Artículos de revistas: "Plant secondary cell walls"

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Avci, Utku. "Trafficking of Xylan to Plant Cell Walls". Biomass 2, n.º 3 (25 de agosto de 2022): 188–94. http://dx.doi.org/10.3390/biomass2030012.

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Plant cell walls are classified as primary and secondary walls. The primary wall is necessary for plant morphogenesis and supports cell growth and expansion. Once the growth and expansion ceases, specialized cells form secondary walls in order to give strength and rigidity to the plant. Secondary cell walls are the main constituent of woody biomass. This biomass is raw material for industrial products, food, and biomaterials. Recently, there are an increasing number of studies using biomass for biofuel production and this area has gained importance. However, there are still many unknowns regarding the synthesis and structure of complex polysaccharides forming biomass. Cellulose, being one of the main components of the cell wall, is synthesized at the plasma membrane by cellulose synthase complexes and does not require transportation. On the other hand, pectin and hemicelluloses are synthesized by enzymes located in the Golgi apparatus. Therefore, they need to be transported to the plasma membrane. Even though this transport mechanism is very important, it is one of the least understood parts of the endomembrane system. Xylan is the major hemicellulose in many biomasses and is important for renewable material production. There is limited knowledge about the cellular trafficking of xylan. In this review, we cover the current information and what we know about the vesicular transport of xylan to the cell wall.

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Wightman, Raymond y Simon Turner. "Digesting the indigestible: Biosynthesis of the plant secondary wall". Biochemist 33, n.º 2 (1 de abril de 2011): 24–28. http://dx.doi.org/10.1042/bio03302024.

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Biofuels have recently been the subject of intense debate with regard to‘food versus fuel’. Consequently, attention has focused upon so-called ‘second-generation’ biofuels that use alternatives to food-based feedstocks. In the best-developed forms of second-generation biofuels, sugars from starch digestion could be replaced with sugars released from the plant cell walls. This biomass could come from either agricultural residue, such as part of the maize culm, or from purpose grown biofuel crops, such as Miscanthus or Switchgrass (Panicum virgatum), that generate huge yields even when grown on marginal land with minimal agricultural inputs. For these and other potential bioenergy crops such as trees, the majority of the plant biomass is composed of woody secondary cell walls. If all cell wall sugars were readily accessible to fermenting micro-organisms, a 5 kg log could theoretically produce up to 2.5 litres of ethanol. The secondary cell walls are frequently the first line of defence against pests and pathogens, as well as providing structure and support for upward plant growth (Figure 1). Consequently, by their very nature, secondary cell walls are designed for strength and to resist degradation. The compact organization of the wall makes its digestion, a process known as saccharification, very difficult so biomass is currently too costly to be a viable feedstock. Knowledge of how the walls are constructed, however, would allow us to efficiently deconstruct them. This article gives an overview of secondary walls and potential modifications expected to be beneficial to improved biofuel production.

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3

Ma, Yingxuan, Luke Stafford, Julian Ratcliffe, Antony Bacic y Kim L. Johnson. "WAKL8 Regulates Arabidopsis Stem Secondary Wall Development". Plants 11, n.º 17 (2 de septiembre de 2022): 2297. http://dx.doi.org/10.3390/plants11172297.

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Wall-associated kinases/kinase-likes (WAKs/WAKLs) are plant cell surface sensors. A variety of studies have revealed the important functions of WAKs/WAKLs in regulating cell expansion and defense in cells with primary cell walls. Less is known about their roles during the development of the secondary cell walls (SCWs) that are present in xylem vessel (XV) and interfascicular fiber (IF) cells. In this study, we used RNA-seq data to screen Arabidopsis thaliana WAKs/WAKLs members that may be involved in SCW development and identified WAKL8 as a candidate. We obtained T-DNA insertion mutants wakl8-1 (inserted at the promoter region) and wakl8-2 (inserted at the first exon) and compared the phenotypes to wild-type (WT) plants. Decreased WAKL8 transcript levels in stems were found in the wakl8-2 mutant plants, and the phenotypes observed included reduced stem length and thinner walls in XV and IFs compared with those in the WT plants. Cell wall analysis showed no significant changes in the crystalline cellulose or lignin content in mutant stems compared with those in the WT. We found that WAKL8 had alternative spliced versions predicted to have only extracellular regions, which may interfere with the function of the full-length version of WAKL8. Our results suggest WAKL8 can regulate SCW thickening in Arabidopsis stems.

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4

Blanchette, Robert A., Kory R. Cease, André R. Abad, Todd A. Burnes y John R. Obst. "Ultrastructural characterization of wood from Tertiary fossil forests in the Canadian Arctic". Canadian Journal of Botany 69, n.º 3 (1 de marzo de 1991): 560–68. http://dx.doi.org/10.1139/b91-076.

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Micromorphological and ultrastructural characterization of fossil gymnosperm wood from Comwallis Island, Axel Heiberg Island, and Ellesmere Island in the Canadian High Arctic showed the changes that have occurred in cell walls of wood during 20–60 million years of burial. No evidence of permineralization was observed. Wood with rounded cells, thick secondary walls, and intercellular spaces was common in all samples. Secondary walls were eroded and swollen. A transition from an organized secondary wall, with altered but visible microfibrillar structure, to an electron-dense, amorphous material was evident in cell walls. The amorphous material appeared to form primarily in the secondary walls near cell lumina and along cracks that extended into the walls. The middle lamellae were often expanded in size and had convoluted shapes. Hemicellulose degradation appeared to precede cellulose degradation. Samples exhibiting cell walls with increased amorphous material had the greatest lignin and lowest cellulose concentrations. Hemicellulose concentration was extremely low in all Eocene and Paleocene samples. The lignin content of Miocene wood was 47.9%, whereas the Eocene and Paleocene samples ranged from 66 to 84%. Tracheids from extensively degraded samples were distorted and collapsed, and in some cases the cells appeared compressed together. Although the residual amorphous middle lamellae and secondary walls were fused together, the outlines of original cells were visible. Chemical analyses and ultrastructural data indicated that a nonbiological degradation was responsible for the deterioration of the arctic fossil wood samples. Key words: wood deterioration, lignin, hemicelluloses, cellulose, wood ultrastructure, coal formation, fossil wood.

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5

Pesquet, Edouard, Andrey V. Korolev, Grant Calder y Clive W. Lloyd. "Mechanisms for shaping, orienting, positioning and patterning plant secondary cell walls". Plant Signaling & Behavior 6, n.º 6 (junio de 2011): 843–49. http://dx.doi.org/10.4161/psb.6.6.15202.

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6

Terrett, Oliver M. y Paul Dupree. "Covalent interactions between lignin and hemicelluloses in plant secondary cell walls". Current Opinion in Biotechnology 56 (abril de 2019): 97–104. http://dx.doi.org/10.1016/j.copbio.2018.10.010.

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7

Busse-Wicher, Marta, Nicholas J. Grantham, Jan J. Lyczakowski, Nino Nikolovski y Paul Dupree. "Xylan decoration patterns and the plant secondary cell wall molecular architecture". Biochemical Society Transactions 44, n.º 1 (9 de febrero de 2016): 74–78. http://dx.doi.org/10.1042/bst20150183.

