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Akagi T, Ikegami A, Yonemori K. DkMyb2 wound-induced transcription factor of persimmon (Diospyros kaki Thunb.), contributes to proanthocyanidin regulation. PLANTA 2010; 232:1045-59. [PMID: 20690029 DOI: 10.1007/s00425-010-1241-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Accepted: 07/23/2010] [Indexed: 05/22/2023]
Abstract
Proanthocyanidins (PAs) are secondary metabolites that contribute to the protection of a plant against biotic and abiotic stresses. Persimmon (Diospyros kaki) accumulates abundant PAs in each plant organ, and some potential Myb-like transcription factors (Myb-TFs) involved in the production of PAs have been isolated. In this study, we aimed to molecularly characterize one of them, DkMyb2, which was placed in a subclade including a PA regulator of Arabidopsis (Arabidopsis thaliana), TRANSPARENT TESTA2 (TT2), and was co-induced with PA pathway genes after wound stress. Ectopic DkMyb2 overexpression caused significant up-regulation of PA pathway genes in transgenic persimmon calluses and significant accumulation of PA, and increased mean degree of polymerization of PAs in transgenic kiwifruit calluses. Analysis of the DNA-binding ability of DkMyb2 by electrophoretic mobility shift assays showed that DkMyb2 directly binds to the AC-rich cis-motifs known as AC elements in the promoters of the two PA pathway genes in persimmon, DkANR, and DkLAR. Furthermore, a transient reporter assay using a dual-luciferase system demonstrated direct transcriptional activation of DkANR and DkLAR by DkMyb2. We also discuss subfunctionalization of two PA regulators in persimmon, DkMyb2 and DkMyb4, as well as PA regulators in other plant species from the viewpoint of their ability to bind to cis-motifs and their functions in transcriptional activation. Our results provide insight into the multiple regulatory mechanisms that control PA metabolism by Myb-TFs in persimmon.
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Affiliation(s)
- Takashi Akagi
- Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, Japan
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152
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Bedon F, Bomal C, Caron S, Levasseur C, Boyle B, Mansfield SD, Schmidt A, Gershenzon J, Grima-Pettenati J, Séguin A, MacKay J. Subgroup 4 R2R3-MYBs in conifer trees: gene family expansion and contribution to the isoprenoid- and flavonoid-oriented responses. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:3847-64. [PMID: 20732878 PMCID: PMC2935864 DOI: 10.1093/jxb/erq196] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Revised: 06/09/2010] [Accepted: 06/10/2010] [Indexed: 05/18/2023]
Abstract
Transcription factors play a fundamental role in plants by orchestrating temporal and spatial gene expression in response to environmental stimuli. Several R2R3-MYB genes of the Arabidopsis subgroup 4 (Sg4) share a C-terminal EAR motif signature recently linked to stress response in angiosperm plants. It is reported here that nearly all Sg4 MYB genes in the conifer trees Picea glauca (white spruce) and Pinus taeda (loblolly pine) form a monophyletic clade (Sg4C) that expanded following the split of gymnosperm and angiosperm lineages. Deeper sequencing in P. glauca identified 10 distinct Sg4C sequences, indicating over-representation of Sg4 sequences compared with angiosperms such as Arabidopsis, Oryza, Vitis, and Populus. The Sg4C MYBs share the EAR motif core. Many of them had stress-responsive transcript profiles after wounding, jasmonic acid (JA) treatment, or exposure to cold in P. glauca and P. taeda, with MYB14 transcripts accumulating most strongly and rapidly. Functional characterization was initiated by expressing the P. taeda MYB14 (PtMYB14) gene in transgenic P. glauca plantlets with a tissue-preferential promoter (cinnamyl alcohol dehydrogenase) and a ubiquitous gene promoter (ubiquitin). Histological, metabolite, and transcript (microarray and targeted quantitative real-time PCR) analyses of PtMYB14 transgenics, coupled with mechanical wounding and JA application experiments on wild-type plantlets, allowed identification of PtMYB14 as a putative regulator of an isoprenoid-oriented response that leads to the accumulation of sesquiterpene in conifers. Data further suggested that PtMYB14 may contribute to a broad defence response implicating flavonoids. This study also addresses the potential involvement of closely related Sg4C sequences in stress responses and plant evolution.
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Affiliation(s)
- Frank Bedon
- Centre d’Étude de la Forêt, Université Laval, Québec (QC), G1V A06, Canada
- UMR UPS/CNRS 5546, Pôle de Biotechnologies Végétales, 24 chemin de Borde Rouge, BP42617, Auzeville Tolosane, 31326 Castanet Tolosan, France
| | - Claude Bomal
- Centre d’Étude de la Forêt, Université Laval, Québec (QC), G1V A06, Canada
| | - Sébastien Caron
- Centre d’Étude de la Forêt, Université Laval, Québec (QC), G1V A06, Canada
| | - Caroline Levasseur
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, Québec (QC), G1V A06, Canada
| | - Brian Boyle
- Centre d’Étude de la Forêt, Université Laval, Québec (QC), G1V A06, Canada
| | - Shawn D. Mansfield
- Canada Research Chair in Wood and Fibre Quality, Department of Wood Science, University of British Columbia, 4030-2424 Main Mall, Vancouver (BC), V6T 1Z4, Canada
| | - Axel Schmidt
- Max Planck Institute for Chemical Ecology, Hans-Knoell-Str.8, Beutenberg-Campus, D-07745 Jena, Germany
| | - Jonathan Gershenzon
- Max Planck Institute for Chemical Ecology, Hans-Knoell-Str.8, Beutenberg-Campus, D-07745 Jena, Germany
| | - Jacqueline Grima-Pettenati
- UMR UPS/CNRS 5546, Pôle de Biotechnologies Végétales, 24 chemin de Borde Rouge, BP42617, Auzeville Tolosane, 31326 Castanet Tolosan, France
| | - Armand Séguin
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, Québec (QC), G1V A06, Canada
| | - John MacKay
- Centre d’Étude de la Forêt, Université Laval, Québec (QC), G1V A06, Canada
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153
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Designing Biomass Crops with Improved Calorific Content and Attributes for Burning: a UK Perspective. ACTA ACUST UNITED AC 2010. [DOI: 10.1007/978-3-642-13440-1_2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
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154
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155
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Syringyl lignin biosynthesis is directly regulated by a secondary cell wall master switch. Proc Natl Acad Sci U S A 2010; 107:14496-501. [PMID: 20660755 DOI: 10.1073/pnas.1009170107] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Lignin is a major component of plant secondary cell walls and is derived from p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) monolignols. Among higher plants, S lignin is generally considered to be restricted to angiosperms, which contain the S lignin-specific cytochrome P450-dependent monooxygenase, ferulic acid/coniferaldehyde/coniferyl alcohol 5-hydoxylase (F5H). The transcription factor MYB58 directly regulates expression of monolignol pathway genes except for F5H. Here we show that F5H expression is directly regulated by the secondary cell wall master switch NST1/SND1, which is known to regulate expression of MYB58. Deletion of NST1 expression in Medicago truncatula leads to a loss of S lignin associated with a more than 25-fold reduction of F5H expression but only around a 2-fold reduction in expression of other lignin pathway genes. A detailed phylogenetic analysis showed that gymnosperms lack both F5H and orthologs of NST1/SND1. We propose that both F5H and NST1 appeared at a similar time after the divergence of angiosperms and gymnosperms, with F5H possibly originating as a component of a defense mechanism that was recruited to cell wall biosynthesis through the evolution of NST1-binding elements in its promoter.
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156
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Vanholme R, Demedts B, Morreel K, Ralph J, Boerjan W. Lignin biosynthesis and structure. PLANT PHYSIOLOGY 2010; 153:895-905. [PMID: 20472751 PMCID: PMC2899938 DOI: 10.1104/pp.110.155119] [Citation(s) in RCA: 1135] [Impact Index Per Article: 81.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2010] [Accepted: 05/12/2010] [Indexed: 05/02/2023]
Affiliation(s)
| | | | | | | | - Wout Boerjan
- Department of Plant Systems Biology, VIB, 9052 Ghent, Belgium (R.V., B.D., K.M., W.B.); Department of Plant Biotechnology and Genetics, Ghent University, 9052 Ghent, Belgium (R.V., B.D., K.M., W.B.); Department of Biochemistry and Great Lakes Bioenergy Research Center, University of Wisconsin, Madison, Wisconsin 53706 (J.R.)
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157
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Rahantamalala A, Rech P, Martinez Y, Chaubet-Gigot N, Grima-Pettenati J, Pacquit V. Coordinated transcriptional regulation of two key genes in the lignin branch pathway--CAD and CCR--is mediated through MYB- binding sites. BMC PLANT BIOLOGY 2010; 10:130. [PMID: 20584286 PMCID: PMC3017776 DOI: 10.1186/1471-2229-10-130] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2010] [Accepted: 06/28/2010] [Indexed: 05/02/2023]
Abstract
BACKGROUND Cinnamoyl CoA reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD) catalyze the final steps in the biosynthesis of monolignols, the monomeric units of the phenolic lignin polymers which confer rigidity, imperviousness and resistance to biodegradation to cell walls. We have previously shown that the Eucalyptus gunnii CCR and CAD2 promoters direct similar expression patterns in vascular tissues suggesting that monolignol production is controlled, at least in part, by the coordinated transcriptional regulation of these two genes. Although consensus motifs for MYB transcription factors occur in most gene promoters of the whole phenylpropanoid pathway, functional evidence for their contribution to promoter activity has only been demonstrated for a few of them. Here, in the lignin-specific branch, we studied the functional role of MYB elements as well as other cis-elements identified in the regulatory regions of EgCAD2 and EgCCR promoters, in the transcriptional activity of these gene promoters. RESULTS By using promoter deletion analysis and in vivo footprinting, we identified an 80 bp regulatory region in the Eucalyptus gunnii EgCAD2 promoter that contains two MYB elements, each arranged in a distinct module with newly identified cis-elements. A directed mutagenesis approach was used to introduce block mutations in all putative cis-elements of the EgCAD2 promoter and in those of the 50 bp regulatory region previously delineated in the EgCCR promoter. We showed that the conserved MYB elements in EgCAD2 and EgCCR promoters are crucial both for the formation of DNA-protein complexes in EMSA experiments and for the transcriptional activation of EgCAD2 and EgCCR promoters in vascular tissues in planta. In addition, a new regulatory cis-element that modulates the balance between two DNA-protein complexes in vitro was found to be important for EgCAD2 expression in the cambial zone. CONCLUSIONS Our assignment of functional roles to the identified cis-elements clearly demonstrates the importance of MYB cis-elements in the transcriptional regulation of two genes of the lignin-specific pathway and support the hypothesis that MYB elements serve as a common means for the coordinated regulation of genes in the entire lignin biosynthetic pathway.
