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Drought stress is a crucial environmental factor that limits plant growth, development, and productivity. Autophagy of misfolded proteins can help alleviate the damage caused in plants experiencing drought. However, the mechanism of autophagy‐mediated drought tolerance in plants remains largely unknown. Here, we cloned the gene for a maize (Zea mays) selective autophagy receptor, NEXT TO BRCA1 GENE 1 (ZmNBR1), and identified its role in the response to drought stress. We observed that drought stress increased the accumulation of autophagosomes. RNA sequencing and reverse transcription‐quantitative polymerase chain reaction showed that ZmNBR1 is markedly induced by drought stress. ZmNBR1 overexpression enhanced drought tolerance, while its knockdown reduced drought tolerance in maize. Our results established that ZmNBR1 mediates the increase in autophagosomes and autophagic activity under drought stress. ZmNBR1 also affects the expression of genes related to autophagy under drought stress. Moreover, we determined that BRASSINOSTEROID INSENSITIVE 1A (ZmBRI1a), a brassinosteroid receptor of the BRI1‐like family, interacts with ZmNBR1. Phenotype analysis showed that ZmBRI1a negatively regulates drought tolerance in maize, and genetic analysis indicated that ZmNBR1 acts upstream of ZmBRI1a in regulating drought tolerance. Furthermore, ZmNBR1 facilitates the autophagic degradation of ZmBRI1a under drought stress. Taken together, our results reveal that ZmNBR1 regulates the expression of autophagy‐related genes, thereby increasing autophagic activity and promoting the autophagic degradation of ZmBRI1a under drought stress, thus enhancing drought tolerance in maize. These findings provide new insights into the autophagy degradation of brassinosteroid signaling components by the autophagy receptor NBR1 under drought stress. [ABSTRACT FROM AUTHOR]

The heating process of the polymer composite reinforced by buckypaper was simulated with the finite element model. FLUENT was used to analyze how the thickness of buckypaper affect the temperature distribution, the changes of the temperature with time and the heating rate during heating. The maximum and average temperature of the composites decrease when the thickness of the buckypaper increase, whereas the minimum temperature on the samples have the opposite trend. The heating rate of the average temperature of the composites reinforced by the buckypaper with the thickness of 1.2 mm is faster than those of 0.4 mm and 0.8 mm. The temperature distribution of the polymer composites reinforced by the buckypaper is more uniform as the thickness of the buckypaper increase.

FLUENT was used to analyze how the bending cycles of buckypaper affects the temperature distribution, the changes of the temperature with time and the heating rate during heating. The typical temperature decreases with the increase of bending cycles of the buckypaper. The typical temperature increases with the increase of heating power. The temperature distribution of the polymer composites is more uniform with the increase of bending cycles of buckypaper. The difference of the maximum and minimum temperature of the composites increases linearly with the increase of heating power. The average temperature of the composites when reaching the stable state increase as the bending cycles of buckypaper decrease. The difference of the maximum and minimum temperature of the composites decreases with the increase of the bending cycles.

Summary: Mitogen‐activated protein kinase (MPK) is a critical regulator of the antioxidant defence system in response to various stimuli. However, how MPK directly and exactly regulates antioxidant enzyme activities is still unclear. Here, we demonstrated that a NAC transcription factor ZmNAC49 mediated the regulation of antioxidant enzyme activities by ZmMPK5.ZmNAC49 expression is induced by oxidative stress. ZmNAC49 enhances oxidative stress tolerance in maize, and it also reduces superoxide anion generation and increases superoxide dismutase (SOD) activity. A detailed study showed that ZmMPK5 directly interacts with and phosphorylates ZmNAC49 in vitro and in vivo. ZmMPK5 directly phosphorylates Thr‐26 in NAC subdomain A of ZmNAC49. Mutation at Thr‐26 of ZmNAC49 does not affect the interaction with ZmMPK5 and its subcellular localisation.Further analysis found that ZmNAC49 activates the ZmSOD3 expression by directly binding to its promoter. ZmMPK5‐mediated ZmNAC49 phosphorylation improves its ability to bind to the ZmSOD3 promoter. Thr‐26 of ZmNAC49 is essential for its transcriptional activity. In addition, ZmSOD3 enhances oxidative stress tolerance in maize.Our results show that phosphorylation of Thr‐26 in ZmNAC49 by ZmMPK5 increased its DNA‐binding activity to the ZmSOD3 promoter, enhanced SOD activity and thereby improved oxidative stress tolerance in maize. [ABSTRACT FROM AUTHOR]

