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Betts NS, Collins HM, Shirley NJ, Cuesta-Seijo JA, Schwerdt JG, Phillips RJ, Finnie C, Fincher GB, Dockter C, Skadhauge B, Bulone V. Identification and spatio-temporal expression analysis of barley genes that encode putative modular xylanolytic enzymes. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2021; 308:110792. [PMID: 34034860 DOI: 10.1016/j.plantsci.2020.110792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 11/30/2020] [Accepted: 12/05/2020] [Indexed: 06/12/2023]
Abstract
Arabinoxylans are cell wall polysaccharides whose re-modelling and degradation during plant development are mediated by several classes of xylanolytic enzymes. Here, we present the identification and new annotation of twelve putative (1,4)-β-xylanase and six β-xylosidase genes, and their spatio-temporal expression patterns during vegetative and reproductive growth of barley (Hordeum vulgare cv. Navigator). The encoded xylanase proteins are all predicted to contain a conserved carbohydrate-binding module (CBM) and a catalytic glycoside hydrolase (GH) 10 domain. Additional domains in some xylanases define three discrete phylogenetic clades: one clade contains proteins with an additional N-terminal signal sequence, while another clade contains proteins with multiple CBMs. Homology modelling revealed that all fifteen xylanases likely contain a third domain, a β-sandwich folded from two non-contiguous sequence segments that bracket the catalytic GH domain, which may explain why the full length protein is required for correct folding of the active enzyme. Similarly, predicted xylosidase proteins share a highly conserved domain structure, each with an N-terminal signal peptide, a split GH 3 domain, and a C-terminal fibronectin-like domain. Several genes appear to be ubiquitously expressed during barley growth and development, while four newly annotated xylanase and xylosidase genes are expressed at extremely high levels, which may be of broader interest for industrial applications where cell wall degradation is necessary.
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Affiliation(s)
- Natalie S Betts
- School of Agriculture, Food and Wine, Waite Campus, Glen Osmond SA 5064 Australia.
| | - Helen M Collins
- School of Agriculture, Food and Wine, Waite Campus, Glen Osmond SA 5064 Australia.
| | - Neil J Shirley
- School of Agriculture, Food and Wine, Waite Campus, Glen Osmond SA 5064 Australia
| | - Jose A Cuesta-Seijo
- Carlsberg Research Laboratory, J.C. Jacobsens Gade 4, 1799 Copenhagen V, Denmark.
| | - Julian G Schwerdt
- School of Agriculture, Food and Wine, Waite Campus, Glen Osmond SA 5064 Australia.
| | - Renee J Phillips
- School of Agriculture, Food and Wine, Waite Campus, Glen Osmond SA 5064 Australia.
| | - Christine Finnie
- Carlsberg Research Laboratory, J.C. Jacobsens Gade 4, 1799 Copenhagen V, Denmark
| | - Geoffrey B Fincher
- School of Agriculture, Food and Wine, Waite Campus, Glen Osmond SA 5064 Australia.
| | - Christoph Dockter
- Carlsberg Research Laboratory, J.C. Jacobsens Gade 4, 1799 Copenhagen V, Denmark.
| | - Birgitte Skadhauge
- Carlsberg Research Laboratory, J.C. Jacobsens Gade 4, 1799 Copenhagen V, Denmark.
| | - Vincent Bulone
- School of Agriculture, Food and Wine, Waite Campus, Glen Osmond SA 5064 Australia; Division of Glycoscience, Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology and Health, Royal Institute of Technology (KTH), AlbaNova University Centre, 106 91 Stockholm, Sweden.
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Lu X, Fang Y, Tian B, Tong T, Wang J, Wang H, Cai S, Hu J, Zeng D, Xu H, Zhang X, Xue D. Genetic variation of HvXYN1 associated with endoxylanase activity and TAX content in barley (Hordeum vulgare L.). BMC PLANT BIOLOGY 2019; 19:170. [PMID: 31039733 PMCID: PMC6492322 DOI: 10.1186/s12870-019-1747-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 03/29/2019] [Indexed: 05/16/2023]
Abstract
BACKGROUND Endo-β-1,4-xylanase1 (EA), the key endoxylanase in plants, is involved in the degradation of arabinoxylan during grain germination. In barley (Hordeum vulgare L.), one gene (HvXYN-1) that encode a endo-beta-1,4-xylanase, has been cloned. However, the single nucleotide polymorphisms (SNPs) that affect the endoxylanase activity and total arabinoxylan (TAX) content have yet to be characterized. The investigation of genetic variation in HvXYN1 may facilitate a better understanding of the relationship between TAX content and EA activity in barley. RESULTS In the current study, 56 polymorphisms were detected in HvXYN1 among 210 barley accessions collected from 34 countries, with 10 distinct haplotypes identified. The SNPs at positions 110, 305, 1045, 1417, 1504, 1597, 1880 bp in the genomic region of HvXYN1 were significantly associated with EA activity (P < 0.0001), and the sites 110, 305, and 1045 were highly significantly associated with TAX content. The amount of phenotypic variation in a given trait explained by each associated polymorphism ranged from 6.96 to 9.85%. Most notably, we found two variants at positions 1504 bp and 1880 bp in the second exon that significantly (P < 0.0001) affected EA activity; this result could be used in breeding programs to improve beer quality. In addition, African accessions had the highest EA activity and TAX content, and the richest germplasm resources were from Asia, indicating the high potential value of Asian barley. CONCLUSION This study provided insight into understanding the relationship, EA activity, TAX content with the SNPs of HvXYN1 in barley. These SNPs can be applied as DNA markers in breeding programs to improve the quality of barley for beer brewing after further validation.
