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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.[Graphic: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Although heat shock proteins (HSPs), a family of ubiquitous molecular chaperones, are well characterized in heat stress-related responses, their function in plant defense remains largely unclear. Here, we report the role of VvHSP24, a class B HSP from Vitis vinifera, in β-aminobutyric acid (BABA)-induced priming defense against the necrotrophic fungus Botrytis cinerea in grapes. Grapes treated with 10 mmol L–1 BABA exhibited transiently increased transcript levels of VvNPR1 and several SA-inducible genes, including PR1, PR2, and PR5. Additionally, phytoalexins accumulated upon inoculation with the gray mold fungus B. cinerea, which coincided with the action of a priming mode implicated in pathogen-driven resistance. Intriguingly, electrophoretic mobility shift (EMSA), yeast two-hybrid (Y2H) and His pull-down assays demonstrated that the nuclear chaperone VvHSP24 cannot modulate the transcript of PR genes but does directly interact with VvNPR1 in vivo or in vitro. Furthermore, we found that VvHSP24 overexpression enhanced the transcript levels of NPR1 and SA-responsive genes (PR1, PR2, and PR5) and increased the resistance of transgenic Arabidopsis thaliana to B. cinerea compared with wildtype Col-0. An opposite trend between CRISPR mutants of AtHSFB1 (the orthologous gene of VvHSP24 in Arabidopsis) and wildtype plants was observed. Hence, our results suggest that VvHSP24 has a potential role in NPR1-dependent plant resistance to fungal pathogen. BABA-induced priming defense in grapes may require posttranslational modification of the chaperone VvHSP24 to activate VvNPR1 transcript, leading to PR gene expressions and resistance phenotypes.

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.

Slug rivet should be installed by automatic drilling and riveting machine due to its special structure. The investigation on slug rivet is limited. In order to promote the application of slug rivet, this article conducts investigations on slug rivet installation process. For the understanding of the riveting quality of a riveted lap joint, it is essential to analyze the riveting parameters. There are numerous parameters associated with a riveting process such as squeezing force, rivet structure, countersunk hole structure, hole diameter, sheet thickness, and clamping force. Incorrect selection or variations in these parameters could directly affect the riveting quality. The aim of this article is to study the impact of the aforementioned parameters on the riveting quality of a riveted aircraft structure. The interference condition is considered as the main quality control criterion. The squeezing force is introduced as the most important parameter for the riveting quality. The study provides a deeper understanding of the slug rivet installation process with the impacts of its riveting parameters. This study will pave the way for further researches and extend the scope of the slug rivet application to more structural connections.

In aircraft assembly, the influence of interlayer burr formation in drilling of stacked metal sheets is an important problem. This article aims to develop a deeply understanding of the relationship between the clamping force and interlayer burr formation. The minimum clamping force, which would just make the stacked sheets entirely contact each other, is considered as the optimal clamping force. Hence, the additional deformation would appear at the contact region when the clamping force keeps rising up. The optimal clamping force is obtained first through theoretical calculation. Then, numerical simulations and experimental verifications are conducted. The results demonstrate the effectiveness of the theoretical analysis based on shell theory.