The Experts below are selected from a list of 15306 Experts worldwide ranked by ideXlab platform
Margit Sara - One of the best experts on this subject based on the ideXlab platform.
-
structural characterization of the acid degraded Secondary Cell Wall polymer of geobacillus stearothermophilus pv72 p2
Carbohydrate Research, 2008Co-Authors: Bent O Petersen, Margit Sara, Christoph Mader, Harald F Mayer, Uwe B Sleytr, Martin Pabst, Michael Puchberger, Eberhard Krause, Andreas Hofinger, Jens O DuusAbstract:Abstract The Secondary Cell Wall polymer (SCWP) from Geobacillus stearothermophilus PV72/p2, which is involved in the anchoring of the surface-layer protein to the bacterial Cell Wall layer, is composed of 2-amino-2-deoxy- and 2-acetamido-2-deoxy- d -glucose, 2-acetamido-2-deoxy- d -mannose, and 2-acetamido-2-deoxy- d -mannuronic acid. The primary structure of the acid-degraded polysaccharide—liberated by HF-treatment from the Cell Wall—was determined by high-field NMR spectroscopy and mass spectrometry using N-acetylated and hydrolyzed polysaccharide derivatives as well as Smith-degradation. The polysaccharide was shown to consist of a tetrasaccharide repeating unit containing a pyruvic acid acetal at a side-chain 2-acetamido-2-deoxy-α- d -mannopyranosyl residue. Substoichiometric substitutions of the repeating unit were observed concerning the degree of N-acetylation of glucosamine residues and the presence of side-chain linked 2-acetamido-2-deoxy-β- d -glucopyranosyl units: Download full-size image
-
conserved anchoring mechanisms between crystalline Cell surface s layer proteins and Secondary Cell Wall polymers in gram positive bacteria
Trends in Microbiology, 2001Co-Authors: Margit SaraAbstract:The Cell Wall is an important structuralcomponent of prokaryotic organisms andis essential for bacterial survival.Although in Gram-positive bacteria theprimary function of the rigid Cell Walllayer, which comprises peptidoglycan andaccessory (Secondary) Cell Wall polymers,is to provide an exoskeleton for protectionagainst mechanical and osmotic stress, itis also an attachment site for otherproteins interacting with the bacterialenvironment
-
structural and functional analyses of the Secondary Cell Wall polymer of bacillus sphaericus ccm 2177 that serves as an s layer specific anchor
Journal of Bacteriology, 1999Co-Authors: Nicola Ilk, Harald F Mayer, Uwe B Sleytr, Michael Puchberger, Paul Kosma, Eva M Egelseer, Margit SaraAbstract:Sacculi of Bacillus sphaericus CCM 2177 contain a Secondary Cell Wall polymer which was completely extracted with 48% hydrofluoric acid. Nuclear magnetic resonance analysis showed that the polymer is composed of repeating units, as follows:33)-[4,6-O-(1-carboxyethylidene)];0.5-b-D-ManpNAc-(134)-b-D-GlcpNAc-(13. The N-terminal part of the S-layer protein carrying S-layer homologous motifs recognizes this polymer as a binding site.
-
evidence that the n terminal part of the s layer protein from bacillus stearothermophilus pv72 p2 recognizes a Secondary Cell Wall polymer
Journal of Bacteriology, 1997Co-Authors: W Ries, Uwe B Sleytr, Christoph Hotzy, I Schocher, Margit SaraAbstract:The S-layer of Bacillus stearothermophilus PV72/p2 shows oblique lattice symmetry and is composed of identical protein subunits with a molecular weight of 97,000. The isolated S-layer subunits could bind and recrystallize into the oblique lattice on native peptidoglycan-containing sacculi which consist of peptidoglycan of the A1gamma chemotype and a Secondary Cell Wall polymer with an estimated molecular weight of 24,000. The Secondary Cell Wall polymer could be completely extracted from peptidoglycan-containing sacculi with 48% HF, indicating the presence of phosphodiester linkages between the polymer chains and the peptidoglycan backbone. The Cell Wall polymer was composed mainly of GlcNAc and ManNAc in a molar ratio of 4:1, constituted about 20% of the peptidoglycan-containing sacculus dry weight, and was also detected in the fraction of the S-layer self-assembly products. Extraction experiments and recrystallization of the whole S-layer protein and proteolytic cleavage fragments confirmed that the Secondary Cell Wall polymer is responsible for anchoring the S-layer subunits by the N-terminal part to the peptidoglycan-containing sacculi. In addition to this binding function, the Cell Wall polymer was found to influence the in vitro self-assembly of the guanidinium hydrochloride-extracted S-layer protein. Chemical modification studies further showed that the Secondary Cell Wall polymer does not contribute significant free amino or carboxylate groups to the peptidoglycan-containing sacculi.
