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Isono E, Li J, Pulido P, Siao W, Spoel SH, Wang Z, Zhuang X, Trujillo M. Protein degrons and degradation: Exploring substrate recognition and pathway selection in plants. THE PLANT CELL 2024; 36:3074-3098. [PMID: 38701343 PMCID: PMC11371205 DOI: 10.1093/plcell/koae141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Revised: 03/27/2024] [Accepted: 04/07/2024] [Indexed: 05/05/2024]
Abstract
Proteome composition is dynamic and influenced by many internal and external cues, including developmental signals, light availability, or environmental stresses. Protein degradation, in synergy with protein biosynthesis, allows cells to respond to various stimuli and adapt by reshaping the proteome. Protein degradation mediates the final and irreversible disassembly of proteins, which is important for protein quality control and to eliminate misfolded or damaged proteins, as well as entire organelles. Consequently, it contributes to cell resilience by buffering against protein or organellar damage caused by stresses. Moreover, protein degradation plays important roles in cell signaling, as well as transcriptional and translational events. The intricate task of recognizing specific proteins for degradation is achieved by specialized systems that are tailored to the substrate's physicochemical properties and subcellular localization. These systems recognize diverse substrate cues collectively referred to as "degrons," which can assume a range of configurations. They are molecular surfaces recognized by E3 ligases of the ubiquitin-proteasome system but can also be considered as general features recognized by other degradation systems, including autophagy or even organellar proteases. Here we provide an overview of the newest developments in the field, delving into the intricate processes of protein recognition and elucidating the pathways through which they are recruited for degradation.
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Affiliation(s)
- Erika Isono
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| | - Jianming Li
- Department of Biology, Hong Kong Baptist University, Kowloon Tong, Hong Kong
| | - Pablo Pulido
- Department of Plant Molecular Genetics, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas (CNB-CSIC), 28049 Madrid, Spain
| | - Wei Siao
- Department of Biology, Aachen RWTH University, Institute of Molecular Plant Physiology, 52074 Aachen, Germany
| | - Steven H Spoel
- Institute of Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - Zhishuo Wang
- Institute of Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - Xiaohong Zhuang
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Marco Trujillo
- Department of Biology, Aachen RWTH University, Institute of Molecular Plant Physiology, 52074 Aachen, Germany
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2
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Žárský V. Exocyst functions in plants - secretion and autophagy. FEBS Lett 2022; 596:2324-2334. [PMID: 35729750 DOI: 10.1002/1873-3468.14430] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 06/03/2022] [Accepted: 06/03/2022] [Indexed: 11/09/2022]
Abstract
Tethering complexes mediate vesicle-target compartment contact. Octameric complex exocyst initiates vesicle exocytosis at specific cytoplasmic membrane domains. Plant exocyst is possibly stabilized at the membrane by a direct interaction between SEC3 and EXO70A. Land plants evolved three basic membrane-targeting EXO70 subfamilies, the evolution of which resulted in several types of exocyst with distinct functions within the same cell. Surprisingly, some of these EXO70-exocyst versions are implicated in autophagy as is animal exocyst or are involved in host defense, cell-wall fortification and secondary metabolites transport. Interestingly, EXO70Ds act as selective autophagy receptors in the regulation of cytokinin signalling pathway. Secretion of double membrane autophagy-related structures formed with the contribution of EXO70s to the apoplast hints at the possibility of secretory autophagy in plants.
