1
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Afrin T, Costello CN, Monella AN, Kørner CJ, Pajerowska-Mukhtar KM. The interplay of GTP-binding protein AGB1 with ER stress sensors IRE1a and IRE1b modulates Arabidopsis unfolded protein response and bacterial immunity. PLANT SIGNALING & BEHAVIOR 2022; 17:2018857. [PMID: 34968413 PMCID: PMC8920210 DOI: 10.1080/15592324.2021.2018857] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 12/10/2021] [Accepted: 12/10/2021] [Indexed: 06/14/2023]
Abstract
In eukaryotic cells, the accumulation of unfolded or misfolded proteins in the endoplasmic reticulum (ER) results in ER stress that induces a cascade of reactions called the unfolded protein response (UPR). In Arabidopsis, the most conserved UPR sensor, Inositol-requiring enzyme 1 (IRE1), responds to both abiotic- and biotic-induced ER stress. Guanine nucleotide-binding proteins (G proteins) constitute another universal and conserved family of signal transducers that have been extensively investigated due to their ubiquitous presence and diverse nature of action. Arabidopsis GTP-binding protein β1 (AGB1) is the only G-protein β-subunit encoded by the Arabidopsis genome that is involved in numerous signaling pathways. Mounting evidence suggests the existence of a crosstalk between IRE1 and G protein signaling during ER stress. AGB1 has previously been shown to control a distinct UPR pathway independently of IRE1 when treated with an ER stress inducer tunicamycin. Our results obtained with combinatorial knockout mutants support the hypothesis that both IRE1 and AGB1 synergistically contribute to ER stress responses chemically induced by dithiothreitol (DTT) as well as to the immune responses against a phytopathogenic bacterium Pseudomonas syringae pv. tomato strain DC3000. Our study highlights the crosstalk between the plant UPR transducers under abiotic and biotic stress.
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Affiliation(s)
- Taiaba Afrin
- Department of Biology, University of Alabama at Birmingham, 1300 University Blvd, Birmingham, AL, USA
| | - Caitlin N. Costello
- Department of Biology, University of Alabama at Birmingham, 1300 University Blvd, Birmingham, AL, USA
| | - Amber N. Monella
- Department of Biology, University of Alabama at Birmingham, 1300 University Blvd, Birmingham, AL, USA
| | - Camilla J. Kørner
- Department of Biology, University of Alabama at Birmingham, 1300 University Blvd, Birmingham, AL, USA
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2
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Tiwari R, Bisht NC. The multifaceted roles of heterotrimeric G-proteins: lessons from models and crops. PLANTA 2022; 255:88. [PMID: 35304667 DOI: 10.1007/s00425-022-03868-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 03/04/2022] [Indexed: 06/14/2023]
Abstract
The review summarizes our advanced understanding of the heterotrimeric G-protein research from model plants and their emerging roles in modulating various plant architecture and agronomical traits in crop species. Heterotrimeric G-proteins (hereafter G-proteins), consisting of G-alpha (Gα), G-beta (Gβ) and G-gamma (Gγ) subunits, are key signal transducers conserved across different forms of life. The discovery of plant lineage-specific G-protein components (extra-large G-proteins and type-C Gγ subunits), inherent polyploidy in angiosperms, and unique modes of G-protein cycle regulation in plants pointed out to a few fundamental differences of plant G-protein signaling from its animal counterpart. Over the last 2 decades, extensive studies in the model plant Arabidopsis thaliana have confirmed the involvement of G-proteins in a wide range of plant growth and development, and stress adaptation processes. The G-protein research in crop species, however, is still in its infancy, and a handful of studies suggest important roles of G-proteins in regulating plant architectural and key agronomical traits including plant's response to abiotic and biotic factors. We propose that the advancement made in plant G-proteins research will facilitate the development of novel approaches to manage plant yield and fitness in changing environments.
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Affiliation(s)
- Ruchi Tiwari
- National Institute of Plant Genome Research (NIPGR), Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Naveen C Bisht
- National Institute of Plant Genome Research (NIPGR), Aruna Asaf Ali Marg, New Delhi, 110067, India.
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3
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Urano D, Leong R, Wu TY, Jones AM. Quantitative morphological phenomics of rice G protein mutants portend autoimmunity. Dev Biol 2019; 457:83-90. [PMID: 31541643 DOI: 10.1016/j.ydbio.2019.09.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 09/12/2019] [Accepted: 09/17/2019] [Indexed: 10/26/2022]
Abstract
The heterotrimeric G protein complex, composed of Gα, Gβ, and Gγ subunits, plays some role in structural development in plants but this role could be indirect because loss-of-function mutations do not alter the body plan and post-embryonic organs differ only morphologically and not in their identity. This uncertainty has been compounded by the fact that loss of the Gβ subunit in cereals, but not Arabidopsis, is seedling lethal and that loss of maize Gα subunit confers prolificacy of a reproductive organ. In this study, we comprehensively profiled the root and shoot structural traits of rice Gα-null and viable Gβ-RNAi "knockdown" mutants, and found anomalous morphologies caused by Gβ-RNAi that are distinct from the Arabidopsis orthologue. The rice Gβ-RNAi mutant exhibited reduced radial growth of aerial parts as well as a more compact root architecture, among which smaller root mass seems mainly due to increased necrosis when grown on soil. In addition, three dimensional analyses of rice root system architecture revealed that the smaller root architecture of Gβ-RNAi plant is also due to both reduced root elongation and adventitious root formation. This contrasts to the Arabidopsis Gβ-null mutation that promotes cell proliferation. There is elevated cell senescence activity both visualized by Evans Blue staining and inferred from an expression analysis of cell-death marker genes. We propose that the morphological phenotypes of rice Gβ-RNAi plants are predominantly associated with the mediation of various stresses and cell senescence, consistent with an indirect role for Arabidopsis Gβ in development where the orthologous gene ablation mainly confers altered cell proliferation. We also elaborate our speculative working hypothesis that cell division is a type of stress and as such due to impairment in responding to stress in the G protein mutants, manifests as altered morphology and architecture but not an altered body plan or organ identities.
