Extensive Wall Research Articles

Genome-wide identification, and phylogenetic and expression profiling analyses, of XTH gene families in Brassica rapa L. and Brassica oleracea L.

BackgroundXyloglucan endotransglucosylase/hydrolase genes (XTHs) are a multigene family and play key roles in regulating cell wall extensibility in plant growth and development. Brassica rapa and Brassica oleracea contain XTHs, but detailed identification and characterization of the XTH family in these species, and analysis of their tissue expression profiles, have not previously been carried out.ResultsIn this study, 53 and 38 XTH genes were identified in B. rapa and B. oleracea respectively, which contained some novel members not observed in previous studies. All XTHs of B. rapa, B. oleracea and Arabidopsis thaliana could be classified into three groups, Group I/II, III and the Early diverging group, based on phylogenetic relationships. Gene structures and motif patterns were similar within each group. All XTHs in this study contained two characteristic conserved domains (Glyco_hydro and XET_C). XTHs are located mainly in the cell wall but some are also located in the cytoplasm. Analyses of the mechanisms of gene family expansion revealed that whole-genome triplication (WGT) events and tandem duplication (TD) may have been the major mechanisms accounting for the expansion of the XTH gene family. Interestingly, TD genes all belonged to Group I/II, suggesting that TD was the main reason for the largest number of genes being in these groups. B. oleracea had lost more of the XTH genes, the conserved domain XET_C and the conserved active-site motif EXDXE compared with B. rapa, consistent with asymmetrical evolution between the two Brassica genomes. A majority of XTH genes exhibited different tissue-specific expression patterns based on RNA-seq data analyses. Moreover, there was differential expression of duplicated XTH genes in the two species, indicating that their functional differentiation occurred after B. rapa and B. oleracea diverged from a common ancestor.ConclusionsWe carried out the first systematic analysis of XTH gene families in B. rapa and B. oleracea. The results of this investigation can be used for reference in further studies on the functions of XTH genes and the evolution of this multigene family.

Internal Reference Gene Selection under Different Hormone Stresses in Multipurpose Timber Yielding Tree Neolamarckia cadamba

Neolamarckia cadamba, a member of the Rubiaceae family, is widely distributed throughout South Asia and South China. In order to acquire reliable and repeatable results, the use of a suitable internal reference gene to normalize the RT-qPCR data is essential. In this study, we reported the validation of housekeeping genes to identify the most suitable internal reference gene(s) for normalization of qPCR data obtained among different tissues (bud, leaf, cambium region) under different hormone stresses. Here, ΔCt, geNorm, NormFinder, and BestKeeper analyses were carried out to analyze the normalization of qPCR data of twenty-one reference gene families (ACT, CAC, CYP, EF1α, eIF, FPS1, FBK, GAPDH, RAN, PEPKR1, PP2A, RPL, RPS, RuBP, SAMDC, TEF, Tub-α, Tub-β, UBCE, UBQ, UPL) including 43 genes. The results showed that FPS1, RPL, and FBK were the most stable reference genes across all of the tested samples. In addition, the expression of NcEXPA8, one gene of interest that plays an important role in regulating cell wall extension, under different phytohormone stresses was used to further confirm the validated reference genes. Taken together, our results provide guidelines for reference gene selection under different phytohormone stresses and a foundation for more accurate and widespread use of RT-qPCR in N. cadamba.

Super-Resolution Microscopy and Single-Molecule Tracking Reveal Distinct Adaptive Dynamics of MreB and of Cell Wall-Synthesis Enzymes.

