Plasma membrane aquaporins of the PIP1 and PIP2 subfamilies facilitate hydrogen peroxide diffusion into plant roots.

BACKGROUND: The permeability of plasma membrane aquaporins (PIPs) to small solutes other than water greatly diversifies their potential functions in plant development and metabolic processes. One such process is stress signalling in which hydrogen peroxide (H2O2) plays a major role. Based on transport assays carried out in yeast, there are differences in the degree to which PIPs of Arabidopsis thaliana, are permeable to H2O2 and thus they may differentially facilitate transmembrane diffusion. Here, we test whether specific PIPs aid in the transmembrane diffusion of H2O2 to such an extent that knocking-out PIPs affects plant phenotype. We examined changes in growth and morphology, including biomass accumulation, root system architecture and relative water content, as well as gas exchange, across two H2O2 treatments in knockout mutants of A. thaliana. RESULTS: We could infer that PIP-type aquaporins are permeable to H2O2 in planta and that this permeability is physiologically relevant in a plant's response to oxidative stress. In particular, the lack of functional PIP2;3 confers resistance to exogenously applied H2O2 indicating that it facilitates H2O2 entry into root cells. Additionally, PIP1;1 and PIP2;6 were found to facilitate H2O2 diffusion, while PIP2;2 is required for proper root growth under controlled conditions. MAIN FINDINGS: We conclude that PIPs are physiologically relevant conduits for H2O2 diffusion in the A. thaliana roots and participate in the regulation of stress responses.

Formation of Heterogeneous Microstructure in AA1050/AA5052/AA6061/AA1050 Layered Sheet Processed by Cold Roll-Bonding and Subsequent Annealing.

A cold roll-bonding process was applied to fabricate an AA1050/AA6061/AA5052/AA1050 four-layer clad sheet and subsequently annealed. Three types of aluminum alloy sheets such as AA1050, AA6061 and AA5052 with 2 mm thickness, 40 mm width and 300 mm length were stacked up each other after such surface treatment as degreasing and wire brushing, then reduced to a thickness of 2 mm by multi-pass cold rolling. The rolling was performed at ambient temperature without lubricant using a 2-high mill with a roll diameter of 400 mm at rolling speed of 6.0 m/sec. The roll bonded AA1050/AA6061/AA5052/AA1050 clad sheet was then annealed for 0.5 h at 200~400 °C. Microstructures of the as-roll bonded and subsequently annealed aluminum sheets are investigated by electron back scatter diffraction (EBSD) measurement. After rolling, the roll-bonded AA1050/AA5052/AA6061/AA1050 sheet showed a typical deformation structure that the grains are largely elongated to the rolling direction. However, after annealing, it exhibits a very heterogeneous structure consisting of both deformation structure and recrystallization structure containing nanometer order grains. The formation of this heterogeneous structure and texture with annealing is investigated in detail through EBSD analysis.

The Effect of Mn and Ca Addition on the Microstructure and Mechanical Properties of the Al-Cu-Fe-Si-Zn Based Alloys.

High conductivity Al alloys are widely used for electric materials, heat exchangers, and heat dissipation parts such as electric conductors, transmission lines, communication cables, automobile wires and so on. In this study, the effects of Ca and Mn addition on the microstructure and mechanical properties of Al-0.3Cu-0.2Fe-0.15Si-0.15Zn alloys were investigated. The melt was held at 800 °C for 20 minutes and poured into a mold. The cast Al alloy was hot extruded with a rod having a diameter of 12 mm and a reduction ratio of 38:1. Al-0.3Cu-0.2Fe-0.15Si-0.15Zn-0.9Mn-0.4Ca alloy consists of Al, Al-(Fe, Mn)-Si, Al-(Fe, Mn) and Al-(Ca) intermetallic compounds. The formation of the intermetallic compound and this phase was broken in to small particles during extrusion. As the Ca content increased from 0 to 0.4 wt.%, the electrical conductivity of the extruded Al-0.3Cu- 0.2Fe-0.15Si-0.15Zn alloys increased by 57.3, 57.9 and 59.0 %IACS (International annealed copper standard). Al-0.3Cu-0.2Fe-0.15Si-0.15Zn-0.9Mn alloy with element additions of Ca, ultimate tensile strength was decreased from 178.3 to 163.2 and 151.8 MPa. However, the elongation was improved to 18.6, 21.6 and 23.15%.

