| 973431. |
- Majda, Mateusz, et al.
(författare)
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Elongation of wood fibers combines features of diffuse and tip growth
- 2021
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Ingår i: New Phytologist. - : John Wiley & Sons. - 0028-646X .- 1469-8137. ; 232:2, s. 673-691
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 973432. |
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| 973433. |
- Majda, Mateusz, et al.
(författare)
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Mechanochemical Polarization of Contiguous Cell Walls Shapes Plant Pavement Cells
- 2017
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Ingår i: Developmental Cell. - : Elsevier BV. - 1534-5807 .- 1878-1551. ; 43:3, s. 4-304
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Tidskriftsartikel (refereegranskat)abstract
- The epidermis of aerial plant organs is thought to be limiting for growth, because it acts as a continuous load-bearing layer, resisting tension. Leaf epidermis contains jigsaw puzzle piece-shaped pavement cells whose shape has been proposed to be a result of subcellular variations in expansion rate that induce local buckling events. Paradoxically, such local compressive buckling should not occur given the tensile stresses across the epidermis. Using computational modeling, we show that the simplest scenario to explain pavement cell shapes within an epidermis under tension must involve mechanical wall heterogeneities across and along the anticlinal pavement cell walls between adjacent cells. Combining genetics, atomic force microscopy, and immunolabeling, we demonstrate that contiguous cell walls indeed exhibit hybrid mechanochemical properties. Such biochemical wall heterogeneities precede wall bending. Altogether, this provides a possible mechanism for the generation of complex plant cell shapes. Pavement cells in the leaf epidermis are multi-lobed like jigsaw puzzle pieces. Majda et al. provide evidence through in vivo analyses using atomic force microscopy and computational modeling that mechanical heterogeneities across and along anticlinal cell walls allow wall bending that contributes to lobe formation and these complex cell shapes.
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| 973434. |
- Majda, Mateusz, et al.
(författare)
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The Role of Auxin in Cell Wall Expansion
- 2018
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 19
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Forskningsöversikt (refereegranskat)abstract
- Plant cells are surrounded by cell walls, which are dynamic structures displaying a strictly regulated balance between rigidity and flexibility. Walls are fairly rigid to provide support and protection, but also extensible, to allow cell growth, which is triggered by a high intracellular turgor pressure. Wall properties regulate the differential growth of the cell, resulting in a diversity of cell sizes and shapes. The plant hormone auxin is well known to stimulate cell elongation via increasing wall extensibility. Auxin participates in the regulation of cell wall properties by inducing wall loosening. Here, we review what is known on cell wall property regulation by auxin. We focus particularly on the auxin role during cell expansion linked directly to cell wall modifications. We also analyze downstream targets of transcriptional auxin signaling, which are related to the cell wall and could be linked to acid growth and the action of wall-loosening proteins. All together, this update elucidates the connection between hormonal signaling and cell wall synthesis and deposition.
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| 973435. |
- Majda, Mateusz
(författare)
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Visualization of Plant Cell Wall Epitopes Using Immunogold Labeling for Electron Microscopy
- 2019
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Ingår i: Bio-protocol. - 2331-8325. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Plant cell walls consist of different polysaccharides and structural proteins, which form a rigid layer located outside of the plasma membrane. The wall is also a very dynamic cell composite, which is characterized by complex polysaccharide interactions and various modifications during cell development. The visualization of cell wall components in situ is very challenging due to the small size of cell wall composites (nanometer scale), large diversity of the wall polysaccharides and their complex interactions. This protocol describes immunogold labeling of different cell wall epitopes for high-resolution transmission electron microscopy (TEM). It provides a detailed procedure for collection and preparation of plant material, ultra-thin sectioning, specimen labeling and contrasting. An immunolabeling procedure workflow was optimized to obtain high efficiency of carbohydrates labeling for high-resolution TEM. This method was applied to study plant cell wall characteristics in various plant tissues but could also be applied for other cell components in plant and animal tissues.
