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Metabolomics reveals significant variations in metabolites and correlations regarding the maturation of walnuts (Juglans regia L.).

Rao G, Sui J, Zhang J - Biol Open (2016)

Bottom Line: PCA scores revealed that the metabolic compositions of the embryo are different at each stage, while the metabolic composition of the endotesta could not be significantly separated into distinct groups.Additionally, 7225 metabolite-metabolite correlations were detected in walnut kernel by a Pearson correlation coefficient approach; during screening of the calculated correlations, 463 and 1047 were determined to be significant with r(2)≥0.49 and had a false discovery rate (FDR) ≤0.05 in endotesta and embryo, respectively.This work provides the first comprehensive metabolomic study of walnut kernels and reveals that most of the carbohydrate and protein-derived carbon was transferred into other compounds, such as fatty acids, during the maturation of walnuts, which may potentially provide the basis for further studies on walnut kernel metabolism.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Tree Genetics and Breeding, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, Republic of China Collaborative Innovation Center of Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, Republic of China Key Laboratory of Tree Breeding and Cultivation, State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, Republic of China.

No MeSH data available.


Relative abundance of carbohydrates in endotesta and embryo of walnut kernels. Bar graph shows the normalized abundance of carbohydrates in endotesta (P) and embryo (R) at different development time points (T1-T5). Data represented as mean±s.d.
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BIO017863F6: Relative abundance of carbohydrates in endotesta and embryo of walnut kernels. Bar graph shows the normalized abundance of carbohydrates in endotesta (P) and embryo (R) at different development time points (T1-T5). Data represented as mean±s.d.

Mentions: The levels of carbohydrates were higher and relatively stable in endotesta, while they were more dynamic during the kernel development in embryo (Fig. 6). Glucose and cellobiose were predominant during the walnut kernel development; the difference between these two carbohydrates was that the level of glucose was continuously decreasing while cellobiose increased to a high and stable level during kernel ripening. The reverse content changing between these two carbohydrates supports the carbon flow into cellobiose from glucose. Glucose is an energy source that plays an important role in the respiration of several plant tissues. In endotesta the levels of glucose were stable during development, suggesting that there is a balance between the glucose consumed and synthesized. Meanwhile, the glucose levels at the early stage were much higher than in the later stages in the embryos, suggesting that the glucose was mainly consumed as an energy source for respiration and metabolic synthesis. Cellobiose can be obtained by enzymatic or acidic hydrolysis of cellulose and cellulose rich materials, suggesting that the main carbohydrate of the ripe walnut kernel is cellulose. In higher plants, cell morphogenesis and anisotropic growth were mediated by a cellulose biosynthesis process which played a vital role to support the structural framework of the plant cell wall (Mendu et al., 2011). Cellulose also has been considered to have the key role to strengthen the secondary cell wall, which protects the embryo during seed development (Stork et al., 2010). Cellulose is also protects the seed from damage in the environment by seed mucilage that surrounds the seed (Arsovski et al., 2010). The dynamic upregulation of cellulose both in endotesta and embryo of walnut kernel suggests that cellulose plays an important role in carbohydrate metabolism during kernel development. Another two carbohydrates, gulose and fructose, have the same dynamic changing model as glucose; both of them were consumed at the early stage from a relative high level in embryos, indicating that these two carbohydrates are essential for the development of embryos at the early stage either by providing energy sources or as a chemical structure of enzymes.Fig. 6.


Metabolomics reveals significant variations in metabolites and correlations regarding the maturation of walnuts (Juglans regia L.).

Rao G, Sui J, Zhang J - Biol Open (2016)

Relative abundance of carbohydrates in endotesta and embryo of walnut kernels. Bar graph shows the normalized abundance of carbohydrates in endotesta (P) and embryo (R) at different development time points (T1-T5). Data represented as mean±s.d.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4920193&req=5

BIO017863F6: Relative abundance of carbohydrates in endotesta and embryo of walnut kernels. Bar graph shows the normalized abundance of carbohydrates in endotesta (P) and embryo (R) at different development time points (T1-T5). Data represented as mean±s.d.
Mentions: The levels of carbohydrates were higher and relatively stable in endotesta, while they were more dynamic during the kernel development in embryo (Fig. 6). Glucose and cellobiose were predominant during the walnut kernel development; the difference between these two carbohydrates was that the level of glucose was continuously decreasing while cellobiose increased to a high and stable level during kernel ripening. The reverse content changing between these two carbohydrates supports the carbon flow into cellobiose from glucose. Glucose is an energy source that plays an important role in the respiration of several plant tissues. In endotesta the levels of glucose were stable during development, suggesting that there is a balance between the glucose consumed and synthesized. Meanwhile, the glucose levels at the early stage were much higher than in the later stages in the embryos, suggesting that the glucose was mainly consumed as an energy source for respiration and metabolic synthesis. Cellobiose can be obtained by enzymatic or acidic hydrolysis of cellulose and cellulose rich materials, suggesting that the main carbohydrate of the ripe walnut kernel is cellulose. In higher plants, cell morphogenesis and anisotropic growth were mediated by a cellulose biosynthesis process which played a vital role to support the structural framework of the plant cell wall (Mendu et al., 2011). Cellulose also has been considered to have the key role to strengthen the secondary cell wall, which protects the embryo during seed development (Stork et al., 2010). Cellulose is also protects the seed from damage in the environment by seed mucilage that surrounds the seed (Arsovski et al., 2010). The dynamic upregulation of cellulose both in endotesta and embryo of walnut kernel suggests that cellulose plays an important role in carbohydrate metabolism during kernel development. Another two carbohydrates, gulose and fructose, have the same dynamic changing model as glucose; both of them were consumed at the early stage from a relative high level in embryos, indicating that these two carbohydrates are essential for the development of embryos at the early stage either by providing energy sources or as a chemical structure of enzymes.Fig. 6.

Bottom Line: PCA scores revealed that the metabolic compositions of the embryo are different at each stage, while the metabolic composition of the endotesta could not be significantly separated into distinct groups.Additionally, 7225 metabolite-metabolite correlations were detected in walnut kernel by a Pearson correlation coefficient approach; during screening of the calculated correlations, 463 and 1047 were determined to be significant with r(2)≥0.49 and had a false discovery rate (FDR) ≤0.05 in endotesta and embryo, respectively.This work provides the first comprehensive metabolomic study of walnut kernels and reveals that most of the carbohydrate and protein-derived carbon was transferred into other compounds, such as fatty acids, during the maturation of walnuts, which may potentially provide the basis for further studies on walnut kernel metabolism.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Tree Genetics and Breeding, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, Republic of China Collaborative Innovation Center of Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, Republic of China Key Laboratory of Tree Breeding and Cultivation, State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, Republic of China.

No MeSH data available.