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Eckardt NA, Allahverdiyeva Y, Alvarez CE, Büchel C, Burlacot A, Cardona T, Chaloner E, Engel BD, Grossman AR, Harris D, Herrmann N, Hodges M, Kern J, Kim TD, Maurino VG, Mullineaux CW, Mustila H, Nikkanen L, Schlau-Cohen G, Tronconi MA, Wietrzynski W, Yachandra VK, Yano J. Lighting the way: Compelling open questions in photosynthesis research. THE PLANT CELL 2024; 36:3914-3943. [PMID: 39038210 DOI: 10.1093/plcell/koae203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 05/29/2024] [Accepted: 07/15/2024] [Indexed: 07/24/2024]
Abstract
Photosynthesis-the conversion of energy from sunlight into chemical energy-is essential for life on Earth. Yet there is much we do not understand about photosynthetic energy conversion on a fundamental level: how it evolved and the extent of its diversity, its dynamics, and all the components and connections involved in its regulation. In this commentary, researchers working on fundamental aspects of photosynthesis including the light-dependent reactions, photorespiration, and C4 photosynthetic metabolism pose and discuss what they view as the most compelling open questions in their areas of research.
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Affiliation(s)
| | - Yagut Allahverdiyeva
- Molecular Plant Biology Unit, Department of Life Technologies, University of Turku, 20014 Turku, Finland
| | - Clarisa E Alvarez
- Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI-CONICET), Facultad de Ciencias Bioquímicas y Farmacuticas, University of Rosario, Suipacha 570, 2000 Rosario, Argentina
| | - Claudia Büchel
- Institute of Molecular Biosciences, Goethe University Frankfurt, 60438 Frankfurt, Germany
| | - Adrien Burlacot
- Division of Bioscience and Engineering, Carnegie Institution for Science, 260 Panama Street, Stanford, CA 94305, USA
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Tanai Cardona
- School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Emma Chaloner
- School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Benjamin D Engel
- Biozentrum, University of Basel, Sptialstrasse 41, 4056 Basel, Switzerland
| | - Arthur R Grossman
- Division of Bioscience and Engineering, Carnegie Institution for Science, 260 Panama Street, Stanford, CA 94305, USA
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Dvir Harris
- Department of Chemistry, Massachusetts Institute of Technology, Massachusetts Ave, Cambridge, MA 02139, USA
| | - Nicolas Herrmann
- Institute of Molecular Biosciences, Goethe University Frankfurt, 60438 Frankfurt, Germany
| | - Michael Hodges
- Université Paris-Saclay, CNRS, INRAE, Université d'Evry, Université de Paris Cité, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
| | - Jan Kern
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Tom Dongmin Kim
- School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Veronica G Maurino
- Molecular Plant Physiology, Institute for Cellular and Molecular Botany (IZMB), University of Bonn, Kirschallee 1, 53115 Bonn, Germany
| | - Conrad W Mullineaux
- School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Henna Mustila
- Molecular Plant Biology Unit, Department of Life Technologies, University of Turku, 20014 Turku, Finland
| | - Lauri Nikkanen
- Molecular Plant Biology Unit, Department of Life Technologies, University of Turku, 20014 Turku, Finland
| | - Gabriela Schlau-Cohen
- Department of Chemistry, Massachusetts Institute of Technology, Massachusetts Ave, Cambridge, MA 02139, USA
| | - Marcos A Tronconi
- Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI-CONICET), Facultad de Ciencias Bioquímicas y Farmacuticas, University of Rosario, Suipacha 570, 2000 Rosario, Argentina
| | | | - Vittal K Yachandra
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Junko Yano
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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DiMario RJ, Kophs AN, Apalla AJA, Schnable JN, Cousins AB. Multiple highly expressed phosphoenolpyruvate carboxylase genes have divergent enzyme kinetic properties in two C4 grasses. ANNALS OF BOTANY 2023; 132:413-428. [PMID: 37675505 PMCID: PMC10667006 DOI: 10.1093/aob/mcad116] [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: 04/12/2023] [Accepted: 09/06/2023] [Indexed: 09/08/2023]
Abstract
BACKGROUND AND AIMS Phosphoenolpyruvate (PEP) carboxylase (PEPC) catalyses the irreversible carboxylation of PEP with bicarbonate to produce oxaloacetate. This reaction powers the carbon-concentrating mechanism (CCM) in plants that perform C4 photosynthesis. This CCM is generally driven by a single PEPC gene product that is highly expressed in the cytosol of mesophyll cells. We found two C4 grasses, Panicum miliaceum and Echinochloa colona, that each have two highly expressed PEPC genes. We characterized the kinetic properties of the two most abundant PEPCs in E. colona and P. miliaceum to better understand how the enzyme's amino acid structure influences its function. METHODS Coding sequences of the two most abundant PEPC proteins in E. colona and P. miliaceum were synthesized by GenScript and were inserted into bacteria expression plasmids. Point mutations resulting in substitutions at conserved amino acid residues (e.g. N-terminal serine and residue 890) were created via site-directed PCR mutagenesis. The kinetic properties of semi-purified plant PEPCs from Escherichia coli were analysed using membrane-inlet mass spectrometry and a spectrophotometric enzyme-coupled reaction. KEY RESULTS The two most abundant P. miliaceum PEPCs (PmPPC1 and PmPPC2) have similar sequence identities (>95 %), and as a result had similar kinetic properties. The two most abundant E. colona PEPCs (EcPPC1 and EcPPC2) had identities of ~78 % and had significantly different kinetic properties. The PmPPCs and EcPPCs had different responses to allosteric inhibitors and activators, and substitutions at the conserved N-terminal serine and residue 890 resulted in significantly altered responses to allosteric regulators. CONCLUSIONS The two, significantly expressed C4Ppc genes in P. miliaceum were probably the result of genomes combining from two closely related C4Panicum species. We found natural variation in PEPC's sensitivity to allosteric inhibition that seems to bypass the conserved 890 residue, suggesting alternative evolutionary pathways for increased malate tolerance and other kinetic properties.