The movement of filamentous, actin-like MreB and of enzymes synthesizing the bacterial cell wall has been proposed to be highly coordinated. We have investigated the motion of MreB and of RodA and PbpH cell wall synthesis enzymes at 500 ms and at 20 ms time scales, allowing us to compare the motion of entire MreB filaments as well as of single molecules with that of the two synthesis proteins. While all three proteins formed assemblies that move with very similar trajectory orientation and with similar velocities, their trajectory lengths differed considerably, with PbpH showing shortest and MreB longest trajectories. These experiments suggest different on/off rates for RodA and PbpH at the putative peptidoglycan-extending machinery (PGEM), and during interaction with MreB filaments. Single molecule tracking revealed distinct slow-moving and freely diffusing populations of PbpH and RodA, indicating that they change between free diffusion and slow motion, indicating a dynamic interaction with the PGEM complex. Dynamics of MreB molecules and the orientation and speed of filaments changed markedly after induction of salt stress, while there was little change for RodA and PbpH single molecule dynamics. During the stress adaptation phase, cells continued to grow and extended the cell wall, while MreB formed fewer and more static filaments. Our results show that cell wall synthesis during stress adaptation occurs in a mode involving adaptation of MreB dynamics, and indicate that Bacillus subtilis cell wall extension involves an interplay of enzymes with distinct binding kinetics to sites of active synthesis.

Intraoperative Classification of Cholesteatoma Using ChOLE Classification and Evaluating its Treatment Outcomes Using Inside Out Approach Mastoidectomy.

The primary objective is to classify acquired cholesteatoma according to the ChOLE classification system based on the preoperative and intraoperative findings, and to describe prevalence of each stage. The secondary objective is to correlate the extent of inside out approach mastoidectomy required with the staged extent of cholesteatoma. A non-randomized Prospective Observational study conducted in 67 patients in a tertiary care hospital. Each case was categorized according to the ChOLE classification system including cholesteatoma extension, ossicular chain status, life threatening complications and eustachian tube dysfunction. Based on the extent of disease, inside out approach mastoidectomy was done and results analysed. Most patients presented with stage 2 disease [67%]. Canal wall was preserved for all stage I, and in stage II cholesteatoma canal wall was either kept intact, reconstructed or lowered based on the extent of erosion of posterior meatal wall and cholesteatoma extension. All stage III underwent canal wall down mastoidectomy. Staging of cholesteatoma by ChOLE classification allows standardization in reporting gravity of disease and surgical outcomes. Inside out approach mastoidectomy contributes to the successful surgical management of cholesteatoma by eradicating the disease with the creation of a smaller cavity.

Morphology Evolution of the Midlatitude Ionospheric Trough in Nighttime Under Geomagnetic Quiet Conditions

AbstractThe dynamics and climatology of midlatitude trough minimum have been widely investigated. However, the detailed magnetic local time (MLT) evolution of the trough walls (both equatorward and poleward) has not been well addressed. In this study, we used nearly 10‐year Planar Langmuir Probe (PLP) data from the CHAMP satellite to investigate how the location and shape of midlatitude trough evolve during night hours. We find that (1) the trough equatorward wall experiences an obvious equatorward extension in the premidnight sector, with steepness rapidly decreasing during the same local time sector; (2) the trough equatorward wall is as steep as poleward wall in the dusk sector; and (3) the trough poleward wall shows no remarkable change during the whole nighttime, except for a weakly reduced width and a slightly enhanced steepness near midnight. We suggest that the rapid extension of the equatorward wall in the premidnight sector is closely related to the plasma equatorward movement caused by the neutral winds. The rapid decrease of the steepness of the equatorward wall in the premidnight sector is not only influenced by its own width expansion but possibly also related to the upward plasma drift caused by neutral winds. The trough minimum and equatorward/poleward boundaries are found located at slightly higher magnetic latitude during equinoxes than that during solstice seasons.