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Affiliation(s)
- Viktor Žárský
- Department of Experimental Plant Biology, Faculty of Science, Charles University in Prague, Viničná 5, 128 44, Prague, Czech Republic.,Institute of Experimental Botany, v.v.i., Czech Academy of Sciences, Rozvojová 263, 165 02, Prague, Czech Republic
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3
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Brillada C, Teh OK, Ditengou FA, Lee CW, Klecker T, Saeed B, Furlan G, Zietz M, Hause G, Eschen-Lippold L, Hoehenwarter W, Lee J, Ott T, Trujillo M. Exocyst subunit Exo70B2 is linked to immune signaling and autophagy. THE PLANT CELL 2021; 33:404-419. [PMID: 33630076 PMCID: PMC8136888 DOI: 10.1093/plcell/koaa022] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 11/18/2020] [Indexed: 05/08/2023]
Abstract
During the immune response, activation of the secretory pathway is key to mounting an effective response, while gauging its output is important to maintain cellular homeostasis. The Exo70 subunit of the exocyst functions as a spatiotemporal regulator by mediating numerous interactions with proteins and lipids. However, a molecular understanding of the exocyst regulation remains challenging. We show that, in Arabidopsis thaliana, Exo70B2 behaves as a bona fide exocyst subunit. Conversely, treatment with the salicylic acid (SA) defence hormone analog benzothiadiazole (BTH), or the immunogenic peptide flg22, induced Exo70B2 transport into the vacuole. We reveal that Exo70B2 interacts with AUTOPHAGY-RELATED PROTEIN 8 (ATG8) via two ATG8-interacting motives (AIMs) and its transport into the vacuole is dependent on autophagy. In line with its role in immunity, we discovered that Exo70B2 interacted with and was phosphorylated by the kinase MPK3. Mimicking phosphorylation had a dual impact on Exo70B2: first, by inhibiting localization at sites of active secretion, and second, it increased the interaction with ATG8. Phosphonull variants displayed higher effector-triggered immunity (ETI) and were hypersensitive to BTH, which induce secretion and autophagy. Our results suggest a molecular mechanism by which phosphorylation diverts Exo70B2 from the secretory into the autophagy pathway for its degradation, to dampen secretory activity.
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Affiliation(s)
- Carla Brillada
- Faculty of Biology, Cell Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Ooi-Kock Teh
- Leibniz Institute of Plant Biochemistry, 06120 Halle (Saale), Germany
- Department of Biological Science, School of Science, Hokkaido University, 060-0810 Sapporo, Japan
- Institute for the Advancement of Higher Education, Hokkaido University, 060-0815 Sapporo, Japan
| | | | - Chil-Woo Lee
- Leibniz Institute of Plant Biochemistry, 06120 Halle (Saale), Germany
| | - Till Klecker
- Institute of Cell Biology, University of Bayreuth, 95440 Bayreuth, Germany
| | - Bushra Saeed
- Faculty of Biology, Cell Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Giulia Furlan
- Leibniz Institute of Plant Biochemistry, 06120 Halle (Saale), Germany
| | - Marco Zietz
- Leibniz Institute of Plant Biochemistry, 06120 Halle (Saale), Germany
| | - Gerd Hause
- Biozentrum, Martin-Luther-University Halle-Wittenberg, Halle 06120 (Saale), Germany
| | | | | | - Justin Lee
- Leibniz Institute of Plant Biochemistry, 06120 Halle (Saale), Germany
| | - Thomas Ott
- Faculty of Biology, Cell Biology, University of Freiburg, 79104 Freiburg, Germany
- CIBSS—Centre for Integrative Biological Signalling Studies, University of Freiburg, 79085 Freiburg, Germany
| | - Marco Trujillo
- Faculty of Biology, Cell Biology, University of Freiburg, 79104 Freiburg, Germany
- Leibniz Institute of Plant Biochemistry, 06120 Halle (Saale), Germany
- Author for communication:
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4
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Glutamatergic Receptor Trafficking and Delivery: Role of the Exocyst Complex. Cells 2020; 9:cells9112402. [PMID: 33153008 PMCID: PMC7693776 DOI: 10.3390/cells9112402] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 10/21/2020] [Accepted: 10/23/2020] [Indexed: 12/29/2022] Open
Abstract
Cells comprise several intracellular membrane compartments that allow them to function properly. One of these functions is cargo movement, typically proteins and membranes within cells. These cargoes ride microtubules through vesicles from Golgi and recycling endosomes to the plasma membrane in order to be delivered and exocytosed. In neurons, synaptic functions employ this cargo trafficking to maintain inter-neuronal communication optimally. One of the complexes that oversee vesicle trafficking and tethering is the exocyst. The exocyst is a protein complex containing eight subunits first identified in yeast and then characterized in multicellular organisms. This complex is related to several cellular processes, including cellular growth, division, migration, and morphogenesis, among others. It has been associated with glutamatergic receptor trafficking and tethering into the synapse, providing the molecular machinery to deliver receptor-containing vesicles into the plasma membrane in a constitutive manner. In this review, we discuss the evidence so far published regarding receptor trafficking and the exocyst complex in both basal and stimulated levels, comparing constitutive trafficking and long-term potentiation-related trafficking.