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Affiliation(s)
- Robert J DiMario
- School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
| | - Ashley N Kophs
- School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
| | - Anthony J A Apalla
- School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
| | - James N Schnable
- Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE 68583, USA
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
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3
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Yogadasan N, Doxey AC, Chuong SDX. A Machine Learning Framework Identifies Plastid-Encoded Proteins Harboring C3 and C4 Distinguishing Sequence Information. Genome Biol Evol 2023; 15:evad129. [PMID: 37462292 PMCID: PMC10368328 DOI: 10.1093/gbe/evad129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/12/2023] [Indexed: 07/27/2023] Open
Abstract
C4 photosynthesis is known to have at least 61 independent origins across plant lineages making it one of the most notable examples of convergent evolution. Of the >60 independent origins, a predicted 22-24 origins, encompassing greater than 50% of all known C4 species, exist within the Panicoideae, Arundinoideae, Chloridoideae, Micrairoideae, Aristidoideae, and Danthonioideae (PACMAD) clade of the Poaceae family. This clade is therefore primed with species ideal for the study of genomic changes associated with the acquisition of the C4 photosynthetic trait. In this study, we take advantage of the growing availability of sequenced plastid genomes and employ a machine learning (ML) approach to screen for plastid genes harboring C3 and C4 distinguishing information in PACMAD species. We demonstrate that certain plastid-encoded protein sequences possess distinguishing and informative sequence information that allows them to train accurate ML C3/C4 classification models. Our RbcL-trained model, for example, informs a C3/C4 classifier with greater than 99% accuracy. Accurate prediction of photosynthetic type from individual sequences suggests biologically relevant, and potentially differing roles of these sequence products in C3 versus C4 metabolism. With this ML framework, we have identified several key sequences and sites that are most predictive of C3/C4 status, including RbcL, subunits of the NAD(P)H dehydrogenase complex, and specific residues within, further highlighting their potential significance in the evolution and/or maintenance of C4 photosynthetic machinery. This general approach can be applied to uncover intricate associations between other similar genotype-phenotype relationships.
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Affiliation(s)
| | - Andrew C Doxey
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
| | - Simon D X Chuong
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
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Singh J, Garai S, Das S, Thakur JK, Tripathy BC. Role of C4 photosynthetic enzyme isoforms in C3 plants and their potential applications in improving agronomic traits in crops. PHOTOSYNTHESIS RESEARCH 2022; 154:233-258. [PMID: 36309625 DOI: 10.1007/s11120-022-00978-9] [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: 06/02/2022] [Accepted: 10/14/2022] [Indexed: 06/16/2023]
Abstract
As compared to C3, C4 plants have higher photosynthetic rates and better tolerance to high temperature and drought. These traits are highly beneficial in the current scenario of global warming. Interestingly, all the genes of the C4 photosynthetic pathway are present in C3 plants, although they are involved in diverse non-photosynthetic functions. Non-photosynthetic isoforms of carbonic anhydrase (CA), phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase (MDH), the decarboxylating enzymes NAD/NADP-malic enzyme (NAD/NADP-ME), and phosphoenolpyruvate carboxykinase (PEPCK), and finally pyruvate orthophosphate dikinase (PPDK) catalyze reactions that are essential for major plant metabolism pathways, such as the tricarboxylic acid (TCA) cycle, maintenance of cellular pH, uptake of nutrients and their assimilation. Consistent with this view differential expression pattern of these non-photosynthetic C3 isoforms has been observed in different tissues across the plant developmental stages, such as germination, grain filling, and leaf senescence. Also abundance of these C3 isoforms is increased considerably in response to environmental fluctuations particularly during abiotic stress. Here we review the vital roles played by C3 isoforms of C4 enzymes and the probable mechanisms by which they help plants in acclimation to adverse growth conditions. Further, their potential applications to increase the agronomic trait value of C3 crops is discussed.
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Affiliation(s)
- Jitender Singh
- National Institute of Plant Genome Research, New Delhi, 110067, India.
| | - Sampurna Garai
- International Centre for Genetic Engineering and Biotechnology, New Delhi, 110067, India
| | - Shubhashis Das
- National Institute of Plant Genome Research, New Delhi, 110067, India
| | - Jitendra Kumar Thakur
- National Institute of Plant Genome Research, New Delhi, 110067, India.
- International Centre for Genetic Engineering and Biotechnology, New Delhi, 110067, India.
