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College of Forest Resources and Environmental Science


Triploid poplar trees have been shown to have a number of growth advantages, especially much bigger leaves that contribute greatly to the increased biomass. In this study, we focused on the relationships between leaf age and leaf metabolism in triploids. We performed comparative proteomic analysis of the 5th (FDR5), 10th (FDR10), and 25th (FDR25) leaves from the apical meristems in allotriploids originated from first-division restitution (FDR). A total of 1970, 1916, and 1850 proteins were identified in the FDR5, FDR10, and FDR25, respectively. Principle component analysis (PCA) and differentially accumulated protein (DAP) analysis showed that FDR10 and FDR25 displayed higher similarities of protein accumulation patterns as compared to FDR5. MapMan enrichment analysis showed that several primary metabolic pathways or processes were significantly enriched in the DAPs. For example, photosynthesis, major CHO metabolism, glycolysis, N metabolism, redox, C1-metabolism, DNA, and protein turnover were significantly altered in both FDR10 and FDR25 compared with FDR5. In addition, amino acid metabolism and gluconeogenesis/glyoxylate cycle also underwent significant changes in FDR25 compared with FDR5. However, only amino acid metabolism was significantly enriched in the DAPs between FDR25 and FDR10. Further, DAP accumulation pattern analysis implied that FDR5, FDR10, and FDR25 were placed in the young, mature, and primary senescence stages of leaves. The most DAPs involved in the light reaction, photorespiration, Calvin cycle, starch and sucrose metabolism, pentose phosphate pathway (OPP), tricarboxylic acid (TCA) cycle, N metabolism, and C1-metabolism displayed higher accumulation in both FDR10 and FDR25 compared to FDR5. However, the most DAPs that are involved in cell wall and lipid metabolism, tetrapyrrole synthesis, nucleotide metabolism exhibited lower accumulation in both FDR10 and FDR25. Almost all DAPs between FDR-10 and FDR-25 showed a dramatic decrease in FDR25. KEGG enrichment analysis showed that carbon metabolism was altered significantly at different leaf ages. DAPs that are involved in carbon metabolism were predicted as different points in protein–protein interaction (PPI) networks from the STRING database. Finally, inconsistent transcript and protein abundance was found for DAPs, indicating the presence of posttranscriptional regulation during leaf-age progression process.

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© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( Publisher’s version of record:

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Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


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