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Affiliation(s)
- Anjanirina Rahantamalala
- Université de Toulouse; UPS; UMR 5546, Surfaces Cellulaires et Signalisation chez les Végétaux; BP 42617, F-31326, Castanet-Tolosan, France
- CNRS; UMR 5546; BP 42617, F-31326, Castanet-Tolosan, France
| | - Philippe Rech
- Université de Toulouse; UPS; UMR 5546, Surfaces Cellulaires et Signalisation chez les Végétaux; BP 42617, F-31326, Castanet-Tolosan, France
- CNRS; UMR 5546; BP 42617, F-31326, Castanet-Tolosan, France
- Université Pierre et Marie Curie Paris 6, EAC7180 CNRS, UR5, Mécanismes de la Régénération des Plantes, F-75252 Paris cedex 05, France
| | - Yves Martinez
- Université de Toulouse; UPS; UMR 5546, Surfaces Cellulaires et Signalisation chez les Végétaux; BP 42617, F-31326, Castanet-Tolosan, France
- CNRS; UMR 5546; BP 42617, F-31326, Castanet-Tolosan, France
| | - Nicole Chaubet-Gigot
- Université de Toulouse; UPS; UMR 5546, Surfaces Cellulaires et Signalisation chez les Végétaux; BP 42617, F-31326, Castanet-Tolosan, France
- CNRS; UMR 5546; BP 42617, F-31326, Castanet-Tolosan, France
| | - Jacqueline Grima-Pettenati
- Université de Toulouse; UPS; UMR 5546, Surfaces Cellulaires et Signalisation chez les Végétaux; BP 42617, F-31326, Castanet-Tolosan, France
- CNRS; UMR 5546; BP 42617, F-31326, Castanet-Tolosan, France
| | - Valérie Pacquit
- Université de Toulouse; UPS; UMR 5546, Surfaces Cellulaires et Signalisation chez les Végétaux; BP 42617, F-31326, Castanet-Tolosan, France
- CNRS; UMR 5546; BP 42617, F-31326, Castanet-Tolosan, France
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158
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McCarthy RL, Zhong R, Fowler S, Lyskowski D, Piyasena H, Carleton K, Spicer C, Ye ZH. The poplar MYB transcription factors, PtrMYB3 and PtrMYB20, are involved in the regulation of secondary wall biosynthesis. PLANT & CELL PHYSIOLOGY 2010; 51:1084-90. [PMID: 20427511 DOI: 10.1093/pcp/pcq064] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Dicot wood is mainly composed of cellulose, xylan and lignin, and its formation requires the coordinated regulation of their biosynthesis. In this report, we demonstrate that the poplar wood-associated MYB transcriptional activators, PtrMYB3 and PtrMYB20, activate the biosynthetic pathways of cellulose, xylan and lignin when overexpressed in Arabidopsis and they are also able to activate the promoter activities of poplar wood biosynthetic genes. We also show that PtrMYB3 and PtrMYB20 are functional orthologs of Arabidopsis MYB46 and MYB83, and their expression is directly activated by poplar PtrWND2, suggesting their involvement in the regulation of wood formation in poplar.
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Affiliation(s)
- Ryan L McCarthy
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
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159
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Zhong R, Ye ZH. The poplar PtrWNDs are transcriptional activators of secondary cell wall biosynthesis. PLANT SIGNALING & BEHAVIOR 2010; 5:469-72. [PMID: 20383071 PMCID: PMC2958599 DOI: 10.4161/psb.5.4.11400] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Accepted: 02/02/2010] [Indexed: 05/17/2023]
Abstract
Secondary cell walls, consisting of cellulose, hemicelluloses and lignin, make up the bulk of wood biomass. It is therefore expected that dissection of the molecular mechanisms underlying secondary wall biosynthesis and its regulation will be instrumental to unravel the process of wood formation in tree species. Wood formation requires the coordinated activation of genes in the secondary wall biosynthetic program that is essential for the biosynthesis and assembly of wood components. It has recently been discovered that a group of poplar (Populus trichocarpa) wood-associated NAC domain transcription factors, PtrWNDs, which are functional orthologs of the Arabidopsis SND1, are capable of turning on the entire secondary wall biosynthetic program when expressed in Arabidopsis. In addition, two of the PtrWNDs were found to be able to activate the promoters of poplar wood biosynthetic genes and a number of other poplar wood-associated transcription factors. Further testing reveals that the promoters of these poplar wood-associated transcription factors are also activated by other PtrWNDs. It is therefore proposed that PtrWNDs are master transcriptional switches regulating a cascade of downstream transcription factors and thereby mediate the coordinated activation of wood biosynthetic genes during wood formation.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, GA, USA
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160
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Winzell A, Aspeborg H, Wang Y, Ezcurra I. Conserved CA-rich motifs in gene promoters of Pt×tMYB021-responsive secondary cell wall carbohydrate-active enzymes in Populus. Biochem Biophys Res Commun 2010; 394:848-53. [DOI: 10.1016/j.bbrc.2010.03.101] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Accepted: 03/17/2010] [Indexed: 11/30/2022]
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161
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Dharmawardhana P, Brunner AM, Strauss SH. Genome-wide transcriptome analysis of the transition from primary to secondary stem development in Populus trichocarpa. BMC Genomics 2010; 11:150. [PMID: 20199690 PMCID: PMC2846914 DOI: 10.1186/1471-2164-11-150] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Accepted: 03/04/2010] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND With its genome sequence and other experimental attributes, Populus trichocarpa has become the model species for genomic studies of wood development. Wood is derived from secondary growth of tree stems, and begins with the development of a ring of vascular cambium in the young developing stem. The terminal region of the developing shoot provides a steep developmental gradient from primary to secondary growth that facilitates identification of genes that play specialized functions during each of these phases of growth. RESULTS Using a genomic microarray representing the majority of the transcriptome, we profiled gene expression in stem segments that spanned primary to secondary growth. We found 3,016 genes that were differentially expressed during stem development (Q-value = 0.05; >2-fold expression variation), and 15% of these genes encode proteins with no significant identities to known genes. We identified all gene family members putatively involved in secondary growth for carbohydrate active enzymes, tubulins, actins, actin depolymerizing factors, fasciclin-like AGPs, and vascular development-associated transcription factors. Almost 70% of expressed transcription factors were upregulated during the transition to secondary growth. The primary shoot elongation region of the stem contained specific carbohydrate active enzyme and expansin family members that are likely to function in primary cell wall synthesis and modification. Genes involved in plant defense and protective functions were also dominant in the primary growth region. CONCLUSION Our results describe the global patterns of gene expression that occur during the transition from primary to secondary stem growth. We were able to identify three major patterns of gene expression and over-represented gene ontology categories during stem development. The new regulatory factors and cell wall biogenesis genes that we identified provide candidate genes for further functional characterization, as well as new tools for molecular breeding and biotechnology aimed at improvement of tree growth rate, crown form, and wood quality.
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Affiliation(s)
- Palitha Dharmawardhana
- Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR, 97331-5752, USA
| | - Amy M Brunner
- Department of Forest Resources and Environmental Conservation, Virginia Tech, Blacksburg, VA, 24061-0324, USA
| | - Steven H Strauss
- Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR, 97331-5752, USA
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162
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Du J, Groover A. Transcriptional regulation of secondary growth and wood formation. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2010; 52:17-27. [PMID: 20074137 DOI: 10.1111/j.1744-7909.2010.00901.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Secondary growth and wood formation are products of the vascular cambium, a lateral meristem. Although the mechanisms have only recently begun to be uncovered, transcriptional regulation appears increasingly central to the regulation of secondary growth. The importance of transcriptional regulation is illustrated by the correlation of expression of specific classes of genes with related biological processes occurring at specific stages of secondary growth, including cell division, cell expansion, and cell differentiation. At the same time, transcription factors have been characterized that affect specific aspects of secondary growth, including regulation of the cambium and differentiation of cambial daughter cells. In the present review, we summarize evidence pointing to transcription as a major mechanism for regulation of secondary growth, and outline future approaches for comprehensively describing transcriptional networks underlying secondary growth.
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Affiliation(s)
- Juan Du
- Institute of Forest Genetics, US Forest Service, Davis, California 95618, USA
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163
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Du J, Mansfield SD, Groover AT. The Populus homeobox gene ARBORKNOX2 regulates cell differentiation during secondary growth. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2009; 60:1000-14. [PMID: 19737362 DOI: 10.1111/j.1365-313x.2009.04017.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The stem cells of the vascular cambium divide to produce daughter cells, which in turn divide before undergoing differentiation during the radial growth of woody stems. The genetic regulation of these developmental events is poorly understood, however. We report here the cloning and functional characterization of a Populus class-I KNOX homeobox gene, ARBORKNOX2 (ARK2), which we show influences terminal cell differentiation and cell wall properties during secondary growth. In the early stages of secondary growth, ARK2 is expressed broadly in the cambial zone and in terminally differentiating cell types, before becoming progressively restricted to the cambium. ARK2 overexpression and synthetic miRNA-suppression transgenics reveal positive correlations between ARK2 expression level and the timing of cambium formation, the width of the cambial zone and inhibition of cambial daughter cell differentiation. These phenotypes in turn correlate with changes in the expression of genes affecting transcription, cell division, auxin and cell wall synthesis. Notably, wood properties associated with secondary cell wall synthesis are negatively associated with ARK2 expression, including lignin and cellulose content. Together, our results suggest that ARK2 functions primarily to regulate a complex suite of genes that together influence cell differentiation during secondary growth. We propose that ARK2 may represent a co-evolved transcriptional module that influences complex, adaptive wood properties.
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Affiliation(s)
- Juan Du
- Institute of Forest Genetics, Pacific Southwest Research Station, US Forest Service, Davis, CA 95618, USA
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164
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Hinchee M, Rottmann W, Mullinax L, Zhang C, Chang S, Cunningham M, Pearson L, Nehra N. Short-rotation woody crops for bioenergy and biofuels applications. IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY. PLANT : JOURNAL OF THE TISSUE CULTURE ASSOCIATION 2009; 45:619-629. [PMID: 19936031 PMCID: PMC2778772 DOI: 10.1007/s11627-009-9235-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2009] [Accepted: 07/24/2009] [Indexed: 05/16/2023]
Abstract
Purpose-grown trees will be part of the bioenergy solution in the United States, especially in the Southeast where plantation forestry is prevalent and economically important. Trees provide a "living biomass inventory" with existing end-use markets and associated infrastructure, unlike other biomass species such as perennial grasses. The economic feasibility of utilizing tree biomass is improved by increasing productivity through alternative silvicultural systems, improved breeding and biotechnology. Traditional breeding and selection, as well as the introduction of genes for improved growth and stress tolerance, have enabled high growth rates and improved site adaptability in trees grown for industrial applications. An example is the biotechnology-aided improvement of a highly productive tropical Eucalyptus hybrid, Eucalyptus grandis x Eucalyptus urophylla. This tree has acquired freeze tolerance by the introduction of a plant transcription factor that up-regulates the cold-response pathways and makes possible commercial plantings in the Southeastern United States. Transgenic trees with reduced lignin, modified lignin, or increased cellulose and hemicellulose will improve the efficiency of feedstock conversion into biofuels. Reduced lignin trees have been shown to improve efficiency in the pre-treatment step utilized in fermentation systems for biofuels production from lignocellulosics. For systems in which thermochemical or gasification approaches are utilized, increased density will be an important trait, while increased lignin might be a desired trait for direct firing or co-firing of wood for energy. Trees developed through biotechnology, like all transgenic plants, need to go through the regulatory process, which involves biosafety and risk assessment analyses prior to commercialization.