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The molecular architecture of plant secondary cell walls is still not resolved. There are several proposed structures for cellulose fibrils, the main component of plant cell walls and the conformation of other molecules is even less well known. Glucuronic acid (GlcA) substitution of xylan (GUX) enzymes, in CAZy family glycosyl transferase (GT)8, decorate the xylan backbone with various specific patterns of GlcA. It was recently discovered that dicot xylan has a domain with the side chain decorations distributed on every second unit of the backbone (xylose). If the xylan backbone folds in a similar way to glucan chains in cellulose (2-fold helix), this kind of arrangement may allow the undecorated side of the xylan chain to hydrogen bond with the hydrophilic surface of cellulose microfibrils. MD simulations suggest that such interactions are energetically stable. We discuss the possible role of this xylan decoration pattern in building of the plant cell wall.

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8

Seago, Jr., James L., Carol A. Peterson y Daryl E. Enstone. "Cortical ontogeny in roots of the aquatic plant, Hydrocharis morsus-ranae L." Canadian Journal of Botany 77, n.º 1 (1 de junio de 1999): 113–21. http://dx.doi.org/10.1139/b98-210.

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Tissues in adventitious roots of Hydrocharis morsus-ranae L. developed from a four-tiered apical meristem. A set of periclinal divisions in the outermost layer of the ground meristem produced a hypodermis, which was normally uniformly biseriate. Aerenchyma formed from the adjacent inner layer of the cortex by a series of cell divisions and cell lyses; three- to five-celled, radial aerenchyma strands formed by periclinal divisions in radial cell files 0.3-5 mm behind the apex. Intervening cells underwent anticlinal and periclinal divisions followed by cell lyses within 1 mm of the apex to produce air spaces. Aerenchyma formation in this species is unusual and presents a unique system suitable for a study of developmentally programmed cell death in parenchyma cells. The endodermis formed a complete Casparian band about 10 mm behind the root apex and did not develop further; it had neither suberin lamellae nor secondary walls. The hypodermis was parenchymatous and was without Casparian bands, suberin lamellae, and secondary walls. Following acid digestion, the wavy walls of the endodermis and the walls of the epidermis remained.Key words: aerenchyma, cell death, endodermis, Hydrocharis, hypodermis, root development.

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Idris, Nurul A., Maketelana Aleamotuʻa, David W. McCurdy y David A. Collings. "The Orchid Velamen: A Model System for Studying Patterned Secondary Cell Wall Development?" Plants 10, n.º 7 (2 de julio de 2021): 1358. http://dx.doi.org/10.3390/plants10071358.

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Understanding the mechanisms through which plants generate secondary cell walls is of more than academic interest: the physical properties of plant-derived materials, including timber and textiles, all depend upon secondary wall cellulose organization. Processes controlling cellulose in the secondary cell wall and their reliance on microtubules have been documented in recent decades, but this understanding is complicated, as secondary walls normally form in the plant’s interior where live cell imaging is more difficult. We investigated secondary wall formation in the orchid velamen, a multicellular epidermal layer found around orchid roots that consists of dead cells with lignified secondary cell walls. The patterns of cell wall ridges that form within the velamen vary between different orchid species, but immunolabelling demonstrated that wall deposition is controlled by microtubules. As these patterning events occur at the outer surface of the root, and as orchids are adaptable for tissue culture and genetic manipulation, we conclude that the orchid root velamen may indeed be a suitable model system for studying the organization of the plant cell wall. Notably, roots of the commonly grown orchid Laelia anceps appear ideally suited for developing this research.

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10

Keplinger, Tobias, Johannes Konnerth, Véronique Aguié-Béghin, Markus Rüggeberg, Notburga Gierlinger y Ingo Burgert. "A zoom into the nanoscale texture of secondary cell walls". Plant Methods 10, n.º 1 (2014): 1. http://dx.doi.org/10.1186/1746-4811-10-1.

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11

Spokevicius, Antanas V., Simon G. Southerton, Colleen P. MacMillan, Deyou Qiu, Siming Gan, Josquin F. G. Tibbits, Gavin F. Moran y Gerd Bossinger. "β-tubulin affects cellulose microfibril orientation in plant secondary fibre cell walls". Plant Journal 51, n.º 4 (30 de junio de 2007): 717–26. http://dx.doi.org/10.1111/j.1365-313x.2007.03176.x.

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12

Yoshizawa, Nobuo, Naomi Watanabe, Sbinso Yokota y Tosbinaga Idei. "Distribution of Guaiacyl and Syringyl Lignins in Normal and Compression Wood of Buxus Microphylla Var. Insularis Nakai". IAWA Journal 14, n.º 2 (1993): 139–51. http://dx.doi.org/10.1163/22941932-90001307.

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The distribution of guaiacyl and syringyl lignins in the secondary xylem tissues of normal and compression wood of Buxus microphylla var. insularis Nakai was examined by visible light (VL) microspectrophotometry coupled with the Mäule and Wiesner colour reactions and by UV -microspectrophotometry, and compared with normal wood of Betula ermani Cham. Buxus formed compression wood on the lower side of the leaning sterns, and the secondary walls of the vessels and fibre-tracheids showed excessive lignification, resembling the S2 (L) layer of compression wood tracheids in gymnosperms.In normal wood of both species, the Mäule colour reaction indicated that in Betula the secondary walls of fibres contain larger amounts of syringyl units in the lignins than other tissues, and that in Buxus the secondary walls of fibre-tracheids contain both syringyl and guaiacyl units. The vessel walls of both speeies contained higher amounts of guaiacyl units. Heterogeneity of the syringyl-Jignin distribution was found in the secondary walls of Buxus fibre-tracheids.In compression wood of Buxus, on the other hand, the spectra of the secondary walls of the vessels and fibretracheids after the Mäule reaction showed low absorbances compared with the normal wood, whereas, after the Wiesner reaction, their secondary walls gave high absorbances. In addition, the UV -absorption maximum of the secondary fibre walls shifted from 274 nm to 279 nrn, and the UV -absorbances of the vessei and fibre-tracheid walls greatly increased in compression wood. The results obtained in the present study demonstrated that in normal Buxus wood the secondary walls of the vessels and fibre-tracheids contain both guaiacyl and syringyl units, though the syringyl unit is a rninor constituent in the vessel walls, and that both cell types increase their contents of guaiacyl units, especially in the outer parts of the secondary walls during their changes from normal wood to compression wood. The present study also suggested that the Wiesner reaction may be used for examining the content of lignin and the proportion of guaiacyl to syringyl units in lignins.

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13

Coomey, Joshua H., Richard Sibout y Samuel P. Hazen. "Grass secondary cell walls, Brachypodium distachyon as a model for discovery". New Phytologist 227, n.º 6 (7 de junio de 2020): 1649–67. http://dx.doi.org/10.1111/nph.16603.

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14

Zhai, Shengcheng, Yoshiki Horikawa, Tomoya Imai y Junji Sugiyama. "Cell wall ultrastructure of palm leaf fibers". IAWA Journal 35, n.º 2 (2014): 127–37. http://dx.doi.org/10.1163/22941932-00000054.

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The cell wall organization of leaf sheath fibers in different palm species was studied with polarized light microscopy (PLM) and transmission electron microscopy (TEM). The secondary wall of the fibers consisted of only two layers, S1 and S2. The thickness of the S1 layer in leaf sheath fibers from the different palm species ranged from 0.31 to 0.90 μm, with a mean value of 0.57 μm, which was thicker than that of tracheids and fibers in secondary xylem of conifers and dicotyledons. The thickness of the S2 layer ranged from 0.44 to 3.43 μm, with a mean value of 1.86 μm. The ratio of S1 thickness to the whole cell wall thickness in palm fibers appears to be higher than in secondary xylem fibers and tracheids. The lignin in the fiber walls is very electron dense which makes it difficult to obtain high contrast of the different layers in the secondary wall. To clarify the cell wall layering with cellulose microfibrils in different orientations, the fibrovascular bundles of the windmill palm (Trachycarpus fortunei) were delignified with different reaction time intervals. The treated fibers were surveyed using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy analysis and TEM. The secondary fiber walls of windmill palm clearly showed only two layers at different reaction intervals with different lignin contents, even after almost all lignin was removed. We suggest that the two-layered structure in the secondary wall of palm leaf fibers, which presumably also applies to the homologous fibers in palm stems, is a specific character different from the fibers in other monocotyledons (such as bamboo and rattan) and dicot wood.