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Bu F, Yang M, Guo X, Huang W, Chen L. Multiple Functions of ATG8 Family Proteins in Plant Autophagy. Front Cell Dev Biol 2020; 8:466. [PMID: 32596242 PMCID: PMC7301642 DOI: 10.3389/fcell.2020.00466] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 05/19/2020] [Indexed: 11/13/2022] Open
Abstract
Autophagy is a major degradation process of cytoplasmic components in eukaryotes, and executes both bulk and selective degradation of targeted cargos. A set of autophagy-related (ATG) proteins participate in various stages of the autophagic process. Among ATGs, ubiquitin-like protein ATG8 plays a central role in autophagy. The ATG8 protein is conjugated to the membrane lipid phosphatidylethanolamine in a ubiquitin-like conjugation reaction that is essential for autophagosome formation. In addition, ATG8 interacts with various adaptor/receptor proteins to recruit specific cargos for degradation by selective autophagy. The ATG8-interacting proteins usually contain the ATG8-interacting motif (AIM) or the ubiquitin-interacting motif (UIM) for ATG8 binding. Unlike a single ATG8 gene in yeast, multiple ATG8 orthologs have been identified in the plant kingdom. The large diversity within the ATG8 family may explain the various functions of selective autophagy in plants. Here, we discuss and summarize the current view of the structure and function of ATG8 proteins in plants.
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Affiliation(s)
- Fan Bu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Sciences, South China Agricultural University, Guangzhou, China
| | - Mingkang Yang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Sciences, South China Agricultural University, Guangzhou, China
| | - Xu Guo
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Sciences, South China Agricultural University, Guangzhou, China
| | - Wei Huang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Sciences, South China Agricultural University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China
| | - Liang Chen
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Sciences, South China Agricultural University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China
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6
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Wun CL, Quan Y, Zhuang X. Recent Advances in Membrane Shaping for Plant Autophagosome Biogenesis. FRONTIERS IN PLANT SCIENCE 2020; 11:565. [PMID: 32547570 PMCID: PMC7270194 DOI: 10.3389/fpls.2020.00565] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 04/15/2020] [Indexed: 06/11/2023]
Abstract
Autophagy is an intracellular degradation process, which is highly conserved in eukaryotes. During this process, unwanted cytosolic constituents are sequestered and delivered into the vacuole/lysosome by a double-membrane organelle known as an autophagosome. The autophagosome initiates from a membrane sac named the phagophore, and after phagophore expansion and closure, the outer membrane fuses with the vacuole/lysosome to release the autophagic body into the vacuole. Membrane sources derived from the endomembrane system (e.g., Endoplasmic Reticulum, Golgi and endosome) have been implicated to contribute to autophagosome in different steps (initiation, expansion or maturation). Therefore, coordination between the autophagy-related (ATG) proteins and membrane tethers from the endomembrane system is required during autophagosome biogenesis. In this review, we will update recent findings with a focus on comparing the selected core ATG complexes and the endomembrane tethering machineries for shaping the autophagosome membrane in yeast, mammal, and plant systems.