Microstructural Changes with Annealing of a Nanostructured Al Alloy Severely Plastic Deformed by Four-Layer Stack Accumulative Roll-Bonding Process.

Microstructural changes with annealing of a nanostructured complex aluminum alloy fabricated by 3 cycles of four-layer stack ARB process using different Al alloys were investigated in detail. The four-layer stack ARB process using AA1050, AA5052 and AA6061 alloy sheets was performed up to 3 cycles without a lubricant at room temperature. The sample fabricated by the ARB is a multi-layer aluminum alloy sheet in which the AA1050, AA5052 and AA6061 aluminum alloys are alternately stacked to each other. The layer thickness of each alloy became thinner and elongated to the rolling direction with the number of ARB cycles. The grain size decreased with increasing of the number of ARB cycles, and became about 160 nm in thickness after 3 cycles. The complex Al alloy still showed ultrafine grained microstructure to annealing temperature of 300 °C, but it had a heterogeneous structure containing both the ultrafine grains and the coarse grains due to an occurrence of discontinuous recrystallization after 350 °C.

Analysis of Microstructure and Electric Conductivity in Al-RE Alloy by Heat-Treatment Condition.

In this study, we investigate the microstructure and mechanical properties of as-extruded Al-1.0RE alloys. The molten Aluminum alloy was maintained at 800 °C and then poured into a mould at 200 °C. Aluminum alloys were hot-extruded into a rod measuring 12 mm thick with a reduction ratio of 38:1. The microstructure and electric conductivity properties of as-extruded Al-1.0RE alloy under different annealing processes were investigated and compared. After extrusion, the intermetallic compound having a needle shape in the cast state was finely decomposed based on the direction of extrusion. Significant changes in the microstructure were detected after annealing at 500 °C with fragmentation and sphering of eutectic particles. The annealing temperature of Al-1.0RE alloy increased proportionally to the electrical conductivity. The formation of Al-RE intermetallic compounds increases the electrical conductivity and improves the mechanical properties of the alloy through precipitation hardening.

Regulation of water transport in Arabidopsis by methyl jasmonate.

Following a stress event, jasmonate-dependent signaling pathway triggers a shift from growth to defense responses that are accompanied by the cessation of growth in many plants. However, the processes leading to this growth inhibition remain obscure. In this study, we provide evidence for a rapid inhibition of cell hydraulic conductivity (Lp) by methyl jasmonate (MeJA) in the roots of wild-type Arabidopsis within 0.5 h of 20 and 50 µM MeJA treatments. We also demonstrate that MeJA did not affect Lp in fad3-2 and fad7-2 Arabidopsis mutants that are deficient in jasmonate precursor, linolenic acid. The reductions of Lp in wild-type plants were accompanied by the down-regulation of several plasma membrane intrinsic protein (PIP) isoforms, and dephosphorylation. Treatments with HgCl2 did not further reduce Lp in the wild-type plants, but significantly reduced Lp in the fad3-2 and fad7-2 that had been first treated with MeJA. Continuous prolonged exposure to exogenous 50 µM MeJA inhibited the relative growth rates (RGR) of shoots and net photosynthesis (Pn) in the Arabidopsis wild-type and fad7-2 plants, but had no effect on the RGR of roots. The results demonstrated that a reduction of aquaporin (AQP)-mediated water transport was the initial target of MeJA exposure, and may contribute to the processes of growth inhibition by MeJA.

Microstructure and Mechanical Properties of Al-Si-Fe-Cu-Mn-x Zn Alloys Processed by Extrusion.