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Affiliation(s)
- Daisuke Urano
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, 117604, Singapore.
| | - Richalynn Leong
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, 117604, Singapore
| | - Ting-Ying Wu
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, 117604, Singapore
| | - Alan M Jones
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599-3280, USA; Department of Pharmacology, University of North Carolina, Chapel Hill, NC, 27599-3280, USA
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4
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Zhang H, Nielsen AL, Strømgaard K. Recent achievements in developing selective Gqinhibitors. Med Res Rev 2019; 40:135-157. [DOI: 10.1002/med.21598] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 04/09/2019] [Accepted: 04/26/2019] [Indexed: 02/06/2023]
Affiliation(s)
- Hang Zhang
- Key Laboratory of Advanced Drug Preparation Technologies, Ministry of Education, Co‐innovation Center of Henan Province for New Drug R&D and Preclinical Safety, and School of Pharmaceutical SciencesZhengzhou UniversityZhengzhou Henan China
| | - Alexander L. Nielsen
- Department of Drug Design and Pharmacology, Center for BiopharmaceuticalsUniversity of CopenhagenCopenhagen Denmark
| | - Kristian Strømgaard
- Department of Drug Design and Pharmacology, Center for BiopharmaceuticalsUniversity of CopenhagenCopenhagen Denmark
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5
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Ha JH, Kim JH, Kim SG, Sim HJ, Lee G, Halitschke R, Baldwin IT, Kim JI, Park CM. Shoot phytochrome B modulates reactive oxygen species homeostasis in roots via abscisic acid signaling in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 94:790-798. [PMID: 29570885 DOI: 10.1111/tpj.13902] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 02/26/2018] [Accepted: 03/02/2018] [Indexed: 05/14/2023]
Abstract
Underground roots normally reside in darkness. However, they are often exposed to ambient light that penetrates through cracks in the soil layers which can occur due to wind, heavy rain or temperature extremes. In response to light exposure, roots produce reactive oxygen species (ROS) which promote root growth. It is known that ROS-induced growth promotion facilitates rapid escape of the roots from non-natural light. Meanwhile, long-term exposure of the roots to light elicits a ROS burst, which causes oxidative damage to cellular components, necessitating that cellular levels of ROS should be tightly regulated in the roots. Here we demonstrate that the red/far-red light photoreceptor phytochrome B (phyB) stimulates the biosynthesis of abscisic acid (ABA) in the shoots, and notably the shoot-derived ABA signals induce a peroxidase-mediated ROS detoxification reaction in the roots. Accordingly, while ROS accumulate in the roots of the phyb mutant that exhibits reduced primary root growth in the light, such an accumulation of ROS did not occur in the dark-grown phyb roots that exhibited normal growth. These observations indicate that mobile shoot-to-root ABA signaling links shoot phyB-mediated light perception with root ROS homeostasis to help roots adapt to unfavorable light exposure. We propose that ABA-mediated shoot-to-root phyB signaling contributes to the synchronization of shoot and root growth for optimal propagation and performance in plants.
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Affiliation(s)
- Jun-Ho Ha
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea
| | - Ju-Heon Kim
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea
| | - Sang-Gyu Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Korea
| | - Hee-Jung Sim
- Gyeongnam Department of Environmental Toxicology and Chemistry, Korea Institute of Toxicology, Gyeongnam, 52834, Korea
| | - Gisuk Lee
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Jena, 07745, Germany
| | - Rayko Halitschke
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Jena, 07745, Germany
| | - Ian T Baldwin
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Jena, 07745, Germany
| | - Jeong-Il Kim
- Department of Biotechnology and Kumho Life Science Laboratory, Chonnam National University, Gwangju, 61186, Korea
| | - Chung-Mo Park
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea
- Plant Genomics and Breeding Institute, Seoul National University, Seoul, 08826, Korea
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6
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Pandey S, Vijayakumar A. Emerging themes in heterotrimeric G-protein signaling in plants. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2018; 270:292-300. [PMID: 29576082 DOI: 10.1016/j.plantsci.2018.03.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 01/18/2018] [Accepted: 03/01/2018] [Indexed: 05/28/2023]
Abstract
Heterotrimeric G-proteins are key signaling components involved during the regulation of a multitude of growth and developmental pathways in all eukaryotes. Although the core proteins (Gα, Gβ, Gγ subunits) and their basic biochemistries are conserved between plants and non-plant systems, seemingly different inherent properties of specific components, altered wirings of G-protein network architectures, and the presence of novel receptors and effector proteins make plant G-protein signaling mechanisms somewhat distinct from the well-established animal paradigm. G-protein research in plants is getting a lot of attention recently due to the emerging roles of these proteins in controlling many agronomically important traits. New findings on both canonical and novel G-protein components and their conserved and unique signaling mechanisms are expected to improve our understanding of this important module in affecting critical plant growth and development pathways and eventually their utilization to produce plants for the future needs. In this review, we briefly summarize what is currently known in plant G-protein research, describe new findings and how they are changing our perceptions of the field, and discuss important issues that still need to be addressed.
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Affiliation(s)
- Sona Pandey
- Donald Danforth Plant Science Center, 975 N. Warson Road, St. Louis, MO, 63132, USA.