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Affiliation(s)
- Xueli Lu
- College of Life and Environmental Sciences, Hangzhou Normal University, 16 Xiasha Road, Hangzhou, 310036, China
- State Key Laboratory of Rice Biology, China National Rice Research Institute, 359 Tiyu Road, Hangzhou, 310006, China
| | - Yunxia Fang
- College of Life and Environmental Sciences, Hangzhou Normal University, 16 Xiasha Road, Hangzhou, 310036, China
| | - Bin Tian
- College of Life and Environmental Sciences, Hangzhou Normal University, 16 Xiasha Road, Hangzhou, 310036, China
| | - Tao Tong
- College of Life and Environmental Sciences, Hangzhou Normal University, 16 Xiasha Road, Hangzhou, 310036, China
| | - Jiahui Wang
- College of Life and Environmental Sciences, Hangzhou Normal University, 16 Xiasha Road, Hangzhou, 310036, China
| | - Hua Wang
- State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, Zhejiang Academy of Agricultural Science, 298 Deshengzhong Road, Hangzhou, 310021, China
| | - Shengguan Cai
- Agronomy Department, Key Laboratory of Crop Germplasm Resource of Zhejiang Province, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China
| | - Jiang Hu
- State Key Laboratory of Rice Biology, China National Rice Research Institute, 359 Tiyu Road, Hangzhou, 310006, China
| | - Dali Zeng
- State Key Laboratory of Rice Biology, China National Rice Research Institute, 359 Tiyu Road, Hangzhou, 310006, China
| | - Heng Xu
- State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, Zhejiang Academy of Agricultural Science, 298 Deshengzhong Road, Hangzhou, 310021, China
| | - Xiaoqin Zhang
- College of Life and Environmental Sciences, Hangzhou Normal University, 16 Xiasha Road, Hangzhou, 310036, China.
| | - Dawei Xue
- College of Life and Environmental Sciences, Hangzhou Normal University, 16 Xiasha Road, Hangzhou, 310036, China.
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Courtin CM, Broekaert WF, Swennen K, Aerts G, Van Craeyveld V, Delcour JA. Occurrence of Arabinoxylo-Oligosaccharides and Arabinogalactan Peptides in Beer. JOURNAL OF THE AMERICAN SOCIETY OF BREWING CHEMISTS 2018. [DOI: 10.1094/asbcj-2009-0323-01] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Christophe M. Courtin
- Laboratory of Food Chemistry and Biochemistry and Leuven Food Science and Nutrition Research Center (LFORCE), K. U. Leuven, Leuven, Belgium
| | - Willem F. Broekaert
- Laboratory of Food Chemistry and Biochemistry and Leuven Food Science and Nutrition Research Center (LFORCE), K. U. Leuven, Leuven, Belgium
| | - Katrien Swennen
- Laboratory of Food Chemistry and Biochemistry and Leuven Food Science and Nutrition Research Center (LFORCE), K. U. Leuven, Leuven, Belgium
| | - Guido Aerts
- Laboratory of Enzyme and Brewing Technology, KaHo St.-Lieven, Gent, Belgium
| | - Valerie Van Craeyveld
- Laboratory of Food Chemistry and Biochemistry and LFORCE, K. U. Leuven, Leuven, Belgium
| | - Jan A. Delcour
- Laboratory of Food Chemistry and Biochemistry and LFORCE, K. U. Leuven, Leuven, Belgium
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4
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Andriotis VME, Rejzek M, Barclay E, Rugen MD, Field RA, Smith AM. Cell wall degradation is required for normal starch mobilisation in barley endosperm. Sci Rep 2016; 6:33215. [PMID: 27622597 PMCID: PMC5020691 DOI: 10.1038/srep33215] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 08/12/2016] [Indexed: 01/02/2023] Open
Abstract
Starch degradation in barley endosperm provides carbon for early seedling growth, but the control of this process is poorly understood. We investigated whether endosperm cell wall degradation is an important determinant of the rate of starch degradation. We identified iminosugar inhibitors of enzymes that degrade the cell wall component arabinoxylan. The iminosugar 1,4-dideoxy-1, 4-imino-l-arabinitol (LAB) inhibits arabinoxylan arabinofuranohydrolase (AXAH) but does not inhibit the main starch-degrading enzymes α- and β-amylase and limit dextrinase. AXAH activity in the endosperm appears soon after the onset of germination and resides in dimers putatively containing two isoforms, AXAH1 and AXAH2. Upon grain imbibition, mobilisation of arabinoxylan and starch spreads across the endosperm from the aleurone towards the crease. The front of arabinoxylan degradation precedes that of starch degradation. Incubation of grains with LAB decreases the rate of loss of both arabinoxylan and starch, and retards the spread of both degradation processes across the endosperm. We propose that starch degradation in the endosperm is dependent on cell wall degradation, which permeabilises the walls and thus permits rapid diffusion of amylolytic enzymes. AXAH may be of particular importance in this respect. These results provide new insights into the mobilization of endosperm reserves to support early seedling growth.
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Affiliation(s)
| | - Martin Rejzek
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Elaine Barclay
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Michael D. Rugen
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Robert A. Field
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Alison M. Smith
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
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Olukolu BA, Tracy WF, Wisser R, De Vries B, Balint-Kurti PJ. A Genome-Wide Association Study for Partial Resistance to Maize Common Rust. PHYTOPATHOLOGY 2016; 106:745-51. [PMID: 27003507 DOI: 10.1094/phyto-11-15-0305-r] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Quantitative resistance to maize common rust (causal agent Puccinia sorghi) was assessed in an association mapping population of 274 diverse inbred lines. Resistance to common rust was found to be moderately correlated with resistance to three other diseases and with the severity of the hypersensitive defense response previously assessed in the same population. Using a mixed linear model accounting for the confounding effects of population structure and flowering time, genome-wide association tests were performed based at 246,497 single-nucleotide polymorphism loci. Three loci associated with maize common rust resistance were identified. Candidate genes at each locus had predicted roles, mainly in cell wall modification. Other candidate genes included a resistance gene and a gene with a predicted role in regulating accumulation of reactive oxygen species.
