Kiwifruit (Actinidia spp.) is a climacteric fruit with high sensitivity to ethylene, influenced by multiple ethylene-responsive structural genes and transcription factors. However, the roles of other ...post-transcriptional regulators (e.g. miRNAs) necessary for ripening remain elusive.
High-throughput sequencing sRNAome, degradome and transcriptome methods were used to identify further contributors to ripening control in the kiwifruit (A. deliciosa cv ‘Hayward’).
Two NAM/ATAF/CUC domain transcription factors (AdNAC6 and AdNAC7), both predicted targets for miR164, showed significant upregulation by exogenous ethylene. Gene expression analysis and luciferase reporter assays indicated that Ade-miR164 and one of its precursor miRNAs (Ade-MIR164b) were repressed by ethylene treatment and negatively correlated with AdNAC6/7 expression. Subsequent analysis indicated that both AdNAC6 and AdNAC7 proteins are transcriptional activators and physically bind the promoters of AdACS1 (1-aminocyclopropane-1-carboxylate synthase), AdACO1 (1-aminocyclopropane-1-carboxylic acid oxidase), AdMAN1 (endo-β-mannanase) and AaTPS1 (terpene synthase). Moreover, subcellular analysis indicated that the location of the AdNAC6/7 proteins was influenced by Ade-miR164.
Multiple omics-based approaches revealed a novel regulatory link for fruit ripening that involved ethylene-miR164-NAC. The regulatory pathway for miR164-NAC is present in various fruit (e.g. Rosaceae fruit, citrus, grape), with implications for fruit ripening regulation.
To assess the efficacy of probiotic Lactobacillus on serum lipids using a meta-analysis of randomized, controlled trials.
Fifteen studies containing 15 trials, with 976 subjects were included. The ...pooled WMD was calculated by random effects model.
Probiotic Lactobacillus consumption significantly reduced TC by 0.26mmol/l (95% CI, -0.40 to -0.12) and LDL-C by 0.23mmol/l (95% CI, -0.36 to -0.10). Subgroup analysis of trials found significantly reduction of TC using L. plantarum and reduction of LDL-C using L. plantarum or L. reuteri. No significant effects were found on TG and HDL-C levels after supplementation with probiotic Lactobacillus. While, subgroup analysis found significantly beneficial effects on TG and HDL-C by consuming synbiotic food, containing L. sporogenes and inulin.
Consuming probiotic Lactobacillus, especially L. reuteri and L. plantarm, could reduce TC and LDL-C significantly. The study also suggested significantly beneficial effects on TG and HDL-C by consuming synbiotic food, containing L. sporogenes and inulin.
A facile synthesis of cyclopropenes and fluorinated cyclopropanes from readily available alkyl triflones was developed. The reaction, regardless of electronic effect, gave products in good to ...excellent yields and moderate diastereoselectivity. The mechanism may involve tandem Michael addition of triflones/intramolecular nucleophilic cyclization (elimination of ‐SO2CF3)/elimination of fluoride.
Various cyclopropenes and fluorinated cyclopropanes were prepared from readily available alkyl triflones and electron‐deficient alkenes via a Michael addition initiated ring closure (MIRC) process. This protocol not only has a broad substrates scope but also achieves good chemical yields and moderate diastereoselectivity. The mechanism may involve tandem Michael addition of triflones/intramolecular nucleophilic cyclization (elimination of ‐SO2CF3)/elimination of fluoride.
Summary
Chlorophyll degradation naturally occurs during plant senescence. However, in fruit such as citrus, it is a positive characteristic, as degreening is an important colour development ...contributing to fruit quality. In the present work, Citrus sinensis Osbeck, cv. Newhall fruit was used as a model for chlorophyll degradation. An ethylene response factor, CitERF13, was isolated and its transcriptional changes were closely correlated with fruit peel degreening during development or in response to ethylene. Dual‐luciferase and yeast one‐hybrid assays, as well as motif mutation, indicated that CitERF13 directly binds to the CitPPH promoter and enhances its activity. Transient and stable over‐expression of CitERF13 resulted in rapid chlorophyll degradation in Nicotiana tabacum leaves and led to accumulation of pheophorbide (Pheide) a, a metabolite of pheophorbide hydrolase (PPH). Similar results were observed from transient transformation of CitERF13 in citrus fruit peel. Moreover, this function of CitERF13 was conserved within Arabidopsis and tomato, as the homologs AtERF17 and SlERF16 similarly acted as activators of PPH genes and accelerators of chlorophyll degradation.
