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Ni H, Rui Q, Xu Y, Zhu J, Gao F, Dang B, Li D, Gao R, Chen G. RACK1 upregulation induces neuroprotection by activating the IRE1-XBP1 signaling pathway following traumatic brain injury in rats. Exp Neurol 2018. [DOI: 10.1016/j.expneurol.2018.03.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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52
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Li M, Ji L, Jia Z, Yang X, Meng Q, Guo S. Constitutive expression of CaHSP22.5 enhances chilling tolerance in transgenic tobacco by promoting the activity of antioxidative enzymes. FUNCTIONAL PLANT BIOLOGY : FPB 2018; 45:575-585. [PMID: 32290996 DOI: 10.1071/fp17226] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 11/29/2017] [Indexed: 05/24/2023]
Abstract
Chilling stress limits the productivity and geographical distribution of many organisms throughout the world. In plants, the small heat shock proteins (sHSPs) belong to a group of proteins known as chaperones. The sweet pepper (Capsicum annuum L.) cDNA clone CaHSP22.5, which encodes an endoplasmic reticulum-located sHSP (ER-sHSP), was isolated and introduced into tobacco (Nicotiana tabacum L.) plants and Escherichia coli. The performance index and the maximal efficiency of PSII photochemistry (Fv/Fm) were higher and the accumulation of H2O2 and superoxide radicals (O2-) was lower in the transgenic lines than in the untransformed plants under chilling stress, which suggested that CaHSP22.5 accumulation enhanced photochemical activity and oxidation resistance. However, purified CaHSP22.5 could not directly reduce the contents of H2O2 and O2- in vitro. Additionally, heterologously expressed recombinant CaHSP22.5 enhanced E. coli viability under oxidative stress, helping to elucidate the cellular antioxidant function of CaHSP22.5 in vivo. At the same time, antioxidant enzyme activity was higher, which was consistent with the lower relative electrolyte conductivity and malondialdehyde contents of the transgenic lines compared with the wild-type. Furthermore, constitutive expression of CaHSP22.5 decreased the expression of other endoplasmic reticulum molecular chaperones, which indicated that the constitutive expression of ER-sHSP alleviated endoplasmic reticulum stress caused by chilling stress in plants. We hypothesise that CaHSP22.5 stabilises unfolded proteins as a chaperone and increases the activity of reactive oxygen species-scavenging enzymes to avoid oxidation damage under chilling stress, thereby suggesting that CaHSP22.5 could be useful for improving the tolerance of chilling-sensitive plant types.
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Affiliation(s)
- Meifang Li
- College of Life Science, Liaocheng University, Liaocheng 252000, China
| | - Lusha Ji
- College of Life Science, Liaocheng University, Liaocheng 252000, China
| | - Zefeng Jia
- College of Life Science, Liaocheng University, Liaocheng 252000, China
| | - Xinghong Yang
- State Key Laboratory of Crop Biology, Shandong Key Laboratory of Crop Biology, Shandong Agricultural University, Taian 271018, China
| | - Qingwei Meng
- State Key Laboratory of Crop Biology, Shandong Key Laboratory of Crop Biology, Shandong Agricultural University, Taian 271018, China
| | - Shangjing Guo
- College of Life Science, Liaocheng University, Liaocheng 252000, China
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53
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Yamaoka Y, Choi BY, Kim H, Shin S, Kim Y, Jang S, Song WY, Cho CH, Yoon HS, Kohno K, Lee Y. Identification and functional study of the endoplasmic reticulum stress sensor IRE1 in Chlamydomonas reinhardtii. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 94:91-104. [PMID: 29385296 DOI: 10.1111/tpj.13844] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2017] [Revised: 01/07/2018] [Accepted: 01/15/2018] [Indexed: 06/07/2023]
Abstract
In many eukaryotes, endoplasmic reticulum (ER) stress activates the unfolded protein response (UPR) via the transmembrane endoribonuclease IRE1 to maintain ER homeostasis. The ER stress response in microalgae has not been studied in detail. Here, we identified Chlamydomonas reinhardtii IRE1 (CrIRE1) and characterized two independent knock-down alleles of this gene. CrIRE1 is similar to IRE1s identified in budding yeast, plants, and humans, in terms of conserved domains, but differs in having the tandem zinc-finger domain at the C terminus. CrIRE1 was highly induced under ER stress conditions, and the expression of a chimeric protein consisting of the luminal N-terminal region of CrIRE1 fused to the cytosolic C-terminal region of yeast Ire1p rescued the yeast ∆ire1 mutant. Both allelic ire1 knock-down mutants ire1-1 and ire1-2 were much more sensitive than their parental strain CC-4533 to the ER stress inducers tunicamycin, dithiothreitol and brefeldin A. Treatment with a low concentration of tunicamycin resulted in growth arrest and cytolysis in ire1 mutants, but not in CC-4533 cells. Furthermore, in the mutants, ER stress marker gene expression was reduced, and reactive oxygen species (ROS) marker gene expression was increased. The survival of ire1 mutants treated with tunicamycin improved in the presence of the ROS scavenger glutathione, suggesting that ire1 mutants failed to maintain ROS levels under ER stress. Together, these results indicate that CrIRE1 functions as an important component of the ER stress response in Chlamydomonas, and suggest that the ER stress sensor IRE1 is highly conserved during the evolutionary history.
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Affiliation(s)
- Yasuyo Yamaoka
- Department of Life Science, Pohang University of Science and Technology, Pohang, 37673, Korea
| | - Bae Young Choi
- Department of Integrative Bioscience & Biotechnology, Pohang University of Science and Technology, Pohang, 37673, Korea
| | - Hanul Kim
- Department of Life Science, Pohang University of Science and Technology, Pohang, 37673, Korea
| | - Seungjun Shin
- Department of Integrative Bioscience & Biotechnology, Pohang University of Science and Technology, Pohang, 37673, Korea
| | - Yeongho Kim
- Department of Life Science, Pohang University of Science and Technology, Pohang, 37673, Korea
| | - Sunghoon Jang
- Department of Life Science, Pohang University of Science and Technology, Pohang, 37673, Korea
| | - Won-Yong Song
- Department of Life Science, Pohang University of Science and Technology, Pohang, 37673, Korea
| | - Chung H Cho
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Korea
| | - Hwan Su Yoon
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Korea
| | - Kenji Kohno
- Graduate School of Biological Sciences and Institute for Research Initiatives, Nara Institute of Science and Technology, Ikoma, Nara, 630-0192, Japan
| | - Youngsook Lee
- Department of Life Science, Pohang University of Science and Technology, Pohang, 37673, Korea
- Department of Integrative Bioscience & Biotechnology, Pohang University of Science and Technology, Pohang, 37673, Korea
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54
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Nawkar GM, Lee ES, Shelake RM, Park JH, Ryu SW, Kang CH, Lee SY. Activation of the Transducers of Unfolded Protein Response in Plants. FRONTIERS IN PLANT SCIENCE 2018; 9:214. [PMID: 29515614 DOI: 10.3389/fpls.2018.00214/full] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 02/05/2018] [Indexed: 05/24/2023]
Abstract
Maintenance of homeostasis of the endoplasmic reticulum (ER) ensures the balance between loading of nascent proteins and their secretion. Certain developmental conditions or environmental stressors affect protein folding causing ER stress. The resultant ER stress is mitigated by upregulating a set of stress-responsive genes in the nucleus modulating the mechanism of the unfolded protein response (UPR). In plants, the UPR is mediated by two major pathways; by the proteolytic processing of bZIP17/28 and by the IRE1-mediated splicing of bZIP60 mRNA. Recent studies have shown the involvement of plant-specific NAC transcription factors in UPR regulation. The molecular mechanisms activating plant-UPR transducers are only recently being unveiled. This review focuses on important structural features involved in the activation of the UPR transducers like bZIP17/28/60, IRE1, BAG7, and NAC017/062/089/103. Also, we discuss the activation of the UPR pathways, including BAG7-bZIP28 and IRE1-bZIP60, in detail, together with the NAC-TFs, which adds a new paradigm to the plant UPR.
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Affiliation(s)
- Ganesh M Nawkar
- Division of Applied Life Sciences (BK21 Plus) and Plant Molecular Biology and Biotechnology Research Center (PMBBRC), Gyeongsang National University, Jinju, South Korea
| | - Eun Seon Lee
- Division of Applied Life Sciences (BK21 Plus) and Plant Molecular Biology and Biotechnology Research Center (PMBBRC), Gyeongsang National University, Jinju, South Korea
| | - Rahul M Shelake
- Division of Applied Life Sciences (BK21 Plus) and Plant Molecular Biology and Biotechnology Research Center (PMBBRC), Gyeongsang National University, Jinju, South Korea
| | - Joung Hun Park
- Division of Applied Life Sciences (BK21 Plus) and Plant Molecular Biology and Biotechnology Research Center (PMBBRC), Gyeongsang National University, Jinju, South Korea
| | - Seoung Woo Ryu
- Division of Applied Life Sciences (BK21 Plus) and Plant Molecular Biology and Biotechnology Research Center (PMBBRC), Gyeongsang National University, Jinju, South Korea
| | - Chang Ho Kang
- Division of Applied Life Sciences (BK21 Plus) and Plant Molecular Biology and Biotechnology Research Center (PMBBRC), Gyeongsang National University, Jinju, South Korea
| | - Sang Yeol Lee
- Division of Applied Life Sciences (BK21 Plus) and Plant Molecular Biology and Biotechnology Research Center (PMBBRC), Gyeongsang National University, Jinju, South Korea
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55
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Nawkar GM, Lee ES, Shelake RM, Park JH, Ryu SW, Kang CH, Lee SY. Activation of the Transducers of Unfolded Protein Response in Plants. FRONTIERS IN PLANT SCIENCE 2018; 9:214. [PMID: 29515614 PMCID: PMC5826264 DOI: 10.3389/fpls.2018.00214] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 02/05/2018] [Indexed: 05/19/2023]
Abstract
Maintenance of homeostasis of the endoplasmic reticulum (ER) ensures the balance between loading of nascent proteins and their secretion. Certain developmental conditions or environmental stressors affect protein folding causing ER stress. The resultant ER stress is mitigated by upregulating a set of stress-responsive genes in the nucleus modulating the mechanism of the unfolded protein response (UPR). In plants, the UPR is mediated by two major pathways; by the proteolytic processing of bZIP17/28 and by the IRE1-mediated splicing of bZIP60 mRNA. Recent studies have shown the involvement of plant-specific NAC transcription factors in UPR regulation. The molecular mechanisms activating plant-UPR transducers are only recently being unveiled. This review focuses on important structural features involved in the activation of the UPR transducers like bZIP17/28/60, IRE1, BAG7, and NAC017/062/089/103. Also, we discuss the activation of the UPR pathways, including BAG7-bZIP28 and IRE1-bZIP60, in detail, together with the NAC-TFs, which adds a new paradigm to the plant UPR.
