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Boix M, Garcia-Rodriguez A, Castillo L, Miró B, Hamilton F, Tolak S, Pérez A, Monte-Bello C, Caldana C, Henriques R. 40S Ribosomal protein S6 kinase integrates daylength perception and growth regulation in Arabidopsis thaliana. PLANT PHYSIOLOGY 2024; 195:3039-3052. [PMID: 38701056 PMCID: PMC11288760 DOI: 10.1093/plphys/kiae254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 03/29/2024] [Accepted: 04/09/2024] [Indexed: 05/05/2024]
Abstract
Plant growth occurs via the interconnection of cell growth and proliferation in each organ following specific developmental and environmental cues. Therefore, different photoperiods result in distinct growth patterns due to the integration of light and circadian perception with specific Carbon (C) partitioning strategies. In addition, the TARGET OF RAPAMYCIN (TOR) kinase pathway is an ancestral signaling pathway that integrates nutrient information with translational control and growth regulation. Recent findings in Arabidopsis (Arabidopsis thaliana) have shown a mutual connection between the TOR pathway and the circadian clock. However, the mechanistical network underlying this interaction is mostly unknown. Here, we show that the conserved TOR target, the 40S ribosomal protein S6 kinase (S6K) is under circadian and photoperiod regulation both at the transcriptional and post-translational level. Total S6K (S6K1 and S6K2) and TOR-dependent phosphorylated-S6K protein levels were higher during the light period and decreased at dusk especially under short day conditions. Using chemical and genetic approaches, we found that the diel pattern of S6K accumulation results from 26S proteasome-dependent degradation and is altered in mutants lacking the circadian F-box protein ZEITLUPE (ZTL), further strengthening our hypothesis that S6K could incorporate metabolic signals via TOR, which are also under circadian regulation. Moreover, under short days when C/energy levels are limiting, changes in S6K1 protein levels affected starch, sucrose and glucose accumulation and consequently impacted root and rosette growth responses. In summary, we propose that S6K1 constitutes a missing molecular link where day-length perception, nutrient availability and TOR pathway activity converge to coordinate growth responses with environmental conditions.
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Affiliation(s)
- Marc Boix
- Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Campus UAB, 08193 Barcelona, Spain
| | - Alba Garcia-Rodriguez
- Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Campus UAB, 08193 Barcelona, Spain
| | - Laia Castillo
- Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Campus UAB, 08193 Barcelona, Spain
| | - Bernat Miró
- Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Campus UAB, 08193 Barcelona, Spain
| | - Ferga Hamilton
- School of Biological, Earth and Environmental Sciences, University College Cork, North Mall, Cork T23 N73K, Ireland
- Environmental Research Institute, University College Cork, Cork T23 XE10, Ireland
| | - Sanata Tolak
- School of Biological, Earth and Environmental Sciences, University College Cork, North Mall, Cork T23 N73K, Ireland
- Environmental Research Institute, University College Cork, Cork T23 XE10, Ireland
| | - Adrián Pérez
- Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Campus UAB, 08193 Barcelona, Spain
| | | | - Camila Caldana
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm 14476, Germany
| | - Rossana Henriques
- Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Campus UAB, 08193 Barcelona, Spain
- School of Biological, Earth and Environmental Sciences, University College Cork, North Mall, Cork T23 N73K, Ireland
- Environmental Research Institute, University College Cork, Cork T23 XE10, Ireland
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2
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Canal MV, Mansilla N, Gras DE, Ibarra A, Figueroa CM, Gonzalez DH, Welchen E. Cytochrome c levels affect the TOR pathway to regulate growth and metabolism under energy-deficient conditions. THE NEW PHYTOLOGIST 2024; 241:2039-2058. [PMID: 38191763 DOI: 10.1111/nph.19506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 12/03/2023] [Indexed: 01/10/2024]
Abstract
Mitochondrial function is essential for plant growth, but the mechanisms involved in adjusting growth and metabolism to changes in mitochondrial energy production are not fully understood. We studied plants with reduced expression of CYTC-1, one of two genes encoding the respiratory chain component cytochrome c (CYTc) in Arabidopsis, to understand how mitochondria communicate their status to coordinate metabolism and growth. Plants with CYTc deficiency show decreased mitochondrial membrane potential and lower ATP content, even when carbon sources are present. They also exhibit higher free amino acid content, induced autophagy, and increased resistance to nutritional stress caused by prolonged darkness, similar to plants with triggered starvation signals. CYTc deficiency affects target of rapamycin (TOR)-pathway activation, reducing S6 kinase (S6K) and RPS6A phosphorylation, as well as total S6K protein levels due to increased protein degradation via proteasome and autophagy. TOR overexpression restores growth and other parameters affected in cytc-1 mutants, even if mitochondrial membrane potential and ATP levels remain low. We propose that CYTc-deficient plants coordinate their metabolism and energy availability by reducing TOR-pathway activation as a preventive signal to adjust growth in anticipation of energy exhaustion, thus providing a mechanism by which changes in mitochondrial activity are transduced to the rest of the cell.
