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Li L, Li J, Wang X, Ullah S, Lin S. Reponses of morphological and biochemical traits of bamboo trees under elevated atmospheric O 3 enrichment. ENVIRONMENTAL RESEARCH 2024; 252:119069. [PMID: 38735376 DOI: 10.1016/j.envres.2024.119069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2024] [Revised: 05/01/2024] [Accepted: 05/02/2024] [Indexed: 05/14/2024]
Abstract
Dwarf bamboo (Indocalamus decorus) is an O3-tolerant plant species. To identify the possible mechanism and response of leaf morphological, antioxidant, and anatomical characteristics to elevated atmospheric O3 (EO3) concentrations, we exposed three-year-old I. decorus seedlings to three O3 levels (low O3-LO: ambient air; medium O3-MO: Ambient air+70 ppb high O3-HO: Ambient air+140 ppb O3) over a growing season using open-top chambers. Leaf shape and stomatal characteristics, and leaf microscopic structure of I. decorus were examined. The results indicated that 1) the stomata O3 flux (Fst) of HO decreased more rapidly under EO3 as the exposure time increased. The foliar O3 injury of HO and MO occurred when AOT40 was 26.62 ppm h and 33.20 ppm h, respectively, 2) under EO3, leaf number, leaf mass per area, leaf area, and stomata length/width all decreased, while leaf thickness, stomatal density, width, and area increased compared to the control, 3) MDA and total soluble protein contents all showed significantly increase under HO (36.57% and 32.77%) and MO(31.91% and 19.52%) while proline contents only increased under HO(33.27%). 4) MO and HO increased bulliform cells numbers in the leaves by 6.28% and 23.01%, respectively. HO reduced the transverse area of bulliform cells by 13.73%, while MO treatments had no effect, and 5) the number of fusoid cells interspace, the transverse area of fusoid cells interspace, and mesophyll thickness of HO significantly increased by 11.16%, 28.58%, and 13.42%, respectively. In conclusion, I. decorus exhibits strong O3 tolerance characteristics, which stem from adaptions in the leaf's morphological, structural, antioxidant, and anatomical features. One critical attribute was the enlargement of the bulliform cell transverse area and the transverse area of fusoid cells interspace that drove this resistance to O3. Local bamboo species with high resistance to O3 pollution thus need to be promoted for sustained productivity and ecosystem services in areas with high O3 pollution.
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Affiliation(s)
- Li Li
- Co-Innovation Center for Sustainable Forestry in Southern China, Bamboo Research Institute, Nanjing Forestry University, Nanjing, Jiangsu 210037, China.
| | - Jinling Li
- Co-Innovation Center for Sustainable Forestry in Southern China, Bamboo Research Institute, Nanjing Forestry University, Nanjing, Jiangsu 210037, China; Guangxi Eco-engineering Vocational and Technical College, Liuzhou, Guangxi, China
| | - Xiaoke Wang
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Sami Ullah
- School of Geography, Earth and Environmental Sciences & Birmingham Institute of Forest Research, University of Birmingham, UK.
| | - Shuyan Lin
- Co-Innovation Center for Sustainable Forestry in Southern China, Bamboo Research Institute, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
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Xu Y, Feng Z, Peng J, Uddling J. Variations in leaf anatomical characteristics drive the decrease of mesophyll conductance in poplar under elevated ozone. GLOBAL CHANGE BIOLOGY 2023; 29:2804-2823. [PMID: 36718962 DOI: 10.1111/gcb.16621] [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: 11/21/2022] [Accepted: 01/18/2023] [Indexed: 05/31/2023]
Abstract
Decline in mesophyll conductance (gm ) plays a key role in limiting photosynthesis in plants exposed to elevated ozone (O3 ). Leaf anatomical traits are known to influence gm , but the potential effects of O3 -induced changes in leaf anatomy on gm have not yet been clarified. Here, two poplar clones were exposed to elevated O3 . The effects of O3 on the photosynthetic capacity and anatomical characteristics were assessed to investigate the leaf anatomical properties that potentially affect gm . We also conducted global meta-analysis to explore the general response patterns of gm and leaf anatomy to O3 exposure. We found that the O3 -induced reduction in gm was critical in limiting leaf photosynthesis. Changes in liquid-phase conductance rather than gas-phase conductance drive the decline in gm under elevated O3, and this effect was associated with thicker cell walls and smaller chloroplast sizes. The effects of O3 on palisade and spongy mesophyll cell traits and their contributions to gm were highly genotype-dependent. Our results suggest that, while anatomical adjustments under elevated O3 may contribute to defense against O3 stress, they also cause declines in gm and photosynthesis. These results provide the first evidence of anatomical constraints on gm under elevated O3 .
