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Bamboo, a renewable resource with rapid growth and an impressive height-to-diameter ratio, faces mechanical instability due to its slender structure. Despite this, bamboo maintains its posture without breaking in its battle against environmental and gravitational forces. But what drives this motor function in bamboo? This study subjected Moso bamboo (Phyllostachys edulis) to gravitational stimulation, compelling it to grow at a 45° angle instead of upright. Remarkably, the artificially inclined bamboo exhibited astonishing shape control and adjustment capabilities. The growth strain was detected at both macroscopic and microscopic levels, providing evidence for the presence of internal stress, namely growth stress. The high longitudinal tensile stress on the upper side, along with a significant asymmetry in stress distribution in tilted bamboo, plays a pivotal role in maintaining its mechanical stability. Drawing upon experimental findings, it can be deduced that the growth stress primarily originates from the broad layers of fiber cells. Bamboo could potentially regulate the magnitude of growth stress by modifying the number of fiber cell layers during its maturation process. Additionally, the microfibril angle and lignin disposition may decisively influence the generation of growth stress., (© 2024 The Author(s). New Phytologist © 2024 New Phytologist Foundation.)

Summary: Xylem fibers are highly elongated cells that are key constituents of wood, play major physiological roles in plants, comprise an important terrestrial carbon reservoir, and thus have enormous ecological and economic importance. As they develop, from fusiform initials, their bodies remain the same length while their tips elongate and intrude into intercellular spaces.To elucidate mechanisms of tip elongation, we studied the cell wall along the length of isolated, elongating aspen xylem fibers and used computer simulations to predict the forces driving the intercellular space formation required for their growth.We found pectin matrix epitopes (JIM5, LM7) concentrated at the tips where cellulose microfibrils have transverse orientation, and xyloglucan epitopes (CCRC‐M89, CCRC‐M58) in fiber bodies where microfibrils are disordered. These features are accompanied by changes in cell wall thickness, indicating that while the cell wall elongates strictly at the tips, it is deposited all over fibers. Computer modeling revealed that the intercellular space formation needed for intrusive growth may only require targeted release of cell adhesion, which allows turgor pressure in neighboring fiber cells to 'round' the cells creating spaces.These characteristics show that xylem fibers' elongation involves a distinct mechanism that combines features of both diffuse and tip growth. [ABSTRACT FROM AUTHOR]

Carbon for cellulose biosynthesis is derived from sucrose. Cellulose is synthesized from uridine 5′-diphosphoglucose ( UDP-glucose), but the enzyme(s) responsible for the initial sucrose cleavage and the source of UDP-glucose for cellulose biosynthesis in developing wood have not been defined., We investigated the role of CYTOSOLIC INVERTASEs ( CINs) during wood formation in hybrid aspen ( Populus tremula × tremuloides) and characterized transgenic lines with reduced CIN activity during secondary cell wall biosynthesis., Suppression of CIN activity by 38-55% led to a 9-13% reduction in crystalline cellulose. The changes in cellulose were reflected in reduced diameter of acid-insoluble cellulose microfibrils and increased glucose release from wood upon enzymatic digestion of cellulose. Reduced CIN activity decreased the amount of the cellulose biosynthesis precursor UDP-glucose in developing wood, pointing to the likely cause of the cellulose phenotype., The findings suggest that CIN activity has an important role in the cellulose biosynthesis of trees, and indicate that cellulose biosynthesis in wood relies on a quantifiable UDP-glucose pool. The results also introduce a concept of altering cellulose microfibril properties by modifying substrate supply to cellulose biosynthesis. [ABSTRACT FROM AUTHOR]

