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Benedetti M, Vecchi V, Guardini Z, Dall’Osto L, Bassi R. Expression of a Hyperthermophilic Cellobiohydrolase in Transgenic Nicotiana tabacum by Protein Storage Vacuole Targeting. PLANTS (BASEL, SWITZERLAND) 2020; 9:E1799. [PMID: 33353085 PMCID: PMC7767180 DOI: 10.3390/plants9121799] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 11/30/2020] [Accepted: 12/15/2020] [Indexed: 02/01/2023]
Abstract
Plant expression of microbial Cell Wall Degrading Enzymes (CWDEs) is a valuable strategy to produce industrial enzymes at affordable cost. Unfortunately, the constitutive expression of CWDEs may affect plant fitness to variable extents, including developmental alterations, sterility and even lethality. In order to explore novel strategies for expressing CWDEs in crops, the cellobiohydrolase CBM3GH5, from the hyperthermophilic bacterium Caldicellulosiruptor saccharolyticus, was constitutively expressed in N. tabacum by targeting the enzyme both to the apoplast and to the protein storage vacuole. The apoplast targeting failed to isolate plants expressing the recombinant enzyme despite a large number of transformants being screened. On the opposite side, the targeting of the cellobiohydrolase to the protein storage vacuole led to several transgenic lines expressing CBM3GH5, with an enzyme yield of up to 0.08 mg g DW-1 (1.67 Units g DW-1) in the mature leaf tissue. The analysis of CBM3GH5 activity revealed that the enzyme accumulated in different plant organs in a developmental-dependent manner, with the highest abundance in mature leaves and roots, followed by seeds, stems and leaf ribs. Notably, both leaves and stems from transgenic plants were characterized by an improved temperature-dependent saccharification profile.
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Affiliation(s)
- Manuel Benedetti
- Dipartimento di Medicina Clinica, Sanità Pubblica, Scienze della Vita e dell’Ambiente, Università dell’Aquila, Piazzale Salvatore Tommasi 1, 67100 L’Aquila, Italy;
| | - Valeria Vecchi
- Dipartimento di Biotecnologie, Università di Verona, Strada Le Grazie 15, 37134 Verona, Italy; (V.V.); (Z.G.); (L.D.)
| | - Zeno Guardini
- Dipartimento di Biotecnologie, Università di Verona, Strada Le Grazie 15, 37134 Verona, Italy; (V.V.); (Z.G.); (L.D.)
| | - Luca Dall’Osto
- Dipartimento di Biotecnologie, Università di Verona, Strada Le Grazie 15, 37134 Verona, Italy; (V.V.); (Z.G.); (L.D.)
| | - Roberto Bassi
- Dipartimento di Biotecnologie, Università di Verona, Strada Le Grazie 15, 37134 Verona, Italy; (V.V.); (Z.G.); (L.D.)
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2
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Padilla CS, Damaj MB, Yang ZN, Molina J, Berquist BR, White EL, Solís-Gracia N, Da Silva J, Mandadi KK. High-Level Production of Recombinant Snowdrop Lectin in Sugarcane and Energy Cane. Front Bioeng Biotechnol 2020; 8:977. [PMID: 33015000 PMCID: PMC7461980 DOI: 10.3389/fbioe.2020.00977] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 07/27/2020] [Indexed: 01/11/2023] Open
Abstract
Sugarcane and energy cane (Saccharum spp. hybrids) are ideal for plant-based production of recombinant proteins because their high resource-use efficiency, rapid growth and efficient photosynthesis enable extensive biomass production and protein accumulation at a cost-effective scale. Here, we aimed to develop these species as efficient platforms to produce recombinant Galanthus nivalis L. (snowdrop) agglutinin (GNA), a monocot-bulb mannose-specific lectin with potent antiviral, antifungal and antitumor activities. Initially, GNA levels of 0.04% and 0.3% total soluble protein (TSP) (0.3 and 3.8 mg kg–1 tissue) were recovered from the culms and leaves, respectively, of sugarcane lines expressing recombinant GNA under the control of the constitutive maize ubiquitin 1 (Ubi) promoter. Co-expression of recombinant GNA from stacked multiple promoters (pUbi and culm-regulated promoters from sugarcane dirigent5-1 and Sugarcane bacilliform virus) on separate expression vectors increased GNA yields up to 42.3-fold (1.8% TSP or 12.7 mg kg–1 tissue) and 7.7-fold (2.3% TSP or 29.3 mg kg–1 tissue) in sugarcane and energy cane lines, respectively. Moreover, inducing promoter activity in the leaves of GNA transgenic lines with stress-regulated hormones increased GNA accumulation to 2.7% TSP (37.2 mg kg–1 tissue). Purification by mannose-agarose affinity chromatography yielded a functional sugarcane recombinant GNA with binding substrate specificity similar to that of native snowdrop-bulb GNA, as shown by enzyme-linked lectin and mannose-binding inhibition assays. The size and molecular weight of recombinant GNA were identical to those of native GNA, as determined by size-exclusion chromatography and MALDI-TOF mass spectrometry. This work demonstrates the feasibility of producing recombinant GNA at high levels in Saccharum species, with the long-term goal of using it as a broad-spectrum antiviral carrier molecule for hemopurifiers and in related therapeutic applications.
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Affiliation(s)
- Carmen S Padilla
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, United States
| | - Mona B Damaj
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, United States
| | - Zhong-Nan Yang
- Institute for Plant Gene Function, Department of Biology, Shanghai Normal University, Shanghai, China
| | - Joe Molina
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, United States
| | | | - Earl L White
- MDx BioAnalytical Laboratory, Inc., College Station, TX, United States
| | - Nora Solís-Gracia
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, United States
| | - Jorge Da Silva
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, United States.,Department of Soil and Crop Sciences, Texas A&M University, College Station, TX, United States
| | - Kranthi K Mandadi
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, United States.,Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, United States
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3
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Damaj MB, Jifon JL, Woodard SL, Vargas-Bautista C, Barros GOF, Molina J, White SG, Damaj BB, Nikolov ZL, Mandadi KK. Unprecedented enhancement of recombinant protein production in sugarcane culms using a combinatorial promoter stacking system. Sci Rep 2020; 10:13713. [PMID: 32792533 PMCID: PMC7426418 DOI: 10.1038/s41598-020-70530-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 07/21/2020] [Indexed: 11/09/2022] Open
Abstract
Plants represent a safe and cost-effective platform for producing high-value proteins with pharmaceutical properties; however, the ability to accumulate these in commercially viable quantities is challenging. Ideal crops to serve as biofactories would include low-input, fast-growing, high-biomass species such as sugarcane. The objective of this study was to develop an efficient expression system to enable large-scale production of high-value recombinant proteins in sugarcane culms. Bovine lysozyme (BvLz) is a potent broad-spectrum antimicrobial enzyme used in the food, cosmetics and agricultural industries. Here, we report a novel strategy to achieve high-level expression of recombinant proteins using a combinatorial stacked promoter system. We demonstrate this by co-expressing BvLz under the control of multiple constitutive and culm-regulated promoters on separate expression vectors and combinatorial plant transformation. BvLz accumulation reached 1.4% of total soluble protein (TSP) (10.0 mg BvLz/kg culm mass) in stacked multiple promoter:BvLz lines, compared to 0.07% of TSP (0.56 mg/kg) in single promoter:BvLz lines. BvLz accumulation was further boosted to 11.5% of TSP (82.5 mg/kg) through event stacking by re-transforming the stacked promoter:BvLz lines with additional BvLz expression vectors. The protein accumulation achieved with the combinatorial promoter stacking expression system was stable in multiple vegetative propagations, demonstrating the feasibility of using sugarcane as a biofactory for producing high-value proteins and bioproducts.
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Affiliation(s)
- Mona B Damaj
- Texas A&M AgriLife Research and Extension Center, 2415 East US Highway 83, Weslaco, TX, 78596, USA.
| | - John L Jifon
- Texas A&M AgriLife Research and Extension Center, 2415 East US Highway 83, Weslaco, TX, 78596, USA
- Department of Horticultural Sciences, Texas A&M University, College Station, TX, 77843-2133, USA
| | - Susan L Woodard
- National Center for Therapeutics Manufacturing, Texas A&M University, 100 Discovery Drive, College Station, TX, 77843-4482, USA
| | - Carol Vargas-Bautista
- Texas A&M AgriLife Research and Extension Center, 2415 East US Highway 83, Weslaco, TX, 78596, USA
- College of Medicine, Texas A&M University, 8447 Riverside Parkway, Bryan, TX, 77807, USA
| | - Georgia O F Barros
- BioSeparation Laboratory, Biological and Agricultural Engineering Department, College Station, TX, 77843-2117, USA
| | - Joe Molina
- Texas A&M AgriLife Research and Extension Center, 2415 East US Highway 83, Weslaco, TX, 78596, USA
| | - Steven G White
- BioSeparation Laboratory, Biological and Agricultural Engineering Department, College Station, TX, 77843-2117, USA
| | - Bassam B Damaj
- Innovus Pharmaceuticals, Inc., 8845 Rehco Road, San Diego, CA, 92121, USA
| | - Zivko L Nikolov
- BioSeparation Laboratory, Biological and Agricultural Engineering Department, College Station, TX, 77843-2117, USA
| | - Kranthi K Mandadi
- Texas A&M AgriLife Research and Extension Center, 2415 East US Highway 83, Weslaco, TX, 78596, USA.
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, 77843-2132, USA.
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van Eerde A, Várnai A, Jameson JK, Paruch L, Moen A, Anonsen JH, Chylenski P, Steen HS, Heldal I, Bock R, Eijsink VGH, Liu‐Clarke J. In-depth characterization of Trichoderma reesei cellobiohydrolase TrCel7A produced in Nicotiana benthamiana reveals limitations of cellulase production in plants by host-specific post-translational modifications. PLANT BIOTECHNOLOGY JOURNAL 2020; 18:631-643. [PMID: 31373133 PMCID: PMC7004914 DOI: 10.1111/pbi.13227] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 07/01/2019] [Accepted: 07/26/2019] [Indexed: 05/17/2023]
Abstract
Sustainable production of biofuels from lignocellulose feedstocks depends on cheap enzymes for degradation of such biomass. Plants offer a safe and cost-effective production platform for biopharmaceuticals, vaccines and industrial enzymes boosting biomass conversion to biofuels. Production of intact and functional protein is a prerequisite for large-scale protein production, and extensive host-specific post-translational modifications (PTMs) often affect the catalytic properties and stability of recombinant enzymes. Here we investigated the impact of plant PTMs on enzyme performance and stability of the major cellobiohydrolase TrCel7A from Trichoderma reesei, an industrially relevant enzyme. TrCel7A was produced in Nicotiana benthamiana using a vacuum-based transient expression technology, and this recombinant enzyme (TrCel7Arec ) was compared with the native fungal enzyme (TrCel7Anat ) in terms of PTMs and catalytic activity on commercial and industrial substrates. We show that the N-terminal glutamate of TrCel7Arec was correctly processed by N. benthamiana to a pyroglutamate, critical for protein structure, while the linker region of TrCel7Arec was vulnerable to proteolytic digestion during protein production due to the absence of O-mannosylation in the plant host as compared with the native protein. In general, the purified full-length TrCel7Arec had 25% lower catalytic activity than TrCel7Anat and impaired substrate-binding properties, which can be attributed to larger N-glycans and lack of O-glycans in TrCel7Arec . All in all, our study reveals that the glycosylation machinery of N. benthamiana needs tailoring to optimize the production of efficient cellulases.
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Affiliation(s)
| | - Anikó Várnai
- Faculty of Chemistry, Biotechnology and Food ScienceNorwegian University of Life Sciences (NMBU)ÅsNorway
| | - John Kristian Jameson
- Faculty of Chemistry, Biotechnology and Food ScienceNorwegian University of Life Sciences (NMBU)ÅsNorway
| | - Lisa Paruch
- NIBIONorwegian Institute of Bioeconomy ResearchÅsNorway
| | - Anders Moen
- Department of BiosciencesFaculty of Mathematics and Natural SciencesUniversity of Oslo (UiO)OsloNorway
| | - Jan Haug Anonsen
- Department of BiosciencesFaculty of Mathematics and Natural SciencesUniversity of Oslo (UiO)OsloNorway
| | - Piotr Chylenski
- Faculty of Chemistry, Biotechnology and Food ScienceNorwegian University of Life Sciences (NMBU)ÅsNorway
| | | | - Inger Heldal
- NIBIONorwegian Institute of Bioeconomy ResearchÅsNorway
| | - Ralph Bock
- Max Planck Institute of Molecular Plant PhysiologyPotsdam‐GolmGermany
| | - Vincent G. H. Eijsink
- Faculty of Chemistry, Biotechnology and Food ScienceNorwegian University of Life Sciences (NMBU)ÅsNorway
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Ozbayram EG, Kleinsteuber S, Nikolausz M. Biotechnological utilization of animal gut microbiota for valorization of lignocellulosic biomass. Appl Microbiol Biotechnol 2019; 104:489-508. [DOI: 10.1007/s00253-019-10239-w] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 10/25/2019] [Accepted: 11/04/2019] [Indexed: 10/25/2022]
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6
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Green Production and Biotechnological Applications of Cell Wall Lytic Enzymes. APPLIED SCIENCES-BASEL 2019. [DOI: 10.3390/app9235012] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
: Energy demand is constantly growing, and, nowadays, fossil fuels still play a dominant role in global energy production, despite their negative effects on air pollution and the emission of greenhouse gases, which are the main contributors to global warming. An alternative clean source of energy is represented by the lignocellulose fraction of plant cell walls, the most abundant carbon source on Earth. To obtain biofuels, lignocellulose must be efficiently converted into fermentable sugars. In this regard, the exploitation of cell wall lytic enzymes (CWLEs) produced by lignocellulolytic fungi and bacteria may be considered as an eco-friendly alternative. These organisms evolved to produce a variety of highly specific CWLEs, even if in low amounts. For an industrial use, both the identification of novel CWLEs and the optimization of sustainable CWLE-expressing biofactories are crucial. In this review, we focus on recently reported advances in the heterologous expression of CWLEs from microbial and plant expression systems as well as some of their industrial applications, including the production of biofuels from agricultural feedstock and of value-added compounds from waste materials. Moreover, since heterologous expression of CWLEs may be toxic to plant hosts, genetic strategies aimed in converting such a deleterious effect into a beneficial trait are discussed.