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Affiliation(s)
- Yansen Xu
- Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD), Nanjing University of Information Science & Technology, Nanjing, China
- Key Laboratory of Ecosystem Carbon Source and Sink, China Meteorological Administration (ECSS-CMA),School of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing, China
| | - Zhaozhong Feng
- Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD), Nanjing University of Information Science & Technology, Nanjing, China
- Key Laboratory of Ecosystem Carbon Source and Sink, China Meteorological Administration (ECSS-CMA),School of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing, China
| | - Jinlong Peng
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
| | - Johan Uddling
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
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Kivimäenpää M, Riikonen J, Valolahti H, Elina H, Holopainen JK, Holopainen T. Effects of elevated ozone and warming on terpenoid emissions and concentrations of Norway spruce depend on needle phenology and age. TREE PHYSIOLOGY 2022; 42:1570-1586. [PMID: 35183060 PMCID: PMC9366870 DOI: 10.1093/treephys/tpac019] [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: 06/03/2021] [Accepted: 02/01/2022] [Indexed: 06/14/2023]
Abstract
Norway spruce (Picea abies (L.) Karst) trees are affected by ongoing climate change, including warming and exposure to phytotoxic levels of ozone. Non-volatile terpenoids and volatile terpenoids (biogenic organic volatile compounds, BVOCs) protect spruce against biotic and abiotic stresses. BVOCs also affect the atmosphere's oxidative capacity. Four-year-old Norway spruce were exposed to elevated ozone (EO) (1.4 × ambient) and warming (1.1 °C + ambient air) alone and in combination on an open-field exposure site in Central Finland. Net photosynthesis, needle terpenoid concentrations and BVOC emissions were measured four times during the experiment's second growing season: after bud opening in May, during the mid-growing season in June, and after needle maturation in August and September. Warming increased terpene concentrations in May due to advanced phenology and decreased them at the end of the growing season in matured current-year needles. Ozone enhanced these effects of warming on several compounds. Warming decreased concentrations of oxygenated sesquiterpenes in previous-year needles. Decreased emissions of oxygenated monoterpenes by warming and ozone alone in May were less prominent when ozone and warming were combined. A similar interactive treatment response in isoprene, camphene, tricyclene and α-pinene was observed in August when the temperature and ozone concentration was high. The results suggest long-term warming may reduce the terpenoid-based defence capacity of young spruce, but the defence capacity can be increased during the most sensitive growth phase (after bud break), and when high temperatures or ozone concentrations co-occur. Reduced BVOC emissions from young spruce may decrease the atmosphere's oxidative capacity in the warmer future, but the effect of EO may be marginal because less reactive minor compounds are affected.
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Affiliation(s)
| | | | - Hanna Valolahti
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 1627, Kuopio 70211, Finland
- Ramboll, Niemenkatu 73, Lahti 15140, Finland
| | - Häikiö Elina
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 1627, Kuopio 70211, Finland
- South Savo Centre for Economic Development, Transport and the Environment, PO Box 164, Mikkeli 50101, Finland
| | - Jarmo K Holopainen
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 1627, Kuopio 70211, Finland
| | - Toini Holopainen
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 1627, Kuopio 70211, Finland
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Wang Y, Xu S, Zhang W, Li Y, Wang N, He X, Chen W. Responses of growth, photosynthesis and related physiological characteristics in leaves of Acer ginnala Maxim. to increasing air temperature and/or elevated O 3. PLANT BIOLOGY (STUTTGART, GERMANY) 2021; 23 Suppl 1:221-231. [PMID: 33527649 DOI: 10.1111/plb.13240] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 01/12/2021] [Accepted: 01/21/2021] [Indexed: 05/26/2023]
Abstract
Regional warming and atmospheric ozone (O3 ) pollution are two of the most important environmental issues, and commonly coexist in many areas. Both factors have an intense impact on plants. However, little information is available on the combined and interactive effects of air warming and elevated O3 concentrations on physiological characteristics of plants. To explore this issue, we studied variations in growth, photosynthesis and physiological characteristics of leaves of Acer ginnala seedlings exposed to control (ambient temperature and O3 ), increasing air temperature (ambient temperature + 2 °C), elevated O3 (ambient O3 concentration + 40 ppb) and a combination of the two abiotic factors at different phenological stages by using open-top chambers. The results showed that increasing air temperature had no significant effect on growth, but increased photosynthesis and antioxidant enzyme activity at the leaf unfolding and defoliation stages. In contrast, elevated O3 decreased growth and photosynthesis and caused oxidative stress injury in A. ginnala leaves at each phenological stage. The combination of increasing air temperature and elevated O3 improved growth and net photosynthetic rates of tested plants and alleviated the oxidative stress compared to O3 alone. Our findings demonstrated that moderate warming was beneficial to A. ginnala at leaf unfolding and defoliation stages, and alleviated the adverse effects of O3 stress on growth, photosynthesis and the antioxidant system. These results will provide a theoretical reference and scientific basis for the adaptation and response of A. ginnala under regional air warming and atmospheric O3 pollution.