The cell walls constitute the mechanical support of plants. Crystalline cellulose building the walls forms rigid microfibrils that set the stiffness of the cell and the direction in which it expands during growth. Therefore, the determination of the directions of the microfibrils is important in both mechanical and developmental assays., We adapted polarized light microscopy to estimate the cellulose microfibril orientations at subcellular resolution. The optical information supplements X-ray scattering data, Raman microspectroscopy, and electron microscopy., We analyzed samples from three plant tissues: cells from an Araucaria excels branch, in which we revealed lower cellulose density in regions where the cell wall curvature becomes bigger, namely, the cell wall corners; a wheat ( Triticum turgidum) awn's hygroscopically active region, which revealed a gradient in the cellulose microfibril angles that spans across four cell rows; and a stork's bill's ( Erodium gruinum) coiling awn, which revealed that the cellulose in the cell wall is organized in two orientations seamed together, rather than in a continuous helix., The unique spatial information is easily obtained from microscopic specimens and further illuminates new aspects in the mechanical tissues. [ABSTRACT FROM AUTHOR]

•It is generally hypothesized that the synthesis of cellulose in higher plants is mediated by cellulose synthase complexes (CSCs) localized on the plasma membrane. However, CSCs have not been investigated thoroughly through their isolation. The availability of ample Populus tissue allowed Populus CSCs to be isolated and characterized in association with xylem differentiation. •The methods used here included co-immunoprecipitation, proteomic analysis, laser microdissection, immunolocalization and others. •Western blot analysis of the immunoprecipitated CSCs led to the identification of at least two types of CSC in the membrane protein of Populus xylem tissue. Proteomic analysis further revealed that the two types of CSC were assembled from different cellulose synthase proteins. Immunolocalization confirmed that both types of CSC were involved in secondary cell wall formation. In addition, a number of noncellulose synthase proteins were also identified in association with CSC precipitation. •The results indicate that two types of CSC participate in secondary wall formation in Populus, suggesting a new mechanism of cellulose formation involved in the thickening of wood cell walls. This study also suggests that the CSC machinery may be aided by other proteins in addition to cellulose synthase proteins. [ABSTRACT FROM AUTHOR]

Contents The plant cell wall is central to plant development. Cellulose is a major component of plant cell walls, and is the world's most abundant biopolymer. Cellulose contains apparently simple linear chains of glucose residues, but these chains aggregate to form immensely strong microfibrils. It is the physical properties of these microfibrils that, when laid down in an organized manner, are responsible for both oriented cell elongation during plant growth and the strength required to maintain an upright growth habit. Despite the importance of cellulose, only recently have we started to unravel details of its synthesis. Mutational analysis has allowed us to identify some of the proteins involved in its synthesis at the plasma membrane, and to define a set of cellulose synthase enzymes essential for cellulose synthesis. These proteins are organized into a very large plasma membrane-localized protein complex. The way in which this protein complex is regulated and directed is central in depositing cellulose microfibrils in the wall in the correct orientation, which is essential for directional cell growth. Recent developments have given us clues as to how cellulose synthesis and deposition is regulated, an understanding of which is essential if we are to manipulate cell wall composition. [ABSTRACT FROM AUTHOR]

The morphogenesis of lobed plant cells has been considered to be controlled by microtubule (MT) and/or actin filament (AF) organization. In this article, a comprehensive mechanism is proposed, in which distinct roles are played by these cytoskeletal components. First, cortical MT bundles and, in the case of pavement cells, radial MT arrays combined with MT bundles determine the deposition of local cell wall thickenings, the cellulose microfibrils of which copy the orientation of underlying MTs. Cell growth is thus locally prevented and, consequently, lobes and constrictions are formed. Arch-like tangential expansion is locally imposed at the external periclinal wall of pavement cells by the radial arrangement of cellulose microfibrils at every wall thickening. Whenever further elongation of the original cell lobes occurs, AF patches assemble at the tips of growing lobes. Intercellular space formation is promoted or prevented by the opposite or alternate, respectively, arrangement of cortical MT arrays between neighboring cells. The genes that are possibly involved in the molecular regulation of the above morphogenetic procedure by MT and AF array organization are reviewed. New Phytologist (2005) doi: 10.1111/j.1469-8137.2005.01464.x © New Phytologist (2005) [ABSTRACT FROM AUTHOR]