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15

Fry, Stephen C., Lenka Franková y Dimitra Chormova. "Setting the boundaries: Primary cell wall synthesis and expansion". Biochemist 33, n.º 2 (1 de abril de 2011): 14–19. http://dx.doi.org/10.1042/bio03302014.

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Mature plant cells typically have two-layered walls: a first-formed thin outer primary wall layer enclosing a later-formed thick inner secondary wall. The surface area of the primary wall limits the size of the cell and thus the maximum amount of biomass that can potentially be accumulated in the secondary wall. By controlling the shape and size of the cell, the primary wall therefore imposes the limits on the amount of inedible biofuel a plant cell can make.

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16

Yokoyama, Ryusuke y Kazuhiko Nishitani. "Identification and characterization of Arabidopsis thaliana genes involved in xylem secondary cell walls". Journal of Plant Research 119, n.º 3 (22 de marzo de 2006): 189–94. http://dx.doi.org/10.1007/s10265-006-0261-7.

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17

Gindl, W., H. S. Gupta y C. Grünwald. "Lignification of spruce tracheid secondary cell walls related to longitudinal hardness and modulus of elasticity using nano-indentation". Canadian Journal of Botany 80, n.º 10 (1 de octubre de 2002): 1029–33. http://dx.doi.org/10.1139/b02-091.

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The lignin content and the mechanical properties of lignifying and fully lignified spruce tracheid secondary cell walls were determined using UV microscopy and nano-indentation, respectively. The average lignin content of developing tracheids was 0.10 g·g1, as compared with 0.21 g·g1 in mature tracheids. The modulus of elasticity of developing cells was on average 22% lower than the one measured in mature, fully lignified cells. For the longitudinal hardness, a larger difference of 26% was observed. As lignifying cells in the cambial zone are undergoing cell wall development, spaces in the cellulosehemicellulose structure are filled with lignin and the density of the cell wall is believed to increase. It is therefore suggested that the observed difference in modulus of elasticity between developing and fully lignified cell walls is due to the filling of spaces with lignin and an increase of the packing density of the cell wall during lignification. Although remarkably less stiff than the composite polysaccharide structure in the secondary cell wall, lignin may be considered equally hard. Therefore, the observed increase in lignin content may contribute directly to the measured increase of hardness.Key words: secondary cell wall, hardness, lignin, modulus of elasticity, wood formation.

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18

Berg, R. Howard y Lorraine McDowell. "Cytochemistry of the wall of infected cells in Casuarina actinorhizae". Canadian Journal of Botany 66, n.º 10 (1 de octubre de 1988): 2038–47. http://dx.doi.org/10.1139/b88-279.

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Development of the wall of infected cells in Casuarina actinorhizae differs from that of many actinorhizae. After the endophyte penetrates the wall of a cortical cell, that (primary) cell wall becomes lignified, based on histochemical (autofluorescence, phloroglucinol staining) and cytochemical (permanganate staining, enzyme etching) evidence. Subsequently, the remaining walls of the infected cell become lignified. Adjacent noninfected cells somehow are stimulated to deposit a lignified secondary wall only on those walls bordering the infected cell. This remarkable participation of all adjacent noninfected cells in the development of a given infected cell results in an increased thickness and strength of the wall material surrounding infected cells. When they mature, there is a further modification of some of the wall layers surrounding infected cells, manifested in a relative impermeability to en bloc staining with permanganate. Unlike lignified walls, the permanganate-impermeable region is selectively stained by osmium or ferricyanide-reduced osmium and is relatively resistant to concentrated chromic acid digestion. A region that remains permeable to (and stained by) permanganate (part of the secondary wall of bordering noninfected cells) may be developmentally related to phi thickenings. An earlier contention that the permanganate-impermeable region contains suberin is unconfirmed. This region is most likely an unusual lignin modification or results from unidentified material impregnated in its ligninlike matrix.

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McCartney, Lesley, Susan E. Marcus y J. Paul Knox. "Monoclonal Antibodies to Plant Cell Wall Xylans and Arabinoxylans". Journal of Histochemistry & Cytochemistry 53, n.º 4 (abril de 2005): 543–46. http://dx.doi.org/10.1369/jhc.4b6578.2005.

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Two rat monoclonal antibodies have been generated to plant cell wall (1→4)-β-D-xylans using a penta-1,4-xylanoside-containing neoglycoprotein as an immunogen. The monoclonal antibodies, designated LM10 and LM11, have different specificities to xylans in relation to the substitution of the xylan backbone as indicated by immunodot assays and competitive-inhibition ELISAs. LM10 is specific to unsubstituted or low-substituted xylans, whereas LM11 binds to wheat arabinoxylan in addition to unsubstituted xylans. Immunocytochemical analyses indicated the presence of both epitopes in secondary cell walls of xylem but differences in occurrence in other cell types.

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20

Domingo, Concepcion, Maria Dolores Gomez, Luis Canas, Jose Hernandez-Yago, Vicente Conejero y Pablo Vera. "A Novel Extracellular Matrix Protein from Tomato Associated with Lignified Secondary Cell Walls". Plant Cell 6, n.º 8 (agosto de 1994): 1035. http://dx.doi.org/10.2307/3869883.

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21

Hoffmann, Natalie, Anika Benske, Heather Betz, Mathias Schuetz y A. Lacey Samuels. "Laccases and Peroxidases Co-Localize in Lignified Secondary Cell Walls throughout Stem Development". Plant Physiology 184, n.º 2 (22 de julio de 2020): 806–22. http://dx.doi.org/10.1104/pp.20.00473.

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Gacias-Amengual, Neus, Lena Wohlschlager, Florian Csarman y Roland Ludwig. "Fluorescent Imaging of Extracellular Fungal Enzymes Bound onto Plant Cell Walls". International Journal of Molecular Sciences 23, n.º 9 (6 de mayo de 2022): 5216. http://dx.doi.org/10.3390/ijms23095216.

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Lignocelluloytic enzymes are industrially applied as biocatalysts for the deconstruction of recalcitrant plant biomass. To study their biocatalytic and physiological function, the assessment of their binding behavior and spatial distribution on lignocellulosic material is a crucial prerequisite. In this study, selected hydrolases and oxidoreductases from the white rot fungus Phanerochaete chrysosporium were localized on model substrates as well as poplar wood by confocal laser scanning microscopy. Two different detection approaches were investigated: direct tagging of the enzymes and tagging specific antibodies generated against the enzymes. Site-directed mutagenesis was employed to introduce a single surface-exposed cysteine residue for the maleimide site-specific conjugation. Specific polyclonal antibodies were produced against the enzymes and were labeled using N-hydroxysuccinimide (NHS) ester as a cross-linker. Both methods allowed the visualization of cell wall-bound enzymes but showed slightly different fluorescent yields. Using native poplar thin sections, we identified the innermost secondary cell wall layer as the preferential attack point for cellulose-degrading enzymes. Alkali pretreatment resulted in a partial delignification and promoted substrate accessibility and enzyme binding. The methods presented in this study are suitable for the visualization of enzymes during catalytic biomass degradation and can be further exploited for interaction studies of lignocellulolytic enzymes in biorefineries.

