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This paper mainly introduces the anti-crack performance of the nuclear grade nickel-based alloy welding materials produced by Baowu Special Metallurgy Co., Ltd. The research materials include welding wires (ERNiCrFe-7A), covered electrodes (ENiCrFe-7) and welding strips (EQNiCrFe-7A) used in PWR nuclear power plants. Evaluation of the anti-crack performance of the deposited metal is mainly carried out from the following three aspects: In order to study the thermal crack (crystal cracks) sensitivity of Baowu nickel-based alloy welding materials, the adjustable constraint test method is used and the results are compared with those of imported commercial welding materials; Based on STF (strain-to-fracture test) experimental method, the sensitivity of ductility dip cracking (DDC) of Baowu and imported nickel-based alloy welding materials is studied by thermal simulation equipment; The stress corrosion cracking (SCC) performance evaluation of Baowu welding materials is carried out by stress corrosion crack propagation experiment in simulated PWR primary water and compared with imported materials respectively. According to the above research, the crystal crack resistance, DDC resistance and SCC resistance of Baowu nickel-based alloy welding materials have reached the level of international high-level commercial welding material, which will further provide experimental data support for the engineering applicability and performance reliability of domestic nickel-based welding materials.

Creep behavior is an important parameter of the material properties of cold-formed steel (CFS) at elevated temperatures and the corresponding investigation is still very limited. In this paper, an experimental study with the creep duration of 4 h was performed for 1.0 mm thick G550 CFS. Forty-one test conditions were selected. The results showed that the creep curves of G550 CFS were distinctly different from that of Q550 and Q690 hot-rolled high-strength steel at elevated temperatures. In addition, the G550 CFS coupon specimens which demonstrated tertiary creep during the experiments would experience creep rupture. For the fire safety of steel structures, a critical temperature of G550 CFS which represented the onset of tertiary creep was given. When the stress ratio was less than 0.7, the critical temperature was lower than the temperature corresponding to the high-temperature yield strength of G550 CFS. Furthermore, a steady-state creep rate expression of G550 CFS was proposed. When the primary creep stage of G550 CFS was insignificant, the proposed expression could be used to give the estimation of the high-temperature creep curves of G550 CFS. Finally, the transient-state test strain of G550 CFS at 500 °C was predicted and compared with previous experimental results. It was shown that the creep strain was an essential part of the total strain of G550 CFS under transient-state conditions, and also a key factor leading to the difference of strain results between the transient-state and steady-state tests.

Drought is one of the main environmental factors that limit plant development and growth. Accordingly, plants have evolved strategies to prevent water loss under drought stress, such as stomatal closure, maintenance of root water uptake, enhancement of stem water transport, and synthesis and deposition of cuticular wax. However, the molecular evidence of cuticular wax biosynthesis regulation in response to drought is limited in woody plants. Here, we identified an MYB transcription factor, Populus tomentosa Carr. MYB transcription factor (PtoMYB142), in response to drought stress from P. tomentosa. Over-expression of PtoMYB142 (PtoMYB142-OE) resulted in increased wax accumulation in poplar leaves, and significantly enhanced drought resistance. We found that the expression of wax biosynthesis genes CER4 and 3-ketoacyl CoA synthase (KCS) were markedly induced under drought stress, and significantly up-regulated in PtoMYB142-OE lines. Biochemical analysis confirmed that PtoMYB142 could directly bind to the promoter of CER4 and KCS6, and regulate their expression in P. tomentosa. Taken together, this study reveals that PtoMYB142 regulates cuticular wax biosynthesis to adapt to water-deficient conditions.

The regulation of cytokinin on secondary vascular development has been uncovered by modulating cytokinin content. However, it remains unclear how cytokinin enriched in developing secondary phloem regulates cambium activity in poplar. Here, we visualized the gradient distribution of cytokinin with a peak in the secondary phloem of poplar stem via immunohistochemical imaging, and determined the role of phloem-located cytokinin signaling during wood formation. We generated transgenic poplar harboring cytokinin oxidase/dehydrogenase (CKX)2, a gene encoding a cytokinin degrading enzyme, driven by the phloem-specific CLE41b promoter, indicating that the disruption of the cytokinin gradient pattern restricts the cambial activity. The RNA interference-based knockdown of the histidine kinase (HK) genes encoding cytokinin receptors specifically in secondary phloem significantly compromised the division activity of cambial cells, whereas the phloem-specific expression of a type-B response regulator (RR) transcription factor stimulated cambial proliferation, providing evidence for the noncell-autonomous regulation of local cytokinin signaling on the cambial activity. Moreover, the cambium-specific knockdown of HKs also led to restricted cambial activity, and the defects were aggravated by the reduced cytokinin accumulation. Our results showed that local cytokinin signaling in secondary phloem regulates cambial activity noncell-autonomously, and coordinately with its local signaling in cambium.