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Affiliation(s)
- María Victoria Canal
- Instituto de Agrobiotecnología del Litoral (CONICET-UNL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000, Santa Fe, Argentina
| | - Natanael Mansilla
- Instituto de Agrobiotecnología del Litoral (CONICET-UNL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000, Santa Fe, Argentina
| | - Diana E Gras
- Instituto de Agrobiotecnología del Litoral (CONICET-UNL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000, Santa Fe, Argentina
| | - Agustín Ibarra
- Instituto de Agrobiotecnología del Litoral (CONICET-UNL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000, Santa Fe, Argentina
| | - Carlos M Figueroa
- Instituto de Agrobiotecnología del Litoral (CONICET-UNL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000, Santa Fe, Argentina
| | - Daniel H Gonzalez
- Instituto de Agrobiotecnología del Litoral (CONICET-UNL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000, Santa Fe, Argentina
| | - Elina Welchen
- Instituto de Agrobiotecnología del Litoral (CONICET-UNL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000, Santa Fe, Argentina
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3
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Chen Q, Qu M, Chen Q, Meng X, Fan H. Phosphoproteomics analysis of the effect of target of rapamycin kinase inhibition on Cucumis sativus in response to Podosphaera xanthii. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2023; 197:107641. [PMID: 36940522 DOI: 10.1016/j.plaphy.2023.107641] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2023] [Revised: 03/12/2023] [Accepted: 03/13/2023] [Indexed: 06/18/2023]
Abstract
Target of rapamycin (TOR) kinase is a conserved sensor of cell growth in yeasts, plants, and mammals. Despite the extensive research on the TOR complex in various biological processes, large-scale phosphoproteomics analysis of TOR phosphorylation events upon environmental stress are scarce. Powdery mildew caused by Podosphaera xanthii poses a major threat to the quality and yield of cucumber (Cucumis sativus L.). Previous studies concluded that TOR participated in abiotic and biotic stress responses. Hence, studying the underlying mechanism of TOR-P. xanthii infection is particularly important. In this study, we performed a quantitative phosphoproteomics studies of Cucumis against P. xanthii attack under AZD-8055 (TOR inhibitor) pretreatment. A total of 3384 phosphopeptides were identified from the 1699 phosphoproteins. The Motif-X analysis showed high sensitivity and specificity of serine sites under AZD-8055-treatment or P. xanthii stress, and TOR exhibited a unique preference for proline at +1 position and glycine at -1 position to enhance the phosphorylation response to P. xanthii. The functional analysis suggested that the unique responses were attributed to proteins related to plant hormone signaling, mitogen-activated protein kinase cascade signaling, phosphatidylinositol signaling system, and circadian rhythm; and calcium signaling- and defense response-related proteins. Our results provided rich resources for understanding the molecular mechanism of how the TOR kinase controlled plant growth and stress adaptation.