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Affiliation(s)
- Maud Hinchee
- ArborGen, LLC, P.O. Box 840001, Summerville, SC 29484 USA
| | | | | | | | - Shujun Chang
- ArborGen, LLC, P.O. Box 840001, Summerville, SC 29484 USA
| | | | - Leslie Pearson
- ArborGen, LLC, P.O. Box 840001, Summerville, SC 29484 USA
| | - Narender Nehra
- ArborGen, LLC, P.O. Box 840001, Summerville, SC 29484 USA
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165
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Ko JH, Kim WC, Han KH. Ectopic expression of MYB46 identifies transcriptional regulatory genes involved in secondary wall biosynthesis in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2009; 60:649-65. [PMID: 19674407 DOI: 10.1111/j.1365-313x.2009.03989.x] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
MYB46 functions as a transcriptional switch that turns on the genes necessary for secondary wall biosynthesis. Elucidating the transcriptional regulatory network immediately downstream of MYB46 is crucial to our understanding of the molecular and biochemical processes involved in the biosynthesis and deposition of secondary walls in plants. To gain insights into MYB46-mediated transcriptional regulation, we first established an inducible secondary wall thickening system in Arabidopsis by expressing MYB46 under the control of dexamethasone-inducible promoter. Then, we used an ATH1 GeneChip microarray and Illumina digital gene expression system to obtain a series of transcriptome profiles with regard to the induction of secondary wall development. These analyses allowed us to identify a group of transcription factors whose expression coincided with or preceded the induction of secondary wall biosynthetic genes. A transient transcriptional activation assay was used to confirm the hierarchical relationships among the transcription factors in the network. The in vivo assay showed that MYB46 transcriptionally activates downstream target transcription factors, three of which (AtC3H14, MYB52 and MYB63) were shown to be able to activate secondary wall biosynthesis genes. AtC3H14 activated the transcription of all of the secondary wall biosynthesis genes tested, suggesting that AtC3H14 may be another master regulator of secondary wall biosynthesis. The transcription factors identified here may include direct activators of secondary wall biosynthesis genes. The present study discovered novel hierarchical relationships among the transcription factors involved in the transcriptional regulation of secondary wall biosynthesis, and generated several testable hypotheses.
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Affiliation(s)
- Jae-Heung Ko
- Department of Forestry, Michigan State University, East Lansing, MI 48824-1222, USA
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166
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McCarthy RL, Zhong R, Ye ZH. MYB83 is a direct target of SND1 and acts redundantly with MYB46 in the regulation of secondary cell wall biosynthesis in Arabidopsis. PLANT & CELL PHYSIOLOGY 2009; 50:1950-64. [PMID: 19808805 DOI: 10.1093/pcp/pcp139] [Citation(s) in RCA: 314] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
It has been proposed that the transcriptional regulation of secondary wall biosynthesis in Arabidopsis is controlled by a transcriptional network mediated by SND1 and its close homologs. Uncovering all the transcription factors and deciphering their interrelationships in the network are essential for our understanding of the molecular mechanisms underlying the transcriptional regulation of biosynthesis of secondary walls, the major constituent of wood and fibers. Here, we present functional evidence that the MYB83 transcription factor is another molecular switch in the SND1-mediated transcriptional network regulating secondary wall biosynthesis. MYB83 is specifically expressed in fibers and vessels where secondary wall thickening occurs. Its expression is directly activated by SND1 and its close homologs, including NST1, NST2, VND6 and VND7, indicating that MYB83 is their direct target. MYB83 overexpression is able to activate a number of the biosynthetic genes of cellulose, xylan and lignin and concomitantly induce ectopic secondary wall deposition. In addition, its overexpression upregulates the expression of several transcription factors involved in regulation of secondary wall biosynthesis. Dominant repression of MYB83 functions or simultaneous RNAi inhibition of MYB83 and MYB46 results in a reduction in secondary wall thickening in fibers and vessels and a deformation of vessels. Furthermore, double T-DNA knockout mutations of MYB83 and MYB46 cause a lack of secondary walls in vessels and an arrest in plant growth. Together, these results demonstrate that MYB83 and MYB46, both of which are SND1 direct targets, function redundantly in the transcriptional regulatory cascade leading to secondary wall formation in fibers and vessels.
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Affiliation(s)
- Ryan L McCarthy
- Department of Plant Biology, University of Georgia, 2502 Miller Plant Sciences, Athens, GA 30602, USA
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167
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Zhong R, Ye ZH. Transcriptional regulation of lignin biosynthesis. PLANT SIGNALING & BEHAVIOR 2009; 4:1028-34. [PMID: 19838072 PMCID: PMC2819510 DOI: 10.4161/psb.4.11.9875] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Accepted: 08/19/2009] [Indexed: 05/17/2023]
Abstract
Lignin is the second most abundant plant biopolymer mainly present in the secondary walls of tracheary elements and fibers in wood. Understanding how lignin is biosynthesized has long been an interest to plant biologists and will have a significant impact on tree biotechnology. Lignin is polymerized from monolignols that are synthesized through the lignin biosynthetic pathway. To make lignin, all the genes in the lignin biosynthetic pathway need to be coordinately turned on. It has been shown that a common cis-element, namely the AC element, is present in the majority of the lignin biosynthetic genes and required for their expression in lignifying cells. Important progress has been made in the identification of transcription factors that bind to the AC elements and are potentially involved in the coordinated regulation of lignin biosynthesis. The Arabidopsis MYB58 and MYB63 as well as their poplar ortholog PtrMYB28 are transcriptional activators of the lignin biosynthetic pathway, whereas the eucalyptus EgMYB2 and pine PtMYB4 transcription factors are likely Arabidopsis MYB46 orthologs involved in the regulation of the entire secondary wall biosynthetic program. It was found that the transcriptional regulation of lignin biosynthesis is under the control of the same transcriptional network regulating the biosynthesis of other secondary wall components, including cellulose and xylan. The identification of transcription factors directly activating lignin biosynthetic genes provides unprecedented tools to potentially manipulate the amount of lignin in wood and other plant products based on our needs.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, GA, USA
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168
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Osakabe Y, Osakabe K, Chiang VL. Characterization of the tissue-specific expression of phenylalanine ammonia-lyase gene promoter from loblolly pine (Pinus taeda) in Nicotiana tabacum. PLANT CELL REPORTS 2009; 28:1309-17. [PMID: 19636564 DOI: 10.1007/s00299-009-0707-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2008] [Revised: 03/18/2009] [Accepted: 04/20/2009] [Indexed: 05/28/2023]
Abstract
We isolated the 5' flanking region of a gene for phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) from Pinus taeda, PtaPAL. To investigate the tissue-specific expression of the PtaPAL promoter, histochemical assay of GUS activity was performed using the transgenic tobacco expressing the PtaPAL promoter-GUS. The region of -897 to -420 in PtaPAL promoter showed high activities in the secondary xylem and response to bending stress. To characterize the cis-regulatory functions of the promoters for enzymes in phenylpropanoid biosynthesis, we examined the activity of chimeric promoters of PtaPAL and a 4-coumarate CoA ligase, Pta4CL alpha. The chimeric promoter showed similar activity as the Pta4CL alpha promoter. Electrophoretic mobility shift assays implicated -897 to -674 of PtaPAL promoter containing cis-elements of the expression in xylem of Pinus taeda. The results suggested that AC elements of PtaPAL have multiple functions in the expression under the various developmental stages and stress conditions in the transgenic tobacco.
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Affiliation(s)
- Yuriko Osakabe
- Plant Biotechnology Research Center, School of Forestry and Wood Products, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA.
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169
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Gutiérrez J, López Núñez-Flores MJ, Gómez-Ros LV, Novo Uzal E, Esteban Carrasco A, Díaz J, Sottomayor M, Cuello J, Ros Barceló A. Hormonal regulation of the basic peroxidase isoenzyme from Zinnia elegans. PLANTA 2009; 230:767-78. [PMID: 19626339 DOI: 10.1007/s00425-009-0982-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Accepted: 07/06/2009] [Indexed: 05/08/2023]
Abstract
Xylem differentiation in plants is under strict hormonal regulation. Auxins and cytokinins, together with brassinosteroids (BRs), appear to be the main hormones controlling vascular differentiation. In this report, we study the effect of these hormones on the basic peroxidase isoenzyme from Zinnia elegans (ZePrx), an enzyme involved in lignin biosynthesis. Results showed that auxins and cytokinins induce ZePrx, similarly to the way in which they induce seedling secondary growth (in particular, metaxylem differentiation). Likewise, the exogenous application of BR reduces the levels of ZePrx, in a similar way to their capacity to inhibit seedling secondary growth. Consistent with this notion, the exogenous application of BR reverses the auxin/cytokinin-induced ZePrx expression, but has no effect on the auxin/cytokinin-induced secondary growth. This differential hormonal response is supported by the analysis of the ZePrx promoter, which contains (a) cis-elements directly responsive to these hormones and (b) cis-elements targets of the plethora of transcription factors, such as NAC, MYB, AP2, MADS and class III HD Zip, which are up-regulated during the auxin- and cytokinin-induced secondary growth. Taken together, these results suggest that ZePrx is directly and indirectly regulated by the plethora of hormones that control xylem differentiation, supporting the role of ZePrx in xylem lignification.
