Metabolomics and Transcriptomics Provide Insights into Lipid Biosynthesis in the Embryos of Walnut (<i>Juglans regia</i> L.)
Walnut (<i>Juglans regia</i> L.) is an important woody oilseed tree species due to its commercial value. However, the regulation mechanism of walnut oil accumulation is still poorly understood, which restricted the breeding and genetic improvement of high-quality oil-bearing walnuts. In...
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MDPI AG
2023-01-01
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| Series: | Plants |
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| Online Access: | https://www.mdpi.com/2223-7747/12/3/538 |
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| author | Manman Liang Xuemei Zhang Qinglong Dong Han Li Suping Guo Haoan Luan Peng Jia Minsheng Yang Guohui Qi |
| author_facet | Manman Liang Xuemei Zhang Qinglong Dong Han Li Suping Guo Haoan Luan Peng Jia Minsheng Yang Guohui Qi |
| author_sort | Manman Liang |
| collection | DOAJ |
| description | Walnut (<i>Juglans regia</i> L.) is an important woody oilseed tree species due to its commercial value. However, the regulation mechanism of walnut oil accumulation is still poorly understood, which restricted the breeding and genetic improvement of high-quality oil-bearing walnuts. In order to explore the metabolic mechanism that regulates the synthesis of walnut oil, we used transcriptome sequencing technology and metabolome technology to comprehensively analyze the key genes and metabolites involved in oil synthesis of the walnut embryo at 60, 90, and 120 days after pollination (DAP). The results showed that the oil and protein contents increased gradually during fruit development, comprising 69.61% and 18.32% of the fruit, respectively, during ripening. Conversely, the contents of soluble sugar and starch decreased gradually during fruit development, comprising 2.14% and 0.84%, respectively, during ripening. Transcriptome sequencing generated 40,631 unigenes across 9 cDNA libraries. We identified 51 and 25 candidate unigenes related to the biosynthesis of fatty acid and the biosynthesis of triacylglycerol (TAG), respectively. The expression levels of the genes encoding Acetyl-CoA carboxylase (ACCase), long-chain acyl-CoA synthetases (LACS), 3-oxoacyl-ACP synthase II (KASII), and glycerol-3-phosphate acyl transfer (GPAT) were upregulated at 60 DAP relative to the levels at 90 and 120 DAP, while the stearoyl-ACP-desaturase (<i>SAD</i>) and fatty acid desaturase 2 (<i>FAD2</i>) genes were highly abundantly expressed during all walnut developmental periods. We found that ABSCISIC ACID INSENSEITIVE3 (ABI3), WRINKLEDl (WRI1), LEAFY COTYLEDON1 (LEC1), and FUSCA3 (FUS3) may be key transcription factors involved in lipid synthesis. Additionally, the metabolomics analysis detected 706 metabolites derived from 18 samples, among which, 4 are implicated in the TAG synthesis, 2 in the glycolysis pathway, and 5 in the tricarboxylic acid cycle (TCA cycle) pathway. The combined analysis of the related genes and metabolites in TAG synthesis showed that phospholipid:diacylglycerol acyltransferase (<i>PDAT</i>) genes were highly abundantly expressed across walnut fruit developmental periods, and their downstream metabolite TAG gradually accumulated with the progression of fruit development. The <i>FAD2</i> gene showed consistently higher expression during fruit development, and its downstream metabolites 18:2-PC and 18:3-PC gradually accumulated. The <i>ACCase</i>, <i>LACS</i>, <i>SAD</i>, <i>FAD2</i>, and <i>PDAT</i> genes may be crucial genes required for walnut oil synthesis. Our data will enrich public databases and provide new insights into functional genes related to lipid metabolism in walnut. |
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| spelling | doaj.art-adc81f89b14243c3a39c011626ede3a72023-11-16T17:43:48ZengMDPI AGPlants2223-77472023-01-0112353810.3390/plants12030538Metabolomics and Transcriptomics Provide Insights into Lipid Biosynthesis in the Embryos of Walnut (<i>Juglans regia</i> L.)Manman Liang0Xuemei Zhang1Qinglong Dong2Han Li3Suping Guo4Haoan Luan5Peng Jia6Minsheng Yang7Guohui Qi8College of Forestry, Hebei Agricultural University, Baoding 071001, ChinaCollege of Forestry, Hebei Agricultural University, Baoding 071001, ChinaCollege of Forestry, Hebei Agricultural University, Baoding 071001, ChinaCollege of Forestry, Hebei Agricultural University, Baoding 071001, ChinaCollege of Forestry, Hebei Agricultural