| | - Anitha Vijayakumar
- Donald Danforth Plant Science Center, 975 N. Warson Road, St. Louis, MO, 63132, USA
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7
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Ferrero-Serrano Á, Su Z, Assmann SM. Illuminating the role of the Gα heterotrimeric G protein subunit, RGA1, in regulating photoprotection and photoavoidance in rice. PLANT, CELL & ENVIRONMENT 2018; 41:451-468. [PMID: 29216416 DOI: 10.1111/pce.13113] [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: 10/06/2017] [Revised: 11/19/2017] [Accepted: 11/21/2017] [Indexed: 05/22/2023]
Abstract
We studied physiological mechanisms of photoavoidance and photoprotection of a dwarf rice mutant with erect leaves, d1, in which the RGA1 gene, which encodes the Gα subunit of the heterotrimeric G protein, is non-functional. Leaves of d1 exhibit lower leaf temperature and higher photochemical reflectance index relative to wild type (WT), indicative of increased photoavoidance and more efficient light harvesting. RNA sequencing analysis of flag leaves revealed that messenger RNA levels of genes encoding heat shock proteins, enzymes associated with chlorophyll breakdown, and ROS scavengers were down-regulated in d1. By contrast, genes encoding proteins associated with light harvesting, Photosystem II, cyclic electron transport, Photosystem I, and chlorophyll biosynthesis were up-regulated in d1. Consistent with these observations, when WT and d1 plants were experimentally subjected to the same light intensity, d1 plants exhibited a greater capacity to dissipate excess irradiance (increased nonphotochemical quenching) relative to WT. The increased capacity in d1 for both photoavoidance and photoprotection reduced sustained photoinhibitory damage, as revealed by a higher Fv /Fm . We therefore propose RGA1 as a regulator of photoavoidance and photoprotection mechanisms in rice and highlight the prospect of exploiting modulation of heterotrimeric G protein signalling to increase these characteristics and improve the yield of cereals in the event of abiotic stress.
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Affiliation(s)
- Ángel Ferrero-Serrano
- Biology Department, Penn State University, 208 Mueller Laboratory, University Park, PA, 16802, USA
| | - Zhao Su
- Biology Department, Penn State University, 208 Mueller Laboratory, University Park, PA, 16802, USA
| | - Sarah M Assmann
- Biology Department, Penn State University, 208 Mueller Laboratory, University Park, PA, 16802, USA
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8
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Kumar R, Sharma A, Chandel I, Bisht NC. Pattern of expression and interaction specificity of multiple G-protein beta (Gβ) subunit isoforms with their potential target proteins reveal functional dominance of BjuGβ1 in the allotetraploid Brassica juncea. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2017; 118:22-30. [PMID: 28603081 DOI: 10.1016/j.plaphy.2017.05.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 05/17/2017] [Accepted: 05/25/2017] [Indexed: 06/07/2023]
Abstract
Heterotrimeric G-protein, consisting Gα, Gβ and Gγ subunits, interacts with various upstream and downstream effector (target) proteins to regulate a large array of conserved and species-specific biological functions. The targets of G-protein components are recently reported in model plant Arabidopsis thaliana; however limited information is available from crop species. In this study, we utilized yeast two-hybrid (Y2H) assay to screen the diversity of interacting partners of multiple Gβ subunit isoforms from allotetraploid Brassica juncea, a globally important oilseed and vegetable crop. The three BjuGβ genes (BjuGβ1-3), resulted from whole genome triplication event in Brassica lineage, showed distinct expression profile during plant developmental stages with maximal transcript abundance during reproductive stages. Protein-protein interaction of three BjuGβ proteins (bait) against the Y2H cDNA library (prey) identified a total of 14 and 1 non-redundant targets for BjuGβ1 and BjuGβ2, whereas BjuGβ3 screening surprisingly did not yield any genuine target, thereby suggesting functional dominance of BjuGβ1. The triplicated BjuGβ isoforms showed a high degree of interaction strength and specificity with the identified target proteins, which are known to be involved in diverse biological functions in plants. qRT-PCR analysis further indicated that the expression of BjuGβ-target genes was developmentally regulated under various tissue types studied and showed a high degree of co-expression pattern with the BjuGβ genes, particularly during flower and silique development in B. juncea. Taken together, our data provides novel insights on pattern of expression and interaction specificity governing functional divergence of multiple Gβ subunit proteins in polyploid B. juncea.
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Affiliation(s)
- Roshan Kumar
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Aprajita Sharma
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Ishita Chandel
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Naveen C Bisht
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India.
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9
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Ge XM, Cai HL, Lei X, Zhou X, Yue M, He JM. Heterotrimeric G protein mediates ethylene-induced stomatal closure via hydrogen peroxide synthesis in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 82:138-50. [PMID: 25704455 DOI: 10.1111/tpj.12799] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 02/10/2015] [Accepted: 02/11/2015] [Indexed: 05/18/2023]
Abstract
Heterotrimeric G proteins function as key players in hydrogen peroxide (H2O2) production in plant cells, but whether G proteins mediate ethylene-induced H2O2 production and stomatal closure are not clear. Here, evidences are provided to show the Gα subunit GPA1 as a missing link between ethylene and H2O2 in guard cell ethylene signalling. In wild-type leaves, ethylene-triggered H2O2 synthesis and stomatal closure were dependent on activation of Gα. GPA1 mutants showed the defect of ethylene-induced H2O2 production and stomatal closure, whereas wGα and cGα overexpression lines showed faster stomatal closure and H2O2 production in response to ethylene. Ethylene-triggered H2O2 generation and stomatal closure were impaired in RAN1, ETR1, ERS1 and EIN4 mutants but not impaired in ETR2 and ERS2 mutants. Gα activator and H2O2 rescued the defect of RAN1 and EIN4 mutants or etr1-3 in ethylene-induced H2O2 production and stomatal closure, but only rescued the defect of ERS1 mutants or etr1-1 and etr1-9 in ethylene-induced H2O2 production. Stomata of CTR1 mutants showed constitutive H2O2 production and stomatal closure, but which could be abolished by Gα inhibitor. Stomata of EIN2, EIN3 and ARR2 mutants did not close in responses to ethylene, Gα activator or H2O2, but do generate H2O2 following challenge of ethylene or Gα activator. The data indicate that Gα mediates ethylene-induced stomatal closure via H2O2 production, and acts downstream of RAN1, ETR1, ERS1, EIN4 and CTR1 and upstream of EIN2, EIN3 and ARR2. The data also show that ETR1 and ERS1 mediate both ethylene and H2O2 signalling in guard cells.