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56
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Lomin SN, Myakushina YA, Arkhipov DV, Leonova OG, Popenko VI, Schmülling T, Romanov GA. Studies of cytokinin receptor-phosphotransmitter interaction provide evidences for the initiation of cytokinin signalling in the endoplasmic reticulum. FUNCTIONAL PLANT BIOLOGY : FPB 2018; 45:192-202. [PMID: 32291033 DOI: 10.1071/fp16292] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2016] [Accepted: 01/11/2017] [Indexed: 05/06/2023]
Abstract
Cytokinin receptors were shown recently to be localised mainly to the endoplasmic reticulum (ER); however, the activity of ER-located receptors was not proven. We have therefore tested the functionality of ER-located Arabidopsis receptors. The first step of cytokinin signal transduction is the transfer of a phosphoryl group from the activated receptor to a phosphotransfer protein. To determine the subcellular localisation of receptor-phosphotransmitter interaction in planta, BiFC experiments were performed. Receptors ARABIDOPSIS HISTIDINE KINASE 2 (AHK2), AHK3 and AHK4 (CRE1) and phosphotransmitters ARABIDOPSIS HISTIDINE-CONTAINING PHOSPHOTRANSMITTER 1 (AHP1), AHP2 and AHP3 fused to split-eYFP were transiently expressed in Nicotiana benthamiana leaves. Receptor-phosphotransmitter pairs were shown to interact in every possible combination in a pattern reflecting the ER. Receptor dimers, an active form of the receptors, were also detected in the ER. According to BiFC and protease protection data, the catalytic part of AHK3 was located in the cytoplasm whereas the hormone binding module faced the ER lumen. This topology is consistent with receptor signalling from the ER membrane. Finally, the functionality of receptors in different membrane fractions was tested using an in vitro kinase assay visualising the phosphorylation of phosphotransfer proteins. The detected cytokinin-dependent phosphotransfer activity was confined mainly to the ER-enriched fraction. Collectively, our data demonstrate that ER-located cytokinin receptors are active in cytokinin signal transduction. Hence, intracellular cytokinins appear to play an essential role in cytokinin signalling. An updated model for the spatial organisation of cytokinin transport form activation, intracellular trafficking and signalling from the ER is proposed.
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Affiliation(s)
- Sergey N Lomin
- Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya str. 35, 127276 Moscow, Russia
| | - Yulia A Myakushina
- Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya str. 35, 127276 Moscow, Russia
| | - Dmitry V Arkhipov
- Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya str. 35, 127276 Moscow, Russia
| | - Olga G Leonova
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov str. 32, 119991 Moscow, Russia
| | - Vladimir I Popenko
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov str. 32, 119991 Moscow, Russia
| | - Thomas Schmülling
- Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences, Freie Universität Berlin, Albrecht-Thaer-Weg 6, D-14195 Berlin, Germany
| | - Georgy A Romanov
- Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya str. 35, 127276 Moscow, Russia
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57
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Mira MM, Huang S, Kapoor K, Hammond C, Hill RD, Stasolla C. Expression of Arabidopsis class 1 phytoglobin (AtPgb1) delays death and degradation of the root apical meristem during severe PEG-induced water deficit. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:5653-5668. [PMID: 29059380 PMCID: PMC5853930 DOI: 10.1093/jxb/erx371] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Maintenance of a functional root is fundamental to plant survival in response to some abiotic stresses, such as water deficit. In this study, we found that overexpression of Arabidopsis class 1 phytoglobin (AtPgb1) alleviated the growth retardation of polyethylene glycol (PEG)-induced water stress by reducing programmed cell death (PCD) associated with protein folding in the endoplasmic reticulum (ER). This was in contrast to PEG-stressed roots down-regulating AtPgb1 that exhibited extensive PCD and reduced expression of several attenuators of ER stress, including BAX Inhibitor-1 (BI-1). The death program experienced by the suppression of AtPgb1 in stressed roots was mediated by reactive oxygen species (ROS) and ethylene. Suppression of ROS synthesis or ethylene perception reduced PCD and partially restored root growth. The PEG-induced cessation of root growth was preceded by structural changes in the root apical meristem (RAM), including the loss of cell and tissue specification, possibly as a result of alterations in PIN1- and PIN4-mediated auxin accumulation at the root pole. These events were attenuated by the overexpression of AtPgb1 and aggravated when AtPgb1 was suppressed. Specifically, suppression of AtPgb1 compromised the functionality of the WOX5-expressing quiescent cells (QCs), leading to the early and premature differentiation of the adjacent columella stem cells and to a rapid reduction in meristem size. The expression and localization of other root domain markers, such as SCARECROW (SCR), which demarks the endodermis and QCs, and WEREWOLF (WER), which specifies the lateral root cap, were also most affected in PEG-treated roots with suppressed AtPgb1. Collectively, the results demonstrate that AtPgb1 exercises a protective role in roots exposed to lethal levels of PEG, and suggest a novel function of this gene in ensuring meristem functionality through the retention of cell fate specification.
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Affiliation(s)
- Mohamed M Mira
- Department of Botany, Faculty of Science, Tanta University, Tanta, Egypt
| | - Shuanglong Huang
- Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Karuna Kapoor
- Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Cassandra Hammond
- Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Robert D Hill
- Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Claudio Stasolla
- Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada
- Correspondence:
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58
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Angelos E, Ruberti C, Kim SJ, Brandizzi F. Maintaining the factory: the roles of the unfolded protein response in cellular homeostasis in plants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 90:671-682. [PMID: 27943485 PMCID: PMC5415411 DOI: 10.1111/tpj.13449] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 11/23/2016] [Accepted: 12/02/2016] [Indexed: 05/07/2023]
Abstract
Much like a factory, the endoplasmic reticulum (ER) assembles simple cellular building blocks into complex molecular machines known as proteins. In order to protect the delicate protein folding process and ensure the proper cellular delivery of protein products under environmental stresses, eukaryotes have evolved a set of signaling mechanisms known as the unfolded protein response (UPR) to increase the folding capacity of the ER. This process is particularly important in plants, because their sessile nature commands adaptation for survival rather than escape from stress. As such, plants make special use of the UPR, and evidence indicates that the master regulators and downstream effectors of the UPR have distinct roles in mediating cellular processes that affect organism growth and development as well as stress responses. In this review we outline recent developments in this field that support a strong relevance of the UPR to many areas of plant life.
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Affiliation(s)
- Evan Angelos
- MSU-DOE Plant Research Lab and Plant Biology Department, Michigan State University, East Lansing, MI 48824, USA
| | - Cristina Ruberti
- MSU-DOE Plant Research Lab and Plant Biology Department, Michigan State University, East Lansing, MI 48824, USA
| | - Sang-Jin Kim
- MSU-DOE Plant Research Lab and Plant Biology Department, Michigan State University, East Lansing, MI 48824, USA
- Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI 48824, USA
| | - Federica Brandizzi
- MSU-DOE Plant Research Lab and Plant Biology Department, Michigan State University, East Lansing, MI 48824, USA
- Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
- Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI 48824, USA
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59
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Liu JX, Howell SH. Managing the protein folding demands in the endoplasmic reticulum of plants. THE NEW PHYTOLOGIST 2016; 211:418-28. [PMID: 26990454 DOI: 10.1111/nph.13915] [Citation(s) in RCA: 134] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 01/25/2016] [Indexed: 05/18/2023]
Abstract
Endoplasmic reticulum (ER) stress occurs in plants during certain developmental stages or under adverse environmental conditions, as a result of the accumulation of unfolded or misfolded proteins in the ER. To minimize the accumulation of misfolded proteins in the ER, a protein quality control (PQC) system monitors protein folding and eliminates misfolded proteins through either ER-associated protein degradation (ERAD) or autophagy. ER stress elicits the unfolded protein response (UPR), which enhances the operation in plant cells of the ER protein folding machinery and the PQC system. The UPR also reduces protein folding demands in the ER by degrading mRNAs encoding secretory proteins. In plants subjected to severe or chronic stress, UPR promotes programmed cell death (PCD). Progress in the field in recent years has provided insights into the regulatory networks and signaling mechanisms of the ER stress responses in plants. In addition, novel physiological functions of the ER stress responses in plants for coordinating plant growth and development with changing environment have been recently revealed.
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Affiliation(s)
- Jian-Xiang Liu
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Stephen H Howell
- Department of Genetics, Development and Cell Biology, Plant Sciences Institute, Iowa State University, Ames, IA, 50011, USA
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60
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Wang A, Zhou X. ER Stress, UPR and Virus Infections in Plants. CURRENT RESEARCH TOPICS IN PLANT VIROLOGY 2016. [PMCID: PMC7123154 DOI: 10.1007/978-3-319-32919-2_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/17/2023]
Abstract
The endoplasmic reticulum (ER) endomembrane is a central site for protein synthesis. Perturbation of ER homeostasis can result in an accumulation of unfolded proteins within the ER lumen, causing ER stress and the unfolded protein response (UPR). In humans, ER stress and UPR are closely associated with a vast number of diseases, including viral diseases. In plants, two arms that govern the UPR signaling network have been described: one that contains two ER membrane–associated transcription factors (bZIP17 and bZIP28) and the other that encompasses a dual protein kinase (RNA-splicing factor IRE1) and its target RNA (bZIP60). Although early studies mainly focus on the essential roles of the UPR in abiotic stresses, the significance of UPR in plant diseases caused by virus infections has recently drawn much attention. This chapter summarizes the latest scenario of ER stress and UPR in virus-infected plant cells, highlights the emerging roles of the IRE1 pathway in virus infections, and outlines exciting future directions to spark more research interest in the UPR field in plants.
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Affiliation(s)
- Aiming Wang
- London Research and Development Centre, Agriculture and Agri-Food Canada, London, Ontario Canada
| | - Xueping Zhou
- State Key Laboratory for Biology of Plan, Chinese Academy of Agricultural Sciences, Beijing, China
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61
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Lu Y, Yin M, Wang X, Chen B, Yang X, Peng J, Zheng H, Zhao J, Lin L, Yu C, MacFarlane S, He J, Liu Y, Chen J, Dai L, Yan F. The unfolded protein response and programmed cell death are induced by expression of Garlic virus X p11 in Nicotiana benthamiana. J Gen Virol 2016; 97:1462-1468. [PMID: 27011387 DOI: 10.1099/jgv.0.000460] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Garlic virus X (GarVX) ORF3 encodes a p11 protein, which contributes to virus cell-to-cell movement and forms granules on the endoplasmic reticulum (ER) in Nicotiana benthamiana. Expression of p11 either from a binary vector, PVX or TMV induced ER stress and the unfolded protein response (UPR), as demonstrated by an increase in transcription of the ER luminal binding protein (BiP) and bZIP60 genes. UPR-related programmed cell death (PCD) was elicited by PVX : p11 or TMV : p11 in systemic infected leaves. Examination of p11 mutants with deletions of two transmembrane domains (TM) revealed that both were required for generating granules and for inducing necrosis. TRV-based VIGS was used to investigate the correlation between bZIP60 expression and p11-induced UPR-related PCD. Less necrosis was observed on local and systemic leaves of bZIP60 knockdown plants when infected with PVXp11, suggesting that bZIP60 plays an important role in the UPR-related PCD response to p11 in N. benthamiana.
