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Wall Formation (wall + formation)
Kinds of Wall Formation Selected AbstractsMolecular and Biochemical Evidence for Phenylpropanoid Synthesis and Presence of Wall-linked Phenolics in Cotton FibersJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 7 2009Ling Fan Abstract The mature cotton (Gossypium hirsutum L.) fiber is a single cell with a typically thickened secondary cell wall. The aim of this research was to use molecular, spectroscopic and chemical techniques to investigate the possible occurrence of previously overlooked accumulation of phenolics during secondary cell wall formation in cotton fibers. Relative quantitative reverse transcription-polymerase chain reaction analysis showed that GhCAD6 and GhCAD1 were predominantly expressed among seven gene homologs, only GhCAD6 was up-regulated during secondary wall formation in cotton fibers. Phylogenic analysis revealed that GhCAD6 belonged to Class I and was proposed to have a major role in monolignol biosynthesis, and GhCAD1 belonged to Class III and was proposed to have a compensatory mechanism for monolignol biosynthesis. Amino acid sequence comparison showed that the cofactor binding sites of GhCADs were highly conserved with high similarity and identity to bona fide cinnamyl alcohol dehydrogenases. The substrate binding site of GhCAD1 is different from GhCAD6. This difference was confirmed by the different catalytic activities observed with the enzymes. Cell wall auto-fluorescence, Fourier transform infrared spectroscopy (FTIR), high-performance liquid chromatography (HPLC) and chemical analyses confirmed that phenolic compounds were bound to the cell walls of mature cotton fibers. Our findings may suggest a potential for genetic manipulation of cotton fiber properties, which are of central importance to agricultural, cotton processing and textile industries. [source] Overexpression of EgROP1, a Eucalyptus vascular-expressed Rac-like small GTPase, affects secondary xylem formation in Arabidopsis thalianaNEW PHYTOLOGIST, Issue 4 2009Camille Foucart Summary ,,To better understand the genetic control of secondary xylem formation in trees we analysed genes expressed during Eucalyptus xylem development. ,Using eucalyptus xylem cDNA libraries, we identified EgROP1, a member of the plant ROP family of Rho-like GTPases. These signalling proteins are central regulators of many important processes in plants, but information on their role in xylogenesis is scarce. ,,Quantitative real-time reverse-transcriptase polymerase chain reaction (qRT-PCR) confirmed that EgROP1 was preferentially expressed in the cambial zone and differentiating xylem in eucalyptus. Genetic mapping performed in a eucalyptus breeding population established a link between EgROP1 sequence polymorphisms and quantitative trait loci (QTLs) related to lignin profiles and fibre morphology. Overexpression of various forms of EgROP1 in Arabidopsis thaliana altered anisotropic cell growth in transgenic leaves, but most importantly affected vessel element and fibre growth in secondary xylem. Patches of fibre-like cells in the secondary xylem of transgenic plants showed changes in secondary cell wall thickness, lignin and xylan composition. ,,These results suggest a role for EgROP1 in fibre cell morphology and secondary cell wall formation making it a good candidate gene for marker-based selection of eucalyptus trees. [source] Herbicidal cyanoacrylates with antimicrotubule mechanism of actionPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 11 2005Stefan Tresch Abstract The herbicidal mode of action of the new synthetic cyanoacrylates ethyl (2Z)-3-amino-2-cyano-4-ethylhex-2-enoate (CA1) and its isopropyl ester derivative CA2 was investigated. For initial characterization, a series of bioassays was used indicating a mode of action similar to that of mitotic disrupter herbicides such as the dinitroaniline pendimethalin. Cytochemical fluorescence studies including monoclonal antibodies against polymerized and depolymerized tubulin and a cellulose-binding domain of a bacterial cellulase conjugated to a fluorescent dye were applied to elucidate effects on cell division processes including mitosis and microtubule and cell wall formation in maize roots. When seedlings were root treated with 10 µM of CA1 or CA2, cell division activity in meristematic root tip cells decreased within 4 h. The chromosomes proceeded to a condensed state of prometaphase, but were unable to progress further in the mitotic cycle. The compounds caused a complete loss of microtubular structures, including preprophase, spindle, phragmoplast and cortical microtubules. Concomitantly, in the cytoplasm, an increase in labelling of free tubulin was observed. This suggests that the herbicides disrupt polymerization and microtubule stability, whereas tubulin synthesis or degradation appeared not to be affected. In addition, cellulose labelling in cell walls of root tip cells was not influenced. The effects of CA1 and CA2 were comparable with those caused by pendimethalin. In transgenic Arabidopsis plants expressing a green fluorescent protein-microtubule-associated