Hepatic injury is common in patients who suffer from severe burns plus delayed resuscitation (B + DR). Stimulator of interferon genes (STING) is primarily expressed in Kupffer cells (KCs). We demonstrated that B + DR caused hepatic injury and oxidative stress. Reactive oxygen species (ROS) damage mitochondrial membranes in hepatocytes, leading to the release of mitochondrial DNA (mtDNA) into the hepatocyte cytosol and the circulation. The damaged hepatocytes then activate the mtDNA/STING pathway in KCs and trigger KCs polarization towards pro-inflammatory phenotype. SS-31 is a strong antioxidant that specifically concentrates in the inner mitochondrial membrane. SS-31 prevented hepatic injury by neutralizing ROS, inhibiting the release of mtDNA, protecting hepatocyte mitochondria, suppressing the activation of the mtDNA/STING pathway and inhibiting KCs polarization into pro-inflammatory phenotype.

The SKU5 similar (SKS) genes encode a family of multi-copper-oxidase-like proteins with cupredoxin domains similar to those in laccase and ascorbate oxidase. Although SKS proteins are known to function in root growth and cotyledon vascular patterning in Arabidopsis, their role in plant reproductive processes is poorly understood. Here, we identified a seed mutant of maize (Zea mays), generated by ethyl methane sulfonate (EMS) mutagenesis, that we designated defective kernel-zk1 (dek-zk1). The mutant produced small, shriveled kernels with an aberrant basal endosperm transfer layer (BETL) and placento-chalazal (PC) layer and irregular starch granules. Map-based cloning revealed that Dek-zk1 encodes an SKU5 similar 13 (GenBank: ONM36900.1), so it was named ZmSKS13. ZmSKS13 comprises a paralogous pair with Zm00001d012524, but the transcript abundance of ZmSKS13 in developing kernels is 15 times higher than that of Zm00001d012524, resulting in dek-zk1 mutation conveying a distinct kernel phenotype. ZmSKS13 loss of function led to overaccumulation of reactive oxygen species (ROS) and severe DNA damage in the nucellus and BETL and PC layer cells, and exogenous antioxidants significantly alleviated the defects of the mutant kernels. Our results thus demonstrate that ZmSKS13 is a novel regulator that plays a crucial role in kernel development in maize through the modulation of ROS homeostasis.

An external-insulated cold-formed steel (CFS) wall is a potential configuration that overcomes the disadvantage of cavity insulation in the fire performance of such walls and can meet the sound and thermal insulation requirements for building structures by increasing the thickness of insulation material. This paper conducted eight mid-scale non-load-bearing fire experiments on external-insulated wall specimens. Four different fire conditions were tested, including ISO 834 fire, external fire, hydrocarbon fire and a typical realistic design fire. A quasi-steady heat transfer state was identified at the final stage of external fire exposure. The effect of substituting the cavity insulation with external insulation on the fire performance is discussed by comparison with the previous fire experiments on cavity-insulated CFS walls. The results show that external insulation is a more reasonable configuration than cavity insulation for improving the fire resistance of CFS walls. In addition, two types of stud buckling, which include the local buckling of the whole stud section and local buckling of stud hot flange and adjacent web, were identified for non-load-bearing walls in fire, and the corresponding cause and conditions were described. In addition, to achieve high efficiency in the thermal performance modeling of CFS walls in fire, a quick and simplified calculation method was developed to get the temperature profile of steel frame based on a one-dimensional finite difference method. Moreover, an unexposed surface temperature of 900 °C was recommended as the criterion to predict the falling-off of the fire-side face-layer gypsum plasterboards of CFS walls in the heat transfer modeling.

Genetically modified (GM) crops possess some superior characteristics, such as high yield and insect resistance, but their biosafety has aroused broad public concern. Some genetic engineering technologies have recently been proposed to remove exogenous genes from GM crops. Few approaches have been applied to maintain advantageous traits, but excising exogenous genes in seeds or fruits from these hybrid crops has led to the generation of harvested food without exogenous genes. In a previous study, split-Cre mediated by split intein could recombine its structure and restore recombination activity in hybrid plants. In the current study, the recombination efficiency of split-Cre under the control of ovule-specific or pollen-specific promoters was validated by hybridization of transgenic Arabidopsis containing the improved expression vectors. In these vectors, all exogenous genes were flanked by two loxP sites, including promoters, resistance genes, reporter genes, and split-Cre genes linked to the reporter genes via LP4/2A. A gene deletion system was designed in which NCre was driven by proDD45, and CCre was driven by proACA9 and proDLL. Transgenic lines containing NCre were used as paternal lines to hybridize with transgenic lines containing CCre. Because this hybridization method results in no co-expression of the NCre and CCre genes controlled by reproduction-specific promoters in the F1 progeny, the desirable characteristics could be retained. After self-crossing in F1 progeny, the expression level and protein activity of reporter genes were detected, and confirmed that recombination of split-Cre had occurred and the exogenous genes were partially deleted. The gene deletion efficiency represented by the quantitative measurements of GUS enzyme activity was over 59%, with the highest efficiency of 73% among variable hybrid combinations. Thus, in the present study a novel dual reproductive cell-specific promoter-mediated gene deletion system was developed that has the potential to take advantage of the merits of GM crops while alleviating biosafety concerns.

