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Xu Q, Zhang H, Vandenkoornhuyse P, Guo S, Kuzyakov Y, Shen Q, Ling N. Carbon starvation raises capacities in bacterial antibiotic resistance and viral auxiliary carbon metabolism in soils. Proc Natl Acad Sci U S A 2024; 121:e2318160121. [PMID: 38598339 PMCID: PMC11032446 DOI: 10.1073/pnas.2318160121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 03/12/2024] [Indexed: 04/12/2024] Open
Abstract
Organic carbon availability in soil is crucial for shaping microbial communities, yet, uncertainties persist concerning microbial adaptations to carbon levels and the ensuing ecological and evolutionary consequences. We investigated organic carbon metabolism, antibiotic resistance, and virus-host interactions in soils subjected to 40 y of chemical and organic fertilization that led to contrasting carbon availability: carbon-poor and carbon-rich soils, respectively. Carbon-poor soils drove the enrichment of putative genes involved in organic matter decomposition and exhibited specialization in utilizing complex organic compounds, reflecting scramble competition. This specialization confers a competitive advantage of microbial communities in carbon-poor soils but reduces their buffering capacity in terms of organic carbon metabolisms, making them more vulnerable to environmental fluctuations. Additionally, in carbon-poor soils, viral auxiliary metabolic genes linked to organic carbon metabolism increased host competitiveness and environmental adaptability through a strategy akin to "piggyback the winner." Furthermore, putative antibiotic resistance genes, particularly in low-abundance drug categories, were enriched in carbon-poor soils as an evolutionary consequence of chemical warfare (i.e., interference competition). This raises concerns about the potential dissemination of antibiotic resistance from conventional agriculture that relies on chemical-only fertilization. Consequently, carbon starvation resulting from long-term chemical-only fertilization increases microbial adaptations to competition, underscoring the importance of implementing sustainable agricultural practices to mitigate the emergence and spread of antimicrobial resistance and to increase soil carbon storage.
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Affiliation(s)
- Qicheng Xu
- Jiangsu Provincial Key Lab for Solid Organic Waste Utilization, Nanjing Agricultural University, Nanjing210095, China
- CNRS, UMR 6553 EcoBio, Université de Rennes, Rennes Cedex35042, France
| | - He Zhang
- Jiangsu Provincial Key Lab for Solid Organic Waste Utilization, Nanjing Agricultural University, Nanjing210095, China
- State Key Laboratory of Herbage Improvement and Grassland Agro-Ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou730020, China
| | | | - Shiwei Guo
- Jiangsu Provincial Key Lab for Solid Organic Waste Utilization, Nanjing Agricultural University, Nanjing210095, China
| | - Yakov Kuzyakov
- Department of Soil Science of Temperate Ecosystems, University of Göttingen, Göttingen37077, Germany
- Department of Agricultural Soil Science, University of Göttingen, Göttingen37077, Germany
| | - Qirong Shen
- Jiangsu Provincial Key Lab for Solid Organic Waste Utilization, Nanjing Agricultural University, Nanjing210095, China
| | - Ning Ling
- State Key Laboratory of Herbage Improvement and Grassland Agro-Ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou730020, China
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2
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Artins A, Fernie AR. FCS-like zinc finger proteins maintain energy homeostasis during stresses. Trends Plant Sci 2023; 28:1347-1349. [PMID: 37743166 DOI: 10.1016/j.tplants.2023.09.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 08/28/2023] [Accepted: 09/08/2023] [Indexed: 09/26/2023]
Abstract
Sucrose non-fermenting kinase 1 (SnRK1) has emerged as a pivotal activator of the autophagy pathway; however, the reciprocal influence of autophagy on SnRK1 remains unknown. Yang et al. have recently revealed the existence of a feedback loop connecting autophagy and SnRK1 in terrestrial plants, involving the novel FCS-like zinc finger (FLZ) class of proteins.
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Affiliation(s)
- Anthony Artins
- Max-Planck Institut für Molekulare Pflanzenphysiologie, 14476, Potsdam-Golm, Germany.
| | - Alisdair R Fernie
- Max-Planck Institut für Molekulare Pflanzenphysiologie, 14476, Potsdam-Golm, Germany.
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3
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Zhang YL, Yang Y, Saurer M, Schaub M, Gessler A, Lehmann MM, Rigling A, Walser M, Stierli B, Hajjar N, Christen D, Li MH. Sugar infusion into trees: A novel method to study tree carbon relations and its regulations. Front Plant Sci 2023; 14:1142595. [PMID: 36909442 PMCID: PMC9996627 DOI: 10.3389/fpls.2023.1142595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 02/14/2023] [Indexed: 06/18/2023]
Abstract
Many carbon-related physiological questions in plants such as carbon (C) limitation or starvation have not yet been resolved thoroughly due to the lack of suitable experimental methodology. As a first step towards resolving these problems, we conducted infusion experiments with bonsai trees (Ficus microcarpa) and young maple trees (Acer pseudoplatanus) in greenhouse, and with adult Scots pine trees (Pinus sylvestris) in the field, that were "fed" with 13C-labelled glucose either through the phloem or the xylem. We then traced the 13C-signal in plant organic matter and respiration to test whether trees can take up and metabolize exogenous sugars infused. Ten weeks after infusion started, xylem but not phloem infusion significantly increased the δ13C values in both aboveground and belowground tissues of the bonsai trees in the greenhouse, whereas xylem infusion significantly increased xylem δ13C values and phloem infusion significantly increased phloem δ13C values of the adult pines in the field experiment, compared to the corresponding controls. The respiration measurement experiment with young maple trees showed significantly increased δ13C-values in shoot respired CO2 at the time of four weeks after xylem infusion started. Our results clearly indicate that trees do translocate and metabolize exogenous sugars infused, and because the phloem layer is too thin, and thus xylem infusion can be better operated than phloem infusion. This tree infusion method developed here opens up new avenues and has great potential to be used for research on the whole plant C balance and its regulation in response to environmental factors and extreme stress conditions.
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Affiliation(s)
- Yan-Li Zhang
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
- Department of Environmental Systems Science, Institute of Terrestrial Ecosystems, ETH Zürich, Zürich, Switzerland
| | - Yue Yang
- College of Ecology and Environment, Hainan University, Haikou, China
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
| | - Matthias Saurer
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
| | - Marcus Schaub
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
| | - Arthur Gessler
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
- Department of Environmental Systems Science, Institute of Terrestrial Ecosystems, ETH Zürich, Zürich, Switzerland
| | - Marco M. Lehmann
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
| | - Andreas Rigling
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
- Department of Environmental Systems Science, Institute of Terrestrial Ecosystems, ETH Zürich, Zürich, Switzerland
| | - Marco Walser
- Forest Soils and Biogeochemistry, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
| | - Beat Stierli
- Forest Soils and Biogeochemistry, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
| | - Noureddine Hajjar
- Forest Soils and Biogeochemistry, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
| | - Daniel Christen
- Forest Soils and Biogeochemistry, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
| | - Mai-He Li
- College of Ecology and Environment, Hainan University, Haikou, China
- Key Laboratory of Geographical Processes and Ecological Security in Changbai Mountains, Ministry of Education, School of Geographical Sciences, Northeast Normal University, Changchun, Jilin, China
- College of Life Science, Hebei University, Baoding, Hebei, China
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4
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Oswald SW, Aubrey DP. Modeling starch dynamics from seasonal variations of photosynthesis, growth, and respiration. Tree Physiol 2023:tpad007. [PMID: 36708035 DOI: 10.1093/treephys/tpad007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 11/21/2022] [Indexed: 06/18/2023]
Abstract
Nonstructural carbohydrates (NSCs) buffer differences in plant carbon supply (photosynthesis) and demand (respiration, growth, etc.) but the regulation of their dynamics remains unresolved. Seasonal variations in NSCs are well-documented, but differences in the time-average, amplitude, phase, and other characteristics across ecosystems and functional types lack explanation; furthermore, observed dynamics do not always match expectations. The failure to match observed and expected dynamics has stimulated debate on whether carbon supply or demand drives NSC dynamics. To gain insight into how carbon supply and demand drive seasonal NSC dynamics, we derive a simple model of NSC dynamics based on carbon mass balance and linearizing the NSC demand to determine how supply-driven and demand-driven seasonal NSC dynamics differ. We find that supply-driven and demand-driven dynamics yield distinct timings of seasonal extrema, and supply overrides demand when carbon supply is low in winter (e.g., at high latitudes). Our results also suggest that NSC dynamics often lag changes carbon mass balance. We also predict differences in NSC dynamics across mass, suggesting saplings are more dynamics and respond faster to the environment than mature trees. Our findings suggest substrate-dependent regulation with environmental variation is sufficient to generate complex NSC dynamics.