Summary: Drought stress seriously limits crop productivity. Although studies have been carried out, it is still largely unknown how plants respond to drought stress. Here we find that drought treatment can enhance the phosphorylation activity of brassinosteroid‐signaling kinase 1 (ZmBSK1) in maize (Zea mays).Our genetic studies reveal that ZmBSK1 positively affects drought tolerance in maize plants. ZmBSK1 localizes in plasma membrane, interacts with calcium/calmodulin (Ca2+/CaM)‐dependent protein kinase (ZmCCaMK), and phosphorylates ZmCCaMK. Ser‐67 is a crucial phosphorylation site of ZmCCaMK by ZmBSK1.Drought stress enhances not only the interaction between ZmBSK1 and ZmCCaMK but also the phosphorylation of Ser‐67 in ZmCCaMK by ZmBSK1. Furthermore, Ser‐67 phosphorylation in ZmCCaMK regulates its Ca2+/CaM binding, autophosphorylation and transphosphorylation activity, and positively affects its function in drought tolerance in maize.Our results reveal an important role for ZmBSK1 in drought tolerance and suggest a direct regulatory mode of ZmBSK1 phosphorylating ZmCCaMK. [ABSTRACT FROM AUTHOR]

Salinity severely reduces plant growth and limits agricultural productivity. Dynamic changes and rearrangement of the plant cell wall is an important response to salt stress, but relatively little is known about the biological importance of specific cell wall components in the response. Here, we demonstrate a specific function of β-1,4-galactan in salt hypersensitivity. We found that salt stress induces the accumulation of β-1,4-galactan in root cell walls by up regulating the expression of GALACTAN SYNTHASE 1 (GALS1), which encodes a β-1,4-galactan synthase. The accumulation of β-1,4-galactan negatively affects salt tolerance. Exogenous application of D-galactose (D-Gal) causes an increase in β-1,4-galactan levels in the wild type and GALS1 mutants, especially in GALS1 overexpressors, which correlated with the aggravated salt hypersensitivity. Furthermore, we discovered that the BARLEY B RECOMBINANT/BASIC PENTACYSTEINE transcription factors BPC1/BPC2 positively regulate plant salt tolerance by repressing GALS1 expression and β-1,4-galactan accumulation. Genetic analysis suggested that GALS1 is genetically epistatic to BPC1/BPC2 with respect to the control of salt sensitivity as well as accumulation of β-1,4-galactan. Taken together, our results reveal a new regulatory mechanism by which β-1,4-galactan regulated by the BPC1/BPC2-GALS1 module aggravates salt sensitivity in Arabidopsis thaliana. Dynamic changes and rearrangement of the plant cell wall is an important response to salt stress, but relatively little is known about the underlying mechanisms. This study discovers a new regulatory mechanism by which cell wall β-1,4-galactan regulated by the BPC1/BPC2-GALS1 module aggravates salt sensitivity. [ABSTRACT FROM AUTHOR]

Drought stress severely limits the growth, development, and productivity of crops, and therefore understanding the mechanisms by which plants respond to drought is crucial. In this study, we cloned a maize NAC transcription factor, ZmNAC49 , and identified its function in response to drought stress. We found that ZmNAC49 is localized in the nucleus and has transcriptional activation activity. ZmNAC49 expression is rapidly and strongly induced by drought stress, and overexpression enhances stress tolerance in maize. Overexpression also significant decreases the transpiration rate, stomatal conductance, and stomatal density in maize. Detailed study showed that ZmNAC49 overexpression affects the expression of genes related to stomatal development, namely ZmTMM , ZmSDD1 , ZmMUTE , and ZmFAMA. In addition, we found that ZmNAC49 can directly bind to the promoter of ZmMUTE and suppress its expression. Taken together, our results show that the transcription factor ZmNAC49 represses ZmMUTE expression, reduces stomatal density, and thereby enhances drought tolerance in maize. [ABSTRACT FROM AUTHOR]