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Affiliation(s)
- Bode A Olukolu
- First author: Department of Plant Pathology and Department of Horticulture, North Carolina State University, Raleigh 27695; second and fourth authors: Department of Agronomy, University of Wisconsin-Madison, Madison 53706; third author: Department of Plant & Soil Sciences, University of Delaware, Newark 19716; and fifth author: Department of Plant Pathology, North Carolina State University, and United States Department of Agriculture-Agricultural Research Service Plant Science Research Unit, Raleigh, NC 27695
| | - William F Tracy
- First author: Department of Plant Pathology and Department of Horticulture, North Carolina State University, Raleigh 27695; second and fourth authors: Department of Agronomy, University of Wisconsin-Madison, Madison 53706; third author: Department of Plant & Soil Sciences, University of Delaware, Newark 19716; and fifth author: Department of Plant Pathology, North Carolina State University, and United States Department of Agriculture-Agricultural Research Service Plant Science Research Unit, Raleigh, NC 27695
| | - Randall Wisser
- First author: Department of Plant Pathology and Department of Horticulture, North Carolina State University, Raleigh 27695; second and fourth authors: Department of Agronomy, University of Wisconsin-Madison, Madison 53706; third author: Department of Plant & Soil Sciences, University of Delaware, Newark 19716; and fifth author: Department of Plant Pathology, North Carolina State University, and United States Department of Agriculture-Agricultural Research Service Plant Science Research Unit, Raleigh, NC 27695
| | - Brian De Vries
- First author: Department of Plant Pathology and Department of Horticulture, North Carolina State University, Raleigh 27695; second and fourth authors: Department of Agronomy, University of Wisconsin-Madison, Madison 53706; third author: Department of Plant & Soil Sciences, University of Delaware, Newark 19716; and fifth author: Department of Plant Pathology, North Carolina State University, and United States Department of Agriculture-Agricultural Research Service Plant Science Research Unit, Raleigh, NC 27695
| | - Peter J Balint-Kurti
- First author: Department of Plant Pathology and Department of Horticulture, North Carolina State University, Raleigh 27695; second and fourth authors: Department of Agronomy, University of Wisconsin-Madison, Madison 53706; third author: Department of Plant & Soil Sciences, University of Delaware, Newark 19716; and fifth author: Department of Plant Pathology, North Carolina State University, and United States Department of Agriculture-Agricultural Research Service Plant Science Research Unit, Raleigh, NC 27695
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6
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Iminosugar inhibitors of carbohydrate-active enzymes that underpin cereal grain germination and endosperm metabolism. Biochem Soc Trans 2016; 44:159-65. [PMID: 26862201 PMCID: PMC4747157 DOI: 10.1042/bst20150222] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Starch is a major energy store in plants. It provides most of the calories in the human diet and, as a bulk commodity, it is used across broad industry sectors. Starch synthesis and degradation are not fully understood, owing to challenging biochemistry at the liquid/solid interface and relatively limited knowledge about the nature and control of starch degradation in plants. Increased societal and commercial demand for enhanced yield and quality in starch crops requires a better understanding of starch metabolism as a whole. Here we review recent advances in understanding the roles of carbohydrate-active enzymes in starch degradation in cereal grains through complementary chemical and molecular genetics. These approaches have allowed us to start dissecting aspects of starch degradation and the interplay with cell-wall polysaccharide hydrolysis during germination. With a view to improving and diversifying the properties and uses of cereal grains, it is possible that starch degradation may be amenable to manipulation through genetic or chemical intervention at the level of cell wall metabolism, rather than simply in the starch degradation pathway per se.
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7
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Derba-Maceluch M, Awano T, Takahashi J, Lucenius J, Ratke C, Kontro I, Busse-Wicher M, Kosik O, Tanaka R, Winzéll A, Kallas Å, Leśniewska J, Berthold F, Immerzeel P, Teeri TT, Ezcurra I, Dupree P, Serimaa R, Mellerowicz EJ. Suppression of xylan endotransglycosylase PtxtXyn10A affects cellulose microfibril angle in secondary wall in aspen wood. THE NEW PHYTOLOGIST 2015; 205:666-81. [PMID: 25307149 DOI: 10.1111/nph.13099] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 08/25/2014] [Indexed: 05/02/2023]
Abstract
Certain xylanases from family GH10 are highly expressed during secondary wall deposition, but their function is unknown. We carried out functional analyses of the secondary-wall specific PtxtXyn10A in hybrid aspen (Populus tremula × tremuloides). PtxtXyn10A function was analysed by expression studies, overexpression in Arabidopsis protoplasts and by downregulation in aspen. PtxtXyn10A overexpression in Arabidopsis protoplasts resulted in increased xylan endotransglycosylation rather than hydrolysis. In aspen, the enzyme was found to be proteolytically processed to a 68 kDa peptide and residing in cell walls. Its downregulation resulted in a corresponding decrease in xylan endotransglycosylase activity and no change in xylanase activity. This did not alter xylan molecular weight or its branching pattern but affected the cellulose-microfibril angle in wood fibres, increased primary growth (stem elongation, leaf formation and enlargement) and reduced the tendency to form tension wood. Transcriptomes of transgenic plants showed downregulation of tension wood related genes and changes in stress-responsive genes. The data indicate that PtxtXyn10A acts as a xylan endotransglycosylase and its main function is to release tensional stresses arising during secondary wall deposition. Furthermore, they suggest that regulation of stresses in secondary walls plays a vital role in plant development.
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Affiliation(s)
- Marta Derba-Maceluch
- Department of Forest Genetics and Plant Physiology, SLU, Umeå Plant Science Centre (UPSC), Umeå, Sweden
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8
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Johnston SL, Prakash R, Chen NJ, Kumagai MH, Turano HM, Cooney JM, Atkinson RG, Paull RE, Cheetamun R, Bacic A, Brummell DA, Schröder R. An enzyme activity capable of endotransglycosylation of heteroxylan polysaccharides is present in plant primary cell walls. PLANTA 2013; 237:173-87. [PMID: 23001197 DOI: 10.1007/s00425-012-1766-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2012] [Accepted: 09/03/2012] [Indexed: 06/01/2023]
Abstract
Heteroxylans in the plant cell wall have been proposed to have a role analogous to that of xyloglucans or heteromannans, forming growth-restraining networks by interlocking cellulose microfibrils. A xylan endotransglycosylase has been identified that can transglycosylate heteroxylan polysaccharides in the presence of xylan-derived oligosaccharides. High activity was detected in ripe fruit of papaya (Carica papaya), but activity was also found in a range of other fruits, imbibed seeds and rapidly growing seedlings of cereals. Xylan endotransglycosylase from ripe papaya fruit used a range of heteroxylans, such as wheat arabinoxylan, birchwood glucuronoxylan and various heteroxylans from dicotyledonous primary cell walls purified from tomato and papaya fruit, as donor molecules. As acceptor molecules, the enzyme preferentially used xylopentaitol over xylohexaitol or shorter-length acceptors. Xylan endotransglycosylase was active over a broad pH range and could perform transglycosylation reactions up to 55 °C. Xylan endotransglycosylase activity was purified from ripe papaya fruit by ultrafiltration and cation exchange chromatography. Highest endotransglycosylase activity was identified in fractions that also contained high xylan hydrolase activity and correlated with the presence of the endoxylanase CpaEXY1. Recombinant CpaEXY1 protein transiently over-expressed in Nicotiana benthamiana leaves showed both endoxylanase and xylan endotransglycosylase activities in vitro, suggesting that CpaEXY1 is a single enzyme with dual activity in planta. Purified native CpaEXY1 showed two- to fourfold higher endoxylanase than endotransglycosylase activity, suggesting that CpaEXY1 may act primarily as a hydrolase. We propose that xylan endotransglycosylase activity (like xyloglucan and mannan endotransglycosylase activities) could be involved in remodelling or re-arrangement of heteroxylans of the cellulose-non-cellulosic cell wall framework.