For woody plants, clonal propagation efficiency is largely determined by adventitious root (AR) formation at the bases of stem cuttings. However, our understanding of the molecular mechanisms contributing to AR morphogenesis in trees remains limited, despite the importance of vegetative propagation, currently the most common practice for tree breeding and commercialization. Here, we identified Populus-specific miR476a as a regulator of wound-induced adventitious rooting that acts by orchestrating mitochondrial homeostasis. MiR476a exhibited inducible expression during AR formation and directly targeted several Restorer of Fertility like (RFL) genes encoding mitochondrion-localized pentatricopeptide repeat proteins. Genetic modification of miR476a-RFL expression revealed that miR476a/RFL-mediated dynamic regulation of mitochondrial homeostasis influences AR formation in poplar. Mitochondrial perturbation via exogenous application of a chemical inhibitor indicated that miR476a/RFL-directed AR formation depends on mitochondrial regulation that acts via auxin signaling. Our results thus establish a microRNA-directed mitochondrion-auxin signaling cascade required for AR development, providing insights into the role of mitochondrial regulation in the developmental plasticity of plants.

WRKY transcription factors (WRKY TFs) are one of the largest protein families in plants, and most of them play vital roles in response to biotic and abiotic stresses by regulating related signaling pathways. In this study, we isolated two WRKY TF genes PtrWRKY18 and PtrWRKY35 from Populustrichocarpa and overexpressed them in Arabidopsis. Expression pattern analyses showed that PtrWRKY18 and PtrWRKY35 respond to salicylic acid (SA), methyl JA (MeJA), abscisic acid (ABA), B. cinereal, and P. syringae treatment. The transgenic plants conferred higher B. cinerea tolerance than wild-type (WT) plants, and real-time quantitative (qRT)-PCR assays showed that PR3 and PDF1.2 had higher expression levels in transgenic plants, which was consistent with their tolerance to B. cinereal. The transgenic plants showed lower P. syringae tolerance than WT plants, and qRT-PCR analysis (PR1, PR2, and NPR1) also corresponded to this phenotype. Germination rate and root analysis showed that the transgenic plants are less sensitive to ABA, which leads to the reduced tolerance to osmotic stress and the increase of the death ratio and stomatal aperture. Compared with WT plants, a series of ABA-related genes (RD29A, ABO3, ABI4, ABI5, and DREB1A) were significantly down-regulated in PtrWRKY18 and PtrWRKY35 overexpression plants. All of these results demonstrated that the two WRKY TFs are multifunctional transcription factors in plant resistance.

Background As the main form of photoassimilates transported from vegetative tissues to the reproductive organs, sucrose and its degradation products are crucial for cell fate determination and development of maize kernels. Despite the relevance of sucrose synthase SH1 (shrunken 1)-mediated release of hexoses for kernel development, the underlying physiological and molecular mechanisms are not yet well understood in maize (Zea mays). Results Here, we identified a new allelic mutant of SH1 generated by EMS mutagenesis, designated as sh1*. The mutation of SH1 caused more than 90% loss of sucrose synthase activity in sh1* endosperm, which resulted in a significant reduction in starch contents while a dramatic increase in soluble sugars. As a result, an extremely high osmolality in endosperm cells of sh1* was generated, which caused kernel swelling and affected the seed development. Quantitative measurement of phosphorylated sugars showed that Glc-1-P in endosperm of sh1* (17 μg g− 1 FW) was only 5.2% of that of wild-type (326 μg g− 1 FW). As a direct source of starch synthesis, the decrease of Glc-1-P may cause a significant reduction in carbohydrates that flow to starch synthesis, ultimately contributing to the defects in starch granule development and reduction of starch content. Conclusions Our results demonstrated that SH1-mediated sucrose degradation is critical for maize kernel development and starch synthesis by regulating the flow of carbohydrates and maintaining the balance of osmotic potential.

RsgA plays an important role in maturation of 30S subunit in many bacteria that assists in the release of RbfA from the 30S subunit during a late stage of ribosome biosynthesis. Here, we genetically characterized functional roles of RsgA in

Additional file 1: Table S1. The list of molecular markers and primers used in gene cloning.

Additional file 4: Fig. S2. Full size, unedited gel used for Fig. 5c in the main text.

Additional file 2: Table S2. The list of primers used in qRT-PCR reaction.

