Channel: HORTICULTURE http://journals.caass.org.cn/zgnykx EN-US http://journals.caass.org.cn/zgnykx/EN/current.shtml http://journals.caass.org.cn/zgnykx 5 【Objective】 Grape seeds have high bioactivity because they are rich in many metabolites. The objective of this study was to comprehensively identify the metabolite components in grape seeds, to compare and to analyze the differences of metabolites among different varieties, and to explore the relationship between metabolites in grape seeds and skin color and variety origin, so as to provide a reference basis for further development and utilization of grape seeds. 【Method】 The mature seeds of purple-skinned Kyoho (V. labruscana: V. labrusca × V. vinifera, JFS), pink-skinned Wink (V. vinifera, WKS), and yellow-skinned Italia (V. vinifera, YDS) were used for widely targeted metabolomics analysis by UPLC-MS/MS. The metabolites were identified and compared by multivariate statistical methods. 【Result】 The quality of metabolomics data was good, and the data of samples within groups was repetitive and the differences in the data of samples among groups were existed. A total of 514 metabolites were identified in the seeds of three grape varieties, including 6 primary metabolites, such as amino acids and lipids, and 20 secondary metabolites, such as proanthocyanidins and resveratrol. Among different varieties, the metabolite components were similar but the metabolite contents were significantly different. The relative contents of most metabolites were high in the dark variety Kyoho, followed by the light variety Wink, but low in the colorless variety Italy, indicating that the metabolite contents in grape seeds might be positively correlated with the skin color. The relative contents of metabolites in the seeds of Wink and Italia were similar, while they were greatly different from those of Kyoho, indicating that the metabolite contents in grape seeds might be related to the variety origin. The differential metabolites among different varieties were mainly involved in phenylpropane biosynthesis, anthocyanin synthesis, lipid metabolism, etc. pathway. There were many phenolic compounds in the differential metabolites and the metabolites with the large difference were mainly flavonoids. Grape seeds were rich in phenols and lipids. In addition to monomeric flavane-3-ols and their polymers, the relative contents of other phenolic compounds such as flavones and flavonols were also high. There was no significant difference in the relative contents of resveratrol among the three varieties. The relative contents of glyceryl phosphatide such as lysophosphatidylcholine were high, while those of linolenic acid were low. There was little difference in the relative contents of lipids among different varieties. 【Conclusion】 The metabolite components in grape seeds of different varieties were similar, while the metabolite contents were related to the skin color and the variety origin. Phenols and lipids were important components of metabolites in grape seeds and could be used as good sources for food and other processing industries.

]]> 【Objective】 Here, two ecotypes of P. betulaefolia from Huaguo Mountain, Lianyungang (the salt-tolerant ecotype, D) and Purple Mountain, Nanjing (the common ecotype, U) were collected for this research. The purpose of this study was to analyze the role of transcription factor genes in the roots of two ecotypes of P. betulaefolia differing in terms of salt stress. Transcription factors involving in the regulation of the salt tolerance of different P. betulaefolia ecotypes were identified on the grounds of differential expression under salt stress and the relationship between the methylation status and the relative expression level of relevant tolerance genes after exposure to salt stress was investigated. 【Method】 The 90-day-old P. betulaefolia seedlings were grown hydroponically in Hoagland’s nutrient solution supplemented with 200 mmol∙L^-1 NaCl, with seedlings grown in Hoagland’s nutrient solution as the control. The sodium ion content in the tissues was determined by flame graphite furnace atomic absorption spectrometry. Whole-genome DNA methylation analysis and transcriptome sequencing were performed on three replicates for the following four root samples: ecotype D and ecotype U, each grown in the presence or absence of salt stress. Bioinformatics analysis of transcription factor gene expression under salt stress at the levels of transcriptional regulation and epigenetic methylation were carried out using transcriptome sequencing data and whole-genome DNA methylation results, respectively. Then, McrBC-PCR and real-time fluorescence quantitative PCR (qPCR) were used to confirm the levels of methylation and transcription of differential transcription factor genes. 【Result】 After exogenous NaCl treatment for 24 h, the concentration of sodium ions in P. betulaefolia roots increased significantly, with the increase in sodium ion concentration in the salt-tolerant ecotype being significantly less than that in the common ecotype. In the whole seedling, the final salt concentration of tolerant ecotype was only 73.1% of that of the common ecotype. Whereas, in the roots, the sodium content of the salt-tolerant ecotype was 1.1 times of that in the common ecotype. These results indicated that the salt-tolerant ecotype could store more sodium ions in roots and limit their upward transport after salt stress. A total of 2 682 transcription factor (TF) genes from 69 gene families were detected in roots. Among them, 243 TF genes displayed differential expression in response to salt stress, including 37 AP2/ERF, 19 bHLH, 7 bZIP, 10 HD-Zip, 30 MYB, 18 NAC, 8 WRKY, and 23 ZFP family genes. The global methylation level of transcription factor genes in the genome of the salt-tolerant rootstock ecotype decreased, whereas the overall methylation level of these genes in the common ecotype increased after exposure to 200 mmol∙L^-1 NaCl. The differentially methylated regions in both ecotypes were mainly in the position of gene promoters, with the type of differentially methylated sequences being mostly mCHH, constituting more than 93% of the sum of all three types of methylated sequences. The expression levels of twenty-three transcription factor genes, which belonged to the AP2/ERF, bHLH, DREB, GRAS, GT factor, HB Zip, MYB, NAC, Trihelix, and zinc-finger ZFP gene families, were upregulated, and their methylation levels were downregulated in both two ecotypes in response to salt stress. These genes may be involved in the regulation of sodium uptake and accumulation in roots under salt stress. The expression patterns and promoter methylation of representative candidate genes identified by bioinformatics analysis were confirmed by qPCR and McrBC-qPCR.【Conclusion】 The differentially expressed genes in roots of P. betulaefolia under salt stress included 243 transcription factor genes in both ecotypes. The methylation changes in DNA sequences in eight transcription factor genes (PbERF2, PbGT3, PbZAT10.1, PbSCL33, PbDREB1, PbZAT10.2, PbERF53, and PbNAC72) were correlated with their transcriptional activity. Our results provided preliminary experimental evidence for supporting a relationship between promoter DNA methylation and expression of TF genes in P. betulaefolia in response to salt stress as part of the molecular role of TFs involved in the regulation of salt tolerance among different P. betulaefolia ecotypes, which would increase our understanding of the role of epigenetics in the response of woody trees to abiotic stress.

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