Search

Defense elicitors can induce fruit disease resistance to control postharvest decay but may incur quality impairment. Our present work aimed to investigate the resistance against Botrytis cinerea induced by the elicitor β-aminobutyric acid (BABA) and to elucidate the specific transcriptional mechanism implicated in defense-related metabolic regulations. The functional dissection results demonstrated that, after inoculation with the fungal necrotroph B. cinerea, a suite of critical genes encoding enzymes related to the sucrose metabolism and phenylpropanoid pathway in priming defense in grapes were transcriptionally induced by treatment with 10 mM BABA. In contrast, more UDP-glucose, a shared precursor of phenylpropanoid and sucrose metabolism, may be redirected to the phenylpropanoid pathway for the synthesis of phytoalexins, including trans-resveratrol and ɛ-viniferin, in 100 mM BABA–treated grapes, resulting in direct resistance but compromised soluble sugar contents. An R2R3-type MYB protein from Vitis vinifera, VvMYB44, was isolated and characterized. VvMYB44 expression was significantly induced upon the grapes expressed defensive reaction. Subcellular localization, yeast two-hybrid, and coimmunoprecipitation assays revealed that the nuclear-localized VvMYB44 physically interacted with the salicylic acid–responsive transcription coactivator NPR1 in vivo for defense expression. In addition, VvMYB44 directly bound to the promoter regions of sucrose and phenylpropanoid metabolism-related genes and transactivated their expression, thus tipping the balance of antifungal compound accumulation and soluble sugar maintenance. Hence, these results suggest that 2R-type VvMYB44 might be a potential positive participant in BABA-induced priming defense in grape berries that contributes to avoiding the excessive consumption of soluble sugars during the postharvest storage. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

The priming of defence responses in pathogen‐challenged model plants undergoes a preparation phase and an expression phase for defence function. However, the priming response in postharvest fruits has not been elucidated. Here, we found that 50 mM β‐aminobutyric acid (BABA) treatment could induce two distinct pathways linked with TGA1‐related systemic acquired resistance (SAR), resulting in the alleviation of Rhizopus rot in postharvest peach fruit. The first priming phase was elicited by BABA alone, leading to the enhanced transcription of redox‐regulated genes and posttranslational modification of PpTGA1. The second phase was activated by an H2O2 burst via up‐regulation of PpRBOH genes and stimulation of the MAPK cascade on pathogen invasion, resulting in a robust defence. In the MAPK cascade, PpMAPKK5 was identified as a shortcut interacting protein of PpTGA1 and increased the DNA binding activity of PpTGA1 for the activation of salicylic acid (SA)‐responsive PR genes. The overexpression of PpMAPKK5 in Arabidopsis caused the constitutive transcription of SA‐dependent PR genes and as a result conferred resistance against the fungus Rhizopus stolonifer. Hence, we suggest that the BABA‐induced priming defence in peaches is activated by redox homeostasis with an elicitor‐induced reductive signalling and a pathogen‐stimulated H2O2 burst, which is accompanied by the possible phosphorylation of PpTGA1 by PpMAPKK5 for signal amplification., BABA elicitation regulates the redox homeostasis and shortcut interaction of TGA1 and MAPKK5 for a SAR‐related priming defence in postharvest peaches.

Either NPR1 or TGA1 serve as master redox-sensitive transcriptional regulators for the transcription of PR genes in plants. The redox modification of the two co-activators involved in BABA-induced priming resistance against Botrytis cinerea in grapes was examined in this study. The results showed that 10 mmol L−1 BABA could effectively trigger a priming defense in grapes as manifested by augmented expression levels of PR genes upon inoculation with B. cinerea. Moreover, transcriptome profiling analysis revealed that all of the sets of key genes in the enzymatic ROS scavenging system, the PPP and AsA-GSH cycle were in harmony and were transcriptionally induced in BABA-primed grapes with pathogenic infection; in addition, this enhanced expression caused the accelerated accumulation of reductive substances, namely, AsA, GSH and NADPH, resulting in reduced intercellular conditions. Under reduced conditions, the interaction of VvTGA1 and VvNPR1 in the Y2H assay implied that VvTGA1 can provide the DNA binding capacity required by VvNPR1 for activation of VvPR genes. Consequently, the transactivation of VvNPR1 by the promoters of VvPR1, VvPR2 and VvPR5 was determined via a DLR assay, and it induced the transcription of the VvPR genes. In parallel, the redox-modified reducing condition achieved with an abundant supply of reductive substances was closely associated with the translocation of NPR1 for interaction with TGA in the nucleus. Thus, the posttranslational modification and subsequent interaction of the two redox-sensitive co-activators of VvNPR1 and VvTGA1 under reduced conditions may be responsible for BABA-induced priming for effective disease resistance in grapes.