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Affiliation(s)
- Sarah L Johnston
- The New Zealand Institute for Plant and Food Research Limited, Mount Albert Research Centre, Private Bag 92169, Auckland 1142, New Zealand
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9
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Differential protein expression associated with heat stress in Antarctic microalga. BIOCHIP JOURNAL 2012. [DOI: 10.1007/s13206-012-6310-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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10
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Elrouby N, Bureau TE. Bs1, a new chimeric gene formed by retrotransposon-mediated exon shuffling in maize. PLANT PHYSIOLOGY 2010; 153:1413-24. [PMID: 20488894 PMCID: PMC2899935 DOI: 10.1104/pp.110.157420] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Accepted: 05/16/2010] [Indexed: 05/19/2023]
Abstract
Transposons are major components of all eukaryotic genomes. Although traditionally regarded as causes of detrimental mutations, recent evidence suggests that transposons may play a role in host gene diversification and evolution. For example, host gene transduction by retroelements has been suggested to be both common and to have the potential to create new chimeric genes by the shuffling of existing sequences. We have previously shown that the maize (Zea mays subsp. mays) retrotransposon Bs1 has transduced sequences from three different host genes. Here, we provide evidence that these transduction events led to the generation of a chimeric new gene that is both transcribed and translated. Expression of Bs1 is tightly controlled and occurs during a narrow developmental window in early ear development. Although all Bs1-associated transduction events took place before Zea speciation, a full uninterrupted open reading frame encoding the BS1 protein may have arisen in domesticated maize or in the diverse populations of its progenitor Z. mays subsp. parviglumis. We discuss potential functions based on domain conservation and evidence for functional constraints between the transduced sequences and their host gene counterparts.
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Affiliation(s)
- Nabil Elrouby
- Department of Biology, McGill University, Montreal, Quebec, Canada.
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11
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Baba K, Park YW, Kaku T, Kaida R, Takeuchi M, Yoshida M, Hosoo Y, Ojio Y, Okuyama T, Taniguchi T, Ohmiya Y, Kondo T, Shani Z, Shoseyov O, Awano T, Serada S, Norioka N, Norioka S, Hayashi T. Xyloglucan for generating tensile stress to bend tree stem. MOLECULAR PLANT 2009; 2:893-903. [PMID: 19825666 DOI: 10.1093/mp/ssp054] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
In response to environmental variation, angiosperm trees bend their stems by forming tension wood, which consists of a cellulose-rich G (gelatinous)-layer in the walls of fiber cells and generates abnormal tensile stress in the secondary xylem. We produced transgenic poplar plants overexpressing several endoglycanases to reduce each specific polysaccharide in the cell wall, as the secondary xylem consists of primary and secondary wall layers. When placed horizontally, the basal regions of stems of transgenic poplars overexpressing xyloglucanase alone could not bend upward due to low strain in the tension side of the xylem. In the wild-type plants, xyloglucan was found in the inner surface of G-layers during multiple layering. In situ xyloglucan endotransglucosylase (XET) activity showed that the incorporation of whole xyloglucan, potentially for wall tightening, began at the inner surface layers S1 and S2 and was retained throughout G-layer development, while the incorporation of xyloglucan heptasaccharide (XXXG) for wall loosening occurred in the primary wall of the expanding zone. We propose that the xyloglucan network is reinforced by XET to form a further connection between wall-bound and secreted xyloglucans in order to withstand the tensile stress created within the cellulose G-layer microfibrils.
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Affiliation(s)
- Kei'ichi Baba
- Kyoto University, RISH, Gokasho, Uji, Kyoto 611-0011, Japan
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Burton RA, Collins HM, Fincher GB. The Role of Endosperm Cell Walls in Barley Malting Quality. ADVANCED TOPICS IN SCIENCE AND TECHNOLOGY IN CHINA 2009. [DOI: 10.1007/978-3-642-01279-2_7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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13
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Mallard S, Nègre S, Pouya S, Gaudet D, Lu ZX, Dedryver F. Adult plant resistance-related gene expression in 'Camp Remy' wheat inoculated with Puccinia striiformis. MOLECULAR PLANT PATHOLOGY 2008; 9:213-25. [PMID: 18705853 PMCID: PMC6640271 DOI: 10.1111/j.1364-3703.2007.00459.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The French wheat variety 'Camp Remy' (CR) possesses a durable, adult plant resistance to yellow rust (YR), caused by the pathogen Puccinia striiformis. Using cDNA-AFLP on different sets of heterogeneous inbred families (HIFs) derived from the cross CR x Récital, we compared gene expression profiles during one seedling and two adult developmental stages following inoculation with P. striiformis. Transcripts differentially expressed in response to YR infection were isolated and cloned. Sequence analysis of the resultant clones revealed several classes of putative genes, including those related to resistance/defence responses, transcription and signal transduction, and primary metabolism. The expression profiles of seven selected genes were obtained using real-time PCR in CR leaves at the same three stages of development. The results confirmed the stage-specific expression of the genes at one or two specific stages in response to P. striiformis infection and demonstrated that CR modifies the expression of some resistance/defence-related genes during its transition from the seedling to adult growth stages. These results provided the first clue to understand the molecular basis of quantitative trait loci for adult plant resistance to YR and connect it with durability.