Plants have evolved various strategies to sense and respond to saline environments, which severely reduce plant growth and limit agricultural productivity. Alteration to the cell wall is one strategy that helps plants adapt to salt stress. However, the physiological mechanism of how the cell wall components respond to salt stress is not fully understood. Here, we show that expression of XTH30 , encoding xyloglucan endotransglucosylase-hydrolase30, is strongly up-regulated in response to salt stress in Arabidopsis. Loss-of-function of XTH30 leads to increased salt tolerance and overexpression of XTH30 results in salt hypersensitivity. XTH30 is located in the plasma membrane and is highly expressed in the root, flower, stem, and etiolated hypocotyl. The NaCl-induced increase in xyloglucan (XyG)-derived oligosaccharide (XLFG) of the wild type is partly blocked in xth30 mutants. Loss-of-function of XTH30 slows down the decrease of crystalline cellulose content and the depolymerization of microtubules caused by salt stress. Moreover, lower Na+ accumulation in shoot and lower H2O2 content are found in xth30 mutants in response to salt stress. Taken together, these results indicate that XTH30 modulates XyG side chains, altered abundance of XLFG, cellulose synthesis, and cortical microtubule stability, and negatively affecting salt tolerance. [ABSTRACT FROM AUTHOR]

Water deficit is a key limiting factor that affects the growth, development and productivity of crops. It is vital to understand the mechanisms by which plants respond to drought stress. Here an N -acetylglutamate kinase gene, ZmNAGK , was cloned from maize (Zea mays). ZmNAGK was expressed at high levels in maize leaves and at lower levels in root, stem, female flower and male flower. The expression of ZmNAGK was significantly induced by PEG, NaCl, ABA, brassinosteroid and H2O2. The ectopic expression of ZmNAGK in tobacco resulted in higher tolerance to drought compared to plants transformed with empty vector. Further physiological analysis revealed that overexpression of ZmNAGK could enhance the activities of antioxidant defense enzymes, and decrease malondialdehyde content and leakage of electrolyte in tobacco under drought stress. Moreover, the ZmNAGK transgenic tobacco accumulated more arginine and nitric oxide (NO) than control plants under drought stress. In addition, the ZmNAGK transgenic tobaccos activated drought responses faster than vector-transformed plants. These results indicate that ZmNAGK can play a vital role in enhancing drought tolerance by likely affecting the arginine and NO accumulation, and ZmNAGK could be involved in different strategies in response to drought stress. [ABSTRACT FROM AUTHOR]

A heat transfer model of polymer composite reinforced by buckypaper was established in this study to analyze how the shapes, heating power and thermal conductivity of polymer matrix affect the temperature distribution and heating uniformity. Thermal responses of the polymer composites reinforced by flat and pulse bending buckypaper were systematically studied, and the heating mechanisms of multiple-field coupling were investigated. The shapes and dimensions of the buckypaper are crucial in the optimization of such the polymer composites for heat generation. Results showed that the polymer composites reinforced by the flat buckypaper had relatively higher maximum and average temperatures in a steady heated state compared with those by the pulse bending ones, whereas the minimum temperature of the composites reinforced by the flat buckypaper was relatively lower, so the temperature distribution in those flat ones was more non-uniform. The overall heating temperature of the polymer composites reinforced by both the flat and pulse bending buckypaper was increased linearly with the applied power. The larger the thermal conductivity of the polymer is, the lower the maximum and average temperatures are. [ABSTRACT FROM AUTHOR]

In maize ( Zea mays), the mitogen-activated protein kinase Zm MPK5 has been shown to be involved in abscisic acid ( ABA)-induced antioxidant defence and to enhance the tolerance of plants to drought, salt stress and oxidative stress. However, the underlying molecular mechanisms are poorly understood. Here, using Zm MPK5 as bait in yeast two-hybrid screening, a protein interacting with Zm MPK5 named Zm ABA2, which belongs to a member of the short-chain dehydrogenase/reductase family, was identified. Pull-down assay and bimolecular fluorescence complementation analysis and co-immunoprecipitation test confirmed that Zm MPK5 interacts with Zm ABA2 in vitro and in vivo. Phosphorylation of Ser173 in Zm ABA2 by Zm MPK5 was shown to increase the activity of Zm ABA2 and the protein stability. Various abiotic stimuli induced the expression of Zm ABA2 in leaves of maize plants. Pharmacological, biochemical and molecular biology and genetic analyses showed that both Zm MPK5 and Zm ABA2 coordinately regulate the content of ABA. Overexpression of Zm ABA2 in tobacco plants was found to elevate the content of ABA, regulate seed germination and root growth under drought and salt stress and enhance the tolerance of tobacco plants to drought and salt stress. These results suggest that Zm ABA2 is a direct target of Zm MPK5 and is involved in ABA biosynthesis and functions. [ABSTRACT FROM AUTHOR]