In this work, Al-0.15Si-0.2Fe-0.3Cu-0.9Mn alloys with different Zn addition (0, 0.15 and 0.3 wt%) were melted and extruded at 200 °C. The effect of Zn on the microstructure, texture evolution and mechanical properties of Al-0.15Si-0.2Fe-0.3Cu-0.9Mn alloys was investigated using scanning electron microscope (SEM), equipped with energy-dispersive X-ray spectrometry (EDS) and electron backscatter diffraction (EBSD) and in the present study. In order to evaluate the mechanical properties, we implemented the tensile tests by a universal material test machine. Al-0.15Si-0.2Fe- 0.3Cu-0.9Mn-xZ resulted in the formation of Al-(Fe, Mn)-Si and Al-(Fe, Mn) intermetallic compounds. The formation of the intermetallic compound and this phase was broken in to small particles during extrusion. The ultimate strength and elongation of the as-extruded Al-0.15Si-0.2Fe-0.3Cu- 0.9Mn alloy were 96.51 MPa and 34.01%, while those of the Al-0.15Si-0.2Fe-0.3Cu-0.9Mn-0.3Zn alloy were 99.08 MPa and 36.21%, respectively. Al-0.15Si-0.2Fe-0.3Cu-0.9Mn alloys with Zn addition resulted in improving the strength with no reduction in elongation.

[Primary Hepatic Schwannoma].

A primary benign schwannoma of the liver is extremely rare. Only 30 cases have been reported in the medical literature worldwide, and only one case has been reported in Korea previously. A 56-year-old man was admitted to Gil Medical Center with incidental findings of a hepatic mass by abdominal computed tomography. The computed tomography and magnetic resonance image revealed a 3×2 cm-sized solid mass in the left lobe of the liver. Histological examination confirmed the diagnosis of a benign schwannoma, proven by positive immunoreaction with the neurogenic marker S-100 protein and a negative response to CD34, CD117, and smooth muscle actin. We report a primary benign schwannoma of the liver and review the literature.

Water transport properties of root cells contribute to salt tolerance in halophytic grasses Poa juncifolia and Puccinellia nuttalliana.

Plant water uptake and aquaporin-mediated root water transport are among the most salt-sensitive processes in most plants, but even relatively high salt concentrations do not appear to impair water transport processes in halophytes. To develop better understanding of these processes in halophytic plants, we compared the responses to NaCl of the two halophytic grasses varying in salt tolerance, Puccinellia nuttalliana and Poa juncifolia, with the glycophytic grass Poa pratensis. The plants were hydroponically grown and subjected to different NaCl concentrations for up to 10 days. At the lower NaCl concentrations, shoot and root dry weights were drastically reduced in Poa pratensis, but increased in Puccinellia nuttalliana and Poa juncifolia. The examined treatment concentrations of up to 300 mM NaCl had either no effect (Puccinellia nuttalliana) or little effect (Poa juncifolia) on the net photosynthesis and transpiration rates in plants, but severely decreased the gas exchange parameters in Poa pratensis. Similarly, to growth and gas exchange, leaf water content in Puccinellia nuttalliana was not affected even by the highest, 300 mM NaCl concentration, while Poa pratensis showed decreased shoot water content in all examined NaCl treatments and Poa juncifolia in 150 and 300 mM NaCl. Cell hydraulic conductivity in roots of Poa pratensis also showed high sensitivity to NaCl and was drastically reduced in all examined NaCl concentrations. Cell hydraulic conductivity in Poa juncifolia roots was less affected by NaCl compared with Poa pratensis and in Puccinellia nuttalliana, cell hydraulic conductivity increased in response to NaCl treatments. Both Puccinellia nuttalliana and Poa juncifolia accumulated less Na in their shoot tissues compared with Poa pratensis. The concentrations of K in the roots of Poa pratensis sharply decreased with increasing NaCl treatment concentrations while in Puccinellia nuttalliana, K root concentrations remained high in all NaCl treatments and in Poa juncifoila, root K decreased only in the 300 mM NaCl treatment. Since K efflux from the cytoplasm can contribute to the acidification of the cytoplasm, this process could potentially lead to the inhibition of aquaporin function and reduction of root hydraulic conductivity. The, significance of stable K root concentrations in the roots of halophytes should be further investigated as a possible salt tolerance mechanism that could contribute to the maintenance of aquaporin function and root water transport under salt stress conditions.

