1
|
Jobe TO, Rahimzadeh Karvansara P, Zenzen I, Kopriva S. Ensuring Nutritious Food Under Elevated CO 2 Conditions: A Case for Improved C 4 Crops. FRONTIERS IN PLANT SCIENCE 2020; 11:1267. [PMID: 33013946 PMCID: PMC7461923 DOI: 10.3389/fpls.2020.01267] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 08/03/2020] [Indexed: 05/04/2023]
Abstract
Global climate change is a challenge for efforts to ensure food security for future generations. It will affect crop yields through changes in temperature and precipitation, as well as the nutritional quality of crops. Increased atmospheric CO2 leads to a penalty in the content of proteins and micronutrients in most staple crops, with the possible exception of C4 crops. It is essential to understand the control of nutrient homeostasis to mitigate this penalty. However, despite the importance of mineral nutrition for plant performance, comparably less is known about the regulation of nutrient uptake and homeostasis in C4 plants than in C3 plants and mineral nutrition has not been a strong focus of the C4 research. Here we review what is known about C4 specific features of nitrogen and sulfur assimilation as well as of homeostasis of other essential elements. We identify the major knowledge gaps and urgent questions for future research. We argue that adaptations in mineral nutrition were an integral part of the evolution of C4 photosynthesis and should be considered in the attempts to engineer C4 photosynthetic mechanisms into C3 crops.
Collapse
Affiliation(s)
- Timothy O Jobe
- Institute for Plant Sciences, Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany
| | - Parisa Rahimzadeh Karvansara
- Institute for Plant Sciences, Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany
| | - Ivan Zenzen
- Institute for Plant Sciences, Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany
| | - Stanislav Kopriva
- Institute for Plant Sciences, Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany
| |
Collapse
|
2
|
Abstract
C4 photosynthesis evolved multiple times independently from ancestral C3 photosynthesis in a broad range of flowering land plant families and in both monocots and dicots. The evolution of C4 photosynthesis entails the recruitment of enzyme activities that are not involved in photosynthetic carbon fixation in C3 plants to photosynthesis. This requires a different regulation of gene expression as well as a different regulation of enzyme activities in comparison to the C3 context. Further, C4 photosynthesis relies on a distinct leaf anatomy that differs from that of C3, requiring a differential regulation of leaf development in C4. We summarize recent progress in the understanding of C4-specific features in evolution and metabolic regulation in the context of C4 photosynthesis.
Collapse
Affiliation(s)
- Urte Schlüter
- Institute of Plant Biochemistry, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich Heine University, 40225 Düsseldorf, Germany; ,
| | - Andreas P M Weber
- Institute of Plant Biochemistry, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich Heine University, 40225 Düsseldorf, Germany; ,
| |
Collapse
|
3
|
Abadie C, Tcherkez G. Plant sulphur metabolism is stimulated by photorespiration. Commun Biol 2019; 2:379. [PMID: 31633070 PMCID: PMC6795801 DOI: 10.1038/s42003-019-0616-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 09/16/2019] [Indexed: 11/08/2022] Open
Abstract
Intense efforts have been devoted to describe the biochemical pathway of plant sulphur (S) assimilation from sulphate. However, essential information on metabolic regulation of S assimilation is still lacking, such as possible interactions between S assimilation, photosynthesis and photorespiration. In particular, does S assimilation scale with photosynthesis thus ensuring sufficient S provision for amino acids synthesis? This lack of knowledge is problematic because optimization of photosynthesis is a common target of crop breeding and furthermore, photosynthesis is stimulated by the inexorable increase in atmospheric CO2. Here, we used high-resolution 33S and 13C tracing technology with NMR and LC-MS to access direct measurement of metabolic fluxes in S assimilation, when photosynthesis and photorespiration are varied via the gaseous composition of the atmosphere (CO2, O2). We show that S assimilation is stimulated by photorespiratory metabolism and therefore, large photosynthetic fluxes appear to be detrimental to plant cell sulphur nutrition.