Slug rivet interference-fit riveting is an advanced connection technology. The quality of riveted aircraft structures can be evolved to a higher-level with good sealing performance when using slug rivet. Some research has been conducted to study the effects of riveting process on riveting quality. But, few attentions have been paid on the action mechanism of rivet die structure during riveting process. This paper reveals the internal relation between rivet die structure and riveting quality in the forms of theoretical and numerical analyses as well as experimental verification. Three typical concave rivet die structures and the corresponding combinations have been studied. The result indicates that well-designed rivet die can effectively improve riveting quality. The rivet die with isosceles trapezoid cross-section can generate a larger radial reactive force to prevent the radial flow of rivet metal material to form driven head. More axial material flow can be pushed into rivet hole to increase the interference value. The results considerably improve knowledge about the behavior of rivet die during riveting process. The aim is to find out the appropriate rivet die to improve riveting quality. The study will pave the way for high structural fatigue-resistant design in modern aerospace manufacture.

This paper presents a U-model-based adaptive sliding mode control (SMC) using a deep deterministic policy gradient (DDPG) for uncertain nonlinear systems. The configuration of the proposed methodology consisted of a U-model framework and an SMC with a variable boundary layer. The U-model framework forms the outer feedback loop that adjusts the overall performance of the nonlinear system, while SMC serves as a robust dynamic inverter that cancels the nonlinearity of the original plant. Besides, to alleviate the chattering problem while maintaining the intrinsic advantages of SMC, a DDPG network is designed to adaptively tune the boundary and switching gain. From the control perspective, this controller combines the interpretability of the U-model and the robustness of the SMC. From the deep reinforcement learning (DRL) point of view, the DDPG calculates nearly optimal parameters for SMC based on current states and maximizes its favourable features while minimizing the unfavourable ones. The simulation results of the single-pendulum system are compared with those of a U-model-based SMC optimized by the particle swarm optimization (PSO) algorithm. The comparison, as well as model visualization, demonstrates the superiority of the proposed methodology.

MADS-box genes play well-documented roles in plant development, but relatively little is known regarding their involvement in defence responses. In this study, pre-treatment of peach (Prunus persica) fruit with β-aminobutyric acid (BABA) activated resistance against Rhizopus stolonifer, leading to a significant delay in the symptomatic appearance of disease. This was associated with an integrated defence response that included a H2O2 burst, ABA accumulation, and callose deposition. cDNA library screening identified nucleus-localized MADS2 as an interacting partner with NPR1, and this was further confirmed by yeast two-hybrid, luciferase complementation imaging, and co-immunoprecipitation assays. The DNA-binding activity of NPR1 conferred by the NPR1–MADS2 complex was required for the transcription of SA-dependent pathogenesis-related (PR) and ABA-inducible CalS genes in order to gain the BABA-induced resistance, in which MAPK1-induced post-translational modification of MADS2 was also involved. In accordance with this, overexpression of PpMADS2 in Arabidopsis potentiated the transcription of a group of PR genes and conferred fungal resistance in the transgenic plants. Conversely, Arabidopsis mads2-knockout lines showed high sensitivity to the fungal pathogen. Our results indicate that MADS2 positively participates in BABA-elicited defence in peach through a combination of SA-dependent NPR1 activation and ABA signaling-induced callose accumulation, and that this defence is also related to the post-translational modification of MADS2 by MAPK1 for signal amplification.

Many previous studies have mainly focused on the effects of riveting parameters on single-row riveted lap joints. Little attention has been paid to multi-row riveted lap joints. The outer rows of a normal multi-row riveted lap joint usually bear a larger part of the tensile load. However, none of the studies relate the phenomenon to the squeezing displacement combination of a multi-row riveted lap joint. To improve the performance of a three-row riveted lap joint, this paper aims to reveal the internal relation between tensile load distribution, structural deformation and squeezing displacement combination. Theoretical discussion, numerical simulation and an experimental test have been conducted. Four different squeezing displacement combinations have been studied. The result indicates that an appropriate squeezing displacement combination can effectively make tensile load distribution more homogeneous. Each rivet can take approximately 33% tensile load. Structural deformation magnitude can be reduced as well. Compared with the worst situation, at the region most sensitive to tensile load, the max strain value can reduce about 53.22–79.76%. A suitable squeeze displacement combination is a simple approach for the performance enhancement of a three-row riveted lap joint. It can be practically applied in aircraft manufacturing without any additional equipment or skill learning.

