Autophagy and Hsp70 activation alleviate oral epithelial cell death induced by food-derived hypertonicity

Stable intracellular and intercellular osmolarity is vital for all physiological processes. Although it is the first organ that receives food, the osmolarity around the mouth epithelium has never been systematically investigated. We found that oral epithelial cells are a population of ignored cells routinely exposed to hypertonic environments mainly composed of saline, glucose, etc. in vivo after chewing food. By using cultured oral epithelial cells as an in vitro model, we found that the hypotonic environments caused by both high NaCl and high glucose induced cell death in a dose- and time-dependent manner. Transcriptomics revealed similar expression profiles after high NaCl and high glucose stimulation. Most of the common differentially expressed genes were enriched in "mitophagy" and "autophagy" according to KEGG pathway enrichment analysis. Hypertonic stimulation for 1 to 6 h resulted in autophagosome formation. The activation of autophagy protected cells from high osmolarity-induced cell death. The activation of Hsp70 by the pharmacological activator handelin significantly improved the cell survival rate after hypertonic stimulation. The protective role of Hsp70 activation was partially dependent on autophagy activation, indicating a crosstalk between Hsp70 and autophagy in hypertonic stress response. The extract of the handelin-containing herb Chrysanthemum indicum significantly protected oral epithelial cells from hypertonic-induced death, providing an inexpensive way to protect against hypertonic-induced oral epithelial damage. In conclusion, the present study emphasized the importance of changes in osmolarity in oral health for the first time. The identification of novel compounds or herbal plant extracts that can activate autophagy or HSPs may contribute to oral health and the food industry.

Azospirillum tabaci sp. nov., a bacterium isolated from rhizosphere soil of Nicotiana tabacum L

Strain W712T was isolated from rhizosphere soil of Nicotiana tabacum L. collected from Kunming, south-west China. Cells were Gram-staining negative, aerobic, motile and rod shaped. The isolate grew at 20-45 °C (optimum 30 °C), pH 6.0-8.0 (optimum pH 7.0) and in the presence of up to 3.0% (w/v) NaCl (optimum 1%, w/v). Ubiquinone-10 was the only respiratory quinone type. Polar lipids contained diphosphatidylglycerol, phosphatidylmehtylethanolamine, phosphatidylglycerol, phosphatidylcholine and an unidentified aminolipid. The major fatty acids were detected as summed feature 8 (C18:1 ω7c or C18:1 ω6c), summed feature 3 (C16:1 ω7c or C16:1 ω6c) and C18:1 2OH. The genomic DNA G + C content was 68.7%. The ANI values were 94.3%, 93.3% and 93.6% between Azospirillum baldaniorum Sp245T, Azospirillum brasilense ATCC 49958T, Azospirillum formosense CC-Nfb-7T and strain W712T, respectively, which were lower than the prokaryotic species delineation threshold of 95.0-96.0%. The digital DNA-DNA hybridization values between A. baldaniorum Sp245T, A. brasilense ATCC 49958T, A. formosense CC-Nfb-7T and strain W712T indicated that the candidate represents a novel genomic species. According to the phenotypic and genotypic characteristics, we propose that strain W712T warrants the assignment to a novel species, for which the name Azospirillum tabaci sp. nov. (type strain W712T = CGMCC 1.18567T = KCTC 82186T) is proposed.

Citral Essential Oil-Loaded Microcapsules by Simple Coacervation and Its Application on Peach Preservation

Citral essential oil (CEO) was encapsulated by the single coalescence method, and its stability, release properties, and ability to maintain freshness were evaluated for the first time. The microshape characteristics of a CEO-loaded microcapsule (CM) were analyzed by inverted microscopy (OM) and scanning electron microscopy (SEM). The encapsulation efficiency, stability, and release behavior of CEO were evaluated using Fourier transform infrared spectroscopy (FTIR), thermogravimetric/differential thermal comprehensive analysis (TG/DSC), and gas chromatography mass spectrometry (GC/MS). Moreover, peaches were used to evaluate the preservation properties of the CEO-loaded microcapsule. The results showed that the microcapsule produced using simple coacervation had better microstructure and the ability to reduce and control the release of citral essential oil. The qualities of peaches, such as appearance changes, hardness, soluble solid content, total acids, and total bacterial counts, were significantly improved in the CM system during storage, in comparison with the control and cold storage groups. Therefore, the CM has potential applications and development prospects in the food, drug, and other industries.