Identification of Genes Involved in Root Growth Inhibition Under Lead Stress by Transcriptome Profiling in Arabidopsis

Lead (Pb) is a heavy metal with high toxicity to plants. Root is the major organ to respond to Pb stress. However, little is known about how plant roots perceive Pb stress signaling. Here, we describe the transcriptome of Arabidopsis root tips under Pb stress using the RNA-seq assay. A total of 703 differentially expressed genes (DEGs) were identified and expressed at every time points. Some early-responsive DEGs (1 h) were predicted to be negatively involved in cell elongation and cell expansion, while some late-responsive DEGs (24 h) positively participated in defense of oxidative stress. Hydrogen peroxide (H2O2) and superoxide (O2−) were increased significantly in root tips under Pb stress. Cell wall extension related gene XYLOGLUCAN ENDOTRANSGLUCOSYLASE/HYDROLASE 18 (XTH18) was induced in root tips, and xth18 showed reduced root growth inhibition by Pb stress. Our results revealed the potential mechanism of root growth inhibition by Pb stress and shed light for the further study.

Unidirectional tilt of domain walls in equilibrium in biaxial stripes with Dzyaloshinskii–Moriya interaction

The orientation of a chiral magnetic domain wall in a racetrack determines its dynamical properties. In equilibrium, magnetic domain walls are expected to be oriented perpendicular to the stripe axis. We demonstrate the appearance of a unidirectional domain wall tilt in out-of-plane magnetized stripes with biaxial anisotropy and Dzyaloshinskii–Moriya interaction (DMI). The tilt is a result of the interplay between the in-plane easy-axis anisotropy and DMI. We show that the additional anisotropy and DMI prefer different domain wall structure: anisotropy links the magnetization azimuthal angle inside the domain wall with the anisotropy direction in contrast to DMI, which prefers the magnetization perpendicular to the domain wall. Their balance with the energy gain due to domain wall extension defines the equilibrium magnetization the domain wall tilting. We demonstrate that the Walker field and the corresponding Walker velocity of the domain wall can be enhanced in the system supporting tilted walls.

Golgi-localized exo-β1,3-galactosidases involved in cell expansion and root growth in Arabidopsis

Plant arabinogalactan proteins (AGPs) are a diverse group of cell surface- and wall-associated glycoproteins. Functionally important AGP glycans are synthesized in the Golgi apparatus, but the relationships among their glycosylation levels, processing, and functionalities are poorly understood. Here, we report the identification and functional characterization of two Golgi-localized exo-β-1,3-galactosidases from the glycosyl hydrolase 43 (GH43) family in Arabidopsis thaliana GH43 loss-of-function mutants exhibited root cell expansion defects in sugar-containing growth media. This root phenotype was associated with an increase in the extent of AGP cell wall association, as demonstrated by Yariv phenylglycoside dye quantification and comprehensive microarray polymer profiling of sequentially extracted cell walls. Characterization of recombinant GH43 variants revealed that the exo-β-1,3-galactosidase activity of GH43 enzymes is hindered by β-1,6 branches on β-1,3-galactans. In line with this steric hindrance, the recombinant GH43 variants did not release galactose from cell wall-extracted glycoproteins or AGP-rich gum arabic. These results indicate that the lack of exo-β-1,3-galactosidase activity alters cell wall extensibility in roots, a phenotype that could be explained by the involvement of galactosidases in AGP glycan biosynthesis.

Biomicroscopy of the bulbar conjunctiva: the possibilities of the method in assessing microcirculatory disorders in systemic sclerosis