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5
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Heyduk K, McAssey EV, Leebens‐Mack J. Differential timing of gene expression and recruitment in independent origins of CAM in the Agavoideae (Asparagaceae). THE NEW PHYTOLOGIST 2022; 235:2111-2126. [PMID: 35596719 PMCID: PMC9796715 DOI: 10.1111/nph.18267] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 05/09/2022] [Indexed: 06/15/2023]
Abstract
Crassulacean acid metabolism (CAM) photosynthesis has evolved repeatedly across the plant tree of life, however our understanding of the genetic convergence across independent origins remains hampered by the lack of comparative studies. Here, we explore gene expression profiles in eight species from the Agavoideae (Asparagaceae) encompassing three independent origins of CAM. Using comparative physiology and transcriptomics, we examined the variable modes of CAM in this subfamily and the changes in gene expression across time of day and between well watered and drought-stressed treatments. We further assessed gene expression and the molecular evolution of genes encoding phosphoenolpyruvate carboxylase (PPC), an enzyme required for primary carbon fixation in CAM. Most time-of-day expression profiles are largely conserved across all eight species and suggest that large perturbations to the central clock are not required for CAM evolution. By contrast, transcriptional response to drought is highly lineage specific. Yucca and Beschorneria have CAM-like expression of PPC2, a copy of PPC that has never been shown to be recruited for CAM in angiosperms. Together the physiological and transcriptomic comparison of closely related C3 and CAM species reveals similar gene expression profiles, with the notable exception of differential recruitment of carboxylase enzymes for CAM function.
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Affiliation(s)
- Karolina Heyduk
- School of Life SciencesUniversity of Hawaiʻi at MānoaHonoluluHI96822USA
- Department of Plant BiologyUniversity of GeorgiaAthensGA30602USA
- Department of Ecology and Evolutionary BiologyYale UniversityNew HavenCT06520USA
| | - Edward V. McAssey
- School of Life SciencesUniversity of Hawaiʻi at MānoaHonoluluHI96822USA
| | - Jim Leebens‐Mack
- Department of Plant BiologyUniversity of GeorgiaAthensGA30602USA
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Cao J, Cheng G, Wang L, Maimaitijiang T, Lan H. Genome-Wide Identification and Analysis of the Phosphoenolpyruvate Carboxylase Gene Family in Suaeda aralocaspica, an Annual Halophyte With Single-Cellular C 4 Anatomy. FRONTIERS IN PLANT SCIENCE 2021; 12:665279. [PMID: 34527003 PMCID: PMC8435749 DOI: 10.3389/fpls.2021.665279] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Accepted: 07/09/2021] [Indexed: 06/13/2023]
Abstract
Phosphoenolpyruvate carboxylase (PEPC) plays pivotal roles in the carbon fixation of photosynthesis and a variety of metabolic and stress pathways. Suaeda aralocaspica belongs to a single-cellular C4 species and carries out a photosynthetic pathway in an unusually elongated chlorenchyma cell, which is expected to have PEPCs with different characteristics. To identify the different isoforms of PEPC genes in S. aralocaspica and comparatively analyze their expression and regulation patterns as well as the biochemical and enzymatic properties in this study, we characterized a bacterial-type PEPC (BTPC; SaPEPC-4) in addition to the two plant-type PEPCs (PTPCs; SaPEPC-1 and SaPEPC-2) using a genome-wide identification. SaPEPC-4 presented a lower expression level in all test combinations with an unknown function; two SaPTPCs showed distinct subcellular localizations and different spatiotemporal expression patterns but positively responded to abiotic stresses. Compared to SaPEPC-2, the expression of SaPEPC-1 specifically in chlorenchyma cell tissues was much more active with the progression of development and under various stresses, particularly sensitive to light, implying the involvement of SaPEPC-1 in a C4 photosynthetic pathway. In contrast, SaPEPC-2 was more like a non-photosynthetic PEPC. The expression trends of two SaPTPCs in response to light, development, and abiotic stresses were also matched with the changes in PEPC activity in vivo (native) or in vitro (recombinant), and the biochemical properties of the two recombinant SaPTPCs were similar in response to various effectors while the catalytic efficiency, substrate affinity, and enzyme activity of SaPEPC-2 were higher than that of SaPEPC-1 in vitro. All the different properties between these two SaPTPCs might be involved in transcriptional (e.g., specific cis-elements), posttranscriptional [e.g., 5'-untranslated region (5'-UTR) secondary structure], or translational (e.g., PEPC phosphorylation/dephosphorylation) regulatory events. The comparative studies on the different isoforms of the PEPC gene family in S. aralocaspica may help to decipher their exact role in C4 photosynthesis, plant growth/development, and stress resistance.
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DiMario RJ, Kophs AN, Pathare VS, Schnable JC, Cousins AB. Kinetic variation in grass phosphoenolpyruvate carboxylases provides opportunity to enhance C 4 photosynthetic efficiency. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 105:1677-1688. [PMID: 33345397 DOI: 10.1111/tpj.15141] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 12/11/2020] [Accepted: 12/15/2020] [Indexed: 06/12/2023]
Abstract
The high rates of photosynthesis and the carbon-concentrating mechanism (CCM) in C4 plants are initiated by the enzyme phosphoenolpyruvate (PEP) carboxylase (PEPC). The flow of inorganic carbon into the CCM of C4 plants is driven by PEPC's affinity for bicarbonate (KHCO3 ), which can be rate limiting when atmospheric CO2 availability is restricted due to low stomatal conductance. We hypothesize that natural variation in KHCO3 across C4 plants is driven by specific amino acid substitutions to impact rates of C4 photosynthesis under environments such as drought that restrict stomatal conductance. To test this hypothesis, we measured KHCO3 from 20 C4 grasses to compare kinetic properties with specific amino acid substitutions. There was nearly a twofold range in KHCO3 across these C4 grasses (24.3 ± 1.5 to 46.3 ± 2.4 μm), which significantly impacts modeled rates of C4 photosynthesis. Additionally, molecular engineering of a low-HCO3- affinity PEPC identified key domains that confer variation in KHCO3 . This study advances our understanding of PEPC kinetics and builds the foundation for engineering increased-HCO3- affinity and C4 photosynthetic efficiency in important C4 crops.