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Affiliation(s)
- Scott W Oswald
- Savannah River Ecology Lab, Savannah River Site, Jackson, SC, USA
- Warnell School of Forestry, University of Georgia, Athens, GA, USA
| | - Doug P Aubrey
- Savannah River Ecology Lab, Savannah River Site, Jackson, SC, USA
- Warnell School of Forestry, University of Georgia, Athens, GA, USA
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Zhang XQ, Zeng QX, Yuan XC, Wan XH, Cui JY, Li WZ, Lin HY, Xie H, Chen WW, Wu JM, Chen YM. Phosphorus limitation induced by nitrogen addition changed soil microbial community structure in a subtropical Pinus taiwanensis forest. Ying Yong Sheng Tai Xue Bao 2023; 34:203-212. [PMID: 36799395 DOI: 10.13287/j.1001-9332.202301.042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
Soil microorganisms play an important role in the biogeochemical cycles of terrestrial ecosystems. How-ever, it is still unclear how the amount and duration of nitrogen (N) addition affect soil microbial community structure and whether there is a correlation between the changes in microbial community structure and their nutrient limi-tation status. In this study, we conducted an N addition experiment in a subtropical Pinus taiwanensis forest to simulate N deposition with three treatments: control (CK, 0 kg N·hm-2·a-1), low N (LN, 40 kg N·hm-2·a-1), and high N (HN, 80 kg N·hm-2·a-1). Basic soil physicochemical properties, phospholipid fatty acids content, and carbon (C), N and phosphorus (P) acquisition enzyme activities were measured after one and three years of N addition. The relative nutrient limitation status of soil microorganisms was analyzed using ecological enzyme stoichiometry. The results showed that one-year N addition did not affect soil microbial community structure. Three-year LN treatment significantly increased the contents of Gram-positive bacteria (G+), Gram-negative bacteria (G-), actinomycetes (ACT), and total phospholipid fatty acids (TPLFA), whereas three-year HN treatment did not significantly affect soil microbial community, indicating that bacteria and ACT might be more sensitive to N addition. Nitrogen addition exacerbated soil C and P limitation. Phosphorus limitation was the optimal explanatory factor for the changes in soil microbial community structure. It suggested that P limitation induced by N addition might be more beneficial for the growth of certain oligotrophic bacteria (e.g. G+) and the microorganisms participating in the P cycling (e.g. ACT), with consequences on soil microbial community structure of subtropical Pinus taiwanensis forest.
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Affiliation(s)
- Xiao-Qing Zhang
- Cultivation Base of State Key Laboratory of Humid Subtropical Mountain Ecology, Fujian Normal University, Fuzhou 350007, China.,School of Geographical Science, Fujian Normal University, Fuzhou 350007, China
| | - Quan-Xin Zeng
- Cultivation Base of State Key Laboratory of Humid Subtropical Mountain Ecology, Fujian Normal University, Fuzhou 350007, China.,School of Geographical Science, Fujian Normal University, Fuzhou 350007, China
| | - Xiao-Cun Yuan
- Cultivation Base of State Key Laboratory of Humid Subtropical Mountain Ecology, Fujian Normal University, Fuzhou 350007, China.,School of Geographical Science, Fujian Normal University, Fuzhou 350007, China.,College of Tourism, Wuyi University, Wuyishan 354300, Fujian, China
| | - Xiao-Hua Wan
- Cultivation Base of State Key Laboratory of Humid Subtropical Mountain Ecology, Fujian Normal University, Fuzhou 350007, China.,School of Geographical Science, Fujian Normal University, Fuzhou 350007, China
| | - Ju-Yan Cui
- Cultivation Base of State Key Laboratory of Humid Subtropical Mountain Ecology, Fujian Normal University, Fuzhou 350007, China.,School of Geographical Science, Fujian Normal University, Fuzhou 350007, China
| | - Wen-Zhou Li
- Daiyun Mountain National Nature Reserve Administration Bureau, Quanzhou 362500, Fujian, China
| | - Hui-Ying Lin
- Cultivation Base of State Key Laboratory of Humid Subtropical Mountain Ecology, Fujian Normal University, Fuzhou 350007, China.,School of Geographical Science, Fujian Normal University, Fuzhou 350007, China
| | - Huan Xie
- Cultivation Base of State Key Laboratory of Humid Subtropical Mountain Ecology, Fujian Normal University, Fuzhou 350007, China.,School of Geographical Science, Fujian Normal University, Fuzhou 350007, China
| | - Wen-Wei Chen
- Daiyun Mountain National Nature Reserve Administration Bureau, Quanzhou 362500, Fujian, China
| | - Jun-Mei Wu
- Cultivation Base of State Key Laboratory of Humid Subtropical Mountain Ecology, Fujian Normal University, Fuzhou 350007, China.,School of Geographical Science, Fujian Normal University, Fuzhou 350007, China
| | - Yueh-Min Chen
- Cultivation Base of State Key Laboratory of Humid Subtropical Mountain Ecology, Fujian Normal University, Fuzhou 350007, China.,School of Geographical Science, Fujian Normal University, Fuzhou 350007, China
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Calderan-Rodrigues MJ, Luzarowski M, Monte-Bello CC, Minen RI, Zühlke BM, Nikoloski Z, Skirycz A, Caldana C. Proteogenic Dipeptides Are Characterized by Diel Fluctuations and Target of Rapamycin Complex-Signaling Dependency in the Model Plant Arabidopsis thaliana. Front Plant Sci 2021; 12:758933. [PMID: 35003157 PMCID: PMC8727597 DOI: 10.3389/fpls.2021.758933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Accepted: 11/11/2021] [Indexed: 06/14/2023]
Abstract
As autotrophic organisms, plants capture light energy to convert carbon dioxide into ATP, nicotinamide adenine dinucleotide phosphate (NADPH), and sugars, which are essential for the biosynthesis of building blocks, storage, and growth. At night, metabolism and growth can be sustained by mobilizing carbon (C) reserves. In response to changing environmental conditions, such as light-dark cycles, the small-molecule regulation of enzymatic activities is critical for reprogramming cellular metabolism. We have recently demonstrated that proteogenic dipeptides, protein degradation products, act as metabolic switches at the interface of proteostasis and central metabolism in both plants and yeast. Dipeptides accumulate in response to the environmental changes and act via direct binding and regulation of critical enzymatic activities, enabling C flux distribution. Here, we provide evidence pointing to the involvement of dipeptides in the metabolic rewiring characteristics for the day-night cycle in plants. Specifically, we measured the abundance of 13 amino acids and 179 dipeptides over short- (SD) and long-day (LD) diel cycles, each with different light intensities. Of the measured dipeptides, 38 and eight were characterized by day-night oscillation in SD and LD, respectively, reaching maximum accumulation at the end of the day and then gradually falling in the night. Not only the number of dipeptides, but also the amplitude of the oscillation was higher in SD compared with LD conditions. Notably, rhythmic dipeptides were enriched in the glucogenic amino acids that can be converted into glucose. Considering the known role of Target of Rapamycin (TOR) signaling in regulating both autophagy and metabolism, we subsequently investigated whether diurnal fluctuations of dipeptides levels are dependent on the TOR Complex (TORC). The Raptor1b mutant (raptor1b), known for the substantial reduction of TOR kinase activity, was characterized by the augmented accumulation of dipeptides, which is especially pronounced under LD conditions. We were particularly intrigued by the group of 16 dipeptides, which, based on their oscillation under SD conditions and accumulation in raptor1b, can be associated with limited C availability or photoperiod. By mining existing protein-metabolite interaction data, we delineated putative protein interactors for a representative dipeptide Pro-Gln. The obtained list included enzymes of C and amino acid metabolism, which are also linked to the TORC-mediated metabolic network. Based on the obtained results, we speculate that the diurnal accumulation of dipeptides contributes to its metabolic adaptation in response to changes in C availability. We hypothesize that dipeptides would act as alternative respiratory substrates and by directly modulating the activity of the focal enzymes.
