iTRAQ-based quantitative proteomic analysis reveals pathways associated with re-establishing desiccation tolerance in germinating seeds of Caragana korshinskii Kom.

Mature seeds of Caragana korshinskii Kom. lose desiccation tolerance (DT) during germination. However, DT can be re-induced by polyethylene glycol (PEG) or abscisic acid (ABA), and this provides a novel system to analyse the mechanism of DT. Although the global gene expression during the re-establishment of DT treated by PEG or ABA has been characterized, the changes in protein species abundance are still unknown. Here, we used an iTRAQ-based quantitative proteomics approach to perform a comparative analysis of protein abundances in germinated seeds of PEG-treated, ABA-treated and untreated radicles in response to the re-establishment of DT. A total of 3009 proteins were quantified; compared with the untreated samples, 274 and 261 differentially abundant protein species were found in PEG- and ABA-treated samples, respectively. The observed protein abundance patterns showed a clear overlap in seeds with ABA-and PEG-induced re-establishment of DT. During the re-establishment of DT, the expression of auxin-repressed protein and metallothionien-like protein was induced, and the content of proline increased significantly; however, proteins related to cell proliferation were found to be expressed at lower levels, and the glycolytic pathway was partially inhibited. These results provide promising insights into the molecular mechanisms underlying the re-establishment of DT in germinated seeds.

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The major challenge for seed storage is the complexity of the tolerance to desiccation. Re-establishment of desiccation tolerance (DT) in germinating seed as a model was used for DT researching. Although several researches have been focusing on the transcriptome of DT re-establishment, little proteomic information remained to be available. In the present study, the iTRAQ-based quantitative proteomic analysis was employed to identify the differentially accumulated protein species from radicles of germinating C. korshinskii seedling after ABA-, PEG- treatment or not. The data obtained not only provides basic information about proteome, but also characterize the quantitative changes that occur in the abundance of proteins species during DT re-establishment. These results are helpful understanding the mechanism of DT re-establishment induced by PEG or ABA.