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Affiliation(s)
- Jorge Gutiérrez
- Department of Plant Biology, University of La Coruña, 15071 La Coruña, Spain
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170
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Morse AM, Whetten RW, Dubos C, Campbell MM. Post-translational modification of an R2R3-MYB transcription factor by a MAP Kinase during xylem development. THE NEW PHYTOLOGIST 2009; 183:1001-1013. [PMID: 19566814 DOI: 10.1111/j.1469-8137.2009.02900.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Despite the pivotal role played by R2R3-MYB family members in the regulation of plant gene expression, little is known about post-translational regulation of these proteins. In animals, the MYB family member, c-MYB, is post-translationally modified by a mitogen-activated protein kinase (MAPK), p42(mapk). In order to test the hypothesis that R2R3-MYB proteins may be regulated by MAPK activity, interplay between a R2R3-MYB family member expressed in differentiating pine xylem (Pinus taeda MYB4, PtMYB4) and MAPK proteins expressed in the same tissue was examined. One of the MAPK proteins expressed in pine xylem, PtMAPK6, phosphorylated PtMYB4. Recombinant PtMAPK6 phosphorylated PtMYB4 on serine-236, located in the C-terminal activation domain of this transcription factor in a context that is found in other plant MYB proteins. Modification of the PtMAPK6 target serine in PtMYB4 did not appear to alter DNA binding in vitro but did alter the ability of PtMYB4 to promote transcriptional activation in yeast. PtMAPK6 activity was detected in developing xylem cells that had ceased cell division and formed secondary walls. Together, the data support a role for PtMAPK6 during early xylem development and suggest a function for this kinase in regulating gene expression through phosphorylation of PtMYB4.
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Affiliation(s)
- Alison M Morse
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA
| | - Ross W Whetten
- Department of Forestry and Environmental Resources, North Carolina State University, 5231 Jordan Hall, Box 8008, Raleigh, NC, 27695, USA
| | - Christian Dubos
- Centre for the Analysis of Genome Evolution & Function, Department of Cell & Systems Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, Canada, M5S 3B2
| | - Malcolm M Campbell
- Centre for the Analysis of Genome Evolution & Function, Department of Cell & Systems Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, Canada, M5S 3B2
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171
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Sonbol FM, Fornalé S, Capellades M, Encina A, Touriño S, Torres JL, Rovira P, Ruel K, Puigdomènech P, Rigau J, Caparrós-Ruiz D. The maize ZmMYB42 represses the phenylpropanoid pathway and affects the cell wall structure, composition and degradability in Arabidopsis thaliana. PLANT MOLECULAR BIOLOGY 2009; 70:283-96. [PMID: 19238561 DOI: 10.1007/s11103-009-9473-2] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Accepted: 02/12/2009] [Indexed: 05/07/2023]
Abstract
The involvement of the maize ZmMYB42 R2R3-MYB factor in the phenylpropanoid pathway and cell wall structure and composition was investigated by overexpression in Arabidopsis thaliana. ZmMYB42 down-regulates several genes of the lignin pathway and this effect reduces the lignin content in all lignified tissues. In addition, ZmMYB42 plants generate a lignin polymer with a decreased S to G ratio through the enrichment in H and G subunits and depletion in S subunits. This transcription factor also regulates other genes involved in the synthesis of sinapate esters and flavonoids. Furthermore, ZmMYB42 affects the cell wall structure and degradability, and its polysaccharide composition. Together, these results suggest that ZmMYB42 may be part of the regulatory network controlling the phenylpropanoid biosynthetic pathway.
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Affiliation(s)
- Fathi-Mohamed Sonbol
- Consorci CSIC-IRTA-UAB, Centre de Recerca en AgriGenomica (CRAG), Barcelona, Spain
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172
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Mellway RD, Tran LT, Prouse MB, Campbell MM, Constabel CP. The wound-, pathogen-, and ultraviolet B-responsive MYB134 gene encodes an R2R3 MYB transcription factor that regulates proanthocyanidin synthesis in poplar. PLANT PHYSIOLOGY 2009; 150:924-41. [PMID: 19395405 PMCID: PMC2689947 DOI: 10.1104/pp.109.139071] [Citation(s) in RCA: 193] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2009] [Accepted: 04/21/2009] [Indexed: 05/18/2023]
Abstract
In poplar (Populus spp.), the major defense phenolics produced in leaves are the flavonoid-derived proanthocyanidins (PAs) and the salicin-based phenolic glycosides. Transcriptional activation of PA biosynthetic genes leading to PA accumulation in leaves occurs following herbivore damage and mechanical wounding as well as infection by the fungal biotroph Melampsora medusae. In this study, we have identified a poplar R2R3 MYB transcription factor gene, MYB134, that exhibits close sequence similarity to the Arabidopsis (Arabidopsis thaliana) PA regulator TRANSPARENT TESTA2 and that is coinduced with PA biosynthetic genes following mechanical wounding, M. medusae infection, and exposure to elevated ultraviolet B light. Overexpression of MYB134 in poplar resulted in transcriptional activation of the full PA biosynthetic pathway and a significant plant-wide increase in PA levels, and electrophoretic mobility shift assays showed that recombinant MYB134 protein is able to bind to promoter regions of PA pathway genes. MYB134-overexpressing plants exhibited a concomitant reduction in phenolic glycoside concentrations and other minor alterations to levels of small phenylpropanoid metabolites. Our data provide insight into the regulatory mechanisms controlling stress-induced PA metabolism in poplar, and the identification of a regulator of stress-responsive PA biosynthesis constitutes a valuable tool for manipulating PA metabolism in poplar and investigating the biological functions of PAs in resistance to biotic and abiotic stresses.
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Affiliation(s)
- Robin D Mellway
- Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5
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173
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Mansfield SD. Solutions for dissolution--engineering cell walls for deconstruction. Curr Opin Biotechnol 2009; 20:286-94. [PMID: 19481436 DOI: 10.1016/j.copbio.2009.05.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2009] [Accepted: 05/05/2009] [Indexed: 11/27/2022]
Abstract
Photosynthetic carbon capture by terrestrial plants represents a major sink for atmospheric CO(2), ultimately terminating in the synthesis of a secondary plant cell wall-a complex matrix of polysaccharides intricately linked to lignin. The production and co-ordinated deposition of this lignocellulosic composite confers both protective and structural properties to the plant cell. The inherent properties of this complex cell wall also represent a major obstacle for its effective industrial utilization, as operationally effective mechanisms for the removal of lignin and the consequential release of carbohydrate constituents remain elusive. Perturbing plants by mis-regulating key genes/enzymes integral to major cell wall pathways can provide both rich insights into cell wall development and architecture, and concurrently provide significant opportunities for improved lignocellulose utilization.
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Affiliation(s)
- Shawn D Mansfield
- 4030-2424 Main Mall, Department of Wood Science, University of British Columbia, Vancouver, BC V6T1Z4, Canada.
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174
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Wilkins O, Nahal H, Foong J, Provart NJ, Campbell MM. Expansion and diversification of the Populus R2R3-MYB family of transcription factors. PLANT PHYSIOLOGY 2009; 149:981-93. [PMID: 19091872 PMCID: PMC2633813 DOI: 10.1104/pp.108.132795] [Citation(s) in RCA: 331] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2008] [Accepted: 12/12/2008] [Indexed: 05/17/2023]
Abstract
The R2R3-MYB proteins comprise one of the largest families of transcription factors in plants. R2R3-MYB family members regulate plant-specific processes, such as the elaboration of specialized cell types, including xylem, guard cells, trichomes, and root hairs, and the biosynthesis of specialized branches of metabolism, including phenylpropanoid biosynthesis. As such, R2R3-MYB family members are hypothesized to contribute to the emergence of evolutionary innovations that have arisen in specific plant lineages. As a first step in determining the role played by R2R3-MYB family members in the emergence of lineage-specific innovations in the genus Populus, the entire Populus trichocarpa R2R3-MYB family was characterized. The Populus R2R3-MYB complement is much larger than that found in other angiosperms with fully sequenced genomes. Phylogenetic analyses, together with chromosome placement, showed that the expansion of the Populus R2R3-MYB family was not only attributable to whole genome duplication but also involved selective expansion of specific R2R3-MYB clades. Expansion of the Populus R2R3-MYB family prominently involved members with expression patterns that suggested a role in specific components of Populus life history, including wood formation and reproductive development. An expandable compendium of microarray-based expression data (PopGenExpress) and associated Web-based tools were developed to better enable within- and between-species comparisons of Populus R2R3-MYB gene expression. This resource, which includes intuitive graphic visualization of gene expression data across multiple tissues, organs, and treatments, is freely available to, and expandable by, scientists wishing to better understand the genome biology of Populus, an ecologically dominant and economically important forest tree genus.
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Affiliation(s)
- Olivia Wilkins
- Department of Cell and Systems Biology and Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada M5S 3B2
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175
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Li X, Wu HX, Dillon SK, Southerton SG. Generation and analysis of expressed sequence tags from six developing xylem libraries in Pinus radiata D. Don. BMC Genomics 2009; 10:41. [PMID: 19159482 PMCID: PMC2636829 DOI: 10.1186/1471-2164-10-41] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Accepted: 01/21/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Wood is a major renewable natural resource for the timber, fibre and bioenergy industry. Pinus radiata D. Don is the most important commercial plantation tree species in Australia and several other countries; however, genomic resources for this species are very limited in public databases. Our primary objective was to sequence a large number of expressed sequence tags (ESTs) from genes involved in wood formation in radiata pine. RESULTS Six developing xylem cDNA libraries were constructed from earlywood and latewood tissues sampled at juvenile (7 yrs), transition (11 yrs) and mature (30 yrs) ages, respectively. These xylem tissues represent six typical development stages in a rotation period of radiata pine. A total of 6,389 high quality ESTs were collected from 5,952 cDNA clones. Assembly of 5,952 ESTs from 5' end sequences generated 3,304 unigenes including 952 contigs and 2,352 singletons. About 97.0% of the 5,952 ESTs and 96.1% of the unigenes have matches in the UniProt and TIGR databases. Of the 3,174 unigenes with matches, 42.9% were not assigned GO (Gene Ontology) terms and their functions are unknown or unclassified. More than half (52.1%) of the 5,952 ESTs have matches in the Pfam database and represent 772 known protein families. About 18.0% of the 5,952 ESTs matched cell wall related genes in the MAIZEWALL database, representing all 18 categories, 91 of all 174 families and possibly 557 genes. Fifteen cell wall-related genes are ranked in the 30 most abundant genes, including CesA, tubulin, AGP, SAMS, actin, laccase, CCoAMT, MetE, phytocyanin, pectate lyase, cellulase, SuSy, expansin, chitinase and UDP-glucose dehydrogenase. Based on the PlantTFDB database 41 of the 64 transcription factor families in the poplar genome were identified as being involved in radiata pine wood formation. Comparative analysis of GO term abundance revealed a distinct transcriptome in juvenile earlywood formation compared to other stages of wood development. CONCLUSION The first large scale genomic resource in radiata pine was generated from six developing xylem cDNA libraries. Cell wall-related genes and transcription factors were identified. Juvenile earlywood has a distinct transcriptome, which is likely to contribute to the undesirable properties of juvenile wood in radiata pine. The publicly available resource of radiata pine will also be valuable for gene function studies and comparative genomics in forest trees.