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Affiliation(s)
- Xiao-Min Ge
- School of Life Sciences, Shaanxi Normal University, Xi'an, 710062, China; School of Life Sciences, Northwest University, Xi'an, 710069, China
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10
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Arabidopsis G-protein β subunit AGB1 interacts with NPH3 and is involved in phototropism. Biochem Biophys Res Commun 2014; 445:54-7. [DOI: 10.1016/j.bbrc.2014.01.106] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 01/22/2014] [Indexed: 01/12/2023]
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11
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Rodriguez-López J, Martínez-Centeno C, Padmanaban A, Guillén G, Olivares JE, Stefano G, Lledías F, Ramos F, Ghabrial SA, Brandizzi F, Rocha-Sosa M, Díaz-Camino C, Sanchez F. Nodulin 22, a novel small heat-shock protein of the endoplasmic reticulum, is linked to the unfolded protein response in common bean. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2014; 27:18-29. [PMID: 24073881 PMCID: PMC4028047 DOI: 10.1094/mpmi-07-13-0200-r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The importance of plant small heat shock proteins (sHsp) in multiple cellular processes has been evidenced by their unusual abundance and diversity; however, little is known about their biological role. Here, we characterized the in vitro chaperone activity and subcellular localization of nodulin 22 of Phaseolus vulgaris (PvNod22; common bean) and explored its cellular function through a virus-induced gene silencing-based reverse genetics approach. We established that PvNod22 facilitated the refolding of a model substrate in vitro, suggesting that it acts as a molecular chaperone in the cell. Through microscopy analyses of PvNod22, we determined its localization in the endoplasmic reticulum (ER). Furthermore, we found that silencing of PvNod22 resulted in necrotic lesions in the aerial organs of P. vulgaris plants cultivated under optimal conditions and that downregulation of PvNod22 activated the ER-unfolded protein response (UPR) and cell death. We also established that PvNod22 expression in wild-type bean plants was modulated by abiotic stress but not by chemicals that trigger the UPR, indicating PvNod22 is not under UPR control. Our results suggest that the ability of PvNod22 to suppress protein aggregation contributes to the maintenance of ER homeostasis, thus preventing the induction of cell death via UPR in response to oxidative stress during plant-microbe interactions.
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Abstract
Investigators studying G protein-coupled signaling--often called the best-understood pathway in the world owing to intense research in medical fields--have adopted plants as a new model to explore the plasticity and evolution of G signaling. Much research on plant G signaling has not disappointed. Although plant cells have most of the core elements found in animal G signaling, differences in network architecture and intrinsic properties of plant G protein elements make G signaling in plant cells distinct from the animal paradigm. In contrast to animal G proteins, plant G proteins are self-activating, and therefore regulation of G activation in plants occurs at the deactivation step. The self-activating property also means that plant G proteins do not need and therefore do not have typical animal G protein-coupled receptors. Targets of activated plant G proteins, also known as effectors, are unlike effectors in animal cells. The simpler repertoire of G signal elements in Arabidopsis makes G signaling easier to manipulate in a multicellular context.
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Affiliation(s)
- Daisuke Urano
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Alan M. Jones
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
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13
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Urano D, Chen JG, Botella JR, Jones AM. Heterotrimeric G protein signalling in the plant kingdom. Open Biol 2013. [PMID: 23536550 DOI: 10.1098/rsob.12.0186] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/08/2023] Open
Abstract
In animals, heterotrimeric G proteins, comprising α-, β-and γ-subunits, perceive extracellular stimuli through cell surface receptors, and transmit signals to ion channels, enzymes and other effector proteins to affect numerous cellular behaviours. In plants, G proteins have structural similarities to the corresponding molecules in animals but transmit signals by atypical mechanisms and effector proteins to control growth, cell proliferation, defence, stomate movements, channel regulation, sugar sensing and some hormonal responses. In this review, we summarize the current knowledge on the molecular regulation of plant G proteins, their effectors and the physiological functions studied mainly in two model organisms: Arabidopsis thaliana and rice (Oryza sativa). We also look at recent progress on structural analyses, systems biology and evolutionary studies.
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Affiliation(s)
- Daisuke Urano
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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14
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Urano D, Chen JG, Botella JR, Jones AM. Heterotrimeric G protein signalling in the plant kingdom. Open Biol 2013; 3:120186. [PMID: 23536550 PMCID: PMC3718340 DOI: 10.1098/rsob.120186] [Citation(s) in RCA: 178] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 03/05/2013] [Indexed: 12/18/2022] Open
Abstract
In animals, heterotrimeric G proteins, comprising α-, β-and γ-subunits, perceive extracellular stimuli through cell surface receptors, and transmit signals to ion channels, enzymes and other effector proteins to affect numerous cellular behaviours. In plants, G proteins have structural similarities to the corresponding molecules in animals but transmit signals by atypical mechanisms and effector proteins to control growth, cell proliferation, defence, stomate movements, channel regulation, sugar sensing and some hormonal responses. In this review, we summarize the current knowledge on the molecular regulation of plant G proteins, their effectors and the physiological functions studied mainly in two model organisms: Arabidopsis thaliana and rice (Oryza sativa). We also look at recent progress on structural analyses, systems biology and evolutionary studies.
