Immunocytochemical characterization of tension wood: Gelatinous fibers contain more than just cellulose.
TL;DR: Surprisingly, a number of antibodies that recognize arabinogalactan proteins and RG I-type pectin molecules bound to the G-layer, suggesting that AGPs and pectic mucilages are the source of the contractile forces that act on the cellulose microfibrils to provide the tension force necessary to bend the tree trunk.
Abstract: Gelatinous fibers (G-fibers) are the active component of tension wood. G-fibers are unlike traditional fiber cells in that they possess a thick, nonlignified gelatinous layer (G-layer) internal to the normal secondary cell wall layers. For the past several decades, the G-layer has generally been presumed to be composed nearly entirely of crystalline cellulose, although several reports have appeared that disagreed with this hypothesis. In this report, immunocytochemical techniques were used to investigate the polysaccharide composition of G-fibers in sweetgum (Liquidambar styraciflua; Hamamelidaceae) and hackberry (Celtis occidentalis; Ulmaceae) tension wood. Surprisingly, a number of antibodies that recognize arabinogalactan proteins and RG I-type pectin molecules bound to the G-layer. Because AGPs and pectic mucilages are found in other plant tissues where swelling reactions occur, we propose that these polymers may be the source of the contractile forces that act on the cellulose microfibrils to provide the tension force necessary to bend the tree trunk.
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TL;DR: This work investigates the structural and compositional basis of a sophisticated plant movement mechanism--the hydration-dependent unfolding of ice plant seed capsules--the reversible origami-like folding pattern proceeds via a cooperative flexing-and-packing mechanism actuated by a swellable cellulose layer filling specialized plant cells.
Abstract: Hydro-responsive plant movements have provided inspiration for the design of adaptive materials. Harrington et al. investigate the hydration-dependent unfolding of ice plant seed capsules and find an origami-like folding pattern, which could aid the development of biomimetic folding structures.
237 citations
TL;DR: This review presents a model of gelatinous-fibre organization and stresses the unique character of the gelatinous layer as a separate type of cell-wall layer, different from either primary or secondary wall layers.
Abstract: Gelatinous fibres are specialized fibres, distinguished by the presence of an inner, gelatinous cell-wall layer. In recent years, they have attracted increasing interest since their walls have a desirable chemical composition (low lignin, low pentosan, and high cellulose contents) for applications such as saccharification and biofuel production, and they have interesting mechanical properties, being capable of generating high tensional stress. However, the unique character of gelatinous layer has not yet been widely recognized. The first part of this review presents a model of gelatinous-fibre organization and stresses the unique character of the gelatinous layer as a separate type of cell-wall layer, different from either primary or secondary wall layers. The second part discusses major current models of tensional stress generation by these fibres and presents a novel unifying model based on recent advances in knowledge of gelatinous wall structure. Understanding this mechanism could potentially lead to novel biomimetic developments in material sciences.
197 citations
TL;DR: Measurements show that mesoporosity is high in tension wood with a typical thick G-layer while it is much less with a thinner G- layer, sometimes no more than normal wood.
Abstract: The mechanism for tree orientation in angiosperms is based on the production of high tensile stress on the upper side of the inclined axis. In many species, the stress level is strongly related to the presence of a peculiar layer, called G-layer, in the fibre wall. The structure of G-layer has been recently described as a hydrogel thanks to N2 adsorption-desorption isotherms of supercritically dried samples showing a high mesoporosity (pores size from 2 to 50 nm). This led us to revisit the concept of G-layer that was until now only described from anatomical observation. Adsorption isotherms of both normal wood and tension wood have been measured on six tropical species. Measurements show that mesoporosity is high in tension wood with typical thick G-layer while it is much less with thinner G-layer, sometimes no more than normal wood. The mesoporosity of tension wood species without G-layer is as low as in normal wood. Not depending on the amount of pores, the pore sizes distribution are always centred around 6-12 nm. These results suggest that, among species producing fibres with G-layer, large structural differences of G-layer exist between species
196 citations
TL;DR: It is proposed that, during cellulose crystallization, a part of the xyloglucan is trapped inside the crystal, inducing longitudinal tensile stress within it; another part of it is accessible and present between the G-layer and the outer wall layers.
132 citations
TL;DR: Various aspects of fiber development such as initiation, elongation, cell wall formation and multinuclearity are reviewed, discuss open questions and propose directions for further research.
Abstract: Plant fibers are one of the most important renewable resources, used as raw material in the paper industry, and for various textiles and for composites. Fibers are structural components in timber and an energy-rich component of fuel-wood. For the plant itself, fibers are important in establishing plant architecture, as a source of mechanical support, in defence from herbivory, and in some cases as elements with contractile properties, resembling those of muscles. In addition, fibers may store ergastic carbon resources and water. Here, we review various aspects of fiber development such as initiation, elongation, cell wall formation and multinuclearity, discuss open questions and propose directions for further research. Most of the recent progress in fiber formation biology, especially in cell wall structure and chemistry, emerged from studies of only a few model plants including flax, Populus spp., Eucalyptus spp., Arabidopsis thaliana and hemp. Considering the enormous importance of fibers to humanity, i...
126 citations
Cites background or methods from "Immunocytochemical characterization..."
..., 2008), some of which can originate from the presence of pectin-like substances in the gelatinous secondary cell wall (Bowling and Vaughn, 2008; Gorshkova et al., 2010)....
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..., 2002), sweetgum (Liquidambar styraciflua) and hackberry (Celtis occidentalis) (Bowling and Vaughn, 2008); primary phloem fibers of hemp (Blake et al....