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Affiliation(s)
- Xinguo Li
- CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia
| | - Harry X Wu
- CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia
| | - Shannon K Dillon
- CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia
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176
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Zhou J, Lee C, Zhong R, Ye ZH. MYB58 and MYB63 are transcriptional activators of the lignin biosynthetic pathway during secondary cell wall formation in Arabidopsis. THE PLANT CELL 2009; 21:248-66. [PMID: 19122102 PMCID: PMC2648072 DOI: 10.1105/tpc.108.063321] [Citation(s) in RCA: 510] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Revised: 12/02/2008] [Accepted: 12/09/2008] [Indexed: 05/17/2023]
Abstract
It has previously been shown that SECONDARY WALL-ASSOCIATED NAC DOMAIN PROTEIN1 (SND1) is a key transcription factor regulating secondary cell wall formation, including the biosynthesis of cellulose, xylan, and lignin. In this study, we show that two closely related SND1-regulated MYB transcription factors, MYB58 and MYB63, are transcriptional regulators specifically activating lignin biosynthetic genes during secondary wall formation in Arabidopsis thaliana. MYB58 and MYB63 are phylogenetically distinct from previously characterized MYBs shown to be associated with secondary wall formation or phenylpropanoid metabolism. Expression studies showed that MYB58 and MYB63 are specifically expressed in fibers and vessels undergoing secondary wall thickening. Dominant repression of their functions led to a reduction in secondary wall thickening and lignin content. Overexpression of MYB58 and MYB63 resulted in specific activation of lignin biosynthetic genes and concomitant ectopic deposition of lignin in cells that are normally unlignified. MYB58 was able to activate directly the expression of lignin biosynthetic genes and a secondary wall-associated laccase (LAC4) gene. Furthermore, the expression of MYB58 and MYB63 was shown to be regulated by the SND1 close homologs NST1, NST2, VND6, and VND7 and their downstream target MYB46. Together, our results indicate that MYB58 and MYB63 are specific transcriptional activators of lignin biosynthesis in the SND1-mediated transcriptional network regulating secondary wall formation.
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Affiliation(s)
- Jianli Zhou
- Department of Plant Biology, University of Georgia, Athens, Georgia 30602, USA
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177
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Liao Y, Zou HF, Wang HW, Zhang WK, Ma B, Zhang JS, Chen SY. Soybean GmMYB76, GmMYB92, and GmMYB177 genes confer stress tolerance in transgenic Arabidopsis plants. Cell Res 2008; 18:1047-60. [PMID: 18725908 DOI: 10.1038/cr.2008.280] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
MYB-type transcription factors contain the conserved MYB DNA-binding domain of approximately 50 amino acids and are involved in the regulation of many aspects of plant growth, development, metabolism and stress responses. From soybean plants, we identified 156 GmMYB genes using our previously obtained 206 MYB unigenes, and 48 were found to have full-length open-reading frames. Expressions of all these identified genes were examined, and we found that expressions of 43 genes were changed upon treatment with ABA, salt, drought and/or cold stress. Three GmMYB genes, GmMYB76, GmMYB92 and GmMYB177, were chosen for further analysis. Using the yeast assay system, GmMYB76 and GmMYB92 were found to have transactivation activity and can form homodimers. GmMYB177 did not appear to have transactivation activity but can form heterodimers with GmMYB76. Yeast one-hybrid assay revealed that all the three GmMYBs could bind to cis-elements TAT AAC GGT TTT TT and CCG GAA AAA AGG AT, but with different affinity, and GmMYB92 could also bind to TCT CAC CTA CC. The transgenic Arabidopsis plants overexpressing GmMYB76 or GmMYB177 showed better performance than the GmMYB92-transgenic plants in salt and freezing tolerance. However, these transgenic plants exhibited reduced sensitivity to ABA treatment at germination stage in comparison with the wild-type plants. The three GmMYB genes differentially affected a subset of stress-responsive genes in addition to their regulation of a common subset of stress-responsive genes. These results indicate that the three GmMYB genes may play differential roles in stress tolerance, possibly through regulation of stress-responsive genes.
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Affiliation(s)
- Yong Liao
- Plant Gene Research Center, National Key Lab of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
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178
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Bomal C, Bedon F, Caron S, Mansfield SD, Levasseur C, Cooke JEK, Blais S, Tremblay L, Morency MJ, Pavy N, Grima-Pettenati J, Séguin A, Mackay J. Involvement of Pinus taeda MYB1 and MYB8 in phenylpropanoid metabolism and secondary cell wall biogenesis: a comparative in planta analysis. JOURNAL OF EXPERIMENTAL BOTANY 2008; 59:3925-39. [PMID: 18805909 PMCID: PMC2576632 DOI: 10.1093/jxb/ern234] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Revised: 08/15/2008] [Accepted: 08/19/2008] [Indexed: 05/18/2023]
Abstract
The involvement of two R2R3-MYB genes from Pinus taeda L., PtMYB1 and PtMYB8, in phenylpropanoid metabolism and secondary cell wall biogenesis was investigated in planta. These pine MYBs were constitutively overexpressed (OE) in Picea glauca (Moench) Voss, used as a heterologous conifer expression system. Morphological, histological, chemical (lignin and soluble phenols), and transcriptional analyses, i.e. microarray and reverse transcription quantitative PCR (RT-qPCR) were used for extensive phenotyping of MYB-overexpressing spruce plantlets. Upon germination of somatic embryos, root growth was reduced in both transgenics. Enhanced lignin deposition was also a common feature but ectopic secondary cell wall deposition was more strongly associated with PtMYB8-OE. Microarray and RT-qPCR data showed that overexpression of each MYB led to an overlapping up-regulation of many genes encoding phenylpropanoid enzymes involved in lignin monomer synthesis, while misregulation of several cell wall-related genes and other MYB transcription factors was specifically associated with PtMYB8-OE. Together, the results suggest that MYB1 and MYB8 may be part of a conserved transcriptional network involved in secondary cell wall deposition in conifers.
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Affiliation(s)
- Claude Bomal
- Centre d'Etude de Forêt, Université Laval, Québec (QC), Canada G1V 0A6.
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179
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Weng JK, Li X, Bonawitz ND, Chapple C. Emerging strategies of lignin engineering and degradation for cellulosic biofuel production. Curr Opin Biotechnol 2008; 19:166-72. [PMID: 18403196 DOI: 10.1016/j.copbio.2008.02.014] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Revised: 02/19/2008] [Accepted: 02/27/2008] [Indexed: 10/22/2022]
Abstract
Ethanol and other biofuels produced from lignocellulosic biomass represent a renewable, more carbon-balanced alternative to both fossil fuels and corn-derived or sugarcane-derived ethanol. Unfortunately, the presence of lignin in plant cell walls impedes the breakdown of cell wall polysaccharides to simple sugars and the subsequent conversion of these sugars to usable fuel. Recent advances in the understanding of lignin composition, polymerization, and regulation have revealed new opportunities for the rational manipulation of lignin in future bioenergy crops, augmenting the previous successful approach of manipulating lignin monomer biosynthesis. Furthermore, recent studies on lignin degradation in nature may provide novel resources for the delignification of dedicated bioenergy crops and other sources of lignocellulosic biomass.
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Affiliation(s)
- Jing-Ke Weng
- Department of Biochemistry, Purdue University, 175 South University Street, West Lafayette, IN 47907-2063, USA
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180
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Apuya NR, Park JH, Zhang L, Ahyow M, Davidow P, Van Fleet J, Rarang JC, Hippley M, Johnson TW, Yoo HD, Trieu A, Krueger S, Wu CY, Lu YP, Flavell RB, Bobzin SC. Enhancement of alkaloid production in opium and California poppy by transactivation using heterologous regulatory factors. PLANT BIOTECHNOLOGY JOURNAL 2008; 6:160-75. [PMID: 17961129 DOI: 10.1111/j.1467-7652.2007.00302.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Genes encoding regulatory factors isolated from Arabidopsis, soybean and corn have been screened to identify those that modulate the expression of genes encoding for enzymes involved in the biosynthesis of morphinan alkaloids in opium poppy (Papaver somniferum) and benzophenanthridine alkaloids in California poppy (Eschscholzia californica). In opium poppy, the over-expression of selected regulatory factors increased the levels of PsCOR (codeinone reductase), Ps4'OMT (S-adenosyl-l-methionine:3'-hydroxy-N-methylcoclaurine 4'-O-methyltransferase) and Ps6OMT [(R,S)-norcoclaurine 6-O-methyltransferase] transcripts by 10- to more than 100-fold. These transcriptional activations translated into an enhancement of alkaloid production in opium poppy of up to at least 10-fold. In California poppy, the transactivation effect of regulatory factor WRKY1 resulted in an increase of up to 60-fold in the level of EcCYP80B1 [(S)-N-methylcoclaurine 3'-hydroxylase] and EcBBE (berberine bridge enzyme) transcripts. As a result, the accumulations of selected alkaloid intermediates were enhanced up to 30-fold. The transactivation effects of other regulatory factors led to the accumulation of the same intermediates. These regulatory factors also led to the production of new alkaloids in California poppy callus culture.
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Affiliation(s)
- Nestor R Apuya
- Ceres, Inc., 1535 Rancho Conejo Blvd, Thousand Oaks, CA 91320, USA.
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181
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Zhong R, Ye ZH. Regulation of cell wall biosynthesis. CURRENT OPINION IN PLANT BIOLOGY 2007; 10:564-72. [PMID: 17950657 DOI: 10.1016/j.pbi.2007.09.001] [Citation(s) in RCA: 175] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2007] [Revised: 09/07/2007] [Accepted: 09/07/2007] [Indexed: 05/03/2023]
Abstract
Plant cell walls differ in their amount and composition among various cell types and even in different microdomains of the wall of a given cell. Plants must have evolved regulatory mechanisms controlling biosynthesis, targeted secretion, and assembly of wall components to achieve the heterogeneity in cell walls. A number of factors, including hormones, the cytoskeleton, glycosylphosphatidylinositol-anchored proteins, phosphoinositides, and sugar nucleotide supply, have been implicated in the regulation of cell wall biosynthesis or deposition. In the past two years, there have been important discoveries in transcriptional regulation of secondary wall biosynthesis. Several transcription factors in the NAC and MYB families have been shown to be the key switches for activation of secondary wall biosynthesis. These studies suggest a transcriptional network comprised of a hierarchy of transcription factors is involved in regulating secondary wall biosynthesis. Further investigation and integration of the regulatory players participating in the making of cell walls will certainly lead to our understanding of how wall amounts and composition are controlled in a given cell type. This may eventually allow custom design of plant cell walls on the basis of our needs.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
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182
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Ververidis F, Trantas E, Douglas C, Vollmer G, Kretzschmar G, Panopoulos N. Biotechnology of flavonoids and other phenylpropanoid-derived natural products. Part II: Reconstruction of multienzyme pathways in plants and microbes. Biotechnol J 2007; 2:1235-49. [PMID: 17935118 DOI: 10.1002/biot.200700184] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Plant natural products derived from phenylalanine and the phenylpropanoid pathways are impressive in their chemical diversity and are the result of plant evolution, which has selected for the acquisition of large repertoires of pigments, structural and defensive compounds, all derived from a phenylpropanoid backbone via the plant-specific phenylpropanoid pathway. These compounds are important in plant growth, development and responses to environmental stresses and thus can have large impacts on agricultural productivity. While plant-based medicines containing phenylpropanoid-derived active components have long been used by humans, the benefits of specific flavonoids and other phenylpropanoid-derived compounds to human health and their potential for long-term health benefits have only been recognized more recently. In this part of the review, we discuss in detail the recent strategies and achievements used in the reconstruction of multienzyme pathways in plants and microbes in an effort to be able to attain higher amounts of the desired flavonoids and stilbenoids exploiting their beneficial properties as analyzed extensively in Part I of this review.