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7
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Kumari U, Singh R, Ray T, Rana S, Saha P, Malhotra K, Daniell H. Validation of leaf enzymes in the detergent and textile industries: launching of a new platform technology. PLANT BIOTECHNOLOGY JOURNAL 2019; 17:1167-1182. [PMID: 30963679 PMCID: PMC6523609 DOI: 10.1111/pbi.13122] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 03/21/2019] [Accepted: 03/27/2019] [Indexed: 05/02/2023]
Abstract
Chemical catalysts are being replaced by biocatalysts in almost all industrial applications due to environmental concerns, thereby increasing their demand. Enzymes used in current industries are produced in microbial systems or plant seeds. We report here five newly launched leaf-enzyme products and their validation with 15 commercial microbial-enzyme products, for detergent or textile industries. Enzymes expressed in chloroplasts are functional at broad pH/temperature ranges as crude-leaf extracts, while most purified commercial enzymes showed significant loss at alkaline pH or higher temperature, required for broad range commercial applications. In contrast to commercial liquid enzymes requiring cold storage/transportation, chloroplast enzymes as a leaf powder can be stored up to 16 months at ambient temperature without loss of enzyme activity. Chloroplast-derived enzymes are stable in crude-leaf extracts without addition of protease inhibitors. Leaf lipase/mannanase crude extracts removed chocolate or mustard oil stains effectively at both low and high temperatures. Moreover, leaf lipase or mannanase crude-extracts removed stain more efficiently at 70 °C than commercial microbial enzymes (<10% activity). Endoglucanase and exoglucanase in crude leaf extracts removed dye efficiently from denim surface and depilled knitted fabric by removal of horizontal fibre strands. Due to an increased demand for enzymes in the food industry, marker-free lettuce plants expressing lipase or cellobiohydrolase were created for the first time and site-specific transgene integration/homoplasmy was confirmed by Southern blots. Thus, leaf-production platform offers a novel low-cost approach by the elimination of fermentation, purification, concentration, formulation and cold-chain storage/transportation. This is the first report of commercially launched protein products made in leaves and validated with current commercial products.
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Affiliation(s)
- Uma Kumari
- Department of BiochemistrySchool of Dental MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Rahul Singh
- Department of BiochemistrySchool of Dental MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Tui Ray
- Department of BiochemistrySchool of Dental MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Seema Rana
- Department of BiochemistrySchool of Dental MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Prasenjit Saha
- Department of BiochemistrySchool of Dental MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Karan Malhotra
- Department of BiochemistrySchool of Dental MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Henry Daniell
- Department of BiochemistrySchool of Dental MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
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8
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Jutras PV, Goulet M, Lavoie P, D'Aoust M, Sainsbury F, Michaud D. Recombinant protein susceptibility to proteolysis in the plant cell secretory pathway is pH-dependent. PLANT BIOTECHNOLOGY JOURNAL 2018; 16:1928-1938. [PMID: 29618167 PMCID: PMC6181212 DOI: 10.1111/pbi.12928] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 03/14/2018] [Accepted: 03/21/2018] [Indexed: 05/07/2023]
Abstract
Cellular engineering approaches have been proposed to mitigate unintended proteolysis in plant protein biofactories, involving the design of protease activity-depleted environments by gene silencing or in situ inactivation with accessory protease inhibitors. Here, we assessed the impact of influenza virus M2 proton channel on host protease activities and recombinant protein processing in the cell secretory pathway of Nicotiana benthamiana leaves. Transient co-expression assays with M2 and GFP variant pHluorin were first conducted to illustrate the potential of proton export from the Golgi lumen to promote recombinant protein yield. A fusion protein-based system involving protease-sensitive peptide linkers to attach inactive variants of tomato cystatin SlCYS8 was then designed to relate the effects of M2 on protein levels with altered protease activities in situ. Secreted versions of the cystatin fusions transiently expressed in leaf tissue showed variable 'fusion to free cystatin' cleavage ratios, in line with the occurrence of protease forms differentially active against the peptide linkers in the secretory pathway. Variable ratios were also observed for the fusions co-expressed with M2, but the extent of fusion cleavage was changed for several fusions, positively or negatively, as a result of pH increase in the Golgi. These data indicating a remodelling of endogenous protease activities upon M2 expression confirm that the stability of recombinant proteins in the plant cell secretory pathway is pH-dependent. They suggest, in practice, the potential of M2 proton channel to modulate the stability of protease-susceptible secreted proteins in planta via a pH-related, indirect effect on host resident proteases.
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Affiliation(s)
- Philippe V. Jutras
- Centre de recherche et d'innovation sur les végétauxUniversité LavalQuebec CityQCCanada
| | - Marie‐Claire Goulet
- Centre de recherche et d'innovation sur les végétauxUniversité LavalQuebec CityQCCanada
| | | | | | - Frank Sainsbury
- Australian Institute for Bioengineering and NanotechnologyThe University of QueenslandSt LuciaQldAustralia
| | - Dominique Michaud
- Centre de recherche et d'innovation sur les végétauxUniversité LavalQuebec CityQCCanada
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9
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Cheavegatti-Gianotto A, Gentile A, Oldemburgo DA, Merheb GDA, Sereno ML, Lirette RP, Ferreira THS, de Oliveira WS. Lack of Detection of Bt Sugarcane Cry1Ab and NptII DNA and Proteins in Sugarcane Processing Products Including Raw Sugar. Front Bioeng Biotechnol 2018; 6:24. [PMID: 29637070 PMCID: PMC5880997 DOI: 10.3389/fbioe.2018.00024] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 02/28/2018] [Indexed: 11/26/2022] Open
Abstract
Brazil is the largest sugarcane producer and the main sugar exporter in the world. The industrial processes applied by Brazilian mills are very efficient in producing highly purified sugar and ethanol. Literature presents evidence of lack of DNA/protein in these products, regardless of the nature of sugarcane used as raw material. Recently CTNBio, the Brazilian biosafety authority, has approved the first biotechnology-derived sugarcane variety for cultivation, event CTC175-A, which expresses the Cry1Ab protein to control the sugarcane borer (Diatraea saccharalis). The event also expresses neomycin-phosphotransferase type II (NptII) protein used as selectable marker during the transformation process. Because of the high purity of sugar and ethanol produced from genetically modified sugarcane, these end-products should potentially be classified as “pure substances, chemically defined,” by Brazilian Biosafety Law No. 11.105. If this classification is to be adopted, these substances are not considered as “GMO derivatives” and fall out of the scope of Law No. 11.105. In order to assess sugar composition and quality, we evaluate Cry1Ab and NptII expression in several sugarcane tissues and in several fractions from laboratory-scale processing of event CTC175-A for the presence of these heterologous proteins as well as for the presence of traces of recombinant DNA. The results of these studies show that CTC175-A presents high expression of Cry1Ab in leaves and barely detectable expression of heterologous proteins in stalks. We also evaluated the presence of ribulose-1,5-bisphosphate carboxylase/oxygenase protein and DNA in the fractions of the industrial processing of conventional Brazilian sugarcane cultivars. Results from both laboratory and industrial processing were concordant, demonstrating that DNA and protein are not detected in the clarified juice and downstream processed fractions, including ethanol and raw sugar, indicating that protein and DNA are removed and/or degraded during processing. In conclusion, the processing of conventional sugarcane and CTC175-A Bt event results in downstream products with no detectable concentrations of heterologous DNA or new protein. These results help in the classification of sugar and ethanol derived from CTC175-A event as pure, chemically defined substances in Brazil and may relieve regulatory burdens in countries that import Brazilian sugar.
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Affiliation(s)
| | - Agustina Gentile
- Biotechnology Department, Centro de Tecnologia Canavieira (CTC), Piracicaba, Brazil
| | | | | | - Maria Lorena Sereno
- Regulatory Department, Centro de Tecnologia Canavieira (CTC), Piracicaba, Brazil
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Dugdale B, Kato M, Deo P, Plan M, Harrison M, Lloyd R, Walsh T, Harding R, Dale J. Production of human vitronectin in Nicotiana benthamiana using the INPACT hyperexpression platform. PLANT BIOTECHNOLOGY JOURNAL 2018; 16:394-403. [PMID: 28640945 PMCID: PMC5787849 DOI: 10.1111/pbi.12779] [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: 04/04/2017] [Revised: 06/13/2017] [Accepted: 06/16/2017] [Indexed: 05/29/2023]
Abstract
Human vitronectin (hVN) is a glycoprotein that functions as a cell adhesion molecule and a regulator of coagulation in blood plasma and the extracellular matrix. In vitro, hVN is added to serum-free media in order to promote the adhesion of animal cells to tissue culture surfaces and the proliferation of undifferentiated stem cells. Here, we report the production of hVN in Nicotiana benthamiana using the inducible In Plant ACTivation (INPACT) hyperexpression platform. N. benthamiana plants were transformed with an INPACT expression cassette encoding hVN, and both the Tobacco yellow dwarf virus Rep/RepA activator and Tomato bushy stunt virus p19 gene under the transcriptional control of the ethanol-inducible AlcR:alcA gene switch. hVN expression was maximal 4-5 days postactivation of the INPACT platform with a dilute ethanol solution, and crude yields of the recombinant protein reached a maximum of 643 ± 78 mg/kg fresh weight. A three-stage purification protocol was developed using heparin and polyhistidine tag affinity binding and size exclusion filtration, resulting in a plant-made hVN product of >90% purity. Storage conditions for plant-made hVN were identified that maximized the capacity of the recombinant protein to promote cell adhesion. Critically, plant-made hVN was shown to be functionally equivalent to commercial, plasma-derived hVN at promoting one-half maximal attachment of murine fibroblast cells (BALB-C/3T3) in serum-free medium at <0.1 μg/cm2 to tissue culture plasticware. The INPACT platform represents an attractive means of producing large quantities of functional, animal-free hVN for in vitro applications.
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Affiliation(s)
- Benjamin Dugdale
- Centre for Tropical Crops and BiocommoditiesQueensland University of Technology (QUT)BrisbaneQLDAustralia
| | - Maiko Kato
- Centre for Tropical Crops and BiocommoditiesQueensland University of Technology (QUT)BrisbaneQLDAustralia
| | - Pradeep Deo
- Centre for Tropical Crops and BiocommoditiesQueensland University of Technology (QUT)BrisbaneQLDAustralia
| | - Manuel Plan
- Centre for Tropical Crops and BiocommoditiesQueensland University of Technology (QUT)BrisbaneQLDAustralia
- Present address:
Metabolomics Australia (UQ Node)Australian Institute for Bioengineering and NanotechnologyThe University of QueenslandSt LuciaQLD4072Australia
| | - Mark Harrison
- Centre for Tropical Crops and BiocommoditiesQueensland University of Technology (QUT)BrisbaneQLDAustralia
| | - Robyn Lloyd
- Centre for Tropical Crops and BiocommoditiesQueensland University of Technology (QUT)BrisbaneQLDAustralia
| | - Terry Walsh
- Centre for Tropical Crops and BiocommoditiesQueensland University of Technology (QUT)BrisbaneQLDAustralia
| | - Robert Harding
- Centre for Tropical Crops and BiocommoditiesQueensland University of Technology (QUT)BrisbaneQLDAustralia
| | - James Dale
- Centre for Tropical Crops and BiocommoditiesQueensland University of Technology (QUT)BrisbaneQLDAustralia
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11
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Song EG, Ryu KH. A pepper mottle virus-based vector enables systemic expression of endoglucanase D in non-transgenic plants. Arch Virol 2017; 162:3717-3726. [PMID: 28864903 DOI: 10.1007/s00705-017-3539-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 08/02/2017] [Indexed: 12/16/2022]
Abstract
Plant-virus-based expression vectors have been used as an alternative to the creation of transgenic plants. Using a virus-based vector, we investigated the feasibility of producing the endoglucanase D (EngD) from Clostridium cellulovorans in Nicotiana benthamiana. This protein has endoglucanase, xylanase, and exoglucanase activities and may be of value for cellulose digestion in the generation of biofuels from plant biomass. The EngD gene was cloned between the nuclear inclusion b (NIb)- and coat protein (CP)-encoding sequences of pSP6PepMoV-Vb1. In vitro transcripts derived from the clone (pSP6PepMoV-Vb1/EngD) were infectious in N. benthamiana but caused milder symptoms than wild-type PepMoV-Vb1. RT-PCR amplification of total RNA from non-inoculated upper leaves infected with PepMoV-Vb1/EngD produced the target band for the CP, partial NIb and EngD-CP regions of PepMoV-V1/EngD, in addition to nonspecific bands. Western blot analysis showed the CP target bands of PepMoV-Vb1/EngD as well as non-target bands. EngD enzymatic activity in infected plants was detected using a glucose assay. The plant leaves showed increased senescence compared with healthy and PepMoV-Vb1-infected plants. Our study suggests the feasibility of using a viral vector for systemic infection of plants for expression of heterologous engD for the purpose of digesting a cellulose substrate in plant cells for biomass production.