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Affiliation(s)
- Qiumin Chen
- College of Horticulture, Shenyang Agricultural University, Shenyang, 110866, China
| | - Mengqi Qu
- College of Bioscience and Biotechnology, Shenyang Agricultural University, Shenyang, 110866, China
| | - Qinglei Chen
- College of Bioscience and Biotechnology, Shenyang Agricultural University, Shenyang, 110866, China
| | - Xiangnan Meng
- College of Bioscience and Biotechnology, Shenyang Agricultural University, Shenyang, 110866, China; Key Laboratory of Protected Horticulture of Ministry of Education, Shenyang Agricultural University, Shenyang, 110866, China; Key Laboratory of Biology and Genetic Improvement of Fruit Vegetables of Shenyang, Shenyang Agricultural University, Shenyang, 110866, China.
| | - Haiyan Fan
- College of Bioscience and Biotechnology, Shenyang Agricultural University, Shenyang, 110866, China; Key Laboratory of Protected Horticulture of Ministry of Education, Shenyang Agricultural University, Shenyang, 110866, China; Key Laboratory of Biology and Genetic Improvement of Fruit Vegetables of Shenyang, Shenyang Agricultural University, Shenyang, 110866, China.
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4
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Urrea-Castellanos R, Caldana C, Henriques R. Growing at the right time: interconnecting the TOR pathway with photoperiod and circadian regulation. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:7006-7015. [PMID: 35738873 PMCID: PMC9664226 DOI: 10.1093/jxb/erac279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Accepted: 06/23/2022] [Indexed: 06/15/2023]
Abstract
Plants can adjust their growth to specific times of the day and season. Different photoperiods result in distinct growth patterns, which correlate with specific carbon-partitioning strategies in source (leaves) and sink (roots) organs. Therefore, external cues such as light, day length, and temperature need to be integrated with intracellular processes controlling overall carbon availability and anabolism. The target of rapamycin (TOR) pathway is a signalling hub where environmental signals, circadian information, and metabolic processes converge to regulate plant growth. TOR complex mutants display altered patterns of root growth and starch levels. Moreover, depletion of TOR or reduction in cellular energy levels affect the pace of the clock by extending the period length, suggesting that this pathway could participate in circadian metabolic entrainment. However, this seems to be a mutual interaction, since the TOR pathway components are also under circadian regulation. These results strengthen the role of this signalling pathway as a master sensor of metabolic status, integrating day length and circadian cues to control anabolic processes in the cell, thus promoting plant growth and development. Expanding this knowledge from Arabidopsis thaliana to crops will improve our understanding of the molecular links connecting environmental perception and growth regulation under field conditions.
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Affiliation(s)
| | - Camila Caldana
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg, Potsdam-Golm, Germany
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5
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Meng Y, Zhang N, Li J, Shen X, Sheen J, Xiong Y. TOR kinase, a GPS in the complex nutrient and hormonal signaling networks to guide plant growth and development. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:7041-7054. [PMID: 35781569 PMCID: PMC9664236 DOI: 10.1093/jxb/erac282] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 06/24/2022] [Indexed: 06/01/2023]
Abstract
To survive and sustain growth, sessile plants have developed sophisticated internal signalling networks that respond to various external and internal cues. Despite the central roles of nutrient and hormone signaling in plant growth and development, how hormone-driven processes coordinate with metabolic status remains largely enigmatic. Target of rapamycin (TOR) kinase is an evolutionarily conserved master regulator that integrates energy, nutrients, growth factors, hormones, and stress signals to promote growth in all eukaryotes. Inspired by recent comprehensive systems, chemical, genetic, and genomic studies on TOR in plants, this review discusses a potential role of TOR as a 'global positioning system' that directs plant growth and developmental programs both temporally and spatially by integrating dynamic information in the complex nutrient and hormonal signaling networks. We further evaluate and depict the possible functional and mechanistic models for how a single protein kinase, TOR, is able to recognize, integrate, and even distinguish a plethora of positive and negative input signals to execute appropriate and distinct downstream biological processes via multiple partners and effectors.