Collapse
Affiliation(s)
- Cyril Abadie
- Research School of Biology, Australian National University, Canberra, ACT 2601 Australia
- Present Address: IRHS (Institut de Recherche en Horticulture et Semences), UMR 1345, INRA, Agrocampus-Ouest, Université d’Angers, SFR 4207 QuaSaV, 49071 Angers, Beaucouzé France
| | - Guillaume Tcherkez
- Research School of Biology, Australian National University, Canberra, ACT 2601 Australia
| |
Collapse
|
4
|
Jobe TO, Zenzen I, Rahimzadeh Karvansara P, Kopriva S. Integration of sulfate assimilation with carbon and nitrogen metabolism in transition from C3 to C4 photosynthesis. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:4211-4221. [PMID: 31124557 PMCID: PMC6698703 DOI: 10.1093/jxb/erz250] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 05/21/2019] [Indexed: 05/08/2023]
Abstract
The first product of sulfate assimilation in plants, cysteine, is a proteinogenic amino acid and a source of reduced sulfur for plant metabolism. Cysteine synthesis is the convergence point of the three major pathways of primary metabolism: carbon, nitrate, and sulfate assimilation. Despite the importance of metabolic and genetic coordination of these three pathways for nutrient balance in plants, the molecular mechanisms underlying this coordination, and the sensors and signals, are far from being understood. This is even more apparent in C4 plants, where coordination of these pathways for cysteine synthesis includes the additional challenge of differential spatial localization. Here we review the coordination of sulfate, nitrate, and carbon assimilation, and show how they are altered in C4 plants. We then summarize current knowledge of the mechanisms of coordination of these pathways. Finally, we identify urgent questions to be addressed in order to understand the integration of sulfate assimilation with carbon and nitrogen metabolism particularly in C4 plants. We consider answering these questions to be a prerequisite for successful engineering of C4 photosynthesis into C3 crops to increase their efficiency.
Collapse
Affiliation(s)
- Timothy O Jobe
- Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany
| | - Ivan Zenzen
- Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany
| | - Parisa Rahimzadeh Karvansara
- Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany
- Department of Biology, Faculty of Science, University of Mohaghegh Ardabili, Ardabil, Iran
| | - Stanislav Kopriva
- Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany
- Correspondence:
| |
Collapse
|
5
|
Kleinenkuhnen N, Büchel F, Gerlich SC, Kopriva S, Metzger S. A Novel Method for Identification and Quantification of Sulfated Flavonoids in Plants by Neutral Loss Scan Mass Spectrometry. FRONTIERS IN PLANT SCIENCE 2019; 10:885. [PMID: 31333712 PMCID: PMC6625178 DOI: 10.3389/fpls.2019.00885] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 06/21/2019] [Indexed: 05/25/2023]
Abstract
Sulfur is present in plants in a large range of essential primary metabolites, as well as in numerous natural products. Many of these secondary metabolites contain sulfur in the oxidized form of organic sulfate. However, except of glucosinolates, very little is known about other classes of such sulfated metabolites, mainly because of lack of specific and quantitative analytical methods. We developed an LC-MS method to analyze sulfated flavonoids, a group of sulfated secondary metabolites prominent, e.g., in plants of the genus Flaveria. The method uses a linear gradient of methanol/formic acid in water on a Restek Raptor C18 Core-Shell column for separation of the compounds. The sulfated flavonoids are detected by mass spectrometry (MS) in a negative mode, using a neutral loss of 80 Da after a collision induced dissociation. With this method we were also able to quantify the sulfated flavonoids. We could detect all (mono)sulfated flavonoids described before in Flaveria plus a number of new ones, such as isorhamnetin-sulfate-glycoside. In addition, we showed that sulfated flavonoids represent a substantial sulfur pool in Flaveria, larger than the thiols glutathione and cysteine. The individual species possess different sulfated flavonoids, but there is no correlation between the qualitative pattern and type of photosynthesis. Similar to other sulfur-containing secondary compounds, the concentration of sulfated flavonoids in leaves is reduced by sulfur starvation. The new LC-MS method will enable qualitative and quantitative detection of these secondary metabolites in plants as a pre-requisite to addressing their functions.