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Abe, Hisashi y Ryo Funada. "Review — The Orientation of Cellulose Microfibrils in the cell walls of Tracheids in Conifers". IAWA Journal 26, n.º 2 (2005): 161–74. http://dx.doi.org/10.1163/22941932-90000108.

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We examined the orientation of cellulose microfibrils (Mfs) in the cell walls of tracheids in some conifer species by field emission-scanning electron microscopy (FE-SEM) and developed a model on the basis of our observations. Mfs depositing on the primary walls in differentiating tracheids were not well-ordered. The predominant orientation of the Mfs changed from longitudinal to transverse, as the differentiation of tracheids proceeded. The first Mfs to be deposited in the outer layer of the secondary wall (S1 layer) were arranged as an S-helix. Then the orientation of Mfs changed gradually, with rotation in the clockwise direction as viewed from the lumen side of tracheids, from the outermost to the innermost S1 layer. Mfs in the middle layer of the secondary wall (S2 layer) were oriented in a steep Z-helix with a deviation of less than 15° within the layer. The orientation of Mfs in the inner layer of the secondary wall (S3 layer) changed, with rotation in a counterclockwise direction as viewed from the lumen side, from the outermost to the innermost S3 layer. The angle of orientation of Mfs that were deposited on the innermost S3 layer varied among tracheids from 40° in a Z-helix to 20° in an S-helix.

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Chukhchin, Dmitry G., Ksenia Vashukova y Evgeniy Novozhilov. "Bordered Pit Formation in Cell Walls of Spruce Tracheids". Plants 10, n.º 9 (21 de septiembre de 2021): 1968. http://dx.doi.org/10.3390/plants10091968.

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The process of pit formation in plants still has various questions unaddressed and unknown, which opens up many interesting and new research opportunities. The aim of this work was elucidation of the mechanism for the formation of bordered pits of the spruce (Picea abies (L.) Karst.) tracheid with exosomes participation and mechanical deformation of the cell wall. Sample sections were prepared from spruce stem samples after cryomechanical destruction with liquid nitrogen. The study methods included scanning electron microscopy and enzymatic treatment. Enzymatic treatment of the elements of the bordered pit made it possible to clarify the localization of cellulose and pectin. SEM images of intermediate stages of bordered pit formation in the radial and tangential directions were obtained. An asynchronous mechanism of formation of bordered-pit pairs in tracheids is proposed. The formation of the pit pair begins from the side of the initiator cell and is associated with enzymatic hydrolysis of the secondary cell wall and subsequent mechanical deformation of the primary cell walls. Enzymatic hydrolysis of the S1 layer of the secondary cell wall is carried out by exosome-delivered endoglucanases.

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Yi Chou, Eva, Mathias Schuetz, Natalie Hoffmann, Yoichiro Watanabe, Richard Sibout y A. Lacey Samuels. "Distribution, mobility, and anchoring of lignin-related oxidative enzymes in Arabidopsis secondary cell walls". Journal of Experimental Botany 69, n.º 8 (22 de febrero de 2018): 1849–59. http://dx.doi.org/10.1093/jxb/ery067.

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Putoczki, Tracy L., Juliet A. Gerrard, Brian G. Butterfield y Sandra L. Jackson. "The Distribution of un-esterified and Methyl-Esterified Pectic Polysaccharides in Pinus Radiata". IAWA Journal 29, n.º 2 (2008): 115–27. http://dx.doi.org/10.1163/22941932-90000173.

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A cationic dye which binds acidic polymers such as pectin and monoclonal antibodies, directed against un-esterified and methyl-esterified (JIM5) and only methyl-esterified (JIM7) pectin epitopes, were used, in conjunction with light microscopy, confocal microscopy and immunogold electron microscopy, to study the spatial distribution of pectin in the xylem tissue of Pinus radiata D. Don. Histochemistry demonstrated that pectin was located in the compound middle lamella (CML) of the maturing tracheid cell wall, in addition to the pit membranes and the CML of the ray cell walls. Immunogold labeling showed differential distribution of the pectin epitopes within the CML of the maturing cell walls. Moreover, in the xylem, the JIM5 and JIM7 epitopes were found to be restricted to distinct tissues. Neither epitope occurred in the secondary walls of the xylem cells. These patterns of epitope expression were not maintained in the mature cell. These results represent the first demonstration of restricted spatial patterns of distribution of these epitopes in the xylem tissue of radiata pine and are consistent with results from other coniferous gymnosperms.

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Ito, Hiroaki, Kuniko Nishikawa, Tatsuya Awano, Munetaka Hosokawa y Susumu Yazawa. "Secondary Cell Walls at a Scarious Floral Leaf in Several Plant Species Including Helichrysum bracteatum". Horticultural Research (Japan) 9, n.º 1 (2010): 19–23. http://dx.doi.org/10.2503/hrj.9.19.

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Dang, Xiaofei, Bei Zhang, Chen Li y Shingo Nagawa. "FvNST1b NAC Protein Induces Secondary Cell Wall Formation in Strawberry". International Journal of Molecular Sciences 23, n.º 21 (30 de octubre de 2022): 13212. http://dx.doi.org/10.3390/ijms232113212.

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Secondary cell wall thickening plays a crucial role in plant growth and development. Diploid woodland strawberry (Fragaria vesca) is an excellent model for studying fruit development, but its molecular control of secondary wall thickening is largely unknown. Previous studies have shown that Arabidopsis NAC secondary wall thickening promoting factor1 (AtNST1) and related proteins are master regulators of xylem fiber cell differentiation in multiple plant species. In this study, a NST1-like gene, FvNST1b, was isolated and characterized from strawberry. Sequence alignment and phylogenetic analysis showed that the FvNST1b protein contains a highly conserved NAC domain, and it belongs to the same family as AtNST1. Overexpression of FvNST1b in wild-type Arabidopsis caused extreme dwarfism, induced ectopic thickening of secondary walls in various tissues, and upregulated the expression of genes related to secondary cell wall synthesis. In addition, transient overexpression of FvNST1b in wild-type Fragaria vesca fruit produced cells resembling tracheary elements. These results suggest that FvNST1b positively regulates secondary cell wall formation as orthologous genes from other species.

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29

Zhang, Qian, Fang Luo, Yu Zhong, Jiajia He y Laigeng Li. "Modulation of NAC transcription factor NST1 activity by XYLEM NAC DOMAIN1 regulates secondary cell wall formation in Arabidopsis". Journal of Experimental Botany 71, n.º 4 (19 de noviembre de 2019): 1449–58. http://dx.doi.org/10.1093/jxb/erz513.

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Abstract In Arabidopsis, secondary cell walls (SCW) are formed in fiber cells and vessel cells in vascular tissue for providing plants with mechanical strength and channels for the long distance transportation of water and nutrients. NAC SECONDARY WALL THICKENING PROMOTING FACTOR1 (NST1) acts as a key gene for the initiation of SCW formation through a hierarchical transcription network. In this study, we report that NST activity is modulated by the NAC domain transcription factor XYLEM NAC DOMAIN1 (XND1) during plant growth. Using yeast two-hybrid screening and in vivo protein interaction analysis, XND1 was identified as an NST-interacting protein that modulates NST1 activity. XND1 and NST1 were co-localized in the nucleus and the interaction of XND1 with NST1 resulted in inhibition of NST1 transactivation activity. In the process of inflorescence growth, XND1 was expressed with a similar pattern to NST1. Up-regulation of XND1 in fiber cells repressed SCW formation. The study demonstrates that NST1 activity is modulated by XND1 in the regulation of secondary cell walls formation.