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Affiliation(s)
- Y Wang
- Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110016, China
- University of the Chinese Academy of Sciences, Beijing, 100049, China
| | - S Xu
- Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110016, China
- University of the Chinese Academy of Sciences, Beijing, 100049, China
- Chinese Academy of Sciences Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Shenyang, 110016, China
| | - W Zhang
- College of Environment, Shenyang University, 110044, China
| | - Y Li
- Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110016, China
- Shenyang Arboretum, Chinese Academy of Sciences, Shenyang, 110016, China
| | - N Wang
- Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110016, China
- University of the Chinese Academy of Sciences, Beijing, 100049, China
| | - X He
- Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110016, China
- University of the Chinese Academy of Sciences, Beijing, 100049, China
- Chinese Academy of Sciences Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Shenyang, 110016, China
- Shenyang Arboretum, Chinese Academy of Sciences, Shenyang, 110016, China
| | - W Chen
- Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110016, China
- University of the Chinese Academy of Sciences, Beijing, 100049, China
- Chinese Academy of Sciences Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Shenyang, 110016, China
- Shenyang Arboretum, Chinese Academy of Sciences, Shenyang, 110016, China
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Artemkina NA, Orlova MA, Lukina NV. Spatial Variation in the Concentration of Phenolic Compounds and Nutritional Elements in the Needles of Spruce in Northern Taiga Forests. CONTEMP PROBL ECOL+ 2020. [DOI: 10.1134/s1995425519070023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Ovsyannikov AY, Koteyeva NK. Seasonal movement of chloroplasts in mesophyll cells of two Picea species. PROTOPLASMA 2020; 257:183-195. [PMID: 31410588 DOI: 10.1007/s00709-019-01427-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 07/29/2019] [Indexed: 06/10/2023]
Abstract
Cold acclimation in evergreen conifers of temperate zone is associated with seasonal structural changes of mesophyll cells. Photoprotective reactions include the movement of chloroplasts from summer position when they are located along the cell walls to winter arrangement with their aggregation in one part of the cell. Special spatial arrangement of mesophyll in Picea species with chloroplasts located along the two opposite cell walls causes the very specific pattern of chloroplast movement. To reveal the intracellular apparatus involved in the seasonal organelle position changes, 3D reconstruction of mesophyll cell structure was applied. Two Picea species, P. obovata and P. pungens, from two geographic regions were studied in a 3-year course. The involvement of small transparent vacuoles in the development of cytoplasmic strands penetrating through the central vacuole and connecting two opposite lateral sides of the cell was shown. The nucleus and cytoplasmic organelles including chloroplasts move inwards the strand forming the cytoplasmic conglomerate enclosed by the vacuole at the cell center. Two Picea species have distinct differences in spatial organization of winter mesophyll cells and in structural events leading to its formation. Analysis of Picea species from two geographic regions over 3 years of monitoring reveals dependence of seasonal organelle movement on the dynamics of temperature decline in autumn.