Additional file 3: Fig. S1. The sequencing data of GRMZM2G089713 in Z58 and sh1*.

Type IV pili (T4P) are virulence factors in various pathogenic bacteria of animals and plants that play important roles in twitching motility, swimming motility, biofilm formation, and adhesion to host cells. Here, we genetically characterized functional roles of a putative T4P assembly protein TapV (Rsc1986 in reference strain GMI1000) and its homologue Rsp0189, which shares 58% amino acid identity with TapV, in Ralstonia solanacearum. Deletion of tapV, but not rsp0189, resulted in significantly impaired twitching motility, swimming motility, and adhesion to tomato roots, which are consistent as phenotypes of the pilA mutant (a known R. solanacearum T4P‐deficient mutant). However, unlike the pilA mutant, the tapV mutant produced more biofilm than the wild‐type strain. Our gene expression studies revealed that TapV, but not Rsp0189, is important for expression of a type III secretion system (T3SS, a pathogenicity determinant of R. solanacearum) both in vitro and in planta, but it is T4P independent. We further revealed that TapV affected the T3SS expression via the PhcA–TapV–PrhG–HrpB pathway, consistent with previous reports that PhcA positively regulates expression of pilA and prhG. Moreover, deletion of tapV, but not rsp0189, significantly impaired the ability to migrate into and colonize xylem vessels of host plants, but there was no alteration in intercellular proliferation of R. solanacearum in tobacco leaves, which is similar to the pilA mutant. The tapV mutant showed significantly impaired virulence in host plants. This is the first report on the impact of T4P components on the T3SS, providing novel insights into our understanding of various biological functions of T4P and the complex regulatory pathway of T3SS in R. solanacearum., A novel type 4 pili (T4P) assembly protein (TapV) was identified to contribute to full virulence of Ralstonia solanacearum, which affects the T3SS expression via the PhcA–TapV–PrhG–HrpB pathway but is T4P independent.

Introduction Liver injury induced by burn plus delayed resuscitation (B + DR) is life threatening in clinical settings. Mitochondrial damage and oxidative stress may account for the liver injury. MitoQ is a mitochondria-targeted antioxidant. We aimed to evaluate whether MitoQ protects against B + DR-induced liver injury. Methods Rats were randomly divided into three groups: (1) the sham group; (2) the B + DR group, which was characterized by third-degree burn of 30% of the total body surface area plus delayed resuscitation, and (3) the treatment group, in which rats from the B + DR model received the target treatment. MitoQ was injected intraperitoneally (i.p) at 15 min before resuscitation and shortly after resuscitation. In the vitro experiments, Kupffer cells (KCs) were subjected to hypoxia/reoxygenation (H/R) injury to simulate the B + DR model. Mitochondrial characteristics, oxidative stress, liver function, KCs apoptosis and activation of the NLRP3 inflammasome in KCs were measured. Results B + DR caused liver injury and oxidative stress. Excessive ROS lead to liver injury by damaging mitochondrial integrity and activating the mitochondrial DNA (mtDNA)-NLRP3 axis in KCs. The oxidized mtDNA, which was released into the cytosol during KCs apoptosis, directly bound and activated the NLRP3 inflammasome. MitoQ protected against liver injury by scavenging intracellular and mitochondrial ROS, preserving mitochondrial integrity and function, reducing KCs apoptosis, inhibiting the release of mtDNA, and suppressing the mtDNA-NLRP3 axis in KCs. Conclusion MitoQ protected against B + DR-induced liver injury by suppressing the mtDNA-NLRP3 axis.

Salt-induced developmental plasticity in a plant root system strongly depends on auxin signaling. However, the molecular events underlying this process are poorly understood. MicroRNA390 (miR390), trans-actin small interfering RNAs (tasiRNAs), and AUXIN RESPONSE FACTORs (ARFs) form a regulatory module involved in controlling lateral root (LR) growth. Here, we found that miR390 expression was strongly induced by exposure to salt during LR formation in poplar (Populus spp.) plants. miR390 overexpression stimulated LR development and increased salt tolerance, whereas miR390 knockdown caused by a short tandem target mimic repressed LR growth and compromised salt resistance. ARF3.1, ARF3.2, and ARF4 expression was inhibited significantly by the presence of salt, and transcript abundance was decreased dramatically in the miR390-overexpressing line but increased in the miR390-knockdown line. Constitutive expression of ARF4m harboring mutated trans-acting small interfering ARF-binding sites removed the salt resistance of the miR390 overexpressors. miR390 positively regulated auxin signaling in LRs subjected to salt, but ARF4 inhibited auxin signaling. Salinity stabilized the poplar Aux/IAA repressor INDOLE-3-ACETIC ACID17.1, and overexpression of an auxin/salt-resistant form of this repressor suppressed LR growth in miR390-overexpressing and ARF4-RNA interfering lines in the presence of salt. Thus, the miR390/TAS3/ARFs module is a key regulator, via modulating the auxin pathway, of LR growth in poplar subjected to salt stress.