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Affiliation(s)
- Stéphanie Mallard
- INRA, Agrocampus Rennes, UMR118, Amélioration des Plantes et Biotechnologies Végétales, 35650 Le Rheu, France
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14
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Manenoi A, Paull RE. Papaya fruit softening, endoxylanase gene expression, protein and activity. PHYSIOLOGIA PLANTARUM 2007; 131:470-80. [PMID: 18251885 DOI: 10.1111/j.1399-3054.2007.00967.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Papaya (Carica papaya L.) cell wall matrix polysaccharides are modified as the fruit starts to soften during ripening and an endoxylanase is expressed that may play a role in the softening process. Endoxylanase gene expression, protein amount and activity were determined in papaya cultivars that differ in softening pattern and in one cultivar where softening was modified by the ethylene receptor inhibitor 1-methylcyclopropene (1-MCP). Antibodies to the endoxylanase catalytic domain were used to determine protein accumulation. The three papaya varieties used in the study, 'Line 8', 'Sunset', and 'Line 4-16', differed in softening pattern, respiration rate, ethylene production and showed similar parallel relationships during ripening and softening in endoxylanase expression, protein level and activity. When fruit of the three papaya varieties showed the respiratory climacteric and started to soften, the level of endoxylanase gene expression increased and this increase was related to the amount of endoxylanase protein at 32 kDa and its activity. Fruit when treated at less than 10% skin yellow stage with 1-MCP showed a significant delay in the respiratory climacteric and softening, and reduced ethylene production, and when ripe was firmer and had a 'rubbery' texture. The 1-MCP-treated fruit that had the 'rubbery' texture showed suppressed endoxylanase gene expression, protein and enzymatic activity. Little or no delay occurred between endoxylanase gene expression and the appearance of activity during posttranslational processing from 65 to 32 kDa. The close relationship between endoxylanase gene expression, protein accumulation and activity in different varieties and the failure of the 1-MCP-treated fruit to fully soften, supported de novo synthesis of endoxylanase, rapid posttranslation processing and a role in papaya fruit softening.
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Affiliation(s)
- Ashariya Manenoi
- Department of Tropical Plant and Soil Sciences, University of Hawaii at Manoa, HI, USA
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15
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Van Campenhout S, Pollet A, Bourgois TM, Rombouts S, Beaugrand J, Gebruers K, De Backer E, Courtin CM, Delcour JA, Volckaert G. Unprocessed barley aleurone endo-β-1,4-xylanase X-I is an active enzyme. Biochem Biophys Res Commun 2007; 356:799-804. [PMID: 17383610 DOI: 10.1016/j.bbrc.2007.03.066] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2007] [Accepted: 03/10/2007] [Indexed: 10/23/2022]
Abstract
Endo-beta-1,4-xylanase X-I is a major hydrolase produced by the aleurone tissue of germinating barley grain. It was previously reported that this cytosolic enzyme is synthesized as an inactive precursor which is proteolytically processed to active forms upon its programmed cell death dependent release. We here demonstrate, however, that the precursor form of X-I is an active enzyme. Purified recombinant precursor X-I was characterised with respect to its molecular weight, iso-electric point and temperature and pH activity and stability. Analysis of the hydrolysis products showed that it is an endo-acting enzyme which has the striking ability to release xylose from both polymeric xylan as well as from small xylo-oligosaccharides. The implications of these findings in relation to the putative role of the N-terminal propeptide as a carbohydrate binding module and the possible consequences for the way X-I fulfils its role in the germination process, are discussed.
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Affiliation(s)
- Steven Van Campenhout
- Laboratory of Gene Technology, K.U. Leuven, Kasteelpark Arenberg 21, B-3001 Leuven, Belgium.
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16
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Mitreva-Dautova M, Roze E, Overmars H, de Graaff L, Schots A, Helder J, Goverse A, Bakker J, Smant G. A symbiont-independent endo-1,4-beta-xylanase from the plant-parasitic nematode Meloidogyne incognita. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:521-9. [PMID: 16673939 DOI: 10.1094/mpmi-19-0521] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Substituted xylan polymers constitute a major part of the hemicellulose fraction of plant cell walls, especially in monocotyledons. Endo-1,4-beta-xylanases (EC 3.2.1.8) are capable of hydrolyzing substituted xylan polymers into fragments of random size. Many herbivorous animals have evolved intimate relationships with endosymbionts to exploit their enzyme complexes for the degradation of xylan. Here, we report the first finding of a functional endo-1,4-beta-xylanase gene from an animal. The gene (Mi-xyl1) was found in the obligate plant-parasitic root-knot nematode Meloidogyne incognita, and encodes a protein that is classified as a member of glycosyl hydrolase family 5. The expression of Mi-xyl1 is localized in the subventral esophageal gland cells of the nematode. Previous studies have shown that M. incognita has the ability to degrade cellulose and pectic polysaccharides in plant cell walls independent of endosymbionts. Including our current data on Mi-xyl1, we show that the endogenous enzyme complex in root-knot nematode secretions targets essentially all major cell wall carbohydrates to facilitate a stealthy intercellular migration in the host plant.
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Affiliation(s)
- Makedonka Mitreva-Dautova
- Genome Sequencing Centre, Department of Genetics, Washington University School of Medicine, St. Louis, MO 63108, USA
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17
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Gibeaut DM, Pauly M, Bacic A, Fincher GB. Changes in cell wall polysaccharides in developing barley (Hordeum vulgare) coleoptiles. PLANTA 2005; 221:729-38. [PMID: 15824908 DOI: 10.1007/s00425-005-1481-0] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2004] [Accepted: 11/23/2004] [Indexed: 05/17/2023]
Abstract
Cell wall polysaccharides in developing barley coleoptiles were examined using acetic acid-nitric acid extraction, alditol acetate and methylation analyses and enzymatic digestion. The coleoptile cell wall from imbibed grain was rich in pectic polysaccharides (30 mol%), arabinoxylan (25 mol%), cellulose (25 mol%) and xyloglucan (6 mol%), but contained only low levels of (1-->3,1-->4)-beta-D-glucan (1 mol%). During 5 days of coleoptile growth, pectic polysaccharides decreased steadily to about 9 mol%, while (1-->3,1-->4)-beta-D-glucan increased to 10 mol%. Following the cessation of growth of the coleoptiles at about 5 days, (1-->3,1-->4)-beta-D-glucan content rapidly decreased to 1 mol%. The cellulose content of the walls remained at about 35-40 mol% throughout coleoptile growth. Similarly, arabinoxylan content remained essentially constant at 25-30 mol% during growth, although the ratio of substituted to unsubstituted 4-linked xylosyl units decreased from about 4:1 to 1:1. Xyloglucan content ranged from 6 mol% to 10 mol% and the oligosaccharide profile determined using a xyloglucan-specific endoglucanase and MALDI-TOF mass spectrometry indicated that the oligosaccharides XXGG and XXGGG were the principal components, with one and two acetyl groups, respectively, Thus, dramatic changes in wall composition were detected during the growth of barley coleoptiles, both with respect to the relative abundance of individual wall constituents and to the fine structure of the arabinoxylans.