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Affiliation(s)
- Eun Gyeong Song
- Plant Virus GenBank, Department of Horticulture, Biotechnology and Landscape Architecture, Seoul Women's University, Seoul, Republic of Korea
| | - Ki Hyun Ryu
- Plant Virus GenBank, Department of Horticulture, Biotechnology and Landscape Architecture, Seoul Women's University, Seoul, Republic of Korea.
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Yadav SK. Technological advances and applications of hydrolytic enzymes for valorization of lignocellulosic biomass. BIORESOURCE TECHNOLOGY 2017; 245:1727-1739. [PMID: 28552567 DOI: 10.1016/j.biortech.2017.05.066] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 05/10/2017] [Accepted: 05/11/2017] [Indexed: 06/07/2023]
Abstract
Hydrolytic enzymes are indispensable tools in the production of various foodstuffs, drugs, and consumables owing to their applications in almost every industrial process nowadays. One of the foremost areas of interest involving the use of hydrolytic enzymes is in the transformation of lignocellulosic biomass into value added products. However, limitations of the processes due to inadequate enzyme activity and stability with a narrow range of pH and temperature optima often limit their effective usage. The innovative technologies, involving manipulation of enzyme activity and stability through mutagenesis, genetic engineering and metagenomics lead to a major leap in all the fields using hydrolytic enzymes. This article provides recent advancement towards the isolation and use of microbes for lignocellulosic biomass utilisation, microbes producing the hydrolytic enzymes, the modern age technologies used to manipulate and enhance the hydrolytic enzyme activity and the applications of such enzymes in value added products development from lignocellulosic biomass.
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Affiliation(s)
- Sudesh Kumar Yadav
- Center of Innovative and Applied Bioprocessing (CIAB), Knowledge City, Sector-81, Mohali, India.
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13
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Mir BA, Myburg AA, Mizrachi E, Cowan DA. In planta expression of hyperthermophilic enzymes as a strategy for accelerated lignocellulosic digestion. Sci Rep 2017; 7:11462. [PMID: 28904370 PMCID: PMC5597601 DOI: 10.1038/s41598-017-11026-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 06/14/2017] [Indexed: 11/24/2022] Open
Abstract
Conversion of lignocellulosic biomass to biofuels and biomaterials suffers from high production costs associated with biomass pretreatment and enzymatic hydrolysis. In-planta expression of lignocellulose-digesting enzymes is a promising approach to reduce these cost elements. However, this approach faces a number of challenges, including auto-hydrolysis of developing cell walls, plant growth and yield penalties, low expression levels and the limited stability of expressed enzymes at the high temperatures generally used for biomass processing to release fermentable sugars. To overcome these challenges we expressed codon-optimized recombinant hyperthermophilic endoglucanase (EG) and xylanase (Xyn) genes in A. thaliana. Transgenic Arabidopsis lines expressing EG and Xyn enzymes at high levels without any obvious plant growth or yield penalties were selected for further analysis. The highest enzyme activities were observed in the dry stems of transgenic lines, indicating that the enzymes were not degraded during stem senescence and storage. Biomass from transgenic lines exhibited improved saccharification efficiency relative to WT control plants. We conclude that the expression of hyperthermophilic enzymes in plants is a promising approach for combining pretreatment and enzymatic hydrolysis processes in lignocellulosic digestion. This study provides a valid foundation for further studies involving in planta co-expression of core and accessory lignocellulose-digesting enzymes.
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Affiliation(s)
- Bilal Ahmad Mir
- Centre for Microbial Ecology and Genomics, Department of Genetics, University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa.,Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa.,Department of Botany, School of Life Sciences, Satellite Campus Kargil, University of Kashmir, Jammu & Kashmir, India
| | - Alexander A Myburg
- Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa
| | - Eshchar Mizrachi
- Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa
| | - Don A Cowan
- Centre for Microbial Ecology and Genomics, Department of Genetics, University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa.
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14
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Bhatia R, Gallagher JA, Gomez LD, Bosch M. Genetic engineering of grass cell wall polysaccharides for biorefining. PLANT BIOTECHNOLOGY JOURNAL 2017; 15:1071-1092. [PMID: 28557198 PMCID: PMC5552484 DOI: 10.1111/pbi.12764] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 05/17/2017] [Accepted: 05/24/2017] [Indexed: 05/10/2023]
Abstract
Grasses represent an abundant and widespread source of lignocellulosic biomass, which has yet to fulfil its potential as a feedstock for biorefining into renewable and sustainable biofuels and commodity chemicals. The inherent recalcitrance of lignocellulosic materials to deconstruction is the most crucial limitation for the commercial viability and economic feasibility of biomass biorefining. Over the last decade, the targeted genetic engineering of grasses has become more proficient, enabling rational approaches to modify lignocellulose with the aim of making it more amenable to bioconversion. In this review, we provide an overview of transgenic strategies and targets to tailor grass cell wall polysaccharides for biorefining applications. The bioengineering efforts and opportunities summarized here rely primarily on (A) reprogramming gene regulatory networks responsible for the biosynthesis of lignocellulose, (B) remodelling the chemical structure and substitution patterns of cell wall polysaccharides and (C) expressing lignocellulose degrading and/or modifying enzymes in planta. It is anticipated that outputs from the rational engineering of grass cell wall polysaccharides by such strategies could help in realizing an economically sustainable, grass-derived lignocellulose processing industry.
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Affiliation(s)
- Rakesh Bhatia
- Institute of Biological, Environmental and Rural Sciences (IBERS)Aberystwyth UniversityAberystwythUK
| | - Joe A. Gallagher
- Institute of Biological, Environmental and Rural Sciences (IBERS)Aberystwyth UniversityAberystwythUK
| | | | - Maurice Bosch
- Institute of Biological, Environmental and Rural Sciences (IBERS)Aberystwyth UniversityAberystwythUK
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15
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Gao SJ, Damaj MB, Park JW, Wu XB, Sun SR, Chen RK, Mirkov TE. A novel Sugarcane bacilliform virus promoter confers gene expression preferentially in the vascular bundle and storage parenchyma of the sugarcane culm. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:172. [PMID: 28680479 PMCID: PMC5496340 DOI: 10.1186/s13068-017-0850-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 06/16/2017] [Indexed: 06/07/2023]
Abstract
BACKGROUND Saccharum species such as sugarcane and energy cane are key players in the expanding bioeconomy for sugars, bioenergy, and production of high-value proteins. Genomic tools such as culm-regulated promoters would be of great value in terms of improving biomass characteristics through enhanced carbon metabolism for sugar accumulation and/or fiber content for biofuel feedstock. Unlike the situation in dicots, monocot promoters currently used are limited and mostly derived from highly expressed constitutive plant genes and viruses. In this study, a novel promoter region of Sugarcane bacilliform virus (SCBV; genus Badnavirus, family Caulimoviridae), SCBV21 was cloned and mapped by deletion analysis and functionally characterized transiently in monocot and dicot species and stably in sugarcane. RESULTS In silico analysis of SCBV21 [1816 base pair (bp)] identified two putative promoter regions (PPR1 and PPR2) with transcription start sites (TSS1 and TSS2) and two TATA-boxes (TATAAAT and ATATAA), and several vascular-specific and regulatory elements. Deletion analysis revealed that the 710 bp region spanning PPR2 (with TSS2 and ATATAA) at the 3' end of SCBV21 retained the full promoter activity in both dicots and monocots, as shown by transient expression of the enhanced yellow fluorescent protein (EYFP) gene. In sugarcane young leaf segments, SCBV21 directed a 1.8- and 2.4-fold higher transient EYFP expression than the common maize ubiquitin 1 (Ubi1) and Cauliflower mosaic virus 35S promoters, respectively. In transgenic sugarcane, SCBV21 conferred a preferential expression of the β-glucuronidase (GUS) gene in leaves and culms and specifically in the culm storage parenchyma surrounding the vascular bundle and in vascular phloem cells. Among the transgenic events and tissues characterized in this study, the SCBV21 promoter frequently produced higher GUS activity than the Ubi1 or 35S promoters in a manner that was not obviously correlated with the transgene copy number. CONCLUSIONS The newly developed plant viral SCBV21 promoter is distinct from the few existing SCBV promoters in its sequence and expression pattern. The potential of SCBV21 as a tissue-regulated promoter with a strong activity in the culm vascular bundle and its storage parenchyma makes it useful in sugarcane engineering for improved carbon metabolism, increased bioenergy production, and enhanced stress tolerance.
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Affiliation(s)
- San-Ji Gao
- National Engineering Research Center for Sugarcane, Fujian Agriculture and Forestry University, Fuzhou, 350002 Fujian China
| | | | | | - Xiao-Bin Wu
- Guangdong Key Lab of Sugarcane Improvement & Biorefinery, Guangzhou Sugarcane Industry Research Institute, Guangzhou, 510316 Guangdong China
| | - Sheng-Ren Sun
- National Engineering Research Center for Sugarcane, Fujian Agriculture and Forestry University, Fuzhou, 350002 Fujian China
| | - Ru-Kai Chen
- National Engineering Research Center for Sugarcane, Fujian Agriculture and Forestry University, Fuzhou, 350002 Fujian China
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16
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Marin Viegas VS, Ocampo CG, Petruccelli S. Vacuolar deposition of recombinant proteins in plant vegetative organs as a strategy to increase yields. Bioengineered 2017; 8:203-211. [PMID: 27644793 PMCID: PMC5470515 DOI: 10.1080/21655979.2016.1222994] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 07/30/2016] [Accepted: 08/07/2016] [Indexed: 02/08/2023] Open
Abstract
Delivery of recombinant proteins to vegetative tissue vacuoles was considered inconvenient since this compartment was expected to be hydrolytic; nevertheless there is growing evidence that certain foreign proteins accumulate at high yields in vacuoles. For example avidin, cellulolytic enzymes, endolysin, and transglutaminases were produced at high yields when were sorted to leaf central vacuole avoiding the detrimental effect of these proteins on plant growth. Also, several secretory mammalian proteins such as collagen, α1-proteinase inhibitor, complement-5a, interleukin-6 and immunoglobulins accumulated at higher yields in leaf vacuoles than in the apoplast or cytosol. To reach this final destination, fusions to sequence specific vacuolar sorting signals (ssVSS) typical of proteases or proteinase inhibitors and/or Ct-VSS representative of storage proteins or plant lectins were used and both types of motifs were capable to increase accumulation. Importantly, the type of VSSs or position, either the N or C-terminus, did not alter protein stability, levels or pos-translational modifications. Vacuolar sorted glycoproteins had different type of oligosaccharides indicating that foreign proteins reached the vacuole by 2 different pathways: direct transport from the ER, bypassing the Golgi (high mannose oligosaccharides decorated proteins) or trafficking through the Golgi (Complex oligosaccharide containing proteins). In addition, some glycoproteins lacked of paucimannosidic oligosaccharides suggesting that vacuolar trimming of glycans did not occur. Enhanced accumulation of foreign proteins fused to VSS occurred in several plant species such as tobacco, Nicotiana benthamiana, sugarcane, tomato and in carrot and the obtained results were influenced by plant physiological state. Ten different foreign proteins fused to vacuolar sorting accumulated at higher levels than their apoplastic or cytosolic counterparts. For proteins with cytotoxic effects vacuolar sorted forms yields were superior than ER retained variants, but for other proteins the results were the opposite an there were also examples of similar levels for ER and vacuolar variants. In conclusion vacuolar sorting in vegetative tissues is a satisfactory strategy to enhance protein yields that can be used in several plant species.
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Affiliation(s)
- Vanesa Soledad Marin Viegas
- Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CIDCA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Carolina Gabriela Ocampo
- Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CIDCA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Silvana Petruccelli
- Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CIDCA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
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17
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Kim JY, Nong G, Rice JD, Gallo M, Preston JF, Altpeter F. In planta production and characterization of a hyperthermostable GH10 xylanase in transgenic sugarcane. PLANT MOLECULAR BIOLOGY 2017; 93:465-478. [PMID: 28005227 DOI: 10.1007/s11103-016-0573-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 12/04/2016] [Indexed: 06/06/2023]
Abstract
Sugarcane (Saccharum sp. hybrids) is one of the most efficient and sustainable feedstocks for commercial production of fuel ethanol. Recent efforts focus on the integration of first and second generation bioethanol conversion technologies for sugarcane to increase biofuel yields. This integrated process will utilize both the cell wall bound sugars of the abundant lignocellulosic sugarcane residues in addition to the sucrose from stem internodes. Enzymatic hydrolysis of lignocellulosic biomass into its component sugars requires significant amounts of cell wall degrading enzymes. In planta production of xylanases has the potential to reduce costs associated with enzymatic hydrolysis but has been reported to compromise plant growth and development. To address this problem, we expressed a hyperthermostable GH10 xylanase, xyl10B in transgenic sugarcane which displays optimal catalytic activity at 105 °C and only residual catalytic activity at temperatures below 70 °C. Transgene integration and expression in sugarcane were confirmed by Southern blot, RT-PCR, ELISA and western blot following biolistic co-transfer of minimal expression cassettes of xyl10B and the selectable neomycin phosphotransferase II. Xylanase activity was detected in 17 transgenic lines with a fluorogenic xylanase activity assay. Up to 1.2% of the total soluble protein fraction of vegetative progenies with integration of chloroplast targeted expression represented the recombinant Xyl10B protein. Xyl10B activity was stable in vegetative progenies. Tissues retained 75% of the xylanase activity after drying of leaves at 35 °C and a 2 month storage period. Transgenic sugarcane plants producing Xyl10B did not differ from non-transgenic sugarcane in growth and development under greenhouse conditions. Sugarcane xylan and bagasse were used as substrate for enzymatic hydrolysis with the in planta produced Xyl10B. TLC and HPLC analysis of hydrolysis products confirmed the superior catalytic activity and stability of the in planta produced Xyl10B with xylobiose as a prominent degradation product. These findings will contribute to advancing consolidated processing of lignocellulosic sugarcane biomass.