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Affiliation(s)
- Robert J DiMario
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Ashley N Kophs
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Varsha S Pathare
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - James C Schnable
- Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE, 68583, USA
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
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8
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Khoshravesh R, Stata M, Adachi S, Sage TL, Sage RF. Evolutionary Convergence of C 4 Photosynthesis: A Case Study in the Nyctaginaceae. FRONTIERS IN PLANT SCIENCE 2020; 11:578739. [PMID: 33224166 PMCID: PMC7667235 DOI: 10.3389/fpls.2020.578739] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 10/06/2020] [Indexed: 05/27/2023]
Abstract
C4 photosynthesis evolved over 65 times, with around 24 origins in the eudicot order Caryophyllales. In the Caryophyllales family Nyctaginaceae, the C4 pathway is known in three genera of the tribe Nyctagineae: Allionia, Okenia and Boerhavia. Phylogenetically, Allionia and Boerhavia/Okenia are separated by three genera whose photosynthetic pathway is uncertain. To clarify the distribution of photosynthetic pathways in the Nyctaginaceae, we surveyed carbon isotope ratios of 159 species of the Nyctaginaceae, along with bundle sheath (BS) cell ultrastructure, leaf gas exchange, and C4 pathway biochemistry in five species from the two C4 clades and closely related C3 genera. All species in Allionia, Okenia and Boerhavia are C4, while no C4 species occur in any other genera of the family, including three that branch between Allionia and Boerhavia. This demonstrates that C4 photosynthesis evolved twice in Nyctaginaceae. Boerhavia species use the NADP-malic enzyme (NADP-ME) subtype of C4 photosynthesis, while Allionia species use the NAD-malic enzyme (NAD-ME) subtype. The BS cells of Allionia have many more mitochondria than the BS of Boerhavia. Bundle sheath mitochondria are closely associated with chloroplasts in Allionia which facilitates CO2 refixation following decarboxylation by mitochondrial NAD-ME. The close relationship between Allionia and Boerhavia could provide insights into why NADP-ME versus NAD-ME subtypes evolve, particularly when coupled to analysis of their respective genomes. As such, the group is an excellent system to dissect the organizational hierarchy of convergent versus divergent traits produced by C4 evolution, enabling us to understand when convergence is favored versus when divergent modifications can result in a common phenotype.
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Affiliation(s)
- Roxana Khoshravesh
- Department of Ecology and Evolutionary Biology, The University of Toronto, Toronto, ON, Canada
- Department of Biology, The University of New Mexico, Albuquerque, NM, United States
| | - Matt Stata
- Department of Ecology and Evolutionary Biology, The University of Toronto, Toronto, ON, Canada
| | - Shunsuke Adachi
- Department of Ecology and Evolutionary Biology, The University of Toronto, Toronto, ON, Canada
- Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, Fuchu, Japan
| | - Tammy L. Sage
- Department of Ecology and Evolutionary Biology, The University of Toronto, Toronto, ON, Canada
| | - Rowan F. Sage
- Department of Ecology and Evolutionary Biology, The University of Toronto, Toronto, ON, Canada
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Nomura K, Sakurai Y, Dozono M. Molecular Cloning of Novel-Type Phospho enolpyruvate Carboxylase Isoforms in Pitaya ( Hylocereus undatus). PLANTS (BASEL, SWITZERLAND) 2020; 9:plants9091241. [PMID: 32967083 PMCID: PMC7569800 DOI: 10.3390/plants9091241] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 09/17/2020] [Accepted: 09/17/2020] [Indexed: 06/11/2023]
Abstract
Phosphoenolpyruvate carboxylase (PEPC) is an important enzyme involved in the initial CO2 fixation of crassulacean acid metabolism (CAM) photosynthesis. To understand the cultivation characteristics of a CAM plant pitaya, it is necessary to clarify the characteristics of PEPC in this species. Here, we cloned three PEPC cDNAs in pitaya, HuPPC1, HuPPC2, and HuPPC3, which encode 942, 934, and 966 amino acid residues, respectively. Phylogenetic analysis indicated that these PEPC belonged to plant-type PEPC (PTPC), although HuPPC1 and HuPPC2 have no Ser-phosphorylation motif in N-terminal region, which is a crucial regulation site in PTPC and contributes to CAM periodicity. HuPPC1 and HuPPC2 phylogenetically unique to the Cactaceae family, whereas HuPPC3 was included in a CAM clade. Two isoforms were partially purified at the protein level and were assigned as HuPPC2 and HuPPC3 using MASCOT analysis. The most distinct difference in enzymatic properties between the two was sensitivity to malate and aspartate, both of which are allosteric inhibitors of PEPC. With 2 mM malate, HuPPC3 was inhibited to 10% of the initial activity, whereas HuPPC2 activity was maintained at 70%. Aspartate inhibited HuPPC3 activity by approximately 50% at 5 mM; however, such inhibition was not observed for HuPPC2 at 10 mM. These results suggest that HuPPC3 corresponds to a general CAM-related PEPC, whereas HuPPC1 and HuPPC2 are related to carbon and/or nitrogen metabolism, with a characteristic regulation mechanism similar to those of Cactaceae plants.