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Affiliation(s)
- Yuwen Lu
- College of Plant Protection, Hunan Agricultural University, Changsha 410128, PR China
- State Key laboratory Breeding Base for Sustainable Control of Pest and Disease, Key Laboratory of Biotechnology in Plant Protection, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, PR China
| | - Mingyuan Yin
- Tibet Agricultural and Animal Husbandry College, Linzhi 860000, PR China
| | - Xiaodan Wang
- Virus-free Seedling Research Institute of Heilongjiang Academy of Agricultural Sciences, No. 368, Xuefu Road, Harbin 150086, PR China
| | - Binghua Chen
- State Key Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key Laboratory of Green Pesticide and Agricultural Bioengineering of Ministry of Education, Guizhou University, Guiyang 550025, PR China
| | - Xue Yang
- Department of Plant Protection, Shenyang Agriculture University, Shenyang 110161, PR China
| | - Jiejun Peng
- State Key laboratory Breeding Base for Sustainable Control of Pest and Disease, Key Laboratory of Biotechnology in Plant Protection, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, PR China
| | - Hongying Zheng
- State Key laboratory Breeding Base for Sustainable Control of Pest and Disease, Key Laboratory of Biotechnology in Plant Protection, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, PR China
| | - Jinping Zhao
- State Key laboratory Breeding Base for Sustainable Control of Pest and Disease, Key Laboratory of Biotechnology in Plant Protection, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, PR China
| | - Lin Lin
- State Key laboratory Breeding Base for Sustainable Control of Pest and Disease, Key Laboratory of Biotechnology in Plant Protection, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, PR China
| | - Chulang Yu
- State Key laboratory Breeding Base for Sustainable Control of Pest and Disease, Key Laboratory of Biotechnology in Plant Protection, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, PR China
| | - Stuart MacFarlane
- The James Hutton Institute, Cell and Molecular Sciences Group, Invergowrie, Dundee DD2 5DA, UK
| | - Jianqing He
- Tibet Agricultural and Animal Husbandry College, Linzhi 860000, PR China
| | - Yong Liu
- Institute of Plant Protection, Hunan Academy of Agricultural Sciences, Changsha, PR China
| | - Jianping Chen
- State Key laboratory Breeding Base for Sustainable Control of Pest and Disease, Key Laboratory of Biotechnology in Plant Protection, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, PR China
| | - Liangying Dai
- College of Plant Protection, Hunan Agricultural University, Changsha 410128, PR China
| | - Fei Yan
- State Key laboratory Breeding Base for Sustainable Control of Pest and Disease, Key Laboratory of Biotechnology in Plant Protection, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, PR China
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62
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Fragkostefanakis S, Mesihovic A, Hu Y, Schleiff E. Unfolded protein response in pollen development and heat stress tolerance. PLANT REPRODUCTION 2016; 29:81-91. [PMID: 27022919 DOI: 10.1007/s00497-016-0276-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2015] [Accepted: 02/10/2016] [Indexed: 05/18/2023]
Abstract
Importance of the UPR for pollen. Pollen is particularly sensitive to environmental conditions that disturb protein homeostasis, such as higher temperatures. Their survival is dependent on subcellular stress response systems, one of which maintains protein homeostasis in the endoplasmic reticulum (ER). Disturbance of ER proteostasis due to stress leads to the activation of the unfolded protein response (UPR) that mitigates stress damage mainly by increasing ER-folding capacity and reducing folding demands. The UPR is controlled by ER membrane-associated transcription factors and an RNA splicing factor. They are important components of abiotic stress responses including general heat stress response and thermotolerance. In addition to responding to environmental stresses, the UPR is implicated in developmental processes required for successful male gametophyte development and fertilization. Consequently, defects in the UPR can lead to pollen abortion and male sterility. Several UPR components are involved in the elaboration of the ER network, which is required for pollen germination and polar tube growth. Transcriptome and proteome analyses have shown that components of the ER-folding machinery and the UPR are upregulated at specific stages of pollen development supporting elevated demands for secretion. Furthermore, genetic studies have revealed that knockout mutants of UPR genes are defective in producing viable or competitive pollen. In this review, we discuss recent findings regarding the importance of the UPR for both pollen development and stress response.
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Affiliation(s)
- Sotirios Fragkostefanakis
- Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, 60438, Frankfurt am Main, Germany.
| | - Anida Mesihovic
- Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, 60438, Frankfurt am Main, Germany
| | - Yangjie Hu
- Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, 60438, Frankfurt am Main, Germany
| | - Enrico Schleiff
- Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, 60438, Frankfurt am Main, Germany.
- Cluster of Excellence Frankfurt, Goethe University, 60438, Frankfurt am Main, Germany.
- Buchmann Institute for Molecular Life Sciences (BMLS), Goethe University, 60438, Frankfurt am Main, Germany.
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63
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Hayashi S, Wakasa Y, Ozawa K, Takaiwa F. Characterization of IRE1 ribonuclease-mediated mRNA decay in plants using transient expression analyses in rice protoplasts. THE NEW PHYTOLOGIST 2016; 210:1259-1268. [PMID: 26831622 DOI: 10.1111/nph.13845] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 12/05/2015] [Indexed: 06/05/2023]
Abstract
In some eukaryotes, endoplasmic reticulum (ER) stress induces regulated inositol-requiring enzyme 1 (IRE1)-dependent decay (RIDD) of mRNAs. Recently, the expression levels of the mRNAs encoding some secretory proteins were reported to be downregulated by RIDD in the vegetative tissues of plants. However, the characteristics of plant RIDD have been insufficiently investigated due to difficulty of in planta analyses. Here, the RIDD susceptibilities of various mRNAs that are difficult to analyze in planta were examined using transient expression analyses of rice protoplasts. In this system, the mRNAs encoding three rice seed storage proteins (SSPs) - namely α-globulin, 16-kDa prolamin and 10-kDa prolamin - were downregulated in response to ER stress. The rapid ER stress-induced degradation of these mRNAs was repressed in cells in which the ribonuclease activity of IRE1 was specifically abolished by genome editing, suggesting that the mRNAs encoding certain SSPs are strong targets of RIDD. Furthermore, we investigated whether these RIDD targets are substrates of the IRE1 ribonuclease using a recombinant IRE1 protein, and identified candidate IRE1-mediated cleavage sites. Overall, the results demonstrate the existence of a post-transcriptional mechanism of regulation of SSPs, and illustrate the basic and multifaceted characteristics of RIDD in higher plants.
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Affiliation(s)
- Shimpei Hayashi
- Genetically Modified Organism Research Center, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki, 305-8602, Japan
| | - Yuhya Wakasa
- Genetically Modified Organism Research Center, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki, 305-8602, Japan
| | - Kenjirou Ozawa
- Genetically Modified Organism Research Center, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki, 305-8602, Japan
| | - Fumio Takaiwa
- Genetically Modified Organism Research Center, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki, 305-8602, Japan
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64
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Wan S, Jiang L. Endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) in plants. PROTOPLASMA 2016; 253:753-764. [PMID: 26060134 DOI: 10.1007/s00709-015-0842-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 05/30/2015] [Indexed: 05/03/2023]
Abstract
Being a major factory for protein synthesis, assembly, and export, the endoplasmic reticulum (ER) has a precise and robust ER quality control (ERQC) system monitoring its product line. However, when organisms are subjected to environmental stress, whether biotic or abiotic, the levels of misfolded proteins may overwhelm the ERQC system, tilting the balance between the capacity of and demand for ER quality control and resulting in a scenario termed ER stress. Intense or prolonged ER stress may cause damage to the ER as well as to other organelles, or even lead to cell death in extreme cases. To avoid such serious consequences, cells activate self-rescue programs to restore protein homeostasis in the ER, either through the enhancement of protein-folding and degradation competence or by alleviating the demands for such reactions. These are collectively called the unfolded protein response (UPR). Long investigated in mammalian cells and yeasts, the UPR is also of great interest to plant scientists. Among the three branches of UPR discovered in mammals, two have been studied in plants with plant homologs existing of the ER-membrane-associated activating transcription factor 6 (ATF6) and inositol-requiring enzyme 1 (IRE1). This review discusses the molecular mechanisms of these two types of UPR in plants, as well as the consequences of insufficient UPR, with a focus on experiments using model plants.
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Affiliation(s)
- Shucen Wan
- Molecular Biotechnology Program, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
| | - Liwen Jiang
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
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65
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miRNA863-3p sequentially targets negative immune regulator ARLPKs and positive regulator SERRATE upon bacterial infection. Nat Commun 2016; 7:11324. [PMID: 27108563 PMCID: PMC4848489 DOI: 10.1038/ncomms11324] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 03/15/2016] [Indexed: 12/21/2022] Open
Abstract
Plant small RNAs play important roles in gene regulation during pathogen infection. Here we show that miR863-3p is induced by the bacterial pathogen Pseudomonas syringae carrying various effectors. Early during infection, miR863-3p silences two negative regulators of plant defence, atypical receptor-like pseudokinase1 (ARLPK1) and ARLPK2, both lacking extracellular domains and kinase activity, through mRNA degradation to promote immunity. ARLPK1 associates with, and may function through another negative immune regulator ARLPK1-interacting receptor-like kinase 1 (AKIK1), an active kinase with an extracellular domain. Later during infection, miR863-3p silences SERRATE, which is essential for miRNA accumulation and positively regulates defence, through translational inhibition. This results in decreased miR863-3p levels, thus forming a negative feedback loop to attenuate immune responses after successful defence. This is an example of a miRNA that sequentially targets both negative and positive regulators of immunity through two modes of action to fine-tune the timing and amplitude of defence responses. Small RNA plays an important role in regulating the plant defence against bacterial pathogens. Here the authors propose that miR863-3p acts to fine-tune the timing of defence responses by sequentially silencing negative and positive regulators of the plant immune response.
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66
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Yang X, Srivastava R, Howell SH, Bassham DC. Activation of autophagy by unfolded proteins during endoplasmic reticulum stress. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2016; 85:83-95. [PMID: 26616142 DOI: 10.1111/tpj.13091] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 11/18/2015] [Accepted: 11/20/2015] [Indexed: 05/20/2023]
Abstract
Endoplasmic reticulum stress is defined as the accumulation of unfolded proteins in the endoplasmic reticulum, and is caused by conditions such as heat or agents that cause endoplasmic reticulum stress, including tunicamycin and dithiothreitol. Autophagy, a major pathway for degradation of macromolecules in the vacuole, is activated by these stress agents in a manner dependent on inositol-requiring enzyme 1b (IRE1b), and delivers endoplasmic reticulum fragments to the vacuole for degradation. In this study, we examined the mechanism for activation of autophagy during endoplasmic reticulum stress in Arabidopsis thaliana. The chemical chaperones sodium 4-phenylbutyrate and tauroursodeoxycholic acid were found to reduce tunicamycin- or dithiothreitol-induced autophagy, but not autophagy caused by unrelated stresses. Similarly, over-expression of BINDING IMMUNOGLOBULIN PROTEIN (BIP), encoding a heat shock protein 70 (HSP70) molecular chaperone, reduced autophagy. Autophagy activated by heat stress was also found to be partially dependent on IRE1b and to be inhibited by sodium 4-phenylbutyrate, suggesting that heat-induced autophagy is due to accumulation of unfolded proteins in the endoplasmic reticulum. Expression in Arabidopsis of the misfolded protein mimics zeolin or a mutated form of carboxypeptidase Y (CPY*) also induced autophagy in an IRE1b-dependent manner. Moreover, zeolin and CPY* partially co-localized with the autophagic body marker GFP-ATG8e, indicating delivery to the vacuole by autophagy. We conclude that accumulation of unfolded proteins in the endoplasmic reticulum is a trigger for autophagy under conditions that cause endoplasmic reticulum stress.