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7
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Žárský V, Sekereš J, Kubátová Z, Pečenková T, Cvrčková F. Three subfamilies of exocyst EXO70 family subunits in land plants: early divergence and ongoing functional specialization. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:49-62. [PMID: 31647563 DOI: 10.1093/jxb/erz423] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Accepted: 10/10/2019] [Indexed: 05/27/2023]
Abstract
Localized delivery of plasma membrane and cell wall components is an essential process in all plant cells. The vesicle-tethering complex, the exocyst, an ancient eukaryotic hetero-octameric protein cellular module, assists in targeted delivery of exocytosis vesicles to specific plasma membrane domains. Analyses of Arabidopsis and later other land plant genomes led to the surprising prediction of multiple putative EXO70 exocyst subunit paralogues. All land plant EXO70 exocyst subunits (including those of Bryophytes) form three distinct subfamilies-EXO70.1, EXO70.2, and EXO70.3. Interestingly, while the basal well-conserved EXO70.1 subfamily consists of multiexon genes, the remaining two subfamilies contain mostly single exon genes. Published analyses as well as public transcriptomic and proteomic data clearly indicate that most cell types in plants express and also use several different EXO70 isoforms. Here we sum up recent advances in the characterization of the members of the family of plant EXO70 exocyst subunits and present evidence that members of the EXO70.2 subfamily are often recruited to non-canonical functions in plant membrane trafficking pathways. Engagement of the most evolutionarily dynamic EXO70.2 subfamily of EXO70s in biotic interactions and defence correlates well with massive proliferation and conservation of new protein variants in this subfamily.
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Affiliation(s)
- Viktor Žárský
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Viničná, Prague, Czech Republic
- Institute of Experimental Botany, v.v.i., Czech Academy of Sciences, Rozvojová, Prague, Czech Republic
| | - Juraj Sekereš
- Institute of Experimental Botany, v.v.i., Czech Academy of Sciences, Rozvojová, Prague, Czech Republic
| | - Zdeňka Kubátová
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Viničná, Prague, Czech Republic
| | - Tamara Pečenková
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Viničná, Prague, Czech Republic
- Institute of Experimental Botany, v.v.i., Czech Academy of Sciences, Rozvojová, Prague, Czech Republic
| | - Fatima Cvrčková
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Viničná, Prague, Czech Republic
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8
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Saeed B, Brillada C, Trujillo M. Dissecting the plant exocyst. CURRENT OPINION IN PLANT BIOLOGY 2019; 52:69-76. [PMID: 31509792 DOI: 10.1016/j.pbi.2019.08.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 07/12/2019] [Accepted: 08/08/2019] [Indexed: 06/10/2023]
Abstract
The exocyst is an evolutionary conserved complex that mediates tethering of post-Golgi vesicles derived from the conventional secretory pathway to the plasma membrane (PM), before SNARE-mediated fusion. Through its tethering function, connecting secretory vesicles to the PM, it mediates spatiotemporal regulation of exocytosis. As an integral element of the secretory machinery, the exocyst has been implicated in a large variety of processes. However, emerging evidence suggests that it may also cater for unconventional secretory pathways, as well as autophagy. The exocyst entertains a multitude of interactions with proteins and membrane phospholipids, reflecting its highly dynamic nature and the complex regulatory processes that hardwire it with cellular signalling networks. However, our molecular understanding of this essential complex remains fragmentary. Here we review recent work focusing on the molecular features that have revealed both commonalities with yeast and animals, as well as unique characteristics of the plant exocyst.
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Affiliation(s)
- Bushra Saeed
- Albert-Ludwigs-University Freiburg, Faculty of Biology, Institute of Biology II, 79104 Freiburg, Germany
| | - Carla Brillada
- Albert-Ludwigs-University Freiburg, Faculty of Biology, Institute of Biology II, 79104 Freiburg, Germany
| | - Marco Trujillo
- Albert-Ludwigs-University Freiburg, Faculty of Biology, Institute of Biology II, 79104 Freiburg, Germany.