Collapse
Affiliation(s)
- Niklas Kleinenkuhnen
- MS-Platform, Cluster of Excellence on Plant Sciences, Botanical Institute (CEPLAS), University of Cologne, Cologne, Germany
| | - Felix Büchel
- MS-Platform, Cluster of Excellence on Plant Sciences, Botanical Institute (CEPLAS), University of Cologne, Cologne, Germany
| | - Silke C. Gerlich
- Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany
| | - Stanislav Kopriva
- Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany
| | - Sabine Metzger
- MS-Platform, Cluster of Excellence on Plant Sciences, Botanical Institute (CEPLAS), University of Cologne, Cologne, Germany
- Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany
| |
Collapse
|
6
|
Wiseschart A, Mhuantong W, Tangphatsornruang S, Chantasingh D, Pootanakit K. Shotgun metagenomic sequencing from Manao-Pee cave, Thailand, reveals insight into the microbial community structure and its metabolic potential. BMC Microbiol 2019; 19:144. [PMID: 31248378 PMCID: PMC6598295 DOI: 10.1186/s12866-019-1521-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 06/19/2019] [Indexed: 12/21/2022] Open
Abstract
Background Due to the cave oligotrophic environment, this habitat presents a challenge for microorganisms to colonize and thrive. However, it has been well documented that microorganisms play important roles in cave development. Survival of microbes in this unique habitat likely involves a broad range of adaptive capabilities. Recently, cave microbiomes all over the world are of great scientific interest. However, the majority of investigations focused mostly on small subunit ribosomal RNA (16S rRNA) gene, leaving the ecological role of the microbial community largely unknown. Here, we are particularly interested in exploring the taxonomic composition and metabolic potential of microorganisms in soil from Manao-Pee cave, a subterranean limestone cave in the western part of Thailand, by using high-throughput shotgun metagenomic sequencing. Results From taxonomic composition analysis using ribosomal RNA genes (rRNA), the results confirmed that Actinobacteria (51.2%) and Gammaproteobacteria (24.4%) were the dominant bacterial groups in the cave soil community. Metabolic potential analysis, based on six functional modules of the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, revealed that functional genes involved in microbial metabolisms are highly represented in this community (40.6%). To better understand how microbes thrive under unfavorable cave condition, we focused on microbial energy metabolism. The results showed that microbial genes involved in oxidative phosphorylation were the most dominant (28.8%) in Manao-Pee cave, and were followed by methane metabolism (20.5%), carbon fixation (16.0%), nitrogen metabolism (14.7%), and sulfur metabolism (6.3%). In addition, microbial genes involved in xenobiotic biodegradation (26 pathways) and in production of secondary metabolites (27 pathways) were also identified. Conclusion In addition to providing information on microbial diversity, we also gained insights into microbial adaptations and survival strategies under cave conditions. Based on rRNA genes, the results revealed that bacteria belonging to the Actinobacteria and Gammaproteobacteria were the most abundant in this community. From metabolic potential analysis, energy and nutrient sources that sustain diverse microbial population in this community might be atmospheric gases (methane, carbon dioxide, nitrogen), inorganic sulfur, and xenobiotic compounds. In addition, the presence of biosynthetic pathways of secondary metabolites suggested that they might play important ecological roles in the cave microbiome. Electronic supplementary material The online version of this article (10.1186/s12866-019-1521-8) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Apirak Wiseschart
- Institute of Molecular Biosciences, Mahidol University, Salaya Campus, Phuttamonthon 4 Rd, Salaya, Nakhon Pathom, 73170, Thailand
| | - Wuttichai Mhuantong
- National Center for Genetic Engineering and Biotechnology (BIOTEC), 133 Thailand Science Park, Paholyothin Rd, Klong 1, Klongluang, Pathumthani, 12120, Thailand
| | - Sithichoke Tangphatsornruang
- National Center for Genetic Engineering and Biotechnology (BIOTEC), 133 Thailand Science Park, Paholyothin Rd, Klong 1, Klongluang, Pathumthani, 12120, Thailand
| | - Duriya Chantasingh
- National Center for Genetic Engineering and Biotechnology (BIOTEC), 133 Thailand Science Park, Paholyothin Rd, Klong 1, Klongluang, Pathumthani, 12120, Thailand
| | - Kusol Pootanakit
- Institute of Molecular Biosciences, Mahidol University, Salaya Campus, Phuttamonthon 4 Rd, Salaya, Nakhon Pathom, 73170, Thailand.