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Affiliation(s)
- Jae Yoon Kim
- Plant Molecular and Cellular Biology Program, Agronomy Department, Genetics Institute, University of Florida - IFAS, Gainesville, FL, USA
- Division of Biotechnology, Korea University, Seongbuk-Gu, Seoul, 02841, Republic of Korea
| | - Guang Nong
- Department of Microbiology and Cell Science, University of Florida - IFAS, Gainesville, FL, USA
| | - John D Rice
- Department of Microbiology and Cell Science, University of Florida - IFAS, Gainesville, FL, USA
| | - Maria Gallo
- Plant Molecular and Cellular Biology Program, Agronomy Department, Genetics Institute, University of Florida - IFAS, Gainesville, FL, USA
- Delaware Valley University, Doylestown, PA, USA
| | - James F Preston
- Department of Microbiology and Cell Science, University of Florida - IFAS, Gainesville, FL, USA
| | - Fredy Altpeter
- Plant Molecular and Cellular Biology Program, Agronomy Department, Genetics Institute, University of Florida - IFAS, Gainesville, FL, USA.
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18
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Willis JD, Grant JN, Mazarei M, Kline LM, Rempe CS, Collins AG, Turner GB, Decker SR, Sykes RW, Davis MF, Labbe N, Jurat-Fuentes JL, Stewart CN. The TcEG1 beetle ( Tribolium castaneum) cellulase produced in transgenic switchgrass is active at alkaline pH and auto-hydrolyzes biomass for increased cellobiose release. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:230. [PMID: 29213306 PMCID: PMC5707894 DOI: 10.1186/s13068-017-0918-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 09/28/2017] [Indexed: 05/17/2023]
Abstract
BACKGROUND Genetically engineered biofuel crops, such as switchgrass (Panicum virgatum L.), that produce their own cell wall-digesting cellulase enzymes would reduce costs of cellulosic biofuel production. To date, non-bioenergy plant models have been used in nearly all studies assessing the synthesis and activity of plant-produced fungal and bacterial cellulases. One potential source for cellulolytic enzyme genes is herbivorous insects adapted to digest plant cell walls. Here we examine the potential of transgenic switchgrass-produced TcEG1 cellulase from Tribolium castaneum (red flour beetle). This enzyme, when overproduced in Escherichia coli and Saccharomyces cerevisiae, efficiently digests cellulose at optima of 50 °C and pH 12.0. RESULTS TcEG1 that was produced in green transgenic switchgrass tissue had a range of endoglucanase activity of 0.16-0.05 units (µM glucose release/min/mg) at 50 °C and pH 12.0. TcEG1 activity from air-dried leaves was unchanged from that from green tissue, but when tissue was dried in a desiccant oven (46 °C), specific enzyme activity decreased by 60%. When transgenic biomass was "dropped-in" into an alkaline buffer (pH 12.0) and allowed to incubate at 50 °C, cellobiose release was increased up to 77% over non-transgenic biomass. Saccharification was increased in one transgenic event by 28%, which had a concurrent decrease in lignin content of 9%. Histological analysis revealed an increase in cell wall thickness with no change to cell area or perimeter. Transgenic plants produced more, albeit narrower, tillers with equivalent dry biomass as the control. CONCLUSIONS This work describes the first study in which an insect cellulase has been produced in transgenic plants; in this case, the dedicated bioenergy crop switchgrass. Switchgrass overexpressing the TcEG1 gene appeared to be morphologically similar to its non-transgenic control and produced equivalent dry biomass. Therefore, we propose TcEG1 transgenics could be bred with other transgenic germplasm (e.g., low-lignin lines) to yield new switchgrass with synergistically reduced recalcitrance to biofuel production. In addition, transgenes for other cell wall degrading enzymes may be stacked with TcEG1 in switchgrass to yield complementary cell wall digestion features and complete auto-hydrolysis.
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Affiliation(s)
- Jonathan D. Willis
- Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996 USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Joshua N. Grant
- Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996 USA
| | - Mitra Mazarei
- Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996 USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Lindsey M. Kline
- Center for Renewable Carbon, University of Tennessee, Knoxville, TN 37996 USA
| | - Caroline S. Rempe
- Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996 USA
- UT-ORNL Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, TN 37996 USA
| | - A. Grace Collins
- Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996 USA
| | - Geoffrey B. Turner
- The National Research Energy Laboratory, Golden, CO 80401 USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Stephen R. Decker
- The National Research Energy Laboratory, Golden, CO 80401 USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Robert W. Sykes
- The National Research Energy Laboratory, Golden, CO 80401 USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Mark F. Davis
- The National Research Energy Laboratory, Golden, CO 80401 USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Nicole Labbe
- Center for Renewable Carbon, University of Tennessee, Knoxville, TN 37996 USA
| | - Juan L. Jurat-Fuentes
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996 USA
| | - C. Neal Stewart
- Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996 USA
- UT-ORNL Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, TN 37996 USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
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19
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Park SH, Ong RG, Sticklen M. Strategies for the production of cell wall-deconstructing enzymes in lignocellulosic biomass and their utilization for biofuel production. PLANT BIOTECHNOLOGY JOURNAL 2016; 14:1329-44. [PMID: 26627868 PMCID: PMC5063159 DOI: 10.1111/pbi.12505] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 10/23/2015] [Accepted: 11/02/2015] [Indexed: 05/18/2023]
Abstract
Microbial cell wall-deconstructing enzymes are widely used in the food, wine, pulp and paper, textile, and detergent industries and will be heavily utilized by cellulosic biorefineries in the production of fuels and chemicals. Due to their ability to use freely available solar energy, genetically engineered bioenergy crops provide an attractive alternative to microbial bioreactors for the production of cell wall-deconstructing enzymes. This review article summarizes the efforts made within the last decade on the production of cell wall-deconstructing enzymes in planta for use in the deconstruction of lignocellulosic biomass. A number of strategies have been employed to increase enzyme yields and limit negative impacts on plant growth and development including targeting heterologous enzymes into specific subcellular compartments using signal peptides, using tissue-specific or inducible promoters to limit the expression of enzymes to certain portions of the plant or certain times, and fusion of amplification sequences upstream of the coding region to enhance expression. We also summarize methods that have been used to access and maintain activity of plant-generated enzymes when used in conjunction with thermochemical pretreatments for the production of lignocellulosic biofuels.
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Affiliation(s)
- Sang-Hyuck Park
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, USA
| | - Rebecca Garlock Ong
- Department of Chemical Engineering and Materials Science, DOE Great Lakes Bioenergy Research Center, Michigan State University, Lansing, MI, USA
- Department of Chemical Engineering, Michigan Technological University, Houghton, MI, USA
| | - Mariam Sticklen
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, USA
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20
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Willis JD, Mazarei M, Stewart CN. Transgenic Plant-Produced Hydrolytic Enzymes and the Potential of Insect Gut-Derived Hydrolases for Biofuels. FRONTIERS IN PLANT SCIENCE 2016; 7:675. [PMID: 27303411 PMCID: PMC4885837 DOI: 10.3389/fpls.2016.00675] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 05/02/2016] [Indexed: 05/25/2023]
Abstract
Various perennial C4 grass species have tremendous potential for use as lignocellulosic biofuel feedstocks. Currently available grasses require costly pre-treatment and exogenous hydrolytic enzyme application to break down complex cell wall polymers into sugars that can then be fermented into ethanol. It has long been hypothesized that engineered feedstock production of cell wall degrading (CWD) enzymes would be an efficient production platform for of exogenous hydrolytic enzymes. Most research has focused on plant overexpression of CWD enzyme-coding genes from free-living bacteria and fungi that naturally break down plant cell walls. Recently, it has been found that insect digestive tracts harbor novel sources of lignocellulolytic biocatalysts that might be exploited for biofuel production. These CWD enzyme genes can be located in the insect genomes or in symbiotic microbes. When CWD genes are transformed into plants, negative pleiotropic effects are possible such as unintended cell wall digestion. The use of codon optimization along with organelle and tissue specific targeting improves CWD enzyme yields. The literature teaches several important lessons on strategic deployment of CWD genes in transgenic plants, which is the focus of this review.
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Affiliation(s)
- Jonathan D. Willis
- Department of Plant Sciences, University of TennesseeKnoxville, TN, USA
- Oak Ridge National Laboratory, BioEnergy Science CenterOak Ridge, TN, USA
| | - Mitra Mazarei
- Department of Plant Sciences, University of TennesseeKnoxville, TN, USA
- Oak Ridge National Laboratory, BioEnergy Science CenterOak Ridge, TN, USA
| | - C. Neal Stewart
- Department of Plant Sciences, University of TennesseeKnoxville, TN, USA
- Oak Ridge National Laboratory, BioEnergy Science CenterOak Ridge, TN, USA
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21
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Zeilinger S, Gupta VK, Dahms TES, Silva RN, Singh HB, Upadhyay RS, Gomes EV, Tsui CKM, Nayak S C. Friends or foes? Emerging insights from fungal interactions with plants. FEMS Microbiol Rev 2016; 40:182-207. [PMID: 26591004 PMCID: PMC4778271 DOI: 10.1093/femsre/fuv045] [Citation(s) in RCA: 133] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 06/11/2015] [Accepted: 10/11/2015] [Indexed: 12/22/2022] Open
Abstract
Fungi interact with plants in various ways, with each interaction giving rise to different alterations in both partners. While fungal pathogens have detrimental effects on plant physiology, mutualistic fungi augment host defence responses to pathogens and/or improve plant nutrient uptake. Tropic growth towards plant roots or stomata, mediated by chemical and topographical signals, has been described for several fungi, with evidence of species-specific signals and sensing mechanisms. Fungal partners secrete bioactive molecules such as small peptide effectors, enzymes and secondary metabolites which facilitate colonization and contribute to both symbiotic and pathogenic relationships. There has been tremendous advancement in fungal molecular biology, omics sciences and microscopy in recent years, opening up new possibilities for the identification of key molecular mechanisms in plant-fungal interactions, the power of which is often borne out in their combination. Our fragmentary knowledge on the interactions between plants and fungi must be made whole to understand the potential of fungi in preventing plant diseases, improving plant productivity and understanding ecosystem stability. Here, we review innovative methods and the associated new insights into plant-fungal interactions.
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Affiliation(s)
- Susanne Zeilinger
- Institute of Microbiology, University of Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
| | - Vijai K Gupta
- Molecular Glycobiotechnology Group, Discipline of Biochemistry, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Tanya E S Dahms
- Department of Chemistry and Biochemistry, University of Regina, SK, Canada
| | - Roberto N Silva
- Department of Biochemistry and Immunology, Ribeirão Preto Medical School, University of São Paulo (USP), 14049-900 Ribeirão Preto, SP, Brazil
| | - Harikesh B Singh
- Department of Mycology and Plant Pathology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi 221 005, India
| | - Ram S Upadhyay
- Department of Botany, Banaras Hindu University, Varanasi 221 005, India
| | - Eriston Vieira Gomes
- Department of Biochemistry and Immunology, Ribeirão Preto Medical School, University of São Paulo (USP), 14049-900 Ribeirão Preto, SP, Brazil
| | - Clement Kin-Ming Tsui
- Department of Pathology and Laboratory Medicine, the University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Chandra Nayak S
- Department of Biotechnology, University of Mysore, Mysore-570001, Karnataka, India
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Castiglia D, Sannino L, Marcolongo L, Ionata E, Tamburino R, De Stradis A, Cobucci-Ponzano B, Moracci M, La Cara F, Scotti N. High-level expression of thermostable cellulolytic enzymes in tobacco transplastomic plants and their use in hydrolysis of an industrially pretreated Arundo donax L. biomass. BIOTECHNOLOGY FOR BIOFUELS 2016; 9:154. [PMID: 27453729 PMCID: PMC4957871 DOI: 10.1186/s13068-016-0569-z] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 07/12/2016] [Indexed: 05/06/2023]
Abstract
BACKGROUND Biofuels production from plant biomasses is a complex multi-step process with important economic burdens. Several biotechnological approaches have been pursued to reduce biofuels production costs. The aim of the present study was to explore the production in tobacco plastome of three genes encoding (hemi)cellulolytic enzymes from thermophilic and hyperthermophilic bacterium and Archaea, respectively, and test their application in the bioconversion of an important industrially pretreated biomass feedstock (A. donax) for production of second-generation biofuels. RESULTS The selected enzymes, endoglucanase, endo-β-1,4-xylanase and β-glucosidase, were expressed in tobacco plastome with a protein yield range from 2 % to more than 75 % of total soluble proteins (TSP). The accumulation of endoglucanase (up to 2 % TSP) gave altered plant phenotypes whose severity was directly linked to the enzyme yield. The most severe seedling-lethal phenotype was due to the impairment of plastid development associated to the binding of endoglucanase protein to thylakoids. Endo-β-1,4-xylanase and β-glucosidase, produced at very high level without detrimental effects on plant development, were enriched (fourfold) by heat treatment (105.4 and 255.4 U/mg, respectively). Both plastid-derived biocatalysts retained the main features of the native or recombinantly expressed enzymes with interesting differences. Plastid-derived xylanase and β-glucosidase resulted more thermophilic than the E. coli recombinant and native counterpart, respectively. Bioconversion experiments, carried out at 50 and 60 °C, demonstrated that plastid-derived enzymes were able to hydrolyse an industrially pretreated giant reed biomass. In particular, the replacement of commercial enzyme with plastid-derived xylanase, at 60 °C, produced an increase of both xylose recovery and hydrolysis rate; whereas the replacement of both xylanase and β-glucosidase produced glucose levels similar to those observed with the commercial cocktails, and xylose yields always higher in the whole 24-72 h range. CONCLUSIONS The very high production level of thermophilic and hyperthermophilic enzymes, their stability and bioconversion efficiencies described in this study demonstrate that plastid transformation represents a real cost-effective production platform for cellulolytic enzymes.