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9
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New advances in autophagy in plants: Regulation, selectivity and function. Semin Cell Dev Biol 2017; 80:113-122. [PMID: 28734771 DOI: 10.1016/j.semcdb.2017.07.018] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 07/08/2017] [Accepted: 07/15/2017] [Indexed: 01/01/2023]
Abstract
Autophagy is a major and conserved pathway for delivering unwanted proteins or damaged organelles to the vacuole for degradation and recycling. In plants, it functions as a housekeeping process to maintain cellular homeostasis under normal conditions and is induced by stress and senescence; it thus plays important roles in development, stress tolerance and metabolism. Autophagy can both execute bulk degradation and be highly selective in targeting cargos under specific environmental conditions or during certain developmental processes. Here, we review recent research on autophagy in plants, and discuss new insights into its core mechanism, regulation, selectivity and physiological roles. Potential future directions are also highlighted.
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10
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Seo DH, Ahn MY, Park KY, Kim EY, Kim WT. The N-Terminal UND Motif of the Arabidopsis U-Box E3 Ligase PUB18 Is Critical for the Negative Regulation of ABA-Mediated Stomatal Movement and Determines Its Ubiquitination Specificity for Exocyst Subunit Exo70B1. THE PLANT CELL 2016; 28:2952-2973. [PMID: 27956469 PMCID: PMC5240735 DOI: 10.1105/tpc.16.00347] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 11/18/2016] [Accepted: 12/09/2016] [Indexed: 05/20/2023]
Abstract
The Arabidopsis thaliana U-box E3 ligases PUB18/PUB19 and PUB22/PUB23 are negative regulators of drought stress responses. PUB18/PUB19 regulate the drought stress response in an abscisic acid (ABA)-dependent manner, whereas PUB22/PUB23 regulate this response in an ABA-independent manner. A major structural difference between PUB18/PUB19 and PUB22/PUB23 is the presence of the UND (U-box N-terminal domain). Here, we focused on elucidating the molecular mechanism that mediates the functional difference between PUB18 and PUB22 and found that the UNDPUB18 was critically involved in the negative regulation of ABA-mediated stomatal movements. Exo70B1, a subunit of the exocyst complex, was identified as a target of PUB18, whereas Exo70B2 was a substrate of PUB22. However, the ∆UND-PUB18 derivative failed to ubiquitinate Exo70B1, but ubiquitinated Exo70B2. By contrast, the UNDPUB18-PUB22 chimeric protein ubiquitinated Exo70B1 instead of Exo70B2, suggesting that the ubiquitination specificities of PUB18 and PUB22 to Exo70B1 and Exo70B2, respectively, are dependent on the presence or absence of the UNDPUB18 motif. The ABA-insensitive phenotypes of the pub18 pub19 exo70b1 triple mutant were reminiscent of those of exo70b1 rather than pub18 pub19, indicating that Exo70B1 functions downstream of PUB18. Overall, our results suggest that the UNDPUB18 motif is crucial for the negative regulation of ABA-dependent stomatal movement and for determination of its ubiquitination specificity to Exo70B1.