Wood is a complex and highly variable tissue, the formation of which is developmentally and environmentally regulated. In reaction to gravitropic stimuli, angiosperm trees differentiate tension wood, a wood with specific anatomical, chemical and mechanical features. In poplar the most significant of these features is an additional layer that forms in the secondary wall of tension wood fibres. This layer is mainly constituted of cellulose microfibrils oriented nearly parallel to the fibre axis. Tension wood formation can be induced easily and strongly by bending the stem of a tree. Located at the upper side of the bent stem, tension wood can be compared with the wood located on its lower side. Therefore tension wood represents an excellent model for studying the formation of xylem cell walls. This review summarizes results recently obtained in the field of genomics on tension wood. In addition, we present an example of how the application of functional genomics to tension wood can help decipher the molecular mechanisms responsible for cell wall characteristics such as the orientation of cellulose microfibrils. New Phytologist (2004) doi: 10.1111/j.1469-8137.2004.01176.x © New Phytologist (2004) [ABSTRACT FROM AUTHOR]

Microtubules (MTs) and actin filaments (AFs) form highly organized arrays in stomatal cells that play key roles in the morphogenesis of stomatal complexes. The cortical MTs controlling the orientation of the depositing cellulose microfibrils (CMs) and affecting the pattern of local wall thickenings define the mechanical properties of the walls of stomatal cells, thus regulating accurately their shape. Besides, they are involved in determination of the cell division plane. Substomatal cavity and stomatal pore formation are also MT-dependent processes. Among the cortical MT arrays, the radial ones lining the periclinal walls are of particular morphogenetic importance. Putative MT organizing centers (MTOCs) function at their focal regions, at least in guard cells (GCs), or alternatively, these regions either organize or nucleate cortical MTs. AFs are involved in cell polarization preceding asymmetrical divisions, in determination of the cell division plane and final cell plate alignment and probably in transduction of stimuli implicated in stomatal complex morphogenesis. Mature kidney-shaped GCs display radial AF arrays, undergoing definite organization cycles during stomatal movement. They are involved in stomatal movement, probably by controlling plasmalemma ion-channel activities. Radial MT arrays also persist in mature GCs, but a role in stomatal function cannot yet be attributed to them. © New Phytologist (2004) doi: 10.1111/j.1469-8137.2004.00986.x [ABSTRACT FROM AUTHOR]

During the initial phases of elongation of pea internodes, oat and rice coleoptiles, oat mesocotyls, soybean hypocotyls and dandelion peduncles, net transverse orientation of cellulose wall microfibrils (Mfs) was found in the outer epidermal wall. This paper demonstrates that in all these axes, with the exception of rice coleoptile, net longitudinal orientation of microfibrils occurs in the outer epidermal wall in portions of the axes that were still elongating at the time of sampling. The timing of the transition to net longitudinal orientation and whether the transition proceeded acropetally or basipetally varied with the type of axis under study. The variability of the relationship between extension and the transition from net transverse to net longitudinal orientation suggests that factors other than extension are important in determining the transition. Layers of longitudinal wall microfibrils may be added to the extending epidermal wall to bolster its tensile strength commensurate with its function during and after extension. Attention is drawn to the parallels between the concept of tissue tension in growing axes and the concept that the epidermis functions as a stressed skin in the support of mature plant parts in primary growth. [ABSTRACT FROM AUTHOR]