Wood formation is a complex developmental process under multi-level transcriptional control executed by a large set of transcription factors. However, only limited members have been characterized to be key regulators of lignin biosynthesis in poplar. Here we report the conserved and unique functions of PtoMYB170, a transcription factor identified from Populus tomentosa (Chinese white poplar), in lignin deposition and drought tolerance in comparison with its duplicate paralog PtoMYB216. PtoMYB170 is preferentially expressed in young leaves and xylem tissues. Overexpression of PtoMYB170 in transgenic poplar plants resulted in stronger lignification and more thickened secondary wall in xylem compared with wild-type plants, whereas the CRISPR/Cas9-generated mutation of PtoMYB170 weakened lignin deposition, thereby leading to a more flexible and collapsed xylem phenotype. Transient expression experiments demonstrated that PtoMYB170 specifically activated the expression of lignin biosynthetic genes, consistent with the function of PtoMYB216. However, GUS staining assays revealed that PtoMYB170 was specifically expressed in guard cells of transgenic Arabidopsis while PtoMYB216 was not. Heterologous expression of PtoMYB170 in Arabidopsis enhanced stomatal closure in the dark and resulted in drought tolerance of the transgenic plants through reduced water loss, indicating a diversified role from PtoMYB216. These results revealed the PtoMYB170-dependent positive transcriptional regulation on lignin deposition in poplar and its coordinated function in enhancing drought tolerance by promoting dark-induced stomatal closure.

Wood development is strictly regulated by various phytohormones and auxin plays a central regulatory role in this process. However, how the auxin signaling is transducted in developing secondary xylem during wood formation in tree species remains unclear. Here, we identified an Aux/INDOLE-3-ACETIC ACID 9 (IAA9)-AUXIN RESPONSE FACTOR 5 (ARF5) module in Populus tomentosa as a key mediator of auxin signaling to control early developing xylem development. PtoIAA9, a canonical Aux/IAA gene, is predominantly expressed in vascular cambium and developing secondary xylem and induced by exogenous auxin. Overexpression of PtoIAA9m encoding a stabilized IAA9 protein significantly represses secondary xylem development in transgenic poplar. We further showed that PtoIAA9 interacts with PtoARF5 homologs via the C-terminal III/IV domains. The truncated PtoARF5.1 protein without the III/IV domains rescued defective phenotypes caused by PtoIAA9m. Expression analysis showed that the PtoIAA9-PtoARF5 module regulated the expression of genes associated with secondary vascular development in PtoIAA9m- and PtoARF5.1-overexpressing plants. Furthermore, PtoARF5.1 could bind to the promoters of two Class III homeodomain-leucine zipper (HD-ZIP III) genes, PtoHB7 and PtoHB8, to modulate secondary xylem formation. Taken together, our results suggest that the Aux/IAA9-ARF5 module is required for auxin signaling to regulate wood formation via orchestrating the expression of HD-ZIP III transcription factors in poplar.

Most previous fire experiments of cold-formed steel (CFS) walls were conducted under ISO834 fire exposure, for which the results can not reflect the fire performance in some special scenarios. Meanwhile, full-scale fire experiments of CFS walls are time-consuming and suffer from high equipment requirements and cost. In this paper, two 1.1 m×1.1 m mid-scale non-load-bearing fire experiments and three 3 m×3 m full-scale load-bearing fire experiments of CFS walls were carried out. The specimens used gypsum plaster (GP) board and calcium-silicate (CS) board as the sheathing boards, and rock wool as the cavity insulation. In addition, the experiments involved four different fire exposures. The results show that the time-temperature profiles between the mid-scale and full-scale specimens, which had the identical dimensions and configuration of wall cross-section, tend to be consistent under the same fire condition. Therefore, a simplified experimental method was proposed to determine the fire resistance time for the structural failure of CFS walls with different load ratios through only one non-load-bearing fire experiment of mid-scale specimen, which avoided the current complex implementation that the fire resistance time of CFS walls with different load ratios was determined by carrying out multiple full-scale load-bearing fire experiments. In addition, the horizontal board joints were identified as the weak parts for the fire resistance of CFS walls under different fire exposures, which would cause stud buckling near the horizontal joints during the fire experiments. Moreover, the experiments under different fire exposures shows extended fire resistance time by substituting GP board with CS board as the base-layer sheathing, and the critical temperatures of stud hot flanges, which corresponded to the structural failure of present cavity-insulated GP-CS sheathed CFS walls and the load ratio of 0.27, were close to each other with the average of 693.8 °C. Finally, it was verified that the equal area method can give a rational prediction of the fire resistance time equivalency after correction by reference temperatures.