Relevance. In this article, the authors draw the attention of readers to the modern possibilities of using the biomicroscopy of the bulbar conjunctiva (BMBC) method in the diagnosis of microcirculatory (MC) disorders in systemic sclerosis (SS). Comparison of BMBC results of patients with SS with a control group allowed us to identify microcirculatory signs of this disease, and comparison the changes detected during nail capillaroscopy (NC) showed additional diagnostic capabilities of the BMBC method. The aim of the study was to identify new MC signs in SS using the BMBC-method, which can be further used to assess the dynamics and search for patterns with the clinical picture. Materials and methods. 48 patients with SS, the average age was 51±1.7 years were examined by BMBC, the ratio of women to men was 46:2, respectively. The control group consisted of healthy individuals without any diseases that could affect to the microcirculatory bed (MCB); the average age was 47.4±2.3 years, and the ratio of women to men was 20:10. The results showed statistically significant changes in angioarchitectonics among patients with SS compared with the control. A significant decrease in the average diameter of arterioles (14.1±0.7 μm) and capillaries (6.6±0.2 μm) was observed in the group of patients with SS compared with the control (16.6±0.6 μm, p=0.0165 and 7.3±0.2 μm, p=0.0356, respectively, for arterioles and capillaries). The decrease in capillaries during SS in four regions of the temporal section of the bulbar conjunctiva was incremental and amounted to: 15.3% in the area of the angle of the eye, 23.3% in the transitional region, 28.1% in the central and 37.9% in the perilimbal in comparison with the control. Conclusions. The BMBC-method is highly informative in the diagnosis of MC-disorders in SS. The main BMBC changes in the MC disorders caused by SS are the disturbance of MCB by the increasing tortuosity of microvessels, the contour discontinuity and the presence of local wall extensions. A peculiarity is the reduction of the capillary bed in all four regions of the temporal section of the bulbar conjunctiva with a maximum in the perilymb area.

A hybrid multiphase flow model for the prediction of both low and high void fraction nucleate boiling regimes

The improvement of a hybrid (a combination of Volume-of-Fluid (VOF) and Eulerian model) multiphase flow solver for the numerical prediction of high- and low-void fraction flow boiling regimes is presented in this article. These flow regimes could simultaneously occur in core-catcher and in-vessel retention-external reactor cooling systems during a severe accident in nuclear power plant. To enhance the prediction of the low void fraction boiling regime, a turbulent rough wall function model is implemented in the hybrid model to reproduce the impact of coarseness induced by the existence of growing bubbles along the heating wall on the liquid velocity profile. With this wall function, a more accurate prediction of the radial velocity profile is achieved within the uncertainty of the velocity measurements. Moreover, an improved prediction of the radial void fraction is achieved using the model proposed by Lopez de Bertodano for turbulence dispersion force without compromising the prediction of the radial gas velocity profile and radial liquid temperature profile. Although the hybrid model shows potential in capturing the interface and dynamic behavior of large-scale bubbles (vapor slug) for high void fraction regime, the predicted wall superheat is higher than the measured values. This highlighted the need for the extension of the present wall boiling model to cover flow boiling involving sliding vapor slugs on the heated wall.

A novel endo-β-1,6-glucanase from the mushroom Coprinopsis cinerea and its application in studying of cross-linking of β-1,6-glucan and the wall extensibility in stipe cell walls

We previously reported that chitinases reconstituted heat-inactivated stipe cell wall extension in a steady and continuous extension profile by cleaving chitins cross-linked to various polysaccahrides, whereas, endo-β-1,3-glucanases reconstituted heat-inactivated stipe wall extension in a profile of an initially fast extension and subsequent termination of extension due to its degradation of β-1,3-glucan but not other polysaccharides such as β-1,6-glucans cross-linked to chitins. Thus, a novel endo-β-1,6-glucanase, GH30A, from Coprinopsis cinerea was cloned and characterized to study cross-linking of β-1,6-glucan and wall extensibility in stipe walls. GH30A had higher activity and better thermophilicity than reported β-1,6-glucanases. GH30A hydrolyzed pustulan having β-1,6-linkages but not other polysaccharides without β-1,6-linkages; GH30A did not cleave gentiobiose and single β-1,6-linkage branches in laminarin from Laminaria digitata but cut consecutive β-1,6-linkage branches in laminarin from Eisenia bicyclis. GH30A reconstituted heated-inactivated stipe cell wall extension with release of glucose and gentiobiose, indicating that β-1,6-glucans were present and cross-linked to chitins in stipe walls, and cleaving β-1,6-glucans cross-linked to chitins by GH30A led to wall loosening for extension. However, GH30A individually or in combination with endo-β-1,3-glucanase reconstituted-stipe wall extension profile was similar to individual endo-β-1,3-glucanase's, exploring that chitins were also cross-linked to other polysaccharides besides β-1,3-glucans and β-1,6-glucans.