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Affiliation(s)
- Keiichi Nomura
- Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan;
| | - Yuho Sakurai
- Faculty of Agricultural Science, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan;
| | - Mayu Dozono
- Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan;
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10
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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.
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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; ,
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11
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Shi W, Yue L, Guo J, Wang J, Yuan X, Dong S, Guo J, Guo P. Identification and evolution of C 4 photosynthetic pathway genes in plants. BMC PLANT BIOLOGY 2020; 20:132. [PMID: 32228460 PMCID: PMC7106689 DOI: 10.1186/s12870-020-02339-x] [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: 11/21/2019] [Accepted: 03/11/2020] [Indexed: 05/03/2023]
Abstract
BACKGROUND NADP-malic enzyme (NAPD-ME), and pyruvate orthophosphate dikinase (PPDK) are important enzymes that participate in C4 photosynthesis. However, the evolutionary history and forces driving evolution of these genes in C4 plants are not completely understood. RESULTS We identified 162 NADP-ME and 35 PPDK genes in 25 species and constructed respective phylogenetic trees. We classified NADP-ME genes into four branches, A1, A2, B1 and B2, whereas PPDK was classified into two branches in which monocots were in branch I and dicots were in branch II. Analyses of selective pressure on the NAPD-ME and PPDK gene families identified four positively selected sites, including 94H and 196H in the a5 branch of NADP-ME, and 95A and 559E in the e branch of PPDK at posterior probability thresholds of 95%. The positively selected sites were located in the helix and sheet regions. Quantitative RT-PCR (qRT-PCR) analyses revealed that expression levels of 6 NADP-ME and 2 PPDK genes from foxtail millet were up-regulated after exposure to light. CONCLUSION This study revealed that positively selected sites of NADP-ME and PPDK evolution in C4 plants. It provides information on the classification and positive selection of plant NADP-ME and PPDK genes, and the results should be useful in further research on the evolutionary history of C4 plants.
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Affiliation(s)
- Weiping Shi
- College of Agronomy, Shanxi Agricultural University, Taigu, 030801, China
| | - Linqi Yue
- College of Agronomy, Shanxi Agricultural University, Taigu, 030801, China
| | - Jiahui Guo
- College of Agronomy, Shanxi Agricultural University, Taigu, 030801, China
| | - Jianming Wang
- College of Agronomy, Shanxi Agricultural University, Taigu, 030801, China
| | - Xiangyang Yuan
- College of Agronomy, Shanxi Agricultural University, Taigu, 030801, China
| | - Shuqi Dong
- College of Agronomy, Shanxi Agricultural University, Taigu, 030801, China
| | - Jie Guo
- College of Agronomy, Shanxi Agricultural University, Taigu, 030801, China.
| | - Pingyi Guo
- College of Agronomy, Shanxi Agricultural University, Taigu, 030801, China.
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13
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DiMario RJ, Cousins AB. A single serine to alanine substitution decreases bicarbonate affinity of phosphoenolpyruvate carboxylase in C4Flaveria trinervia. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:995-1004. [PMID: 30517744 PMCID: PMC6363079 DOI: 10.1093/jxb/ery403] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 11/20/2018] [Indexed: 05/12/2023]
Abstract
Phosphoenolpyruvate (PEP) carboxylase (PEPc) catalyzes the first committed step of C4 photosynthesis generating oxaloacetate from bicarbonate (HCO3-) and PEP. It is hypothesized that PEPc affinity for HCO3- has undergone selective pressure for a lower KHCO3 (Km for HCO3-) to increase the carbon flux entering the C4 cycle, particularly during conditions that limit CO2 availability. However, the decrease in KHCO3 has been hypothesized to cause an unavoidable increase in KPEP (Km for PEP). Therefore, the amino acid residue S774 in the C4 enzyme, which has been shown to increase KPEP, should lead to a decrease in KHCO3. Several studies reported the effect S774 has on KPEP; however, the influence of this amino acid substitution on KHCO3 has not been tested. To test these hypotheses, membrane-inlet mass spectrometry (MIMS) was used to measure the KHCO3 of the photosynthetic PEPc from the C4Flaveria trinervia and the non-photosynthetic PEPc from the C3F. pringlei. The cDNAs for these enzymes were overexpressed and purified from the PEPc-less PCR1 Escherichia coli strain. Our work in comparison with previous reports suggests that KHCO3 and KPEP are linked by specific amino acids, such as S774; however, these kinetic parameters respond differently to the tested allosteric regulators, malate and glucose-6-phosphate.