Immunoelectron microscopy using the anti-pectin monoclonal antibody JIM 7 confirmed earlier observations that pectin degradation is a primary event in the process of host cell wall breakdown during the development of chocolate spot disease (causal agent: Botrytis fabae (Sard.)) of broad bean. Close examination of infected and non-infected Vicia faba L.. leaves indicated a loss of JIM 7-labeling, and therefore, methyl-esterified pectin, from swollen walls of infected and contiguous epidermal cells. Modified mesophyll walls also possessed less methyl-esterified pectin than healthy walls. Enzymes which attack methyl-esterified pectin appeared to he most active in regions of host tissue close to sites of fungal infection. Ultrastructural studies using the enzyme, cellobiohydrolase conjugated to gold (CBH1-Au) revealed that the cellulose microfibrils of outer epidermal walls of non-infected V. faba leaf tissue were heavily masked by other components of the plant cell wall. Such material was most probably pectin because the cellulose microfibrils of swollen epidermal and modified mesophyll walls of infected host tissue were heavily labelled with CBH1-Au. These results were confirmed by double-labeling studies using JIM 7 and CBH1-Au. At early stages of the infection process, limited cellulose degradation was observed in infected leaf tissue. Double-labelling experiments using the monoclonal antibody BC-KH4 directed against Botrytis matrices and a marker for the plant cell wall (JIM 7 or CBH1-Au) confirmed previous observations that the fungal matrices extended through modified host walls and degenerate cytoplasm. It is suggested that the wall-modifying action of the pectin-degrading enzymes produced during the infection process might facilitate pervasion of matrix material associated with the infection process might facilitate pervasion of matrix material associated with the infection hyphae through host cell walls. ossible role(s) of such matrix material during the post-penetration rocesses of the V. faba-B. fabae relationship are discussed. [ABSTRACT FROM AUTHOR]

The thallus of the metzgerialean liverwort Symphygyna brasiliensis Necs contains a strand of dead thick-walled cells with helicoidally-arranged pits that are presumably involved in water transport. During the first phase of differentiation these cells undergo a 13- 16-fold elongation while remaining thin-walled and almost unchanged in diameter. During subsequent maturation the walls become strongly thickened by deposition of highly electron- opaque material on extraplasmodesmal areas and of transparent material forming collars around plasmodesmal. Whilst the growing wall shows an ordered micofibrillar texture and is strongly reactive to PATAg staining for carbohydrates, the material associated with plasmodesmata is amorphous and PATAg-negative. A dense conical array of microtobules (MTs) overlies the growing wall except in proximity to plasmodesmata, which are closely associated with tubular endoplasmic reticulum (ER). During cellular maturation plasmodesmata undergo extensive secondary elongation by incorporation of conical ER supposedly continuous with desmotubules. Quantitative analysis of plasmodesmal frequencies in relation to cellular elongation and wall thickness indicates that there is no de novo formation of plasmodesmata. Cortical MTs, wall microfibrils and secondarily-modified plasmodesmata are consistently co-aligned, all forming helices of about 45°. During maturation the Golgi apparatus proliferates and a vast number of vesicles containing PATAg-positive material are produced from a membrane domain interpreted as trans Golgi network, whilst PATAg-negative vesicles are formed along the fenestrated margins of cis and medial dictyosomal cisternae. Exocytosis of PATAg-positive vesicles is confined to extraplasmodesmal areas. In ageing cells abundant fibrillar material, also positive to PATAg-test. accumulates within pleomorphic membrane-bounded tubules. [ABSTRACT FROM AUTHOR]

Morphogenesis of sinuous epidermal cells in leaves of the fern Asplenium nidus and the monocotyledonous Cyperus papyrus, petals of the dicotyledonous Begonia lucerna, and in-vitro-grown leaves of the fern Adiantum capillusveneris is controlled by the local differentiation of their walls. In all these cases wall pads, including radial cellulose microfibrils, are deposited at the junctions of the external periclinical wall with the anticlinal ones. Moreover, in Asplenium nidus, similar wall pads form at the junctions of the external periclinal wall with the anticlinal ones. The wall pads are connected to anticlinal cellulose microfibril bundles running the whole depth of the anticlincal walls or part of it. This wall differentiation imposes a highly controlled cell wall expansion, a consequence of which is the waviness of the epidermal cell anticlinal walls. The pattern of wall reinforcement varies among different species, resulting in differences in the pattern of waviness. Cortical microtubule arrays mirror the orientated deposition of cellulose mircofibrils in the epidermal cells. These findings, derived from plants from different major groups, show a common epidermal cell morphogenetic mechanism depending or radial cellulose microfibrils and cellulose microfibril bundles. The facts that (a) epidermal cell morphogenesis in Adiantum capillus-veneris leaves grown in vitro differs considerably from that of typical leaves and (b) petal epidermal cells in Begonia lucerna are sinuous, while leaf epidermal cells are not, suggest that this mechanism may be affected by epigenetic factors. [ABSTRACT FROM AUTHOR]

