yang
- Key Laboratory of Soybean Molecular Design Breeding, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China
| | - Xianzhong Feng
- Key Laboratory of Soybean Molecular Design Breeding, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China
- Zhejiang Lab, Hangzhou, China
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Jeong J, Hwang I, Lee DW. Functional Organization of Sequence Motifs in Diverse Transit Peptides of Chloroplast Proteins. Front Physiol 2021; 12:795156. [PMID: 34880786 PMCID: PMC8645953 DOI: 10.3389/fphys.2021.795156] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 10/28/2021] [Indexed: 11/17/2022] Open
Abstract
Although the chloroplasts in plants are characterized by an inherent genome, the chloroplast proteome is composed of proteins encoded by not only the chloroplast genome but also the nuclear genome. Nuclear-encoded chloroplast proteins are synthesized on cytosolic ribosomes and post-translationally targeted to the chloroplasts. In the latter process, an N-terminal cleavable transit peptide serves as a targeting signal required for the import of nuclear-encoded chloroplast interior proteins. This import process is mediated via an interaction between the sequence motifs in transit peptides and the components of the TOC/TIC (translocon at the outer/inner envelope of chloroplasts) translocons. Despite a considerable diversity in primary structures, several common features have been identified among transit peptides, including N-terminal moderate hydrophobicity, multiple proline residues dispersed throughout the transit peptide, preferential usage of basic residues over acidic residues, and an absence of N-terminal arginine residues. In this review, we will recapitulate and discuss recent progress in our current understanding of the functional organization of sequence elements commonly present in diverse transit peptides, which are essential for the multi-step import of chloroplast proteins.
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Affiliation(s)
- Jinseung Jeong
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju, South Korea
| | - Inhwan Hwang
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, South Korea
| | - Dong Wook Lee
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju, South Korea.,Department of Bioenergy Science and Technology, Chonnam National University, Gwangju, South Korea
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Protein import into chloroplasts and its regulation by the ubiquitin-proteasome system. Biochem Soc Trans 2020; 48:71-82. [PMID: 31922184 PMCID: PMC7054747 DOI: 10.1042/bst20190274] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 12/19/2019] [Accepted: 12/23/2019] [Indexed: 02/08/2023]
Abstract
Chloroplasts are photosynthetic plant organelles descended from a bacterial ancestor. The vast majority of chloroplast proteins are synthesized in the cytosol and then imported into the chloroplast post-translationally. Translocation complexes exist in the organelle's outer and inner envelope membranes (termed TOC and TIC, respectively) to facilitate protein import. These systems recognize chloroplast precursor proteins and mediate their import in an energy-dependent manner. However, many unanswered questions remain regarding mechanistic details of the import process and the participation and functions of individual components; for example, the cytosolic events that mediate protein delivery to chloroplasts, the composition of the TIC apparatus, and the nature of the protein import motor all require resolution. The flux of proteins through TOC and TIC varies greatly throughout development and in response to specific environmental cues. The import process is, therefore, tightly regulated, and it has emerged that the ubiquitin-proteasome system (UPS) plays a key role in this regard, acting at several different steps in the process. The UPS is involved in: the selective degradation of transcription factors that co-ordinate the expression of chloroplast precursor proteins; the removal of unimported chloroplast precursor proteins in the cytosol; the inhibition of chloroplast biogenesis pre-germination; and the reconfiguration of the TOC apparatus in response to developmental and environmental signals in a process termed chloroplast-associated protein degradation. In this review, we highlight recent advances in our understanding of protein import into chloroplasts and how this process is regulated by the UPS.
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