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Affiliation(s)
| | | | - Jiatian Li
- College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
- Haixia Institute of Science and Technology, Plant Synthetic Biology Center, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xuehong Shen
- College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
- Haixia Institute of Science and Technology, Plant Synthetic Biology Center, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Jen Sheen
- Department of Molecular Biology and Centre for Computational and Integrative Biology, Massachusetts General Hospital, and Department of Genetics, Harvard Medical School, Boston, MA, USA
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6
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Henriques R, Calderan-Rodrigues MJ, Luis Crespo J, Baena-González E, Caldana C. Growing of the TOR world. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:6987-6992. [PMID: 36377640 PMCID: PMC9664224 DOI: 10.1093/jxb/erac401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Indexed: 06/16/2023]
Affiliation(s)
| | | | - José Luis Crespo
- Instituto de Bioquimica Vegetal y Fotosintesis, Consejo Superior de Investigaciones Cientificas (CSIC)-Universidad de Sevilla, Sevilla, Spain
| | - Elena Baena-González
- Instituto Gulbenkian de Ciência, 2780-156 Oeiras, Portugal and GREEN-IT Bioresources for Sustainability, ITQB-NOVA, 2780-157 Oeiras, Portugal
| | - Camila Caldana
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476, Potsdam-Golm, Germany
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7
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Wang S, Steed G, Webb AAR. Circadian entrainment in Arabidopsis. PLANT PHYSIOLOGY 2022; 190:981-993. [PMID: 35512209 PMCID: PMC9516740 DOI: 10.1093/plphys/kiac204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 03/29/2022] [Indexed: 06/14/2023]
Abstract
Circadian clocks coordinate physiology and development as an adaption to the oscillating day/night cycle caused by the rotation of Earth on its axis and the changing length of day and night away from the equator caused by orbiting the sun. Circadian clocks confer advantages by entraining to rhythmic environmental cycles to ensure that internal events within the plant occur at the correct time with respect to the cyclic external environment. Advances in determining the structure of circadian oscillators and the pathways that allow them to respond to light, temperature, and metabolic signals have begun to provide a mechanistic insight to the process of entrainment in Arabidopsis (Arabidopsis thaliana). We describe the concepts of entrainment and how it occurs. It is likely that a thorough mechanistic understanding of the genetic and physiological basis of circadian entrainment will provide opportunities for crop improvement.
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Affiliation(s)
- Shouming Wang
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
- School of Life Science and Technology, Hubei Engineering University, Xiaogan 432000, China
| | - Gareth Steed
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
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8
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Nakamichi N, Yamaguchi J, Sato A, Fujimoto KJ, Ota E. Chemical biology to dissect molecular mechanisms underlying plant circadian clocks. THE NEW PHYTOLOGIST 2022; 235:1336-1343. [PMID: 35661165 DOI: 10.1111/nph.18298] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Accepted: 05/19/2022] [Indexed: 06/15/2023]
Abstract
Circadian clocks regulate the diel rhythmic physiological activities of plants, enabling them to anticipate and adapt to day-night and seasonal changes. Genetic and biochemical approaches have suggested that transcription-translation feedback loops (TTFL) are crucial for Arabidopsis clock function. Recently, the study of chemical chronobiology has emerged as a discipline within the circadian clock field, with important and complementary discoveries from both plant and animal research. In this review, we introduce recent advances in chemical biology using small molecules to perturb plant circadian clock function through TTFL components. Studies using small molecule clock modulators have been instrumental for revealing the role of post-translational modification in the clock, or the metabolite-dependent clock input pathway, as well as for controlling clock-dependent flowering time.