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Affiliation(s)
- Daisuke Urano
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Jin-Gui Chen
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - José Ramón Botella
- Plant Genetic Engineering Laboratory, School of Agriculture and Food Sciences, University of Queensland, Brisbane, Queensland 4072, Australia
| | - Alan M. Jones
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC 27599, USA
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15
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He JM, Ma XG, Zhang Y, Sun TF, Xu FF, Chen YP, Liu X, Yue M. Role and interrelationship of Gα protein, hydrogen peroxide, and nitric oxide in ultraviolet B-induced stomatal closure in Arabidopsis leaves. PLANT PHYSIOLOGY 2013; 161:1570-83. [PMID: 23341360 PMCID: PMC3585617 DOI: 10.1104/pp.112.211623] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2012] [Accepted: 01/18/2013] [Indexed: 05/18/2023]
Abstract
Heterotrimeric G proteins have been shown to transmit ultraviolet B (UV-B) signals in mammalian cells, but whether they also transmit UV-B signals in plant cells is not clear. In this paper, we report that 0.5 W m(-2) UV-B induces stomatal closure in Arabidopsis (Arabidopsis thaliana) by eliciting a cascade of intracellular signaling events including Gα protein, hydrogen peroxide (H2O2), and nitric oxide (NO). UV-B triggered a significant increase in H2O2 or NO levels associated with stomatal closure in the wild type, but these effects were abolished in the single and double mutants of AtrbohD and AtrbohF or in the Nia1 mutants, respectively. Furthermore, we found that UV-B-mediated H2O2 and NO generation are regulated by GPA1, the Gα-subunit of heterotrimeric G proteins. UV-B-dependent H2O2 and NO accumulation were nullified in gpa1 knockout mutants but enhanced by overexpression of a constitutively active form of GPA1 (cGα). In addition, exogenously applied H2O2 or NO rescued the defect in UV-B-mediated stomatal closure in gpa1 mutants, whereas cGα AtrbohD/AtrbohF and cGα nia1 constructs exhibited a similar response to AtrbohD/AtrbohF and Nia1, respectively. Finally, we demonstrated that Gα activation of NO production depends on H2O2. The mutants of AtrbohD and AtrbohF had impaired NO generation in response to UV-B, but UV-B-induced H2O2 accumulation was not impaired in Nia1. Moreover, exogenously applied NO rescued the defect in UV-B-mediated stomatal closure in the mutants of AtrbohD and AtrbohF. These findings establish a signaling pathway leading to UV-B-induced stomatal closure that involves GPA1-dependent activation of H2O2 production and subsequent Nia1-dependent NO accumulation.
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Affiliation(s)
- Jun-Min He
- School of Life Sciences, Shaanxi Normal University, Xi'an 710062, China.
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16
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Tsugama D, Liu H, Liu S, Takano T. Arabidopsis heterotrimeric G protein β subunit interacts with a plasma membrane 2C-type protein phosphatase, PP2C52. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:2254-60. [PMID: 23058975 DOI: 10.1016/j.bbamcr.2012.10.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 09/29/2012] [Accepted: 10/01/2012] [Indexed: 11/24/2022]
Abstract
Heterotrimeric G proteins (Gα, Gβ, Gγ) play important roles in signal transduction among various eukaryotic species. G proteins transmit signals by regulating the activities of effector proteins, but only a few Gβ-interacting effectors have been identified in plants. Here we show by a yeast two-hybrid screen that a putative myristoylated 2C-type protein phosphatase, PP2C52, is an Arabidopsis Gβ (AGB1)-interacting partner. The interaction between AGB1 and PP2C52 was confirmed by an in vitro pull-down assay and a bimolecular fluorescence complementation assay. PP2C52 transcripts were detected in many tissues. PP2C52 was localized to the plasma membrane and a mutation in the putative myristoylation site of PP2C52 disrupted its plasma membrane localization. Our results suggest that PP2C52 interacts with AGB1 on the plasma membrane and transmits signals via dephosphorylation of other proteins.
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Affiliation(s)
- Daisuke Tsugama
- Asian Natural Environmental Science Center, The University of Tokyo, Japan.
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17
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Zhang H, Gao Z, Zheng X, Zhang Z. The role of G-proteins in plant immunity. PLANT SIGNALING & BEHAVIOR 2012; 7:1284-8. [PMID: 22895102 PMCID: PMC3493415 DOI: 10.4161/psb.21431] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Heterotrimeric G-proteins play an important regulatory role in multiple physiological processes, including the plant immune response, and substantial progress has been made in elucidating the G-protein-mediated defense-signaling network. This mini-review discusses the importance of G-proteins in plant immunity. We also provide an overview of how G-proteins affect plant cell death and stomatal movement. Our recent studies demonstrated that G-proteins are involved in signal transduction and induction of stomatal closure and defense responses. We also discuss future directions for G-protein signaling studies involving plant immunity.
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Affiliation(s)
- Huajian Zhang
- Department of Plant Pathology; College of Plant Protection; Nanjing Agricultural University; Key Laboratory of Monitoring and Management of Crop Diseases and Pest Insects; Ministry of Agriculture; Nanjing, China
- Department of Plant Pathology; Anhui Agricultural University; Hefei, China
| | - Zhimou Gao
- Department of Plant Pathology; Anhui Agricultural University; Hefei, China
| | - Xiaobo Zheng
- Department of Plant Pathology; College of Plant Protection; Nanjing Agricultural University; Key Laboratory of Monitoring and Management of Crop Diseases and Pest Insects; Ministry of Agriculture; Nanjing, China
| | - Zhengguang Zhang
- Department of Plant Pathology; College of Plant Protection; Nanjing Agricultural University; Key Laboratory of Monitoring and Management of Crop Diseases and Pest Insects; Ministry of Agriculture; Nanjing, China
- Correspondence to: Zhengguang Zhang,
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18
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Fox AR, Soto GC, Jones AM, Casal JJ, Muschietti JP, Mazzella MA. cry1 and GPA1 signaling genetically interact in hook opening and anthocyanin synthesis in Arabidopsis. PLANT MOLECULAR BIOLOGY 2012; 80:315-24. [PMID: 22855128 PMCID: PMC4871592 DOI: 10.1007/s11103-012-9950-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Accepted: 07/23/2012] [Indexed: 05/08/2023]
Abstract
While studying blue light-independent effects of cryptochrome 1 (cry1) photoreceptor, we observed premature opening of the hook in cry1 mutants grown in complete darkness, a phenotype that resembles the one described for the heterotrimeric G-protein α subunit (GPA1) null mutant gpa1. Both cry1 and gpa1 also showed reduced accumulation of anthocyanin under blue light. These convergent gpa1 and cry1 phenotypes required the presence of sucrose in the growth media and were not additive in the cry1 gpa1 double mutant, suggesting context-dependent signaling convergence between cry1 and GPA1 signaling pathways. Both, gpa1 and cry1 mutants showed reduced GTP-binding activity. The cry1 mutant showed wild-type levels of GPA1 mRNA or GPA1 protein. However, an anti-transducin antibody (AS/7) typically used for plant Gα proteins, recognized a 54 kDa band in the wild type but not in gpa1 and cry1 mutants. We propose a model where cry1-mediated post-translational modification of GPA1 alters its GTP-binding activity.