With the exception of the unicellular yeasts, fungi typically grow by means of hyphae that extend only at their apices and ramify into a mycelium. This mode of growth provides fungi with a certain mobility and the ability to invade dead and living organic substrata. They are thus the main decomposers of plant residues but they also have established intricate symbiotic relationships with plants, both mutualistic and parasitic. The process of apical growth of a hypha requires the controlled expansion of the apical wall which must be transformed subsequently into a wall that resists turgor pressure and maintains the tubular shape of the hypha. Although the driving force for hyphal extension is probably the turgor pressure, a subtle interplay between wall extension and cytoplasmic activity is necessary because only a precise gradient of wall-synthetic activity can maintain uniform wall thickness during expansion. Possibly, the presence in the plasma membrane of mechanico-sensitive proteins plays a role in conjunction with the cytoskeleton at the apex, particularly actin. Although the major structural wall polysaccharides are probably manufactured directly on the expanding apical plasma membrane, proteins (and probably some wall components) are delivered to the growing surface by a continuous stream of exocytotic vesicles that fuse with the plasma membrane, at the same time extending its surface. Our analyses of the chemistry of the fungal wall and its biosynthesis and assemblage have disclosed a simple mechanism (though complex in detail) that may explain the transition from a newly formed expandable wall at the apex to a more rigid wall at the base of the hyphal extension zone. Two individual wall polymers, chitin and β-glucan, extruded at the apex are modified within the domain of the wall. Among the modifications observed arc the formation of covalent crosslinks between these two polymers and hydrogen bonds between the homologous polymer chains, leading to the formation of chitin microfibrils crosslinked to a glucan matrix. This process is thought to convert an initially plastic wall into a rigid wall as the polymers fall behind the advancing tip. We have called this the steady-state growth theory for apical wall extension because a steady-state amount of plastic wall is always maintained at the growing apex. Excretion of lytic enzymes is a vital process in filamentous fungi because, in nature, they thrive on organic polymers which must be degraded extracellularly. Such enzymes are also necessary for infection processes. Cytological data suggest that such enzymes are extruded by the vesicles that continuously fuse with the plasma membrane at the growing apex. We have shown that a large portion of the excreted enzymes indeed leaves the hypha at the growing apex but another portion may be retained by the wall and is slowly released into the medium. In relation to the steady-state growth theory we hypothesize that enzymes can pass the wall at the apex by bulk flow, that is, by being carried by the flow of plastic wail material, making pores in the wall less important than previously thought. Proteins excreted by filamentous fungi not only serve dissimilatory purposes but are also important for a variety of other activities of the whole mycelium, including morphogenesis. By cloning genes abundantly expressed during formation of aerial hyphae and fruit bodies, we have discovered a class of proteins, named hydrophobins, which are only produced when the mycelium has reached a certain stage of maturity. Whilst excreted by submerged hyphae as monomers into the medium, they self-assemble as insoluble complexes in the walls of emergent hyphae. In aerial hyphae a particular hydrophobin takes the form of rodlets which probably coat the hyphae with an impermeable layer. During fruit-body formation other hydrophobins are produced which may function in the aggregation of hyphae to form a multicellular tissue. Apart from such specific morphogenetic functions, the hydrophobins may play a general role in insulating hyphae from the environment, converting the differentiating structures into sinks for translocation of water and nutrients from the assimilating mycelium. [ABSTRACT FROM AUTHOR]