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Affiliation(s)
| | - Marcin Luzarowski
- Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany
| | | | | | - Boris M. Zühlke
- Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Zoran Nikoloski
- Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Aleksandra Skirycz
- Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany
- Boyce Thompson Institute, Ithaca, NY, United States
| | - Camila Caldana
- Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany
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Högberg MN, Högberg P, Wallander H, Nilsson LO. Carbon-nitrogen relations of ectomycorrhizal mycelium across a natural nitrogen supply gradient in boreal forest. New Phytol 2021; 232:1839-1848. [PMID: 34449884 DOI: 10.1111/nph.17701] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 08/17/2021] [Indexed: 06/13/2023]
Abstract
The supply of carbon (C) from tree photosynthesis to ectomycorrhizal (ECM) fungi is known to decrease with increasing plant nitrogen (N) supply, but how this affects fungal nutrition and growth remains to be clarified. We placed mesh-bags with quartz sand, with or without an organic N (15 N-, 13 C-labeled) source, in the soil along a natural N supply gradient in boreal forest, to measure growth and use of N and C by ECM extramatrical mycelia. Mycelial C : N declined with increasing N supply. Addition of N increased mycelial growth at the low-N end of the gradient. We found an inverse relationship between uptake of added N and C; the use of added N was high when ambient N was low, whereas use of added C was high when C from photosynthesis was low. We propose that growth of ECM fungi is N-limited when soil N is scarce and tree belowground C allocation to ECM fungi is high, but is C-limited when N supply is high and tree belowground C allocation is low. This suggests that ECM fungi have a major role in soil N retention in nutrient-poor, but less so in nutrient-rich boreal forests.
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Affiliation(s)
- Mona N Högberg
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, SE-901 83, Sweden
| | - Peter Högberg
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, SE-901 83, Sweden
| | - Håkan Wallander
- Department of Biology, Lund University, Lund, SE-22362, Sweden
| | - Lars-Ola Nilsson
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Frederiksberg C, DK-1958, Denmark
- Chancellery, Halmstad University, Halmstad, SE-301 18, Sweden
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Rabouille S, Campbell DA, Masuda T, Zavřel T, Bernát G, Polerecky L, Halsey K, Eichner M, Kotabová E, Stephan S, Lukeš M, Claquin P, Bonomi-Barufi J, Lombardi AT, Červený J, Suggett DJ, Giordano M, Kromkamp JC, Prášil O. Electron & Biomass Dynamics of Cyanothece Under Interacting Nitrogen & Carbon Limitations. Front Microbiol 2021; 12:617802. [PMID: 33897635 PMCID: PMC8063122 DOI: 10.3389/fmicb.2021.617802] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 03/01/2021] [Indexed: 11/25/2022] Open
Abstract
Marine diazotrophs are a diverse group with key roles in biogeochemical fluxes linked to primary productivity. The unicellular, diazotrophic cyanobacterium Cyanothece is widely found in coastal, subtropical oceans. We analyze the consequences of diazotrophy on growth efficiency, compared to NO3–-supported growth in Cyanothece, to understand how cells cope with N2-fixation when they also have to face carbon limitation, which may transiently affect populations in coastal environments or during blooms of phytoplankton communities. When grown in obligate diazotrophy, cells face the double burden of a more ATP-demanding N-acquisition mode and additional metabolic losses imposed by the transient storage of reducing potential as carbohydrate, compared to a hypothetical N2 assimilation directly driven by photosynthetic electron transport. Further, this energetic burden imposed by N2-fixation could not be alleviated, despite the high irradiance level within the cultures, because photosynthesis was limited by the availability of dissolved inorganic carbon (DIC), and possibly by a constrained capacity for carbon storage. DIC limitation exacerbates the costs on growth imposed by nitrogen fixation. Therefore, the competitive efficiency of diazotrophs could be hindered in areas with insufficient renewal of dissolved gases and/or with intense phytoplankton biomass that both decrease available light energy and draw the DIC level down.
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Affiliation(s)
- Sophie Rabouille
- Sorbonne Université, CNRS, LOV, Villefranche-sur-Mer, France.,Sorbonne Université, CNRS, LOMIC, Banyuls-sur-Mer, France
| | - Douglas A Campbell
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia.,Mount Allison University, Sackville, NB, Canada
| | - Takako Masuda
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia
| | - Tomáš Zavřel
- Department of Adaptive Biotechnologies, Global Change Research Institute CAS, Brno, Czechia
| | - Gábor Bernát
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia.,Centre for Ecological Research, Balaton Limnological Institute, Klebelsberg Kuno u. 3. 8237 Tihany, Hungary
| | - Lubos Polerecky
- Department of Earth Sciences, Utrecht University, Utrecht, Netherlands
| | - Kimberly Halsey
- Department of Microbiology, Oregon State University, Corvallis, OR, United States
| | - Meri Eichner
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia.,Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Eva Kotabová
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia
| | - Susanne Stephan
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Zur alten Fischerhütte 2, Stechlin, Germany.,Department of Ecology, Berlin Institute of Technology (TU Berlin), Ernst-Reuter-Platz 1, Berlin, Germany
| | - Martin Lukeš
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia
| | - Pascal Claquin
- UMR BOREA (CNRS 8067), MNHN, IRD (207), Université de Caen Basse-Normandie, Caen, France
| | - José Bonomi-Barufi
- Departamento de Botânica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | | | - Jan Červený
- Department of Adaptive Biotechnologies, Global Change Research Institute CAS, Brno, Czechia
| | - David J Suggett
- University of Technology Sydney, Climate Change Cluster, Faculty of Science, Ultimo, NSW, Australia
| | - Mario Giordano
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia.,Dipartimento di Scienze della Vita e dell'Ambiente, UniversitaÌ Politecnica delle Marche, Ancona, Italy
| | - Jacco C Kromkamp
- NIOZ Royal Netherlands Institute for Sea Research and Utrecht University, Utrecht, Netherlands
| | - Ondřej Prášil
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia
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Holwerda EK, Zhou J, Hon S, Stevenson DM, Amador-Noguez D, Lynd LR, van Dijken JP. Metabolic Fluxes of Nitrogen and Pyrophosphate in Chemostat Cultures of Clostridium thermocellum and Thermoanaerobacterium saccharolyticum. Appl Environ Microbiol 2020; 86:e01795-20. [PMID: 32978139 DOI: 10.1128/AEM.01795-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 09/17/2020] [Indexed: 01/29/2023] Open
Abstract
Clostridium thermocellum and Thermoanaerobacterium saccharolyticum were grown in cellobiose-limited chemostat cultures at a fixed dilution rate. C. thermocellum produced acetate, ethanol, formate, and lactate. Surprisingly, and in contrast to batch cultures, in cellobiose-limited chemostat cultures of T. saccharolyticum, ethanol was the main fermentation product. Enzyme assays confirmed that in C. thermocellum, glycolysis proceeds via pyrophosphate (PPi)-dependent phosphofructokinase (PFK), pyruvate-phosphate dikinase (PPDK), as well as a malate shunt for the conversion of phosphoenolpyruvate (PEP) to pyruvate. Pyruvate kinase activity was not detectable. In T. saccharolyticum, ATP but not PPi served as cofactor for the PFK reaction. High activities of both pyruvate kinase and PPDK were present, whereas the activities of a malate shunt enzymes were low in T. saccharolyticum In C. thermocellum, glycolysis via PPi-PFK and PPDK obeys the equation glucose + 5 NDP + 3 PPi → 2 pyruvate + 5 NTP + Pi (where NDP is nucleoside diphosphate and NTP is nucleoside triphosphate). Metabolic flux analysis of chemostat data with the wild type and a deletion mutant of the proton-pumping pyrophosphatase showed that a PPi-generating mechanism must be present that operates according to ATP + Pi → ADP + PPi Both organisms also produced significant amounts of amino acids in cellobiose-limited cultures. It was anticipated that this phenomenon would be suppressed by growth under nitrogen limitation. Surprisingly, nitrogen-limited chemostat cultivation of wild-type C. thermocellum revealed a bottleneck in pyruvate oxidation, as large amounts of pyruvate and amino acids, mainly valine, were excreted; up to 50% of the nitrogen consumed was excreted again as amino acids.IMPORTANCE This study discusses the fate of pyrophosphate in the metabolism of two thermophilic anaerobes that lack a soluble irreversible pyrophosphatase as present in Escherichia coli but instead use a reversible membrane-bound proton-pumping enzyme. In such organisms, the charging of tRNA with amino acids may become more reversible. This may contribute to the observed excretion of amino acids during sugar fermentation by Clostridium thermocellum and Thermoanaerobacterium saccharolyticum Calculation of the energetic advantage of reversible pyrophosphate-dependent glycolysis, as occurs in Clostridium thermocellum, could not be properly evaluated, as currently available genome-scale models neglect the anabolic generation of pyrophosphate in, for example, polymerization of amino acids to protein. This anabolic pyrophosphate replaces ATP and thus saves energy. Its amount is, however, too small to cover the pyrophosphate requirement of sugar catabolism in glycolysis. Consequently, pyrophosphate for catabolism is generated according to ATP + Pi → ADP + PPi.