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Affiliation(s)
- David M Gibeaut
- Australian Centre for Plant Functional Genomics, School of Agriculture and Wine, University of Adelaide, Waite Campus, Glen Osmond, SA, 5064, Australia
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18
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Sungurtas J, Swanston J, Davies H, McDougall G. Xylan-degrading enzymes and arabinoxylan solubilisation in barley cultivars of differing malting quality. J Cereal Sci 2004. [DOI: 10.1016/j.jcs.2003.11.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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19
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Gebruers K, Brijs K, Courtin CM, Fierens K, Goesaert H, Rabijns A, Raedschelders G, Robben J, Sansen S, Sørensen JF, Van Campenhout S, Delcour JA. Properties of TAXI-type endoxylanase inhibitors. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2004; 1696:213-21. [PMID: 14871662 DOI: 10.1016/j.bbapap.2003.08.013] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2003] [Accepted: 08/07/2003] [Indexed: 12/20/2022]
Abstract
Two types of proteinaceous endoxylanase inhibitors occur in different cereals, i.e. the TAXI [Triticum aestivum endoxylanase inhibitor]-type and XIP [endoxylanase inhibiting protein]-type inhibitors. The present paper focuses on the TAXI-type proteins and deals with their structural characteristics and the identification, characterisation and heterologous expression of a TAXI gene from wheat. In addition, to shed light on the mechanism by which TAXI-type endoxylanase inhibitors work, the enzyme specificity, the optimal conditions for maximal inhibition activity, the molar complexation ratio and the inhibition kinetics of the inhibitors are explained and the effect of mutations of an endoxylanase on the inhibition by TAXIs is discussed.
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Affiliation(s)
- Kurt Gebruers
- KU Leuven, Laboratory of Food Chemistry, Kasteelpark Arenberg 20, B-3001 Louvain, Belgium.
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20
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21
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Wu SSH, Suen DF, Chang HC, Huang AHC. Maize tapetum xylanase is synthesized as a precursor, processed and activated by a serine protease, and deposited on the pollen. J Biol Chem 2002; 277:49055-64. [PMID: 12368281 DOI: 10.1074/jbc.m208804200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pollen coat contains ingredients that interact with the stigma surface during sexual reproduction. In maize (Zea mays L.) pollen coat, the predominant protein is a 35-kDa endoxylanase, whose mRNA is located in the tapetum cells enclosing the maturing pollen in the anthers. This 2.0-kb mRNA was found to have an open reading frame of 1,635 nucleotides encoding a 60-kDa pre-xylanase. In developing anthers, the pre-xylanase protein appeared prior to the 35-kDa xylanase protein and enzyme activity and then peaked and declined, whereas the 35-kDa xylanase protein and activity continued to increase until anther maturation. An acid protease in the anther extract converted the inactive pre-xylanase to the active 35-kDa xylanase in vitro. The protease activity was inhibited by inhibitors of serine proteases but unaffected by inhibitors of cysteine, aspartic, or metallic proteases. Sequence analysis revealed that the 60-kDa pre-xylanase was converted to the 35-kDa xylanase with the removal of 198 and 48 residues from the N and C termini, respectively. During in vitro and in vivo conversions, no intermediates of 60-35 kDa were observed, and the 35-kDa xylanase was highly stable. The pre-xylanase was localized in the tapetum-containing anther wall, whereas the 35-kDa xylanase was found in the pollen coat. The significance of having a large non-active pre-xylanase and the mode of transfer of the xylanase to the pollen coat are discussed. A gene encoding the barley (Hordeum vulgare L.) tapetum xylanase was cloned; this gene and the gene encoding the seed aleurone-layer xylanase had strict tissue-specific expressions.
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Affiliation(s)
- Sherry S H Wu
- Department of Botany and Plant Sciences and Center for Plant Cell Biology, University of California, Riverside 92521, USA
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22
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Burton RA, Jenner H, Carrangis L, Fahy B, Fincher GB, Hylton C, Laurie DA, Parker M, Waite D, van Wegen S, Verhoeven T, Denyer K. Starch granule initiation and growth are altered in barley mutants that lack isoamylase activity. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2002; 31:97-112. [PMID: 12100486 DOI: 10.1046/j.1365-313x.2002.01339.x] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Two mutant lines of barley, Risø 17 and Notch-2, were found to accumulate phytoglycogen in the grain. Like the sugary mutants of maize and rice, these phytoglycogen-accumulating mutants of barley lack isoamylase activity in the developing endosperm. The mutants were shown to be allelic, and to have lesions in the isoamylase gene, isa1 that account for the absence of this enzyme. As well as causing a reduction in endosperm starch content, the mutations have a profound effect on the structure, number and timing of initiation of starch granules. There are no normal A-type or B-type granules in the mutants. The mutants have a greater number of starch granules per plastid than the wild-type and, particularly in Risø 17, this leads to the appearance of compound starch granules. These results suggest that, as well as suppressing phytoglycogen synthesis, isoamylase in the wild-type endosperm plays a role in determining the number, and hence the form, of starch granules.