University, Baoding 071001, ChinaCollege of Forestry, Hebei Agricultural University, Baoding 071001, ChinaCollege of Forestry, Hebei Agricultural University, Baoding 071001, ChinaCollege of Forestry, Hebei Agricultural University, Baoding 071001, ChinaCollege of Forestry, Hebei Agricultural University, Baoding 071001, ChinaWalnut (<i>Juglans regia</i> L.) is an important woody oilseed tree species due to its commercial value. However, the regulation mechanism of walnut oil accumulation is still poorly understood, which restricted the breeding and genetic improvement of high-quality oil-bearing walnuts. In order to explore the metabolic mechanism that regulates the synthesis of walnut oil, we used transcriptome sequencing technology and metabolome technology to comprehensively analyze the key genes and metabolites involved in oil synthesis of the walnut embryo at 60, 90, and 120 days after pollination (DAP). The results showed that the oil and protein contents increased gradually during fruit development, comprising 69.61% and 18.32% of the fruit, respectively, during ripening. Conversely, the contents of soluble sugar and starch decreased gradually during fruit development, comprising 2.14% and 0.84%, respectively, during ripening. Transcriptome sequencing generated 40,631 unigenes across 9 cDNA libraries. We identified 51 and 25 candidate unigenes related to the biosynthesis of fatty acid and the biosynthesis of triacylglycerol (TAG), respectively. The expression levels of the genes encoding Acetyl-CoA carboxylase (ACCase), long-chain acyl-CoA synthetases (LACS), 3-oxoacyl-ACP synthase II (KASII), and glycerol-3-phosphate acyl transfer (GPAT) were upregulated at 60 DAP relative to the levels at 90 and 120 DAP, while the stearoyl-ACP-desaturase (<i>SAD</i>) and fatty acid desaturase 2 (<i>FAD2</i>) genes were highly abundantly expressed during all walnut developmental periods. We found that ABSCISIC ACID INSENSEITIVE3 (ABI3), WRINKLEDl (WRI1), LEAFY COTYLEDON1 (LEC1), and FUSCA3 (FUS3) may be key transcription factors involved in lipid synthesis. Additionally, the metabolomics analysis detected 706 metabolites derived from 18 samples, among which, 4 are implicated in the TAG synthesis, 2 in the glycolysis pathway, and 5 in the tricarboxylic acid cycle (TCA cycle) pathway. The combined analysis of the related genes and metabolites in TAG synthesis showed that phospholipid:diacylglycerol acyltransferase (<i>PDAT</i>) genes were highly abundantly expressed across walnut fruit developmental periods, and their downstream metabolite TAG gradually accumulated with the progression of fruit development. The <i>FAD2</i> gene showed consistently higher expression during fruit development, and its downstream metabolites 18:2-PC and 18:3-PC gradually accumulated. The <i>ACCase</i>, <i>LACS</i>, <i>SAD</i>, <i>FAD2</i>, and <i>PDAT</i> genes may be crucial genes required for walnut oil synthesis. Our data will enrich public databases and provide new insights into functional genes related to lipid metabolism in walnut.https://www.mdpi.com/2223-7747/12/3/538oil contentlipid biosynthesis<i>SAD</i>FAD2regulatory network |
| spellingShingle | Manman Liang Xuemei Zhang Qinglong Dong Han Li Suping Guo Haoan Luan Peng Jia Minsheng Yang Guohui Qi Metabolomics and Transcriptomics Provide Insights into Lipid Biosynthesis in the Embryos of Walnut (<i>Juglans regia</i> L.) Plants oil content lipid biosynthesis <i>SAD</i> FAD2 regulatory network |
| title | Metabolomics and Transcriptomics Provide Insights into Lipid Biosynthesis in the Embryos of Walnut (<i>Juglans regia</i> L.) |
| title_full | Metabolomics and Transcriptomics Provide Insights into Lipid Biosynthesis in the Embryos of Walnut (<i>Juglans regia</i> L.) |
| title_fullStr | Metabolomics and Transcriptomics Provide Insights into Lipid Biosynthesis in the Embryos of Walnut (<i>Juglans regia</i> L.) |
| title_full_unstemmed | Metabolomics and Transcriptomics Provide Insights into Lipid Biosynthesis in the Embryos of Walnut (<i>Juglans regia</i> L.) |
| title_short | Metabolomics and Transcriptomics Provide Insights into Lipid Biosynthesis in the Embryos of Walnut (<i>Juglans regia</i> L.) |
| title_sort | metabolomics and transcriptomics provide insights into lipid biosynthesis in the embryos of walnut i juglans regia i l |
| topic | oil content lipid biosynthesis <i>SAD</i> FAD2 regulatory network |
| url | https://www.mdpi.com/2223-7747/12/3/538 |
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