Significance Statement
Chlorophyll degradation in the fruit is a desired trait in citrus, so understanding the underlying molecular mechanisms is important for citrus breeding. Here we show that an ethylene response factor directly binds to the promoter of PPH, a gene encoding pheohorbide hydrolase, a key mark of chlorophyll degradation.
Summary
Ethylene plays an important role in regulating fruit ripening by triggering dynamic changes in expression of ripening‐associated genes, but the functions of many of these genes are still ...unknown.
Here, a methionine sulfoxide reductase gene (AdMsrB1) was identified by transcriptomics‐based analysis as the gene most responsive to ethylene treatment in ripening kiwifruit.
The AdMsrB1 protein exhibits a stereospecific activity toward the oxidative stress‐induced R enantiomer of methionine sulfoxide (MetSO), reducing it to methionine (Met). Stable overexpression of AdMsrB1 in kiwifruit significantly increased the content of free Met and 1‐aminocyclopropane‐1‐carboxylic acid (ACC), the immediate precursor of ethylene, and increased ethylene production. Dual‐luciferase assays indicated that the AdMsrB1 promoter was not directly upregulated by ethylene treatment but was modulated by two ethylene‐inducible NAM/ATAF/CUC transcription factors (AdNAC2 and AdNAC72) that bind directly to the AdMsrB1 promoter. Overexpression of AdNAC72 in kiwifruit not only enhanced AdMsrB1 expression, but also increased free Met and ACC content and ethylene production rates.
This finding establishes an unexpected regulatory loop that enhances ethylene production and the concentration of its biosynthetic intermediates.
Lignin biosynthesis is regulated by many transcription factors, such as those of the MYB and NAC families. However, the roles of AP2/ERF transcription factors in lignin biosynthesis have been rarely ...investigated. Eighteen EjAP2/ERF genes were isolated from loquat fruit (Eriobotrya japonica), which undergoes postharvest lignification during low temperature storage. Among these, expression of EjAP2‐1, a transcriptional repressor, was negatively correlated with fruit lignification. The dual‐luciferase assay indicated that EjAP2‐1 could trans‐repress activities of promoters of lignin biosynthesis genes from both Arabidopsis and loquat. However, EjAP2‐1 did not interact with the target promoters (Ej4CL1). Yeast two‐hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays indicated protein–protein interactions between EjAP2‐1 and lignin biosynthesis‐related EjMYB1 and EjMYB2. Furthermore, repression effects on the Ej4CL1 promoter were observed with the combination of EjAP2‐1 and EjMYB1 or EjMYB2, while EjAP2‐1 with the EAR motif mutated (mEjAP2‐1) lost such repression, although mEjAP2‐1 still interacted with EjMYB protein. Based on these results, it is proposed that EjAP2‐1 is an indirect transcriptional repressor on lignin biosynthesis, and the repression effects were manifested by EAR motifs and were conducted via protein–protein interaction with EjMYBs.
Heat stress is a major abiotic stress for plants, which can generate a range of biochemical and genetic responses. In ‘Ponkan’ mandarin fruit, hot air treatment (HAT) accelerates the degradation of ...citric acid. However, the transcriptional regulatory mechanisms of citrate degradation in response to HAT remain to be elucidated. Here, 17 heat shock transcription factor sequences were isolated, and dual‐luciferase assays were employed to investigate whether the encoded proteins that could trans‐activate the promoters of key genes in the GABA shunt, involved in citrate metabolism. We identified four heat shock transcription factors (CitHsfA7, CitHsfA3, CitHsfA4b and CitHsfA8) that showed trans‐activation effects on CitAco3, CitIDH3 and CitGAD4, respectively. Transient expression of the CitHsfs in citrus fruits indicated that CitHsfA7 was the only factor that resulted in a significant lowering of the citric acid content, and these results were confirmed by a virus‐induced gene silencing system (VIGS). Sub‐cellar localization showed that CitHsfA7 is located in the nucleus and is capable of binding directly to a putative HSE in the CitAco3 promoter and enhance its expression. We proposed that the induction of CitHsfA7 transcript level contributes to citric acid degradation in citrus fruit, via modulation of CitAco3 in response to HAT.
A heat shock transcription factor CitHsfA7 was characterized in citrus, which accelerates citric acid degradation via transcriptional regulating the aconitase gene (CitAco3) in response to heat stress. CitHsfA7 can be considered a key regulator mediating the role of heat treatment on citric acid degradation.