Keming Luo - One of the best experts on this subject based on the ideXlab platform.
-
r2r3 myb transcription factor myb6 promotes anthocyanin and proanthocyanidin biosynthesis but inhibits Secondary Cell Wall formation in populus tomentosa
Plant Journal, 2019Co-Authors: Lijun Wang, Lingyu Ran, Di Fan, Liwen Dou, Shu Yao, Keming LuoAbstract:The Secondary Cell Wall is an important carbon sink in higher plants and its biosynthesis requires coordination of metabolic fluxes in the phenylpropanoid pathway. In Arabidopsis (Arabidopsis thaliana), MYB75 and the KNOX transcription factor KNAT7 form functional complexes to regulate Secondary Cell Wall formation in the inflorescence stem. However, the molecular mechanism by which these transcription factors control different branches of the phenylpropanoid pathway remains poorly understood in woody species. We isolated an R2R3-MYB transcription factor MYB6 from Populus tomentosa and determined that it was expressed predominately in young leaves. Overexpression of MYB6 in transgenic poplar upregulated flavonoid biosynthetic gene expression, resulting in significantly increased accumulation of anthocyanin and proanthocyanidins. MYB6-overexpression plants showed reduced Secondary Cell Wall deposition, accompanied by repressed expression of Secondary Cell Wall biosynthetic genes. We further showed that MYB6 interacted physically with KNAT7 and formed functional complexes that acted to repress Secondary Cell Wall development in poplar and Arabidopsis. The results provide an insight into the transcriptional mechanisms involved in the regulation of the metabolic fluxes between the flavonoid and lignin biosynthetic pathways in poplar.
-
ectopic expression of ptomyb74 in poplar and arabidopsis promotes Secondary Cell Wall formation
Frontiers in Plant Science, 2018Co-Authors: Keming LuoAbstract:In vascular plants, R2R3-MYB transcription factors are important regulators of Secondary Cell Wall formation. Although 192 annotated R2R3 MYB genes were identified in the poplar genome, only a few members were characterized to participate in the regulation of the Secondary Cell Wall biosynthesis. In this paper, we identify an R2R3-MYB transcription factor, PtoMYB74, which is predicted to be an ortholog of Arabidopsis AtMYB61, a transcription activator that regulates the Secondary Cell Wall formation, lignin biosynthesis, stomatal aperture, and the mucilage of seed coat. PtoMYB74 is mainly expressed in the stems, especially in the xylem tissues and organs. PtoMYB74 as a transcriptional activator is localized to the nucleus. The overexpression of PtoMYB74 increased the Secondary Cell Wall thickness of vessels in transgenic poplar and changed the Secondary Cell Wall compositions. The expression levels of lignin and Cellulose biosynthetic genes were elevated in the transgenic poplar overexpressing PtoMYB74 compared to the wild type, while there was no change in the xylan biosynthetic genes. Transcriptional activation assays demonstrated that PtoMYB74 could activate the promoters of structural genes in the lignin and Cellulose biosynthetic pathways. Taken together, our data show that PtoMYB74 positively regulates the Secondary Cell Wall biosynthesis in poplar.