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Affiliation(s)
- Ana R. Fox
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Dr. Hector Torres, (INGEBI-CONICET), Vuelta de Obligado 2490, 1428 Buenos Aires, Argentina
| | - Gabriela C. Soto
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Dr. Hector Torres, (INGEBI-CONICET), Vuelta de Obligado 2490, 1428 Buenos Aires, Argentina
| | - Alan M. Jones
- Departments of Biology and Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jorge J. Casal
- IFEVA, Facultad de Agronomía, Universidad de Buenos Aires and CONICET, 1417 Buenos Aires, Argentina
- Fundacion Instituto Leloir, 1405 Buenos Aires, Argentina
| | - Jorge P. Muschietti
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Dr. Hector Torres, (INGEBI-CONICET), Vuelta de Obligado 2490, 1428 Buenos Aires, Argentina
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina
| | - María A. Mazzella
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Dr. Hector Torres, (INGEBI-CONICET), Vuelta de Obligado 2490, 1428 Buenos Aires, Argentina
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19
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Hao LH, Wang WX, Chen C, Wang YF, Liu T, Li X, Shang ZL. Extracellular ATP promotes stomatal opening of Arabidopsis thaliana through heterotrimeric G protein α subunit and reactive oxygen species. MOLECULAR PLANT 2012; 5:852-64. [PMID: 22138967 DOI: 10.1093/mp/ssr095] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
In recent years, adenosine tri-phosphate (ATP) has been reported to exist in apoplasts of plant cells as a signal molecule. Extracellular ATP (eATP) plays important roles in plant growth, development, and stress tolerance. Here, extracellular ATP was found to promote stomatal opening of Arabidopsis thaliana in light and darkness. ADP, GTP, and weakly hydrolyzable ATP analogs (ATPγS, Bz-ATP, and 2meATP) showed similar effects, whereas AMP and adenosine did not affect stomatal movement. Apyrase inhibited stomatal opening. ATP-promoted stomatal opening was blocked by an NADPH oxidase inhibitor (diphenylene iodonium) or deoxidizer (dithiothreitol), and was impaired in null mutant of NADPH oxidase (atrbohD/F). Added ATP triggered ROS generation in guard cells via NADPH oxidase. ATP also induced Ca(2+) influx and H(+) efflux in guard cells. In atrbohD/F, ATP-induced ion flux was strongly suppressed. In null mutants of the heterotrimeric G protein α subunit, ATP-promoted stomatal opening, cytoplasmic ROS generation, Ca(2+) influx, and H(+) efflux were all suppressed. These results indicated that eATP-promoted stomatal opening possibly involves the heterotrimeric G protein, ROS, cytosolic Ca(2+), and plasma membrane H(+)-ATPase.
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Affiliation(s)
- Li-Hua Hao
- Key Laboratory of Molecular and Cell Biology of Hebei Province, College of Life Sciences, Hebei Normal University, Shijiazhuang, PR China
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20
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Jiang K, Frick-Cheng A, Trusov Y, Delgado-Cerezo M, Rosenthal DM, Lorek J, Panstruga R, Booker FL, Botella JR, Molina A, Ort DR, Jones AM. Dissecting Arabidopsis Gβ signal transduction on the protein surface. PLANT PHYSIOLOGY 2012; 159:975-83. [PMID: 22570469 PMCID: PMC3387721 DOI: 10.1104/pp.112.196337] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The heterotrimeric G-protein complex provides signal amplification and target specificity. The Arabidopsis (Arabidopsis thaliana) Gβ-subunit of this complex (AGB1) interacts with and modulates the activity of target cytoplasmic proteins. This specificity resides in the structure of the interface between AGB1 and its targets. Important surface residues of AGB1, which were deduced from a comparative evolutionary approach, were mutated to dissect AGB1-dependent physiological functions. Analysis of the capacity of these mutants to complement well-established phenotypes of Gβ-null mutants revealed AGB1 residues critical for specific AGB1-mediated biological processes, including growth architecture, pathogen resistance, stomata-mediated leaf-air gas exchange, and possibly photosynthesis. These findings provide promising new avenues to direct the finely tuned engineering of crop yield and traits.
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21
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Chen Y, Brandizzi F. AtIRE1A/AtIRE1B and AGB1 independently control two essential unfolded protein response pathways in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 69:266-77. [PMID: 21914012 DOI: 10.1111/j.1365-313x.2011.04788.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The endoplasmic reticulum (ER) has the ability to maintain the balance between demand for and synthesis of secretory proteins. To ensure protein-folding homeostasis in the ER, cells invoke signaling pathways known as the unfolded protein response (UPR). To initiate UPR, yeasts largely rely on a conserved sensor, IRE1. In metazoans, there are at least three independent UPR signalling pathways. Some UPR transducers have been identified in plants, but no genetic interaction among them has yet been examined. The Arabidopsis genome encodes two IRE1 sequence homologs, AtIRE1A and AtIRE1B. Here we provide evidence that AtIRE1A and AtIRE1B have overlapping functions that are essential for the plant UPR. A double mutant of AtIRE1A and AtIRE1B, atire1a atire1b, showed reduced ER stress tolerance and a compromised UPR activation phenotype. We have also established that Arabidopsis AGB1, a subunit of the ubiquitous heterotrimeric GTP-binding protein family, and AtIRE1A/AtIRE1B independently control two essential plant UPR pathways. By demonstrating that atire1a atire1b has a short root phenotype that is enhanced by an agb1 loss-of-function mutation, we have identified a role for UPR transducers in organ growth regulation.