| |
Collapse
|
7
|
Gerlich SC, Walker BJ, Krueger S, Kopriva S. Sulfate Metabolism in C 4 Flaveria Species Is Controlled by the Root and Connected to Serine Biosynthesis. PLANT PHYSIOLOGY 2018; 178:565-582. [PMID: 30104256 PMCID: PMC6181035 DOI: 10.1104/pp.18.00520] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 07/27/2018] [Indexed: 05/21/2023]
Abstract
The evolution of C4 photosynthesis led to an increase in carbon assimilation rates and plant growth compared to C3 photosynthetic plants. This enhanced plant growth, in turn, affects the requirement for soil-derived mineral nutrients. However, mineral plant nutrition has scarcely been considered in connection with C4 photosynthesis. Sulfur is crucial for plant growth and development, and preliminary studies in the genus Flaveria suggested metabolic differences in sulfate assimilation along the C4 evolutionary trajectory. Here, we show that in controlled conditions, foliar accumulation of the reduced sulfur compounds Cys and glutathione (GSH) increased with progressing establishment of the C4 photosynthetic cycle in different Flaveria species. An enhanced demand for reduced sulfur in C4 Flaveria species is reflected in high rates of [35S]sulfate incorporation into GSH upon sulfate deprivation and increased GSH turnover as a reaction to the inhibition of GSH synthesis. Expression analyses indicate that the γ-glutamyl cycle is crucial for the recycling of GSH in C4 species. Sulfate reduction and GSH synthesis seems to be preferentially localized in the roots of C4 species, which might be linked to its colocalization with the phosphorylated pathway of Ser biosynthesis. Interspecies grafting experiments of F. robusta (C3) and F. bidentis (C4) revealed that the root system primarily controls sulfate acquisition, GSH synthesis, and sulfate and metabolite allocation in C3 and C4 plants. This study thus shows that evolution of C4 photosynthesis resulted in a wide range of adaptations of sulfur metabolism and points out the need for broader studies on importance of mineral nutrition for C4 plants.