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Affiliation(s)
- Dong Hye Seo
- Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea
| | - Min Yong Ahn
- Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea
| | - Ki Youl Park
- Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea
| | - Eun Yu Kim
- Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea
| | - Woo Taek Kim
- Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea
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11
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Xie Q, Tzfadia O, Levy M, Weithorn E, Peled-Zehavi H, Van Parys T, Van de Peer Y, Galili G. hfAIM: A reliable bioinformatics approach for in silico genome-wide identification of autophagy-associated Atg8-interacting motifs in various organisms. Autophagy 2016; 12:876-87. [PMID: 27071037 DOI: 10.1080/15548627.2016.1147668] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Most of the proteins that are specifically turned over by selective autophagy are recognized by the presence of short Atg8 interacting motifs (AIMs) that facilitate their association with the autophagy apparatus. Such AIMs can be identified by bioinformatics methods based on their defined degenerate consensus F/W/Y-X-X-L/I/V sequences in which X represents any amino acid. Achieving reliability and/or fidelity of the prediction of such AIMs on a genome-wide scale represents a major challenge. Here, we present a bioinformatics approach, high fidelity AIM (hfAIM), which uses additional sequence requirements-the presence of acidic amino acids and the absence of positively charged amino acids in certain positions-to reliably identify AIMs in proteins. We demonstrate that the use of the hfAIM method allows for in silico high fidelity prediction of AIMs in AIM-containing proteins (ACPs) on a genome-wide scale in various organisms. Furthermore, by using hfAIM to identify putative AIMs in the Arabidopsis proteome, we illustrate a potential contribution of selective autophagy to various biological processes. More specifically, we identified 9 peroxisomal PEX proteins that contain hfAIM motifs, among which AtPEX1, AtPEX6 and AtPEX10 possess evolutionary-conserved AIMs. Bimolecular fluorescence complementation (BiFC) results verified that AtPEX6 and AtPEX10 indeed interact with Atg8 in planta. In addition, we show that mutations occurring within or nearby hfAIMs in PEX1, PEX6 and PEX10 caused defects in the growth and development of various organisms. Taken together, the above results suggest that the hfAIM tool can be used to effectively perform genome-wide in silico screens of proteins that are potentially regulated by selective autophagy. The hfAIM system is a web tool that can be accessed at link: http://bioinformatics.psb.ugent.be/hfAIM/.
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Affiliation(s)
- Qingjun Xie
- a Department of Plant and Environmental Science , Weizmann Institute of Science , Rehovotx , Israel
| | - Oren Tzfadia
- a Department of Plant and Environmental Science , Weizmann Institute of Science , Rehovotx , Israel.,b Department of Plant Systems Biology , VIB , Ghent , Belgium.,c Department of Plant Biotechnology and Bioinformatics , Ghent University , Ghent , Belgium.,d Bioinformatics Institute Ghent, Ghent University , Ghent , Belgium
| | - Matan Levy
- a Department of Plant and Environmental Science , Weizmann Institute of Science , Rehovotx , Israel
| | - Efrat Weithorn
- a Department of Plant and Environmental Science , Weizmann Institute of Science , Rehovotx , Israel
| | - Hadas Peled-Zehavi
- a Department of Plant and Environmental Science , Weizmann Institute of Science , Rehovotx , Israel
| | - Thomas Van Parys
- b Department of Plant Systems Biology , VIB , Ghent , Belgium.,c Department of Plant Biotechnology and Bioinformatics , Ghent University , Ghent , Belgium.,d Bioinformatics Institute Ghent, Ghent University , Ghent , Belgium
| | - Yves Van de Peer
- b Department of Plant Systems Biology , VIB , Ghent , Belgium.,c Department of Plant Biotechnology and Bioinformatics , Ghent University , Ghent , Belgium.,d Bioinformatics Institute Ghent, Ghent University , Ghent , Belgium.,e Genomics Research Institute (GRI), University of Pretoria , Pretoria , South Africa
| | - Gad Galili
- a Department of Plant and Environmental Science , Weizmann Institute of Science , Rehovotx , Israel
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12
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Pečenková T, Sabol P, Kulich I, Ortmannová J, Žárský V. Constitutive Negative Regulation of R Proteins in Arabidopsis also via Autophagy Related Pathway? FRONTIERS IN PLANT SCIENCE 2016; 7:260. [PMID: 26973696 PMCID: PMC4777726 DOI: 10.3389/fpls.2016.00260] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 02/18/2016] [Indexed: 05/29/2023]
Abstract
Even though resistance (R) genes are among the most studied components of the plant immunity, there remain still a lot of aspects to be explained about the regulation of their function. Many gain-of-function mutants of R genes and loss-of-function of their regulators often demonstrate up-regulated defense responses in combination with dwarf stature and/or spontaneous leaf lesions formation. For most of these mutants, phenotypes are a consequence of an ectopic activation of R genes. Based on the compilation and comparison of published results in this field, we have concluded that the constitutively activated defense phenotypes recurrently arise by disruption of tight, constitutive and multilevel negative control of some of R proteins that might involve also their targeting to the autophagy pathway. This mode of R protein regulation is supported also by protein-protein interactions listed in available databases, as well as in silico search for autophagy machinery interacting motifs. The suggested model could resolve some explanatory discrepancies found in the studies of the immunity responses of autophagy mutants.