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| 973436. |
- Majdalawieh, Osama F, et al.
(författare)
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Linearity and Lever Ratio of the Normal and Reconstructed Cadaveric Human Middle Ear
- 2008
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Ingår i: Otology & Neurotology. - 1531-7129. ; 29:6, s. 796-802
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: The linearity and the level ratio are different in reconstructed ears. Background: The linearity of the reconstructed human middle ear (ME) has not been previously explored. It is important to analyze if high sound pressure levels (SPLs) result in distortion due to nonlinearities particularly because hearing aids have high-output SPLs. The diseased ME is reconstructed with prostheses. These diseased ears frequently need additional amplification with hearing aids, and it is unclear if reconstruction itself leads to nonlinear ME responses. Methods: Eight fresh human cadaveric temporal bones were used. Pure tones of 70, 90, and 110 dB SPL at 500, 1,000, and 3,000 Hz were presented to the ear canal. Umbo and stapes displacements were measured by means of a laser Doppler vibrometer. After removing the incus, the tympanic membrane assembly to the stapes head prosthesis was placed, and measurements were repeated. Results: Stapes footplate vibrations in the reconstructed ears are 10 to 15 dB lower than those of the normal ears. In both normal and reconstructed ears, the footplate vibrations are linearly related to SPL at the tympanic membrane between 70 and 110 dB SPL at the frequencies tested. For the lever ratio, intact ears are more efficient at transmission of umbo vibrations to the stapes compared with reconstructed ears. Conclusion: To within acceptable limits, the ME seems to be linear between 70 and 110 dB SPL input levels, across the speech frequencies, and this does not change with reconstruction. The reconstructed human ME seems to have a less efficient lever ratio than the intact ME.
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| 973437. |
- Majdejabbari, Sara, et al.
(författare)
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Synthesis and Characterization of Biosuperabsorbent Based on Ovalbumin Protein
- 2010
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Ingår i: Journal of macromolecular science. Pure and applied chemistry (Print). - : Informa UK Limited. - 1060-1325 .- 1520-5738. ; 47:7, s. 708-715
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A biosuperabsorbent (Bio-SAP) hydrogel from ovalbumin (egg protein) was synthesized via modification with an acylating reagent and a bifunctional crosslinker, and its swelling behavior was investigated. The protein was acylated using ethylenediaminetetraacetic dianhydride (EDTAD), and then crosslinked by glutaraldehyde and dried. Bio-SAP provided through this method includes modification of lysyl residues in the unfolded protein by adding one or more hydrophilic carboxyl groups to increase the hydrophilicity of protein. The water binding capacity was measured in deionized water, 0.9% NaCl solution and synthetic urine, which under the best conditions were 296, 64 and 56 g/g after 24 h, respectively. In addition, the effects of EDTAD/protein ratio on the chemical modification of the protein, the various chemical neutralization agents, pH sensitivity and ionic strength, as well as temperature and particle size on the water absorption capacity with and without load and its kinetic were also investigated.
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| 973438. |
- Majdejabbari, Sara, et al.
(författare)
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Synthesis and Properties of a Novel Biosuperabsorbent from Alkali Soluble Rhizomucor pusillus Proteins
- 2011
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Ingår i: Applied Microbiology and Biotechnology. - : Springer. - 0175-7598 .- 1432-0614. ; 92:6, s. 1171-1177
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Tidskriftsartikel (refereegranskat)abstract
- A novel biosuperabsorbent protein hydrogel was prepared from protein-rich alcoholic–alkali soluble parts of zygomycete Rhizomucor pusillus biomass. The fungal protein content was 46.8%, and the lipid content was 13.1%. Extraction of protein from this microorganism through the method applied prevents protein decomposition, resulting in maximum yield. After alcoholic–alkaline extraction, the proteins from the biomass were acylated using ethylenediaminetetraacetic dianhydride and subsequently treated with glutaraldehyde as a crosslinker for further experiments. Thermal consistency was investigated by means of two different methods: thermal denaturation via differential scanning calorimetry and thermal decomposition study via thermogravimetric analysis. The swelling behaviour of the crosslinked hydrogel was measured in deionised water, 0.9% NaCl solution and synthetic urine, which were 87.6, 43 and 38.6 g/g water after 24 h, respectively. Moreover, the isoelectric point (pI) of the hydrogel was determined as pH = 8 by studying swelling behaviour at different pHs. In addition, the dependencies of the swelling behaviour with regard to the chemical modification, the ionic strength, the degree of crosslinking, as well as water absorbency with or without load were studied.