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Affiliation(s)
- Norihito Nakamichi
- Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, 464-8601, Japan
| | - Junichiro Yamaguchi
- Department of Applied Chemistry, Waseda University, 513 Wasedatsurumakicho, Shinjuku, Tokyo, 169-8555, Japan
| | - Ayato Sato
- Institute of Transformative Bio-Molecules (ITbM), Nagoya University, Chikusa, Nagoya, 464-8602, Japan
| | - Kazuhiro J Fujimoto
- Institute of Transformative Bio-Molecules (ITbM), Nagoya University, Chikusa, Nagoya, 464-8602, Japan
- Graduate School of Science, Nagoya University, Chikusa, Nagoya, 464-8601, Japan
| | - Eisuke Ota
- Department of Applied Chemistry, Waseda University, 513 Wasedatsurumakicho, Shinjuku, Tokyo, 169-8555, Japan
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Güldür T. Potential linkages between circadian rhythm and membrane lipids: timekeeper and bilayer. BIOL RHYTHM RES 2022. [DOI: 10.1080/09291016.2022.2096756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Tayfun Güldür
- Medical Biochemistry Department, Faculty of Medicine, Inönü University, Malatya, Turkey
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10
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Chen W, Hu Z, Yu M, Zhu S, Xing J, Song L, Pu W, Yu F. A molecular link between autophagy and circadian rhythm in plants. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2022; 64:1044-1058. [PMID: 35297190 DOI: 10.1111/jipb.13250] [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: 01/05/2022] [Accepted: 03/16/2022] [Indexed: 06/14/2023]
Abstract
Extremely high or low autophagy levels disrupt plant survival under nutrient starvation. Recently, autophagy has been reported to display rhythms in animals. However, the mechanism of circadian regulation of autophagy is still unclear. Here, we observed that autophagy has a robust rhythm and that various autophagy-related genes (ATGs) are rhythmically expressed in Arabidopsis. Chromatin immunoprecipitation (ChIP) and dual-luciferase (LUC) analyses showed that the core oscillator gene TIMING OF CAB EXPRESSION 1 (TOC1) directly binds to the promoters of ATG (ATG1a, ATG2, and ATG8d) and negatively regulates autophagy activities under nutritional stress. Furthermore, autophagy defects might affect endogenous rhythms by reducing the rhythm amplitude of TOC1 and shortening the rhythm period of CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1). Autophagy is essential for the circadian clock pattern in seedling development and plant sensitivity to nutritional deficiencies. Taken together, our studies reveal a plant strategy in which the TOC1-ATG axis involved in autophagy-rhythm crosstalk to fine-tune the intensity of autophagy.
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Affiliation(s)
- Weijun Chen
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, and Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, Hunan University, Changsha, 410082, China
| | - Zhaotun Hu
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, and Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, Hunan University, Changsha, 410082, China
- Key Laboratory of Research and Utilization of Ethnomedicinal Plant Resources of Hunan Province, School of Biological and Food Engineering, Huaihua College, Huaihua, 418008, China
| | - MengTing Yu
- Key Laboratory of Research and Utilization of Ethnomedicinal Plant Resources of Hunan Province, School of Biological and Food Engineering, Huaihua College, Huaihua, 418008, China
| | - Sirui Zhu
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, and Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, Hunan University, Changsha, 410082, China
| | - Junjie Xing
- State Key Laboratory of Hybrid Rice, Hunan Hybrid Rice Research Center, Changsha, 410125, China
| | - Limei Song
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, and Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, Hunan University, Changsha, 410082, China
| | - Wenxuan Pu
- Technology Center, China Tobacco Hunan Industrial Co., Ltd., Changsha, 410007, China
| | - Feng Yu
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, and Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, Hunan University, Changsha, 410082, China
- State Key Laboratory of Hybrid Rice, Hunan Hybrid Rice Research Center, Changsha, 410125, China
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11
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Wingler A, Henriques R. Sugars and the speed of life-Metabolic signals that determine plant growth, development and death. PHYSIOLOGIA PLANTARUM 2022; 174:e13656. [PMID: 35243645 PMCID: PMC9314607 DOI: 10.1111/ppl.13656] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 02/24/2022] [Accepted: 03/01/2022] [Indexed: 05/27/2023]
Abstract
Plant growth and development depend on the availability of carbohydrates synthesised in photosynthesis (source activity) and utilisation of these carbohydrates for growth (sink activity). External conditions, such as temperature, nutrient availability and stress, can affect source as well as sink activity. Optimal utilisation of resources is under circadian clock control. This molecular timekeeper ensures that growth responses are adjusted to different photoperiod and temperature settings by modulating starch accumulation and degradation accordingly. For example, during the night, starch degradation is required to provide sugars for growth. Under favourable growth conditions, high sugar availability stimulates growth and development, resulting in an overall accelerated life cycle of annual plants. Key signalling components include trehalose-6-phosphate (Tre6P), which reflects sucrose availability and stimulates growth and branching when the conditions are favourable. Under sink limitation, Tre6P does, however, inhibit night-time starch degradation. Tre6P interacts with Sucrose-non-fermenting1-Related Kinase1 (SnRK1), a protein kinase that inhibits growth under starvation and stress conditions and delays development (including flowering and senescence). Tre6P inhibits SnRK1 activity, but SnRK1 increases the Tre6P to sucrose ratio under favourable conditions. Alongside Tre6P, Target of Rapamycin (TOR) stimulates processes such as protein synthesis and growth when sugar availability is high. In annual plants, an accelerated life cycle results in early leaf and plant senescence, thus shortening the lifespan. While the availability of carbohydrates in the form of sucrose and other sugars also plays an important role in seasonal life cycle events (phenology) of perennial plants, the sugar signalling pathways in perennials are less well understood.