The slug rivet installation process is complex. A lot of parameters are included during the riveting deformation process. The workload and time cost of a traditional simulation study is very high since a traditional numerical model should be modified manually time by time when riveting parameters change. The data processing after simulation is another complex work. To improve the situation, this paper presents a parameterized modeling method. The modeling process and data processing algorithm can be developed using Python script. The parameterized model can automatically and continuously re-build without any manual intervention according to the riveting parameter auto-update condition. The post-processing analysis can be automatically conducted and saved as well. Then this paper conducts continuous analysis to illustrate the impact of riveting parameters on riveting quality. The parameterized model keeps running 41 times until the riveting parameter is out of range. The parameterized modeling method is a useful method for a simulation study. The study will pave the way for further investigations.

Induction of phytoalexin production after invading pathogens is recognized as an essential aspect of the plant-induced resistance. The WRKY family includes plant-specific transcriptional factors associated with plant defense responses, but the comprehensive mechanisms are poorly understood. Here, we attempted to elaborate the regulatory function of VvWRKY18 from the group IIa of WRKY transcription factor (TF) from Vitis vinifera, in the regulation of β-aminobutyric acid (BABA)-activated stilbene phytoalexins biosynthesis and PATHOGENESIS-RELATED (PR) genes expressions in grapes. BABA at 10 mmol L-1 triggered a priming protection in grapes and conferred a potentiation of the expression levels of VvWRKY18, VvNPR1, and several salicylic acid (SA)-responsive genes, which was accompanied by enhanced stilbene production upon Botrytis cinerea infection. In addition, a physical interaction between VvWRKY18 and the regulatory protein VvNPR1 was detected in vivo and in vitro by yeast-2-hybrid (Y2H), pull-down and co-immunoprecipitation assay (Co-IP) assays. Furthermore, yeast-1-hybrid (Y1H) and dual-luciferase reporter (DLR) assays indicated that VvWRKY18 activated the transcription of STILBENE SYNTHASE (STS) genes, including VvSTS1 and VvSTS2, by directly binding the W-box elements within the specific promoters and resultantly enhancing stilbene phytoalexins biosynthesis. Further investigation demonstrated that heterologous expression of VvWRKY18 elevated the transcriptions of STS and PR genes, thus contributing to potentiating the defense of transgenic Arabidopsis thaliana plants and resultantly inhibiting B. cinerea invasion. Hence, VvWRKY18 serves as a singular effector involved in the synthesis of stilbene phytoalexins in grapes and its interaction with VvNPR1 provided DNA binding ability required for VvNPR1 to initiate systemic acquired resistance (SAR) defense.

Slug rivet interference-fit riveting is one of the advanced connection technologies. Many researches have been conducted to study the quality of slug rivet assembly. However, some previous theoretical studies have only focused on the riveted lap joints without countersunk hole structure. To make a more comprehensive understanding of the riveting quality, this paper first proposes an effective method to study the riveted assembly with countersunk hole structure. An effective and accurate theoretical model is built to reflect the mapping relationship between squeezing force and driven head dimension. Since the driven head dimension is the riveting quality control criterion, and the squeezing force is the most important riveting parameter. Simulations and experiments are conducted to verify the validity of the theoretical analysis. Comparison results prove the theoretical model’s ability to analyze the rivet deformation. Theoretical analysis can provide an effective compact analysis. The study will pave the way for further investigations.

Slug rivet interference-fit riveting is one of the advanced connection technologies, which has been widely applied in aerospace manufacture. In the fields of residual stress analysis, structural deformation analysis, load transfer mechanism analysis, and the assessment of the effects of process parameters on riveting quality, study accuracy needs increasingly accurate and comprehensive models. Since the simulation of riveting process is a particularly time-consuming case. The aim of this paper is to develop some appropriate FE models for the special applications with a compromise between model size, calculation time, and simulation precision. Different types of FE models have been established based on force-controlled approach and displacement-controlled approach. The comparison between different FE models is satisfactory in terms of riveting process and riveting quality control criterion. The study significantly deepens the comprehension of the slug rivet installation process. Subsequent research can select an appropriate model according to its special target. The study will pave the way for further investigations.