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| 973439. |
- Majdi, Hooshang, et al.
(författare)
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Effects of fertilization with dolomite Lime plus PK or wood ash on root distribution and morphology in a Norway spruce stand in Southwest Sweden
- 2005
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Ingår i: Forest Science. - 0015-749X .- 1938-3738. ; 50:6, s. 802-809
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Tidskriftsartikel (refereegranskat)abstract
- Pelleted wood ash (A) or crushed dolomite lime with added potassium and phosphorous (CaMgPK) was applied to plots in a 60-yr-old Norway spruce stand in Southwest Sweden. Eight years later, we measured the effect of these treatments on a number of root parameters, including root biomass and distribution (in different diameter classes), root length density (cm cm(-3) Soil), specific root length (SRL, mg(-1) DM), and number of mycorrhizal root tips. Layers sampled included the humus layer and the upper 30 cm of the mineral soil. The total fine root (0-1 mm) biomass in the mineral soil layer was lower in the A plots than the control plots, and the fine root (1-2 mm) systems were shallower in the A plots compared to both the control and CaMgPK plots. SRL was higher in the humus layer in both the CaMgPK and A plots than in the controls, and higher in the CaMgPK than in the A plots. The number of mycorrhizal root tips was also higher in the treated plots than in the controls, with the highest numbers being found in CaMgPK plots. Based on our results, we conclude that both the CaMgPK and ash treatments resulted in changes in root morphology and, therefore, presumably increased the capacity for nutrient uptake.
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| 973440. |
- Majdi, Hooshang, et al.
(författare)
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Effects of slash retention and wood ash addition on fine root biomass and production and fungal mycelium in a Norway spruce stand in SW Sweden
- 2008
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 1872-7042 .- 0378-1127. ; 255:7, s. 2109-2117
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Tidskriftsartikel (refereegranskat)abstract
- In the study reported here we examined the short-term effects (1-3 years) of slash retention (SR) and the long-term effects (13-15 years) of wood-ash application (A) on fine roots and mycorrhizae in a 40-year-old Norway spruce forest in southwest Sweden. Soil cores were used to obtain estimates of the biomass (g m(-2)) of roots in three diameter classes (< 0.5, 0.5-1 and 1-2 mm), root length density (RLD), specific root length (SRL) and mycorrhizal root tip density (RTD). Fine root (< 1 mm) length production and mortality, and mycelium production, were estimated using minirhizotron and mesh bag techniques, respectively. Compared with the control plots (C), the biomass of fine roots in diameter classes < 0.5 mm and 0.5-1 mm was significantly higher in A plots, but lower in SR plots. In addition, RLD was significantly lower in the humus layer of SR plots than in the humus layers of C and A plots, but not in the other layers. None of the treatments affected the SRL. In all soil layers, the SR treatment resulted in significant reductions in the number of ectomycorrhizal root tips, and the mycelia production of fungi in mesh bags, relative to the C treatment, but the C and A treatments induced no significant changes in these variables. Fine root length production in the C, A and SR plots amounted to 94, 87 and 70 turn tube(-1) during the 2003 growing season, respectively. Fine root mortality in treated plots did not change over the course of the study. We suggest that leaving logging residues on fertile sites may result in nitrogen mineralisation, which may in turn induce reductions in root biomass, and both root and mycelium production, and consequently affect nutrient uptake and the accumulation of organic carbon in soil derived from roots and mycorrhizae.
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