Effect of Mn and AlTiB Addition and Heattreatment on the Microstructures and Mechanical Properties of Al-Si-Fe-Cu-Zr Alloy.

The microstructure and mechanical properties of as-extruded Al-0.1 wt%Si-0.2 wt%Fe- 0.4 wt%Cu-0.04 wt%Zr-xMn-xAlTiB (x = 1.0 wt%) alloys under various annealing processes were investigated and compared. After the as-cast billets were kept at 400 °C for 1 hr, hot extrusion was carried out with a reduction ratio of 38:1. In the case of the as-extruded Al-Si-Fe-Cu-Zr alloy at annealed at 620 °C, large equiaxed grain was observed. When the Mn content is 1.0 wt%, the phase exhibits a skeleton morphology, the phase formation in which Mn participated. Also, the volume fraction of the intermetallic compounds increased with Mn and AlTiB addition. For the Al-0.1Si-0.2Fe-0.4Cu-0.04Zr alloy with Mn and AlTiB addition from 1.0 wt%, the ultimate tensile strength increased from 100.47 to 119.41 to 110.49 MPa. The tensile strength of the as-extruded alloys improved with the addition of Mn and AlTiB due to the formation of Mn and AlTiB-containing intermetallic compounds.

Functionally redundant LNG3 and LNG4 genes regulate turgor-driven polar cell elongation through activation of XTH17 and XTH24.

KEY MESSAGE: In this work, we genetically characterized the function of Arabidopsis thaliana, LONGIFOLIA (LNG1), LNG2, LNG3, LNG4, their contribution to regulate vegetative architecture in plant. We used molecular and biophysical approaches to elucidate a gene function that regulates vegetative architecture, as revealed by the leaf phenotype and later effects on flowering patterns in Arabidopsis loss-of-function mutants. As a result, LNG genes play an important role in polar cell elongation by turgor pressure controlling the activation of XTH17 and XTH24. Plant vegetative architecture is related to important traits that later influence the floral architecture involved in seed production. Leaf morphology is the primary key trait to compose plant vegetative architecture. However, molecular mechanism on leaf shape determination is not fully understood even in the model plant A. thaliana. We previously showed that LONGIFOLIA (LNG1) and LONGIFOLIA2 (LNG2) genes regulate leaf morphology by promoting longitudinal cell elongation in Arabidopsis. In this study, we further characterized two homologs of LNG1, LNG3, and LNG4, using genetic, biophysical, and molecular approaches. Single loss-of-function mutants, lng3 and lng4, do not show any phenotypic difference, but mutants of lng quadruple (lngq), and lng1/2/3 and lng1/2/4 triples, display reduced leaf length, compared to wild type. Using the paradermal analysis, we conclude that the reduced leaf size of lngq is due to decreased cell elongation in the direction of longitudinal leaf growth, and not decreased cell proliferation. This data indicate that LNG1/2/3/4 are functionally redundant, and are involved in polar cell elongation in Arabidopsis leaf. Using a biophysical approach, we show that the LNGs contribute to maintain high turgor pressure, thus regulating turgor pressure-dependent polar cell elongation. In addition, gene expression analysis showed that LNGs positively regulate the expression of the cell wall modifying enzyme encoded by a multi-gene family, xyloglucan endotransglucosylase/hydrolase (XTH). Taking all of these together, we propose that LNG related genes play an important role in polar cell elongation by changing turgor pressure and controlling the activation of XTH17 and XTH24.