Dual functions of Expansin in cell wall extension and compression during cotton fiber development

Cotton fiber provides a distinct picture of cell wall synthesis. It is an epidermal single-cell extension of Cotton plant seed and undergoes three main stages of development, (1) initiation, (2) elongation and (3) maturation. The fiber initiation characterized by thin primary cell wall formation, which is extended afterward by the action of specific non-enzymatic proteins called Expansins, which promote expansion between cellulose microfibrils by cutting the bridges between cellulose and Hemicellulose residues. The elongation phase followed by a compression phase where the secondary cell wall becomes compact and thickened by the deposition of polysaccharides. The fiber development eventually ends up in the maturation phase, attaining the final maximum length of ∼2.5–3.0 cm. However, the most critical periods of Cotton fiber development are cell wall extension and cellulose deposition. Many studies have focused on the role of Expansins in cell wall elongation, but the significance of expansins in cellulose deposition of the secondary cell wall has barely studied to date. This paper, therefore, is a brief review, which will emphasize the role of Expansin in both cell wall extensibility and polysaccharide deposition during the compression phase. However, the versatile role of Expansin proteins in cellulose deposition and cell wall elongation need a more critical experimental approach.

Immunocytochemistry and Density Functional Theory evidence the competition of aluminum and calcium for pectin binding in Urochloa decumbens roots

Root growth is reduced in soils with low pH [H+] and abundant soluble aluminum [Al3+], which can be a consequence of the interaction between Al3+ and cell wall composition. The competition between Al3+ and Ca2+ toward binding to pectin molecules was evaluated in roots of Urochloa decumbens, an African grass highly adapted to acidic Al-rich soils. Variations in the composition and distribution of pectins can change the extensibility, rigidity, porosity, and adhesive properties of plant cell walls, which were tested in seedlings of U. decumbens exposed to pH 3.5, 4.5 and 5.8 and to 0, 80, 160 and 320 μM of Al3+ for 80h. Root growth corroborated that U. decumbens is very tolerant to soil acidity, with effective reduction of root growth only at pH 3.5. Immunocytochemical approaches demonstrated variations in pectin composition induced both by Al3+ and by H+ in root tissues and zones. Based on the usual linkage between Ca2+ and pectins, Density Functional Theory (DFT) analyses indicated that Al3+ bound easier to pectins than Ca2+ did, leading to the formation of more Al3+-pectate complexes than Ca2+-pectate complexes, which resulted in higher rigidity of cell walls, and hampered cell extension.

The Proline-Rich Family Protein EXTENSIN33 Is Required for Etiolated Arabidopsis thaliana Hypocotyl Growth.

Growth of etiolated Arabidopsis hypocotyls is biphasic. During the first phase, cells elongate slowly and synchronously. At 48 h after imbibition, cells at the hypocotyl base accelerate their growth. Subsequently, this rapid elongation propagates through the hypocotyl from base to top. It is largely unclear what regulates the switch from slow to fast elongation. Reverse genetics-based screening for hypocotyl phenotypes identified three independent mutant lines of At1g70990, a short extensin (EXT) family protein that we named EXT33, with shorter etiolated hypocotyls during the slow elongation phase. However, at 72 h after imbibition, these dark-grown mutant hypocotyls start to elongate faster than the wild type (WT). As a result, fully mature 8-day-old dark-grown hypocotyls were significantly longer than WTs. Mutant roots showed no growth phenotype. In line with these results, analysis of native promoter-driven transcriptional fusion lines revealed that, in dark-grown hypocotyls, expression occurred in the epidermis and cortex and that it was strongest in the growing part. Confocal and spinning disk microscopy on C-terminal protein-GFP fusion lines localized the EXT33-protein to the ER and cell wall. Fourier-transform infrared microspectroscopy identified subtle changes in cell wall composition between WT and the mutant, reflecting altered cell wall biomechanics measured by constant load extensometry. Our results indicate that the EXT33 short EXT family protein is required during the first phase of dark-grown hypocotyl elongation and that it regulates the moment and extent of the growth acceleration by modulating cell wall extensibility.