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Affiliation(s)
- Rachel A Burton
- Department of Plant Science, University of Adelaide, Waite Campus, Glen Osmond, SA 5064, Australia
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23
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Suzuki M, Kato A, Nagata N, Komeda Y. A xylanase, AtXyn1, is predominantly expressed in vascular bundles, and four putative xylanase genes were identified in the Arabidopsis thaliana genome. PLANT & CELL PHYSIOLOGY 2002; 43:759-67. [PMID: 12154138 DOI: 10.1093/pcp/pcf088] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The cDNA clone RXF12, which encodes a xylanase (EC 3.2.1.8), was isolated from Arabidopsis thaliana. The C-terminal half of the amino acid sequence of the deduced protein, named AtXyn1, showed similarity with the catalytic domain of barley xylanase X-1. The N-terminal half of AtXyn1 also contained three regions with sequences similar to cellulose-binding domains (CBDs). A xylanase assay revealed that transgenic A. thaliana plants expressing exogenous AtXyn1 fused with enhanced green fluorescent protein (EGFP) possessed approximately twice as much xylanase activity as wild-type plants. Observation by fluorescence microscopy of transgenic A. thaliana plants expressing a fusion protein of AtXyn1 and EGFP suggested that AtXyn1 is a cell wall protein. Analysis of the localization of beta-glucuronidase (GUS) activity in transgenic A. thaliana plants containing a chimeric gene with the upstream sequence of the AtXyn1 gene and the GUS gene demonstrated that the AtXyn1 gene is predominantly expressed in vascular bundles, but not in vessel cells. These data suggest that AtXyn1 is involved in the secondary cell wall metabolism of vascular bundle cells. A database search revealed that four putative xylanase genes exist in the A. thaliana genome, besides the AtXyn1 gene. Of these, two also contain several regions with sequences similar to CBDs in their N-terminal regions. Comparison of the amino acid sequences of the five xylanases suggests a possible process for their molecular evolution.
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Affiliation(s)
- Masashi Suzuki
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, N10, W8, Kita-ku, Sapporo, 060-0810 Japan.
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24
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Lam SK, Ng TB. A xylanase from roots of sanchi ginseng (Panax notoginseng) with inhibitory effects on human immunodeficiency virus-1 reverse transcriptase. Life Sci 2002; 70:3049-58. [PMID: 12138018 DOI: 10.1016/s0024-3205(02)01557-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A xylanase with a molecular weight of 15 kDa, which is lower than those of previously reported xylanases, was isolated from the roots of the medicinal herb Panax notoginseng. The xylanase exhibits a temperature optimum of 50 degrees C and a pH optimum between 5 and 6. It inhibits HIV-1 reverse transcriptase with an IC(50) of 10 microM, but does not affect translation in a cell-free rabbit reticulocyte system when tested up to 70 microM. The enzyme is adsorbed on CM-cellulose, Affi-gel blue gel and Mono S. Previously xylanases have been isolated from seeds and not from roots, and have not been demonstrated to inhibit HIV-1 reverse transcriptase.
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Affiliation(s)
- S K Lam
- Department of Biochemistry, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
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25
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Simões-Araújo JL, Rodrigues RL, de A Gerhardt LB, Mondego JMC, Alves-Ferreira M, Rumjanek NG, Margis-Pinheiro M. Identification of differentially expressed genes by cDNA-AFLP technique during heat stress in cowpea nodules. FEBS Lett 2002; 515:44-50. [PMID: 11943192 DOI: 10.1016/s0014-5793(02)02416-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Legume nodules formed by diazotrophic microorganisms are active sites for biological nitrogen fixation (BNF). In tropical regions, a significant part of N supply for soybean, peanut and bean crops is derived from BNF, which is nevertheless often limited by high temperature stress. In contrast, cowpea nodules are very resistant to high temperatures. To understand the molecular bases of thermotolerance during BNF under heat stress, we have used cDNA-amplified fragment length polymorphism experiments to identify differentially expressed transcripts from cowpea nodules subjected to heat shock treatment. The expression profiles obtained showed approximately 600 bands, 55 up-regulated and nine corresponding to genes repressed by heat stress. Twenty transcript-derived fragments were isolated, cloned and sequenced. The Vigna unguiculata nodule and stress response transcripts present similarities to those that encode low molecular weight heat shock proteins, wound-induced proteins, disease resistance protein, and xylan endohydrolase isoenzyme, as well as different housekeeping genes. The differential expression of 15 genes was confirmed by using Northern blot or reverse Northern hybridization experiments.
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Affiliation(s)
- Jean Luiz Simões-Araújo
- Laboratório de Genética Molecular Vegetal, Departamento de Genética, Universidade Federal do Rio de Janeiro, CP 68011, CEP 21941-970, Rio de Janeiro, Brazil
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26
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Elrouby N, Bureau TE. A novel hybrid open reading frame formed by multiple cellular gene transductions by a plant long terminal repeat retroelement. J Biol Chem 2001; 276:41963-8. [PMID: 11553621 DOI: 10.1074/jbc.m105850200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The discovery that vertebrate retroviruses could transduce cellular sequences was central to cancer etiology and research. Although not well documented, transduction of cellular sequences by retroelements has been suggested to modify cellular functions. The maize Bs1 transposon was the first non-vertebrate retroelement reported to have transduced a portion of a cellular gene (c-pma). We show that Bs1 has, in addition, transduced portions of at least two more maize cellular genes, namely for 1,3-beta-glucanase (c-bg) and 1,4-beta-xylan endohydrolase (c-xe). We also show that Bs1 has maintained a truncated gag domain with similarity to the magellan gypsy-like long terminal repeat retrotransposon and a region that may correspond to an env-like domain. Our findings suggest that, like oncogenic retroviruses, the three transduced gene fragments and the Bs1 gag domain encode a fusion protein that has the potential to be expressed. We suggest that transduction by retroelements may facilitate the formation of novel hybrid genes in plants.
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Affiliation(s)
- N Elrouby
- Department of Biology, McGill University, Montreal, Quebec H3A 1B1, Canada
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27
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Caspers MP, Lok F, Sinjorgo KM, van Zeijl MJ, Nielsen KA, Cameron-Mills V. Synthesis, processing and export of cytoplasmic endo-beta-1,4-xylanase from barley aleurone during germination. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2001; 26:191-204. [PMID: 11389760 DOI: 10.1046/j.0960-7412.2001.01019.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We have identified the major endo-beta-1,4-xylanase (XYN-1) in the aleurone of germinating barley grain, and show that it is expressed as a precursor of Mr 61 500 with both N- and C-terminal propeptides. XYN-1 is synthesized as an inactive enzyme in the cytoplasm, and only becomes active at a late stage of germination when the aleurone ceases to secrete hydrolases. A series of processing steps, mediated in part by aleurone cysteine endoproteases, yields a mature active enzyme of Mr 34 000. Processing and extracellular release of the mature enzyme coincide with the programmed cell death (PCD)-regulated disintegration of aleurone cells. We discuss the significance of delayed aleurone cell-wall degradation by endoxylanases in relation to the secretory capacity of the aleurone, and propose a novel role for aleurone PCD in facilitating the export of hydrolases.