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30

Shomer, Ilan, Edo Chalutz, Rosa Vasiliver, Ella Lomaniec y Monica Berman. "Scierification of juice sacs in pummelo (Citrus grandis) fruit". Canadian Journal of Botany 67, n.º 3 (1 de marzo de 1989): 625–32. http://dx.doi.org/10.1139/b89-084.

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Granulation of juice sacs in pummelo (Citrus grandis L.) fruit was found to occur upon ripening. The juice sac tissue consisted of epidermal and subepidermal cell layers, an elongated cell layer, and juice cells. The granulation was accompanied by the appearance of opaque white regions inside transparent tissue. The subepidermal cells of the granulated tissue were disordered and the cell walls of the elongated and the juice cells were distinctly thickened. An ultrastructural study has shown that the subepidermal cell walls of granulated juice sacs were distorted and had swollen regions. The cell walls of both the elongated and the juice cells had secondary thickening with pits. The total dry weight, cellulose (as glucose), lignin, and hemicellulose (as xylose) were significantly higher and insoluble proteins were lower in granulated juice sacs than in non-granulated ones. The content of insoluble neutral sugars such as rhamnose, arabinose, mannose, and galactose decreased as a result of granulation, as did that of soluble sugars glucose, fructose, sucrose, and organic acids. Thus, it seems that granulation of pummelo fruit juice sacs is a result of lignification of the juice cells, which leads to the formation of sclerenchyma.

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31

Weis, K. y V. S. Polito. "Cytochemistry and ultrastructure of the dehiscence zone of almond (Prunus dulcis) fruits". Canadian Journal of Botany 68, n.º 1 (1 de enero de 1990): 63–72. http://dx.doi.org/10.1139/b90-010.

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At maturity, the almond pericarp dehisces along the ventral suture, a region that originates by fusion of epidermal cells and subsequently differentiates into a separation layer. We have characterized the ontogeny of the fusion–dehiscence zone with emphasis on cell wall characteristics by using cytochemical methods for detection of pectin, cutin, cellulose, and lignin to examine the middle lamellae and primary and secondary walls in dehiscence-zone cells. Carpel margins became united postgenitally along opposing epidermal layers giving rise to the suture. Fusion-zone cells host epidermal characteristics, elaborated broad pectinaceous walls, and ultimately formed a discrete band of cells that dehisced along the original line of fusion by dissolution of cell wall pectins. Treatment of treeborne fruits with 1 ppm ethylene gas or extraction of sectioned material with cell wall hydrolases resulted in cell wall changes similar to those in predehiscent fruits.

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32

Li, Shundai, Logan Bashline, Yunzhen Zheng, Xiaoran Xin, Shixin Huang, Zhaosheng Kong, Seong H. Kim, Daniel J. Cosgrove y Ying Gu. "Cellulose synthase complexes act in a concerted fashion to synthesize highly aggregated cellulose in secondary cell walls of plants". Proceedings of the National Academy of Sciences 113, n.º 40 (19 de septiembre de 2016): 11348–53. http://dx.doi.org/10.1073/pnas.1613273113.

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Cellulose, often touted as the most abundant biopolymer on Earth, is a critical component of the plant cell wall and is synthesized by plasma membrane-spanning cellulose synthase (CESA) enzymes, which in plants are organized into rosette-like CESA complexes (CSCs). Plants construct two types of cell walls, primary cell walls (PCWs) and secondary cell walls (SCWs), which differ in composition, structure, and purpose. Cellulose in PCWs and SCWs is chemically identical but has different physical characteristics. During PCW synthesis, multiple dispersed CSCs move along a shared linear track in opposing directions while synthesizing cellulose microfibrils with low aggregation. In contrast, during SCW synthesis, we observed swaths of densely arranged CSCs that moved in the same direction along tracks while synthesizing cellulose microfibrils that became highly aggregated. Our data support a model in which distinct spatiotemporal features of active CSCs during PCW and SCW synthesis contribute to the formation of cellulose with distinct structure and organization in PCWs and SCWs of Arabidopsis thaliana. This study provides a foundation for understanding differences in the formation, structure, and organization of cellulose in PCWs and SCWs.

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33

Mamoňová, Miroslava y Ladislav Reinprecht. "The impact of natural and artificial weathering on the anatomy of selected tropical hardwoods". IAWA Journal 41, n.º 3 (28 de julio de 2020): 333–55. http://dx.doi.org/10.1163/22941932-bja10028.

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Abstract The effect of natural and artificial weathering on the anatomy of seven tropical hardwoods: Bangkirai (Shorea obtusa Wall.), Cumaru (Dipteryx odorata (Aubl.) Wild.), Cumaru Rosa (Dipteryx magnifica (Ducke) Ducke), Ipé (Tabebuia serratifolia Nichols.), Jatobá (Hymenaea courbaril L.), Kusia (Nauclea diderrichii Merill) and Massaranduba (Manilkara bidentata A. Chev.), was studied. As a result of weathering some characteristic anatomical changes occurred: the weakening of connections between cell elements related to the degradation of the middle lamella; micro-cracks in cell walls; total degradation of parenchyma cells in xylem rays, or significant thinning of parenchyma cell walls and their extreme shrinkage; micro-cracks in the vicinity of xylem rays; significant transversal disruptions in libriform fibres; ablation of pit membranes in vessels and parenchyma cells; changes in the secondary wall of libriform fibres, for example, their defibrillation and weathering-degradation of the S1 layer; and spherical formations on the S3 layer of cell walls produced from condensing compounds of degraded lignin and hemicelluloses as well as thermo-mechanical wrinkling. The highest incidence of micro-cracks after both modes of weathering was found in the densest species; Cumaru, Ipé, and Massaranduba.

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34

De Micco, Veronica, Katia Ruel, Jean-Paul Joseleau, Jacqueline Grima-Pettenati y Giovanna Aronne. "Xylem Anatomy and Cell Wall Ultrastructure of Nicotiana Tabacum After Lignin Genetic Modification Through Transcriptional Activator EgMYB2". IAWA Journal 33, n.º 3 (2012): 269–86. http://dx.doi.org/10.1163/22941932-90000093.

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The transcriptional activator EgMYB2, which belongs to the large R2R3 MYB transcription factor family, plays a major role in the coordinated control of genes in the lignin biosynthetic pathway. Given that lignin genetic modification can lead to xylem alterations compromising vascular functionality, we characterised wood anatomical properties of two transgenic tobacco lines over-expressing EgMYB2, using light, fluorescence, confocal, transmission electron microscopy, immunocytochemical labelling and digital image analysis. Transgenic wood, compared with wild type, was characterised by both reduced frequency of larger vessels and lower vessel grouping; these traits are known to have physiological implications in terms of water transport efficiency and safety against embolism. Transgenic wood also appeared denser due to the occurrence of thicker cell walls and higher incidence of fibres than wild type. Increased lignin content was accompanied by a concomitant increase in cellulose and xylan, but no alterations in the usual distribution of guaiacyl and syringyl units in secondary cell walls were observed. Altogether, these results show that EgMYB2 is a master regulator controlling the synthesis of the three major polymers of the secondary cell wall and that its overexpression has significant influence on quantitative anatomical traits of wood which affect its functional properties.

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35

Gillet, C. y F. Liners. "Changes in distribution of short pectic polysaccharides induced by monovalent ions in the Nitella cell wall". Canadian Journal of Botany 74, n.º 1 (1 de enero de 1996): 26–30. http://dx.doi.org/10.1139/b96-004.