protein4 fusion protein, labelled arrays of cortical microtubules in living epidermal cells of hypocotyls collapsed within 160 min after exposure to 10 µM CA1 or pendimethalin. Moreover, a dinitroaniline-resistant biotype of goosegrass (Eleusine indica (L) Gaertn) with a point mutation in ,-tubulin showed cross-resistance against CA1 and CA2. The results strongly indicate that the cyanoacrylates are a new chemical class of herbicide which possess the same antimicrotubule mechanism of action as dinitroanilines, probably including interaction with the same binding site in ,-tubulin. Copyright © 2005 Society of Chemical Industry [source] Ultrastructure of the differentiating zygotospores of Porphyra leucosticta (Rhodophyta)PHYCOLOGICAL RESEARCH, Issue 4 2002Ioannes Tsekos SUMMARY The ultrastructure of zygotosporogenesis is described for the red alga Porphyra leucosticta Thuret. Packets of eight zygotosporangia, each packet derived from a single carpogonium are interspersed among vegetative cells. Zygotospore differentiation in Porphyra can be separated into three developmental stages. (i) Young zygotospores exhibit a nucleus and a large centrally located, lobed plastid with pyrenoid. Mucilage is produced within concentric membrane structures during their dilation, thus resulting in the formation of mucilage sacs. Subsequently, these sacs release their contents, initiating the zygotospore wall formation. Straight-profiled dictyosomes produce vesicles that also provide wall material. During the later stages of young zygotospores, starch polymerization commences, (ii) Medium-aged zygotospores are characterized by the presence of fibrous vacuoles. These are formed from the ,fibrous vacuole associated organelles'. The fibrous vacuoles finally discharge their contents. (iii) Mature zygotospores are recognized by the presence of numerous cored vesicles produced by dictyosomes. Cored vesicles either discharge their contents or are incorporated into the fibrous vacuoles. There is a gradual reduction of starch granules during zygotospore differentiation. Mature zygotospores are surrounded by a fibrous wall, have a large chloroplast with pyrenoid and well-depicted phycobilisomes but are devoid of starch granules. [source] Developmental Anatomy and Morphology of the Ovule and Seed of Heliconia (Heliconiaceae, Zingiberales)PLANT BIOLOGY, Issue 1 2006D. G. Simão Abstract: The developmental anatomy and morphology of the ovule and seed in several species of Heliconia were investigated as part of an embryological study of the Heliconiaceae and to provide a better understanding of their relationships with the other families of the Zingiberales. Heliconia species have an ovule primordium with an outer integument of both dermal and subdermal origin. The archesporial cell is divided into a megasporocyte and a single parietal cell, which in turn are divided only anticlinally to form a single parietal layer, disintegrating later during gametogenesis. The embryo sac was fully developed prior to anthesis. In the developing seed, the endosperm was nuclear, with wall formation in the globular stage; a nucellar pad was observed during embryo development, but later became compressed. The ripe fruit contained seeds enveloped by a lignified endocarp that formed the pyrenes, with each pyrene having an operculum at the basal end; the embryo was considered to be differentiated. Most of these characteristics are shared with other Zingiberales, although the derivation of the operculum from the funicle and the formation of the main mechanical layer by the endocarp are unique to the Heliconiaceae. [source] Interrelation between Lignin Deposition and Polysaccharide Matrices during the Assembly of Plant Cell WallsPLANT BIOLOGY, Issue 1 2002K. Ruel Abstract: The modifications caused by genetic down-regulation of the enzyme cinnamoyl CoA reductase (CCR) from monolignol biosynthetic pathways on tobacco and Arabidopsis thaliana were investigated at the ultrastructural level. A typical result was that the same transformation led to similar abnormality in secondary wall formation of fibres in both plants. The cell wall alterations mainly consisted in an important disorganization and loosening of cellulose microfibrils in the inner part of the S2 layer. This inability of the transformants to form a coherent cell wall coincided with a lack of synthesis of non-condensed forms of lignin in this disorganized region of the wall, as demonstrated by immunolabelling of lignin subunits. A similar disorganization was observed during fibre wall formation in the differentiating tissues of young Populus and A. thaliana plants. The transitory lack of organization of cellulose microfibrils, also coincided with a depletion in non-condensed forms of lignins. These results suggest that such lignin substructures may be involved in the cohesion of secondary walls during cell wall biogenesis. The mutual influence of the cellulose-hemicellulose environment and monolignol local polymerization is discussed. [source] Functional dissection of an intrinsically disordered protein: Understanding the roles of different domains of Knr4 protein