-
ptomyb92 is a transcriptional activator of the lignin biosynthetic pathway during Secondary Cell Wall formation in populus tomentosa
Plant and Cell Physiology, 2015Co-Authors: Xianqiang Wang, Keming Luo, Lingyu Ran, Qiaoyan Tian, Di FanAbstract:Wood is the most abundant biomass in perennial woody plants and is mainly made up of Secondary Cell Wall. R2R3-MYB transcription factors are important regulators of Secondary Wall biosynthesis in plants. In this study, we describe the identification and characterization of a poplar MYB transcription factor PtoMYB92, a homolog of Arabidopsis MYB42 and MYB85, which is involved in the regulation of Secondary Cell Wall biosynthesis. PtoMYB92 is specifically expressed in xylem tissue in poplar. SubCellular localization and transcriptional activation analysis suggest that PtoMYB92 is a nuclear-localized transcriptional activator. Overexpression of PtoMYB92 in poplar resulted in an increase in Secondary Cell Wall thickness in stems and ectopic deposition of lignin in leaves. Quantitative real-time PCR showed that PtoMYB92 specifically activated the expression of lignin biosynthetic genes. Furthermore, transient expression assays using a β-glucuronidase (GUS) reporter gene revealed that PtoMYB92 is an activator in the lignin biosynthetic pathway during Secondary Cell Wall formation. Taken together, our results suggest that PtoMYB92 is involved in the regulation of Secondary Cell Wall formation in poplar by controlling the biosynthesis of monolignols.
-
a poplar r2r3 myb transcription factor ptrmyb152 is involved in regulation of lignin biosynthesis during Secondary Cell Wall formation
Plant Cell Tissue and Organ Culture, 2014Co-Authors: Xianqiang Wang, Keming Luo, Qiaoyan Tian, Rui Liu, Yiming SunAbstract:Wood is the most abundant biomass in perennial woody plants. Extensive studies have shown that R2R3-MYB transcription factors are involved in regulation of lignin biosynthesis during Secondary Cell Wall formation in many plant species, such as Arabidopsis, rice, maize and poplar. In this study, a MYB transcription factor, named PtrMYB152, was isolated from Populus trichocarpa and encoded a protein of 321 amino acids that contained a conserved R2R3-MYB domain. Phylogenetic analysis revealed that PtrMYB152 shares high sequence homology with other known plant MYBs associated with Secondary Wall formation. PtrMYB152 is specifically expressed in Secondary Wall-forming Cells in poplar. Histochemical localizations of GUS expression in the transgenic Arabidopsis plants showed that PtrMYB152 is predominantly expressed in vascular tissues. Overexpression of PtrMYB152 resulted in specific activation of lignin biosynthetic genes, and caused ectopic deposition of lignin in stem and petiole of transgenic plants. These data indicated that PtrMYB152 is a specific transcriptional activator of lignin biosynthesis during wood formation of poplar.
Richard A. Dixon - One of the best experts on this subject based on the ideXlab platform.
-
current models for transcriptional regulation of Secondary Cell Wall biosynthesis in grasses
Frontiers in Plant Science, 2018Co-Authors: Xiaolan Rao, Richard A. DixonAbstract:Secondary Cell Walls mediate many crucial biological processes in plants including mechanical support, water and nutrient transport and stress management. They also provide an abundant resource of renewable feed, fiber, and fuel. The grass family contains the most important food, forage, and biofuel crops. Understanding the regulatory mechanism of Secondary Wall formation in grasses is necessary for exploiting these plants for agriculture and industry. Previous research has established a detailed model of the Secondary Wall regulatory network in the dicot model species Arabidopsis thaliana. Grasses, branching off from the dicot ancestor 140-150 million years ago, display distinct Cell Wall morphology and composition, suggesting potential for a different Secondary Wall regulation program from that established for dicots. Recently, combined application of molecular, genetic and bioinformatics approaches have revealed more transcription factors involved in Secondary Cell Wall biosynthesis in grasses. Compared with the dicots, grasses exhibit a relatively conserved but nevertheless divergent transcriptional regulatory program to activate their Secondary Cell Wall development and to coordinate Secondary Wall biosynthesis with other physiological processes.