An optimization process for impellers was carried out based on numerical simulation, Latin hypercube sampling (LHS), surrogate model and Genetic algorithm (GA) to improve the efficiency of residual heat removal pump. The commercial software ANSYS CFX 14.5 was utilized to solve the Reynolds-averaged Navier-Stokes equations by using the Shear stress transport turbulence model. The impeller blade parameters, which contain the blade inlet incidence angle Δβ, blade wrap angle φ, and blade outlet angle β 2, were designed by random sample points according to the LHS method. The efficiency predicted under the design flow rate was selected as the objective function. The best combination of parameters was obtained by calculating the surrogate model with the GA. Meanwhile, the prediction accuracies of three surrogate models, namely, Response surface model (RSM), Kriging model, and Radial basis neural network (RBNN), were compared. Results showed that the calculated findings agree with the experimental performance results of the original pump. The RSF model predicted the highest efficiency, while the RBNN had the highest prediction accuracy. Compared with the simulated efficiency of the original pump, the optimization increased efficiency by 8.34% under the design point. Finally, the internal flow fields were analyzed to understand the mechanism of efficiency improvement. The optimization process, including the comparison of the surrogate models, can provide reference for the optimization design of other pumps.

LATERAL ORGAN BOUNDARIES DOMAIN (LBD) proteins defined by a conserved LATERAL ORGAN BOUNDARIES (LOB) domain are key regulators of plant organ development. Recent studies have expanded their functional diversity beyond the definition of lateral organ boundaries to pollen development, plant regeneration, photomorphogenesis, pathogen response, and specific developmental functions in non-model plants, such as poplar and legumes. The identification of a range of upstream regulators, protein partners, and downstream targets of LBD family members has unraveled the molecular networks of LBD-dependent processes. Moreover, it has been demonstrated that LBD proteins have essential roles in integrating developmental changes in response to phytohormone signaling or environmental cues. As we discuss here, these novel discoveries of LBD functions and their molecular contexts promote a better understanding of this plant-specific transcription factor family.

Steel structures usually experience heating and cooling stages during a compartment fire. Most previous investigations on the high-temperature material properties of cold-formed steel (CFS) focused on the heating stage of steel, corresponding to the growth and fully developed phases of a compartment fire. The influence of the cooling stage of steel, which corresponds to the decay phase of a compartment fire, has not been properly considered. This study conducted 88 steady-state tests on G550 CFS at elevated temperatures and investigated the material properties during the heating and cooling stages. The results show that the prediction of the time-dependent load-bearing capacity of CFS structures under compartment fires might become non-conservative if the material properties of the G550 CFS during the cooling stage are replaced with those during the heating stage. For instance, when the tensile temperature is less than 500 °C and the peak temperature is greater than or equal to 600 °C, the yield strength reduction factors of G550 CFS during the cooling stage are significantly lower than those during the heating stage under the same tensile temperature. In addition, the distribution of the yield strength (ultimate strength) reduction factors of G550 CFS during the cooling stage is affected by the peak and tensile temperatures and displays two branches. The difference in the reduction factors between the two branches is significant under the same tensile temperature and different peak temperatures. Finally, unified equations for the material property reduction factors and stress–strain curves are proposed and can provide a reasonable prediction of the material properties of G550 CFS under full-range compartment fires.

Pentatricopeptide repeat (PPR) proteins, which are characterized by tandem 30–40 amino acid sequence motifs, constitute of a large gene family in plants. Some PPR proteins have been identified to play important roles in organellar RNA metabolism and organ development in Arabidopsis and rice. However, functions of PPR genes in woody species remain largely unknown. Here, we identified and characterized a total of 626 PPR genes containing PPR motifs in the Populus trichocarpa genome. A comprehensive genome-wide analysis of the poplar PPR gene family was performed, including chromosomal location, phylogenetic relationships and gene duplication. Genome-wide transcriptomic analysis showed that 154 of the PtrPPR genes were induced by biotic and abiotic treatments, including Marssonina brunnea, salicylic acid (SA), methyl jasmonate (MeJA), mechanical wounding, cold and salinity stress. Quantitative RT-PCR analysis further investigated the expression profiles of 11 PtrPPR genes under different stresses. Our results contribute to a comprehensive understanding the roles of PPR proteins and provided an insight for improving the stress tolerance in poplar.