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Nitella cell walls exhibit a major loss of pectin when the adsorbed bivalent ions are exchanged for monovalents. 2F4 monoclonal antibody, which recognizes a conformational epitope of homogalacturonic acid induced by calcium ions, was complexed to colloidal gold and used to localize, by means of the electron microscope, the wall regions from which the leakage occurred. Comparison of the labelling between nonpretreated cell walls and NaCl or LiCl pretreated ones, with or without incubation in CDTA or in NaOH, reveals that monovalent ions induce the solubilization of a pectic fraction rich in nonesterified galacturonic acids from the primary wall. Our results also indicate that in the secondary wall of Nitella, the pectic polysaccharides could be closely joined by covalent crosslinking. Keywords: pectin, gold labelling, monoclonal antibody, ionic exchange, Nitella.

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36

Ma, Jianfeng, Zhe Ji, Xia Zhou, Zhiheng Zhang y Feng Xu. "Transmission Electron Microscopy, Fluorescence Microscopy, and Confocal Raman Microscopic Analysis of Ultrastructural and Compositional Heterogeneity of Cornus alba L. Wood Cell Wall". Microscopy and Microanalysis 19, n.º 1 (febrero de 2013): 243–53. http://dx.doi.org/10.1017/s1431927612013906.

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AbstractTransmission electron microscopy (TEM), fluorescence microscopy, and confocal Raman microscopy can be used to characterize ultrastructural and compositional heterogeneity of plant cell walls. In this study, TEM observations revealed the ultrastructural characterization of Cornus alba L. fiber, vessel, axial parenchyma, ray parenchyma, and pit membrane between cells, notably with the ray parenchyma consisting of two well-defined layers. Fluorescence microscopy evidenced that cell corner middle lamella was more lignified than adjacent compound middle lamella and secondary wall with variation in lignification level from cell to cell. In situ Raman images showed that the inhomogeneity in cell wall components (cellulose and lignin) among different cells and within morphologically distinct cell wall layers. As the significant precursors of lignin biosynthesis, the pattern of coniferyl alcohol and aldehyde (joint abbreviation Lignin-CAA for both structures) distribution in fiber cell wall was also identified by Raman images, with higher concentration occurring in the fiber secondary wall where there was the highest cellulose concentration. Moreover, noteworthy was the observation that higher concentration of lignin and very minor amounts of cellulose were visualized in the pit membrane areas. These complementary microanalytical methods provide more accurate and complete information with regard to ultrastructural and compositional characterization of plant cell walls.

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37

Tomlinson, P. B. "REACTION TISSUES IN GNETUM GNEMON A PRELIMINARY REPORT". IAWA Journal 22, n.º 4 (2001): 401–13. http://dx.doi.org/10.1163/22941932-90000385.

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Gnetum gnemon exhibits Rouxʼs model of tree architecture, with clear differentiation of orthotropic from plagiotropic axes. All axes have similar anatomy and react to displacement in the same way. Secondary xylem of displaced stems shows little eccentricity of development and no reaction anatomy. In contrast, there is considerable eccentricity in extra-xylary tissue involving both primary and secondary production of apparent tension-wood fibres (gelatinous fibres) of three main kinds. Narrow primary fibres occur concentrically in all axes in the outer cortex as a normal developmental feature. In displaced axes gelatinous fibres are developed abundantly and eccentrically on the topographically upper side, from pre-existing and previously undetermined primary cortical cells. They are wide with lamellate cell walls. In addition narrow secondary phloem fibres are also differentiated abundantly and eccentrically on the upper side of displaced axes. These gelatinous fibres are narrow and without obviously lamellate cell walls. Eccentric gelatinous fibres thus occupy a position that suggests they have the function of tension wood fibres as found in angiosperms. This may be the first report in a gymnosperm of fibres with tension capability. Gnetum gne-mon thus exhibits reaction tissues of unique types, which are neither gymnospermous nor angiospermous. Reaction tissues seem important in maintaining the distinctive architecture of the tree.

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38

Bosman, M. T. M. "Some Effects of Decay and Weathering on the Anatomical Structure of the Stem of Phragmites Australis Trin. Ex Steud." IAWA Journal 6, n.º 2 (1985): 165–70. http://dx.doi.org/10.1163/22941932-90000929.

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Effects of decay and weathering on the stems of Phragmites australis Trin. ex Steud. were studied on material used for thatching. Decay appeared to be mainly a result of fungal attack and ultra-violet radiation. Biological degradation by soft-rot fungi causes a considerable loss of cell wall constituents towards the exposed basal part of the stems. In sclerenchyma and parenchyma (excl. the subepidermal tissues) this effect is visible as diamond-shaped cavities, spirally arranged in the central part of the secondary cell walls (following the microfibrillar arrangement). A second type of fungal attack is observed in stems obtained from a byre. Here the cell walls are thinned from the lumen side towards the external wall layers, showing in longitudinal section cells with locally enlarged lumina. At the exposed parts of the stem superficial weathering by ultra-violet radiation causes degradation of lignin. Thus the middle lamella region disintegrates and the outer cell layers peel off.

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39

Teixeira, Rita Teresa y Helena Pereira. "Suberized Cell Walls of Cork from Cork Oak Differ from Other Species". Microscopy and Microanalysis 16, n.º 5 (31 de agosto de 2010): 569–75. http://dx.doi.org/10.1017/s1431927610093839.

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AbstractPlants have suberized cells that act as protective interfaces with the environment or between different plant tissues. A lamellar structure of alternating dark and light bands has been found upon transmission electron microscopy (TEM) observation of cork cells and considered a typical feature of the suberized secondary wall. We observed cork cells from periderms of Quercus suber, Quercus cerris, Solanum tuberosum, and Calotropis procera by TEM after uranyl acetate and lead citrate staining. A lamellated structure was observed in S. tuberosum and C. procera but not in Q. suber and Q. cerris where the suberized cell wall showed a predominantly hyaline aspect with only a dark dotted staining. Removal of suberin from Q. suber cells left a thinner secondary wall that lost the translucent aspect. We hypothesize that the species' specific chemical composition of suberin will result in different three-dimensional macromolecular development and in a different spatial location of lignin and other aromatics. A lamellated ultrastructure is therefore not a general feature of suberized cells.

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40

Carlquist, Sherwin. "Wood and Bark Anatomy of Caricaceae; Correlations with Systematics and Habit". IAWA Journal 19, n.º 2 (1998): 191–206. http://dx.doi.org/10.1163/22941932-90001522.

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Wood and bark anatomy are described for four species of three genera of Caricaceae; both root and stem material were available for Jacaratia hassleriana. Wood of all species lacks libriform fibers in secondary xylem, and has axial parenchyma instead. Cylicomorpha parviflora has paratracheal parenchyma cells with thin lignified walls; otherwise, all cell walls of secondary xylem in Caricaceae except those of vessels have only primary walls. Vessels have alternate laterally elongate (pseudoscalariform) pits on vessel-vessel interfaces, but wide, minimally bordered scalariform pits on vessel-parenchyma contacts. Laticifers occur commonly in tangential plates in fascicular secondary xylem, and rarely in xylem rays. Proliferation of axial parenchyma by zones of tangential divisions is newly reported for the family. Bark is diverse in the species, although some features (e.g., druses) are common to all. Wood of Caricaceae is compared to that of two species of Moringaceae, recently designated the sister family of Caricaceae. Although the wood and bark of Moringa oleifera, a treelike species, differ from those of Caricaceae, wood and bark of the stem succulent M. hildebrandtii, the habit of which resembles those in Caricaceae, simulate wood and bark of Caricaceae closely. Counterparts to laticifers in Moringaceae are uncertain, however. Phloem fibers of Caricaceae form an expansible peripheral cylinder of mechanical tissue that correlates with the stem succulence of most species of Caricaceae.