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Affiliation(s)
- Xiaochen Yang
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA
- Interdepartmental Plant Biology Program, Iowa State University, Ames, IA, 50011, USA
| | - Renu Srivastava
- Plant Sciences Institute, Iowa State University, Ames, IA, 50011, USA
| | - Stephen H Howell
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA
- Interdepartmental Plant Biology Program, Iowa State University, Ames, IA, 50011, USA
- Plant Sciences Institute, Iowa State University, Ames, IA, 50011, USA
| | - Diane C Bassham
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA
- Interdepartmental Plant Biology Program, Iowa State University, Ames, IA, 50011, USA
- Plant Sciences Institute, Iowa State University, Ames, IA, 50011, USA
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67
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Hossain MA, Henríquez-Valencia C, Gómez-Páez M, Medina J, Orellana A, Vicente-Carbajosa J, Zouhar J. Identification of Novel Components of the Unfolded Protein Response in Arabidopsis. FRONTIERS IN PLANT SCIENCE 2016; 7:650. [PMID: 27242851 PMCID: PMC4864164 DOI: 10.3389/fpls.2016.00650] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Accepted: 04/28/2016] [Indexed: 05/22/2023]
Abstract
Unfavorable environmental and developmental conditions may cause disturbances in protein folding in the endoplasmic reticulum (ER) that are recognized and counteracted by components of the Unfolded Protein Response (UPR) signaling pathways. The early cellular responses include transcriptional changes to increase the folding and processing capacity of the ER. In this study, we systematically screened a collection of inducible transgenic Arabidopsis plants expressing a library of transcription factors for resistance toward UPR-inducing chemicals. We identified 23 candidate genes that may function as novel regulators of the UPR and of which only three genes (bZIP10, TBF1, and NF-YB3) were previously associated with the UPR. The putative role of identified candidate genes in the UPR signaling is supported by favorable expression patterns in both developmental and stress transcriptional analyses. We demonstrated that WRKY75 is a genuine regulator of the ER-stress cellular responses as its expression was found to be directly responding to ER stress-inducing chemicals. In addition, transgenic Arabidopsis plants expressing WRKY75 showed resistance toward salt stress, connecting abiotic and ER-stress responses.
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Affiliation(s)
- Md. Amir Hossain
- Centro de Biotecnología y Genómica de Plantas UPM-INIA, Universidad Politécnica de MadridMadrid, Spain
| | - Carlos Henríquez-Valencia
- Centro de Biotecnología Vegetal, FONDAP Center for Genome Regulation, Facultad de Ciencias Biológicas, Universidad Andrés BelloSantiago, Chile
| | - Marcela Gómez-Páez
- Centro de Biotecnología y Genómica de Plantas UPM-INIA, Universidad Politécnica de MadridMadrid, Spain
| | - Joaquín Medina
- Centro de Biotecnología y Genómica de Plantas UPM-INIA, Universidad Politécnica de MadridMadrid, Spain
| | - Ariel Orellana
- Centro de Biotecnología Vegetal, FONDAP Center for Genome Regulation, Facultad de Ciencias Biológicas, Universidad Andrés BelloSantiago, Chile
| | - Jesús Vicente-Carbajosa
- Centro de Biotecnología y Genómica de Plantas UPM-INIA, Universidad Politécnica de MadridMadrid, Spain
| | - Jan Zouhar
- Centro de Biotecnología y Genómica de Plantas UPM-INIA, Universidad Politécnica de MadridMadrid, Spain
- *Correspondence: Jan Zouhar
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68
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Kørner CJ, Du X, Vollmer ME, Pajerowska-Mukhtar KM. Endoplasmic Reticulum Stress Signaling in Plant Immunity--At the Crossroad of Life and Death. Int J Mol Sci 2015; 16:26582-98. [PMID: 26556351 PMCID: PMC4661823 DOI: 10.3390/ijms161125964] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 10/22/2015] [Accepted: 10/23/2015] [Indexed: 01/01/2023] Open
Abstract
Rapid and complex immune responses are induced in plants upon pathogen recognition. One form of plant defense response is a programmed burst in transcription and translation of pathogenesis-related proteins, of which many rely on ER processing. Interestingly, several ER stress marker genes are up-regulated during early stages of immune responses, suggesting that enhanced ER capacity is needed for immunity. Eukaryotic cells respond to ER stress through conserved signaling networks initiated by specific ER stress sensors tethered to the ER membrane. Depending on the nature of ER stress the cell prioritizes either survival or initiates programmed cell death (PCD). At present two plant ER stress sensors, bZIP28 and IRE1, have been described. Both sensor proteins are involved in ER stress-induced signaling, but only IRE1 has been additionally linked to immunity. A second branch of immune responses relies on PCD. In mammals, ER stress sensors are involved in activation of PCD, but it is unclear if plant ER stress sensors play a role in PCD. Nevertheless, some ER resident proteins have been linked to pathogen-induced cell death in plants. In this review, we will discuss the current understanding of plant ER stress signaling and its cross-talk with immune signaling.
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Affiliation(s)
- Camilla J Kørner
- Department of Biology, University of Alabama at Birmingham, 1300 University Blvd., Birmingham, AL 35294, USA.
| | - Xinran Du
- Department of Biology, University of Alabama at Birmingham, 1300 University Blvd., Birmingham, AL 35294, USA.
| | - Marie E Vollmer
- Department of Biology, University of Alabama at Birmingham, 1300 University Blvd., Birmingham, AL 35294, USA.
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69
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Ruberti C, Kim SJ, Stefano G, Brandizzi F. Unfolded protein response in plants: one master, many questions. CURRENT OPINION IN PLANT BIOLOGY 2015; 27:59-66. [PMID: 26149756 PMCID: PMC4618186 DOI: 10.1016/j.pbi.2015.05.016] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 05/13/2015] [Accepted: 05/15/2015] [Indexed: 05/02/2023]
Abstract
To overcome endoplasmic reticulum (ER) stress, ER-localized stress sensors actuate distinct downstream organelle-nucleus signaling pathways to invoke a cytoprotective response, known as the unfolded protein response (UPR). Compared to yeast and metazoans, plant UPR studies are more recent but nevertheless fascinating. Here we discuss recent discoveries in plant UPR, highlight conserved and unique features of the plant UPR as well as critical yet-open questions whose answers will likely make significant contributions to the understanding plant ER stress management.
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Affiliation(s)
- Cristina Ruberti
- Plant Research Laboratory, Department of Energy-Michigan State University, East Lansing, MI, USA; Department of Plant Biology, Michigan State University, East Lansing, MI, USA
| | - Sang-Jin Kim
- Plant Research Laboratory, Department of Energy-Michigan State University, East Lansing, MI, USA; Department of Plant Biology, Michigan State University, East Lansing, MI, USA
| | - Giovanni Stefano
- Plant Research Laboratory, Department of Energy-Michigan State University, East Lansing, MI, USA; Department of Plant Biology, Michigan State University, East Lansing, MI, USA
| | - Federica Brandizzi
- Plant Research Laboratory, Department of Energy-Michigan State University, East Lansing, MI, USA; Department of Plant Biology, Michigan State University, East Lansing, MI, USA.
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70
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Hayashi S, Takaiwa F. Visualization of endoplasmic reticulum stressed cells for forward genetic studies in plants. JOURNAL OF PLANT PHYSIOLOGY 2015; 180:61-66. [PMID: 25889874 DOI: 10.1016/j.jplph.2015.03.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 03/13/2015] [Accepted: 03/13/2015] [Indexed: 06/04/2023]
Abstract
In eukaryotes, various cellular events are attended by a risk of triggering stress in the endoplasmic reticulum (ER). Such risks are assumed to be minimized by sophisticated regulation systems, but the nature of these systems remains largely unknown in plants. Here, transgenic Arabidopsis plants, intended for use in forward genetic studies of plant ER stress, are described. AtBiP3 promoter activity clearly reflected the effects of inducers of ER stress, such as tunicamycin, dithiothreitol, and salicylic acid. Thus transgenic plants, containing the AtBiP3 promoter coupled to a fluorescent protein-encoding gene, were generated to enable visual detection of cells experiencing ER stress in living plants. Mutagenization of these transgenic plants produced seedlings which exhibited altered fluorescence patterns. Constitutive fluorescence was observed in a number of independent lines, suggesting the plant genome includes many genes whose mutation results in ER stress. Some mutants showed strong fluorescence with different tissue specificity, implying potential ER stresses in individual cellular events. These results indicate that forward genetic approaches will provide useful information in the understanding of ER stress.
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Affiliation(s)
- Shimpei Hayashi
- Genetically Modified Organism Research Center, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki 305-8602, Japan.
| | - Fumio Takaiwa
- Genetically Modified Organism Research Center, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki 305-8602, Japan.
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71
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McCormack ME, Liu X, Jordan MR, Pajerowska-Mukhtar KM. An improved high-throughput screening assay for tunicamycin sensitivity in Arabidopsis seedlings. FRONTIERS IN PLANT SCIENCE 2015; 6:663. [PMID: 26441998 PMCID: PMC4562274 DOI: 10.3389/fpls.2015.00663] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 08/12/2015] [Indexed: 05/20/2023]
Abstract
Tunicamycin (Tm) sensitivity assays are a useful method for studies of endoplasmic reticulum stress and the unfolded protein response in eukaryotic cells. While Tm sensitivity and Tm recovery assays have been previously described, these existing methods are time-consuming, labor intensive, and subjected to mechanical wounding. This study shows an improved method of testing Tm sensitivity in Arabidopsis using liquid Murashige and Skoog medium versus the traditional solid agar plates. Liquid medium bypasses the physical manipulation of seedlings, thereby eliminating the risk of potential mechanical damage and additional unwanted stress to seedlings. Seedlings were subjected to comparative treatments with various concentrations of Tm on both solid and liquid media and allowed to recover. Determination of fresh weight, chlorophyll contents analysis and qRT-PCR results confirm the efficacy of using liquid medium to perform quantitative Tm stress assays.
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Affiliation(s)
| | | | | | - Karolina M. Pajerowska-Mukhtar
- *Correspondence: Karolina M. Pajerowska-Mukhtar, Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Campbell Hall 371, Birmingham, AL 35294, USA,
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72
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Fu XL, Gao DS. Endoplasmic reticulum proteins quality control and the unfolded protein response: the regulative mechanism of organisms against stress injuries. Biofactors 2014; 40:569-85. [PMID: 25530003 DOI: 10.1002/biof.1194] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 11/25/2014] [Indexed: 12/21/2022]
Abstract
The endoplasmic reticulum is the cellular compartment in which secretory proteins are synthesized and folded. Perturbations of endoplasmic reticulum homeostasis lead to the accumulation of unfolded proteins. The activation of the unfolded protein response during endoplasmic reticulum stress transmits information about the status of protein folding to the cytosol and nucleus. The unfolded protein response leads to the upregulation of genes encoding endoplasmic reticulum chaperones, attenuation of translation, and initiation of the endoplasmic reticulum quality control system to restore endoplasmic reticulum homeostasis. When the unfolded protein response is insufficient to rebuild the steady state in endoplasmic reticulum, the programmed cell death or apoptosis would be initiated, by triggering cell injuries, even to cell death through apoptosis signals. In this review, we briefly outline research on the chaperones and foldases conserved in eukaryotes and plants, and describe the general principles and mechanisms of the endoplasmic reticulum quality control and the unfolded protein response. We describe the current models for the molecular mechanism of the unfolded protein response in plants, and emphasize the role of inositol requiring enzyme-1-dependent network in the unfolded protein response. Finally, we give a general overview of the directions for future research on the unfolded protein response in plants and its role in the response to environmental stresses.