MsPG1 alleviated aluminum-induced inhibition of root growth by decreasing aluminum accumulation and increasing porosity and extensibility of cell walls in alfalfa (Medicago sativa)

Pectins are abundant in the primary cell walls and involve in regulating intercellular adhesion. MsPG1gene was cloned from alfalfa and its function of Al tolerance was tested in vivo and vitro. Results showed that the expression of MsPG1 was increased by Al, and the MsPG1 was localized in the plasma membrane of epidermal cells in root apexes. Overexpression of MsPG1 in hairy roots of alfalfa increased root growth in the present of Al, which was attributed to the decreased Al accumulations in pectins, hemicellulose 1 (HC1), cell walls and root apexes conferred by the decreased content of HC1 and ratios of negatively charged functional groups (−OH and −COOH) in cell wall. The decreased Al accumulations in pectins and cell walls were also observed in incubation MsPG1 with pectins and cell walls in vitro. TEM and FESEM assays showed that overexpression of MsPG1 protected the cell microstructure of root apexes, and increased the porosity and pore size of porous lattice-like structure of cell wall in the present of Al. These results indicated that MsPG1 could increase Al tolerance of alfalfa via decreasing Al accumulation in cell wall and increasing the porosity and extensibility of cell wall under excess Al stress.

Mechanobiology: Plant Cells Face Pressure from Neighbors.

Plant cell growth is constrained by the rate of water uptake and wallextensibility. New research reveals that the topology and geometry of cells in a tissue predicts the pressures that ultimately determine growth.

Cellular Heterogeneity in Pressure and Growth Emerges from Tissue Topology and Geometry.

Cell-to-cell heterogeneity prevails in many systems, as exemplified by cell growth, although the origin and function of such heterogeneity are often unclear. In plants, growth is physically controlled by cell wall mechanics and cell hydrostatic pressure, alias turgor pressure. Whereas cell wall heterogeneity has received extensive attention, the spatial variation of turgor pressure is often overlooked. Here, combining atomic force microscopy and a physical model of pressurized cells, we show that turgor pressure is heterogeneous in the Arabidopsis shoot apical meristem, a population of stem cells that generates all plant aerial organs. In contrast with cell wall mechanical properties that appear to vary stochastically between neighboring cells, turgor pressure anticorrelates with cell size and cell neighbor number (local topology), in agreement with the prediction by our model of tissue expansion, which couples cell wall mechanics and tissue hydraulics. Additionally, our model predicts two types of correlations between pressure and cellular growth rate, where high pressure may lead to faster- or slower-than-average growth, depending on cell wall extensibility, yield threshold, osmotic pressure, and hydraulic conductivity. The meristem exhibits one of these two regimes, depending on conditions, suggesting that, in this tissue, water conductivity may contribute to growth control. Our results unravel cell pressure as a source of patterned heterogeneity and illustrate links between local topology, cell mechanical state, and cell growth, with potential roles in tissue homeostasis.