Evolution of Nanostructure Through Thickness of Deoxidized Low-Phosphorous Copper by Three-Layer Stack Accumulative Roll-Bonding.

A nanostructured deoxidized low-phosphorous copper (DLPC) was fabricated by three-layer stack accumulative roll-bonding process. Three sheets of 1 mm in thickness, 30 mm in width and 300 mm in length were stacked up and roll-bonded to thickness of 1 mm by two-pass cold rolling. The bonded sheet was cut in three pieces of same length, then stacked up and roll-bonded to the thickness of 1 mm again. The evolution of nanostructure through thickness with three-layer stack ARB were investigated in detail. It was found that the microstructure has been evolved from a dislocation cell structure to a nano grained structure with the proceeding of ARB cycles. The average grain thickness of 45 µm in initial decreased to 170 nm after 7 cycles of the ARB. The heterogeneity in microstructure through thickness was also largely decreased by the ARB. These results suggest that three-layer stack ARB is an effective process for a formation of nanostructure of DLPC alloy.

Characteristics of Nano Grained AA1050/AA5052 Al Sheets Fabricated by Accumulative Roll-Bonding.

Accumulative roll-bonding (ARB) is the most appropriate process for sheet-shaped materials because it can be carried out readily by utilizing the conventional rolling apparatus. In this study, a nanostructured AA1050/AA5052 Al alloy sheet was successfully fabricated by four-layer stack ARB process. The ARB of AA1050 and AA5052 alloy sheets was performed up to 6 cycles without a lubricant at ambient temperature. The sample fabricated by the ARB was a multi-layer aluminum alloy sheet in which AA1050 and AA5052 layers are alternately stacked. The layer thickness of the each alloy became thinner and elongated to the rolling direction with the number of ARB cycles. The grain size decreased with increasing of the number of ARB cycles, after 6 cycles it became about 180 nm in thickness. The fraction of high angle grain boundaries increased with the number of ARB cycles. The tensile strength also increased with the ARB, it reached 305 MPa which is about 2.1 times that of the as-received AA1050. The mechanical properties of a multi-layer AA1050/AA5052 alloy fabricated by the ARB were compared to those of the other materials.

Grain Refinement of Al-Si-Fe-Cu-Zn-Mn Based Alloy by Al-Ti-B Alloy and Its Effect on Mechanical Properties.

We investigated the effects of Al-5.0wt%Ti-1.0wt%B addition on the microstructure and mechanical properties of the as-extruded Al-0.15wt%Si-0.2wt%Fe-0.3wt%Cu-0.15wt%Zn-0.9wt%Mn based alloys. The Aluminum alloy melt was held at 800 °C and then poured into a mould at 200 °C. Aluminum alloys were hot-extruded into a rod that was 12 mm in thickness with a reduction ratio of 38:1. AlTiB addition to Al-0.15Si-0.2Fe-0.3Cu-0.15Zn-0.9Mn based alloys resulted in the formation of Al3Ti and TiB2 intermetallic compounds and grain refinement. With increasing of addition AlTiB, ultimate tensile strength increased from 93.38 to 99.02 to 100.01 MPa. The tensile strength of the as-extruded alloys was improved due to the formation of intermetallic compounds and grain refinement.

Mechanical Properties and Fracture Behaviors of the As-Extruded Mg-5Al-3Ca Alloys Containing Yttrium at Elevated Temperature.

Effects of yttrium (Y) addition on mechanical properties and fracture behaviors of the as-extruded Mg-Al-Ca based alloys at elevated temperature were investigated by a tensile test. After hot extrusion, the average grain size was refined by Y addition and eutectic phases were broken down into fine particles. Y addition to Mg-5Al-3Ca based alloy resulted in the improvement of strength and ductility at elevated temperature due to fine grain and suppression of grain growth by formation of thermally stable Al2Y intermetallic compound.