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Affiliation(s)
- Astrid Wingler
- School of Biological, Earth & Environmental Sciences and Environmental Research InstituteUniversity College Cork, Distillery FieldsCork
| | - Rossana Henriques
- School of Biological, Earth & Environmental Sciences and Environmental Research InstituteUniversity College Cork, Distillery FieldsCork
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12
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Eskandari R, Ratnayake L, Lakin-Thomas PL. Shared Components of the FRQ-Less Oscillator and TOR Pathway Maintain Rhythmicity in Neurospora. J Biol Rhythms 2021; 36:329-345. [PMID: 33825541 PMCID: PMC8276340 DOI: 10.1177/0748730421999948] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Molecular models for the endogenous oscillators that drive circadian rhythms in eukaryotes center on rhythmic transcription/translation of a small number of "clock genes." Although substantial evidence supports the concept that negative and positive transcription/translation feedback loops (TTFLs) are responsible for regulating the expression of these clock genes, certain rhythms in the filamentous fungus Neurospora crassa continue even when clock genes (frq, wc-1, and wc-2) are not rhythmically expressed. Identification of the rhythmic processes operating outside of the TTFL has been a major unresolved area in circadian biology. Our lab previously identified a mutation (vta) that abolishes FRQ-less rhythmicity of the conidiation rhythm and also affects rhythmicity when FRQ is functional. Further studies identified the vta gene product as a component of the TOR (Target of Rapamycin) nutrient-sensing pathway that is conserved in eukaryotes. We now report the discovery of TOR pathway components including GTR2 (homologous to the yeast protein Gtr2, and RAG C/D in mammals) as binding partners of VTA through co-immunoprecipitation (IP) and mass spectrometry analysis using a VTA-FLAG strain. Reciprocal IP with GTR2-FLAG found VTA as a binding partner. A Δgtr2 strain was deficient in growth responses to amino acids. Free-running conidiation rhythms in a FRQ-less strain were abolished in Δgtr2. Entrainment of a FRQ-less strain to cycles of heat pulses demonstrated that Δgtr2 is defective in entrainment. In all of these assays, Δgtr2 is similar to Δvta. In addition, expression of GTR2 protein was found to be rhythmic across two circadian cycles, and functional VTA was required for GTR2 rhythmicity. FRQ protein exhibited the expected rhythm in the presence of GTR2 but the rhythmic level of FRQ dampened in the absence of GTR2. These results establish association of VTA with GTR2, and their role in maintaining functional circadian rhythms through the TOR pathway.
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Affiliation(s)
- Rosa Eskandari
- Department of Biology, York University, Toronto, ON, Canada
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13
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A Tour of TOR Complex Signaling in Plants. Trends Biochem Sci 2020; 46:417-428. [PMID: 33309324 DOI: 10.1016/j.tibs.2020.11.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 10/26/2020] [Accepted: 11/09/2020] [Indexed: 01/07/2023]
Abstract
To identify the appropriate times for growth and development, organisms must sense and process information about the availability of nutrients, energy status, and environmental cues. For sessile eukaryotes such as plants, integrating such information can be critical in life or death decisions. For nearly 30 years, the conserved phosphatidylinositol 3-kinase-related protein kinases (PIKKs) target of rapamycin (TOR) has been established as a central hub for integrating external and internal metabolic cues. Despite the functional conservation across eukaryotes, the TOR complex has evolved specific functional and mechanistic features in plants. Here, we present recent findings on the plant TOR complex that highlight the conserved and unique nature of this critical growth regulator and its role in multiple aspects of plant life.
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