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Affiliation(s)
- Robert J DiMario
- School of Biological Sciences, Washington State University, Pullman, WA, USA
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA, USA
- Correspondence:
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14
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Minges A, Janßen D, Offermann S, Groth G. Efficient In Vivo Screening Method for the Identification of C 4 Photosynthesis Inhibitors Based on Cell Suspensions of the Single-Cell C 4 Plant Bienertia sinuspersici. FRONTIERS IN PLANT SCIENCE 2019; 10:1350. [PMID: 31736996 PMCID: PMC6831552 DOI: 10.3389/fpls.2019.01350] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 10/01/2019] [Indexed: 05/17/2023]
Abstract
The identification of novel herbicides is of crucial importance to modern agriculture. We developed an efficient in vivo assay based on oxygen evolution measurements using suspensions of chlorenchyma cells isolated from the single-cell C4 plant Bienertia sinuspersici to identify and characterize inhibitors of C4 photosynthesis. This novel approach fills the gap between conventional in vitro assays for inhibitors targeting C4 key enzymes and in vivo experiments on whole plants. The assay addresses inhibition of the target enzymes in a plant context thereby taking care of any reduced target inhibition due to metabolization or inadequate uptake of small molecule inhibitors across plant cell walls and membranes. Known small molecule inhibitors targeting C4 photosynthesis were used to validate the approach. To this end, we tested pyruvate phosphate dikinase inhibitor bisindolylmaleimide IV and phosphoenolpyruvate carboxylase inhibitor okanin. Both inhibitors show inhibition of plant photosynthesis at half-maximal inhibitory concentrations in the sub-mM range and confirm their potential to act as a new class of C4 selective inhibitors.
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Affiliation(s)
- Alexander Minges
- Cluster of Excellence on Plant Sciences (CEPLAS), Institute of Biochemical Plant Physiology, Heinrich Heine University, Düsseldorf, Germany
| | - Dominik Janßen
- Cluster of Excellence on Plant Sciences (CEPLAS), Institute of Biochemical Plant Physiology, Heinrich Heine University, Düsseldorf, Germany
| | | | - Georg Groth
- Cluster of Excellence on Plant Sciences (CEPLAS), Institute of Biochemical Plant Physiology, Heinrich Heine University, Düsseldorf, Germany
- *Correspondence: Georg Groth,
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González-Segura L, Mújica-Jiménez C, Juárez-Díaz JA, Güémez-Toro R, Martinez-Castilla LP, Muñoz-Clares RA. Identification of the allosteric site for neutral amino acids in the maize C 4 isozyme of phosphoenolpyruvate carboxylase: The critical role of Ser-100. J Biol Chem 2018; 293:9945-9957. [PMID: 29743237 PMCID: PMC6028945 DOI: 10.1074/jbc.ra118.002884] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 05/01/2018] [Indexed: 11/06/2022] Open
Abstract
The isozymes of photosynthetic phosphoenolpyruvate carboxylase from C4 plants (PEPC-C4) play a critical role in their atmospheric CO2 assimilation and productivity. They are allosterically activated by phosphorylated trioses or hexoses, such as d-glucose 6-phosphate, and inhibited by l-malate or l-aspartate. Additionally, PEPC-C4 isozymes from grasses are activated by glycine, serine, or alanine, but the allosteric site for these compounds remains unknown. Here, we report a new crystal structure of the isozyme from Zea mays (ZmPEPC-C4) with glycine bound at the monomer-monomer interfaces of the two dimers of the tetramer, making interactions with residues of both monomers. This binding site is close to, but different from, the one proposed to bind glucose 6-phosphate. Docking experiments indicated that d/l-serine or d/l-alanine could also bind to this site, which does not exist in the PEPC-C4 isozyme from the eudicot plant Flaveria, mainly because of a lysyl residue at the equivalent position of Ser-100 in ZmPEPC-C4 Accordingly, the ZmPEPC-C4 S100K mutant is not activated by glycine, serine, or alanine. Amino acid sequence alignments showed that PEPC-C4 isozymes from the monocot family Poaceae have either serine or glycine at this position, whereas those from Cyperaceae and eudicot families have lysine. The size and charge of the residue equivalent to Ser-100 are not only crucial for the activation of PEPC-C4 isozymes by neutral amino acids but also affect their affinity for the substrate phosphoenolpyruvate and their allosteric regulation by glucose 6-phosphate and malate, accounting for the reported kinetic differences between PEPC-C4 isozymes from monocot and eudicot plants.
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Affiliation(s)
| | | | - Javier Andrés Juárez-Díaz
- Departamento de Biología Comparada, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510 Ciudad de México, México
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16
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Goolsby EW, Moore AJ, Hancock LP, De Vos JM, Edwards EJ. Molecular evolution of key metabolic genes during transitions to C 4 and CAM photosynthesis. AMERICAN JOURNAL OF BOTANY 2018; 105:602-613. [PMID: 29660114 DOI: 10.1002/ajb2.1051] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 12/12/2017] [Indexed: 06/08/2023]
Abstract
PREMISE OF THE STUDY Next-generation sequencing facilitates rapid production of well-sampled phylogenies built from very large genetic data sets, which can then be subsequently exploited to examine the molecular evolution of the genes themselves. We present an evolutionary analysis of 83 gene families (19 containing carbon-concentrating mechanism (CCM) genes, 64 containing non-CCM genes) in the portullugo clade (Caryophyllales), a diverse lineage of mostly arid-adapted plants that contains multiple evolutionary origins of all known photosynthesis types in land plants (C3 , C4 , CAM, C4 -CAM, and various intermediates). METHODS We inferred a phylogeny of 197 individuals from 167 taxa using coalescent-based approaches and individual gene family trees using maximum likelihood. Positive selection analyses were conducted on individual gene family trees with a mixed effects model of evolution (MEME). We devised new indices to compare levels of convergence and prevalence of particular residues between CCM and non-CCM genes and between species with different photosynthetic pathways. KEY RESULTS Contrary to expectations, there were no significant differences in the levels of positive selection detected in CCM versus non-CCM genes. However, we documented a significantly higher level of convergent amino acid substitutions in CCM genes, especially in C4 taxa. CONCLUSIONS Our analyses reveal a new suite of amino acid residues putatively important for C4 and CAM function. We discuss both the advantages and challenges of using targeted enrichment sequence data for exploratory studies of molecular evolution.