-
pinoresinol reductase 1 impacts lignin distribution during Secondary Cell Wall biosynthesis in arabidopsis
Phytochemistry, 2015Co-Authors: Qiao Zhao, Yining Zeng, Yanbin Yin, Lisa A Jackson, Nancy L Engle, Madhavi Z Martin, Timothy J Tschaplinski, Shi You Ding, Arthur J Ragauskas, Richard A. DixonAbstract:Pinoresinol reductase (PrR) catalyzes the conversion of the lignan (-)-pinoresinol to (-)-lariciresinol in Arabidopsis thaliana, where it is encoded by two genes, PrR1 and PrR2, that appear to act redundantly. PrR1 is highly expressed in lignified inflorescence stem tissue, whereas PrR2 expression is barely detectable in stems. Co-expression analysis has indicated that PrR1 is co-expressed with many characterized genes involved in Secondary Cell Wall biosynthesis, whereas PrR2 expression clusters with a different set of genes. The promoter of the PrR1 gene is regulated by the Secondary Cell Wall related transcription factors SND1 and MYB46. The loss-of-function mutant of PrR1 shows, in addition to elevated levels of pinoresinol, significantly decreased lignin content and a slightly altered lignin structure with lower abundance of cinnamyl alcohol end groups. Stimulated Raman scattering (SRS) microscopy analysis indicated that the lignin content of the prr1-1 loss-of-function mutant is similar to that of wild-type plants in xylem Cells, which exhibit a normal phenotype, but is reduced in the fiber Cells. Together, these data suggest an association of the lignan biosynthetic enzyme encoded by PrR1 with Secondary Cell Wall biosynthesis in fiber Cells.
-
on off switches for Secondary Cell Wall biosynthesis
Molecular Plant, 2012Co-Authors: Huanzhong Wang, Richard A. DixonAbstract:Secondary Cell Walls provide plants with rigidity and strength to support their body weight and ensure water and nutrient transport. They also provide textiles, timber, and potentially second-generation biofuels for human use. Genes responsible for synthesis of the different Cell Wall components, namely Cellulose, hemiCelluloses, and lignin, are coordinately expressed and under transcriptional regulation. In the past several years, Cell Wall-related NAC and MYB transcription factors have been intensively investigated in different species and shown to be master switches of Secondary Cell Wall biosynthesis. Positive and negative regulators, which function upstream of NAC master switches, have also been identified in different plant tissues. Further elucidation of the regulatory mechanisms of Cell Wall synthesis will facilitate the engineering of plant feedstocks suitable for biofuel production.
-
NAC domain function and transcriptional control of a Secondary Cell Wall master switch.
The Plant Journal, 2011Co-Authors: Huanzhong Wang, Fang Chen, Qiao Zhao, Mingyi Wang, Richard A. DixonAbstract:Summary NAC domain transcription factors act as master switches for Secondary Cell Wall thickening, but how they exert their function and how their expression is regulated remains unclear. Here we identify a loss-of-function point mutation in the NST1 gene of Medicago truncatula. The nst1-3 mutant shows no lignification in interfascicular fibers, as previously seen in tnt1 transposon insertion alleles. However, the C→A transversion, which causes a T94K mutation in the NST1 protein, leads to increased NST1 expression. Introduction of the same mutation into the Arabidopsis homolog SND1 causes both protein mislocalization and loss of target DNA binding, with a resultant inability to trans-activate downstream Secondary Wall synthesis genes. Furthermore, trans-activation assays show that the expression of SND1 operates under positive feedback control from itself, and SND1 was shown to bind directly to a conserved motif in its own promoter, located within a recently described 19-bp Secondary Wall NAC binding element. Three MYB transcription factors downstream of SND1, one of which is directly regulated by SND1, exert negative regulation on SND1 promoter activity. Our results identify a conserved amino acid critical for NST1/SND1 function, and show that the expression of the NAC master switch itself is under both positive (autoregulatory) and negative control.
Simon R Turner - One of the best experts on this subject based on the ideXlab platform.