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Urrutia-Jalabert R, Lara A, Barichivich J, Vergara N, Rodriguez CG, Piper FI. Low Growth Sensitivity and Fast Replenishment of Non-structural Carbohydrates in a Long-Lived Endangered Conifer After Drought. Front Plant Sci 2020; 11:905. [PMID: 32733500 PMCID: PMC7357304 DOI: 10.3389/fpls.2020.00905] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 06/02/2020] [Indexed: 06/11/2023]
Abstract
There is an ongoing debate on whether a drought induced carbohydrate limitation (source limitation) or a direct effect of water shortage (sink limitation) limit growth under drought. In this study, we investigated the effects of the two driest summers recorded in southern Chile in the last seven decades, on the growth and non-structural carbohydrates (NSC) concentrations of the slow-growing conifer Fitzroya cupressoides. Specifically, we studied the seasonal variation of NSC in saplings and adults one and two years after the occurrence of a 2 year-summer drought at two sites of contrasting precipitation and productivity (mesic-productive vs. rainy-less productive). We also evaluated radial growth before, during and after the drought, and predicted that drought could have reduced growth. If drought caused C source limitation, we expected that NSCs will be lower during the first than the second year after drought. Conversely, similar NSC concentrations between years or higher NSC concentrations in the first year would be supportive of sink limitation. Also, due to the lower biomass of saplings compared with adults, we expected that saplings should experience stronger seasonal NSC remobilization than adults. We confirmed this last expectation. Moreover, we found no significant growth reduction during drought in the rainy site and a slightly significant growth reduction at the mesic site for both saplings and adults. Across organs and in both sites and age classes, NSC, starch, and sugar concentrations were generally higher in the first than in the second year following drought, while NSC seasonal remobilization was generally lower. Higher NSC concentrations along with lower seasonal NSC remobilization during the first post-drought year are supportive of sink limitation. However, as these results were found at both sites while growth decreased slightly and just at the mesic site, limited growth only is unlikely to have caused NSC accumulation. Rather, these results suggest that the post-drought dynamics of carbohydrate storage are partly decoupled from the growth dynamics, and that the rebuild of C reserves after drought may be a priority in this species.
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Affiliation(s)
- Rocío Urrutia-Jalabert
- Instituto Forestal INFOR, Valdivia, Chile
- Laboratorio de Dendrocronología y Cambio Global, Facultad de Ciencias Forestales y Recursos Naturales, Instituto de Conservación, Biodiversidad y Territorio, Universidad Austral de Chile, Valdivia, Chile
- Centro de Ciencia del Clima y la Resiliencia, CR2, Santiago, Chile
| | - Antonio Lara
- Laboratorio de Dendrocronología y Cambio Global, Facultad de Ciencias Forestales y Recursos Naturales, Instituto de Conservación, Biodiversidad y Territorio, Universidad Austral de Chile, Valdivia, Chile
- Centro de Ciencia del Clima y la Resiliencia, CR2, Santiago, Chile
- Fundación Centro de los Bosques Nativos FORECOS, Valdivia, Chile
| | - Jonathan Barichivich
- Laboratorio de Dendrocronología y Cambio Global, Facultad de Ciencias Forestales y Recursos Naturales, Instituto de Conservación, Biodiversidad y Territorio, Universidad Austral de Chile, Valdivia, Chile
- Laboratoire des Sciences du Climat et de l’Environnement, IPSL, CRNS/CEA/UVSQ, Paris, France
| | - Nicolás Vergara
- Centro de Ciencia del Clima y la Resiliencia, CR2, Santiago, Chile
| | - Carmen Gloria Rodriguez
- Laboratorio de Dendrocronología y Cambio Global, Facultad de Ciencias Forestales y Recursos Naturales, Instituto de Conservación, Biodiversidad y Territorio, Universidad Austral de Chile, Valdivia, Chile
| | - Frida I. Piper
- Centro de Investigación en Ecosistemas de la Patagonia, Coyhaique, Chile
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11
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Huang J, Rücker A, Schmidt A, Gleixner G, Gershenzon J, Trumbore S, Hartmann H. Production of constitutive and induced secondary metabolites is coordinated with growth and storage in Norway spruce saplings. Tree Physiol 2020; 40:928-942. [PMID: 32268379 PMCID: PMC7325531 DOI: 10.1093/treephys/tpaa040] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 01/17/2020] [Accepted: 03/18/2020] [Indexed: 05/12/2023]
Abstract
A mechanistic understanding of how trees balance the trade-offs between growth, storage and defense is limited but crucial for predicting tree responses to abiotic and biotic stresses. Here we investigated how trees allocate storage of non-structural carbohydrates (NSC) to growth and constitutive and induced secondary metabolites (SM). We exposed Norway spruce (Picea abies) saplings to 5 weeks of complete darkness to induce light and/or carbon limitation and then applied methyl jasmonate (MeJA) to simulate biotic attack. We measured changes in biomass, NSC (sum of soluble sugars and starches), and constitutive and induced SM (sum of phenolic compounds and terpenoids) in current-year developing and previous-year mature needles and branches, as well as volatiles emitted from the canopy. Under darkness, NSC storage was preferentially used for constitutive biosynthesis of monoterpenes rather than biosynthesis of stilbenes and growth of developing organs, while SM stored in mature organs cannot be remobilized and recycled. Furthermore, MeJA-induced production of SM was constrained by low NSC availability in developing organs but not in mature organs grown in the dark. Emissions of volatiles were suppressed in the dark but after 1 h of re-illumination, emissions of both constitutive and induced monoterpene hydrocarbons recovered rapidly, whereas emissions of linalool and sesquiterpene produced via de novo synthesis did not recover. Our results highlight that light and/or carbon limitation may constrain constitutive and JA-induced biosynthesis of SM in coordination with growth, NSC storage and mobilization.