Microstructural Evolution of a Nanostructured Complex Copper Alloy Processed by Accumulative Roll-Bonding of Oxygen Free Copper and DLP.

The accumulative roll-bonding (ARB) process using different copper alloys of oxygen free copper (OFC) and dioxide low-phosphorous copper (DLPC) was performed up to six cycles at ambient temperature without lubrication. A complex copper alloy sheet'in which OFC and DLPC alloys are stacked alternately each other was successfully fabricated by the ARB process. The microstructural evolution and texture development of the complex copper alloy with proceeding of the ARB were investigated by electron back scatter diffraction (EBSD) measurement. The specimen after 1 cycle showed significantly inhomogeneous microstructure in thickness direction, however, the inhomogeneity decreased gradually with increasing the number of ARB cycles. In addition, the grains became finer with the proceeding of the ARB. Resultantly, after 6 cycles, the specimen exhibited an ultrafine grained structure in which the grains above 65% were surrounded by the high angle grain boundaries above 15 degrees. On the other hand, there was no difference in texture development between OFC and DLPC in almost all specimens. In addition, the texture development did not depend on positions in thickness direction; the rolling texture such as {112}<111> and {011}<211> components developed strongly at all regions.

A case of peritoneal dialysis-associated peritonitis by Rothia mucilaginosa.

Rothia muciliaginosa (R. mucilaginosa) is a facultative, Gram-positive coccus that is considered to be part of the normal flora of the mouth and respiratory tract. There are sporadic reports of the organism causing endocarditis in patients with heart valve abnormalities, as well as meningitis, septicemia, and pneumonia associated with intravenous drug abuse. However, it is an unusual pathogen in cases of peritoneal dialysis (PD)-associated peritonitis. Although R. mucilaginosa is generally susceptible to penicillin, ampicillin, cefotaxime, imipenem, rifampicin, and glycopeptides, there are no guidelines for the treatment of PD-associated peritonitis. Herein, we report a case of PD-associated peritonitis due to R. mucilaginosa that was resolved with intraperitoneal antibiotic treatment.

Microstructure and Mechanical Properties of Nanostructured 1050/6061 Aluminum Alloy Fabricated by Four-Layer Stack Accumulative Roll-Bonding.

An ultrafine grained AA1050/AA6061 Al alloy sheet was successfully fabricated by four-layer stack ARB process. The ARB of AA1050 and AA6061 alloy sheets was performed up to 3 cycles without a lubricant at ambient temperature. The sample fabricated by the ARB was a multi-layer aluminum alloy sheet in which AA1050 and AA6061 layers are alternately stacked. The layer thickness of the each alloy became thinner and elongated to the rolling direction with increasing the number of ARB cycles. The tensile strength increased with the ARB, it reached about 347 MPa which is almost 2.4 times that of the starting material. The grain size decreased with increasing of the number of ARB cycles, became about 190 nm in thickness after 3 cycles. The variation of mechanical properties with the ARB was similar to those of the other ARB processed materials. However, the texture development was different from those of the conventional ARB processed materials.

Fabrication of Nanostructure 1050/6061 Complex Al Alloy by Accumulative Roll-Bonding Process.

A nanostructure AA1050/AA6061 complex aluminum alloy was successfully fabricated by the accumulative roll-bonding (ARB) process. The ARB process was performed up to 5 cycles without a lubricant at ambient temperature. The samples fabricated by the ARB were the multi-layer complex aluminum alloys in which AA1050 and AA6061 layers are alternately stacked. The tensile strength of the samples increased with proceeding of the ARB, it reached about 300 MPa which is about twice that of the as-received AA6061. The grain size was greatly reduced to submicron order during the ARB, the efficiency of grain refinement was greater in AA6061 than AA1050. The tensile fracture surfaces showed a mixed morphology of brittle and ductile fracture. It was also found that a nanostructure multi-layer AA1050/AA6061 alloy fabricated by the ARB exhibited very complex microstructure and texture.