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41

Čufar, Katarina, Jožica Gričar, Martin Zupančič, Gerald Koch y Uwe Schmitt. "Anatomy, Cell Wall Structure and Topochemistry of Water-Logged Archaeological wood aged 5,200 and 4,500 years". IAWA Journal 29, n.º 1 (2008): 55–68. http://dx.doi.org/10.1163/22941932-90000170.

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Evaluating the state of deterioration of water-logged archaeological wood is necessary in order to select treatments for its conservation and storage, particularly in the case of valuable archaeological artefacts. For this purpose archaeological wood of ash (Fraxinus sp.) and oak (Quercus sp.) buried in water-logged conditions at prehistoric settlements on the Ljubljansko barje (Ljubljana moor), Slovenia, aged approx. 5,200 and 4,500 years, was investigated by means of light microscopy (LM), transmission electron microscopy (TEM) and cellular UV-microspectrophotometry (UMSP). LM and TEM revealed that the ash wood aged 5,200 years was the least preserved. The secondary walls of fibres, vessels and parenchyma cells were considerably thinner than in normal wood, indicating distinct degradation. TEM and UMSP additionally revealed strong delignification of the remaining parts of the secondary walls of all cell types. The compound middle lamellae appeared structurally intact, but had lower UV-absorbance than normal wood of the same species. The cell corners were topochemically unchanged, as shown by high analogue UV-absorbance. The UV-absorbance maxima at a wavelength of 278 nm corresponded to those of hardwood lignins. The oak heartwood was generally better preserved than the ash wood. Within each species, the 4,500- year-old samples generally appeared better preserved than those 5,200 years old.

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42

Ben’ko, Elena M., Dmitriy G. Chukhchin y Valeriy V. Lunin. "Changes in wheat straw cell walls during ozone pretreatment". Holzforschung 74, n.º 12 (18 de noviembre de 2020): 1157–67. http://dx.doi.org/10.1515/hf-2019-0168.

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AbstractTreatment of plant biomass with ozone is a promising delignification method. It was shown that lignin removal from the cell wall during ozonation was limited by topochemical reactions and toke place in the secondary rather in the primary cell wall. The separation of cellulose microfibrils, the loss of cell wall stiffness and complete removal of intercellular substance during the delignification process were visualized by SEM. The dependence of the average diameter of the cellulose microfibril aggregates in the cell wall of ozonized straw on ozone consumption was studied. Lignin removal caused an increase of size of cellulose microfibrils aggregates. It was demonstrated that there was an optimal degree of delignification, at which cellulose became more accessible to enzymes in the subsequent bioconversion processes. The data on the ozone consumption, residual lignin content, and sugars yield in the enzymatic hydrolysis of ozonized wheat straw were obtained. It was also found that the optimum delignification degree for sugars yield was ≈10% of residual lignin content and optimum ozone consumption was 2 mol·О3/mol C9PPU (phenylpropane structural unit) of lignin in raw straw.

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43

Baldacci-Cresp, Fabien, Julien Le Roy, Brigitte Huss, Cédric Lion, Anne Créach, Corentin Spriet, Ludovic Duponchel et al. "UDP-GLYCOSYLTRANSFERASE 72E3 Plays a Role in Lignification of Secondary Cell Walls in Arabidopsis". International Journal of Molecular Sciences 21, n.º 17 (24 de agosto de 2020): 6094. http://dx.doi.org/10.3390/ijms21176094.

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Lignin is present in plant secondary cell walls and is among the most abundant biological polymers on Earth. In this work we investigated the potential role of the UGT72E gene family in regulating lignification in Arabidopsis. Chemical determination of floral stem lignin contents in ugt72e1, ugt72e2, and ugt72e3 mutants revealed no significant differences compared to WT plants. In contrast, the use of a novel safranin O ratiometric imaging technique indicated a significant increase in the cell wall lignin content of both interfascicular fibers and xylem from young regions of ugt72e3 mutant floral stems. These results were globally confirmed in interfascicular fibers by Raman microspectroscopy. Subsequent investigation using a bioorthogonal triple labelling strategy suggested that the augmentation in lignification was associated with an increased capacity of mutant cell walls to incorporate H-, G-, and S-monolignol reporters. Expression analysis showed that this increase was associated with an up-regulation of LAC17 and PRX71, which play a key role in lignin polymerization. Altogether, these results suggest that UGT72E3 can influence the kinetics of lignin deposition by regulating monolignol flow to the cell wall as well as the potential of this compartment to incorporate monomers into the growing lignin polymer.

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44

Altaner, Clemens M., Michael C. Jarvis, Jack B. Fisher y Thomas E. Marler. "Molecular xylem cell wall structure of an inclined Cycas micronesica stem, a tropical gymnosperm". IAWA Journal 31, n.º 1 (2010): 3–11. http://dx.doi.org/10.1163/22941932-90000001.

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The molecular structure of tracheid walls of an inclined eccentrically grown stem of Cycas micronesica K.D. Hill did not differ between the upper and lower side. The absence the typical molecular features of compression wood tracheids, i.e. an increased galactose and lignin content as well as an increased microfibril angle, indicated that cycads do not have the ability to form even very mild forms of compression wood, which lacks anatomical features commonly observed in compression wood. Analysis of the sugar monomers in Cycas micronesica tracheids did reveal a rather unique composition of the non-cellulosic polysaccharides for a gymnosperm. The low mannose and high xylose content resembled a cell wall matrix common in angiosperms. The crystalline cellulose structure in Cycas micronesica tracheids closely resembled those of secondary cell walls in Picea sitchensis (Bong.) Carr. tracheids. However, the spacing between the sheets of cellulose chains was wider and the cellulose fibrils appeared to form larger aggregates than in Sitka spruce tracheids.

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45

Qin, Wenqi, Qi Yin, Jiajun Chen, Xianhai Zhao, Fengxia Yue, Junbo He, Linjie Yang et al. "The class II KNOX transcription factors KNAT3 and KNAT7 synergistically regulate monolignol biosynthesis in Arabidopsis". Journal of Experimental Botany 71, n.º 18 (31 de mayo de 2020): 5469–83. http://dx.doi.org/10.1093/jxb/eraa266.

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Abstract The function of the transcription factor KNOTTED ARABIDOPSIS THALIANA7 (KNAT7) is still unclear since it appears to be either a negative or a positive regulator for secondary cell wall deposition with its loss-of-function mutant displaying thicker interfascicular and xylary fiber cell walls but thinner vessel cell walls in inflorescence stems. To explore the exact function of KNAT7, class II KNOTTED1-LIKE HOMEOBOX (KNOX II) genes in Arabidopsis including KNAT3, KNAT4, and KNAT5 were studied together. By chimeric repressor technology, we found that both KNAT3 and KNAT7 repressors exhibited a similar dwarf phenotype. Both KNAT3 and KNAT7 genes were expressed in the inflorescence stems and the knat3 knat7 double mutant exhibited a dwarf phenotype similar to the repressor lines. A stem cross-section of knat3 knat7 displayed an enhanced irregular xylem phenotype as compared with the single mutants, and its cell wall thickness in xylem vessels and interfascicular fibers was significantly reduced. Analysis of cell wall chemical composition revealed that syringyl lignin was significantly decreased while guaiacyl lignin was increased in the knat3 knat7 double mutant. Coincidently, the knat3 knat7 transcriptome showed that most lignin pathway genes were activated, whereas the syringyl lignin-related gene Ferulate 5-Hydroxylase (F5H) was down-regulated. Protein interaction analysis revealed that KNAT3 and KNAT7 can form a heterodimer, and KNAT3, but not KNAT7, can interact with the key secondary cell wall formation transcription factors NST1/2, which suggests that the KNAT3–NST1/2 heterodimer complex regulates F5H to promote syringyl lignin synthesis. These results indicate that KNAT3 and KNAT7 synergistically work together to promote secondary cell wall biosynthesis.