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Affiliation(s)
- Jianbei Huang
- Department of Biogeochemical Processes, Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, Jena 07745, Germany
- Corresponding author ()
| | - Alexander Rücker
- Department of Biogeochemical Processes, Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, Jena 07745, Germany
| | - Axel Schmidt
- Department of Biochemistry, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, Jena 07745, Germany
| | - Gerd Gleixner
- Department of Biogeochemical Processes, Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, Jena 07745, Germany
| | - Jonathan Gershenzon
- Department of Biochemistry, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, Jena 07745, Germany
| | - Susan Trumbore
- Department of Biogeochemical Processes, Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, Jena 07745, Germany
| | - Henrik Hartmann
- Department of Biogeochemical Processes, Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, Jena 07745, Germany
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12
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Marozava S, Merl-Pham J, Müller H, Meckenstock RU. Adaptation of Carbon Source Utilization Patterns of Geobacter metallireducens During Sessile Growth. Front Microbiol 2020; 11:1271. [PMID: 32655526 PMCID: PMC7324539 DOI: 10.3389/fmicb.2020.01271] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 05/19/2020] [Indexed: 11/13/2022] Open
Abstract
There are two main strategies known how microorganisms regulate substrate utilization: specialization on one preferred substrate at high concentrations in batch cultures or simultaneous utilization of many substrates at low concentrations in chemostats. However, it remains unclear how microorganisms utilize substrates at low concentrations in the subsurface: do they focus on a single substrate and exhibit catabolite repression or do they de-repress regulation of all catabolic pathways? Here, we investigated the readiness of Geobacter metallireducens to degrade organic substrates under sessile growth in sediment columns in the presence of a mixed community as a model for aquifers. Three parallel columns were filled with sand and flushed with anoxic medium at a constant inflow (18 ml h-1) of the substrate benzoate (1 mM) with non-limiting nitrate concentrations (30 mM) as electron acceptor. Columns were inoculated with the anaerobic benzoate degrader G. metallireducens. Microbial degradation produced concentration gradients of benzoate toward the column outlet. Metagenomics and label-free metaproteomics were used to detect and quantify the protein expression of G. metallireducens. Bulk benzoate concentrations below 0.2 mM led to increased abundance of catabolic proteins involved in utilization of fermentation products and aromatic compounds including the complete upregulation of the toluene-degrading pathway although toluene was not added to the medium. We propose that under sessile conditions and low substrate concentrations G. metallireducens expresses a specific set of catabolic pathways for preferred substrates, even when these substrates are not present.
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Affiliation(s)
- Sviatlana Marozava
- Institute of Groundwater Ecology, Helmholtz Zentrum München, Neuherberg, Germany
| | - Juliane Merl-Pham
- Research Unit Protein Science, Helmholtz Zentrum München, Neuherberg, Germany
| | - Hubert Müller
- Environmental Microbiology and Biotechnology, University of Duisburg-Essen, Essen, Germany
| | - Rainer U. Meckenstock
- Environmental Microbiology and Biotechnology, University of Duisburg-Essen, Essen, Germany
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13
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Roberty S, Béraud E, Grover R, Ferrier-Pagès C. Coral Productivity Is Co-Limited by Bicarbonate and Ammonium Availability. Microorganisms 2020; 8:microorganisms8050640. [PMID: 32354088 PMCID: PMC7285240 DOI: 10.3390/microorganisms8050640] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 04/23/2020] [Accepted: 04/24/2020] [Indexed: 11/16/2022] Open
Abstract
The nitrogen environment and nitrogen status of reef-building coral endosymbionts is one of the important factors determining the optimal assimilation of phototrophic carbon and hence the growth of the holobiont. However, the impact of inorganic nutrient availability on the photosynthesis and physiological state of the coral holobiont is partly understood. This study aimed to determine if photosynthesis of the endosymbionts associated with the coral Stylophora pistillata and the overall growth of the holobiont were limited by the availability of dissolved inorganic carbon and nitrogen in seawater. For this purpose, colonies were incubated in absence or presence of 4 µM ammonium and/or 6 mM bicarbonate. Photosynthetic performances, pigments content, endosymbionts density and growth rate of the coral colonies were monitored for 3 weeks. Positive effects were observed on coral physiology with the supplementation of one or the other nutrient, but the most important changes were observed when both nutrients were provided. The increased availability of DIC and NH4+ significantly improved the photosynthetic efficiency and capacity of endosymbionts, in turn enhancing the host calcification rate. Overall, these results suggest that in hospite symbionts are co-limited by nitrogen and carbon availability for an optimal photosynthesis.
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14
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Delay C, Chapman K, Taleski M, Wang Y, Tyagi S, Xiong Y, Imin N, Djordjevic MA. CEP3 levels affect starvation-related growth responses of the primary root. J Exp Bot 2019; 70:4763-4774. [PMID: 31173100 PMCID: PMC6760281 DOI: 10.1093/jxb/erz270] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2018] [Accepted: 05/16/2019] [Indexed: 05/22/2023]
Abstract
CEPs (C-TERMINALLY ENCODED PEPTIDEs) inhibit Arabidopsis primary root growth by unknown mechanisms. We investigated how CEP3 levels control primary root growth. CEP3 peptide application decreased cell division, S-phase cell number, root meristematic cell number, and meristem zone (MZ) size in a dose- and CEP RECEPTOR1-dependent manner. Grafting showed that CEP3-dependent growth inhibition requires root and shoot CEPR1. CEP3 induced mitotic quiescence in MZ cells significantly faster than that induced by nutrient limitation alone. CEP3 also inhibited the restoration of S-phase to mitotically quiescence cells by nutrient resupply without quantitatively reducing TARGET OF RAPAMYCIN (TOR) kinase activity. In contrast, cep3-1 had an increased meristem size and S-phase cell number under nitrogen (N)-limited conditions, but not under N-sufficient conditions. Furthermore, cep3-1 meristematic cells remained in S-phase longer than wild-type cells during a sustained carbon (C) and N limitation. RNA sequencing showed that CEP3 peptide down-regulated genes involved in S-phase entry, cell wall and ribosome biogenesis, DNA replication, and meristem expansion, and up-regulated genes involved in catabolic processes and proteins and peptides that negatively control meristem expansion and root growth. Many of these genes were reciprocally regulated in cep3-1. The results suggest that raising CEP3 induces starvation-related responses that curtail primary root growth under severe nutrient limitation.