NtERF4 promotes the biosynthesis of chlorogenic acid and flavonoids by targeting PAL genes in Nicotiana tabacum

Chlorogenic acid (CGA) and flavonoids are important secondary metabolites, which modulate plant growth and development, and contribute to plant resistance to various environmental stresses. ERF4 has been shown to be a repressor of anthocyanin accumulation in grape, but its full roles in regulating the biosynthesis of other phenylpropanoid compounds still needs to be further studied. In the present study, two NtERF4 genes were identified from N. tabacum genome. The expression level of NtERF4a was higher than that of NtERF4b in all the tobacco tissues examined. Over-expression of NtERF4a significantly promoted the accumulation of CGA and flavonoids in tobacco leaves, while silencing of NtERF4a significantly repressed the biosynthesis of CGA and flavonoids. RNA-seq analysis of NtERF4a-OE and WT plants revealed 8 phenylpropanoids-related differentially expressed genes (DEGs), including 4 NtPAL genes that encode key enzymes in the phenylpropanoid pathway. Activation of NtERF4a-GR fusion protein in tobacco significantly induced the transcription of NtPAL1 and NtPAL2 in the presence of protein synthesis inhibitor. Chromatin immunoprecipitation and Dual-Luc assays further indicated that NtERF4a could bind to the GCC box presented in the promoters of NtPAL1 and NtPAL2, thereby activating their transcription. Moreover, ectopic expression of NtERF4a induced the transcription of NtGSK1, NtMYC2, and NtJAZ3 genes, and enhanced the resistance of tobacco seedlings to salt and drought stresses, indicating multiple roles of NtERF4a in plants. Our findings revealed new roles of NtERF4a in modulating the accumulation of phenylpropanoid compounds in tobacco, and provided a putative target for improving phenylpropanoids synthesis and stress resistance in plants.

Identification of cell-type specificity, trans- and cis-acting functions of plant lincRNAs from single-cell transcriptomes

Long noncoding RNAs, including intergenic lncRNAs (lincRNAs), play a key role in various biological processes throughout the plant life cycle, and the advent of single-cell RNA sequencing (scRNA-seq) technology has opened up a valuable avenue for scrutinizing the intricate roles of lincRNAs in cellular processes. Here, we identified a new batch of lincRNAs using scRNA-seq data from diverse tissues of plants (rice, Arabidopsis, tomato, and maize). Based on well-annotated single-cell transcriptome atlases, plant lincRNAs were found to possess the same level of cell-type specificity as mRNAs and to be involved in the differentiation of certain cell types based on pseudo-time analysis. Many lincRNAs were predicted to play a hub role in the cell-type-specific co-expression networks of lincRNAs and mRNAs, suggesting their trans-acting abilities. Besides, plant lincRNAs were revealed to have potential cis-acting properties based on their genomic distances and expression correlations with the neighboring mRNAs. Furthermore, an online platform, PscLncRNA (http://ibi.zju.edu.cn/psclncrna/), was constructed for searching and visualizing all identified plant lincRNAs with annotated potential functions. Our work provides new insights into plant lincRNAs at single-cell resolution and an important resource for understanding and further investigation of plant lincRNAs.

Improving the Quality of Low-grade Tobacco by Enzymatic Treatment and Co-fermentation with Yeast and Lactic Acid Bacteria

Enzymatic treatment is a promising method to modulate the chemical composition, flavoring substances and to enhance the sensory quality of cigarettes. This study investigates the feasibility of enzymatic treatment in conjunction with co-fermentation with yeast and lactic acid bacteria to improve the quality of low-quality cigarettes. Amylase, flavourzyme, glucoamylase, protease, and their combinations were used for the enzymatic treatment of tobacco-sorghum by using the liquid-state fermentation method. The biochemical components and flavor substances of the fermented products were analyzed. The findings show that amylase and glucoamylase can effectively degrade starch into fermentable reducing sugars, facilitate microbial growth and proliferation, and significantly enhance the levels of flavoring alcohols and esters. Flavourzyme and glucoamylase, either individually or combined with amylase, achieved a more balanced distribution of flavor substances in the products. Additionally, flavourzyme was capable of increasing the content of guaiacol, solanesol, and 2-acetylpyrrole in the fermented products, thereby improving the richness and depth of the cigarette flavor. While the protease treatment group showed fewer flavor substances and higher nicotine content, which was detrimental to the quality of cigarettes. When integrating the fermentation products into low-quality cigarettes, flavourzyme and glucoamylase combined with amylase treatment received higher scores in sensory quality evaluations. This study provides a beneficial strategy for effectively improving the quality of low-quality cigarettes.