Coordinated crosstalk between microtubules and actin by a spectraplakin regulates lumen formation and branching

Subcellular lumen formation by single-cells involves complex cytoskeletal remodelling. We have previously shown that centrosomes are key players in the initiation of subcellular lumen formation in Drosophila melanogaster, but not much is known on the what leads to the growth of these subcellular luminal branches or makes them progress through a particular trajectory within the cytoplasm. Here, we have identified that the spectraplakin Short-stop (Shot) promotes the crosstalk between MTs and actin, which leads to the extension and guidance of the subcellular lumen within the tracheal terminal cell (TC) cytoplasm. Shot is enriched in cells undergoing the initial steps of subcellular branching as a direct response to FGF signalling. An excess of Shot induces ectopic acentrosomal luminal branching points in the embryonic and larval tracheal TC leading to cells with extra-subcellular lumina. These data provide the first evidence for a role for spectraplakins in single-cell lumen formation and branching.

The Microstructure and Mechanical Properties of Poplar Catkin Fibers Evaluated by Atomic Force Microscope (AFM) and Nanoindentation

In this study, the microstructure and mechanical properties of poplar (Populus tomentosa) catkin fibers (PCFs) were investigated using field emission scanning electron microscope, atomic force microscopy (AFM), X-ray diffraction, and nanoindentation methods. Experimental results indicated that PCFs had a thin-wall cell structure with a large cell lumen and the hollow part of the cell wall took up 80 percent of the whole cell wall. The average diameters of the fiber and cell lumen, and the cell wall thickness were 5.2, 4.2, and 0.5 µm, respectively. The crystallinity of fibers was 32%. The AFM images showed that the orientation of microfibrils in cell walls was irregular and their average diameters were almost between 20.6–20.8 nm after being treated with 2 and 5 wt.% potassium hydroxide (KOH), respectively. According to the test of nanoindentation, the average longitudinal-reduced elastic modulus of the PCF S2 layer was 5.28 GPa and the hardness was 0.25 GPa.

Gymnomitrion fissum (Gymnomitriaceae, Marchantiophyta) — a new species with fissured leaf surface from China

Study of selected specimens of Gymnomitrion collected by D. G. Long in Yunnan, China, revealed a new species, G. fissum Mamontov et Potemkin, sp. nov., with a fissured leaf surface. Comparison of SEM images of the leaf surface and leaf cross sections shows that the leaf surface of G. fissum is different from that of other known species with a superficially similar leaf surface, i. e. Mylia taylorii, M. verrucosa s. l. and Trabacellula tumidula. It has fissures around the cell lumen rather than grids and perforations. Outer cell walls of Gymnomitrion fissum are much thicker than in Mylia taylorii, M. verrucosa s. l. and Trabacellula tumidula, and their outer layers tend to be partly or completely caducous. G. fissum is related to the group of species assigned to the former genus Apomarsupella.

Cell walls as taxonomic markers in Polish species of the genus Odontoschisma (Dum.) Dum. (Hepaticae, Cephaloziaceae)

To get valuable diagnostic characters, the structure of cell walls was studied with use of two stains (Ruthenium Red -RR and Resorcine Blue - RB) and in polarized light. As far as the stem structure is concerned, European species of the genus <em>Odontoschisma</em> fall into two groups: in <em>Odontoschisma elongatum</em> and in <em>Odontoschisma macounii</em> a thick, frequently completely obscuring cell lumen, "lining layer" is present. It frequently, particularly after staining in RB, detaches from the rest of the cell wall. Such a layer is completely lacking in the two remaining species, viz. <em>O. sphagni</em> and <em>0. denudatum</em>. In polarized light only leaves of <em>O. sphagni</em> show a distinct bright border. The thin cellulose layer (bright in polarized light) embrace the angular thickenings in <em>0. sphagni</em> and <em>0. denudatum</em>, but is entering the inside of these thickenings in the two remaining species. Keys for determination of the four European species based on the staining properties of cell walls and their look in polarized light are provided.

Durability of Wood-Polymer Composite Prepared by In Situ Polymerization of Functional Monomers

Fast-growing plant wood, Micheliamacclurel wood, was modified by formation of wood-polymer composite to improve its decay resistance. Two functional monomers, glycidyl methacrylate and ethylene glycol dimethacrylate, added with a few Azo-bis-isobutryonitrile as initiator, and maleic anhydride as catalyst, were first impregnated into wood cell lumen under a vacuum-pressure condition, and then in-situ polymerized into copolymers through a catalyst-thermal treatment. The decay resistances of untreated wood and wood-polymer composites were assessed by weight loss and compared by SEM observations. SEM and FTIR analysis indicated that the in-situ polymerized copolymers fully filled up wood cell lumen and also grafted onto wood cell walls, resulting in the blockage of passages for microorganisms and moisture to wood cell walls. Thus, the decay resistance of the wood-polymer composite against brown rot fungus and white rot fungus in terms of weight loss achieved 1.04%~1.33%, improved 95.10%~95.35% than those of untreated Micheliamacclurel wood; and also higher than that of boron-treated wood. The SEM observations presented the remarkable improvement of decay resistance of wood after such treatment, which effectively protected wood from degradation by fungi.

cDNAs Generated from Individual Epidermal Cells Reveal that Differential Gene Expression Predicting Subsequent Resistance or Susceptibility to Rust Fungal Infection Occurs Prior to the Fungus Entering the Cell Lumen

As the cowpea rust fungus penetrates the wall of a cowpea epidermal cell, resistant and susceptible plants exhibit different ultrastructural and cytochemical changes within the epidermal protoplast. To examine plant gene expression at this stage of infection, cytoplasm was extracted from individual inoculated or uninoculated epidermal cells before the fungal penetration peg reached the cell lumen. Initial differential colony hybridization screening of an expressed sequence tag library constructed from globally amplified cDNAs generated from the inoculated resistant cells resulted in 80 clones (out of 835) with a differential hybridization pattern. Further slot-blot screening and screening of the amplified cDNAs generated from inoculated or uninoculated, resistant or susceptible cells revealed 28 separate genes, mostly with no matching sequences in the databases, that were up-regulated in response to the growth of the fungus through the wall of resistant or susceptible cells. Five genes, including those coding for β- and α-tubulin, were found to be down-regulated specifically in inoculated, susceptible cells, and five were specifically up-regulated in inoculated, resistant cells, including a PR-10 homolog and a phenylalanine ammonialyase gene. Probing the amplified cDNAs from each cell type for the expression of cell death-related genes revealed that an LLS1 homolog (vuLLS1), cloned from cowpea, was up-regulated by infection in both resistant and susceptible cells and that a homolog of HSR203J was differentially up-regulated in resistant cells. These data show that changes in gene expression predicting the subsequent expression of susceptibility or hypersensitive resistance to fungal infection occur prior to the fungus entering the cell lumen.

Compartmented cells in the mesophyll of Araucaria angustifolia (Araucariaceae)

The compartmented cells of the immature and mature leaves of young and adult plants of Araucaria angustifolia (Bert.) O. Ktze. are characterised by the presence of pectinous partitions in the cell lumen, forming a system of compartments. The function of these cells is possibly related to water storage and translocation. The morphology of compartmented cells differs from that of immature and mature leaves: at the time of maturity the compartment system or secretion is more defined. These cells undergo the programmed cell death (PCD) process, because they are enucleated in adult plants. The compartmented cells' cytology and pectic composition are similar to the mucilage cells of Lauraceae and Cactaceae.