in protein,protein interactionsPROTEIN SCIENCE, Issue 7 2010Adilia Dagkessamanskaia Abstract Knr4, recently characterized as an intrinsically disordered Saccharomyces cerevisiae protein, participates in cell wall formation and cell cycle regulation. It is constituted of a functional central globular core flanked by a poorly structured N-terminal and large natively unfolded C-terminal domains. Up to now, about 30 different proteins have been reported to physically interact with Knr4. Here, we used an in vivo two-hybrid system approach and an in vitro surface plasmon resonance (BIAcore) technique to compare the interaction level of different Knr4 deletion variants with given protein partners. We demonstrate the indispensability of the N-terminal domain of Knr4 for the interactions. On the other hand, presence of the unstructured C-terminal domain has a negative effect on the interaction strength. In protein interactions networks, the most highly connected proteins or "hubs" are significantly enriched in unstructured regions, and among them the transient hub proteins contain the largest and most highly flexible regions. The results presented here of our analysis of Knr4 protein suggest that these large disordered regions are not always involved in promoting the protein,protein interactions of hub proteins, but in some cases, might rather inhibit them. We propose that this type of regions could prevent unspecific protein interactions, or ensure the correct timing of occurrence of transient interactions, which may be of crucial importance for different signaling and regulation processes. [source] Walls are thin 1 (WAT1), an Arabidopsis homolog of Medicago truncatula NODULIN21, is a tonoplast-localized protein required for secondary wall formation in fibersTHE PLANT JOURNAL, Issue 3 2010Philippe Ranocha Summary By combining Zinnia elegans in vitro tracheary element genomics with reverse genetics in Arabidopsis, we have identified a new upstream component of secondary wall formation in xylary and interfascicular fibers. Walls are thin 1 (WAT1), an Arabidopsis thaliana homolog of Medicago truncatula NODULIN 21 (MtN21), encodes a plant-specific, predicted integral membrane protein, and is a member of the plant drug/metabolite exporter (P-DME) family (transporter classification number: TC 2.A.7.3). Although WAT1 is ubiquitously expressed throughout the plant, its expression is preferentially associated with vascular tissues, including developing xylem vessels and fibers. WAT1:GFP fusion protein analysis demonstrated that WAT1 is localized to the tonoplast. Analysis of wat1 mutants revealed two cell wall-related phenotypes in stems: a defect in cell elongation, resulting in a dwarfed habit and little to no secondary cell walls in fibers. Secondary walls of vessel elements were unaffected by the mutation. The secondary wall phenotype was supported by comparative transcriptomic and metabolomic analyses of wat1 and wild-type stems, as many transcripts and metabolites involved in secondary wall formation were reduced in abundance. Unexpectedly, these experiments also revealed a modification in tryptophan (Trp) and auxin metabolism that might contribute to the wat1 phenotype. Together, our data demonstrate an essential role for the WAT1 tonoplast protein in the control of secondary cell wall formation in fibers. [source] 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 elementsTHE PLANT JOURNAL, Issue 6 2007Hyunjin Pyo Summary 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. [source] Global transcript profiling of primary stems from Arabidopsis thaliana identifies candidate genes for missing links in lignin biosynthesis and transcriptional regulators of fiber differentiationTHE PLANT JOURNAL, Issue 5 2005Jürgen Ehlting Summary Different stages of vascular and interfascicular fiber differentiation can be identified along the axis of bolting stems in Arabidopsis. To gain insights into the metabolic, developmental, and regulatory events that control this pattern, we applied global transcript profiling employing an Arabidopsis full-genome longmer microarray. More than 5000 genes were differentially expressed, among which more than 3000 changed more than twofold, and were placed into eight expression clusters based on polynomial regression models. Within these, 182 upregulated transcription factors represent candidate regulators of fiber development. A subset of these candidates has been associated with fiber development and/or secondary wall formation and lignification in the literature, making them targets for functional studies and comparative genomic analyses with woody plants. Analysis of differentially expressed phenylpropanoid genes identified a set known to be involved in lignin biosynthesis. These were used to anchor co-expression analyses that allowed us to identify candidate genes encoding proteins involved in monolignol transport and monolignol dehydrogenation and polymerization. Similar analyses revealed candidate genes encoding enzymes that catalyze missing links in the shikimate pathway, namely arogenate dehydrogenase and prephenate aminotransferase. [source] | |||||||||||||