Ascorbate in the Apoplast: Metabolism and Functions

Ascorbic acid (AA) is one of the most important antioxidants and redox-active substances of plants found in the apoplast. In the form of ascorbate anion, it can be exported to the cell wall through anion channels, where it is further oxidized to dehydroascorbic acid (DHA) and in this form is translocated back into the cytoplasm through as yet unidentified transporters. In the apoplast AA is exposed to both enzymatic and non-enzymatic oxidation, participating in the antioxidant and pro-oxidant processes: detoxification of O3, generation of hydroxyl radicals, reduction of phenoxyl radicals, etc. The intermediate product of the AA oxidation in apoplast, monodehydroascorbic acid (MDHA), serves as an extracellular electron acceptor for a number of redox chains localized at the plasma membrane (PM). All three forms of ascorbate, AA, DHA and MDHA, can potentially be involved in the cell signalling. Released from the cell through anionic channels during PM depolarization, AA can stimulate the production of hydroxyl radicals that activate Ca2+-permeable channels, and thus trigger Ca2+-signalling. Due to the ability to generate hydroxyl radicals and reduce phenoxyl radicals, AA affects cell wall extensibility and extension growth. By reducing Fe3+ to a freely soluble transport form of Fe2+, AA is involved in iron uptake by root cells. Apoplastic AA also plays an important role in a number of other processes and is potentially a unique signal-regulatory molecule functioning in the plant cell walls.

Function of NHX-type transporters in improving rice tolerance to aluminum stress and soil acidity.

In this study, we show that ectopic expression of either HtNHX1 or HtNHX2, from Helianthus tuberosus plant (located at vacuolar and endosome membranes, respectively), in rice plants could enhance its tolerance to aluminum (Al3+) stress and soil acidity. Plant sodium (potassium)/proton (Na+(K+)/H+ antiporters of the NHX family have been extensively characterized as they are related to the enhancement of salt tolerance. However, no previous study has reported NHX transporter functions in plant tolerance to Al3+ toxicity. In this study, we demonstrate their role as a component of the Al3+ stress tolerance mechanism. We show that the ectopic expression of either HtNHX1 or HtNHX2 , from Helianthus tuberosus plant, in rice (located at vacuole and endosome, respectively) could also enhance rice tolerance to Al3+ stress and soil acidity. Expression of either HtNHX1 or HtNHX2 reduced the inhibitory effect of Al3+ on the rice root elongation rate; both genes were reported to be equally effective in improvement of stress conditions. Expression of HtNHX1 enhanced Al3+-trigged-secretion of citrate acids, rhizosphere acidification, and also reduced K+ efflux from root tissues. In contrast, expression of HtNHX2 prevented Al3+-trigged-decrease of H+ influx into root tissues. Al3+-induced damage of the cell wall extensibility at the root tips was impaired by either HtNHX1 or HtNHX2. Co-expression of HtNHX1 and HtNHX2 further improved rice growth, particularly under the Al3+ stress conditions. The results demonstrate that HtNHX1 and HtNHX2 improved rice tolerance to Al3+ via different mechanisms by altering the K+ and H+ fluxes and the cell wall structure.

Comparative study of β-glucan-degrading enzymes from Coprinopsis cinerea for their capacities to induce stipe cell wall extension

We previously reported endo-β-1,3-glucanase ENG in combination with β-glucosidase BGL2 at low concentration induced stipe cell wall extension. This study further explored ENG could be replaced by endo-β-1,3(4)-glucanase ENG16A in combination with BGL2 to induce stipe cell wall extension; similarly, BGL2 could be replaced by β-glucosidase BGL1 to cooperate with ENG to induce stipe cell wall extension. However, ENG could not be replaced by exo-β-1,3-glucanase EXG in combination with BGL2 to induce stipe cell wall extension, although EXG alone released higher level of soluble sugars from the stipe cell walls during the reconstituted wall extension than that released from the stipe cell walls by a combination of ENG16A or ENG and BGL2 or BGL1, which was different from chitinase-mediated stipe cell wall extension. These results indicate endo-β-1,3-glucanases loosen the stipe cell wall, whereas exo-β-1,3-glucanases and β-glucosidases play a synergistic role to maintain a low and efficient concentration of endo-β-1,3-glucanases for stipe cell wall extension. Furthermore, ENG was expressed at a very high level in the matured pilei, in contrast, ENG16A was expressed at a very high level in the elongating apical stipe. Therefore, ENG16A might be involved in stipe elongation growth, while ENG might participate in autolysis of pilei.