Changes of Volatile Organic Compounds of Different Flesh Texture Pears during Shelf Life Based on Headspace Solid-Phase Microextraction with Gas Chromatography-Mass Spectrometry.

Aroma is an important sensory factor in evaluating the quality of pear fruits. This study used headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) to analyze the volatile organic compounds (VOCs) of three crispy pears and five soft pears during shelf life, and the changes in soluble solids content (SSC) were analyzed. The results showed that the SSC of the soft pears such as Nanguoli, Jingbaili and Louis was always higher than that of the crispy pears throughout shelf life. A total of 160 VOCs were detected in the eight pear varieties. Orthogonal partial least squares discriminant analysis (OPLS-DA) and hierarchical cluster analysis (HCA) combined with predictor variable importance projection (VIP) showed that the eight pear varieties could be obviously classified into six groups according to the differences in their VOCs, and 31 differential VOCs were screened out, which could be used to differentiate between pears with different flesh textures. The results of clustering heat map analysis showed that, with the extension of shelf life, the content of each different VOC did not change much in crispy pears, whereas the difference in soft pears was larger. This study confirmed the potential of determining the optimal shelf life of different pear varieties about aroma evaluation and studying the mechanism of differences in VOCs in the future.

Metabolomic and transcriptomic analyses highlight the influence of lipid changes on the post-harvest softening of Pyrus ussurian Max. 'Zaoshu Shanli'.

How lipids influence post-harvest softening in pears is not well understood. LC-MS/MS (Liquid chromatography-tandem mass spectrometry) and RNA-Seq analyses of 'Zaoshu Shanli' (ZSSL) pears were conducted during post-harvest storage. This approach enabled the identification of 98 different metabolites that upregulated and 95 that downregulated at 18 days post-harvest in ZSSL fruits to day 0. Metabolites were significantly enriched in KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways including glycerophospholipid metabolism and glycosylphosphatidylinositol (GPI)-anchor biosynthesis. When comparing fruits from day 18 to those from day 0 post-harvest, RNA-seq analyses further highlighted 6496 differentially expressed genes (DEGs) in ZSSL fruits that were significantly enriched in KEGG pathways including glycerophospholipid metabolism and fatty acid degradation. Overall, these results suggested that glycerophospholipid metabolism is closely related to the post-harvest softening of pears. Further research will be essential in order to fully explore the functional implications of and mechanistic basis for these findings.

Structural evolution of dispersed hydrophobic association in a hydrogel analyzed by the tensile behavior.

The use of dispersed cross-links with different levels of strength is one of the most successful strategies for toughening a hydrogel. By using a model hydrogel having dispersed association of single-component short alkyl chains, this work demonstrates that the differential modulus-elongation relation derived from tensile curves can reflect the structural evolution of dispersed cross-links at a molecular level. This analysis method allows for decoupling the mechanical contribution of strong and weak hydrophobic clusters, which serve as the minor and major cross-links in our system, respectively. At small deformation, the weak hydrophobic associations majorly determine the stiffness, and their rupture releases folded partial chains to endow deformation capacity. At large deformation, the strength ratio of strong and weak hydrophobic association should be balanced to achieve the optimal strength. Furthermore, the structural parameters of these partial chains, including the Kuhn number, the Kuhn length and the chain conformation, are determined based on scaling theory of extensibility. These results allow for correlating the apparent mechanics to the structural parameters of the dispersed hydrophobic association, paving the way for customized mechanics for specific applications.

[Prediction of potential geographical distribution patterns of Pyrus xerophila under different climate scenarios.] / ä¸åŒæ°”å€™æƒ æ™¯ä¸‹æœ¨æ¢¨æ½œåœ¨åœ°ç†åˆ†å¸ƒæ ¼å±€å˜åŒ–çš„é¢„æµ‹.

Pyrus xerophila has strong resistance to drought, cold, salt, and rust. It is one of the main rootstock types of pear in Northwest China, with high production value. However, its habitat is seriously damaged. The prediction of the geographical distribution of P. xerophila under different climate scenarios will provide important scientific basis for rational development and utilization of resources and the protection of diversity. Based on MaxEnt model and ArcGIS spatial analysis, the potential spatial distribution pattern of P. xerophila in the current and future (2050, 2070) was constructed using comprehensive and accurate distribution records and high-resolution environmental data, and the relative importance of environmental factors was evaluated. The results showed that the suitable habitat area of P. xerophila was 3.32×105 km2, mainly located in eastern Qinghai, southern Gansu, southern Ningxia, central Shaanxi, southern Shanxi and western Henan. Mean UV-B of the month with lowest UV-B and altitude were identified as the critical factors shaping habitat availability for P. xerophila. Overall, with global warming, the potential habitat for P. xerophila might decrease in 2050 and 2070 under different CO2 climate scenarios. Real-time monitoring of P. xerophila populations should be enhanced.