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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
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22
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Utsunomiya Y, Samejima C, Takayanagi Y, Izawa Y, Yoshida T, Sawada Y, Fujisawa Y, Kato H, Iwasaki Y. Suppression of the rice heterotrimeric G protein β-subunit gene, RGB1, causes dwarfism and browning of internodes and lamina joint regions. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 67:907-16. [PMID: 21585570 DOI: 10.1111/j.1365-313x.2011.04643.x] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
In the present study, we investigated the function of the heterotrimeric G protein β-subunit (Gβ) gene (RGB1) in rice. RGB1 knock-down lines were generated in the wild type and d1-5, a mutant deficient for the heterotrimeric G protein α-subunit (Gα) gene (RGA1). Both transgenic lines showed browning of the lamina joint regions and nodes that could be attributed to a reduction of RGB1 function, as the abnormality was not observed in d1-5. The RGB1 knock-down lines generated in d1-5 were shorter, suggesting RGB1 to be a positive regulator of cellular proliferation, in addition to RGA1. The number of sterile seeds also increased in both RGB1 knock-down lines. These results suggest that Gβγ and Gα cooperatively function in cellular proliferation and seed fertility. We discuss the potential predominant role of RGB1 in G protein signaling in rice.
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Affiliation(s)
- Yuzuko Utsunomiya
- Department of Bioscience, Fukui Prefectural University, 4-1-1 Matsuoka Kenjyojima, Eiheiji-cho, Yoshida-gun, Fukui 910-1195, Japan
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23
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Shi LX, Hall M, Funk C, Schröder WP. Photosystem II, a growing complex: updates on newly discovered components and low molecular mass proteins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:13-25. [PMID: 21907181 DOI: 10.1016/j.bbabio.2011.08.008] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Revised: 08/19/2011] [Accepted: 08/23/2011] [Indexed: 12/12/2022]
Abstract
Photosystem II is a unique complex capable of absorbing light and splitting water. The complex has been thoroughly studied and to date there are more than 40 proteins identified, which bind to the complex either stably or transiently. Another special feature of this complex is the unusually high content of low molecular mass proteins that represent more than half of the proteins. In this review we summarize the recent findings on the low molecular mass proteins (<15kDa) and present an overview of the newly identified components as well. We have also performed co-expression analysis of the genes encoding PSII proteins to see if the low molecular mass proteins form a specific sub-group within the Photosystem II complex. Interestingly we found that the chloroplast-localized genes encoding PSII proteins display a different response to environmental and stress conditions compared to the nuclear localized genes. This article is part of a Special Issue entitled: Photosystem II.
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Affiliation(s)
- Lan-Xin Shi
- Department of Plant Biology, University of California-Davis, One Shields Avenue, Davis, CA 95616, USA
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24
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Doğramacı M, Horvath DP, Christoffers MJ, Anderson JV. Dehydration and vernalization treatments identify overlapping molecular networks impacting endodormancy maintenance in leafy spurge crown buds. Funct Integr Genomics 2011; 11:611-26. [PMID: 21789635 DOI: 10.1007/s10142-011-0239-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Revised: 06/29/2011] [Accepted: 07/03/2011] [Indexed: 11/30/2022]
Abstract
Leafy spurge (Euphorbia esula L.) is a herbaceous perennial weed that reproduces vegetatively from an abundance of underground adventitious buds (UABs), which undergo well-defined phases of seasonal dormancy (para-, endo-, and ecodormancy). In this study, the effects of dehydration stress on vegetative growth and flowering potential from endodormant UABs of leafy spurge was monitored. Further, microarray analysis was used to identify critical signaling pathways of transcriptome profiles associated with endodormancy maintenance in UABs. Surprisingly, only 3-day of dehydration stress is required to break the endodormant phase in UABs; however, the dehydration-stress treatment did not induce flowering. Previous studies have shown that prolonged cold treatment of UABs breaks endodormancy and induces a vernalization response leading to flowering. Thus, in this study, comparing transcriptome data from UABs exposed to short-term dehydration and vernalization provided a unique approach to identify overlapping molecular mechanisms involved in endodormancy maintenance and floral competence. Analysis of transcriptome data associated with breaking endodormancy by both environmental treatments identified LEC1, PHOTOSYSTEM I RC, and brassinosteroids as common central hubs of upregulated genes, while DREB1A, CBF2, GPA1, MYC2, bHLH, BZIP, and flavonoids were identified as common central hubs of downregulated genes. The majority of over-represented gene sets common to breaking endodormancy by dehydration stress and vernalization were downregulated and included pathways involved in hormone signaling, chromatin modification, and circadian rhythm. Additionally, the over-represented gene sets highlighted pathways involved in starch and sugar degradation and biogenesis of carbon skeletons, suggesting a high metabolic activity is necessary during the endodormant phase. The data presented in this study helped to refine our previous model for dormancy regulation.
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Affiliation(s)
- Münevver Doğramacı
- Biosciences Research Laboratory, USDA-Agricultural Research Service, 1605 Albrecht Blvd. N., Fargo, ND 58102-2765, USA
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25
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26
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Wangdi T, Uppalapati SR, Nagaraj S, Ryu CM, Bender CL, Mysore KS. A virus-induced gene silencing screen identifies a role for Thylakoid Formation1 in Pseudomonas syringae pv tomato symptom development in tomato and Arabidopsis. PLANT PHYSIOLOGY 2010; 152:281-92. [PMID: 19915014 PMCID: PMC2799363 DOI: 10.1104/pp.109.148106] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2009] [Accepted: 11/09/2009] [Indexed: 05/20/2023]
Abstract
Pseudomonas syringae pv tomato DC3000 (Pst DC3000), which causes disease in tomato (Solanum lycopersicum) and Arabidopsis (Arabidopsis thaliana), produces coronatine (COR), a non-host-specific phytotoxin. COR, which functions as a jasmonate mimic, is required for full virulence of Pst DC3000 and for the induction of chlorosis in host plants. Previous genetic screens based on insensitivity to COR and/or methyl jasmonate identified several potential targets for COR and methyl jasmonate. In this study, we utilized Nicotiana benthamiana and virus-induced gene silencing to individually reduce the expression of over 4,000 genes. The silenced lines of N. benthamiana were then screened for altered responses to purified COR. Using this forward genetics approach, several genes were identified with altered responses to COR. These were designated as ALC (for altered COR response) genes. When silenced, one of the identified genes, ALC1, produced a hypersensitive/necrosis-like phenotype upon COR application in a Coronatine-Insensitive1 (COI1)-dependent manner. To understand the involvement of ALC1 during the Pst DC3000-host interaction, we used the nucleotide sequence of ALC1 and identified its ortholog in Arabidopsis (Thylakoid Formation1 [THF1]) and tomato (SlALC1). In pathogenicity assays performed on Arabidopsis thf1 mutant and SlALC1-silenced tomato plants, Pst DC3000 induced accelerated coalescing necrotic lesions. Furthermore, we showed that COR affects ALC1 localization in chloroplasts in a COI1-dependent manner. In conclusion, our results show that the virus-induced gene silencing-based forward genetic screen has the potential to identify new players in COR signaling and disease-associated necrotic cell death.