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Affiliation(s)
- Xi Ling Fu
- Division of National Research Center for Apple Engineering and Technology, Shandong Agricultural University, Tai'an, Shandong, China; Division of State Key Laboratory of Crop Biology, Shandong Agricultural University, Tai'an, Shandong, China; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, China
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73
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Nagashima Y, Iwata Y, Ashida M, Mishiba KI, Koizumi N. Exogenous Salicylic Acid Activates Two Signaling Arms of the Unfolded Protein Response in Arabidopsis. ACTA ACUST UNITED AC 2014; 55:1772-8. [DOI: 10.1093/pcp/pcu108] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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74
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Williams B, Verchot J, Dickman MB. When supply does not meet demand-ER stress and plant programmed cell death. FRONTIERS IN PLANT SCIENCE 2014; 5:211. [PMID: 24926295 DOI: 10.3389/fpls.2014.00211/abstract] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Accepted: 04/29/2014] [Indexed: 05/24/2023]
Abstract
The endoplasmic reticulum (ER) is the central organelle in the eukaryotic secretory pathway. The ER functions in protein synthesis and maturation and is crucial for proper maintenance of cellular homeostasis and adaptation to adverse environments. Acting as a cellular sentinel, the ER is exquisitely sensitive to changing environments principally via the ER quality control machinery. When perturbed, ER-stress triggers a tightly regulated and highly conserved, signal transduction pathway known as the unfolded protein response (UPR) that prevents the dangerous accumulation of unfolded/misfolded proteins. In situations where excessive UPR activity surpasses threshold levels, cells deteriorate and eventually trigger programmed cell death (PCD) as a way for the organism to cope with dysfunctional or toxic signals. The programmed cell death that results from excessive ER stress in mammalian systems contributes to several important diseases including hypoxia, neurodegeneration, and diabetes. Importantly, hallmark features and markers of cell death that are associated with ER stress in mammals are also found in plants. In particular, there is a common, conserved set of chaperones that modulate ER cell death signaling. Here we review the elements of plant cell death responses to ER stress and note that an increasing number of plant-pathogen interactions are being identified in which the host ER is targeted by plant pathogens to establish compatibility.
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Affiliation(s)
- Brett Williams
- Centre for Tropical Crops and Biocommodities, Queensland University of Technology Brisbane, QLD, Australia
| | - Jeanmarie Verchot
- Department of Entomology and Plant Pathology, Oklahoma State University Stillwater, OK, USA
| | - Martin B Dickman
- Department of Plant Pathology and Microbiology, Institute for Plant Genomics and Biotechnology, Texas A&M University College Station, TX, USA
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75
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Lai YS, Stefano G, Brandizzi F. ER stress signaling requires RHD3, a functionally conserved ER-shaping GTPase. J Cell Sci 2014; 127:3227-32. [PMID: 24876222 DOI: 10.1242/jcs.147447] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Whether structure and function are correlated features of organelles is a fundamental question in cell biology. Here, we have assessed the ability of Arabidopsis mutants with a defective endoplasmic reticulum (ER) structure to invoke the unfolded protein response (UPR), an essential ER signaling pathway. Through molecular and genetic approaches, we show that loss of the ER-shaping GTPase Root Hair Defective 3 (RHD3) specifically disrupts the UPR by interfering with the mRNA splicing function of the master regulator IRE1. These findings establish a new role for RHD3 in the ER and support specificity of the effects of ER-shaping mutations on ER function.
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Affiliation(s)
- Ya-Shiuan Lai
- MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI 48824, USA Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Giovanni Stefano
- MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI 48824, USA Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Federica Brandizzi
- MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI 48824, USA Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
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76
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Coelho DS, Domingos PM. Physiological roles of regulated Ire1 dependent decay. Front Genet 2014; 5:76. [PMID: 24795742 PMCID: PMC3997004 DOI: 10.3389/fgene.2014.00076] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Accepted: 03/24/2014] [Indexed: 12/17/2022] Open
Abstract
Inositol-requiring enzyme 1 (Ire1) is an important transducer of the unfolded protein response (UPR) that is activated by the accumulation of misfolded proteins in the endoplamic reticulum (ER stress). Activated Ire1 mediates the splicing of an intron from the mRNA of Xbp1, causing a frame-shift during translation and introducing a new carboxyl domain in the Xbp1 protein, which only then becomes a fully functional transcription factor. Studies using cell culture systems demonstrated that Ire1 also promotes the degradation of mRNAs encoding mostly ER-targeted proteins, to reduce the load of incoming ER “client” proteins during ER stress. This process was called RIDD (regulated Ire1-dependent decay), but its physiological significance remained poorly characterized beyond cell culture systems. Here we review several recent studies that have highlighted the physiological roles of RIDD in specific biological paradigms, such as photoreceptor differentiation in Drosophila or mammalian liver and endocrine pancreas function. These studies demonstrate the importance of RIDD in tissues undergoing intense secretory function and highlight the physiologic role of RIDD during UPR activation in cells and organisms.
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Affiliation(s)
- Dina S Coelho
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa Oeiras, Portugal
| | - Pedro M Domingos
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa Oeiras, Portugal
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77
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Seo PJ. Recent advances in plant membrane-bound transcription factor research: emphasis on intracellular movement. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2014; 56:334-342. [PMID: 24299191 DOI: 10.1111/jipb.12139] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 11/25/2013] [Indexed: 06/02/2023]
Abstract
Transcription factors constitute numerous signal transduction networks and play a central role in gene expression regulation. Recent studies have shown that a limited portion of transcription factors are anchored in the cellular membrane, storing as dormant forms. Upon exposure to environmental and developmental cues, these transcription factors are released from the membrane and translocated to the nucleus, where they regulate associated target genes. As this process skips both transcriptional and translational regulations, it guarantees prompt response to external and internal signals. Membrane-bound transcription factors (MTFs) undergo several unique steps that are not involved in the action of canonical nuclear transcription factors: proteolytic processing and intracellular movement. Recently, alternative splicing has also emerged as a mechanism to liberate MTFs from the cellular membranes, establishing an additional activation scheme independent of proteolytic processing. Multiple layers of MTF regulation add complexity to transcriptional regulatory scheme and ensure elaborate action of MTFs. In this review, we provide an overview of recent findings on MTFs in plants and highlight the molecular mechanisms underlying MTF liberation from cellular membranes with an emphasis on intracellular movement.
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Affiliation(s)
- Pil Joon Seo
- Department of Bioactive Material Sciences, Chonbuk National University, Jeonju, 561-756, Korea; Research Center of Bioactive Materials, Chonbuk National University, Jeonju, 561-756, Korea; Department of Chemistry and Research Institute of Physics and Chemistry, Chonbuk National University, Jeonju, 561-756, Korea
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Maurel M, Chevet E, Tavernier J, Gerlo S. Getting RIDD of RNA: IRE1 in cell fate regulation. Trends Biochem Sci 2014; 39:245-54. [PMID: 24657016 DOI: 10.1016/j.tibs.2014.02.008] [Citation(s) in RCA: 428] [Impact Index Per Article: 42.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 02/20/2014] [Accepted: 02/21/2014] [Indexed: 12/12/2022]
Abstract
Inositol-requiring enzyme 1 (IRE1) is the most conserved transducer of the unfolded protein response (UPR), a homeostatic response that preserves proteostasis. Intriguingly, via its endoribonuclease activity, IRE1 produces either adaptive or death signals. This occurs through both unconventional splicing of XBP1 mRNA and regulated IRE1-dependent decay of mRNA (RIDD). Whereas XBP1 mRNA splicing is cytoprotective in response to endoplasmic reticulum (ER) stress, RIDD has revealed many unexpected features. For instance, RIDD cleaves RNA at an XBP1-like consensus site but with an activity divergent from XBP1 mRNA splicing and can either preserve ER homeostasis or induce cell death. Here we review recent findings on RIDD and propose a model of how IRE1 RNase activity might control cell fate decisions.
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Affiliation(s)
- M Maurel
- Department of Medical Protein Research, VIB, Ghent, Belgium; Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium.
| | - E Chevet
- INSERM U1053, Université Bordeaux Segalen, 33000 Bordeaux, France; Centre Régional de Lutte Contre le Cancer Eugène Marquis, 35000 Rennes, France
| | - J Tavernier
- Department of Medical Protein Research, VIB, Ghent, Belgium; Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
| | - S Gerlo
- Department of Medical Protein Research, VIB, Ghent, Belgium; Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium.
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79
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Guillemette T, Calmes B, Simoneau P. Impact of the UPR on the virulence of the plant fungal pathogen A. brassicicola. Virulence 2014; 5:357-64. [PMID: 24189567 PMCID: PMC3956514 DOI: 10.4161/viru.26772] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2013] [Revised: 10/10/2013] [Accepted: 10/10/2013] [Indexed: 11/19/2022] Open
Abstract
The fungal genus Alternaria contains many destructive plant pathogens, including Alternaria brassicicola, which causes black spot disease on a wide range of Brassicaceae plants and which is routinely used as a model necrotrophic pathogen in studies with Arabidopsis thaliana. During host infection, many fungal proteins that are critical for disease progression are processed in the endoplasmic reticulum (ER)/Golgi system and secreted in planta. The unfolded protein response (UPR) is an essential part of ER protein quality control that ensures efficient maturation of secreted and membrane-bound proteins in eukaryotes. This review highlights the importance of the UPR signaling pathway with respect to the ability of A. brassicicola to efficiently accomplish key steps of its pathogenic life cycle. Understanding the pathogenicity mechanisms that fungi uses during infection is crucial for the development of new antifungal therapies. Therefore the UPR pathway has emerged as a promising drug target for plant disease control.
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Affiliation(s)
- Thomas Guillemette
- Université d’Angers; UMR 1345 IRHS; SFR QUASAV; Angers, France
- INRA; UMR 1345 IRHS; Angers, France
- Agrocampus-Ouest; UMR 1345 IRHS; Angers, France
| | - Benoit Calmes
- Université d’Angers; UMR 1345 IRHS; SFR QUASAV; Angers, France
- INRA; UMR 1345 IRHS; Angers, France
- Agrocampus-Ouest; UMR 1345 IRHS; Angers, France
| | - Philippe Simoneau
- Université d’Angers; UMR 1345 IRHS; SFR QUASAV; Angers, France
- INRA; UMR 1345 IRHS; Angers, France
- Agrocampus-Ouest; UMR 1345 IRHS; Angers, France
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80
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Carvalho HH, Brustolini OJB, Pimenta MR, Mendes GC, Gouveia BC, Silva PA, Silva JCF, Mota CS, Soares-Ramos JRL, Fontes EPB. The molecular chaperone binding protein BiP prevents leaf dehydration-induced cellular homeostasis disruption. PLoS One 2014; 9:e86661. [PMID: 24489761 PMCID: PMC3906070 DOI: 10.1371/journal.pone.0086661] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 12/12/2013] [Indexed: 11/18/2022] Open
Abstract
BiP overexpression improves leaf water relations during droughts and delays drought-induced leaf senescence. However, whether BiP controls cellular homeostasis under drought conditions or simply delays dehydration-induced leaf senescence as the primary cause for water stress tolerance remains to be determined. To address this issue, we examined the drought-induced transcriptomes of BiP-overexpressing lines and wild-type (WT) lines under similar leaf water potential (ψw) values. In the WT leaves, a ψw reduction of -1.0 resulted in 1339 up-regulated and 2710 down-regulated genes; in the BiP-overexpressing line 35S::BiP-4, only 334 and 420 genes were induced and repressed, respectively, at a similar leaf ψw = -1.0 MPa. This level of leaf dehydration was low enough to induce a repertory of typical drought-responsive genes in WT leaves but not in 35S::BiP-4 dehydrated leaves. The responders included hormone-related genes, functional and regulatory genes involved in drought protection and senescence-associated genes. The number of differentially expressed genes in the 35S::BiP-4 line approached the wild type number at a leaf ψw = -1.6 MPa. However, N-rich protein (NRP)- mediated cell death signaling genes and unfolded protein response (UPR) genes were induced to a much lower extent in the 35S::BiP-4 line than in the WT even at ψw = -1.6 MPa. The heatmaps for UPR, ERAD (ER-associated degradation protein system), drought-responsive and cell death-associated genes revealed that the leaf transcriptome of 35S::BiP-4 at ψw = -1.0 MPa clustered together with the transcriptome of well-watered leaves and they diverged considerably from the drought-induced transcriptome of the WT (ψw = -1.0, -1.7 and -2.0 MPa) and 35S::BiP-4 leaves at ψw = -1.6 MPa. Taken together, our data revealed that BiP-overexpressing lines requires a much higher level of stress (ψw = -1.6 MPa) to respond to drought than that of WT (ψw = -1.0). Therefore, BiP overexpression maintains cellular homeostasis under water stress conditions and thus ameliorates endogenous osmotic stress.