WRKY transcription factors (TFs) are essential for the regulation of disease resistance in plants, and ubiquitination is one of the major post-translational modification types for a suite of TFs, while limited information is available about the involvement of E3 ubiquitin ligase-mediated regulation of WRKY proteins in β-amino-butyric acid (BABA)-primed defense resistance in peach fruit. Here, we observed that the treatment of peach fruit with BABA elicited disease resistance against the necrotrophic fungus Rhizopus stolonifer, resulting in an obvious inhibition of Rhizopus rot, which was accompanied by accumulation of total phenolics and lignins and potentiated the activity of several defensive enzymes, including phenylalanine ammonia-lyase (PAL), chitinase (CHI) and β-1,3-glucanase (GNS). Additionally, the expression of PpHOS1 that encodes a C3HC4-type Really Interesting New Gene (RING) finger E3 ligase was induced in BABA-treated peach fruit in response to R. stolonifer attack, following which the specific PpWRKY22 protein was exclusively targeted by PpHOS1 for possible degradation. Notably, PpWRKY22 functions as a positive regulator in disease resistance, as determined by overexpression of PpWRKY22 in Arabidopsis thaliana, which conferred enhanced resistance to the fungus R. stolonifer. Moreover, the physical interaction between PpWRKY22 and PpTGA1 increased the transactivation of PpNPR1, PpPR1, PpPR2, and PpPR5 by PpWRKY22 alone, leading to elevated resistance of peach fruit against the fungus R. stolonifer. Taken together, our results indicated that PpWRKY22 might be a positive participant in BABA-primed resistance in peach fruit, which could involve the post-translational ubiquitination of PpWRKY22 by PpHOS1 and physical interaction between PpWRKY22 and PpTGA1 for modification and activation.

This study attempted to determine the transcriptomic responses of peach fruit to β-aminobutyric acid (BABA) elicitation and Rhizopus stolonifer inoculation and to identify the key differentially expressed genes (DEGs) and significantly enriched pathways between BABA + inoculation-versus-control and inoculation-versus-control pairwise comparisons. Furthermore, the regulatory linkage between the critical DEGs and their interacting proteins was investigated based on the expression of pathogenesis-related (PR) genes in the BABA-treated samples. The results showed that the transcription factor PpTGA1 possessed the highest degree in the protein-protein interaction (PPI) network and was identified as a critical DEG. PpTGA1 could directly interact with the significantly expressed PpNPR1 gene in the nucleus through the salicylic acid (SA)-dependent signalling pathway, eventually leading to high transcript levels of PpPR1 and PpPR1-like. In addition, an increased generation of redox signalling molecules (nitric oxide (NO) and SA) was accompanied by an obvious effect on the suppression of Rhizopus rot in peaches pretreated with BABA and subsequent R. stolonifer challenge. Thus, BABA elicitation and subsequent R. stolonifer inoculation positively modulated the intercellular redox state and consequently induced the translocation of the product of the highly expressed PpNPR1 gene to the nucleus, where it interacts with PpTGA1 and eventually strengthens defence-related gene expression and disease resistance.

The priming resistance induced by β-aminobutyric acid (BABA) is a cost-effective strategy to protect postharvest fruit from pathogen infection. The cross-linking underlying E3 ubiquitin ligases, WRKY transcription factors (TFs) and priming defense in peaches, however, remains poorly researched. In the present study, 50 mmol L−1 BABA could induce disease resistance at least by priming peach fruit for an accumulation in H2O2 content following subsequent Rhizopus stolonifer incubation, accompanied by a suppression of the disease incidence and lesion diameter during the incubation at 20 °C. Meanwhile, a WRKY TF (PpWRKY22) and an E3 ubiquitin ligase (PpHOS1) were identified specifically based on analysis and summarization of the differentially expressed genes and proteins in the transcriptome and proteome database of peaches, respectively. Moreover, the putative characterization of PpWRKY22, a Group IIe WRKY TF, and PpHOS1, a RING-type E3 ubiquitin ligase, was expounded. The expression of PpWRKY22 and PpHOS1 was up-regulated in the priming resistance of peach fruit against R. stolonifer, and the two nucleus-localized proteins physically interacted in vivo. Taken together, these findings bring new insights into the functional link between E3 ubiquitin ligases and WRKY TFs in priming resistance, and they enable new perspectives on enhancing the disease resistance of peaches.

Slug rivet interference-fit riveting is one of the advanced connection technologies which has been widely applied in aerospace manufacture. This article presents an appropriate numerical model simulating the slug rivet upset process with countersunk hole structure. Many previous studies have focused on the riveted lap joints without countersunk hole structure and ignored its related process parameters. The main difference is that the hole expansion would be inhomogeneous through the thickness direction due to the impact of countersunk hole. To improve the riveting quality and reduce the inhomogeneity scale of the interference distribution, the effects of two procedure parameters have been assessed. The analysis results significantly improve knowledge about the slug rivet installation process as well as the effects of the corresponding process parameters. The study will pave the way for further investigations.