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Affiliation(s)
- Filippos Ververidis
- Laboratory of Plant Biochemistry and Biotechnology, Department of Plant Sciences, Technological Educational Institute of Crete, Heraklion, Crete, Greece.
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183
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Gabaldón C, Gómez-Ros LV, Núñez-Flores MJL, Esteban-Carrasco A, Barceló AR. Post-translational modifications of the basic peroxidase isoenzyme from Zinnia elegans. PLANT MOLECULAR BIOLOGY 2007; 65:43-61. [PMID: 17588152 DOI: 10.1007/s11103-007-9197-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2007] [Accepted: 05/24/2007] [Indexed: 05/12/2023]
Abstract
The major basic peroxidase (ZePrx) from Zinnia elegans suspension cell cultures was purified and cloned. The purification resolved ZePrxs in two isoforms (ZePrx33.44 and ZePrx34.70), whose co-translational and post-translational modifications are characterized. Based on the N-terminal sequence obtained by Edman degradation of mature ZePxs, it may be expected that the immature polypeptides of ZePrxs contain a signal peptide (N-terminal pro-peptide) of 30 amino acids, which directs the polypeptide chains to the ER membrane. These immature polypeptides are co-translationally processed by proteolytic cleavage, and modeling studies of digestions suggested that the processing of the N-terminal pro-peptide of ZePrxs is performed by a peptidase from the SB clan (S8 family, subfamily A) of serine-type proteases. When the post-translational modifications of ZePrxs were characterized by trypsin digestion, and tryptic peptides were analyzed by reverse phase nano liquid chromatography (RP-nanoLC) coupled to MALDI-TOF MS, it was seen that, despite the presence in the primary structure of the protein of several (disulphide bridges, N-glycosylation, phosphorylation and N-myristoylation) potential post-translational modification sites, ZePrxs are only post-translationated modified by the formation of N-terminal pyroglutamate residues, disulphide bridges and N-glycosylation. Glycans of ZePrxs belong to three main types and conduce to the existence of at least ten different molecular isoforms. The first glycans belong to both low and high mannose-type glycans, with the growing structure Man(3-9)(GlcNAc)(2). Low mannose-type glycans, Man(3-4)(GlcNAc)(2), coexist with the truncated (paucimannosidic-type) glycan, Man(3)Xyl(1)Fuc(1)(GlcNAc)(2), in the G(3) and G(4 )sub-isoforms of ZePrx33.44. In ZePrx34.70, on the other hand, the complex-type biantennary glycan, Man(3)Xyl(1)Fuc(3)(GlcNAc)(5), and the truncated (paucimannosidic-type) glycan, Man(3)Xyl(1)Fuc(1)(GlcNAc)(2), appear to fill the two putative sites for N-glycosylation. Since the two N-glycosylation sites in ZePrxs are located in an immediately upstream loop region of helix F'' (close to the proximal histidine) and in helix F'' itself, and are flanked by positive-charged amino acids that produce an unusual positive-net surface electrostatic charge pattern, it may be expected that glycans not only affect reaction dynamics but may well participate in protein/cell wall interactions. These results emphasize the complexity of the ZePrx proteome and the difficulties involved in establishing any fine structure-function relationship.
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Affiliation(s)
- Carlos Gabaldón
- Department of Plant Biology, University of Murcia, 30100, Murcia, Spain
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184
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Pyo H, Demura T, Fukuda H. TERE; a novel cis-element responsible for a coordinated expression of genes related to programmed cell death and secondary wall formation during differentiation of tracheary elements. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2007; 51:955-65. [PMID: 17683474 DOI: 10.1111/j.1365-313x.2007.03180.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The differentiation of water-conducting tracheary elements (TEs) is the result of the orchestrated construction of secondary wall structure, including lignification, and programmed cell death (PCD), including cellular autolysis. To understand the orchestrated regulation of differentiation of TEs, we investigated the regulatory mechanism of gene expression directing TE differentiation. Detailed loss-of-function and gain-of-function analyses of the ZCP4 (Zinniacysteine protease 4) promoter, which confers TE-specific expression, demonstrated that a novel 11-bp cis-element is necessary and sufficient for the immature TE-specific promoter activity. The 11-bp cis-element-like sequences were found in promoters of many Arabidopsis TE differentiation-related genes. A gain-of-function analysis with similar putative cis-elements from secondary wall formation or modification-related genes as well as PCD-related genes indicated that the cis-elements are also sufficient for TE-specific expression of genes. These results demonstrate that a common sequence, designated as the tracheary-element-regulating cis-element, confers TE-specific expression to both genes related to secondary wall formation or modification and PCD.
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Affiliation(s)
- Hyunjin Pyo
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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185
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Zhong R, Richardson EA, Ye ZH. Two NAC domain transcription factors, SND1 and NST1, function redundantly in regulation of secondary wall synthesis in fibers of Arabidopsis. PLANTA 2007; 225:1603-11. [PMID: 17333250 DOI: 10.1007/s00425-007-0498-y] [Citation(s) in RCA: 247] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2006] [Accepted: 02/09/2007] [Indexed: 05/14/2023]
Abstract
Secondary walls are the major component of wood, and studies of the mechanisms regulating secondary wall synthesis is important for understanding the process of wood formation. We have previously shown that the NAC domain transcription factor SECONDARY WALL-ASSOCIATED NAC DOMAIN PROTEIN1 (SND1) is a key regulator of secondary wall synthesis in fibers of Arabidopsis thaliana stems and dominant repression of SND1 leads to a reduction in secondary wall thickening in fibers. However, T-DNA knockout of the SND1 gene did not cause an alteration in secondary wall thickness, suggesting that other SND1 homologs may compensate for the loss of SND1 expression. Here, we studied the effects of simultaneous inhibition of SND1 and its homolog, NAC SECONDARY WALL THICKENING PROMOTING FACTOR1 (NST1), on secondary wall synthesis in fibers. We show that simultaneous RNA interference (RNAi) inhibition of the expression of both SND1 and NST1 genes results in loss of secondary wall formation in fibers of stems. The fiber cells in the stems of SND1/NST1-RNAi plants lack all three major secondary wall components, including cellulose, xylan, and lignin, which is accompanied by a severe reduction in the expression of genes involved in their biosynthesis. In addition, inhibition of SND1 and NST1 leads to down-regulation of several fiber-associated transcription factor genes. Double T-DNA knockout mutations of SND1 and NST1 genes cause the same effects, as does simultaneous RNAi inhibition of SND1 and NST1. Our results provide first line evidence demonstrating that SND1 and NST1 function redundantly in the regulation of secondary wall synthesis in fibers.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
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186
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Bedon F, Grima-Pettenati J, Mackay J. Conifer R2R3-MYB transcription factors: sequence analyses and gene expression in wood-forming tissues of white spruce (Picea glauca). BMC PLANT BIOLOGY 2007; 7:17. [PMID: 17397551 PMCID: PMC1851958 DOI: 10.1186/1471-2229-7-17] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Accepted: 03/30/2007] [Indexed: 05/14/2023]
Abstract
BACKGROUND Several members of the R2R3-MYB family of transcription factors act as regulators of lignin and phenylpropanoid metabolism during wood formation in angiosperm and gymnosperm plants. The angiosperm Arabidopsis has over one hundred R2R3-MYBs genes; however, only a few members of this family have been discovered in gymnosperms. RESULTS We isolated and characterised full-length cDNAs encoding R2R3-MYB genes from the gymnosperms white spruce, Picea glauca (13 sequences), and loblolly pine, Pinus taeda L. (five sequences). Sequence similarities and phylogenetic analyses placed the spruce and pine sequences in diverse subgroups of the large R2R3-MYB family, although several of the sequences clustered closely together. We searched the highly variable C-terminal region of diverse plant MYBs for conserved amino acid sequences and identified 20 motifs in the spruce MYBs, nine of which have not previously been reported and three of which are specific to conifers. The number and length of the introns in spruce MYB genes varied significantly, but their positions were well conserved relative to angiosperm MYB genes. Quantitative RTPCR of MYB genes transcript abundance in root and stem tissues revealed diverse expression patterns; three MYB genes were preferentially expressed in secondary xylem, whereas others were preferentially expressed in phloem or were ubiquitous. The MYB genes expressed in xylem, and three others, were up-regulated in the compression wood of leaning trees within 76 hours of induction. CONCLUSION Our survey of 18 conifer R2R3-MYB genes clearly showed a gene family structure similar to that of Arabidopsis. Three of the sequences are likely to play a role in lignin metabolism and/or wood formation in gymnosperm trees, including a close homolog of the loblolly pine PtMYB4, shown to regulate lignin biosynthesis in transgenic tobacco.
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Affiliation(s)
- Frank Bedon
- Centre d'étude de la Forêt, Université Laval, Pavillon Charles-Eugène Marchand, Sainte Foy G1K7P4, Québec, Canada
- UMR CNRS/UPS 5546 Surfaces Cellulaires et Signalisation chez les Végétaux, Pôle de Biotechnologie Végétale, BP426 17 – Auzeville 31226, Castanet Tolosan, France
| | - Jacqueline Grima-Pettenati
- UMR CNRS/UPS 5546 Surfaces Cellulaires et Signalisation chez les Végétaux, Pôle de Biotechnologie Végétale, BP426 17 – Auzeville 31226, Castanet Tolosan, France
| | - John Mackay
- Centre d'étude de la Forêt, Université Laval, Pavillon Charles-Eugène Marchand, Sainte Foy G1K7P4, Québec, Canada
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187
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Sakakibara N, Nakatsubo T, Suzuki S, Shibata D, Shimada M, Umezawa T. Metabolic analysis of the cinnamate/monolignol pathway in Carthamus tinctorius seeds by a stable-isotope-dilution method. Org Biomol Chem 2007. [PMID: 17315067 DOI: 10.1007/s11101-009-9155-3] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Abstract
The present study established a system for comprehensive metabolic analysis of the cinnamate/monolignol and lignan pathways by the use of a stable-isotope-dilution method. The system was successfully applied to characterization of the pathways in Carthamus tinctorius cv. Round-leaved White maturing seeds in combination with administration of stable-isotope-labelled precursors. Experimental results obtained using this technique strongly suggested the intermediacy of ferulic acid in lignan biosynthesis in the plant.