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Affiliation(s)
- Humberto H. Carvalho
- National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, MG, Brazil
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | - Otávio J. B. Brustolini
- National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, MG, Brazil
- Departamento de Bioquímica e Biologia Molecular/Bioagro, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | - Maiana R. Pimenta
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | - Giselle C. Mendes
- National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, MG, Brazil
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | - Bianca C. Gouveia
- National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, MG, Brazil
- Departamento de Bioquímica e Biologia Molecular/Bioagro, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | - Priscila A. Silva
- National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, MG, Brazil
- Departamento de Bioquímica e Biologia Molecular/Bioagro, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | | | - Clenilso S. Mota
- National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | - Juliana R. L. Soares-Ramos
- Departamento de Bioquímica e Biologia Molecular/Bioagro, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | - Elizabeth P. B. Fontes
- National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, MG, Brazil
- Departamento de Bioquímica e Biologia Molecular/Bioagro, Universidade Federal de Viçosa, Viçosa, MG, Brazil
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81
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Ruberti C, Brandizzi F. Conserved and plant-unique strategies for overcoming endoplasmic reticulum stress. FRONTIERS IN PLANT SCIENCE 2014; 5:69. [PMID: 24616733 PMCID: PMC3935401 DOI: 10.3389/fpls.2014.00069] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 02/10/2014] [Indexed: 05/19/2023]
Abstract
Stress caused by environmental conditions or physiological growth can lead to an accumulation of unfolded proteins in the endoplasmic reticulum (ER) causing ER stress, which in turn triggers a cytoprotective mechanism termed the unfolded protein response (UPR). Under mild-short stress conditions the UPR can restore ER functioning and cell growth, such as reducing the load of unfolded proteins through the upregulation of genes involved in protein folding and in degrading mis-folded proteins, and through autophagy activation, but it can also lead to cell death under prolonged and severe stress conditions. A diversified suite of sensors has been evolved in the eukaryotic lineages to orchestrate the UPR most likely to suit the cell's necessity to respond to the different kinds of stress in a conserved as well as species-specific manner. In plants three UPR sensors cooperate with non-identical signaling pathways: the protein kinase inositol-requiring enzyme (IRE1), the ER-membrane-associated transcription factor bZIP28, and the GTP-binding protein β1 (AGB1). In this mini-review, we show how plants differ from the better characterized metazoans and fungi, providing an overview of the signaling pathways of the UPR, and highlighting the overlapping and the peculiar roles of the different UPR branches in light of evolutionary divergences in eukaryotic kingdoms.
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Affiliation(s)
- Cristina Ruberti
- Plant Research Laboratory, Department of Energy, Michigan State UniversityEast Lansing, MI, USA
- Department of Plant Biology, Michigan State UniversityEast Lansing, MI, USA
| | - Federica Brandizzi
- Plant Research Laboratory, Department of Energy, Michigan State UniversityEast Lansing, MI, USA
- Department of Plant Biology, Michigan State UniversityEast Lansing, MI, USA
- *Correspondence: Federica Brandizzi, Plant Research Laboratory, Department of Energy, Michigan State University, 612 Wilson Road, East Lansing, MI 48824, USA e-mail:
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82
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Chen Y, Aung K, Rolčík J, Walicki K, Friml J, Brandizzi F. Inter-regulation of the unfolded protein response and auxin signaling. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2014; 77:97-107. [PMID: 24180465 PMCID: PMC3981873 DOI: 10.1111/tpj.12373] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Revised: 10/17/2013] [Accepted: 10/21/2013] [Indexed: 05/03/2023]
Abstract
The unfolded protein response (UPR) is a signaling network triggered by overload of protein-folding demand in the endoplasmic reticulum (ER), a condition termed ER stress. The UPR is critical for growth and development; nonetheless, connections between the UPR and other cellular regulatory processes remain largely unknown. Here, we identify a link between the UPR and the phytohormone auxin, a master regulator of plant physiology. We show that ER stress triggers down-regulation of auxin receptors and transporters in Arabidopsis thaliana. We also demonstrate that an Arabidopsis mutant of a conserved ER stress sensor IRE1 exhibits defects in the auxin response and levels. These data not only support that the plant IRE1 is required for auxin homeostasis, they also reveal a species-specific feature of IRE1 in multicellular eukaryotes. Furthermore, by establishing that UPR activation is reduced in mutants of ER-localized auxin transporters, including PIN5, we define a long-neglected biological significance of ER-based auxin regulation. We further examine the functional relationship of IRE1 and PIN5 by showing that an ire1 pin5 triple mutant enhances defects of UPR activation and auxin homeostasis in ire1 or pin5. Our results imply that the plant UPR has evolved a hormone-dependent strategy for coordinating ER function with physiological processes.
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Affiliation(s)
- Yani Chen
- Michigan State University/Department of Energy Plant Research Laboratory and Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Kyaw Aung
- Michigan State University/Department of Energy Plant Research Laboratory and Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Jakub Rolčík
- Laboratory of Growth Regulators, Faculty of Science, Palacký University and Institute of Experimental Botany AS CR, Šlechtitelů 11, 78371 Olomouc, Czech Republic
| | - Kathryn Walicki
- Michigan State University/Department of Energy Plant Research Laboratory and Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Jiří Friml
- Department of Functional Genomics and Proteomics, Central European Institute of Technology (CEITEC), Masaryk University, 62500 Brno, Czech Republic
- Institute of Science and Technology Austria (IST Austria), 3400 Klosterneuburg, Austria
| | - Federica Brandizzi
- Michigan State University/Department of Energy Plant Research Laboratory and Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
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83
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Williams B, Verchot J, Dickman MB. When supply does not meet demand-ER stress and plant programmed cell death. FRONTIERS IN PLANT SCIENCE 2014; 5:211. [PMID: 24926295 PMCID: PMC4045240 DOI: 10.3389/fpls.2014.00211] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Accepted: 04/29/2014] [Indexed: 05/10/2023]
Abstract
The endoplasmic reticulum (ER) is the central organelle in the eukaryotic secretory pathway. The ER functions in protein synthesis and maturation and is crucial for proper maintenance of cellular homeostasis and adaptation to adverse environments. Acting as a cellular sentinel, the ER is exquisitely sensitive to changing environments principally via the ER quality control machinery. When perturbed, ER-stress triggers a tightly regulated and highly conserved, signal transduction pathway known as the unfolded protein response (UPR) that prevents the dangerous accumulation of unfolded/misfolded proteins. In situations where excessive UPR activity surpasses threshold levels, cells deteriorate and eventually trigger programmed cell death (PCD) as a way for the organism to cope with dysfunctional or toxic signals. The programmed cell death that results from excessive ER stress in mammalian systems contributes to several important diseases including hypoxia, neurodegeneration, and diabetes. Importantly, hallmark features and markers of cell death that are associated with ER stress in mammals are also found in plants. In particular, there is a common, conserved set of chaperones that modulate ER cell death signaling. Here we review the elements of plant cell death responses to ER stress and note that an increasing number of plant-pathogen interactions are being identified in which the host ER is targeted by plant pathogens to establish compatibility.
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Affiliation(s)
- Brett Williams
- Centre for Tropical Crops and Biocommodities, Queensland University of TechnologyBrisbane, QLD, Australia
| | - Jeanmarie Verchot
- Department of Entomology and Plant Pathology, Oklahoma State UniversityStillwater, OK, USA
| | - Martin B. Dickman
- Department of Plant Pathology and Microbiology, Institute for Plant Genomics and Biotechnology, Texas A&M UniversityCollege Station, TX, USA
- *Correspondence: Martin B. Dickman, Department of Plant Pathology and Microbiology, Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, TX 77843, USA e-mail:
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84
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Dong X, Wang X, Zhang L, Yang Z, Xin X, Wu S, Sun C, Liu J, Yang J, Luo X. Identification and characterization of OsEBS, a gene involved in enhanced plant biomass and spikelet number in rice. PLANT BIOTECHNOLOGY JOURNAL 2013; 11:1044-57. [PMID: 23924074 DOI: 10.1111/pbi.12097] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Revised: 05/27/2013] [Accepted: 06/19/2013] [Indexed: 05/03/2023]
Abstract
Common wild rice (Oryza rufipogon Griff.) is an important genetic reservoir for rice improvement. We investigated a quantitative trait locus (QTL), qGP5-1, which is related to plant height, leaf size and panicle architecture, using a set of introgression lines of O. rufipogon in the background of the Indica cultivar Guichao2 (Oryza sativa L.). We cloned and characterized qGP5-1 and confirmed that the newly identified gene OsEBS (enhancing biomass and spikelet number) increased plant height, leaf size and spikelet number per panicle, leading to an increase in total grain yield per plant. Our results showed that the increased size of vegetative organs in OsEBS-expressed plants was enormously caused by increasing cell number. Sequence alignment showed that OsEBS protein contains a region with high similarity to the N-terminal conserved ATPase domain of Hsp70, but it lacks the C-terminal regions of the peptide-binding domain and the C-terminal lid. More results indicated that OsEBS gene did not have typical characteristics of Hsp70 in this study. Furthermore, Arabidopsis (Arabidopsis thaliana) transformed with OsEBS showed a similar phenotype to OsEBS-transgenic rice, indicating a conserved function of OsEBS among plant species. Together, we report the cloning and characterization of OsEBS, a new QTL that controls rice biomass and spikelet number, through map-based cloning, and it may have utility in improving grain yield in rice.
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Affiliation(s)
- Xianxin Dong
- State Key Laboratory of Genetic Engineering, Institute of Genetics, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai, China
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85
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Xu H, Xu W, Xi H, Ma W, He Z, Ma M. The ER luminal binding protein (BiP) alleviates Cd(2+)-induced programmed cell death through endoplasmic reticulum stress-cell death signaling pathway in tobacco cells. JOURNAL OF PLANT PHYSIOLOGY 2013; 170:1434-41. [PMID: 23867017 DOI: 10.1016/j.jplph.2013.05.017] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 05/22/2013] [Accepted: 05/24/2013] [Indexed: 05/23/2023]
Abstract
Cadmium (Cd) is very toxic to plant cells and Cd(2+) stress induces programmed cell death (PCD) in Nicotiana tabacum L. cv. bright yellow-2 (BY-2) cells. In plants, PCD can be regulated through the endoplasmic reticulum (ER) stress-cell death signaling pathway. However, the mechanism of Cd(2+)-induced PCD remains unclear. In this study, we found that Cd(2+) treatment induced ER stress in tobacco BY-2 cells. The expression of two ER stress markers NtBLP4 and NtPDI and an unfolded protein response related transcription factor NtbZIP60 were upregulated with Cd(2+) stress. Meanwhile, the PCD triggered by prolonged Cd(2+) stress could be relieved by two ER chemical chaperones, 4-phenylbutyric acid and tauroursodeoxycholic acid. These results demonstrate that the ER stress-cell death signaling pathway participates in the mediation of Cd(2+)-induced PCD. Furthermore, the ER chaperone AtBiP2 protein alleviated Cd(2+)-induced ER stress and PCD in BY-2 cells based on the fact that heterologous expression of AtBiP2 in tobacco BY-2 cells reduced the expression of NtBLP4 and a PCD-related gene NtHsr203J under Cd(2+) stress conditions. In summary, these results suggest that the ER stress-cell death signaling pathway regulates Cd(2+)-induced PCD in tobacco BY-2 cells, and that the AtBiP2 protein act as a negative regulator in this process.