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Affiliation(s)
- Daniela Castiglia
- />CNR-IBBR UOS Portici, National Research Council of Italy, Institute of Biosciences and BioResources, Research Division Portici, Via Università 133, 80055 Portici, NA Italy
| | - Lorenza Sannino
- />CNR-IBBR UOS Portici, National Research Council of Italy, Institute of Biosciences and BioResources, Research Division Portici, Via Università 133, 80055 Portici, NA Italy
| | - Loredana Marcolongo
- />CNR-IBBR UOS Naples, National Research Council of Italy, Institute of Biosciences and BioResources, Research Division Naples, Via P. Castellino 111, Naples, Italy
- />CNR-IBAF UOS Napoli, National Research Council of Italy, Institute of Agro-environmental and Forest Biology, Research Division Naples, Via P. Castellino 111, Naples, Italy
| | - Elena Ionata
- />CNR-IBBR UOS Naples, National Research Council of Italy, Institute of Biosciences and BioResources, Research Division Naples, Via P. Castellino 111, Naples, Italy
- />CNR-IBAF UOS Napoli, National Research Council of Italy, Institute of Agro-environmental and Forest Biology, Research Division Naples, Via P. Castellino 111, Naples, Italy
| | - Rachele Tamburino
- />CNR-IBBR UOS Portici, National Research Council of Italy, Institute of Biosciences and BioResources, Research Division Portici, Via Università 133, 80055 Portici, NA Italy
| | - Angelo De Stradis
- />CNR-IPSP UOS Bari, National Research Council of Italy, Institute for Sustainable Plant Protection, Research Division Bari, Via Amendola 165/A, 70126 Bari, Italy
| | - Beatrice Cobucci-Ponzano
- />CNR-IBBR UOS Naples, National Research Council of Italy, Institute of Biosciences and BioResources, Research Division Naples, Via P. Castellino 111, Naples, Italy
| | - Marco Moracci
- />CNR-IBBR UOS Naples, National Research Council of Italy, Institute of Biosciences and BioResources, Research Division Naples, Via P. Castellino 111, Naples, Italy
| | - Francesco La Cara
- />CNR-IBBR UOS Naples, National Research Council of Italy, Institute of Biosciences and BioResources, Research Division Naples, Via P. Castellino 111, Naples, Italy
- />CNR-IBAF UOS Napoli, National Research Council of Italy, Institute of Agro-environmental and Forest Biology, Research Division Naples, Via P. Castellino 111, Naples, Italy
| | - Nunzia Scotti
- />CNR-IBBR UOS Portici, National Research Council of Italy, Institute of Biosciences and BioResources, Research Division Portici, Via Università 133, 80055 Portici, NA Italy
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Reis RS, Vale EDM, Heringer AS, Santa-Catarina C, Silveira V. Putrescine induces somatic embryo development and proteomic changes in embryogenic callus of sugarcane. J Proteomics 2016; 130:170-9. [DOI: 10.1016/j.jprot.2015.09.029] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Revised: 08/27/2015] [Accepted: 09/21/2015] [Indexed: 01/29/2023]
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Hoang NV, Furtado A, Botha FC, Simmons BA, Henry RJ. Potential for Genetic Improvement of Sugarcane as a Source of Biomass for Biofuels. Front Bioeng Biotechnol 2015; 3:182. [PMID: 26636072 PMCID: PMC4646955 DOI: 10.3389/fbioe.2015.00182] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Accepted: 10/26/2015] [Indexed: 11/13/2022] Open
Abstract
Sugarcane (Saccharum spp. hybrids) has great potential as a major feedstock for biofuel production worldwide. It is considered among the best options for producing biofuels today due to an exceptional biomass production capacity, high carbohydrate (sugar + fiber) content, and a favorable energy input/output ratio. To maximize the conversion of sugarcane biomass into biofuels, it is imperative to generate improved sugarcane varieties with better biomass degradability. However, unlike many diploid plants, where genetic tools are well developed, biotechnological improvement is hindered in sugarcane by our current limited understanding of the large and complex genome. Therefore, understanding the genetics of the key biofuel traits in sugarcane and optimization of sugarcane biomass composition will advance efficient conversion of sugarcane biomass into fermentable sugars for biofuel production. The large existing phenotypic variation in Saccharum germplasm and the availability of the current genomics technologies will allow biofuel traits to be characterized, the genetic basis of critical differences in biomass composition to be determined, and targets for improvement of sugarcane for biofuels to be established. Emerging options for genetic improvement of sugarcane for the use as a bioenergy crop are reviewed. This will better define the targets for potential genetic manipulation of sugarcane biomass composition for biofuels.
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Affiliation(s)
- Nam V. Hoang
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, QLD, Australia
- College of Agriculture and Forestry, Hue University, Hue, Vietnam
| | - Agnelo Furtado
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, QLD, Australia
| | - Frederik C. Botha
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, QLD, Australia
- Sugar Research Australia, Indooroopilly, QLD, Australia
| | - Blake A. Simmons
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, QLD, Australia
- Joint BioEnergy Institute, Emeryville, CA, USA
| | - Robert J. Henry
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, QLD, Australia
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Harrison MD, Geijskes RJ, Lloyd R, Miles S, Palupe A, Sainz MB, Dale JL. Recombinant cellulase accumulation in the leaves of mature, vegetatively propagated transgenic sugarcane. Mol Biotechnol 2015; 56:795-802. [PMID: 24793894 DOI: 10.1007/s12033-014-9758-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The cost of enzymes that hydrolyse lignocellulosic substrates to fermentable sugars needs to be reduced to make cellulosic ethanol a cost-competitive liquid transport fuel. Sugarcane is a perennial crop and the successful integration of cellulase transgenes into the sugarcane production system requires that transgene expression is stable in the ratoon. Herein, we compared the accumulation of recombinant fungal cellobiohydrolase I (CBH I), fungal cellobiohydrolase II (CBH II), and bacterial endoglucanase (EG) in the leaves of mature, initial transgenic sugarcane plants and their mature ratoon. Mature ratoon events containing equivalent or elevated levels of active CBH I, CBH II, and EG in the leaves were identified. Further, we have demonstrated that recombinant fungal CBH I and CBH II can resist proteolysis during sugarcane leaf senescence, while bacterial EG cannot. These results demonstrate the stability of cellulase enzyme transgene expression in transgenic sugarcane and the utility of sugarcane as a biofactory crop for production of cellulases.
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Affiliation(s)
- Mark D Harrison
- Syngenta Centre for Sugarcane Biofuels Development, Centre for Tropical Crops and Biocommodities, Queensland University of Technology, 2 George Street, Brisbane, QLD, 4001, Australia,
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Wu J, Wang M, Zhang H, Liu R. Extreme Thermophilic Enzyme CelB-m Efficiently Degrades the Cellulose in Transgenic Arabidopsis thaliana. Appl Biochem Biotechnol 2015; 177:362-72. [PMID: 26186956 DOI: 10.1007/s12010-015-1748-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 07/06/2015] [Indexed: 10/23/2022]
Abstract
Agricultural and forestry wastes abundant in the plant biomass are an important resource of green energy. However, little is known about how to exploit efficiently the resource. In this study, we isolated the CelB gene that encodes the extremely thermophilic cellulose-degrading enzyme from Thermotoga maritime. The enzyme-encoding gene CelB was optimized and reconstructed in N' codes by the code adaptability in Arabidopsis thaliana. Then, the optimized gene (CelB-m) or the recombinant gene (CBD-CelB) was fused with the plant binary vector which harbors the β-glucuronidase (GUS) gene that was transferred into Arabidopsis, respectively. GUS assay results showed CelB gene ubiquitous expression in transgenic plants. The enzyme-activity assays exhibited that the cellulase activity in the leaves of CelB-m transgenic plants were significantly higher than that of wild-type plants. The highest amount of enzymatic activity obtained was 131.2 U for every gram of fresh leaves in CBD-CelB plants. In addition, the enzymatic activity was stable at the temperature of 90 °C. These results suggested that the ectopic expression of pertinent biomass-degrading enzymes in transgenic plants can degrade effectively the plant biomass and lay a foundation on the application for the transgenic technique to crops.
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Affiliation(s)
- Jiandong Wu
- College of Life Sciences, Anhui Agricultural University, Hefei, 230036, China
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Tomassetti S, Pontiggia D, Verrascina I, Reca IB, Francocci F, Salvi G, Cervone F, Ferrari S. Controlled expression of pectic enzymes in Arabidopsis thaliana enhances biomass conversion without adverse effects on growth. PHYTOCHEMISTRY 2015; 112:221-30. [PMID: 25242621 DOI: 10.1016/j.phytochem.2014.08.026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 07/09/2014] [Accepted: 08/28/2014] [Indexed: 05/11/2023]
Abstract
Lignocellulosic biomass from agriculture wastes is a potential source of biofuel, but its use is currently limited by the recalcitrance of the plant cell wall to enzymatic digestion. Modification of the wall structural components can be a viable strategy to overcome this bottleneck. We have previously shown that the expression of a fungal polygalacturonase (pga2 from Aspergillus niger) in Arabidopsis and tobacco plants reduces the levels of de-esterified homogalacturonan in the cell wall and significantly increases saccharification efficiency. However, plants expressing pga2 show stunted growth and reduced biomass production, likely as a consequence of an extensive loss of pectin integrity during the whole plant life cycle. We report here that the expression in Arabidopsis of another pectic enzyme, the pectate lyase 1 (PL1) of Pectobacterium carotovorum, under the control of a chemically inducible promoter, results, after induction of the transgene, in a saccharification efficiency similar to that of plants expressing pga2. However, lines with high levels of transgene induction show reduced growth even in the absence of the inducer. To overcome the problem of plant fitness, we have generated Arabidopsis plants that express pga2 under the control of the promoter of SAG12, a gene expressed only during senescence. These plants expressed pga2 only at late stages of development, and their growth was comparable to that of WT plants. Notably, leaves and stems of transgenic plants were more easily digested by cellulase, compared to WT plants, only during senescence. Expression of cell wall-degrading enzymes at the end of the plant life cycle may be therefore a useful strategy to engineer crops unimpaired in biomass yield but improved for bioconversion.
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Affiliation(s)
- Susanna Tomassetti
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Piazzale Aldo Moro, 5, 00185 Roma, Italy
| | - Daniela Pontiggia
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Piazzale Aldo Moro, 5, 00185 Roma, Italy
| | - Ilaria Verrascina
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Piazzale Aldo Moro, 5, 00185 Roma, Italy
| | - Ida Barbara Reca
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Piazzale Aldo Moro, 5, 00185 Roma, Italy
| | - Fedra Francocci
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Piazzale Aldo Moro, 5, 00185 Roma, Italy
| | - Gianni Salvi
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Piazzale Aldo Moro, 5, 00185 Roma, Italy
| | - Felice Cervone
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Piazzale Aldo Moro, 5, 00185 Roma, Italy
| | - Simone Ferrari
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Piazzale Aldo Moro, 5, 00185 Roma, Italy.