Salt-induced developmental plasticity in a plant root system strongly depends on auxin signaling. However, the molecular events underlying this process are poorly understood. MicroRNA390 (miR390), trans-actin small interfering RNAs (tasiRNAs), and AUXIN RESPONSE FACTORs (ARFs) form a regulatory module involved in controlling lateral root (LR) growth. Here, we found that miR390 expression was strongly induced by exposure to salt during LR formation in poplar (Populus spp.) plants. miR390 overexpression stimulated LR development and increased salt tolerance, whereas miR390 knockdown caused by a short tandem target mimic repressed LR growth and compromised salt resistance. ARF3.1, ARF3.2, and ARF4 expression was inhibited significantly by the presence of salt, and transcript abundance was decreased dramatically in the miR390-overexpressing line but increased in the miR390-knockdown line. Constitutive expression of ARF4m harboring mutated trans-acting small interfering ARF-binding sites removed the salt resistance of the miR390 overexpressors. miR390 positively regulated auxin signaling in LRs subjected to salt, but ARF4 inhibited auxin signaling. Salinity stabilized the poplar Aux/IAA repressor INDOLE-3-ACETIC ACID17.1, and overexpression of an auxin/salt-resistant form of this repressor suppressed LR growth in miR390-overexpressing and ARF4-RNA interfering lines in the presence of salt. Thus, the miR390/TAS3/ARFs module is a key regulator, via modulating the auxin pathway, of LR growth in poplar subjected to salt stress.

Phosphate (Pi) deficiency has become a significant challenge to worldwide agriculture due to the depletion of accessible rock phosphate that is the major source of cheap Pi fertilizers. Previous research has identified a number of diverse adaptive responses to Pi starvation in the roots of higher plants. In this study, we found that accelerated axile root elongation of Pi-deprived maize plants resulted from enhanced cell proliferation. Comparative phosphoproteome and proteome profiles of maize axile roots were conducted in four stages in response to Pi deficiency by multiplex staining of high-resolution two dimensional gel separated proteins. Pro-Q DPS stained gels revealed that 6% of phosphoprotein spots displayed changes in phosphorylation state following low-Pi treatment. These proteins were involved in a large number of metabolic and cellular pathways including carbon metabolism and signal transduction. Changes in protein abundance of a number of enzymes indicated that low-Pi induced a number of carbon flux modifications in metabolic processes including sucrose breakdown and other downstream sugar metabolic pathways. A few key metabolic enzymes, including sucrose synthase (EC 2.4.1.13) and malate dehydrogenase (EC 1.1.1.37), and several signaling components involved in protein kinase or phosphatase cascades, auxin signaling and 14-3-3 proteins displayed low-Pi responsive changes in phosphorylation state or protein abundance. A variety of key enzymes and signaling components identified as potential targets for phosphorylation provide novel clues for comprehensive understanding of Pi regulation in plants. Protein phosphorylation, coordinating with changes in protein abundance, is required for maize root metabolic regulation and developmental acclimation to Pi starvation.

Salinity and drought often affect plant growth and crop yields. Cloning and identification of salinity and drought stress inducible promoters is of great significance for their use in the genetic improvement of crop resistance. Previous studies showed that phosphatidylinositol synthase (PIS) is involved in plant salinity and drought stress responses but its promoter has not been characterized by far. In the study, the promoter (pZmPIS, 1834 bp upstream region of the translation initiation site) was isolated from maize genome. To functionally validate the promoter, eight 5´ deletion fragments of pZmPIS in different lengths were fused to GUS to produce pZmPIS::GUS constructs and transformed into tobacco, namely PZ1-PZ8. The transcription activity and expression pattern obviously changed when the promoter was truncated. Previous studies have demonstrated that NaCl and PEG treatments are usually used to simulate salinity and drought treatments. The results showed that PZ1-PZ7 can respond well upon NaCl and PEG treatments, while PZ8 not. PZ7 (467 bp) displayed the highest transcription activity in all tissues of transgenic tobacco amongst 5´ deleted promoter fragments, which corresponds to about 20% and 50% of CaMV35S under normal and NaCl or PEG treatment, respectively. This implied that PZ7 is the core region of pZmPIS which confers high-level gene expression and NaCl or PEG inducible nature. The 113 bp segment between PZ7 and PZ8 (-467 to -355 bp) was considered as the key sequence for ZmPIS responding to NaCl or PEG treatment. GUS transient assay in tobacco leaves showed that this segment was sufficient for the NaCl or PEG stress response. Bioinformatic analysis revealed that the 113 bp sequence may contain new elements that are crucial for ZmPIS response to NaCl or PEG stress. These results promote our understanding on transcriptional regulation mechanism of ZmPIS and the characterized PZ7 promoter fragment would be an ideal candidate for the overexpression of drought and salinity responsive gene to improve crop resistance.