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Affiliation(s)
- Norikazu Sakakibara
- Research Institute for Sustainable Humanosphare, Kyoto University, Uji, Kyoto 611-0011, Japan
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188
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Yang C, Xu Z, Song J, Conner K, Vizcay Barrena G, Wilson ZA. Arabidopsis MYB26/MALE STERILE35 regulates secondary thickening in the endothecium and is essential for anther dehiscence. THE PLANT CELL 2007; 19:534-48. [PMID: 17329564 PMCID: PMC1867336 DOI: 10.1105/tpc.106.046391] [Citation(s) in RCA: 213] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Revised: 01/06/2007] [Accepted: 02/05/2007] [Indexed: 05/14/2023]
Abstract
The Arabidopsis thaliana MYB26/MALE STERILE35 (MS35) gene is critical for the development of secondary thickening in the anther endothecium and subsequent dehiscence. MYB26 is localized to the nucleus and regulates endothecial development and secondary thickening in a cell-specific manner in the anther. MYB26 expression is seen in anthers and also in the style and nectaries, although there is no effect on female fertility in the ms35 mutant. MYB26 expression in anthers occurs early during endothecial development, with maximal expression during pollen mitosis I and bicellular stages, indicating a regulatory role in specifying early endothecial cell development. Overexpression of MYB26 results in ectopic secondary thickening in both Arabidopsis and tobacco (Nicotiana tabacum) plants, predominantly within the epidermal tissues. MYB26 regulates a number of genes linked to secondary thickening, including IRREGULAR XYLEM1 (IRX1), IRX3, IRX8, and IRX12. Changes in expression were also detected in two NAC domain genes, NAC SECONDARY WALL-PROMOTING FACTOR1 (NST1) and NST2, which have been linked to secondary thickening in the anther endothecium. These data indicate that MYB26 regulates NST1 and NST2 expression and in turn controls the process of secondary thickening. Therefore, MYB26 appears to function in a regulatory role involved in determining endothecial cell development within the anther and acts upstream of the lignin biosynthesis pathway.
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Affiliation(s)
- Caiyun Yang
- Plant Sciences Division, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicstershire LE12 5RD, United Kingdom
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189
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Abstract
Tracheary elements (TEs) are cells in the xylem that are highly specialized for transporting water and solutes up the plant. TEs undergo a very well-defined process of differentiation that involves specification, enlargement, patterned cell wall deposition, programmed cell death and cell wall removal. This process is coordinated such that adjacent TEs are joined together to form a continuous network. Expression studies on model systems as diverse as trees and cell cultures have contributed to providing a flood of candidate genes with potential roles in TE differentiation. Analysis of some of these genes has yielded important information on processes such as patterned secondary cell wall deposition. The current challenge is to continue this functional analysis and to use these data and build an integrated model of TE development.
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Affiliation(s)
- Simon Turner
- University of Manchester, Faculty of Life Sciences, Manchester, United Kingdom.
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190
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Friedmann M, Ralph SG, Aeschliman D, Zhuang J, Ritland K, Ellis BE, Bohlmann J, Douglas CJ. Microarray gene expression profiling of developmental transitions in Sitka spruce (Picea sitchensis) apical shoots. JOURNAL OF EXPERIMENTAL BOTANY 2007; 58:593-614. [PMID: 17220514 DOI: 10.1093/jxb/erl246] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The apical shoot drives the yearly new stem growth of conifer trees, is the primary site for the establishment of chemical and physical defences, and is important in establishing subsequent perennial growth. This organ presents an interesting developmental system, with growth and development progressing from a meristematic tip through development of a primary vascular system, to a base with fully differentiated and lignified secondary xylem on the inside and bark tissue with constitutive defence structures such as resin, polyphenolic phloem parenchyma cells, and sclereids on the outside. A spruce (Picea spp.) microarray containing approximately 16.7K unique cDNAs was used to study transcript profiles that characterize the developmental transition in apical shoots of Sitka spruce (Picea sitchensis) from their vegetative tips to their woody bases. Along with genes involved in cell-wall modification and lignin biosynthesis, a number of differentially regulated genes encoding protein kinases and transcription factors with base-preferred expression patterns were identified, which could play roles in the formation of woody tissues inside the apical shoot, as well as in regulating other developmental transitions associated with organ maturation. Preferential expression of known conifer defence genes, genes encoding defence-related proteins, and genes encoding regulatory proteins was observed at the apical shoot tip and in the green bark tissues at the apical shoot base, suggesting a commitment to constitutive defence in the apical shoot that is co-ordinated with rapid development of secondary xylem.
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Affiliation(s)
- Michael Friedmann
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
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191
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Fornalé S, Sonbol FM, Maes T, Capellades M, Puigdomènech P, Rigau J, Caparrós-Ruiz D. Down-regulation of the maize and Arabidopsis thaliana caffeic acid O-methyl-transferase genes by two new maize R2R3-MYB transcription factors. PLANT MOLECULAR BIOLOGY 2006; 62:809-23. [PMID: 16941210 DOI: 10.1007/s11103-006-9058-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2006] [Accepted: 07/13/2006] [Indexed: 05/11/2023]
Abstract
The maize (Zea mays L.) caffeic acid O-methyl-transferase (COMT) is a key enzyme in the biosynthesis of lignin. In this work we have characterized the involvement of COMT in the lignification process through the study of the molecular mechanisms involved in its regulation. The examination of the maize COMT gene promoter revealed a putative ACIII box, typically recognized by R2R3-MYB transcription factors. We used the sequence of known R2R3-MYB factors to isolate five maize R2R3-MYB factors (ZmMYB2, ZmMYB8, ZmMYB31, ZmMYB39, and ZmMYB42) and study their possible roles as regulators of the maize COMT gene. The factors ZmMYB8, ZmMY31, and ZmMYB42 belong to the subgroup 4 of the R2R3-MYB family along with other factors associated with lignin biosynthesis repression. In addition, the induction pattern of ZmMYB31 and ZmMYB42 gene expression on wounding is that expected for repressors of the maize COMT gene. Arabidopsis thaliana plants over-expressing ZmMYB31 and ZmMYB42 down-regulate both the A. thaliana and the maize COMT genes. Furthermore, the over-expression of ZmMYB31 and ZmMYB42 also affect the expression of other genes of the lignin pathway and produces a decrease in lignin content of the transgenic plants.
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Affiliation(s)
- Silvia Fornalé
- Departament de Genética Molecular, Laboratori de Genètica Molecular Vegetal, CSIC-IRTA, Jordi Girona 18-26, 08034, Barcelona, Spain
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192
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Zhong R, Demura T, Ye ZH. SND1, a NAC domain transcription factor, is a key regulator of secondary wall synthesis in fibers of Arabidopsis. THE PLANT CELL 2006; 18:3158-70. [PMID: 17114348 PMCID: PMC1693950 DOI: 10.1105/tpc.106.047399] [Citation(s) in RCA: 485] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Secondary walls in fibers and tracheary elements constitute the most abundant biomass produced by plants. Although a number of genes involved in the biosynthesis of secondary wall components have been characterized, little is known about the molecular mechanisms underlying the coordinated expression of these genes. Here, we demonstrate that the Arabidopsis thaliana NAC (for NAM, ATAF1/2, and CUC2) domain transcription factor, SND1 (for secondary wall-associated NAC domain protein), is a key transcriptional switch regulating secondary wall synthesis in fibers. We show that SND1 is expressed specifically in interfascicular fibers and xylary fibers in stems and that dominant repression of SND1 causes a drastic reduction in the secondary wall thickening of fibers. Ectopic overexpression of SND1 results in activation of the expression of secondary wall biosynthetic genes, leading to massive deposition of secondary walls in cells that are normally nonsclerenchymatous. In addition, we have found that SND1 upregulates the expression of several transcription factors that are highly expressed in fibers during secondary wall synthesis. Together, our results reveal that SND1 is a key transcriptional activator involved in secondary wall biosynthesis in fibers.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, Georgia 30602, USA
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193
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Baghdady A, Blervacq AS, Jouanin L, Grima-Pettenati J, Sivadon P, Hawkins S. Eucalyptus gunnii CCR and CAD2 promoters are active in lignifying cells during primary and secondary xylem formation in Arabidopsis thaliana. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2006; 44:674-83. [PMID: 17107813 DOI: 10.1016/j.plaphy.2006.10.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2006] [Accepted: 10/10/2006] [Indexed: 05/02/2023]
Abstract
Cell-specific expression patterns of the Eucalyptus gunnii cinnamoyl coenzymeA reductase (EgCCR) and cinnamyl alcohol dehydrogenase (EgCAD2) promoters were analyzed by promoter-GUS histochemistry in the primary and secondary xylem tissues from floral stems and roots of Arabidopsis thaliana. Expression patterns indicated that the EgCCR and EgCAD2 genes were expressed in a coordinated manner in primary and secondary xylem tissues of the Arabidopsis floral stem and root. Both genes were expressed in all lignifying cells (vessel elements, xylem fibers and paratracheal parenchyma cells) of xylem tissues. The capacity for long-term monolignol production appeared to be related to the cell-specific developmental processes and biological roles of different cell types. Our results suggested that lignification of short-lived vessel elements was achieved by a two-step process involving (i) monolignol production by vessel elements prior to vessel programmed cell death and (ii) subsequent monolignol production by vessel-associated living paratracheal parenchyma cells following vessel element cell death. EgCCR and EgCAD2 gene expression patterns suggested that the process of xylem cell lignification was similar in both primary and secondary xylem tissues in Arabidopsis floral stems and roots.
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Affiliation(s)
- A Baghdady
- Stress abiotiques et différenciation des végétaux cultivés, UMR USTL-INRA 1281, université des sciences et technologies de Lille, bâtiment SN2, cité scientifique, 59655 Villeneuve-d'Ascq cedex, France
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194
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Ko JH, Beers EP, Han KH. Global comparative transcriptome analysis identifies gene network regulating secondary xylem development in Arabidopsis thaliana. Mol Genet Genomics 2006; 276:517-31. [PMID: 16969662 DOI: 10.1007/s00438-006-0157-1] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2006] [Accepted: 08/03/2006] [Indexed: 12/20/2022]
Abstract
Our knowledge of the genetic control of wood formation (i.e., secondary growth) is limited. Here, we present a novel approach to unraveling the gene network regulating secondary xylem development in Arabidopsis, which incorporates complementary platforms of comparative-transcriptome analyses such as "digital northern" and "digital in situ" analysis. This approach effectively eliminated any genes that are expressed in either non-stem tissues/organs ("digital northern") or phloem and non-vascular regions ("digital in situ"), thereby identifying 52 genes that are upregulated only in the xylem cells of secondary growth tissues as "core xylem gene set". The proteins encoded by this gene set participate in signal transduction, transcriptional regulation, cell wall metabolism, and unknown functions. Five of the seven signal transduction-related genes represented in the core xylem gene set encode the essential components of ROP (Rho-related GTPase from plants) signaling cascade. Furthermore, the analysis of promoter sequences of the core xylem gene set identified a novel cis-regulatory element, ACAAAGAA. The functional significances of this gene set were verified by several independent experimental and bioinformatics methods.