-
arabidopsis genes irregular xylem irx15 and irx15l encode duf579 containing proteins that are essential for normal xylan deposition in the Secondary Cell Wall
Plant Journal, 2011Co-Authors: David Brown, Raymond Wightman, Paul Dupree, Zhinong Zhang, Leonardo D Gomez, I Atanassov, John Paul Bukowski, Theodora Tryfona, Simon J Mcqueenmason, Simon R TurnerAbstract:: There are 10 genes in the Arabidopsis genome that contain a domain described in the Pfam database as domain of unknown function 579 (DUF579). Although DUF579 is widely distributed in eukaryotic species, there is no direct experimental evidence to assign a function to it. Five of the 10 Arabidopsis DUF579 family members are co-expressed with marker genes for Secondary Cell Wall formation. Plants in which two closely related members of the DUF579 family have been disrupted by T-DNA insertions contain less xylose in the Secondary Cell Wall as a result of decreased xylan content, and exhibit mildly distorted xylem vessels. Consequently we have named these genes IRREGULAR XYLEM 15 (IRX15) and IRX15L. These mutant plants exhibit many features of previously described xylan synthesis mutants, such as the replacement of glucuronic acid side chains with methylglucuronic acid side chains. By contrast, immunostaining of xylan and transmission electron microscopy (TEM) reveals that the Walls of these irx15 irx15l double mutants are disorganized, compared with the wild type or other previously described xylan mutants, and exhibit dramatic increases in the quantity of sugar released in Cell Wall digestibility assays. Furthermore, localization studies using fluorescent fusion proteins label both the Golgi and also an unknown intraCellular compartment. These data are consistent with irx15 and irx15l defining a new class of genes involved in xylan biosynthesis. How these genes function during xylan biosynthesis and deposition is discussed.
-
the roles of the cytoskeleton during Cellulose deposition at the Secondary Cell Wall
Plant Journal, 2008Co-Authors: Raymond Wightman, Simon R TurnerAbstract:During Secondary Cell Wall formation, developing xylem vessels deposit Cellulose at specific sites on the plasma membrane. Bands of cortical microtubules mark these sites and are believed to somehow orientate the Cellulose synthase complexes. We have used live Cell imaging on intact roots of Arabidopsis to explore the relationship between the microtubules, actin and the Cellulose synthase complex during Secondary Cell Wall formation. The Cellulose synthase complexes are seen to form bands beneath sites of Secondary Wall synthesis. We find that their maintenance at these sites is dependent upon underlying bundles of microtubules which localize the Cellulose synthase complex (CSC) to the edges of developing Cell Wall thickenings. Thick actin cables run along the long axis of the Cells. These cables are essential for the rapid trafficking of complex-containing organelles around the Cell. The CSCs appear to be delivered directly to sites of Secondary Cell Wall synthesis and it is likely that transverse actin may mark these sites.
-
identification of novel genes in arabidopsis involved in Secondary Cell Wall formation using expression profiling and reverse genetics
The Plant Cell, 2005Co-Authors: David M Brown, Leo A H Zeef, Joanne Ellis, Royston Goodacre, Simon R TurnerAbstract:Forward genetic screens have led to the isolation of several genes involved in Secondary Cell Wall formation. A variety of evidence, however, suggests that the list of genes identified is not exhaustive. To address this problem, microarray data have been generated from tissue undergoing Secondary Cell Wall formation and used to identify genes that exhibit a similar expression pattern to the Secondary Cell Wall–specific Cellulose synthase genes IRREGULAR XYLEM1 (IRX1) and IRX3. Cross-referencing this analysis with publicly available microarray data resulted in the selection of 16 genes for reverse genetic analysis. Lines containing an insertion in seven of these genes exhibited a clear irx phenotype characteristic of a Secondary Cell Wall defect. Only one line, containing an insertion in a member of the COBRA gene family, exhibited a large decrease in Cellulose content. Five of the genes identified as being essential for Secondary Cell Wall biosynthesis have not been previously characterized. These genes are likely to define entirely novel processes in Secondary Cell Wall formation and illustrate the success of combining expression data with reverse genetics to address gene function.
-
Cellulose synthesis in the Arabidopsis Secondary Cell Wall
Cellulose, 2004Co-Authors: Neil G Taylor, John C. Gardiner, Raymond Whiteman, Simon R TurnerAbstract:The identification of genes responsible for Cellulose synthesis has led to a significant advance in our understanding of the synthesis of this important polymer. The identification of these genes has arisen from the identification of Cellulose deficient mutants. The irregular xylem ( irx ) mutants of Arabidopsis are caused by a severe reduction in Cellulose synthesis in the Secondary Cell Wall. Three irx mutants deficient in Secondary Cell Wall Cellulose are the result of mutations in three different members of the Cellulose synthase catalytic subunit (CesA) gene family. The three proteins encoded by these genes all associate within the same membrane bound complex, and the presence of all three, but not their activity, is required for correct assembly and targeting of this complex. The knowledge that these three proteins associate provides a good opportunity to purify the Cellulose synthase complex, and recent results working towards this goal are discussed.