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Affiliation(s)
- Eric W Goolsby
- Brown University, Department of Ecology and Evolutionary Biology, Box G-W, 80 Waterman St, Providence, Rhode Island, 02912, USA
- Yale University, Department of Ecology and Evolutionary Biology, 165 Prospect Street, New Haven, Connecticut, 06511, USA
| | - Abigail J Moore
- Brown University, Department of Ecology and Evolutionary Biology, Box G-W, 80 Waterman St, Providence, Rhode Island, 02912, USA
- University of Oklahoma, Department of Microbiology and Plant Biology and Oklahoma Biological Survey, 136 George Lynn Cross Hall, 770 Van Vleet Oval, Norman, Oklahoma, 73019, USA
| | - Lillian P Hancock
- Brown University, Department of Ecology and Evolutionary Biology, Box G-W, 80 Waterman St, Providence, Rhode Island, 02912, USA
| | - Jurriaan M De Vos
- Brown University, Department of Ecology and Evolutionary Biology, Box G-W, 80 Waterman St, Providence, Rhode Island, 02912, USA
- University of Basel, Department of Environmental Sciences-Botany, Bernoullistrasse 32, 4056, Basel, Switzerland
| | - Erika J Edwards
- Brown University, Department of Ecology and Evolutionary Biology, Box G-W, 80 Waterman St, Providence, Rhode Island, 02912, USA
- Yale University, Department of Ecology and Evolutionary Biology, 165 Prospect Street, New Haven, Connecticut, 06511, USA
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Lauterbach M, Schmidt H, Billakurthi K, Hankeln T, Westhoff P, Gowik U, Kadereit G. De novo Transcriptome Assembly and Comparison of C 3, C 3-C 4, and C 4 Species of Tribe Salsoleae (Chenopodiaceae). FRONTIERS IN PLANT SCIENCE 2017; 8:1939. [PMID: 29184562 PMCID: PMC5694442 DOI: 10.3389/fpls.2017.01939] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 10/27/2017] [Indexed: 05/29/2023]
Abstract
C4 photosynthesis is a carbon-concentrating mechanism that evolved independently more than 60 times in a wide range of angiosperm lineages. Among other alterations, the evolution of C4 from ancestral C3 photosynthesis requires changes in the expression of a vast number of genes. Differential gene expression analyses between closely related C3 and C4 species have significantly increased our understanding of C4 functioning and evolution. In Chenopodiaceae, a family that is rich in C4 origins and photosynthetic types, the anatomy, physiology and phylogeny of C4, C2, and C3 species of Salsoleae has been studied in great detail, which facilitated the choice of six samples of five representative species with different photosynthetic types for transcriptome comparisons. mRNA from assimilating organs of each species was sequenced in triplicates, and sequence reads were de novo assembled. These novel genetic resources were then analyzed to provide a better understanding of differential gene expression between C3, C2 and C4 species. All three analyzed C4 species belong to the NADP-ME type as most genes encoding core enzymes of this C4 cycle are highly expressed. The abundance of photorespiratory transcripts is decreased compared to the C3 and C2 species. Like in other C4 lineages of Caryophyllales, our results suggest that PEPC1 is the C4-specific isoform in Salsoleae. Two recently identified transporters from the PHT4 protein family may not only be related to the C4 syndrome, but also active in C2 photosynthesis in Salsoleae. In the two populations of the C2 species S. divaricata transcript abundance of several C4 genes are slightly increased, however, a C4 cycle is not detectable in the carbon isotope values. Most of the core enzymes of photorespiration are highly increased in the C2 species compared to both C3 and C4 species, confirming a successful establishment of the C2 photosynthetic pathway. Furthermore, a function of PEP-CK in C2 photosynthesis appears likely, since PEP-CK gene expression is not only increased in S. divaricata but also in C2 species of other groups.