Purpose – This paper aims to present a phenomenological model to investigate the underlying mechanism and predict the bio-inspired performance under different thermo-temporal conditions. Design/methodology/approach – Flory-Rehner free-energy functions are applied to quantitatively identify the driving forces in the viscously bio-inspired response of a dynamic polymer network. Furthermore, the permeation transition equation is adopted to couple water gradient and water sorption/desorption into the free-energy function. Findings – The results show that the influence of potential energy on deformation can be related to a stretching ratio that uniquely determines water sorption/desorption, locomotion frequency and contractile stress. Finally, by means of combining the free-energy function and Arrhenius equation, a phenomenological thermo-temporal model is developed and verified by the experimental results. Research limitations/implications – This study focuses on exploring the theoretical mechanism and significantly enhances understanding of relevant experimental features reported previously. Originality/value – The outcome of this study will provide a powerful phenomenological and quantitative tool for study on shape memory effect in bio-inspired polymers. [ABSTRACT FROM AUTHOR]

The influence of the porosity on the static mechanical strength of the carbon fiber fabric reinforced epoxy composites laminates was investigated. The tensile, compressive, bending, and interlaminar strength test on the CFRP laminates with porosity of 0.33% and 1.50% were conducted and simulated by a finite element analysis model. The article proposes the failure criterion of the static mechanical strength of the fabric fiber reinforced composites based on the improved Hashin failure criterion that is suitable for the undirectional composite laminates. The basic composite strength parameters are used to evaluate the mechanical properties of CFRP laminates with different porosities. A finite element analysis model is established by using software ABAQUS™ combined with the sudden stiffness degradation model. The experiment results show that the tensile, compressive, bending, and interlaminar strength decrease with the increasing porosities. The tensile, compressive, bending, and interlaminar strength of the fabric carbon fiber reinforced epoxy composites laminates are simulated accurately by the finite element model. [ABSTRACT FROM AUTHOR]

In this study, the role of the rice (Oryza sativa L.) histidine kinase OsHK3 in abscisic acid (ABA)-induced antioxidant defense was investigated. Treatments with ABA, H2O2, and polyethylene glycol (PEG) induced the expression of OsHK3 in rice leaves, and H2O2 is required for ABA-induced increase in the expression of OsHK3 under water stress. Subcellular localization analysis showed that OsHK3 is located in the cytoplasm and the plasma membrane. The transient expression analysis and the transient RNA interference test in rice protoplasts showed that OsHK3 is required for ABA-induced upregulation in the expression of antioxidant enzymes genes and the activities of antioxidant enzymes. Further analysis showed that OsHK3 functions upstream of the calcium/ calmodulin-dependent protein kinase OsDMI3 and the mitogen- activated protein kinase OsMPK1 to regulate the activities of antioxidant enzymes in ABA signaling. Moreover, OsHK3 was also shown to regulate the expression of nicotinamide adenine dinucleotide phosphate oxidase genes, OsrbohB and OsrbohE, and the production of H2O2 in ABA signaling. Our data indicate that OsHK3 play an important role in the regulation of ABA-induced antioxidant defense and in the feedback regulation of H2O2 production in ABA signaling. [ABSTRACT FROM AUTHOR]

In rice, the Ca2+/calmodulin ( CaM)-dependent protein kinase ( CCaMK) OsDMI3 has been shown to be required for abscisic acid ( ABA)-induced antioxidant defence. However, it is not clear how OsDMI3 participates in this process in rice. In this study, the cross-talk between OsDMI3 and the major ABA-activated MAPK OsMPK1 in ABA-induced antioxidant defence was investigated. ABA treatment induced the expression of OsDMI3 and OsMPK1 and the activities of OsDMI3 and OsMPK1 in rice leaves. In the mutant of OsDMI3, the ABA-induced increases in the expression and the activity of OsMPK1 were substantially reduced. But in the mutant of OsMPK1, the ABA-induced increases in the expression and the activity of OsDMI3 were not affected. Pretreatments with MAPKK inhibitors also did not affect the ABA-induced activation of OsDMI3. Further, a transient expression analysis in combination with mutant analysis in rice protoplasts showed that OsMPK1 is required for OsDMI3-induced increases in the activities of antioxidant enzymes and the production of H2O2. Our data indicate that there exists a cross-talk between OsDMI3 and OsMPK1 in ABA signalling, in which OsDMI3 functions upstream of OsMPK1 to regulate the activities of antioxidant enzymes and the production of H2O2 in rice. [ABSTRACT FROM AUTHOR]