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Affiliation(s)
- Hua Xu
- Key Laboratory of Plant Resources, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
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86
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Scranton MA, Fowler JH, Girke T, Walling LL. Microarray analysis of tomato's early and late wound response reveals new regulatory targets for Leucine aminopeptidase A. PLoS One 2013; 8:e77889. [PMID: 24205013 PMCID: PMC3812031 DOI: 10.1371/journal.pone.0077889] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 09/04/2013] [Indexed: 11/22/2022] Open
Abstract
Wounding due to mechanical injury or insect feeding causes a wide array of damage to plant cells including cell disruption, desiccation, metabolite oxidation, and disruption of primary metabolism. In response, plants regulate a variety of genes and metabolic pathways to cope with injury. Tomato (Solanum lycopersicum) is a model for wound signaling but few studies have examined the comprehensive gene expression profiles in response to injury. A cross-species microarray approach using the TIGR potato 10-K cDNA array was analyzed for large-scale temporal (early and late) and spatial (locally and systemically) responses to mechanical wounding in tomato leaves. These analyses demonstrated that tomato regulates many primary and secondary metabolic pathways and this regulation is dependent on both timing and location. To determine if LAP-A, a known modulator of wound signaling, influences gene expression beyond the core of late wound-response genes, changes in RNAs from healthy and wounded Leucine aminopeptidase A-silenced (LapA-SI) and wild-type (WT) leaves were examined. While most of the changes in gene expression after wounding in LapA-SI leaves were similar to WT, overall responses were delayed in the LapA-SI leaves. Moreover, two pathogenesis-related 1 (PR-1c and PR-1a2) and two dehydrin (TAS14 and Dhn3) genes were negatively regulated by LAP-A. Collectively, this study has shown that tomato wound responses are complex and that LAP-A's role in modulation of wound responses extends beyond the well described late-wound gene core.
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Affiliation(s)
- Melissa A. Scranton
- Department of Botany and Plant Sciences, Center for Plant Cell Biology, University of California Riverside, Riverside, California, United States of America
| | - Jonathan H. Fowler
- Department of Botany and Plant Sciences, Center for Plant Cell Biology, University of California Riverside, Riverside, California, United States of America
| | - Thomas Girke
- Department of Botany and Plant Sciences, Center for Plant Cell Biology, University of California Riverside, Riverside, California, United States of America
| | - Linda L. Walling
- Department of Botany and Plant Sciences, Center for Plant Cell Biology, University of California Riverside, Riverside, California, United States of America
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87
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Protein kinase and ribonuclease domains of IRE1 confer stress tolerance, vegetative growth, and reproductive development in Arabidopsis. Proc Natl Acad Sci U S A 2013; 110:19633-8. [PMID: 24145452 DOI: 10.1073/pnas.1314749110] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The unfolded protein response (UPR) endows plants with the capacity to perceive, respond, and protect themselves from adverse environmental conditions. The UPR signaling pathway in Arabidopsis has two "arms," one arm involving the bifunctional protein kinase (PK)/ribonuclease, IRE1, a RNA splicing enzyme, and another involving membrane-associated transcription factors, such as basic leucine zipper transcription factor 28 (bZIP28). Because of functional redundancies, single gene mutations in the plant UPR signaling pathway generally have not resulted in prominent phenotypes. In this study we generated multiple mutations in the UPR signaling pathway, such as an ire1a ire1b double mutant, which showed defects in stress tolerance and vegetative growth and development. Complementation of ire1a ire1b with constructs containing site-specific mutations in the PK or RNase domains of IRE1b demonstrated that a functional RNase domain is required for endoplasmic reticulum stress tolerance, and that both the PK and RNase domains are required for normal vegetative growth under unstressed conditions. Root growth under stress conditions was dependent on the splicing target of IRE1b, bZIP60 mRNA, and on regulated IRE1-dependent decay of target genes. However, root and shoot growth in the absence of stress was independent of bZIP60. Blocking both arms of the UPR signaling pathway in a triple ire1a ire1b bzip28 mutant was lethal, impacting pollen viability under unstressed conditions. Complementation with IRE1b constructs showed that both the PK and RNase domains are required for normal gametophyte development, but bZIP60 is not. Hence, the UPR plays a critical role in stress tolerance, and in normal vegetative growth and reproductive development in plants.
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88
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Wakasa Y, Hayashi S, Takaiwa F. Effect of overexpression of kinase- or RNase-deficient OsIRE1 on the endoplasmic reticulum stress response in transgenic rice plants. PLANT SIGNALING & BEHAVIOR 2013; 8:25343. [PMID: 23803744 PMCID: PMC4002584 DOI: 10.4161/psb.25343] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
IRE1 is an endoplasmic reticulum (ER) stress sensor protein in eukaryotes. In this study, we generated transgenic rice plants overexpressing three types of OsIRE1, including wild-type OsIRE1 (IRE1-OE) and two disrupted-IRE1s deficient in either kinase activity (K519A-OE) or RNase activity (K833A-OE), under the control of a constitutive promoter. Overexpression of wild-type IRE1 induced the ER stress response in transgenic rice even under non-stress conditions, whereas K519A-OE and K833A-OE had dominant negative effects on endogenous OsIRE1 expression in these transgenic plants. These lines exhibited phenotypes that were quite similar to those of OsIRE1 knock-down rice. These observations suggest that the two types of functionally disrupted OsIRE1 proteins behave as competitive inhibitors toward the ER stress response in transgenic rice plants. Furthermore, OsIRE1 may have a vital, as yet unidentified function, as determined through the characterization of the transgenic plants generated in this study.
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89
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IRE1: ER stress sensor and cell fate executor. Trends Cell Biol 2013; 23:547-55. [PMID: 23880584 DOI: 10.1016/j.tcb.2013.06.005] [Citation(s) in RCA: 401] [Impact Index Per Article: 36.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 05/31/2013] [Accepted: 06/19/2013] [Indexed: 12/20/2022]
Abstract
Cells operate a signaling network termed the unfolded protein response (UPR) to monitor protein-folding capacity in the endoplasmic reticulum (ER). Inositol-requiring enzyme 1 (IRE1) is an ER transmembrane sensor that activates the UPR to maintain the ER and cellular function. Although mammalian IRE1 promotes cell survival, it can initiate apoptosis via decay of antiapoptotic miRNAs. Convergent and divergent IRE1 characteristics between plants and animals underscore its significance in cellular homeostasis. This review provides an updated scenario of the IRE1 signaling model, discusses emerging IRE1 sensing mechanisms, compares IRE1 features among species, and outlines exciting future directions in UPR research.
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90
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Pu Y, Bassham DC. Links between ER stress and autophagy in plants. PLANT SIGNALING & BEHAVIOR 2013; 8:e24297. [PMID: 23603973 PMCID: PMC3907440 DOI: 10.4161/psb.24297] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 03/13/2013] [Indexed: 05/23/2023]
Abstract
Autophagy is a major pathway for the delivery of proteins or organelles to be degraded in the vacuole and recycled. It can be induced by abiotic stresses, senescence, and pathogen infection. Recent research has shown that autophagy is activated by ER stress. Here we review the major progress that has been made in the study of autophagy and ER stress in plants, and describe the links between ER stress and autophagy to guide further study on how autophagy is regulated in response to ER stress.
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91
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Recent advances in understanding the control of secretory proteins by the unfolded protein response in plants. Int J Mol Sci 2013; 14:9396-407. [PMID: 23629671 PMCID: PMC3676789 DOI: 10.3390/ijms14059396] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 04/17/2013] [Accepted: 04/18/2013] [Indexed: 01/03/2023] Open
Abstract
The membrane transport system is built on the proper functioning of the endoplasmic reticulum (ER). The accumulation of unfolded proteins in the ER lumen (ER stress) disrupts ER homeostasis and disturbs the transport system. In response to ER stress, eukaryotic cells activate intracellular signaling (named the unfolded protein response, UPR), which contributes to the quality control of secretory proteins. On the other hand, the deleterious effects of UPR on plant health and growth characteristics have frequently been overlooked, due to limited information on this mechanism. However, recent studies have shed light on the molecular mechanism of plant UPR, and a number of its unique characteristics have been elucidated. This study briefly reviews the progress of understanding what is happening in plants under ER stress conditions.
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92
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Duwi Fanata WI, Lee SY, Lee KO. The unfolded protein response in plants: a fundamental adaptive cellular response to internal and external stresses. J Proteomics 2013; 93:356-68. [PMID: 23624343 DOI: 10.1016/j.jprot.2013.04.023] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 04/07/2013] [Accepted: 04/10/2013] [Indexed: 10/26/2022]
Abstract
In eukaryotic cells, proteins that enter the secretory pathway are translated on membrane-bound ribosomes and translocated into the endoplasmic reticulum (ER), where they are subjected to chaperone-assisted folding, post-translational modification and assembly. During the evolution of the eukaryotic cell, a homeostatic mechanism was developed to maintain the functions of the ER in the face of various internal and external stresses. The most severe stresses imposed on eukaryotic cells can induce ER stress that can overwhelm the processing capacity of the ER, leading to the accumulation of unfolded proteins in the ER lumen. To cope with this accumulation of unfolded proteins, the unfolded protein response (UPR) is activated to alter transcriptional programs through inositol-requiring enzyme 1 (IRE1) and bZIP17/28 in plants. In addition to transcriptional induction of UPR genes, quality control (QC), translational attenuation, ER-associated degradation (ERAD) and ER stress-induced apoptosis are also conserved as fundamental adaptive cellular responses to ER stress in plants. This article is part of a Special Issue entitled: Translational Plant Proteomics.
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Affiliation(s)
- Wahyu Indra Duwi Fanata
- Division of Applied Life Science (BK21 Program) and PMBBRC, Gyeongsang National University, 501 Jinju-daero, Jinju, 660-701, Republic of Korea
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93
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Deng Y, Srivastava R, Howell SH. Endoplasmic reticulum (ER) stress response and its physiological roles in plants. Int J Mol Sci 2013; 14:8188-212. [PMID: 23591838 PMCID: PMC3645738 DOI: 10.3390/ijms14048188] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2013] [Revised: 03/19/2013] [Accepted: 04/01/2013] [Indexed: 01/29/2023] Open
Abstract
The endoplasmic reticulum (ER) stress response is a highly conserved mechanism that results from the accumulation of unfolded or misfolded proteins in the ER. The response plays an important role in allowing plants to sense and respond to adverse environmental conditions, such as heat stress, salt stress and pathogen infection. Since the ER is a well-controlled microenvironment for proper protein synthesis and folding, it is highly susceptible to stress conditions. Accumulation of unfolded or misfolded proteins activates a signaling pathway, called the unfolded protein response (UPR), which acts to relieve ER stress and, if unsuccessful, leads to cell death. Plants have two arms of the UPR signaling pathway, an arm involving the proteolytic processing of membrane-associated basic leucine zipper domain (bZIP) transcription factors and an arm involving RNA splicing factor, IRE1, and its mRNA target. These signaling pathways play an important role in determining the cell's fate in response to stress conditions.