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46

Girault, Raynald, Isabelle His, Christine Andeme-Onzighi, Azeddine Driouich y Claudine Morvan. "Identification and partial characterization of proteins and proteoglycans encrusting the secondary cell walls of flax fibres". Planta 211, n.º 2 (14 de julio de 2000): 256–64. http://dx.doi.org/10.1007/s004250000281.

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47

Aleamotu‘a, Maketalena, David W. McCurdy y David A. Collings. "Phi thickenings in roots: novel secondary wall structures responsive to biotic and abiotic stresses". Journal of Experimental Botany 70, n.º 18 (18 de mayo de 2019): 4631–42. http://dx.doi.org/10.1093/jxb/erz240.

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Abstract Phi thickenings are specialized secondary walls found in root cortical cells. Despite their widespread occurrence throughout the plant kingdom, these specialized thickenings remain poorly understood. First identified by Van Tieghem in 1871, phi thickenings are a lignified and thickened cell wall band that is deposited inside the primary wall, as a ring around the cells’ radial walls. Phi thickenings can, however, display structural variations including a fine, reticulate network of wall thickenings extending laterally from the central lignified band. While phi thickenings have been proposed to mechanically strengthen roots, act as a permeability barrier to modulate solute movement, and regulate fungal interactions, these possibilities remain to be experimentally confirmed. Furthermore, since temporal and spatial development of phi thickenings varies widely between species, thickenings may perform diverse roles in different species. Phi thickenings can be induced by abiotic stresses in different species; they can, for example, be induced by heavy metals in the Zn/Cd hyperaccumulator Thlaspi caerulescens, and in a cultivar-specific manner by water stress in Brassica. This latter observation provides an experimental platform to probe phi thickening function, and to identify genetic pathways responsible for their formation. These pathways might be expected to differ from those involved in secondary wall formation in xylem, since phi thickening deposition in not linked to programmed cell death.

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48

Ouellette, G. B., R. P. Baayen, M. Simard y D. Rioux. "Ultrastructural and cytochemical study of colonization of xylem vessel elements of susceptible and resistant Dianthus caryophyllus by Fusarium oxysporum f.sp. dianthi". Canadian Journal of Botany 77, n.º 5 (16 de octubre de 1999): 644–63. http://dx.doi.org/10.1139/b99-033.

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The colonization processes of the xylem in the susceptible carnation cv. Early Sam and the resistant cv. Novada were studied ultrastructurally following inoculation with Fusarium oxysporum f.sp. dianthi. Samples from 1 to 3 cm above the incision were collected over 5 weeks and processed following conventional procedures as well as with probes for cellulose, N-acetyl-glucosamine, and pectin. The fungus grew profusely in the vessel lumina of the susceptible cultivar. Some of the colonized vessels were lined with coating material connected to the fungal cell wall and extending into the host cell wall through microfilamentous-like structures. Coatings did not label for pectin or cellulose. The pathogen crossed from one vessel element to another (and at times to parenchyma cells) usually directly through pit membranes; often the invading structures of the fungus appeared to be either only membrane-bound or formed solely of microfilamentous-like entities. The fungus subsequently invaded extensively, generally by means of microhyphae, the vessel intercalary walls from the pit membranes and vessel wall junctures. Microhyphae had thin or imperceptible walls and contained only some of the normal cytoplasmic components. Initially, the invading hyphae dislocated the host cell walls, apparently mechanically more than by lysis; however, more pronounced lysis occurred following general tissue invasion. Host parenchyma cells seemed relatively unaffected, even after the surrounding walls had undergone severe degradation. Colonization of resistant plants was restricted. Degradation of tissues did not occur and microhyphae were not observed. Inoculated vessel elements in the 'Novada' plants contained numerous fungal cells and little occluding material, whereas the surrounding vessels were almost completely occluded. The initially invaded xylem became tangentially compartmentalized by parenchyma cell wall thickenings and by hyperplastic parenchyma. Occasionally, hyperplastic tissues were slightly re-invaded, forming secondary invasion pockets. Vessel-occluding material varied in structure and opacity, not only from vessel to vessel but also within the same vessel, and contained microfilamentous-like structures and other types of fine fibrillar material. Some vessel elements in or near the secondary invasion pockets contained only the finer fibrils that reacted strongly with an antibody specific for pectin. Vessel elements rarely contained tyloses.Key words: cellulose, chitin, Dianthus caryophyllus, Fusarium wilt, gels and gums, host wall degradation, microhyphae, pectin, tyloses.

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49

Noshiro, Shuichi y Tomoyuki Fujii. "Fusiform Parenchyma Cells in the Young Wood of Pinaceae, and their Distinction from Marginal Parenchyma". IAWA Journal 15, n.º 4 (1994): 399–406. http://dx.doi.org/10.1163/22941932-90001374.

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Fusiform parenchyma cells found in several genera of Pinaceae are described and compared with marginal parenchyma. Fusiform parenchyma cells are mostly fusiform in shape, with occasional smooth horizontal walls. They form discontinuous tangential bands in complete or incomplete circ1es in the innermost growth rings of Larix, Abies, and Tsuga. Fusiform parenchyma always contains resinous material, and is more conspicuous in branchwoods than in stem woods. Marginal parenchyma cells were observed in Cedrus, Keteleeria, Pseudolarix, and Pseudotsuga as well as in Larix, Abies, and Tsuga, and very rarely in Picea. Marginal parenchyma cells are scattered along growth ring boundaries. They are always in strands with nodular horizontal walls with conspicuous simple pits. Cell wall structure of these two types of parenchyma differs in the intensity of the birefringence of the secondary walls. Fusiform parenchyma cells are distinct from marginal parenchyma with which they were previously confused, and should be regarded as a new component of coniferous wood.

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Rao, Karumanchi S., Yoon Soo Kim y Pramod Sivan. "Ultrastructural Changes in the Cell Walls of Cambial Derivatives During Wood Formation in Indian ELM (Holoptelea Integrifolia)". IAWA Journal 33, n.º 4 (2012): 403–16. http://dx.doi.org/10.1163/22941932-90000103.

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Sequential changes occurring in cell walls during expansion, secondary wall (SW) deposition and lignification have been studied in the differentiating xylem elements of Holoptelea integrifolia using transmission electron microscopy. The PATAg staining revealed that loosening of the cell wall starts at the cell corner middle lamella (CCML) and spreads to radial and tangential walls in the zone of cell expansion (EZ). Lignification started at the CCML region between vessels and associated parenchyma during the final stages of S2 layer formation. The S2 layer in the vessel appeared as two sublayers,an inner one and outer one.The contact ray cells showed SW deposition soon after axial paratracheal parenchyma had completed it, whereas noncontact ray cells underwent SW deposition and lignification following apotracheal parenchyma cells. The paratracheal and apotracheal parenchyma cells differed noticeably in terms of proportion of SW layers and lignin distribution pattern. Fibres were found to be the last xylem elements to complete SW deposition and lignification with differential polymerization of cell wall polysaccharides. It appears that the SW deposition started much earlier in the middle region of the fibres while their tips were still undergoing elongation. In homogeneous lignin distribution was noticed in the CCML region of fibres.

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