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Affiliation(s)
- Christina Delay
- Division of Plant Science, Research School of Biology, College of Medicine, Biology and the Environment, Australian National University, Canberra, ACT, Australia
| | - Kelly Chapman
- Division of Plant Science, Research School of Biology, College of Medicine, Biology and the Environment, Australian National University, Canberra, ACT, Australia
| | - Michael Taleski
- Division of Plant Science, Research School of Biology, College of Medicine, Biology and the Environment, Australian National University, Canberra, ACT, Australia
| | - Yaowei Wang
- Shanghai Center for Plant Stress Biology, Chinese Academy of Science Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, PR China
- University of Chinese Academy of Sciences, Shanghai, PR China
| | - Sonika Tyagi
- Australian Genome Research Facility Ltd, The Walter and Eliza Hall Institute, Parkville, VIC, Australia
- Present address: Bioinformatics Research Group, Monash University, Clayton, VIC, Australia 3800
| | - Yan Xiong
- Shanghai Center for Plant Stress Biology, Chinese Academy of Science Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, PR China
| | - Nijat Imin
- Division of Plant Science, Research School of Biology, College of Medicine, Biology and the Environment, Australian National University, Canberra, ACT, Australia
- Correspondence: or Present address: School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Michael A Djordjevic
- Division of Plant Science, Research School of Biology, College of Medicine, Biology and the Environment, Australian National University, Canberra, ACT, Australia
- Correspondence: or Present address: School of Biological Sciences, University of Auckland, Auckland, New Zealand
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15
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Li L, Ding M, Lan Z, Zhao Y, Chen J. Light Availability and Patterns of Allocation to Reproductive and Vegetative Biomass in the Sexes of the Dioecious Macrophyte Vallisneria spinulosa. Front Plant Sci 2019; 10:572. [PMID: 31130977 PMCID: PMC6510307 DOI: 10.3389/fpls.2019.00572] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Accepted: 04/16/2019] [Indexed: 05/30/2023]
Abstract
Environmental changes, e.g., eutrophication, in aquatic ecosystems can greatly alter light available to submerged macrophytes. In dioecious plants, given potential for sex-specific differences in resource requirements (i.e., high-carbon for seeds vs. high-nitrogen for pollen), females and males are expected to divergently adjust allocations toward resource acquisition structures when resources are limited during growth. Here, Vallisneria spinulosa was used as a representative dioecious submerged macrophyte to detect sex-specific responses to light limitation and assess whether sexual dimorphism varied with resource availability. Plants were grown under varying levels of light availability in nine outdoor mesocosms for 14 weeks. Late in the reproductive season, allocations to vegetative and reproductive traits for both sexes were determined and relative allocation to reproduction vs. vegetative growth was analyzed. Female and male reproductive plants differed in adjustments of resource allocation in response to light availability. Under low light, females showed a smaller reduction in allocation of resources to vegetative tissues and greater leaf area than males, suggesting female plasticity to increase carbon capture. Under low light, males showed a smaller reduction in reproductive allocation than females (flowers and inflorescences in males vs. fruits in females), suggesting that carbon limitation has greater impacts on sexual reproduction by females than males. Our study provides evidence of differences in reproductive costs and currencies for female vs. male reproduction in aquatic macrophytes, as V. spinulosa responded plastically to reduced light, with sexually dimorphic allocation strategies. Sex-related resource currencies are potentially important drivers for sex-specific variations in allocation patterns, with females safeguarding their vegetative carbon-rich biomass to satisfy future fruit and seed production.
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Affiliation(s)
- Lei Li
- Jiangxi Province Key Laboratory of Watershed Ecosystem Change and Biodiversity, Center for Watershed Ecology, Institute of Life Science and School of Life Sciences, Nanchang University, Nanchang, China
- National Ecosystem Research Station of Jiangxi Poyang Lake Wetland, Nanchang, China
| | - Mingming Ding
- Jiangxi Province Key Laboratory of Watershed Ecosystem Change and Biodiversity, Center for Watershed Ecology, Institute of Life Science and School of Life Sciences, Nanchang University, Nanchang, China
| | - Zhichun Lan
- Jiangxi Province Key Laboratory of Watershed Ecosystem Change and Biodiversity, Center for Watershed Ecology, Institute of Life Science and School of Life Sciences, Nanchang University, Nanchang, China
- National Ecosystem Research Station of Jiangxi Poyang Lake Wetland, Nanchang, China
| | - Yao Zhao
- Jiangxi Province Key Laboratory of Watershed Ecosystem Change and Biodiversity, Center for Watershed Ecology, Institute of Life Science and School of Life Sciences, Nanchang University, Nanchang, China
| | - Jiakuan Chen
- Jiangxi Province Key Laboratory of Watershed Ecosystem Change and Biodiversity, Center for Watershed Ecology, Institute of Life Science and School of Life Sciences, Nanchang University, Nanchang, China
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, Fudan University, Shanghai, China
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16
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Huang J, Hammerbacher A, Weinhold A, Reichelt M, Gleixner G, Behrendt T, van Dam NM, Sala A, Gershenzon J, Trumbore S, Hartmann H. Eyes on the future - evidence for trade-offs between growth, storage and defense in Norway spruce. New Phytol 2019; 222:144-158. [PMID: 30289558 DOI: 10.1111/nph.15522] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 09/28/2018] [Indexed: 05/20/2023]
Abstract
Carbon (C) allocation plays a central role in tree responses to environmental changes. Yet, fundamental questions remain about how trees allocate C to different sinks, for example, growth vs storage and defense. In order to elucidate allocation priorities, we manipulated the whole-tree C balance by modifying atmospheric CO2 concentrations [CO2 ] to create two distinct gradients of declining C availability, and compared how C was allocated among fluxes (respiration and volatile monoterpenes) and biomass C pools (total biomass, nonstructural carbohydrates (NSC) and secondary metabolites (SM)) in well-watered Norway spruce (Picea abies) saplings. Continuous isotope labelling was used to trace the fate of newly-assimilated C. Reducing [CO2 ] to 120 ppm caused an aboveground C compensation point (i.e. net C balance was zero) and resulted in decreases in growth and respiration. By contrast, soluble sugars and SM remained relatively constant in aboveground young organs and were partially maintained with a constant allocation of newly-assimilated C, even at expense of root death from C exhaustion. We conclude that spruce trees have a conservative allocation strategy under source limitation: growth and respiration can be downregulated to maintain 'operational' concentrations of NSC while investing newly-assimilated C into future survival by producing SM.
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Affiliation(s)
- Jianbei Huang
- Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, 07745, Jena, Germany
| | - Almuth Hammerbacher
- Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745, Jena, Germany
- Department of Zoology and Entomology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Private Bag X20, 0028, Pretoria, South Africa
| | - Alexander Weinhold
- German Centre for Integrative Biodiversity Research, Deutscher Platz 5e, 04103, Leipzig, Germany
| | - Michael Reichelt
- Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745, Jena, Germany
| | - Gerd Gleixner
- Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, 07745, Jena, Germany
| | - Thomas Behrendt
- Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, 07745, Jena, Germany
| | - Nicole M van Dam
- German Centre for Integrative Biodiversity Research, Deutscher Platz 5e, 04103, Leipzig, Germany
- Institute of Biodiversity, Friedrich Schiller University, Dornburger-Str. 159, 07743, Jena, Germany
| | - Anna Sala
- Division of Biological Sciences, The University of Montana, Missoula, MT, 59812, USA
| | - Jonathan Gershenzon
- Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745, Jena, Germany
| | - Susan Trumbore
- Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, 07745, Jena, Germany
| | - Henrik Hartmann
- Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, 07745, Jena, Germany
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17
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Wiley E, Hoch G, Landhäusser SM. Dying piece by piece: carbohydrate dynamics in aspen (Populus tremuloides) seedlings under severe carbon stress. J Exp Bot 2017; 68:5221-5232. [PMID: 29036658 PMCID: PMC5853906 DOI: 10.1093/jxb/erx342] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 09/14/2017] [Indexed: 05/17/2023]
Abstract
Carbon starvation as a mechanism of tree mortality is poorly understood. We exposed seedlings of aspen (Populus tremuloides) to complete darkness at 20 or 28 °C to identify minimum non-structural carbohydrate (NSC) concentrations at which trees die and to see if these levels vary between organs or with environmental conditions. We also first grew seedlings under different shade levels to determine if size affects survival time under darkness due to changes in initial NSC concentration and pool size and/or respiration rates. Darkness treatments caused a gradual dieback of tissues. Even after half the stem had died, substantial starch reserves were still present in the roots (1.3-3% dry weight), indicating limitations to carbohydrate remobilization and/or transport during starvation in the absence of water stress. Survival time decreased with increased temperature and with increasing initial shade level, which was associated with smaller biomass, higher respiration rates, and initially smaller NSC pool size. Dead tissues generally contained no starch, but sugar concentrations were substantially above zero and differed between organs (~2% in stems up to ~7.5% in leaves) and, at times, between temperature treatments and initial, pre-darkness shade treatments. Minimum root NSC concentrations were difficult to determine because dead roots quickly began to decompose, but we identify 5-6% sugar as a potential threshold for living roots. This variability may complicate efforts to identify critical NSC thresholds below which trees starve.