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Affiliation(s)
- Tamara Pečenková
- Laboratory of Cell Biology, Institute of Experimental Botany, Academy of Sciences of Czech RepublicPrague, Czech Republic
- Laboratory of Cell Morphogenesis, Department of Experimental Plant Biology, Faculty of Science, Charles University in PraguePrague, Czech Republic
| | - Peter Sabol
- Laboratory of Cell Morphogenesis, Department of Experimental Plant Biology, Faculty of Science, Charles University in PraguePrague, Czech Republic
| | - Ivan Kulich
- Laboratory of Cell Morphogenesis, Department of Experimental Plant Biology, Faculty of Science, Charles University in PraguePrague, Czech Republic
| | - Jitka Ortmannová
- Laboratory of Cell Biology, Institute of Experimental Botany, Academy of Sciences of Czech RepublicPrague, Czech Republic
- Laboratory of Cell Morphogenesis, Department of Experimental Plant Biology, Faculty of Science, Charles University in PraguePrague, Czech Republic
| | - Viktor Žárský
- Laboratory of Cell Biology, Institute of Experimental Botany, Academy of Sciences of Czech RepublicPrague, Czech Republic
- Laboratory of Cell Morphogenesis, Department of Experimental Plant Biology, Faculty of Science, Charles University in PraguePrague, Czech Republic
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Michaeli S, Galili G, Genschik P, Fernie AR, Avin-Wittenberg T. Autophagy in Plants--What's New on the Menu? TRENDS IN PLANT SCIENCE 2016; 21:134-144. [PMID: 26598298 DOI: 10.1016/j.tplants.2015.10.008] [Citation(s) in RCA: 153] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 09/22/2015] [Accepted: 10/13/2015] [Indexed: 05/02/2023]
Abstract
Autophagy is a major cellular degradation pathway in eukaryotes. Recent studies have revealed the importance of autophagy in many aspects of plant life, including seedling establishment, plant development, stress resistance, metabolism, and reproduction. This is manifested by the dual ability of autophagy to execute bulk degradation under severe environmental conditions, while simultaneously to be highly selective in targeting specific compartments and protein complexes to regulate key cellular processes, even during favorable growth conditions. Delivery of cellular components to the vacuole enables their recycling, affecting the plant metabolome, especially under stress. Recent research in Arabidopsis has further unveiled fundamental mechanistic aspects in autophagy which may have relevance in non-plant systems. We review the most recent discoveries concerning autophagy in plants, touching upon all these aspects.
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Affiliation(s)
- Simon Michaeli
- Biochimie et Physiologie Moléculaire des Plantes, Unité Mixte de Recherche 5004 Centre National de la Recherche Scientifique (CNRS)/Institut National de la Recherche Agronomique (INRA)/Université de Montpellier 2 (UM2)/SupAgro, 2 Place Viala, 34060 Montpellier, France
| | - Gad Galili
- Weizmann Institute of Science, 234 Herzl Street, 7610001 Rehovot, Israel
| | - Pascal Genschik
- Institut de Biologie Moléculaire des Plantes, CNRS Unité Propre de Recherche 2357, Conventionné avec l'Université de Strasbourg, 67084 Strasbourg, France
| | - Alisdair R Fernie
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Tamar Avin-Wittenberg
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Potsdam, Germany.
