Cold stress is an important factor that limits apple production. In this study, we examined the tissue-cultured plantlets of apple rootstocks ‘M9T337’ and ‘60-160’, which are resistant and sensitive ...to cold stress, respectively. The enriched pathways of differentially expressed genes (DEGs) and physiological changes in ‘M9T337’ and ‘60-160’ plantlets were clearly different after cold stress (1°C) treatment for 48 h, suggesting that they have differential responses to cold stress. The differential expression of WRKY transcription factors in the two plantlets showed that MdWRKY40is and MdWRKY48 are potential regulators of cold tolerance. When we overexpressed MdWRKY40is and MdWRKY48 in apple calli, the overexpression of MdWRKY48 had no significant effect on the callus, while MdWRKY40is overexpression promoted anthocyanin accumulation, increased callus cold tolerance, and promoted the expression of anthocyanin structural gene MdDFR and cold-signaling core gene MdCBF2. Yeast one-hybrid screening and electrophoretic mobility shift assays showed that MdWRKY40is could only bind to the MdDFR promoter. Yeast two-hybrid screening and bimolecular fluorescence complementation showed that MdWRKY40is interacts with the CBF2 inhibitor MdMYB15L through the leucine zipper (LZ). When the LZ of MdWRMY40is was knocked out, MdWRKY40is overexpression in the callus did not affect MdCBF2 expression or callus cold tolerance, indicating that MdWRKY40is acts in the cold signaling pathway by interacting with MdMYB15L. In summary, MdWRKY40is can directly bind to the MdDFR promoter in order to promote anthocyanin accumulation, and it can also interact with MdMYB15L to interfere with its inhibitory effect on MdCBF2, indirectly promoting MdCBF2 expression, and thereby improving cold tolerance. These results provide a new perspective for the cold-resistance mechanism of apple rootstocks and a molecular basis for the screening of cold-resistant rootstocks.
We investigate, for two water models displaying a liquid-liquid critical point, the relation between changes in dynamic and ther-modynamic anomalies arising from the presence of the liquid-liquid ...critical point. We find a correlation between the dynamic crossover and the locus of specific heat maxima$C_{P}^{max}$("Widom line") emanating from the critical point. Our findings are consistent with a possible relation between the previously hypothesized liquid-liquid phase transition and the transition in the dynamics recently observed in neutron scattering experiments on confined water. More generally, we argue that this connection between$C_{P}^{max}$and dynamic crossover is not limited to the case of water, a hydrogen bond network-forming liquid, but is a more general feature of crossing the Widom line. Specifically, we also study the Jagla potential, a spherically symmetric two-scale potential known to possess a liquid-liquid critical point, in which the competition between two liquid structures is generated by repulsive and attractive ramp interactions.
The trace addition of rare earth (RE) elements in Mg alloys can modify the extrusion texture, leading to the formation of RE texture and thus improved formability. The interrupted extrusion ...experiment as well as electron back-scatter diffraction (EBSD) characterization was conducted in Mg-1.5Zn-0.5Gd (wt.%) alloy to unveil the dominant dynamic recrystallization (DRX) mechanism and its correlation with the formation of RE texture during extrusion. The results indicate that continuous DRX (CDRX) dominated the microstructural development. Fresh DRXed grains with 30° 0001 grain boundaries preferentially nucleated in unDRXed grains with 10Formula: see text0 basal fiber orientation via CDRX, showing preferred selection of 2Formula: see textFormula: see text0 basal fiber orientation rather than RE texture orientation. Consequently, CDRX contributed to the weakening of 10Formula: see text0 basal fiber texture and had a more significant effect on the formation of 2Formula: see textFormula: see text0 basal fiber component than that of RE texture component. Besides, the preferred growth of recrystallized grains with RE texture orientation was confirmed to occur during static annealing after extrusion, which is inferred as the key reason for the formation of RE texture in dilute Mg-RE alloys.
In this work, the influence of element Y on the mechanical properties of the as-cast Mg–5.5Zn–
xY–0.8Zr alloys (with element Y content of 0, 1.08, 1.97 and 3.08
wt.%) has been investigated and ...compared. The results showed that the alloy with Y content of 1.08
wt.% had the superior tensile strength, but its ductility was the lowest. When Y content reached 1.97 or 3.08
wt.%, the tensile strength of the alloys decreased obviously, but the ductility had a little improvement. X-ray phase analysis showed that when Y content was 1.08
wt.%, the alloy mainly contained I-phase and α-Mg matrix, whereas when Y content was 1.97 or 3.08
wt.%, besides I-phase and α-Mg matrix, W-phase would be formed. And the diffraction peak of W-phase intensified with the increase of element Y content. Based on fracture observations, the influence of I-phase and W-phase on the mechanical properties of the alloys has been explained, respectively. It revealed that I-phase was closely bonded with the Mg matrix and could effectively retard the basal slip, and then strengthened the alloy greatly. However, W-phase was easily cracked during the tensile process, which degraded the mechanical properties.