De novo assembly of a wild pear (Pyrus betuleafolia) genome.

China is the origin and evolutionary centre of Oriental pears. Pyrus betuleafolia is a wild species native to China and distributed in the northern region, and it is widely used as rootstock. Here, we report the de novo assembly of the genome of P. betuleafolia-Shanxi Duli using an integrated strategy that combines PacBio sequencing, BioNano mapping and chromosome conformation capture (Hi-C) sequencing. The genome assembly size was 532.7 Mb, with a contig N50 of 1.57 Mb. A total of 59 552 protein-coding genes and 247.4 Mb of repetitive sequences were annotated for this genome. The expansion genes in P. betuleafolia were significantly enriched in secondary metabolism, which may account for the organism's considerable environmental adaptability. An alignment analysis of orthologous genes showed that fruit size, sugar metabolism and transport, and photosynthetic efficiency were positively selected in Oriental pear during domestication. A total of 573 nucleotide-binding site (NBS)-type resistance gene analogues (RGAs) were identified in the P. betuleafolia genome, 150 of which are TIR-NBS-LRR (TNL)-type genes, which represented the greatest number of TNL-type genes among the published Rosaceae genomes and explained the strong disease resistance of this wild species. The study of flavour metabolism-related genes showed that the anthocyanidin reductase (ANR) metabolic pathway affected the astringency of pear fruit and that sorbitol transporter (SOT) transmembrane transport may be the main factor affecting the accumulation of soluble organic matter. This high-quality P. betuleafolia genome provides a valuable resource for the utilization of wild pear in fundamental pear studies and breeding.

MicroRNA-21-5p targeting PDCD4 suppresses apoptosis via regulating the PI3K/AKT/FOXO1 signaling pathway in tongue squamous cell carcinoma.

The aim of the present study was to analyze the role of microRNA (miRNA)-21-5p in tongue squamous cell carcinoma (TSCC), predict the target gene of miR-21-5p and provide novel strategies for gene therapy in TSCC treatment. The expression levels of miRNA-21-5p in TSCC tissues were analyzed using reverse transcription quantitative polymerase chain reaction, and the effects of miRNA-21-5p on cell proliferation, invasion and apoptosis and the expression levels of target protein PDCD4 in the Cal 27 and SCC9 cell lines were determined. PI3K/AKT/Forkhead Box O1 (FOXO1) pathway-associated protein expression levels were evaluated by western blot analysis. miRNA-21-5p was consistently upregulated in TSCC tissues compared with normal tissues. Inhibition of miR-21-5p inhibited cell proliferation and invasion, and promoted cell apoptosis. A luciferase reporter assay confirmed that PDCD4 was the target of miR-21-5p. Inhibition of miRNA21-5p suppressed the PI3K/Akt/FOXO1 signaling pathway. The results from the present study indicated that miR-21-5p-targeting PDCD4 suppresses apoptosis in human TSCC cell lines. This anti-apoptotic effect was achieved by regulating the PI3K/Akt/FOXO1 signaling pathway. These data represent the basis for a promising novel strategy for the treatment of TSCC.

Postharvest metabolomic changes in Pyrus ussuriensis Maxim. wild accession 'Zaoshu Shanli'.

There are strong economic drivers for understanding the process of fruit post-harvest softening. In this study, liquid chromatography with electrospray ionization tandem mass spectrometry was used to analyze metabolite changes in 'Zaoshu Shanli' fruit after different storage periods; this wild accession of Pyrus ussuriensis presents good fruit quality and relatively low flesh firmness after fruit storage. The lipid metabolites in 'Zaoshu Shanli' fruit were significantly higher at 18 days of storage compared with those at 0 days of storage, and glycerophospholipid metabolism was different metabolic pathway. It was therefore speculated that lipid metabolism play an important role in pear fruit post-harvest processes and softening. Furthermore, the abscisic acid and trans-zeatin contents in 'Zaoshu Shanli' fruit at 18 days of storage were significantly greater than those at 0 days of storage. Therefore, it was speculated that the abovementioned hormones play an important role in pear fruit post-harvest softening. Together, these results provide fundamental insight into the reasonable control of pear fruit post-harvest softening and lay a solid foundation for additional research.

[Leaf morphology and photosynthetic characteristics of wild Ussurian pear in China].