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Ricroch AE, Hénard-Damave MC. Next biotech plants: new traits, crops, developers and technologies for addressing global challenges. Crit Rev Biotechnol 2015; 36:675-90. [PMID: 25641327 DOI: 10.3109/07388551.2015.1004521] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Most of the genetically modified (GM) plants currently commercialized encompass a handful of crop species (soybean, corn, cotton and canola) with agronomic characters (traits) directed against some biotic stresses (pest resistance, herbicide tolerance or both) and created by multinational companies. The same crops with agronomic traits already on the market today will continue to be commercialized, but there will be also a wider range of species with combined traits. The timeframe anticipated for market release of the next biotech plants will not only depend on science progress in research and development (R&D) in laboratories and fields, but also primarily on how demanding regulatory requirements are in countries where marketing approvals are pending. Regulatory constraints, including environmental and health impact assessments, have increased significantly in the past decades, delaying approvals and increasing their costs. This has sometimes discouraged public research entities and small and medium size plant breeding companies from using biotechnology and given preference to other technologies, not as stringently regulated. Nevertheless, R&D programs are flourishing in developing countries, boosted by the necessity to meet the global challenges that are food security of a booming world population while mitigating climate change impacts. Biotechnology is an instrument at the service of these imperatives and a wide variety of plants are currently tested for their high yield despite biotic and abiotic stresses. Many plants with higher water or nitrogen use efficiency, tolerant to cold, salinity or water submergence are being developed. Food security is not only a question of quantity but also of quality of agricultural and food products, to be available and accessible for the ones who need it the most. Many biotech plants (especially staple food) are therefore being developed with nutritional traits, such as biofortification in vitamins and metals. The main international seed companies continue to be the largest investors in plant biotechnology R&D, and often collaborate in the developing world with public institutions, private entities and philanthropic organizations. These partnerships are particularly present in Africa. In developed countries, plant biotechnology is also used for non-food purposes, such as the pharmaceutical, biofuel, starch, paper and textile industries. For example, plants are modified to specifically produce molecules with therapeutic uses, or with an improved biomass conversion efficiency, or producing larger volumes of feedstocks for biofuels. Various plant breeding technologies are now used in the entire spectrum of plant biotechnology: transgenesis producing proteins or RNAi. Cisgenesis (transgenes isolated from a crossable donor plant) and intragenesis (transgenes originate from the same species or a crossable species), null segregants are also used. To date, the next generation precision gene editing tools are developed in basic research. They include: clustered regularly interspaced short palindromic repeats (CRISPR), oligonucleotide-directed mutagenesis (ODM), transcription activator-like effects nucleases (TALENs) and zinc-finger nuclease (ZFN).
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Affiliation(s)
- Agnès E Ricroch
- a Department of Life Sciences and Health , AgroParisTech , Génétique évolutive et amélioration des plantes , Paris Cedex , France and
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Abstract
Genetic transformation of sugarcane has a tremendous potential to complement traditional breeding in crop improvement and will likely transform sugarcane into a bio-factory for value-added products. We describe here Agrobacterium tumefaciens-mediated transformation of sugarcane. Embryogenic callus induced from immature leaf whorls was used as target for transformation with the hypervirulent Agrobacterium strain AGL1 carrying a constitutive nptII expression cassette in vector pPZP200. Selection with 30 mg/L geneticin during the callus phase and 30 mg/L paromomycin during regeneration of shoots and roots effectively suppressed the development of non-transgenic plants. This protocol was successful with a commercially important sugarcane cultivar, CP-88-1762, at a transformation efficiency of two independent transgenic plants per g of callus.
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Affiliation(s)
- Hao Wu
- Agronomy Department, Plant Molecular and Cellular Biology Program, Genetics Institute, University of Florida, 3085 McCarty Hall, 110500, Gainesville, FL, 32611-0500, USA
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Li Q, Song J, Peng S, Wang JP, Qu GZ, Sederoff RR, Chiang VL. Plant biotechnology for lignocellulosic biofuel production. PLANT BIOTECHNOLOGY JOURNAL 2014; 12:1174-92. [PMID: 25330253 DOI: 10.1111/pbi.12273] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2014] [Revised: 08/11/2014] [Accepted: 09/05/2014] [Indexed: 05/18/2023]
Abstract
Lignocelluloses from plant cell walls are attractive resources for sustainable biofuel production. However, conversion of lignocellulose to biofuel is more expensive than other current technologies, due to the costs of chemical pretreatment and enzyme hydrolysis for cell wall deconstruction. Recalcitrance of cell walls to deconstruction has been reduced in many plant species by modifying plant cell walls through biotechnology. These results have been achieved by reducing lignin content and altering its composition and structure. Reduction of recalcitrance has also been achieved by manipulating hemicellulose biosynthesis and by overexpression of bacterial enzymes in plants to disrupt linkages in the lignin-carbohydrate complexes. These modified plants often have improved saccharification yield and higher ethanol production. Cell wall-degrading (CWD) enzymes from bacteria and fungi have been expressed at high levels in plants to increase the efficiency of saccharification compared with exogenous addition of cellulolytic enzymes. In planta expression of heat-stable CWD enzymes from bacterial thermophiles has made autohydrolysis possible. Transgenic plants can be engineered to reduce recalcitrance without any yield penalty, indicating that successful cell wall modification can be achieved without impacting cell wall integrity or plant development. A more complete understanding of cell wall formation and structure should greatly improve lignocellulosic feedstocks and reduce the cost of biofuel production.
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Affiliation(s)
- Quanzi Li
- State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin, China; State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, Beijing, China
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Furtado A, Lupoi JS, Hoang NV, Healey A, Singh S, Simmons BA, Henry RJ. Modifying plants for biofuel and biomaterial production. PLANT BIOTECHNOLOGY JOURNAL 2014; 12:1246-58. [PMID: 25431201 DOI: 10.1111/pbi.12300] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 08/28/2014] [Accepted: 10/23/2014] [Indexed: 05/08/2023]
Abstract
The productivity of plants as biofuel or biomaterial crops is established by both the yield of plant biomass per unit area of land and the efficiency of conversion of the biomass to biofuel. Higher yielding biofuel crops with increased conversion efficiencies allow production on a smaller land footprint minimizing competition with agriculture for food production and biodiversity conservation. Plants have traditionally been domesticated for food, fibre and feed applications. However, utilization for biofuels may require the breeding of novel phenotypes, or new species entirely. Genomics approaches support genetic selection strategies to deliver significant genetic improvement of plants as sources of biomass for biofuel manufacture. Genetic modification of plants provides a further range of options for improving the composition of biomass and for plant modifications to assist the fabrication of biofuels. The relative carbohydrate and lignin content influences the deconstruction of plant cell walls to biofuels. Key options for facilitating the deconstruction leading to higher monomeric sugar release from plants include increasing cellulose content, reducing cellulose crystallinity, and/or altering the amount or composition of noncellulosic polysaccharides or lignin. Modification of chemical linkages within and between these biomass components may improve the ease of deconstruction. Expression of enzymes in the plant may provide a cost-effective option for biochemical conversion to biofuel.
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Affiliation(s)
- Agnelo Furtado
- Queensland Alliance for Agriculture and Food Innovation, University of Queensland, Brisbane, Qld, Australia
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Harrison MD, Zhang Z, Shand K, Chong BF, Nichols J, Oeller P, O’Hara IM, Doherty WOS, Dale JL. The combination of plant-expressed cellobiohydrolase and low dosages of cellulases for the hydrolysis of sugar cane bagasse. BIOTECHNOLOGY FOR BIOFUELS 2014; 7:131. [PMID: 25254073 PMCID: PMC4172943 DOI: 10.1186/s13068-014-0131-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 08/27/2014] [Indexed: 05/18/2023]
Abstract
BACKGROUND The expression of biomass-degrading enzymes (such as cellobiohydrolases) in transgenic plants has the potential to reduce the costs of biomass saccharification by providing a source of enzymes to supplement commercial cellulase mixtures. Cellobiohydrolases are the main enzymes in commercial cellulase mixtures. In the present study, a cellobiohydrolase was expressed in transgenic corn stover leaf and assessed as an additive for two commercial cellulase mixtures for the saccharification of pretreated sugar cane bagasse obtained by different processes. RESULTS Recombinant cellobiohydrolase in the senescent leaves of transgenic corn was extracted using a simple buffer with no concentration step. The extract significantly enhanced the performance of Celluclast 1.5 L (a commercial cellulase mixture) by up to fourfold on sugar cane bagasse pretreated at the pilot scale using a dilute sulfuric acid steam explosion process compared to the commercial cellulase mixture on its own. Also, the extracts were able to enhance the performance of Cellic CTec2 (a commercial cellulase mixture) up to fourfold on a range of residues from sugar cane bagasse pretreated at the laboratory (using acidified ethylene carbonate/ethylene glycol, 1-butyl-3-methylimidazolium chloride, and ball-milling) and pilot (dilute sodium hydroxide and glycerol/hydrochloric acid steam explosion) scales. We have demonstrated using tap water as a solvent (under conditions that mimic an industrial process) extraction of about 90% recombinant cellobiohydrolase from senescent, transgenic corn stover leaf that had minimal tissue disruption. CONCLUSIONS The accumulation of recombinant cellobiohydrolase in senescent, transgenic corn stover leaf is a viable strategy to reduce the saccharification cost associated with the production of fermentable sugars from pretreated biomass. We envisage an industrial-scale process in which transgenic plants provide both fibre and biomass-degrading enzymes for pretreatment and enzymatic hydrolysis, respectively.
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Affiliation(s)
- Mark D Harrison
- />Syngenta Centre for Sugarcane Biofuels Development, Queensland University of Technology, GPO Box 2432, 2 George Street, Brisbane, Queensland 4001 Australia
- />Centre for Tropical Crops and Biocommodities, Queensland University of Technology, GPO Box 2432, 2 George Street, Brisbane, Queensland 4001 Australia
| | - Zhanying Zhang
- />Syngenta Centre for Sugarcane Biofuels Development, Queensland University of Technology, GPO Box 2432, 2 George Street, Brisbane, Queensland 4001 Australia
- />Centre for Tropical Crops and Biocommodities, Queensland University of Technology, GPO Box 2432, 2 George Street, Brisbane, Queensland 4001 Australia
| | - Kylie Shand
- />Syngenta Centre for Sugarcane Biofuels Development, Queensland University of Technology, GPO Box 2432, 2 George Street, Brisbane, Queensland 4001 Australia
- />Centre for Tropical Crops and Biocommodities, Queensland University of Technology, GPO Box 2432, 2 George Street, Brisbane, Queensland 4001 Australia
| | - Barrie Fong Chong
- />Syngenta Centre for Sugarcane Biofuels Development, Queensland University of Technology, GPO Box 2432, 2 George Street, Brisbane, Queensland 4001 Australia
- />Centre for Tropical Crops and Biocommodities, Queensland University of Technology, GPO Box 2432, 2 George Street, Brisbane, Queensland 4001 Australia
| | - Jason Nichols
- />Syngenta Biotechnology Inc., Research Triangle Park, 3054 East Cornwallis Road, Durham, NC 27709-2257 USA
| | - Paul Oeller
- />Syngenta Biotechnology Inc., Research Triangle Park, 3054 East Cornwallis Road, Durham, NC 27709-2257 USA
| | - Ian M O’Hara
- />Syngenta Centre for Sugarcane Biofuels Development, Queensland University of Technology, GPO Box 2432, 2 George Street, Brisbane, Queensland 4001 Australia
- />Centre for Tropical Crops and Biocommodities, Queensland University of Technology, GPO Box 2432, 2 George Street, Brisbane, Queensland 4001 Australia
| | - William OS Doherty
- />Centre for Tropical Crops and Biocommodities, Queensland University of Technology, GPO Box 2432, 2 George Street, Brisbane, Queensland 4001 Australia
| | - James L Dale
- />Syngenta Centre for Sugarcane Biofuels Development, Queensland University of Technology, GPO Box 2432, 2 George Street, Brisbane, Queensland 4001 Australia
- />Centre for Tropical Crops and Biocommodities, Queensland University of Technology, GPO Box 2432, 2 George Street, Brisbane, Queensland 4001 Australia
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Chong BF, Harrison MD, O’Hara IM. Stability of endoglucanases from mesophilic fungus and thermophilic bacterium in acidified polyols. Enzyme Microb Technol 2014; 61-62:55-60. [DOI: 10.1016/j.enzmictec.2014.04.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 04/23/2014] [Accepted: 04/23/2014] [Indexed: 11/16/2022]
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Pereira EO, Kolotilin I, Conley AJ, Menassa R. Production and characterization of in planta transiently produced polygalacturanase from Aspergillus niger and its fusions with hydrophobin or ELP tags. BMC Biotechnol 2014; 14:59. [PMID: 24970673 PMCID: PMC4083859 DOI: 10.1186/1472-6750-14-59] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 06/18/2014] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Pectinases play an important role in plant cell wall deconstruction and have potential in diverse industries such as food, wine, animal feed, textile, paper, fuel, and others. The demand for such enzymes is increasing exponentially, as are the efforts to improve their production and to implement their use in several industrial processes. The goal of this study was to examine the potential of producing polygalacturonase I from Aspergillus niger in plants and to investigate the effects of subcellular compartmentalization and protein fusions on its accumulation and activity. RESULTS Polygalacturonase I from Aspergillus niger (AnPGI) was transiently produced in Nicotiana benthamiana by targeting it to five different cellular compartments: apoplast, endoplasmic reticulum (ER), vacuole, chloroplast and cytosol. Accumulation levels of 2.5%, 3.0%, and 1.9% of total soluble protein (TSP) were observed in the apoplast, ER, and vacuole, respectively, and specific activity was significantly higher in vacuole-targeted AnPGI compared to the same enzyme targeted to the ER or apoplast. No accumulation was found for AnPGI when targeted to the chloroplast or cytosol. Analysis of AnPGI fused with elastin-like polypeptide (ELP) revealed a significant increase in the protein accumulation level, especially when targeted to the vacuole where the protein doubles its accumulation to 3.6% of TSP, while the hydrophobin (HFBI) fusion impaired AnPGI accumulation and both tags impaired activity, albeit to different extents. The recombinant protein showed activity against polygalacturonic acid with optimum conditions at pH 5.0 and temperature from 30 to 50°C, depending on its fusion. In vivo analysis of reducing sugar content revealed a higher release of reducing sugars in plant tissue expressing recombinant AnPGI compared to wild type N. benthamiana leaves. CONCLUSION Our results demonstrate that subcellular compartmentalization of enzymes has an impact on both the target protein accumulation and its activity, especially in the case of proteins that undergo post-translational modifications, and should be taken into consideration when protein production strategies are designed. Using plants to produce heterologous enzymes for the degradation of a key component of the plant cell wall could reduce the cost of biomass pretreatment for the production of cellulosic biofuels.