Although the solventless method for synthesizing benzoxazine resins has the advantage of low cost, the impurities involved in the products such as oligomers and original phenols significantly weaken ...the properties of polybenzoxazines. Herein, the commercialized BA‐a (benzoxazine derived from bisphenol‐A, aniline, and formaldehyde) resin obtained from a solventless method is modified by phthalonitrile through the reaction between phenol groups and 4‐nitrophtahlonitrile. The structures of obtained resins have been confirmed by 1H and 13C nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR). In addition, the ring‐opening polymerization behavior of each resin has been studied by differential scanning calorimetry and in situ FTIR. Furthermore, the thermal properties of the cross‐linked thermosets were measured by thermomechanical analysis and thermogravimetric analysis. The phthalonitrile‐functionalized benzoxazine resin shows a low polymerization temperature with the maximum of exothermic peak centered at 218.7 °C, and its corresponding polybenzoxazine exhibits excellent thermal stability, with a high Td5 value (346 °C) and high char yield (42.78%).
Phthalonitrile functionality is first introduced into a BA‐a type benzoxazine resin obtained from a solventless method to enhance its thermal stability. The modified resin shows low polymerization temperature but high thermal stability during the polymerization process. The polybenzoxazine derived from phthalonitrile modified benzoxazine exhibits excellent thermal stability, appointing this resin as a good candidate for high‐performance applications.
Chrysanthemums (Chrysanthemum morifolium Ramat.) exhibit a variety of flower colors due to their differing abilities to accumulate anthocyanins. One MYB member, CmMYB6, has been verified as a ...transcription regulator of chrysanthemum genes involved in anthocyanin biosynthesis; however, the co-regulators for CmMYB6 remain unclear in chrysanthemum. Here, the expression pattern of CmbHLH2, which is clustered in the IIIf bHLH subgroup, was shown to be positively correlated with the anthocyanin content of cultivars with red, pink and yellow flower colors, respectively. CmbHLH2 significantly upregulated the CmDFR promoter and triggered anthocyanin accumulation when co-expressed with CmMYB6. Yeast one-hybrid analyses indicated that CmbHLH2 was able to bind directly to the CmDFR promoter. Moreover, yeast two-hybrid assays indicated protein-protein interaction between CmbHLH2 and CmMYB6. These results suggest that CmbHLH2 is the essential partner for CmMYB6 in regulating anthocyanin biosynthesis in chrysanthemum.
SUMMARY
Most of kiwifruit cultivars (e.g. Actinidia chinensis cv. Donghong, “DH”) were sensitive to waterlogging, thus, waterlogging resistant rootstocks (e.g. Actinidia valvata Dunn, “Dunn”) were ...widely used for kiwifruit industry. Those different species provided ideal materials to understand the waterlogging responses in kiwifruit. Compared to the weaken growth and root activities in “DH”, “Dunn” maintained the relative high root activities under the prolonged waterlogging. Based on comparative analysis, transcript levels of pyruvate decarboxylase (PDCs) and alcohol dehydrogenase (ADHs) showed significantly difference between these two species. Both PDCs and ADHs had been significantly increased by waterlogging in “DH”, while they were only limitedly triggered by 2 days stress and subsided during the prolonged waterlogging in “Dunn”. Thus, 19 differentially expressed transcript factors (DETFs) had been isolated using weighted gene co‐expression network analysis combined with transcriptomics and transcript levels of PDCs and ADHs in waterlogged “DH”. Among these DETFs, dual luciferase and electrophoretic mobility shift assays indicated AcMYB68 could bind to and trigger the activity of AcPDC2 promoter. The stable over‐expression of AcMYB68 significantly up‐regulated the transcript levels of PDCs but inhibited the plant growth, especially the roots. Moreover, the enzyme activities of PDC in 35S::AcMYB68 were significantly enhanced during the waterlogging response than that in wild type plants. Most interestingly, comparative analysis indicated that the expression patterns of AcMYB68 and the previously characterized AcERF74/75 (the direct regulator on ADHs) either showed no responses (AcMYB68 and AcERF74) or very limited response (AcERF75) in “Dunn”. Taken together, the restricted responses of AcMYB68 and AcERF74/75 in “Dunn” endow its waterlogging tolerance.
Significance Statement
Comparative analysis on Actinidia chinensis cv. Donghong (“DH”) and A. valvata Dunn (“Dunn”) had been carried out, and found that the higher root activities in “Dunn” contributed to its tolerance to waterlogging stress. Based on transcriptome data, AcMYB68, AcERF74 and AcERF75 had been continuously triggered during waterlogging stress in “DH”, while they either showed no responses (AcMYB68 and AcERF74) or very limited response (AcERF75) in “Dunn”. A stable over‐expression of AcMYB68 significantly up‐regulated PDCs expression, and weakened the root activities and growth compared to wild type “DH” plants.
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