The wild Ussurian pear was the most important wild pear resource in northern China, belonging to the most hardiness species. Taking 48 accessions of wild Ussurian pear and 2 accessions of cultivated Ussurian pear as test materials, this paper studied the morphology of leaves, chlorophyll content, and photosynthetic characteristics. We compared the difference between the wild and cultivated Ussurian pear, analyzed the photosynthetic characteristics of wild Ussurian pear, clarified the interrelationships between the indices, and established significant linear equations of photosynthesis and water-related physiological indices. The results showed that the leaf morphological index, chlorophyll content and photosynthetic indices for cultivated Ussurian pear were significantly lower than their average values for wild Ussurian pear. The specific leaf area (SLA), leaf dry matter content ( LDMC) , and intercellular CO2 concentration had low coefficients of variation, and the other 8 indices had variation coefficient indices between 0.12-0.41. So, the level of diversity was high, indicating obvious difference in photosynthetic characteristic of wild pear resources in China. The photosynthetic indices were significantly correlated with chlorophyll composition (Chl a/b) and LDMC. The photosynthetic rate had significant exponential correlation with the intercellular CO2 concentration, transpiration rate, and stomatal conductance. The photosynthetic rate was mainly affected by stomatal limitation. The wild variety 'Jinzhoushanli' was selected as high photosynthetic genetic resource.

A multicenter study on expressions of vascular endothelial growth factor, matrix metallopeptidase-9 and tissue inhibitor of metalloproteinase-2 in oral and maxillofacial squamous cell carcinoma.

BACKGROUND: Vascular endothelial growth factor (VEGF), matrix metallopeptidase-9 (MMP-9) and tissue inhibitor of metalloproteinase-2 (TIMP-2) are potential markers of oral and maxillofacial squamous cell carcinoma (SCC). OBJECTIVES: To explore the association between expression of VEGF, MMP-9 and TIMP-2 in oral and maxillofacial SCC and clinicopathological factors. PATIENTS AND METHODS: Immunohistochemical Envision method was used to analyze the expression of VEGF, MMP-9 and TIMP-2 in 54 cases of oral and maxillofacial SCC and the association with clinicopathological factors such as clinical staging and lymphatic metastasis. RESULTS: Brownish-yellow staining is correlated with positive expression of VEGF, MMP-9 and TIMP-2. Positive expression of VEGF and MMP-9 was correlated with lymphatic metastasis, and their positive expression rates were significantly higher in patients with lymphatic metastasis than those without it (VEGF: χ(2) = 30.00; P = 0.001; MMP-9: χ(2) = 18.27, P = 0.001). The positive expression rate of MMP-9 decreased at earlier clinical stages (P < 0.05). Positive expression of TIMP-2 was correlated with lymphatic metastasis, clinical staging and T classification. The positive rate of TIMP-2 expression in patients with lymphatic metastasis was significantly lower than those without it (χ(2) = 26.74, P = 0.002), which significantly reduced with increasing clinical stage and T classification (P < 0.05). CONCLUSIONS: Lymphatic metastasis in patients with oral and maxillofacial SCC is closely related to the positive expression of VEGF, MMP-9 and TIMP-2. MMP-9 and TIMP-2 can affect the progression of cancer, which is valuable for studies on oral and maxillofacial SCC genes.

Identifying the candidate genes involved in the calyx abscission process of 'Kuerlexiangli' (Pyrus sinkiangensis Yu) by digital transcript abundance measurements.

BACKGROUND: 'Kuerlexiangli' (Pyrus sinkiangensis Yu), a native pear of Xinjiang, China, is an important agricultural fruit and primary export to the international market. However, fruit with persistent calyxes affect fruit shape and quality. Although several studies have looked into the physiological aspects of the calyx abscission process, the underlying molecular mechanisms remain unknown. In order to better understand the molecular basis of the process of calyx abscission, materials at three critical stages of regulation, with 6000 × Flusilazole plus 300 × PBO treatment (calyx abscising treatment) and 50 mg.L-1GA3 treatment (calyx persisting treatment), were collected and cDNA fragments were sequenced using digital transcript abundance measurements to identify candidate genes. RESULTS: Digital transcript abundance measurements was performed using high-throughput Illumina GAII sequencing on seven samples that were collected at three important stages of the calyx abscission process with chemical agent treatments promoting calyx abscission and persistence. Altogether more than 251,123,845 high quality reads were obtained with approximately 8.0 M raw data for each library. The values of 69.85%-71.90% of clean data in the digital transcript abundance measurements could be mapped to the pear genome database. There were 12,054 differentially expressed genes having Gene Ontology (GO) terms and associating with 251 Kyoto Encyclopedia of Genes and Genomes (KEGG) defined pathways. The differentially expressed genes correlated with calyx abscission were mainly involved in photosynthesis, plant hormone signal transduction, cell wall modification, transcriptional regulation, and carbohydrate metabolism. Furthermore, candidate calyx abscission-specific genes, e.g. Inflorescence deficient in abscission gene, were identified. Quantitative real-time PCR was used to confirm the digital transcript abundance measurements results. CONCLUSIONS: We identified candidate genes that showed highly dynamic changes in expression during the calyx abscission process. These genes are potential targets for future functional characterization and should be valuable for exploration of the mechanisms of calyx abscission, and eventually for developing methods based on small molecule application to induce calyx abscission in fruit production.