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Affiliation(s)
- Eridan Orlando Pereira
- Agriculture and Agri-Food Canada, 1391 Sandford Street, London, ON N5V 4T3, Canada
- Department of Biology, Western University, London, ON N6A 5B7, Canada
- Current address: Universidade Estadual do Ceará, Av. Dr. Silas Munguba, 1700 - Campus do Itaperi, Fortaleza 60714-903, Brazil
| | - Igor Kolotilin
- Agriculture and Agri-Food Canada, 1391 Sandford Street, London, ON N5V 4T3, Canada
| | | | - Rima Menassa
- Agriculture and Agri-Food Canada, 1391 Sandford Street, London, ON N5V 4T3, Canada
- Department of Biology, Western University, London, ON N6A 5B7, Canada
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Reis RR, da Cunha BADB, Martins PK, Martins MTB, Alekcevetch JC, Chalfun A, Andrade AC, Ribeiro AP, Qin F, Mizoi J, Yamaguchi-Shinozaki K, Nakashima K, Carvalho JDFC, de Sousa CAF, Nepomuceno AL, Kobayashi AK, Molinari HBC. Induced over-expression of AtDREB2A CA improves drought tolerance in sugarcane. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2014; 221-222:59-68. [PMID: 24656336 DOI: 10.1016/j.plantsci.2014.02.003] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 02/04/2014] [Accepted: 02/06/2014] [Indexed: 05/19/2023]
Abstract
Drought is one of the most challenging agricultural issues limiting sustainable sugarcane production and, in some cases, yield losses caused by drought are nearly 50%. DREB proteins play vital regulatory roles in abiotic stress responses in plants. The transcription factor DREB2A interacts with a cis-acting DRE sequence to activate the expression of downstream genes that are involved in drought-, salt- and heat-stress response in Arabidopsis thaliana. In the present study, we evaluated the effects of stress-inducible over-expression of AtDREB2A CA on gene expression, leaf water potential (ΨL), relative water content (RWC), sucrose content and gas exchanges of sugarcane plants submitted to a four-days water deficit treatment in a rhizotron-grown root system. The plants were also phenotyped by scanning the roots and measuring morphological parameters of the shoot. The stress-inducible expression of AtDREB2A CA in transgenic sugarcane led to the up-regulation of genes involved in plant response to drought stress. The transgenic plants maintained higher RWC and ΨL over 4 days after withholding water and had higher photosynthetic rates until the 3rd day of water-deficit. Induced expression of AtDREB2A CA in sugarcane increased sucrose levels and improved bud sprouting of the transgenic plants. Our results indicate that induced expression of AtDREB2A CA in sugarcane enhanced its drought tolerance without biomass penalty.
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Affiliation(s)
- Rafaela Ribeiro Reis
- Genetics and Biotechnology Laboratory, Embrapa Agroenergy (CNPAE), Brasília, DF, Brazil; Federal University of Lavras (UFLA), Lavras, MG, Brazil
| | | | - Polyana Kelly Martins
- Genetics and Biotechnology Laboratory, Embrapa Agroenergy (CNPAE), Brasília, DF, Brazil
| | | | | | | | - Alan Carvalho Andrade
- Molecular Genetics Laboratory, Embrapa Genetic Resources and Biotechnology (CENARGEN), Brasilia, DF, Brazil
| | - Ana Paula Ribeiro
- Genetics and Biotechnology Laboratory, Embrapa Agroenergy (CNPAE), Brasília, DF, Brazil; Federal University of Lavras (UFLA), Lavras, MG, Brazil
| | - Feng Qin
- Biological Resources and Post-harvest Division, Japan International Research Center for Agricultural Sciences (JIRCAS), Tsukuba, Japan
| | - Junya Mizoi
- Laboratory of Plant Molecular Physiology, The University of Tokyo, Tokyo, Japan
| | | | - Kazuo Nakashima
- Biological Resources and Post-harvest Division, Japan International Research Center for Agricultural Sciences (JIRCAS), Tsukuba, Japan
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Mir BA, Mewalal R, Mizrachi E, Myburg AA, Cowan DA. Recombinant hyperthermophilic enzyme expression in plants: a novel approach for lignocellulose digestion. Trends Biotechnol 2014; 32:281-9. [PMID: 24732021 DOI: 10.1016/j.tibtech.2014.03.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 02/14/2014] [Accepted: 03/05/2014] [Indexed: 10/25/2022]
Abstract
Plant biomass, as an abundant renewable carbon source, is a promising alternative to fossil fuels. However, the enzymes most commonly used for depolymerization of lignocellulosic biomass are expensive, and the development of cost-effective alternative conversion technologies would be desirable. One possible option is the heterologous expression of genes encoding lignocellulose-digesting enzymes in plant tissues. To overcome simultaneously issues of toxicity and incompatibility with high-temperature steam explosion processes, the use of heterologous genes encoding hyperthermophilic enzymes may be an attractive alternative. This approach could reduce the need for exogenous enzyme additions prior to fermentation, reducing the cost of the complete processing operation. This review highlights recent advances and future prospects for using hyperthermophilic enzymes in the biofuels industry.
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Affiliation(s)
- Bilal Ahmad Mir
- Center for Microbial Ecology and Genomics, Department of Genetics, University of Pretoria, Private bag X20, Pretoria 0028, South Africa; Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private bag X20, Pretoria 0028, South Africa
| | - Ritesh Mewalal
- Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private bag X20, Pretoria 0028, South Africa
| | - Eshchar Mizrachi
- Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private bag X20, Pretoria 0028, South Africa
| | - Alexander A Myburg
- Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private bag X20, Pretoria 0028, South Africa
| | - Don A Cowan
- Center for Microbial Ecology and Genomics, Department of Genetics, University of Pretoria, Private bag X20, Pretoria 0028, South Africa.
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Enhanced production of reducing sugars from transgenic rice expressing exo-glucanase under the control of a senescence-inducible promoter. Transgenic Res 2014; 23:531-7. [DOI: 10.1007/s11248-014-9786-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Accepted: 02/15/2014] [Indexed: 01/23/2023]
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Kinkema M, Geijskes J, Delucca P, Palupe A, Shand K, Coleman HD, Brinin A, Williams B, Sainz M, Dale JL. Improved molecular tools for sugar cane biotechnology. PLANT MOLECULAR BIOLOGY 2014; 84:497-508. [PMID: 24150836 DOI: 10.1007/s11103-013-0147-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Accepted: 10/16/2013] [Indexed: 06/02/2023]
Abstract
Sugar cane is a major source of food and fuel worldwide. Biotechnology has the potential to improve economically-important traits in sugar cane as well as diversify sugar cane beyond traditional applications such as sucrose production. High levels of transgene expression are key to the success of improving crops through biotechnology. Here we describe new molecular tools that both expand and improve gene expression capabilities in sugar cane. We have identified promoters that can be used to drive high levels of gene expression in the leaf and stem of transgenic sugar cane. One of these promoters, derived from the Cestrum yellow leaf curling virus, drives levels of constitutive transgene expression that are significantly higher than those achieved by the historical benchmark maize polyubiquitin-1 (Zm-Ubi1) promoter. A second promoter, the maize phosphonenolpyruvate carboxylate promoter, was found to be a strong, leaf-preferred promoter that enables levels of expression comparable to Zm-Ubi1 in this organ. Transgene expression was increased approximately 50-fold by gene modification, which included optimising the codon usage of the coding sequence to better suit sugar cane. We also describe a novel dual transcriptional enhancer that increased gene expression from different promoters, boosting expression from Zm-Ubi1 over eightfold. These molecular tools will be extremely valuable for the improvement of sugar cane through biotechnology.
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Affiliation(s)
- Mark Kinkema
- Syngenta Centre for Sugar Cane Biofuels Development, Centre for Tropical Crops and Biocommodities, Queensland University of Technology, Brisbane, QLD, 4001, Australia,
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Kinkema M, Geijskes RJ, Shand K, Coleman HD, De Lucca PC, Palupe A, Harrison MD, Jepson I, Dale JL, Sainz MB. An improved chemically inducible gene switch that functions in the monocotyledonous plant sugar cane. PLANT MOLECULAR BIOLOGY 2014; 84:443-54. [PMID: 24142380 DOI: 10.1007/s11103-013-0140-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2013] [Accepted: 10/07/2013] [Indexed: 05/03/2023]
Abstract
Chemically inducible gene switches can provide precise control over gene expression, enabling more specific analyses of gene function and expanding the plant biotechnology toolkit beyond traditional constitutive expression systems. The alc gene expression system is one of the most promising chemically inducible gene switches in plants because of its potential in both fundamental research and commercial biotechnology applications. However, there are no published reports demonstrating that this versatile gene switch is functional in transgenic monocotyledonous plants, which include some of the most important agricultural crops. We found that the original alc gene switch was ineffective in the monocotyledonous plant sugar cane, and describe a modified alc system that is functional in this globally significant crop. A promoter consisting of tandem copies of the ethanol receptor inverted repeat binding site, in combination with a minimal promoter sequence, was sufficient to give enhanced sensitivity and significantly higher levels of ethanol inducible gene expression. A longer CaMV 35S minimal promoter than was used in the original alc gene switch also substantially improved ethanol inducibility. Treating the roots with ethanol effectively induced the modified alc system in sugar cane leaves and stem, while an aerial spray was relatively ineffective. The extension of this chemically inducible gene expression system to sugar cane opens the door to new opportunities for basic research and crop biotechnology.
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Affiliation(s)
- Mark Kinkema
- Syngenta Centre for Sugar Cane Biofuels Development, Centre for Tropical Crops and Biocommodities, Queensland University of Technology, Brisbane, QLD, 4001, Australia,
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Lambertz C, Garvey M, Klinger J, Heesel D, Klose H, Fischer R, Commandeur U. Challenges and advances in the heterologous expression of cellulolytic enzymes: a review. BIOTECHNOLOGY FOR BIOFUELS 2014; 7:135. [PMID: 25356086 PMCID: PMC4212100 DOI: 10.1186/s13068-014-0135-5] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 09/03/2014] [Indexed: 05/03/2023]
Abstract
Second generation biofuel development is increasingly reliant on the recombinant expression of cellulases. Designing or identifying successful expression systems is thus of preeminent importance to industrial progress in the field. Recombinant production of cellulases has been performed using a wide range of expression systems in bacteria, yeasts and plants. In a number of these systems, particularly when using bacteria and plants, significant challenges have been experienced in expressing full-length proteins or proteins at high yield. Further difficulties have been encountered in designing recombinant systems for surface-display of cellulases and for use in consolidated bioprocessing in bacteria and yeast. For establishing cellulase expression in plants, various strategies are utilized to overcome problems, such as the auto-hydrolysis of developing plant cell walls. In this review, we investigate the major challenges, as well as the major advances made to date in the recombinant expression of cellulases across the commonly used bacterial, plant and yeast systems. We review some of the critical aspects to be considered for industrial-scale cellulase production.
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Affiliation(s)
- Camilla Lambertz
- />Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
| | - Megan Garvey
- />Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
- />Present address: School of Medicine, Deakin University, CSIRO Australian Animal Health Laboratory, 5 Portarlington Rd, Newcomb, VIC 3219 Australia
| | - Johannes Klinger
- />Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
| | - Dirk Heesel
- />Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
| | - Holger Klose
- />Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
- />Present address: Institute for Botany and Molecular Genetics, RWTH Aachen University, Worringerweg 3, 52074 Aachen, Germany
| | - Rainer Fischer
- />Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
- />Fraunhofer Institute for Molecular Biology and Applied Ecology, Forckenbeckstrasse 6, 52074 Aachen, Germany
| | - Ulrich Commandeur
- />Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
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41
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Harrison MD, Zhang Z, Shand K, O'Hara IM, Doherty WOS, Dale JL. Effect of pretreatment on saccharification of sugarcane bagasse by complex and simple enzyme mixtures. BIORESOURCE TECHNOLOGY 2013; 148:105-13. [PMID: 24045198 DOI: 10.1016/j.biortech.2013.08.099] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Revised: 08/15/2013] [Accepted: 08/17/2013] [Indexed: 05/10/2023]
Abstract
Saccharification of sugarcane bagasse pretreated at the pilot-scale with different processes (in combination with steam-explosion) was evaluated. Maximum glucan conversion with Celluclast 1.5L (15-25FPU/g glucan) was in the following order: glycerol/HCl>HCl>H2SO4>NaOH, with the glycerol system achieving ≈ 100% conversion. Surprisingly, the NaOH substrate achieved optimum saccharification with only 8 FPU/g glucan. Glucan conversions (3.6-6%) obtained with mixtures of endo-1,4-β-glucanase (EG) and β-glucosidase (βG) for the NaOH substrate were 2-6 times that of acid substrates. However, glucan conversions (15-60%) obtained with mixtures of cellobiohydrolase (CBH I) and βG on acidified glycerol substrate were 10-30% higher than those obtained for NaOH and acid substrates. The susceptibility of the substrates to enzymatic saccharification was explained by their physical and chemical attributes. Acidified glycerol pretreatment offers the opportunity to simplify the complexity of enzyme mixtures required for saccharification of lignocellulosics.
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Affiliation(s)
- Mark D Harrison
- Syngenta Centre for Sugarcane Biofuels Development, Centre for Tropical Crops and Biocommodities, Queensland University of Technology, GP.O. Box 2432, 2 George Street, Brisbane, Queensland 4001, Australia; Centre for Tropical Crops and Biocommodities, Queensland University of Technology, GP.O. Box 2432, 2 George Street, Brisbane, Queensland 4001, Australia.