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Affiliation(s)
- Yan Deng
- Plant Sciences Institute and Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA; E-Mails: (Y.D.); (R.S.)
| | - Renu Srivastava
- Plant Sciences Institute and Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA; E-Mails: (Y.D.); (R.S.)
| | - Stephen H. Howell
- Plant Sciences Institute and Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA; E-Mails: (Y.D.); (R.S.)
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94
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Potential for therapeutic manipulation of the UPR in disease. Semin Immunopathol 2013; 35:351-73. [PMID: 23572207 PMCID: PMC3641308 DOI: 10.1007/s00281-013-0370-z] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Accepted: 03/13/2013] [Indexed: 12/16/2022]
Abstract
Increased endoplasmic reticulum (ER) stress and the activated unfolded protein response (UPR) signaling associated with it play key roles in physiological processes as well as under pathological conditions. The UPR normally protects cells and re-establishes cellular homeostasis, but prolonged UPR activation can lead to the development of various pathologies. These features make the UPR signaling pathway an attractive target for the treatment of diseases whose pathogenesis is characterized by chronic activation of this pathway. Here, we focus on the molecular signaling pathways of the UPR and suggest possible ways to target this response for therapeutic purposes.
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95
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Hayashi S, Takahashi H, Wakasa Y, Kawakatsu T, Takaiwa F. Identification of a cis-element that mediates multiple pathways of the endoplasmic reticulum stress response in rice. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 74:248-257. [PMID: 23331932 DOI: 10.1111/tpj.12117] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2012] [Revised: 01/04/2013] [Accepted: 01/10/2013] [Indexed: 06/01/2023]
Abstract
The accumulation of unfolded proteins in the endoplasmic reticulum (ER) lumen leads to ER stress. Intracellular signalling pathways are activated to alleviate the stress. The ER stress sensor IRE1 induces the active form of key transcription factors, such as XBP1 in mammals and bZIP50 in Oryza sativa (rice), by mediating the unconventional splicing of their mRNAs. Although the characterization of cis-elements that are recognized by these transcription factors is essential for understanding ER stress responses, such cis-elements remain unidentified in plants. Here, a cis-element named pUPRE-II was identified from promoters of bZIP50-dependent genes using chromatin immunoprecipitation assays and electrophoretic mobility shift assays. The sequence of pUPRE-II (e.g., 5'-GATGACGCGTAC-3' in the OsSAR1 promoter) was found to be flexible and not identical with that of mUPRE, a cis-element that preferentially interacts with mammalian XBP1. Unexpectedly, the transcription factor bZIP60, another ER stress sensor in rice, and a counterpart of mammalian ATF6, also showed strong binding affinity for pUPRE-II without assistance from co-factors. Reporter assays indicated that pUPRE-II significantly contributes to gene expression mediated by bZIP50 or bZIP60 in rice. Although both bZIP50 and bZIP60 bound to pUPRE-II, these transcription factors showed distinct requirements for transcriptional activation. This study provides a missing link between ER stress sensors and stress-responsive genes in rice. Furthermore, the characteristics of pUPRE-II highlight the uniqueness of ER stress-responsive transcription in plants.
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Affiliation(s)
- Shimpei Hayashi
- Genetically Modified Organism Research Center, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki, 305-8602, Japan
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96
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Defects in IRE1 enhance cell death and fail to degrade mRNAs encoding secretory pathway proteins in the Arabidopsis unfolded protein response. Proc Natl Acad Sci U S A 2013; 110:5713-8. [PMID: 23509268 DOI: 10.1073/pnas.1219047110] [Citation(s) in RCA: 144] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The unfolded protein response (UPR) is a cellular response highly conserved in eukaryotes to obviate accumulation of misfolded proteins in the endoplasmic reticulum (ER). Inositol-requiring enzyme 1 (IRE1) catalyzes the cytoplasmic splicing of mRNA encoding bZIP transcription factors to activate the UPR signaling pathway. Arabidopsis IRE1 was recently shown to be involved in the cytoplasmic splicing of bZIP60 mRNA. In the present study, we demonstrated that an Arabidopsis mutant with defects in two IRE1 paralogs showed enhanced cell death upon ER stress compared with a mutant with defects in bZIP60 and wild type, suggesting an alternative function of IRE1 in the UPR. Analysis of our previous microarray data and subsequent quantitative PCR indicated degradation of mRNAs encoding secretory pathway proteins by tunicamycin, DTT, and heat in an IRE1-dependent manner. The degradation of mRNAs localized to the ER during the UPR was considered analogous to a molecular mechanism referred to as the regulated IRE1-dependent decay of mRNAs reported in metazoans. Another microarray analysis conducted in the condition repressing transcription with actinomycin D and a subsequent Gene Set Enrichment Analysis revealed the regulated IRE1-dependent decay of mRNAs-mediated degradation of a significant portion of mRNAs encoding the secretory pathway proteins. In the mutant with defects in IRE1, genes involved in the cytosolic protein response such as heat shock factor A2 were up-regulated by tunicamycin, indicating the connection between the UPR and the cytosolic protein response.
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97
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De Wilde K, De Buck S, Vanneste K, Depicker A. Recombinant antibody production in Arabidopsis seeds triggers an unfolded protein response. PLANT PHYSIOLOGY 2013; 161:1021-33. [PMID: 23188806 PMCID: PMC3561000 DOI: 10.1104/pp.112.209718] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Accepted: 11/26/2012] [Indexed: 05/07/2023]
Abstract
Among the many plant-based production systems that are being tested for molecular farming, seeds are very attractive, as they provide a stable environment in which the accumulating recombinant proteins can be stored. However, it is not known exactly how high production levels of recombinant antibodies influence the endogenous transcriptome and proteome of the developing seed. To address this question, we studied the transcriptomic status in developing Arabidopsis (Arabidopsis thaliana) seeds 13 d post anthesis of three transgenic lines, producing varying levels of recombinant VHH or single-chain Fv antibody fragments fused to the human immunoglobulin G1-derived Fc fragment under the control of the β-PHASEOLIN seed-specific promoter. Using genome-wide Tiling arrays, we demonstrated that only a small proportion of the transcriptome was significantly changed in each of the lines compared with the wild type. Strikingly, in all three lines, we found a large overlap of up-regulated genes corresponding to protein folding, glycosylation/modification, translocation, vesicle transport, and protein degradation, suggestive of a state of cellular stress called the unfolded protein response. Moreover, the gene up-regulation amplitude was similar in all three lines. We hypothesize that the production of recombinant antibodies in the endoplasmic reticulum triggers endoplasmic reticulum stress, causing a disturbance of the normal cellular homeostasis.
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Affiliation(s)
- Kirsten De Wilde
- Department of Plant Systems Biology, VIB, B–9052 Ghent, Belgium (K.D.W., S.D.B., K.V., A.D.); and Department of Plant Biotechnology and Bioinformatics, Ghent University, B–9052 Ghent, Belgium (K.D.W., S.D.B., K.V., A.D.)
| | - Sylvie De Buck
- Department of Plant Systems Biology, VIB, B–9052 Ghent, Belgium (K.D.W., S.D.B., K.V., A.D.); and Department of Plant Biotechnology and Bioinformatics, Ghent University, B–9052 Ghent, Belgium (K.D.W., S.D.B., K.V., A.D.)
| | - Kevin Vanneste
- Department of Plant Systems Biology, VIB, B–9052 Ghent, Belgium (K.D.W., S.D.B., K.V., A.D.); and Department of Plant Biotechnology and Bioinformatics, Ghent University, B–9052 Ghent, Belgium (K.D.W., S.D.B., K.V., A.D.)
| | - Ann Depicker
- Department of Plant Systems Biology, VIB, B–9052 Ghent, Belgium (K.D.W., S.D.B., K.V., A.D.); and Department of Plant Biotechnology and Bioinformatics, Ghent University, B–9052 Ghent, Belgium (K.D.W., S.D.B., K.V., A.D.)
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98
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Evolution of the unfolded protein response. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2458-63. [PMID: 23369734 DOI: 10.1016/j.bbamcr.2013.01.016] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 01/07/2013] [Accepted: 01/13/2013] [Indexed: 01/05/2023]
Abstract
The unfolded protein response (UPR) is a network of signaling pathways that responds to stress in the endoplasmic reticulum (ER). The general output of the UPR is to upregulate genes involved in ER function, thus restoring and/or increasing the capacity of the ER to fold and process proteins. In parallel, many organisms have mechanisms for limiting the load on the ER by attenuating translation or degrading ER-targeted mRNAs. Despite broad conservation of these signaling pathways across eukaryotes, interesting variations demonstrate a variety of mechanisms for managing ER stress. How do early-diverging protozoa respond to stress when they lack traditional transcriptional regulation? What is the role of the ER stress sensor Ire1 in fungal species that are missing its main target? Here I describe how diverse species have optimized the UPR to fit their needs. This article is part of a Special Issue entitled: Functional and structural diversity of endoplasmic reticulum.
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Scranton MA, Fowler JH, Girke T, Walling LL. Microarray analysis of tomato's early and late wound response reveals new regulatory targets for Leucine aminopeptidase A. PLoS One 2013. [PMID: 24205013 DOI: 10.1371/journal.pone.007788] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023] Open
Abstract
Wounding due to mechanical injury or insect feeding causes a wide array of damage to plant cells including cell disruption, desiccation, metabolite oxidation, and disruption of primary metabolism. In response, plants regulate a variety of genes and metabolic pathways to cope with injury. Tomato (Solanum lycopersicum) is a model for wound signaling but few studies have examined the comprehensive gene expression profiles in response to injury. A cross-species microarray approach using the TIGR potato 10-K cDNA array was analyzed for large-scale temporal (early and late) and spatial (locally and systemically) responses to mechanical wounding in tomato leaves. These analyses demonstrated that tomato regulates many primary and secondary metabolic pathways and this regulation is dependent on both timing and location. To determine if LAP-A, a known modulator of wound signaling, influences gene expression beyond the core of late wound-response genes, changes in RNAs from healthy and wounded Leucine aminopeptidase A-silenced (LapA-SI) and wild-type (WT) leaves were examined. While most of the changes in gene expression after wounding in LapA-SI leaves were similar to WT, overall responses were delayed in the LapA-SI leaves. Moreover, two pathogenesis-related 1 (PR-1c and PR-1a2) and two dehydrin (TAS14 and Dhn3) genes were negatively regulated by LAP-A. Collectively, this study has shown that tomato wound responses are complex and that LAP-A's role in modulation of wound responses extends beyond the well described late-wound gene core.
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Affiliation(s)
- Melissa A Scranton
- Department of Botany and Plant Sciences, Center for Plant Cell Biology, University of California Riverside, Riverside, California, United States of America
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100
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Abstract
Endoplasmic reticulum (ER) stress is of considerable interest to plant biologists because it occurs in plants subjected to adverse environmental conditions. ER stress responses mitigate the damage caused by stress and confer levels of stress tolerance to plants. ER stress is activated by misfolded proteins that accumulate in the ER under adverse environmental conditions. Under these conditions, the demand for protein folding exceeds the capacity of the system, which sets off the unfolded protein response (UPR). Two arms of the UPR signaling pathway have been described in plants: one that involves two ER membrane-associated transcription factors (bZIP17 and bZIP28) and another that involves a dual protein kinase (RNA-splicing factor IRE1) and its target RNA (bZIP60). Under mild or short-term stress conditions, signaling from IRE1 activates autophagy, a cell survival response. But under severe or chronic stress conditions, ER stress can lead to cell death.
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Affiliation(s)
- Stephen H Howell
- Plant Sciences Institute and Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA 50011, USA.
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