This paper investigated the effect of porosities, environmental factors and impact energies on the impact resistance properties of Carbon Fiber Reinforced Polymer/Plastic (CFRP) laminates. Impact tests on the CFRP laminates with three porosity levels were subjected to five energy levels from 3 J to 15 J at the room temperature. The damage area was assessed with combined effects of different impact energies and porosity levels. The damage area was evaluated by visual inspection and ultrasonic C-scan measurement. The thermal deply technique was used to evaluate the damage evolution behavior. Three-point bending tests were conducted on the non-impacted and impacted specimens that were exposed to the room temperature, the hygrothermal and the drying environments. The curves of the impact resistance of the tested laminates mutate at the impact energy of 9 J. The thermal deply technique reveals the failure mechanism of the impact damage mutation of the tested laminates when the impact energy exceeds the threshold 9 J. [ABSTRACT FROM AUTHOR]

Based on the failure criterion that is suitable for the undirectional composite laminates, the impact damage of fabric fiber reinforced composites is proposed to improve the fiber and matrix damage failure criterion. The impact damage of longitude fiber failure, latitude fiber failure, matrix crushing and delamination were considered for the fabric carbon fiber reinforced epoxy composites laminates. A finite element analysis model is established by using ABAQUS software combined with the sudden stiffness degradation model. Basic strength parameters of composites are used to evaluate the mechanical properties of CFRP laminates with different porosities. The impact damage area of the fabric carbon fiber reinforced epoxy composites laminates are simulated accurately. [ABSTRACT FROM AUTHOR]

Impact tests on CFRP laminates with three porosity levels were conducted at impact energy levels of 3, 6, 9, 12 and 15 J to study the influences of porosity and impact energy on the impact damage tolerance. The impact damage was evaluated by ultrasonic C-scan measurement, metallurgical microscope, thermal deply technique and visual inspections. The experimental results show that the porosity has detrimental effects on the dent depth and the damage area of composite laminates for the same impact energy. The dent depth increases rapidly with the increasing of impact energy, and a progressive increase of the impact area occurs after 9 J. The thermal deply test reveals the failure mechanism of impact damage mutation of CFRP laminates when the impact energy exceeds the threshold 9 J. The impact energy is consumed from the matrix cracks and delaminating to the fiber cracks after 9 J. [ABSTRACT FROM AUTHOR]

C2H2-type zinc finger proteins (ZFPs) are thought to play important roles in modulating the responses of plants to drought, salinity and oxidative stress. However, direct evidence is lacking for the involvement of these ZFPs in abscisic acid (ABA)-induced antioxidant defense in plants. In this study, the role of the rice ( Oryza sativa L. sub. japonica cv. Nipponbare) C2H2-type ZFP ZFP182 in ABA-induced antioxidant defense and the relationship between ZFP182 and two rice MAPKs, OsMPK1 and OsMPK5 in ABA signaling were investigated. ABA treatment induced the increases in the expression of ZFP182, OsMPK1 and OsMPK5, and the activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) in rice leaves. The transient gene expression analysis and the transient RNA interference (RNAi) analysis in protoplasts showed that ZFP182, OsMPK1 and OsMPK5 are involved in ABA-induced up-regulation in the activities of SOD and APX. Besides, OsMPK1 and OsMPK5 were shown to be required for the up-regulation in the expression of ZFP182 in ABA signaling, but ZFP182 did not mediate the ABA-induced up-regulation in the expression of OsMPK1 and OsMPK5. These results indicate that ZFP182 is required for ABA-induced antioxidant defense and the expression of ZFP182 is regulated by rice MAPKs in ABA signaling. [ABSTRACT FROM AUTHOR]