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14
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Robinson DG, Ding Y, Jiang L. Unconventional protein secretion in plants: a critical assessment. PROTOPLASMA 2016; 253:31-43. [PMID: 26410830 DOI: 10.1007/s00709-015-0887-1] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 09/18/2015] [Indexed: 05/27/2023]
Abstract
Unconventional protein secretion (UPS) is a collective term for mechanisms by which cytosolic proteins that lack a signal peptide ("leaderless secretory proteins" (LSPs)) can gain access to the cell exterior. Numerous examples of UPS have been well documented in animal and yeast cells. In contrast, our understanding of the mechanism(s) and function of UPS in plants is very limited. This review evaluates the available literature on this subject. The apparent large numbers of LSPs in the plant secretome suggest that UPS also occurs in plants but is not a proof. Although the direct transport of LSPs across the plant plasma membrane (PM) has not yet been described, it is possible that as in other eukaryotes, exosomes may be released from plant cells through fusion of multivesicular bodies (MVBs) with the PM. In this way, LSPs, but also small RNAs (sRNAs), that are passively taken up from the cytosol into the intraluminal vesicles of MVBs, could reach the apoplast. Another possible mechanism is the recently discovered exocyst-positive organelle (EXPO), a double-membrane-bound compartment, distinct from autophagosomes, which appears to sequester LSPs.
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Affiliation(s)
- David G Robinson
- Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 230, D-69120, Heidelberg, Germany.
| | - Yu Ding
- Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Liwen Jiang
- Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
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15
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Zhuang X, Cui Y, Gao C, Jiang L. Endocytic and autophagic pathways crosstalk in plants. CURRENT OPINION IN PLANT BIOLOGY 2015; 28:39-47. [PMID: 26453966 DOI: 10.1016/j.pbi.2015.08.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 07/25/2015] [Accepted: 08/30/2015] [Indexed: 05/19/2023]
Abstract
The vacuole is the central site for both storage and metabolism in plant cells and mediates multiple cellular events during plant development and growth. Cargo proteins are usually sequestered into membrane-bound organelles and delivered into the vacuole upon membrane fusion. Two major organelles are responsible for the recognition and transport of cargos targeted to the vacuole: the single-membrane multivesicular body (MVB) or prevacuolar compartment (PVC) and the double-membrane autophagosome. Here, we will highlight recent discoveries about MVB/PVC-mediated and autophagosome-mediated protein trafficking and degradation, and will pay special attention to a possible interplay between the endocytic and autophagic pathways in regulating vacuolar degradation in plants.
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Affiliation(s)
- Xiaohong Zhuang
- School of Life Sciences, Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Yong Cui
- School of Life Sciences, Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Caiji Gao
- School of Life Sciences, Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Liwen Jiang
- School of Life Sciences, Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China; CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, China.
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16
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Cvrčková F, Žárský V. Old AIMs of the exocyst: evidence for an ancestral association of exocyst subunits with autophagy-associated Atg8 proteins. PLANT SIGNALING & BEHAVIOR 2013; 8:e27099. [PMID: 24305598 PMCID: PMC4091244 DOI: 10.4161/psb.27099] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
In a recent addendum, Oren Tzfadia and Gad Galili (PSB 2014; 9:e26732) showed that several Arabidopsis exocyst subunits possess consensus Atg8-interacting motifs (AIMs), which may mediate their interaction with the autophagy-associated Atg8 protein, providing thus a mechanistic base for participation of exocyst (sub)complexes in autophagy. However, the bioinformatically identified AIMs are short peptide motifs that may occur by chance. We thus performed an exhaustive search in a large collection of plant exocyst-derived sequences from our previous bioinformatic study and found that AIMs are over-represented among exocyst subunits of all lineages examined, including moss and club moss, compared with a representative sample of the Arabidopsis proteome. This is consistent with the proposed exocyst AIMs being biologically meaningful and evolutionarily ancient. Moreover, among the numerous EXO70 paralogs, the monocot-specific EXO70F clade appears to be exempt from the general AIM enrichment, suggesting a modification of the autophagy connection in a subset of exocyst variants.
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