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Affiliation(s)
- A Yu Ovsyannikov
- Institute Botanic Garden: Ural Branch Russian: Academy of Science, 8 Marta St., 202a, Yekaterinburg, 620144, Russia.
| | - N K Koteyeva
- Komarov Botanical Institute Russian Academy of Science, Saint Petersburg, 197376, Russia
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Xu Y, Feng Z, Shang B, Dai L, Uddling J, Tarvainen L. Mesophyll conductance limitation of photosynthesis in poplar under elevated ozone. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 657:136-145. [PMID: 30537576 DOI: 10.1016/j.scitotenv.2018.11.466] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Revised: 11/06/2018] [Accepted: 11/30/2018] [Indexed: 06/09/2023]
Abstract
Finite mesophyll conductance (gm) reduces the rate of CO2 diffusion from the leaf intercellular space to the chloroplast and constitutes a major limitation of photosynthesis in trees. While it is well established that gm is decreased by stressors such as drought and high temperature, few studies have investigated if the phytotoxic air pollutant ozone (O3) affects gm. We quantified the relative importance of three different types of limitations of photosynthesis in poplar trees exposed to elevated O3: decreases in stomatal conductance, gm and biochemical photosynthetic capacity. The O3-induced reductions in light-saturated net photosynthesis were linked to significant declines in gm and biochemical photosynthetic capacity (in particular carboxylation). There was no significant effect of O3 on stomatal conductance. Of the O3-induced limitations on photosynthesis, gm limitation was by far the most important (-16%) while biochemical limitation (-8%) was rather small. Both limitations grew in magnitude over the study period and varied in response to leaf-specific O3 exposure. Our findings suggest that declines in gm may play a key role in limiting photosynthesis of plants exposed to elevated O3, an effect hitherto overlooked.
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Affiliation(s)
- Yansen Xu
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Zhaozhong Feng
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Bo Shang
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lulu Dai
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Johan Uddling
- Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Lasse Tarvainen
- Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden
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Imaging and Spectroscopy of Natural Fluorophores in Pine Needles. PLANTS 2018; 7:plants7010010. [PMID: 29393922 PMCID: PMC5874599 DOI: 10.3390/plants7010010] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 01/24/2018] [Accepted: 01/29/2018] [Indexed: 02/03/2023]
Abstract
Many plant tissues fluoresce due to the natural fluorophores present in cell walls or within the cell protoplast or lumen. While lignin and chlorophyll are well-known fluorophores, other components are less well characterized. Confocal fluorescence microscopy of fresh or fixed vibratome-cut sections of radiata pine needles revealed the presence of suberin, lignin, ferulate, and flavonoids associated with cell walls as well as several different extractive components and chlorophyll within tissues. Comparison of needles in different physiological states demonstrated the loss of chlorophyll in both chlorotic and necrotic needles. Necrotic needles showed a dramatic change in the fluorescence of extractives within mesophyll cells from ultraviolet (UV) excited weak blue fluorescence to blue excited strong green fluorescence associated with tissue browning. Comparisons were made among fluorophores in terms of optimal excitation, relative brightness compared to lignin, and the effect of pH of mounting medium. Fluorophores in cell walls and extractives in lumens were associated with blue or green emission, compared to the red emission of chlorophyll. Autofluorescence is, therefore, a useful method for comparing the histology of healthy and diseased needles without the need for multiple staining techniques, potentially aiding visual screening of host resistance and disease progression in needle tissue.
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Fernandes FF, Cardoso-Gustavson P, Alves ES. Synergism between ozone and light stress: structural responses of polyphenols in a woody Brazilian species. CHEMOSPHERE 2016; 155:573-582. [PMID: 27155473 DOI: 10.1016/j.chemosphere.2016.04.076] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 04/11/2016] [Accepted: 04/20/2016] [Indexed: 06/05/2023]
Abstract
Microscopic studies on isolated ozone (O3) effects or on those in synergy with light stress commonly report the induction of polyphenols that exhibit different aspects within the vacuole of photosynthesizing cells. It has been assumed that these different aspects are randomly spread in the symptomatic (injured) regions of the leaf blade. Interestingly, secretory ducts that constitutively produce polyphenols also exhibit these same variations in their vacuolar aspect, in a spatial sequence related to the destiny of these cells (e.g., programmed cell death (PCD) in lytic secretion processes). Here, we demonstrate that the deposition pattern of polyphenols prior to the establishment of the hypersensitive-like response, a type of PCD caused by O3, follows the same one observed in the epithelial cells of the constitutive lysigenous secretory ducts. Astronium graveolens, an early secondary Brazilian woody species, was selected based on its susceptibility to high light and presence of secretory ducts. The synergism effects were assessed by exposing plants to the high O3 concentrations at an urban site in São Paulo City. Confocal, widefield and light microscopies were used to examine polyphenols' occurrence and aspects. The spatial pattern of polyphenols distribution along the leaflets of plants submitted to the synergism condition, in which a dense vacuolar aspect is the target of a cell destined to death, was also observed in the constitutive secretory cells prior to lysis. This similar structural pattern may be a case of homology of process involving both the constitutive (secretory ducts) and the induced (photosynthesizing cells) defenses.