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...The tension has also been proposed to be based on the gel-like properties of G-layers (Clair et al., 2008), some of which can originate from the presence of pectin-like substances in the gelatinous secondary cell wall (Bowling and Vaughn, 2008; Gorshkova et al., 2010)....
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...…species, including secondary xylem fibers of aspen (Bourquin et al., 2002), sweetgum (Liquidambar styraciflua) and hackberry (Celtis occidentalis) (Bowling and Vaughn, 2008); primary phloem fibers of hemp (Blake et al., 2008) and flax (Andemme-Onzighi et al., 2000; His et al., 2001; Snegireva et…...
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...…such as immunocytochemistry (e.g., His et al., 2001; Ageeva et al., 2005; Tomlinson and Fisher, 2005; Meloche et al., 2007; Blake et al., 2008; Bowling and Vaughn, 2008; Salnikov et al., 2008) or spectroscopy (Yoshinaga et al., 1997; Yoshida et al., 2005; Gierlinger et al., 2008; Schreiber et…...
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References
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TL;DR: The relationship between the polychromatic staining observed and the lignification of the walls is discussed and the effects of various common fixatives and the pH of the staining solution are evaluated.
Abstract: 1.
The polychromatic staining of plant cell walls by toluidine blue O is described and illustrated.
2.
The effects of various common fixatives and the effects of the pH of the staining solution are evaluated.
3.
Simple and rapid procedures are described for preparing stained temporary mounts of fresh material, or permanent mounts of embedded and sectioned material.
4.
The relationship between the polychromatic staining observed and the lignification of the walls is discussed.
2,041 citations
TL;DR: Major pathways for which the transcriptome and metabolome analysis suggested decreased activity were the pathway for C flux through guanosine 5'-diphosphate (GDP) sugars to mannans, the pentose phosphate pathway, lignin biosynthesis, and biosynthesis of cell wall matrix carbohydrates.
Abstract: Stems and branches of angiosperm trees form tension wood (TW) when exposed to a gravitational stimulus. One of the main characteristics of TW, which distinguishes it from normal wood, is the formation of fibers with a thick inner gelatinous cell wall layer mainly composed of crystalline cellulose. Hence TW is enriched in cellulose, and deficient in lignin and hemicelluloses. An expressed sequence tag library made from TW-forming tissues in Populus tremula (L.) x tremuloides (Michx.) and data from transcript profiling using microarray and metabolite analysis were obtained during TW formation in Populus tremula (L.) in two growing seasons. The data were examined with the aim of identifying the genes responsible for the change in carbon (C) flow into various cell wall components, and the mechanisms important for the formation of the gelatinous cell wall layer (G-layer). A specific effort was made to identify carbohydrate-active enzymes with a putative function in cell wall biosynthesis. An increased C flux to cellulose was suggested by a higher abundance of sucrose synthase transcripts. However, genes related to the cellulose biosynthetic machinery were not generally affected, although the expression of secondary wall-specific CesA genes was modified in both directions. Other pathways for which the data suggested increased activity included lipid and glucosamine biosynthesis and the pectin degradation machinery. In addition, transcripts encoding fasciclin-like arabinogalactan proteins were particularly increased and found to lack true Arabidopsis orthologs. Major pathways for which the transcriptome and metabolome analysis suggested decreased activity were the pathway for C flux through guanosine 5'-diphosphate (GDP) sugars to mannans, the pentose phosphate pathway, lignin biosynthesis, and biosynthesis of cell wall matrix carbohydrates. Several differentially expressed auxin- and ethylene-related genes and transcription factors were also identified.
389 citations
TL;DR: It might not be long before the entire differentiation pathway is understood and this advance would contribute substantially to the understanding of many important cellular events, including secondary cell wall synthesis, cell morphogenesis, vacuolar targeting and cell death.
301 citations
TL;DR: The functional characterization of R2R3-MYB gene function in Arabidopsis is reported based on the phenotype of three independent insertion alleles, suggesting that MYB61 may function in a genetic pathway distinct from that of TTG1.
Abstract: We have undertaken a systematic reverse genetic approach to understand R2R3-MYB gene function in Arabidopsis. Here, we report the functional characterization of MYB61 based on the phenotype of three independent insertion alleles. Wide-ranging phenotype screens indicated that MYB61 mutants were deficient in seed mucilage extrusion upon imbibition. This phenotype was expressed in the sporophytic tissues of the seed. Deposition and extrusion of the principal component of the mucilage, a relatively unbranched rhamnogalacturonan, were reduced in the MYB61 mutant seed coats. Additional defects in the maturation of the testa epidermal cells suggested a potential deficiency in extracellular secretion in myb61 lines. Consistent with a proposed role in testa development, reverse transcription‐polymerase chain reaction analysis showed the highest MYB61 expression in siliques, which was localized to the seed coat by a � -glucuronidase ( GUS ) reporter gene fusion. Lower levels of GUS expression were detected in developing vascular tissue. Parallel analysis of the ttg1-1 mutant phenotype indicated that this mutant showed more severe developmental defects than myb61 and suggested that MYB61 may function in a genetic pathway distinct from that of TTG1. The transient nature of seed epidermal characteristics in the ttg1-1 mutant suggested that TTG1 was required for maintenance rather than initiation of testa epidermal differentiation. Germination and seedling establishment were compromised in the myb61 and ttg1-1 mutants under conditions of reduced water potential, suggesting a function for Arabidopsis seed mucilage during germination in dry conditions.
284 citations