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Affiliation(s)
- Maximilian Lauterbach
- Institute for Molecular Physiology, Johannes Gutenberg-University Mainz, Mainz, Germany
- Institute for Organismic and Molecular Evolutionary Biology, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Hanno Schmidt
- Institute for Organismic and Molecular Evolutionary Biology, Johannes Gutenberg-University Mainz, Mainz, Germany
- Senckenberg Biodiversity and Climate Research Centre (SBiK-F), Frankfurt am Main, Germany
| | - Kumari Billakurthi
- Institute for Developmental and Molecular Biology of Plants, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- Cluster of Excellence on Plant Sciences, Düsseldorf, Germany
| | - Thomas Hankeln
- Institute for Organismic and Molecular Evolutionary Biology, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Peter Westhoff
- Institute for Developmental and Molecular Biology of Plants, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- Cluster of Excellence on Plant Sciences, Düsseldorf, Germany
| | - Udo Gowik
- Institute for Developmental and Molecular Biology of Plants, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- Institute for Biology and Environmental Science (IBU), Plant Evolutionary Genetics, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Gudrun Kadereit
- Institute for Molecular Physiology, Johannes Gutenberg-University Mainz, Mainz, Germany
- Institute for Organismic and Molecular Evolutionary Biology, Johannes Gutenberg-University Mainz, Mainz, Germany
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18
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Lauterbach M, van der Merwe PDW, Keßler L, Pirie MD, Bellstedt DU, Kadereit G. Evolution of leaf anatomy in arid environments – A case study in southern African Tetraena and Roepera (Zygophyllaceae). Mol Phylogenet Evol 2016; 97:129-144. [DOI: 10.1016/j.ympev.2016.01.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Revised: 01/05/2016] [Accepted: 01/06/2016] [Indexed: 12/28/2022]
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19
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Rosnow JJ, Evans MA, Kapralov MV, Cousins AB, Edwards GE, Roalson EH. Kranz and single-cell forms of C4 plants in the subfamily Suaedoideae show kinetic C4 convergence for PEPC and Rubisco with divergent amino acid substitutions. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:7347-58. [PMID: 26417023 PMCID: PMC4765798 DOI: 10.1093/jxb/erv431] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The two carboxylation reactions performed by phosphoenolpyruvate carboxylase (PEPC) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) are vital in the fixation of inorganic carbon for C4 plants. The abundance of PEPC is substantially elevated in C4 leaves, while the location of Rubisco is restricted to one of two chloroplast types. These differences compared with C3 leaves have been shown to result in convergent enzyme optimization in some C4 species. Investigation into the kinetic properties of PEPC and Rubisco from Kranz C4, single cell C4, and C3 species in Chenopodiaceae s. s. subfamily Suaedoideae showed that these major carboxylases in C4 Suaedoideae species lack the same mutations found in other C4 systems which have been examined; but still have similar convergent kinetic properties. Positive selection analysis on the N-terminus of PEPC identified residues 364 and 368 to be under positive selection with a posterior probability >0.99 using Bayes empirical Bayes. Compared with previous analyses on other C4 species, PEPC from C4 Suaedoideae species have different convergent amino acids that result in a higher K m for PEP and malate tolerance compared with C3 species. Kinetic analysis of Rubisco showed that C4 species have a higher catalytic efficiency of Rubisco (k catc in mol CO2 mol(-1) Rubisco active sites s(-1)), despite lacking convergent substitutions in the rbcL gene. The importance of kinetic changes to the two-carboxylation reactions in C4 leaves related to amino acid selection is discussed.
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Affiliation(s)
- Josh J Rosnow
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
| | - Marc A Evans
- Department of Mathematics, Washington State University, Pullman, WA 99164-3113, USA
| | - Maxim V Kapralov
- School of Natural Sciences and Psychology, Liverpool John Moores University, Liverpool L3 3AF, UK
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
| | - Gerald E Edwards
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
| | - Eric H Roalson
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
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Cheng G, Wang L, Lan H. Cloning of PEPC-1 from a C4 halophyte Suaeda aralocaspica without Kranz anatomy and its recombinant enzymatic activity in responses to abiotic stresses. Enzyme Microb Technol 2015; 83:57-67. [PMID: 26777251 DOI: 10.1016/j.enzmictec.2015.11.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 11/17/2015] [Accepted: 11/19/2015] [Indexed: 12/26/2022]
Abstract
Phosphoenolpyruvate carboxylase (PEPC) is a key enzyme of C4 photosynthetic pathway and plays an important biochemical role in higher plants and micro organisms. To gain understanding of the role of PEPC in stress adaptation in plant, we cloned PEPC gene from Suaeda aralocaspica, a C4 species without Kranz anatomy, and performed a series of experiments with PEPC gene expressed in Escherichia coli under various abiotic stresses. Results showed that, based on the homology cloning and 5'-RACE technique, the full-length cDNA sequence of PEPC (2901 bp) from S. aralocaspica was obtained, which shares the typical conserved domains to documented PEPCs and was identified as PEPC-1 in accord to the reported partial sequence (ppc-1) in S. aralocaspica. qRT-PCR analysis revealed the expression patterns of PEPC-1 and PEPC-2 (known as ppc-2, another plant type of PEPC) in S. aralocaspica, suggesting that PEPC-1 was up-regulated during seed germination and under NaCl stress, and presented higher level in chlorenchyma than other tissues, which were significantly different with PEPC-2. Afterwards, PEPC-1 was recombinant in E. coli (pET-28a-PEPC) and expressed as an approximate 110 kDa protein. Under various abiotic stresses, the recombinant E. coli strain harboring with PEPC-1 showed significant advantage in growth at 400-800 mmol L(-1) NaCl, 10-20% PEG6000, 25 and 30 °C lower temperature, 50-200 μmol L(-1) methyl viologen, and pH 5.0 and 9.0 condition, compared to control. Further analysis of the enzymatic characteristics of the recombinant PEPC-1 suggests that it was the higher enzyme activity of PEPC-1 which might confer the stress tolerance to E. coli. We speculate that over expression of PEPC-1 is probably related to regulation of oxaloacetate (OAA) in tricarboxylic acid (TCA) cycle in E. coli, which may contribute to further understanding of the physiological function of PEPC in S. aralocaspica.
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Affiliation(s)
- Gang Cheng
- Xinjiang Key Laboratory of Biological Resources and Genetic Engineering, College of Life Science and Technology, Xinjiang University, Urumqi 830046, China.
| | - Lu Wang
- Xinjiang Key Laboratory of Biological Resources and Genetic Engineering, College of Life Science and Technology, Xinjiang University, Urumqi 830046, China.
| | - Haiyan Lan
- Xinjiang Key Laboratory of Biological Resources and Genetic Engineering, College of Life Science and Technology, Xinjiang University, Urumqi 830046, China.
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