Sweet sorghum is a C4 plant with high efficiency of photosynthesis and accumulation of photosynthetic products during growth stage. Until now, little is known about photosynthetic characteristics of sweet sorghum subjected to heavy metal contaminated soil. In this study, photosynthetic modification of sweet sorghum was measured in response to cadmium (Cd) under greenhouse conditions. The experiment was concentrated specifically on Keller (KE) and E-Tian (ET), two cultivars of sweet sorghum. The plants subjected to 100 mg/kg Cd in soil were compared with the control plants without Cd treatment. The results indicated that both cultivars of sweet sorghum display similar photosynthetic responses to Cd exposure. The high Cd concentration resulted in significant decline of photosynthesis net rate (Pn). Pn of ET declines more than Cd-treated KE plants. Moreover, Cd-treated plants were detected to have lower stomata conductance (gs) and intercellular CO2 concentrations (Ci) than control plants. Chlorophyll content also displayed significant differences between control and Cd-treated plants. In ET, the reduction of both chlorophyll-a and chlorophyll-b was observed under Cd stress, compared with the controls. In contrast, chlorophyll content was significantly enhanced by Cd stress in KE. In conclusion, through the comparison between two sweet sorghum cultivars, it is demonstrated the photosynthetic activity of ET more sensitive to Cd stress than that of KE. Therefore, KE has a potential for biofuel production and phytoremediation of heavy metal in soil.

The ultrafine-grained (0.3–1.3 μm) AZ91 alloys, which were fabricated by powder extrusion in the range of 200 to 350 °C and subsequent aging at 100 °C for 8 h, exhibit a remarkable yield stress of 360–478 MPa and moderate tensile elongations of 6–8%. A composite structure was developed after extrusion with uniform β (Mg 17 Al 12 ) particles dispersed in magnesium matrix. The extrusion temperature has an indirect role on yield stress since partial dissolution of β particles induced by high extrusion temperature fails to retard grain growth. Moreover, the strength was further enhanced by the formation of nano-scale precipitates during artificial aging. The high strength could be attributed to a combination effect of grain refinement, particle reinforcement and precipitation hardening.

Development of high yield maize germplasm with satisfying nutritional quality has been a major objective for maize breeders. Introgression lines from hybrids between Zea mays ssp. mexicana, a close wild relative of cultivated maize, and elite maize inbred line Ye515 were obtained. Ear-related traits of the lines showed wide range of variation compared to the maize parent. Kernel protein contents in the progeny lines ranged from 7.89% to 12.44%. Considerable variability of protein fractions and amino acid composition of mature endosperms was observed. Protein contents for some lines such as SD00362, SD00312 and SD00259 were significantly higher than that of Ye515, and Lys and some other essential amino acids were conspicuously improved. It was concluded that introgression from Z. mays ssp. mexicana into a maize background had great effects on protein content and composition, and that desirable inbred lines with enhanced protein contents and improved nutritional value were produced via alien introgression.

Low phosphorus (P) availability is a major limitation for plant growth. To better understand the molecular mechanism of P efficiency in maize, comparative proteome analyses were performed on the roots of the low-P-tolerant mutant 99038 and wild-type Qi-319 grown under P-sufficient (+P) or P-deficient (-P) conditions. Over 10% of proteins detected on two-dimensional electrophoresis (2-DE) gels showed expression that was altered twofold or more between the genotypes under +P or -P conditions. We identified 73 (+P) and 95 (-P) differentially expressed proteins in response to phosphate (Pi) starvation. These proteins were involved in a large number of cellular and metabolic processes, with an obvious functional skew toward carbon metabolism and regulation of cell proliferation. Further analysis of proteome data, physiological measurements and cell morphological observations showed that, compared to the wild-type, the low-P-tolerant mutant could accumulate and secrete more citrate under Pi starvation, which facilitates solubilization of soil Pi and enhances Pi absorption. The proportion of sucrose in the total soluble sugars of the low-P-tolerant mutant was significantly higher, and cell proliferation in root meristem was accelerated. This resulted in better developed roots and more advantageous root morphology for Pi uptake. These results indicate that differences in citrate secretion, sugar metabolism and root-cell proliferation are the main reasons for higher tolerance to low-P conditions in the mutant compared to the wild-type. Thus, the mutant displayed specialized P-efficient root systems with a higher capacity for mobilization of external Pi and increased cell division in the root meristem under Pi starvation.

The S–N and Coffin–Manson plot, cyclic stress–strain response, changes of microstructure, and the surface morphology of ultra-fine grain (UFG) low-purity copper processed by ECAP were tested and observed in present study. And the formation mechanism of shear bands was discussed in detail. The results show that the UFG Cu represents longer lifetime under stress-controlled fatigue, but lower fatigue resistance under strain-controlled fatigue when compared with the coarse grain counterpart. Cyclic stress–strain responses of UFG Cu under stress-controlled fatigue alter from cyclic softening to cyclic hardening as stress amplitude decreases. But the responses always show cyclic softening under strain-controlled fatigue in present testing. By electron back scattering diffraction and transmission electron microscope technique, the shear bands were discovered on the surface of all cycled samples and no grain coarsening was discovered near the shear bands, which indicated that there was no inevitable relationship between formation of SBs and cyclic softening/grain coarsening. The discovery should be related to impurities in copper. The oriented distribution of defects along the shear plane in the last ECAP processing is one of the major mechanisms of SBs formation.