Collapse
Affiliation(s)
- Silke C Gerlich
- Botanical Institute, University of Cologne, 50674 Cologne, Germany
- Cluster of Excellence on Plant Sciences, University of Cologne, 50674 Cologne, Germany
| | - Berkley J Walker
- Institute of Plant Biochemistry, Cluster of Excellence on Plant Sciences, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Stephan Krueger
- Botanical Institute, University of Cologne, 50674 Cologne, Germany
| | - Stanislav Kopriva
- Botanical Institute, University of Cologne, 50674 Cologne, Germany
- Cluster of Excellence on Plant Sciences, University of Cologne, 50674 Cologne, Germany
| |
Collapse
|
8
|
Xia Z, Xu Z, Wei Y, Wang M. Overexpression of the Maize Sulfite Oxidase Increases Sulfate and GSH Levels and Enhances Drought Tolerance in Transgenic Tobacco. FRONTIERS IN PLANT SCIENCE 2018; 9:298. [PMID: 29593762 PMCID: PMC5857591 DOI: 10.3389/fpls.2018.00298] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 02/21/2018] [Indexed: 05/10/2023]
Abstract
Sulfite oxidase (SO) plays a pivotal role in sulfite metabolism. In our previous study, sulfite-oxidizing function of the SO from Zea mays (ZmSO) was characterized. To date, the knowledge of ZmSO's involvement in abiotic stress response is scarce. In this study, we aimed to investigate the role of ZmSO in drought stress. The transcript levels of ZmSO were relatively high in leaves and immature embryos of maize plants, and were up-regulated markedly by PEG-induced water stress. Overexpression of ZmSO improved drought tolerance in tobacco. ZmSO-overexpressing transgenic plants showed higher sulfate and glutathione (GSH) levels but lower hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents under drought stress, indicating that ZmSO confers drought tolerance by enhancing GSH-dependent antioxidant system that scavenged ROS and reduced membrane injury. In addition, the transgenic plants exhibited more increased stomatal response than the wild-type (WT) to water deficit. Interestingly, application of exogenous GSH effectively alleviated growth inhibition in both WT and transgenic plants under drought conditions. qPCR analysis revealed that the expression of several sulfur metabolism-related genes was significantly elevated in the ZmSO-overexpressing lines. Taken together, these results imply that ZmSO confers enhanced drought tolerance in transgenic tobacco plants possibly through affecting stomatal regulation, GSH-dependent antioxidant system, and sulfur metabolism-related gene expression. ZmSO could be exploited for developing drought-tolerant maize varieties in molecular breeding.
Collapse
Affiliation(s)
- Zongliang Xia
- College of Life Science, Henan Agricultural University, Zhengzhou, China
- Key Laboratory of Wheat and Maize Crop Science, Collaborative Innovation Center of Henan Grain Crops, Zhengzhou, China
- *Correspondence: Zongliang Xia,
| | - Ziwei Xu
- College of Life Science, Henan Agricultural University, Zhengzhou, China
| | - Yangyang Wei
- College of Life Science, Henan Agricultural University, Zhengzhou, China
| | - Meiping Wang
- Library of Henan Agricultural University, Zhengzhou, China
| |
Collapse
|
9
|
Waqas M, Kim YH, Khan AL, Shahzad R, Asaf S, Hamayun M, Kang SM, Khan MA, Lee IJ. Additive effects due to biochar and endophyte application enable soybean to enhance nutrient uptake and modulate nutritional parameters. J Zhejiang Univ Sci B 2017; 18:109-124. [PMID: 28124840 PMCID: PMC5296228 DOI: 10.1631/jzus.b1500262] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 05/02/2016] [Indexed: 11/11/2022]
Abstract
We studied the effects of hardwood-derived biochar (BC) and the phytohormone-producing endophyte Galactomyces geotrichum WLL1 in soybean (Glycine max (L.) Merr.) with respect to basic, macro- and micronutrient uptakes and assimilations, and their subsequent effects on the regulation of functional amino acids, isoflavones, fatty acid composition, total sugar contents, total phenolic contents, and 1,1-diphenyl-2-picrylhydrazyl (DPPH)-scavenging activity. The assimilation of basic nutrients such as nitrogen was up-regulated, leaving carbon, oxygen, and hydrogen unaffected in BC+G. geotrichum-treated soybean plants. In comparison, the uptakes of macro- and micronutrients fluctuated in the individual or co-application of BC and G. geotrichum in soybean plant organs and rhizospheric substrate. Moreover, the same attribute was recorded for the regulation of functional amino acids, isoflavones, fatty acid composition, total sugar contents, total phenolic contents, and DPPH-scavenging activity. Collectively, these results showed that BC+G. geotrichum-treated soybean yielded better results than did the plants treated with individual applications. It was concluded that BC is an additional nutriment source and that the G. geotrichum acts as a plant biostimulating source and the effects of both are additive towards plant growth promotion. Strategies involving the incorporation of BC and endophytic symbiosis may help achieve eco-friendly agricultural production, thus reducing the excessive use of chemical agents.