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Affiliation(s)
- Jae-Heung Ko
- Department of Forestry, Michigan State University, East Lansing, MI 48824-1222, USA
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195
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Lu S, Zhou Y, Li L, Chiang VL. Distinct Roles of Cinnamate 4-hydroxylase Genes in Populus. ACTA ACUST UNITED AC 2006; 47:905-14. [PMID: 16720648 DOI: 10.1093/pcp/pcj063] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Cinnamate 4-hydroxylase (C4H) catalyzes the conversion of cinnamate into 4-hydroxy-cinnamate, a key reaction of the phenylpropanoid pathway which leads to the biosynthesis of several secondary metabolites. C4H genes exist as a multigene family in various plant species. In order to understand the roles of individual C4H members, four C4H cDNAs (PtreC4H) were isolated from Populus tremuloides and three C4H loci (PtriC4H) were identified in the P. trichocarpa genome. The ability of Populus C4H isoforms to convert trans-cinnamate into p-coumaric acid was verified by the examination of yeast recombinant PtreC4H proteins. Populus C4H genes were expressed in various tissues, including developing xylem, phloem and epidermis; however, the expression patterns of individual members were different from each other. Sequential analysis of C4H promoters showed that the differential expression of C4H genes was associated with cis-acting regulatory elements such as box L, box P and H box, suggesting that the divergent C4H isoforms played distinct roles in the production of secondary metabolites. The involvement of specific C4H isoforms in the biosynthesis of guaiacyl and syringyl monolignols is discussed.
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Affiliation(s)
- Shanfa Lu
- Forest Biotechnology Group, Department of Forestry and Environmental Resources, College of Natural Resources, North Carolina State University, Raleigh, NC 27695-7247, USA.
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196
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Urbanczyk-Wochniak E, Usadel B, Thimm O, Nunes-Nesi A, Carrari F, Davy M, Bläsing O, Kowalczyk M, Weicht D, Polinceusz A, Meyer S, Stitt M, Fernie AR. Conversion of MapMan to allow the analysis of transcript data from Solanaceous species: effects of genetic and environmental alterations in energy metabolism in the leaf. PLANT MOLECULAR BIOLOGY 2006; 60:773-92. [PMID: 16649112 DOI: 10.1007/s11103-005-5772-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2005] [Accepted: 12/08/2005] [Indexed: 05/08/2023]
Abstract
The tomato microarray TOM1 offers the possibility to monitor the levels of several thousand transcripts in parallel. The microelements represented on this tomato microarray have been putatively assigned to unigenes, and organised in functional classes using the MapMan ontology (Thimm et al., 2004. Plant J. 37: 914-939). This ontology was initially developed for use with the Arabidopsis ATH1 array, has a low level of redundancy, and can be combined with the MapMan software to provide a biologically structured overview of changes of transcripts, metabolites and enzyme activities. Use of this application is illustrated using three case studies with published or novel TOM1 array data sets for Solanaceous species. Comparison of previously reported data on transcript levels in potato leaves in the middle of the day and the middle of the night identified coordinated changes in the levels of transcripts of genes involved in various metabolic pathways and cellular events. Comparison with diurnal changes of gene expression in Arabidopsis revealed common features, illustrating how MapMan can be used to compare responses in different organisms. Comparison of transcript levels in new experiments performed on the leaves of the cultivated tomato S. lycopersicum and the wild relative S. pennellii revealed a general decrease of levels of transcripts of genes involved in terpene and, phenylpropanoid metabolism as well as chorismate biosynthesis in the crop compared to the wild relative. This matches the recently reported decrease of the levels of secondary metabolites in the latter. In the third case study, new expression array data for two genotypes deficient in TCA cycle enzymes is analysed to show that these genotypes have elevated levels of transcripts associated with photosynthesis. This in part explains the previously documented enhanced rates of photosynthesis in these genotypes. Since the Solanaceous MapMan is intended to be a community resource it will be regularly updated on improvements in tomato gene annotation and transcript profiling resources.
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Affiliation(s)
- Ewa Urbanczyk-Wochniak
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, Golm, 14476, Germany
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197
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Groover A, Robischon M. Developmental mechanisms regulating secondary growth in woody plants. CURRENT OPINION IN PLANT BIOLOGY 2006; 9:55-8. [PMID: 16337827 DOI: 10.1016/j.pbi.2005.11.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Accepted: 11/22/2005] [Indexed: 05/05/2023]
Abstract
Secondary growth results in the radial expansion of woody stems, and requires the coordination of tissue patterning, cell differentiation, and the maintenance of meristematic stem cells within the vascular cambium. Advances are being made towards describing molecular mechanisms that regulate these developmental processes, thanks in part to the application of new genetic technologies to forest trees, and the extension of knowledge about evolutionarily conserved mechanisms from model annuals. New studies demonstrate a central role for developmental mechanisms that involve transcriptional regulators, phytohormones and the cell wall in regulating secondary growth.
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Affiliation(s)
- Andrew Groover
- Institute of Forest Genetics, Pacific Southwest Research Station, USDA Forest Service, Davis, California 95616, USA.
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198
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Douglas CJ, Ehlting J. Arabidopsis thaliana full genome longmer microarrays: a powerful gene discovery tool for agriculture and forestry. Transgenic Res 2006; 14:551-61. [PMID: 16245146 DOI: 10.1007/s11248-005-8926-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2005] [Accepted: 06/13/2005] [Indexed: 10/25/2022]
Abstract
Sequenced plant genomes provide a large reservoir of known genes with potential for use in crop and tree improvement, but assignment of specific functions to annotated genes in sequenced plant genomes remains a challenge. Furthermore, most plant genes belong to families encoding proteins with related but distinct functions. In this commentary, we discuss our development of Arabidopsis spotted whole genome longmer oligonucleotide microarrays, and their use in global transcription profiling. We show that longmer array based transcriptome analysis in Arabidopsis can be used as an efficient and effective gene discovery and functional genomics tool, particularly for functional analyses of members of large gene families. We discuss experiments that focus on gene families involved in phenylpropanoid natural product biosynthesis and fiber differentiation. These analyses have helped to elucidate functions of individual gene family members, and have identified new candidate genes involved in fiber development and differentiation. Results obtained by these studies in Arabidopsis can be used as the basis for gene discovery in commercially important plants, and we have focused our attention on Populus trichocarpa (poplar), a species important in forestry and agroforestry for which complete genome sequence information is available.
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Affiliation(s)
- Carl J Douglas
- Department of Botany, University of British Columbia, BC V6T 1Z4 Vancouver, Canada.
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199
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Reddy MSS, Chen F, Shadle G, Jackson L, Aljoe H, Dixon RA. Targeted down-regulation of cytochrome P450 enzymes for forage quality improvement in alfalfa (Medicago sativa L.). Proc Natl Acad Sci U S A 2005; 102:16573-8. [PMID: 16263933 PMCID: PMC1283808 DOI: 10.1073/pnas.0505749102] [Citation(s) in RCA: 258] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2005] [Indexed: 11/18/2022] Open
Abstract
Improving the digestibility of forages provides a means to enhance animal performance and protect the environment against excessive animal waste. Increased lignin content during maturity, and corresponding changes in lignin composition, correlate with decreased digestibility of forages. These relationships have yet to be investigated in isogenic systems. By targeting three specific cytochrome P450 enzymes of the lignin pathway for antisense down-regulation, we generated transgenic alfalfa lines with a range of differences in lignin content and composition. There was a strong negative relationship between lignin content and rumen digestibility, but no relationship between lignin composition and digestibility, in these transgenic lines. Models for genetic manipulation of forage digestibility based on the changes in lignin composition that increase paper-pulping efficiency in trees are therefore invalid. Down-regulation of 4-coumarate 3-hydroxylase provided the largest improvements in digestibility yet seen in a forage crop.
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Affiliation(s)
- M S Srinivasa Reddy
- Plant Biology Division and Agriculture Division, Samuel Roberts Noble Foundation, Ardmore, OK 73401, USA
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200
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Gabaldón C, López-Serrano M, Pedreño MA, Barceló AR. Cloning and molecular characterization of the basic peroxidase isoenzyme from Zinnia elegans, an enzyme involved in lignin biosynthesis. PLANT PHYSIOLOGY 2005; 139:1138-54. [PMID: 16258008 PMCID: PMC1283753 DOI: 10.1104/pp.105.069674] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The major basic peroxidase from Zinnia elegans (ZePrx) suspension cell cultures was purified and cloned, and its properties and organ expression were characterized. The ZePrx was composed of two isoforms with a M(r) (determined by matrix-assisted laser-desorption ionization time of flight) of 34,700 (ZePrx34.70) and a M(r) of 33,440 (ZePrx33.44). Both isoforms showed absorption maxima at 403 (Soret band), 500, and 640 nm, suggesting that both are high-spin ferric secretory class III peroxidases. M(r) differences between them were due to the glycan moieties, and were confirmed from the total similarity of the N-terminal sequences (LSTTFYDTT) and by the 99.9% similarity of the tryptic fragment fingerprints obtained by reverse-phase nano-liquid chromatography. Four full-length cDNAs coding for these peroxidases were cloned. They only differ in the 5'-untranslated region. These differences probably indicate different ways in mRNA transport, stability, and regulation. According to the k(cat) and apparent K(m)(RH) values shown by both peroxidases for the three monolignols, sinapyl alcohol was the best substrate, the endwise polymerization of sinapyl alcohol by both ZePrxs yielding highly polymerized lignins with polymerization degrees > or =87. Western blots using anti-ZePrx34.70 IgGs showed that ZePrx33.44 was expressed in tracheary elements, roots, and hypocotyls, while ZePrx34.70 was only expressed in roots and young hypocotyls. None of the ZePrx isoforms was significantly expressed in either leaves or cotyledons. A neighbor-joining tree constructed for the four full-length cDNAs suggests that the four putative paralogous genes encoding the four cDNAs result from duplication of a previously duplicated ancestral gene, as may be deduced from the conserved nature and conserved position of the introns.
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Affiliation(s)
- Carlos Gabaldón
- Department of Plant Biology, University of Murcia, E-30100 Murcia, Spain
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