The corrosion and electrochemical behaviour of carefully prepared ultra-lightweight magnesium-lithium (Mg-Li) alloys were investigated and compared. The alloy compositions studied were selected to ...provide the ability to compare unique microstructures and crystal structures, which arise from specific alloying additions of Li. Mg-4%Li is hexagonal closed-packed (HCP) alloy with Li in solid solution of Mg (α-Mg); Mg-14%Li is a fully solid solution BCC (β-Li) alloy, whilst Mg-7.5%Li is a duplex (α-Mg + β-Li) alloy. Testing in 0.1 M NaCl revealed that the corrosion performance and electrochemical response of the Mg-Li system evolved with the composition and crystallographic structure. For Mg-4%Li alloy, filiform-like corrosion morphology can be observed on the corroded surface, whilst a mixture of filiform-like corrosion to the α-Mg and localised dissolution of β-Li existed on the corroded surface of Mg-7.5%Li alloy. In the case of the BCC structured Mg-14%Li alloy, minor pitting was observed, concomitant with a generally low corrosion rate (particularly low corrosion rate for typical Mg alloys) and an increasing corrosion resistance with exposure time were also revealed. A combination of exposure testing inclusive of hydrogen collection and mass loss, in addition to potentiodynamic polarisation and impedance spectroscopy elucidated and quantified the corrosion performance of three differently structured Mg-Li alloys. It revealed that in spite of being composed of reactive elements of Mg and Li, the formation of β-Li phases with BCC structure could facilitate the formation of a highly protective surface film which results in a predictable and consistently low corrosion rate of the Mg-14%Li alloy.
•Corrosion behaviour was dependent on the crystal structure of Mg-Li alloys.•Mg-4Li, Mg-7.5Li and Mg-14Li (wt.%) alloys were HCP, HCP + BCC and BCC structure, respectively.•Corrosion attack preferentially occurred in α-Mg phase of Mg-7.5Li alloy.•Mg-14Li alloy revealed a high corrosion resistance which increased with immersion time.•A highly protective surface film could form on Mg-14Li alloy with single β-Li phase.
This work mainly investigated the mechanical properties of as-cast Mg–Zn–Y–Zr Mg alloys with Zn/Y ratio about 0.97. Tensile results show that when Zn/Y ratio is constant, the alloy (with Zn and Y ...contents of 3.93 and 4.14
wt.%, respectively) has the highest strength. XRD analysis shows that the alloys are mainly composed of α-Mg matrix and W-phase. With the contents of Zn and Y increasing, the diffraction peaks of W-phase are gradually intensified. In addition, microstructure observation indicates that with the increase of Zn and Y contents, the grain boundaries are gradually coarsened by W-phase. Based on the microstructure observation and fracture analysis, the change of the mechanical properties has been explained.
Conservation of normal cognitive functions relies on the proper performance of the nervous system at the cellular and molecular level. The mammalian nicotinamide-adenine dinucleotide-dependent ...deacetylase SIRT1 impacts different processes potentially involved in the maintenance of brain integrity, such as chromatin remodeling, DNA repair, cell survival, and neurogenesis. Here we show that SIRT1 is expressed in neurons of the hippocampus, a key structure in learning and memory. Using a combination of behavioral and electrophysiological paradigms, we analyzed the effects of SIRT1 deficiency and overexpression on mouse learning and memory as well as on synaptic plasticity. We demonstrated that the absence of SIRT1 impaired cognitive abilities, including immediate memory, classical conditioning, and spatial learning. In addition, we found that the cognitive deficits in SIRT1 knock-out (KO) mice were associated with defects in synaptic plasticity without alterations in basal synaptic transmission or NMDA receptor function. Brains of SIRT1-KO mice exhibited normal morphology and dendritic spine structure but displayed a decrease in dendritic branching, branch length, and complexity of neuronal dendritic arbors. Also, a decrease in extracellular signal-regulated kinase 1/2 phosphorylation and altered expression of hippocampal genes involved in synaptic function, lipid metabolism, and myelination were detected in SIRT1-KO mice. In contrast, mice with high levels of SIRT1 expression in brain exhibited regular synaptic plasticity and memory. We conclude that SIRT1 is indispensable for normal learning, memory, and synaptic plasticity in mice.
•I-phase improves the strength of Mg–Li alloys.•I-phase particles suppress the plastic flow of β phases at and below 220°C.•More I-phase particles can further increase the strength.
Through ...investigating tensile properties of the duplex Mg–Li alloys with and without I-phase (Mg3Zn6Y, icosahedral quasicrystal structure) tested both at ambient and elevated temperatures, it demonstrates that I-phase can not only improve the tensile strength at room temperature, but also be beneficial for the mechanical improvement at elevated temperatures. Based on the microstructural observations of the sample surfaces before and after tests, the I-phase particles can effectively suppress the plastic flow of β phase at 220°C, resulting in the I-phase reinforced duplex Mg–Li alloy having higher mechanical properties at elevated temperatures.
Wnt/β‐catenin signalling is initiated by a ternary Wnt‐Frizzled (FZD)‐LDL receptor‐related protein (LRP) 5/6 binding event. The resulting conformational changes in the FZD and LRP5/6 receptors ...promote the assembly of an intracellular signalosome driven by Dishevelled and Axin co‐polymerization. Recent evidence suggests that the FZD receptor and LRP5/6 participate in the assembly of this signalosome by forming regulatory scaffolds for stabilizing Dishevelled and Axin adapters. In this review, we focus on the contributions of Wnts and their receptors in the assembly of the signalosome. We present an emerging model, which unifies Wnt receptor oligomerization with intracellular signalosome formation, and then discuss how FZD receptors might be targeted to either disrupt or enhance their capacity as a dynamic sensor of Wnt binding.
Linked Articles
This article is part of a themed section on WNT Signalling: Mechanisms and Therapeutic Opportunities. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.24/issuetoc
PDF