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Affiliation(s)
- Erin Wiley
- Department of Renewable Resources, University of Alberta, Edmonton, Canada
- Correspondence:
| | - Günter Hoch
- Department of Environmental Sciences - Botany, University of Basel, Basel, Switzerland
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18
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Bajcz AW, Drummond FA. Flower power: Floral and resource manipulations reveal how and why reproductive trade-offs occur for lowbush blueberry ( Vaccinium angustifolium). Ecol Evol 2017; 7:5645-5659. [PMID: 28808544 PMCID: PMC5551106 DOI: 10.1002/ece3.3109] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 05/04/2017] [Accepted: 05/08/2017] [Indexed: 11/24/2022] Open
Abstract
Plant reproductive trade-offs are thought to be caused by resource limitations or other constraints, but more empirical support for these hypotheses would be welcome. Additionally, quantitative characterization of these trade-offs, as well as consideration of whether they are linear, could yield additional insights. We expanded our flower removal research on lowbush blueberry (Vaccinium angustifolium) to explore the nature of and causes of its reproductive trade-offs. We used fertilization, defoliation, positionally biased flower removal, and multiple flower removal levels to discern why reproductive trade-offs occur in this taxon and to plot these trade-offs along two continuous axes. We found evidence through defoliation that vegetative mass per stem may trade off with reproductive effort in lowbush blueberry because the two traits compete for limited carbon. Also, several traits including ripe fruit production per reproductive node and fruit titratable acidity may be "sink-limited"-they decline with increasing reproductive effort because average reproductive structure quality declines. We found no evidence that reproductive trade-offs were caused by nitrogen limitation. Use of reproductive nodes remaining per stem as a measure of reproductive effort indicated steeper trade-offs than use of the proportion of nodes remaining. For five of six traits, we found evidence that the trade-off could be concave down or up instead of strictly linear. Synthesis. To date, studies have aimed primarily at identifying plant reproductive trade-offs. However, understanding how and why these trade-offs occur represent the exciting and necessary next steps for this line of inquiry.
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Affiliation(s)
- Alex W. Bajcz
- School of Biology and EcologyUniversity of Maine at OronoOronoMEUSA
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19
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Turner CB, Wade BD, Meyer JR, Sommerfeld BA, Lenski RE. Evolution of organismal stoichiometry in a long-term experiment with Escherichia coli. R Soc Open Sci 2017; 4:170497. [PMID: 28791173 PMCID: PMC5541568 DOI: 10.1098/rsos.170497] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 06/21/2017] [Indexed: 05/25/2023]
Abstract
Organismal stoichiometry refers to the relative proportion of chemical elements in the biomass of organisms, and it can have important effects on ecological interactions from population to ecosystem scales. Although stoichiometry has been studied extensively from an ecological perspective, much less is known about the rates and directions of evolutionary changes in elemental composition. We measured carbon, nitrogen and phosphorus content of 12 Escherichia coli populations that evolved under controlled carbon-limited, serial-transfer conditions for 50 000 generations. The bacteria evolved higher relative nitrogen and phosphorus content, consistent with selection for increased use of the more abundant elements. Total carbon assimilated also increased, indicating more efficient use of the limiting element. We also measured stoichiometry in one population repeatedly through time. Stoichiometry changed more rapidly in early generations than later on, similar to the trajectory seen for competitive fitness. Altogether, our study shows that stoichiometry evolved over long time periods, and that it did so in a predictable direction, given the carbon-limited environment.
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Affiliation(s)
- Caroline B. Turner
- Ecology, Evolutionary Biology and Behavior Program, Michigan State University, East Lansing, MI, USA
- BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, MI, USA
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA, USA
| | - Brian D. Wade
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, USA
| | - Justin R. Meyer
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA
| | - Brooke A. Sommerfeld
- Department of Integrative Biology, Michigan State University, East Lansing, MI, USA
| | - Richard E. Lenski
- Ecology, Evolutionary Biology and Behavior Program, Michigan State University, East Lansing, MI, USA
- BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, MI, USA
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, USA
- Department of Integrative Biology, Michigan State University, East Lansing, MI, USA
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
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20
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Karmann S, Panke S, Zinn M. The Bistable Behaviour of Pseudomonas putida KT2440 during PHA Depolymerization under Carbon Limitation. Bioengineering (Basel) 2017; 4:bioengineering4020058. [PMID: 28952537 PMCID: PMC5590454 DOI: 10.3390/bioengineering4020058] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2017] [Revised: 06/12/2017] [Accepted: 06/13/2017] [Indexed: 11/16/2022] Open
Abstract
Poly(hydroxyalkanoates) (PHAs) are bacterial polyesters offering a biodegradable alternative to petrochemical plastics. The intracellular formation and degradation of PHAs is a dynamic process that strongly depends on the availability of carbon and other nutrients. Carbon excess and nitrogen limitation are considered to favor PHA accumulation, whereas carbon limitation triggers PHA depolymerization when all other essential nutrients are present in excess. We studied the population dynamics of Pseudomonas putida KT2440 at the single cell level during different physiological conditions, favoring first PHA polymerization during growth on octanoic acid, and then PHA depolymerization during carbon limitation. PHAs accumulate intracellularly in granules, and were proposed to separate preferentially together with nucleic acids, leading to two daughter cells containing approximately equal amounts of PHA. However, we could show that such P. putida KT2440 cells show bistable behavior when exposed to carbon limitation, and separate into two subpopulations: one with high and one with low PHA. This suggests an asymmetric PHA distribution during cell division under carbon limitation, which has a significant influence on our understanding of PHA mobilization.
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Affiliation(s)
- Stephanie Karmann
- Institute of Life Technologies, University of Applied Sciences and Arts Western Switzerland (HES-SO Valais), Route du Rawyl 47, 1950 Sion, Switzerland.
- Department of Biosystems Science and Engineering, ETH Zurich (ETHZ), Mattenstrasse 26, 4058 Basel, Switzerland.
| | - Sven Panke
- Department of Biosystems Science and Engineering, ETH Zurich (ETHZ), Mattenstrasse 26, 4058 Basel, Switzerland.
| | - Manfred Zinn
- Institute of Life Technologies, University of Applied Sciences and Arts Western Switzerland (HES-SO Valais), Route du Rawyl 47, 1950 Sion, Switzerland.
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Truffault V, Gest N, Garchery C, Florian A, Fernie AR, Gautier H, Stevens RG. Reduction of MDHAR activity in cherry tomato suppresses growth and yield and MDHAR activity is correlated with sugar levels under high light. Plant Cell Environ 2016; 39:1279-92. [PMID: 26510400 DOI: 10.1111/pce.12663] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 10/01/2015] [Accepted: 10/18/2015] [Indexed: 05/08/2023]
Abstract
Ascorbate is oxidized into the radical monodehydroascorbate (MDHA) through ascorbate oxidase or peroxidase activity or non-enzymatically by reactive oxygen species. Regeneration of ascorbate from MDHA is ensured by the enzyme MDHA reductase (MDHAR). Previous work has shown that growth processes and yield can be altered by modifying the activity of enzymes that recycle ascorbate; therefore, we have studied similar processes in cherry tomato (Solanum lycopersium L.) under- or overexpressing MDHAR. Physiological and metabolic characterization of these lines was carried out under different light conditions or by manipulating the source-sink ratio. Independently of the light regime, slower early growth of all organs was observed in MDHAR silenced lines, decreasing final fruit yield. Photosynthesis was altered as was the accumulation of hexoses and sucrose in a light-dependent manner in plantlets. Sucrose accumulation was also repressed in young fruits and final yield of MDHAR silenced lines showed a stronger decrease under carbon limitation, and the phenotype was partially restored by reducing fruit load. Ascorbate and MDHA appear to be involved in control of growth and sugar metabolism in cherry tomato and the associated enzymes could be potential targets for yield improvement.