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Affiliation(s)
- M P Caspers
- Department of Applied Plant Sciences, TNO Nutrition and Food Research Institute, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands, and; Carlsberg Research Laboratory, Gamle Carlsberg Vej 10, DK-2500 Copenhagen, Denmark
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28
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Ferré H, Broberg A, Duus JO, Thomsen KK. A novel type of arabinoxylan arabinofuranohydrolase isolated from germinated barley analysis of substrate preference and specificity by nano-probe NMR. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:6633-41. [PMID: 11054116 DOI: 10.1046/j.1432-1327.2000.01758.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
An arabinoxylan arabinofuranohydrolase was isolated from barley malt. The enzyme preparation, Ara 1, contained two polypeptides with apparent molecular masses of approximately 60 and approximately 66 kDa, a pI of 4.55 and almost identical N-terminal amino-acid sequences. With p-nitrophenyl alpha-L-arabinofuranoside (pNPA) as substrate, Ara 1 exhibited a Km of 0.5 mM and a Vmax of 6.7 micromol. min-1.(mg of protein)-1. Maximum activity was displayed at pH 4.2 and 60 degrees C, and, under these conditions, the half-life of the enzyme was 8 min. The Ara 1 preparation showed no activity against p-nitrophenyl alpha-L-arabinopyranoside or p-nitrophenyl beta-D-xylopyranoside. Substrate preference and specificity were investigated using pure oligosaccharides and analysis by TLC and nano-probe NMR. Ara 1 released arabinose from high-molecular-mass arabinoxylan and arabinoxylan-derived oligosaccharides but was inactive against linear or branched-chain arabinan. Arabinose was readily released from both singly and doubly substituted xylo-oligosaccharides. Whereas single 2-O-linked and 3-O-linked arabinose substituents on non-reducing terminal xylose were released at similar rates, there was a clear preference for 2-O-linked arabinose on internal xylose residues. When Ara 1 acted on oligosaccharides with doubly substituted, non-reducing terminal xylose, the 3-O-linked arabinose group was preferred as the initial point of attack. Oligosaccharides with doubly substituted internal xylose were poor substrates and no preference could be determined. The enzyme described here is the first reported arabinoxylan arabinofuranohydrolase which is able to release arabinose from both singly and doubly substituted xylose, and it hydrolyses p-nitrophenyl alpha-L-arabinofuranoside at a rate similar to that observed for oligosaccharide substrates.
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Affiliation(s)
- H Ferré
- Department of Physiology and Department of Chemistry, Carlsberg Laboratory, Valby, Denmark
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29
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Burton RA, Zhang XQ, Hrmova M, Fincher GB. A single limit dextrinase gene is expressed both in the developing endosperm and in germinated grains of barley. PLANT PHYSIOLOGY 1999; 119:859-71. [PMID: 10069825 PMCID: PMC32101 DOI: 10.1104/pp.119.3.859] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/1998] [Accepted: 12/02/1998] [Indexed: 05/17/2023]
Abstract
The single gene encoding limit dextrinase (pullulan 6-glucanohydrolase; EC 3.2.1.41) in barley (Hordeum vulgare) has 26 introns that range in size from 93 to 822 base pairs. The mature polypeptide encoded by the gene has 884 amino acid residues and a calculated molecular mass of 97,417 D. Limit dextrinase mRNA is abundant in gibberellic acid-treated aleurone layers and in germinated grain. Gibberellic acid response elements were found in the promoter region of the gene. These observations suggest that the enzyme participates in starch hydrolysis during endosperm mobilization in germinated grain. The mRNA encoding the enzyme is present at lower levels in the developing endosperm of immature grain, a location consistent with a role for limit dextrinase in starch synthesis. Enzyme activity was also detected in developing grain. The limit dextrinase has a presequence typical of transit peptides that target nascent polypeptides to amyloplasts, but this would not be expected to direct secretion of the mature enzyme from aleurone cells in germinated grain. It remains to be discovered how the enzyme is released from the aleurone and whether another enzyme, possibly of the isoamylase group, might be equally important for starch hydrolysis in germinated grain.
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Affiliation(s)
- R A Burton
- Department of Plant Science, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia
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30
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Hrmova M, Banik M, Harvey AJ, Garrett TP, Varghese JN, Høj PB, Fincher GB. Polysaccharide hydrolases in germinated barley and their role in the depolymerization of plant and fungal cell walls. Int J Biol Macromol 1997; 21:67-72. [PMID: 9283018 DOI: 10.1016/s0141-8130(97)00043-3] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Cell wall degradation is an important event during endosperm mobilization in the germinated barley grain. A battery of polysaccharide and oligosaccharide hydrolases is required for the complete depolymerization of the arabinoxylans and (1 --> 3,1 --> 4)-beta-glucans which comprise in excess of 90% by weight of these walls. The (1 --> 3,1 --> 4)-beta-glucan endohydrolases release oligosaccharides from their substrate and are probably of central importance for the initial solubilization of the (1 --> 3,1 --> 4)-beta-glucans, but beta-glucan exohydrolases and beta-glucosidases may be important additional enzymes for the conversion of released oligosaccharides to glucose. The latter enzymes have recently been purified from germinated barley and characterized. There is an increasing body of evidence to support the notion that the (1 --> 3,1 --> 4)-beta-glucan endohydrolases from germinated barley evolved from the pathogenesis-related (1 --> 3)-beta-glucanases which are widely distributed in plants and which hydrolyse polysaccharides that are abundant in fungal cell walls. Arabinoxylan depolymerization is also mediated by a family of enzymes, but these are less well characterized. (1 --> 4)-beta-Xylan endohydrolases have been purified and the corresponding cDNAs and genes isolated. While the presence of (1 --> 4)-beta-xylan exohydrolases and alpha-L-arabinofuranosidases has been reported many times, the enzymes have not yet been studied in detail. Here, recent advances in the enzymology and physiology of cell wall degradation in the germinated barley grain are briefly reviewed.
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Affiliation(s)
- M Hrmova
- Department of Plant Science, University of Adelaide, Waite Campus, Glen Osmond, SA, Australia
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