Collapse
Affiliation(s)
- Muhammad Waqas
- School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Korea
- Department of Agriculture, Abdul Wali Khan University Mardan, Mardan 23200, Pakistan
| | - Yoon-Ha Kim
- School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Korea
- Division of Plant Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Abdul Latif Khan
- School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Korea
- UoN Chair of Oman's Medicinal Plants & Marine Natural Products, University of Nizwa, Nizwa 616, Oman
| | - Raheem Shahzad
- School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Korea
| | - Sajjad Asaf
- School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Korea
| | - Muhammad Hamayun
- Department of Botany, Abdul Wali Khan University Mardan, Mardan 23200, Pakistan
| | - Sang-Mo Kang
- School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Korea
| | - Muhammad Aaqil Khan
- School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Korea
| | - In-Jung Lee
- School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Korea
| |
Collapse
|
10
|
Ahmad N, Malagoli M, Wirtz M, Hell R. Drought stress in maize causes differential acclimation responses of glutathione and sulfur metabolism in leaves and roots. BMC PLANT BIOLOGY 2016; 16:247. [PMID: 27829370 PMCID: PMC5103438 DOI: 10.1186/s12870-016-0940-z] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 10/31/2016] [Indexed: 05/08/2023]
Abstract
BACKGROUND Drought is the most important environmental stress that limits crop yield in a global warming world. Despite the compelling evidence of an important role of oxidized and reduced sulfur-containing compounds during the response of plants to drought stress (e.g. sulfate for stomata closure or glutathione for scavenging of reactive oxygen species), the assimilatory sulfate reduction pathway is almost not investigated at the molecular or at the whole plant level during drought. RESULTS In the present study, we elucidated the role of assimilatory sulfate reduction in roots and leaves of the staple crop maize after application of drought stress. The time-resolved dynamics of the adaption processes to the stress was analyzed in a physiological relevant situation -when prolonged drought caused significant oxidation stress but root growth should be maintained. The allocation of sulfate was significantly shifted to the roots upon drought and allowed for significant increase of thiols derived from sulfate assimilation in roots. This enabled roots to produce biomass, while leaf growth was stopped. Accumulation of harmful reactive oxygen species caused oxidation of the glutathione pool and decreased glutathione levels in leaves. Surprisingly, flux analysis using [35S]-sulfate demonstrated a significant down-regulation of sulfate assimilation and cysteine synthesis in leaves due to the substantial decrease of serine acetyltransferase activity. The insufficient cysteine supply caused depletion of glutathione pool in spite of significant transcriptional induction of glutathione synthesis limiting GSH1. Furthermore, drought impinges on transcription of membrane-localized sulfate transport systems in leaves and roots, which provides a potential molecular mechanism for the reallocation of sulfur upon prolonged water withdrawal. CONCLUSIONS The study demonstrated a significant and organ-specific impact of drought upon sulfate assimilation. The sulfur metabolism related alterations at the transcriptional, metabolic and enzyme activity level are consistent with a promotion of root growth to search for water at the expense of leaf growth. The results provide evidence for the importance of antagonistic regulation of sulfur metabolism in leaves and roots to enable successful drought stress response at the whole plant level.
Collapse
Affiliation(s)
- Nisar Ahmad
- Centre for Organismal Studies Heidelberg, Heidelberg University, Im Neuenheimer Feld 360, 69120, Heidelberg, Germany
- University of Science & Technology Bannu, Bannu, Pakistan
| | - Mario Malagoli
- Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padova, Padova, Italy
| | - Markus Wirtz
- Centre for Organismal Studies Heidelberg, Heidelberg University, Im Neuenheimer Feld 360, 69120, Heidelberg, Germany
| | - Ruediger Hell
- Centre for Organismal Studies Heidelberg, Heidelberg University, Im Neuenheimer Feld 360, 69120, Heidelberg, Germany.
| |
Collapse
|