-
the irregular xylem 2 mutant is an allele of korrigan that affects the Secondary Cell Wall of arabidopsis thaliana
Plant Journal, 2004Co-Authors: Pio M J Szyjanowicz, Neil G Taylor, Iain Mckinnon, John Gardiner, Michael C Jarvis, Simon R TurnerAbstract:The irregular xylem 2 (irx2) mutant of Arabidopsis thaliana exhibits a Cellulose deficiency in the Secondary Cell Wall, which is brought about by a point mutation in the KORRIGAN (KOR) beta,1-4 endoglucanase (beta,1-4 EGase) gene. Measurement of the total crystalline Cellulose in the inflorescence stem indicates that the irx2 mutant contains approximately 30% of the level present in the wild type (WT). Fourier-Transform Infra Red (FTIR) analysis, however, indicates that there is no decrease in Cellulose in primary Cell Walls of the cortical and epidermal Cells of the stem. KOR expression is correlated with Cellulose synthesis and is highly expressed in Cells synthesising a Secondary Cell Wall. Co-precipitation experiments, using either an epitope-tagged form of KOR or IRX3 (AtCesA7), suggest that KOR is not an integral part of the Cellulose synthase complex. These data are supported by immunolocalisation of KOR that suggests that KOR does not localise to sites of Secondary Cell Wall deposition in the developing xylem. The defect in irx2 plant is consistent with a role for KOR in the later stages of Secondary Cell Wall formation, suggesting a role in processing of the growing microfibrils or release of the Cellulose synthase complex.
Shawn D Mansfield - One of the best experts on this subject based on the ideXlab platform.
-
organization of xylan production in the golgi during Secondary Cell Wall biosynthesis
Plant Physiology, 2019Co-Authors: Miranda J Meents, Sanya Motani, Shawn D Mansfield, Lacey A SamuelsAbstract:Secondary Cell Wall (SCW) production during xylem development requires massive up-regulation of hemiCellulose (e.g. glucuronoxylan) biosynthesis in the Golgi. Although mutant studies have revealed much of the xylan biosynthetic machinery, the precise arrangement of these proteins and their products in the Golgi apparatus is largely unknown. We used a fluorescently tagged xylan backbone biosynthetic protein (IRREGULAR XYLEM9; IRX9) as a marker of xylan production in the Golgi of developing protoxylem tracheary elements in Arabidopsis (Arabidopsis thaliana). Both live-Cell confocal and transmission electron microscopy (TEM) revealed SCW deposition is accompanied by a significant proliferation of Golgi stacks. Furthermore, although Golgi stacks were randomly distributed, the organization of the cytoplasm ensured their close proximity to developing SCWs. Quantitative immuno-TEM revealed IRX9 is present in a specific subdomain of the Golgi stack and was most abundant in the ring of the inner margins of medial cisternae where fenestrations are abundant. Conversely, the xylan product accumulated in swollen trans cisternal margins and the Trans-Golgi network (TGN). The irx9 mutant lacked this expansion for both the cisternal margins and the TGN, whereas Golgi stack proliferation was unaffected. Golgi in irx9 also displayed dramatic changes in their structure, with increases in cisternal fenestration and tubulation. Our data support a new model where xylan biosynthesis and packaging into secretory vesicles are localized in distinct structural and functional domains of the Golgi. Rather than polysaccharide biosynthesis occurring in the center of the cisternae, IRX9 and the xylan product are arranged in successive concentric rings in Golgi cisternae.