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Garvey M, Klose H, Fischer R, Lambertz C, Commandeur U. Cellulases for biomass degradation: comparing recombinant cellulase expression platforms. Trends Biotechnol 2013; 31:581-93. [DOI: 10.1016/j.tibtech.2013.06.006] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 06/21/2013] [Accepted: 06/24/2013] [Indexed: 10/26/2022]
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Nahampun HN, Lee CJ, Jane JL, Wang K. Ectopic expression of bacterial amylopullulanase enhances bioethanol production from maize grain. PLANT CELL REPORTS 2013; 32:1393-1405. [PMID: 23652819 DOI: 10.1007/s00299-013-1453-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 04/18/2013] [Accepted: 04/25/2013] [Indexed: 06/02/2023]
Abstract
Heterologous expression of amylopullulanase in maize seeds leads to partial starch degradation into fermentable sugars, which enhances direct bioethanol production from maize grain. Utilization of maize in bioethanol industry in the United States reached ±13.3 billion gallons in 2012, most of which was derived from maize grain. Starch hydrolysis for bioethanol industry requires the addition of thermostable alpha amylase and amyloglucosidase (AMG) enzymes to break down the α-1,4 and α-1,6 glucosidic bonds of starch that limits the cost effectiveness of the process on an industrial scale due to its high cost. Transgenic plants expressing a thermostable starch-degrading enzyme can overcome this problem by omitting the addition of exogenous enzymes during the starch hydrolysis process. In this study, we generated transgenic maize plants expressing an amylopullulanase (APU) enzyme from the bacterium Thermoanaerobacter thermohydrosulfuricus. A truncated version of the dual functional APU (TrAPU) that possesses both alpha amylase and pullulanase activities was produced in maize endosperm tissue using a seed-specific promoter of 27-kD gamma zein. A number of analyses were performed at 85 °C, a temperature typically used for starch processing. Firstly, enzymatic assay and thin layer chromatography analysis showed direct starch hydrolysis into glucose. In addition, scanning electron microscopy illustrated porous and broken granules, suggesting starch autohydrolysis. Finally, bioethanol assay demonstrated that a 40.2 ± 2.63 % (14.7 ± 0.90 g ethanol per 100 g seed) maize starch to ethanol conversion was achieved from the TrAPU seeds. Conversion efficiency was improved to reach 90.5 % (33.1 ± 0.66 g ethanol per 100 g seed) when commercial amyloglucosidase was added after direct hydrolysis of TrAPU maize seeds. Our results provide evidence that enzymes for starch hydrolysis can be produced in maize seeds to enhance bioethanol production.
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Affiliation(s)
- Hartinio N Nahampun
- Interdepartmental Plant Biology Major, Iowa State University, Ames, IA 50011-1010, USA
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de Siqueira Ferreira S, Nishiyama MY, Paterson AH, Souza GM. Biofuel and energy crops: high-yield Saccharinae take center stage in the post-genomics era. Genome Biol 2013; 14:210. [PMID: 23805917 PMCID: PMC3707038 DOI: 10.1186/gb-2013-14-6-210] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The Saccharinae, especially sugarcane, Miscanthus and sorghum, present remarkable characteristics for bioenergy production. Biotechnology of these plants will be important for a sustainable feedstock supply. Herein, we review knowledge useful for their improvement and synergies gained by their parallel study.
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Affiliation(s)
- Savio de Siqueira Ferreira
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, SP, Brazil
| | - Milton Yutaka Nishiyama
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, SP, Brazil
| | - Andrew H Paterson
- Plant Genome Mapping Laboratory, University of Georgia, Athens, GA 30602, USA
| | - Glaucia Mendes Souza
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, SP, Brazil
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Ndimba BK, Ndimba RJ, Johnson TS, Waditee-Sirisattha R, Baba M, Sirisattha S, Shiraiwa Y, Agrawal GK, Rakwal R. Biofuels as a sustainable energy source: an update of the applications of proteomics in bioenergy crops and algae. J Proteomics 2013; 93:234-44. [PMID: 23792822 DOI: 10.1016/j.jprot.2013.05.041] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Revised: 04/28/2013] [Accepted: 05/30/2013] [Indexed: 11/29/2022]
Abstract
Sustainable energy is the need of the 21st century, not because of the numerous environmental and political reasons but because it is necessary to human civilization's energy future. Sustainable energy is loosely grouped into renewable energy, energy conservation, and sustainable transport disciplines. In this review, we deal with the renewable energy aspect focusing on the biomass from bioenergy crops to microalgae to produce biofuels to the utilization of high-throughput omics technologies, in particular proteomics in advancing our understanding and increasing biofuel production. We look at biofuel production by plant- and algal-based sources, and the role proteomics has played therein. This article is part of a Special Issue entitled: Translational Plant Proteomics.
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Affiliation(s)
- Bongani Kaiser Ndimba
- Proteomics Research and Services Unit, Biotechnology Platform, Agricultural Research Council, Infruitec-Nietvoorbij Campus, Stellenbosch, South Africa; Proteomics Research Group, Department of Biotechnology, University of the Western Cape, Bellville 7535, South Africa
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Klose H, Günl M, Usadel B, Fischer R, Commandeur U. Ethanol inducible expression of a mesophilic cellulase avoids adverse effects on plant development. BIOTECHNOLOGY FOR BIOFUELS 2013; 6:53. [PMID: 23587418 PMCID: PMC3643885 DOI: 10.1186/1754-6834-6-53] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Accepted: 04/12/2013] [Indexed: 05/07/2023]
Abstract
BACKGROUND Plant-produced biomass-degrading enzymes are promising tools for the processing of lignocellulose to fermentable sugars. A major limitation of in planta production is that high-level expression of such enzymes could potentially affect the structure and integrity of the plant cell wall and negatively influence plant growth and development. RESULTS Here, we evaluate the impact on tobacco plant development of constitutive versus alcohol-inducible expression of the endoglucanase TrCel5A from the mesophilic fungus Trichoderma reesei. Using this system, we are able to demonstrate that constitutive expression of the enzyme, controlled by the doubled Cauliflower Mosaic Virus promoter, leads to lower cellulose content of the plant combined with severe effects on plant growth. However, using an alcohol-inducible expression of the endoglucanase in the plant leaves, we achieved similar enzymatic expression levels with no changes in the crystalline cellulose content. CONCLUSION We were able to produce significant amounts of cellulase in the plant leaves without detrimental effects to plant development. These results demonstrate the potential feasibility of an inducible expression system for producing biomass degrading enzymes in plants.
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Affiliation(s)
- Holger Klose
- Institute for Molecular Biotechnology (Biology VII), RWTH Aachen University, Worringerweg 1, Aachen, 52074, Germany
| | - Markus Günl
- Institute of Bio- and Geosciences, IBG-2: Plant Sciences, Forschungszentrum Jülich, Leo-Brandt-Straße, Jülich, 52425, Germany
| | - Björn Usadel
- Institute of Bio- and Geosciences, IBG-2: Plant Sciences, Forschungszentrum Jülich, Leo-Brandt-Straße, Jülich, 52425, Germany
- Institute of Biology I, RWTH Aachen University, Worringerweg 1, Aachen, 52074, Germany
| | - Rainer Fischer
- Institute for Molecular Biotechnology (Biology VII), RWTH Aachen University, Worringerweg 1, Aachen, 52074, Germany
- Fraunhofer Institute for Molecular Biology and Applied Ecology (IME), Forckenbeckstrasse 6, Aachen, 52074, Germany
| | - Ulrich Commandeur
- Institute for Molecular Biotechnology (Biology VII), RWTH Aachen University, Worringerweg 1, Aachen, 52074, Germany
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Recovery of bovine lysozyme from transgenic sugarcane stalks: extraction, membrane filtration, and purification. Bioprocess Biosyst Eng 2013; 36:1407-16. [PMID: 23329238 DOI: 10.1007/s00449-012-0878-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2012] [Accepted: 12/19/2012] [Indexed: 01/06/2023]
Abstract
Increased industrial use of sugarcane (Saccharum spp. hybrid) for food and bioenergy has led to considerable improvements in its genetic transformation, which allowed the development of not only pest- and herbicide-resistant lines but also lines expressing high-value bioproducts and biopolymers. However, the economic benefits of using inexpensive transgenic plant systems for the production of industrial proteins could be offset by high downstream processing costs. In this work, transgenic sugarcane expressing recombinant bovine lysozyme (BvLz) was used to evaluate the feasibility of extraction and fractionation of recombinant proteins expressed in sugarcane stalks. Three pH levels (4.5, 6.0 and 7.5) and three salt concentrations (0, 50, and 150 mM NaCl) were tested to determine BvLz and total protein extractability. Two extraction conditions were selected to prepare BvLz extracts for further processing by cross-flow filtration, a suitable method for concentration and conditioning of extracts for direct applications or prior to chromatography. Partial removal of native proteins was achieved using a 100 kDa membrane but 20-30 % of the extracted BvLz was lost. Concentration of clarified extracts using a 3 kDa membrane resulted in twofold purification and 65 % recovery of BvLz. Loading of concentrated sugarcane extract on hydrophobic interaction chromatography (HIC) resulted in 50 % BvLz purity and 69 % recovery of BvLz.
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Shen B, Sun X, Zuo X, Shilling T, Apgar J, Ross M, Bougri O, Samoylov V, Parker M, Hancock E, Lucero H, Gray B, Ekborg NA, Zhang D, Johnson JCS, Lazar G, Raab RM. Engineering a thermoregulated intein-modified xylanase into maize for consolidated lignocellulosic biomass processing. Nat Biotechnol 2012; 30:1131-6. [PMID: 23086202 DOI: 10.1038/nbt.2402] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 09/28/2012] [Indexed: 11/09/2022]
Abstract
Plant cellulosic biomass is an abundant, low-cost feedstock for producing biofuels and chemicals. Expressing cell wall-degrading (CWD) enzymes (e.g. xylanases) in plant feedstocks could reduce the amount of enzymes required for feedstock pretreatment and hydrolysis during bioprocessing to release soluble sugars. However, in planta expression of xylanases can reduce biomass yield and plant fertility. To overcome this problem, we engineered a thermostable xylanase (XynB) with a thermostable self-splicing bacterial intein to control the xylanase activity. Intein-modified XynB (iXynB) variants were selected that have <10% wild-type enzymatic activity but recover >60% enzymatic activity upon intein self-splicing at temperatures >59 °C. Greenhouse-grown xynB maize expressing XynB has shriveled seeds and low fertility, but ixynB maize had normal seeds and fertility. Processing dried ixynB maize stover by temperature-regulated xylanase activation and hydrolysis in a cocktail of commercial CWD enzymes produced >90% theoretical glucose and >63% theoretical xylose yields.
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Heterologous expression of plant cell wall degrading enzymes for effective production of cellulosic biofuels. J Biomed Biotechnol 2012; 2012:405842. [PMID: 22911272 PMCID: PMC3403577 DOI: 10.1155/2012/405842] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2012] [Accepted: 05/20/2012] [Indexed: 11/17/2022] Open
Abstract
A major technical challenge in the cost-effective production of cellulosic biofuel is the need to lower the cost of plant cell wall degrading enzymes (PCDE), which is required for the production of sugars from biomass. Several competitive, low-cost technologies have been developed to produce PCDE in different host organisms such as Escherichia coli, Zymomonas mobilis, and plant. Selection of an ideal host organism is very important, because each host organism has its own unique features. Synthetic biology-aided tools enable heterologous expression of PCDE in recombinant E. coli or Z. mobilis and allow successful consolidated bioprocessing (CBP) in these microorganisms. In-planta expression provides an opportunity to simplify the process of enzyme production and plant biomass processing and leads to self-deconstruction of plant cell walls. Although the future of currently available technologies is difficult to predict, a complete and viable platform will most likely be available through the integration of the existing approaches with the development of breakthrough technologies.
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Brunecky R, Baker JO, Wei H, Taylor LE, Himmel ME, Decker SR. Analysis of transgenic glycoside hydrolases expressed in plants: T. reesei CBH I and A. cellulolyticus EI. Methods Mol Biol 2012; 908:197-211. [PMID: 22843401 DOI: 10.1007/978-1-61779-956-3_18] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Plant cell walls are composed of three basic structural biomolecules: cellulose, hemicellulose, and lignin with cellulose being the most abundant biopolymer on earth. Cellulose is composed of cellodextrins, which are linear polymers of glucose, and considered to be microcrystalline in structure. The conversion of cellulose to free glucose is one of the primary steps in the fermentative conversion of biomass to fuels and chemicals. However, the crystalline nature of this complex, noncovalent structure is highly resistant to enzymatic hydrolysis. Thus, the substantial cost currently associated with biomass saccharification primarily represents the cost of biomass degrading enzymes. Despite the fact that the microbial cellulose hydrolytic "machinery" for the recycling of carbon from plant biomass already exists in nature, the natural enzymatic degradation of plant material is typically a slow and complex process. Thus, if commercial biofuels production is to become a reality, it must be more cost-effective. One method proposed for achieving this objective is to express all or some of the requisite cellulolytic enzymes in planta, thus reducing both enzyme and thermochemical pretreatment costs.
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Affiliation(s)
- Roman Brunecky
- National Renewable Energy Laboratory, Biosciences Center, Golden, CO, USA.
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