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Affiliation(s)
- Vincent Truffault
- INRA, UR-1052, Génétique et Amélioration des Fruits et Légumes, CS60094, 84143, Montfavet, France
- INRA, UR-1115, Plantes et Systèmes de Culture Horticoles, CS40509, 84914, Avignon Cedex 9, France
| | - Noé Gest
- INRA, UR-1052, Génétique et Amélioration des Fruits et Légumes, CS60094, 84143, Montfavet, France
| | - Cécile Garchery
- INRA, UR-1052, Génétique et Amélioration des Fruits et Légumes, CS60094, 84143, Montfavet, France
| | - Alexandra Florian
- Max-Planck-Institute of Molecular Plant Physiology, Am Muehlenberf 1, 14476, Potsdam-Golm, Germany
| | - Alisdair R Fernie
- Max-Planck-Institute of Molecular Plant Physiology, Am Muehlenberf 1, 14476, Potsdam-Golm, Germany
| | - Hélène Gautier
- INRA, UR-1115, Plantes et Systèmes de Culture Horticoles, CS40509, 84914, Avignon Cedex 9, France
| | - Rebecca G Stevens
- INRA, UR-1052, Génétique et Amélioration des Fruits et Légumes, CS60094, 84143, Montfavet, France
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22
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Abstract
Plants reward microbial and animal mutualists with carbohydrates to obtain nutrients, defense, pollination, and dispersal. Under a fixed carbon budget, plants must allocate carbon to their mutualists at the expense of allocation to growth, reproduction, or storage. Such carbon trade-offs are indirectly expressed when a plant exhibits reduced growth or fecundity in the presence of its mutualist. Because carbon regulates the costs of all plant mutualisms, carbon dynamics are a common platform for integrating these costs in the face of ecological complexity and context dependence. The ecophysiology of whole-plant carbon allocation could thus elucidate the ecology and evolution of plant mutualisms. If mutualisms are costly to plants, then they must be important but frequently underestimated sinks in the terrestrial carbon cycle.
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Affiliation(s)
- Elizabeth G Pringle
- Michigan Society of Fellows, University of Michigan, Ann Arbor, MI, 48109, USA
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, 48109, USA
- Present address: Max Planck Institute for Chemical Ecology, Beutenberg Campus, Hans-Knoell-Strasse 8, Jena, 07745, Germany
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23
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Dang HS, Zhang KR, Zhang QF, Xu YM. Temporal variations of mobile carbohydrates in Abies fargesii at the upper tree limits. Plant Biol (Stuttg) 2015; 17:106-113. [PMID: 24954386 DOI: 10.1111/plb.12191] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2013] [Accepted: 03/10/2014] [Indexed: 06/03/2023]
Abstract
Low temperatures are associated high-altitude treelines, but the functional mechanism of treeline formation remains controversial. The relative contributions of carbon limitation (source activity) and growth limitation (sink activity) require more tests across taxa and regions. We examined temporal variations of mobile carbon supply in different tissues of Abies fargesii across treeline ecotones on north- and south-facing slopes of the Qinling Mountains, China. Non-structural carbohydrate (NSC) concentrations in tissues along the altitudinal gradient on both slopes changed significantly in the early and late growing season, but not in the mid-growing season, indicating the season-dependent carbon supply status. Late in the growing season on both slopes, trees at the upper limits had the highest NSC concentrations and total soluble sugars and lowest starch concentrations compared to trees at the lower elevations. NSC concentrations tended to increase in needles and branches throughout the growing season with increasing elevation on both slopes, but declined in roots and stems. NSC concentrations across sampling dates also indicated increases in needles and branches, and decreases in roots and stem with increasing elevation. Overall altitudinal trends of NSC in A. fargesii revealed no depletion of mobile carbon reserves at upper elevation limits, suggesting limitation of sink activity dominates tree life across treeline ecotones in both north- and south-facing slopes. Carbon reserves in storage tissues (especially roots) in the late growing season might also play an important role in winter survival and early growth in spring at upper elevations on both slopes, which define the uppermost limit of A. fargesii.
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Affiliation(s)
- H S Dang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
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24
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Zhao J, Hartmann H, Trumbore S, Ziegler W, Zhang Y. High temperature causes negative whole-plant carbon balance under mild drought. New Phytol 2013; 200:330-339. [PMID: 23822669 DOI: 10.1111/nph.12400] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 06/06/2013] [Indexed: 05/29/2023]
Abstract
Theoretically, progressive drought can force trees into negative carbon (C) balance by reducing stomatal conductance to prevent water loss, which also decreases C assimilation. At higher temperatures, negative C balance should be initiated at higher soil moisture because of increased respiratory demand and earlier stomatal closure. Few data are available on how these theoretical relationships integrate over the whole plant. We exposed Thuja occidentalis to progressive drought under three temperature conditions (15, 25, and 35°C), and measured C and water fluxes using a whole-tree chamber design. High transpiration rates at higher temperatures led to a rapid decline in soil moisture. During the progressive drought, soil moisture-driven changes in photosynthesis had a greater impact on the whole-plant C balance than respiration. The soil moisture content at which whole-plant C balance became negative increased with temperature, mainly as a result of higher respiration rates and an earlier onset of stomatal closure under a warmer condition. Our results suggest that the effect of drought on whole-plant C balance is highly temperature-dependent. High temperature causes a negative C balance even under mild drought and may increase the risk of C starvation.
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Affiliation(s)
- Junbin Zhao
- Max Planck Institute for Biogeochemistry, Jena, 07745, Germany
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, 666303, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Henrik Hartmann
- Max Planck Institute for Biogeochemistry, Jena, 07745, Germany
| | - Susan Trumbore
- Max Planck Institute for Biogeochemistry, Jena, 07745, Germany
| | | | - Yiping Zhang
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, 666303, China
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Eyles A, Pinkard EA, Davies NW, Corkrey R, Churchill K, O'Grady AP, Sands P, Mohammed C. Whole-plant versus leaf-level regulation of photosynthetic responses after partial defoliation in Eucalyptus globulus saplings. J Exp Bot 2013; 64:1625-36. [PMID: 23382548 PMCID: PMC3617827 DOI: 10.1093/jxb/ert017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Increases in photosynthetic capacity (A1500) after defoliation have been attributed to changes in leaf-level biochemistry, water, and/or nutrient status. The hypothesis that transient photosynthetic responses to partial defoliation are regulated by whole-plant (e.g. source-sink relationships or changes in hydraulic conductance) rather than leaf-level mechanisms is tested here. Temporal variation in leaf-level gas exchange, chemistry, whole-plant soil-to-leaf hydraulic conductance (KP), and aboveground biomass partitioning were determined to evaluate mechanisms responsible for increases in A1500 of Eucalyptus globulus L. potted saplings. A1500 increased in response to debudding (B), partial defoliation (D), and combined B&D treatments by up to 36% at 5 weeks after treatment. Changes in leaf-level factors partly explained increases in A1500 of B and B&D treatments but not for D treatment. By week 5, saplings in B, B&D, and D treatments had similar leaf-specific KP to control trees by maintaining lower midday water potentials and higher transpiration rate per leaf area. Whole-plant source:sink ratios correlated strongly with A1500. Further, unlike KP, temporal changes in source:sink ratios tracked well with those observed for A1500. The results indicate that increases in A1500 after partial defoliation treatments were largely driven by an increased demand for assimilate by developing sinks rather than improvements in whole-plant water relations and changes in leaf-level factors. Three carbohydrates, galactional, stachyose, and, to a lesser extent, raffinose, correlated strongly with photosynthetic capacity, indicating that these sugars may function as signalling molecules in the regulation of longer term defoliation-induced gas exchange responses.
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Affiliation(s)
- Alieta Eyles
- Cooperative Research Centre for Forestry, Private Bag 12, Hobart, Tasmania 7001, Australia.
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