-
regulation of Secondary Cell Wall biosynthesis by poplar r2r3 myb transcription factor ptrmyb152 in arabidopsis
Scientific Reports, 2015Co-Authors: Shucai Wang, Shawn D Mansfield, Ilga Porth, Jingui Chen, Carl J DouglasAbstract:Poplar has 192 annotated R2R3 MYB genes, of which only three have been shown to play a role in the regulation of Secondary Cell Wall formation. Here we report the characterization of PtrMYB152, a poplar homolog of the Arabidopsis R2R3 MYB transcription factor AtMYB43, in the regulation of Secondary Cell Wall biosynthesis. The expression of PtrMYB152 in Secondary xylem is about 18 times of that in phloem. When expressed in Arabidopsis under the control of either 35S or PtrCesA8 promoters, PtrMYB152 increased Secondary Cell Wall thickness, which is likely caused by increased lignification. Accordingly, elevated expression of genes encoding sets of enzymes in Secondary Wall biosynthesis were observed in transgenic plants expressing PtrMYB152. Arabidopsis protoplast transfection assays suggested that PtrMYB152 functions as a transcriptional activator. Taken together, our results suggest that PtrMYB152 may be part of a regulatory network activating expression of discrete sets of Secondary Cell Wall biosynthesis genes.
-
the interacting myb75 and knat7 transcription factors modulate Secondary Cell Wall deposition both in stems and seed coat in arabidopsis
Planta, 2013Co-Authors: Apurva Bhargava, Shawn D Mansfield, Shucai Wang, Carl J Douglas, Abdul Ahad, George W Haughn, Brian E EllisAbstract:The Arabidopsis thaliana KNAT7 (KNOX family) and MYB75 (MYB family) transcription factors were each shown earlier to interact in yeast two-hybrid assays, and to modulate Secondary Cell Wall formation in inflorescence stems. We demonstrate here that their interaction also occurs in vivo, and that specific domains of each protein mediate this process. The participation of these interacting transcription factors in Secondary Cell Wall formation was then extended to the developing seed coat through the use of targeted transcript analysis and SEM in single loss-of-function mutants. Novel genetic and protein–protein interactions of MYB75 and KNAT7 with other transcription factors known to be involved in seed coat regulation were also identified. We propose that a MYB75-associated protein complex is likely to be involved in modulating Secondary Cell Wall biosynthesis in both the Arabidopsis inflorescence stem and seed coat, and that at least some parts of the transcriptional regulatory network in the two tissues are functionally conserved.
-
myb75 functions in regulation of Secondary Cell Wall formation in the arabidopsis inflorescence stem
Plant Physiology, 2010Co-Authors: Apurva Bhargava, Carl J Douglas, Shawn D Mansfield, Hardy Hall, Brian E EllisAbstract:Deposition of lignified Secondary Cell Walls in plants involves a major commitment of carbon skeletons in both the form of polysaccharides and phenylpropanoid constituents. This process is spatially and temporally regulated by transcription factors, including a number of MYB family transcription factors. MYB75, also called PRODUCTION OF ANTHOCYANIN PIGMENT1, is a known regulator of the anthocyanin branch of the phenylpropanoid pathway in Arabidopsis (Arabidopsis thaliana), but how this regulation might impact other aspects of carbon metabolism is unclear. We established that a loss-of-function mutation in MYB75 (myb75-1) results in increased Cell Wall thickness in xylary and interfascicular fibers within the inflorescence stem. The total lignin content and S/G ratio of the lignin monomers were also affected. Transcript profiles from the myb75-1 inflorescence stem revealed marked up-regulation in the expression of a suite of genes associated with lignin biosynthesis and Cellulose deposition, as well as Cell Wall modifying proteins and genes involved in photosynthesis and carbon assimilation. These patterns suggest that MYB75 acts as a repressor of the lignin branch of the phenylpropanoid pathway. Since MYB75 physically interacts with another Secondary Cell Wall regulator, the KNOX transcription factor KNAT7, these regulatory proteins may form functional complexes that contribute to the regulation of Secondary Cell Wall deposition in the Arabidopsis inflorescence stem and that integrate the metabolic flux through the lignin, flavonoid, and polysaccharide pathways.
-
involvement of pinus taeda myb1 and myb8 in phenylpropanoid metabolism and Secondary Cell Wall biogenesis a comparative in planta analysis
Journal of Experimental Botany, 2008Co-Authors: Claude Bomal, Shawn D Mansfield, Frank Bedon, Sebastien Caron, Caroline Levasseur, Janice E K Cooke, Sylvie Blais, Laurence Tremblay, Mariejosee MorencyAbstract: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.