In primary leaves of Vigna sinensis Endl. seedlings growing in the presence of colchicine, some giant polyploid cells at the phloem pole of the vascular bundles differentiate into an extraordinary cell type acquiring most of the prominent features of the sieve elements. These aberrant sieve elements (a-SEs) show some exceptional features not found in normal sieve-tube elements. A heavy secondary thickening is deposited on their walls, which in surface view exhibits a reticulate or `pitted' appearance. The thickenings reach the same depth into the cytoplasm and show a diffuse orientation of cellulose microfibrils. Amorphous callose is deposited around some fine cytoplasmic strands penetrating the secondary wall up to the primary one along the longitudinal and particularly the transverse walls. In the latter walls sieve pores are not formed. At first, the a-SEs undergo a partial protoplasmic degradation like normal sieve-tube elements but finally autolyse completely. During this process, the major portion of the unmasked primary and secondary wall is dissolved. The observations show that (a) a vascular bundle initiation and development proceeds in the affected primary leaves, in the absence of cell divisions. 'Vascular bundles' are formed consisting of a single row of cells, in which a-SE differentiation dominates. (b) The 'sieve element differentiation' is initiated without differential divisions. (c) Although the microtubules are absent, the cells determined to become a-SEs activate another morphogenetic mechanism to control a more or less patterned deposition of a secondary wall layer. [ABSTRACT FROM AUTHOR]

Helicoidal cell walls are characterized by an oscillatory shift in the arrangement of cellulose microfibrils somewhat reminiscent of the rotating movement of the hands of a clock. The periodic movement can be sustained or perturbed. Thus, the helicoidal cell wall presents a temporal reading. Sensitive to temporal signals, the cell wall keeps a record of cellular events and registers very small variations, storing data at a subcellular level. The present paper emphasizes some aspects of the helicoidal cell wall relevant to timekeeping, revealing its dynamics and flexibility and leading to the question of the mechanisms of its construction. [ABSTRACT FROM AUTHOR]

Apical hyphal walls in rapidly growing 48-hour cultures of Phytophthora are significantly thinner than mature non-apical walls from 7-day cultures. Enzymic treatments have shown that in young apices the outer layer of wall glucan is attenuated as compared with mature regions and it is suggested that there is less protein associated with the cellulose microfibrils in the inner part of the wall. [ABSTRACT FROM AUTHOR]

Helicoidally arranged layers of cellulose microfibrils in plant cell walls can produce strong and vivid coloration in a wide range of species. Despite its significance, the morphogenesis of cell walls, whether reflective or not, is not fully understood. Here we show that by optically monitoring the reflectance of Pollia japonica fruits during development we can directly map structural changes of the cell wall on a scale of tens of nanometres. Visible-light reflectance spectra from individual living cells were measured throughout the fruit maturation process and compared with numerical models. Our analysis reveals that periodic spacing of the helicoidal architecture remains unchanged throughout fruit development, suggesting that interactions in the cell-wall polysaccharides lead to a fixed twisting angle of cellulose helicoids in the cell wall. By contrast with conventional electron microscopy, which requires analysis of different fixed specimens at different stages of development, the noninvasive optical technique we present allowed us to directly monitor live structural changes in biological photonic systems as they develop. This method therefore is applicable to investigations of photonic tissues in other organisms., (© 2021 The Authors New Phytologist © 2021 New Phytologist Trust.)

Certain xylanases from family GH10 are highly expressed during secondary wall deposition, but their function is unknown. We carried out functional analyses of the secondary-wall specific PtxtXyn10A in hybrid aspen (Populus tremula × tremuloides). PtxtXyn10A function was analysed by expression studies, overexpression in Arabidopsis protoplasts and by downregulation in aspen. PtxtXyn10A overexpression in Arabidopsis protoplasts resulted in increased xylan endotransglycosylation rather than hydrolysis. In aspen, the enzyme was found to be proteolytically processed to a 68 kDa peptide and residing in cell walls. Its downregulation resulted in a corresponding decrease in xylan endotransglycosylase activity and no change in xylanase activity. This did not alter xylan molecular weight or its branching pattern but affected the cellulose-microfibril angle in wood fibres, increased primary growth (stem elongation, leaf formation and enlargement) and reduced the tendency to form tension wood. Transcriptomes of transgenic plants showed downregulation of tension wood related genes and changes in stress-responsive genes. The data indicate that PtxtXyn10A acts as a xylan endotransglycosylase and its main function is to release tensional stresses arising during secondary wall deposition. Furthermore, they suggest that regulation of stresses in secondary walls plays a vital role in plant development., (© 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.)