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Affiliation(s)
- Francine Faia Fernandes
- Programa de Pós-Graduação em Biodiversidade Vegetal e Meio Ambiente, Instituto de Botânica, Av. Miguel Stefano 3687, Água Funda, 04301-902, SP, Brazil.
| | - Poliana Cardoso-Gustavson
- Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Rua Arcturus 03, Jardim Antares, São Bernardo do Campo, 09606-070, Brazil.
| | - Edenise Segala Alves
- Núcleo de Pesquisa em Anatomia, Instituto de Botânica, Av. Miguel Stefano 3687, Água Funda, 04301-902, SP, Brazil.
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Kao YT, Bartel B. Elevated growth temperature decreases levels of the PEX5 peroxisome-targeting signal receptor and ameliorates defects of Arabidopsis mutants with an impaired PEX4 ubiquitin-conjugating enzyme. BMC PLANT BIOLOGY 2015; 15:224. [PMID: 26377801 PMCID: PMC4574000 DOI: 10.1186/s12870-015-0605-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2015] [Accepted: 09/06/2015] [Indexed: 05/29/2023]
Abstract
BACKGROUND Peroxisomes house critical metabolic reactions. For example, fatty acid β-oxidation enzymes, which are essential during early seedling development, are peroxisomal. Peroxins (PEX proteins) are needed to bring proteins into peroxisomes. Most matrix proteins are delivered to peroxisomes by PEX5, a receptor that forms transient pores to escort proteins across the peroxisomal membrane. After cargo delivery, a peroxisome-tethered ubiquitin-conjugating enzyme (PEX4) and peroxisomal ubiquitin-protein ligases mono- or polyubiquitinate PEX5 for recycling back to the cytosol or for degradation, respectively. Arabidopsis pex mutants β-oxidize fatty acids inefficiently and therefore fail to germinate or grow less vigorously. These defects can be partially alleviated by providing a fixed carbon source, such as sucrose, in the growth medium. Despite extensive characterization of peroxisome biogenesis in Arabidopsis grown in non-challenged conditions, the effects of environmental stressors on peroxisome function and pex mutant dysfunction are largely unexplored. RESULTS We surveyed the impact of growth temperature on a panel of pex mutants and found that elevated temperature ameliorated dependence on external sucrose and reduced PEX5 levels in the pex4-1 mutant. Conversely, growth at low temperature exacerbated pex4-1 physiological defects and increased PEX5 levels. Overexpressing PEX5 also worsened pex4-1 defects, implying that PEX5 lingering on the peroxisomal membrane when recycling is impaired impedes peroxisome function. Growth at elevated temperature did not reduce the fraction of membrane-associated PEX5 in pex4-1, suggesting that elevated temperature did not restore PEX4 enzymatic function in the mutant. Moreover, preventing autophagy in pex4-1 did not restore PEX5 levels at high temperature. In contrast, MG132 treatment increased PEX5 levels, implicating the proteasome in degrading PEX5, especially at high temperature. CONCLUSIONS We conclude that growth at elevated temperature increases proteasomal degradation of PEX5 to reduce overall PEX5 levels and ameliorate pex4-1 physiological defects. Our results support the hypothesis that efficient retrotranslocation of PEX5 after cargo delivery is needed not only to make PEX5 available for further rounds of cargo delivery, but also to prevent the peroxisome dysfunction that results from PEX5 lingering in the peroxisomal membrane.
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Affiliation(s)
- Yun-Ting Kao
- Biochemistry and Cell Biology Program, Department of BioSciences, Rice University, Houston, TX, USA.
| | - Bonnie Bartel
- Biochemistry and Cell Biology Program, Department of BioSciences, Rice University, Houston, TX, USA.
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