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Steffens B, Sauter M. Heterotrimeric G protein signaling is required for epidermal cell death in rice. PLANT PHYSIOLOGY 2009; 151:732-40. [PMID: 19656904 PMCID: PMC2754641 DOI: 10.1104/pp.109.142133] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
In rice (Oryza sativa) adventitious root primordia are formed at the nodes as part of normal development. Upon submergence of rice plants, adventitious roots emerge from the nodes preceded by death of epidermal cells above the root primordia. Cell death is induced by ethylene and mediated by hydrogen peroxide (H(2)O(2)). Pharmacological experiments indicated that epidermal cell death was dependent on signaling through G proteins. Treatment with GTP-gamma-S induced epidermal cell death, whereas GDP-beta-S partially inhibited ethylene-induced cell death. The dwarf1 (d1) mutant of rice has repressed expression of the Galpha subunit RGA1 of heterotrimeric G protein. In d1 plants, cell death in response to ethylene and H(2)O(2) was nearly completely abolished, indicating that signaling through Galpha is essential. Ethylene and H(2)O(2) were previously shown to alter gene expression in epidermal cells that undergo cell death. Transcriptional regulation was not generally affected in the d1 mutant, indicating that altered gene expression is not sufficient to trigger cell death in the absence of Galpha. Analysis of genes encoding proteins related to G protein signaling revealed that four small GTPase genes, two GTPase-activating protein genes, and one GDP dissociation inhibitor gene but not RGA1 were differentially expressed in epidermal cells above adventitious roots, indicating that Galpha activity is regulated posttranscriptionally.
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Affiliation(s)
- Bianka Steffens
- Physiologie und Entwicklungsbiologie der Pflanzen, Botanisches Institut, Universität Kiel, 24118 Kiel, Germany
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Reina-Pinto JJ, Yephremov A. Lipid determinants of cell death. PLANT SIGNALING & BEHAVIOR 2009; 4:625-628. [PMID: 19820339 PMCID: PMC2710557 DOI: 10.4161/psb.4.7.8923] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2009] [Accepted: 05/04/2009] [Indexed: 05/24/2023]
Abstract
Lipids produced by the epidermis serve a number of protective functions, and also act as messengers which activate plant defense responses. The fatty acid elongases which catalyze the formation of very long-chain fatty acids, may be instrumental in the remodeling of the various classes of epidermal lipids, and they also provide a means with which to further investigate the defense mechanisms. In a recent publication, we reported that the epidermal mis-expression of FATTY ACID ELONGASE1 (FAE1) in the Arabidopsis plant both increased the levels of very long-chain fatty acids in various lipid classes, and unexpectedly induced a cell-type specific cell death program in trichome cells, giving the plants a glabrous appearance. Using these plants as a model system for a fatty acid-induced cell death (lipoapoptosis), and a platform for the chemical genetic screen, we identified trichome death inhibitors in the glycerophospholipid fatty acyl remodeling pathway: phospholipase A2 inhibitors, aristolochic acid and bromoenol lactone, as well as the putative lysophospholipid acyltransferase inhibitor, clofibrate. Herein, and due to space limitations, we will briefly discuss these results and the different ways in which the appearance of increasing chain-length fatty acids is likely to regulate the cellular life-or-death switch. The death receptor hypothesis implies the existence of a bioactive lipid ligand(s), the functionality of which is determined by phosphorylation, acyl chain length and saturation.
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Zhang L, Wei Q, Wu W, Cheng Y, Hu G, Hu F, Sun Y, Zhu Y, Sakamoto W, Huang J. Activation of the heterotrimeric G protein alpha-subunit GPA1 suppresses the ftsh-mediated inhibition of chloroplast development in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2009; 58:1041-53. [PMID: 19228339 DOI: 10.1111/j.1365-313x.2009.03843.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Heterotrimeric G protein knock-out mutants have no phenotypic defect in chloroplast development, and the connection between the G protein signaling pathway and chloroplast development has only been inferred from pharmaceutical evidence. Thus, whether G protein signaling plays a role in chloroplast development remains an open question. Here, we present genetic evidence, using the leaf-variegated mutant thylakoid formation 1 (thf1), indicating that inactivation or activation of the endogenous G protein alpha-subunit (GPA1) affects chloroplast development, as does the ectopic expression of the constitutively active Galpha-subunit (cGPA1). Molecular biological and genetic analyses showed that FtsH complexes, which are composed of type-A (FtsH1/FtsH5) and type-B (FtsH2/FtsH8) subunits, are required for cGPA1-promoted chloroplast development in thf1. Furthermore, the ectopic expression of cGPA1 rescues the leaf variegation of ftsh2. Consistent with this finding, microarray analysis shows that ectopic expression of cGPA1 partially corrects mis-regulated gene expression in thf1. This overlooked function of G proteins provides new insight into our understanding of the integrative signaling network, which dynamically regulates chloroplast development and function in response to both intracellular and extracellular signals.
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Affiliation(s)
- Lingang Zhang
- National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
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30
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Zhang L, Hu G, Cheng Y, Huang J. Heterotrimeric G protein α and β subunits antagonistically modulate stomatal density in Arabidopsis thaliana. Dev Biol 2008; 324:68-75. [DOI: 10.1016/j.ydbio.2008.09.008] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 08/13/2008] [Accepted: 09/02/2008] [Indexed: 11/28/2022]
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