Abstract Alkali stress is an important limiting factor for agricultural production. The aim of this study was to investigate whether old and young leaves have different biochemical responses to alkali stress in hexaploid wheat, and to provide molecular dissection of these differential responses on the basis of proteomic profiling. Under alkali stress, hexaploid wheat accumulated higher concentrations of Na+ in older leaves to protect young leaves. Young leaves accumulated amino acids, carbohydrates, and dehydrin proteins to relieve Na+ toxicity. Under alkali stress, 14-3-3 protein abundance was enhanced in old leaves to accelerate Na+ compartmentation in the vacuole. Abundances of 27 ribosomal proteins were significantly decreased in old leaves but not in young leaves, and many proteinases and ribonucleases also were significantly upregulated by alkali stress in old leaves. Interestingly, one E3 ubiquitin-protein ligase, one ubiquitin protein, and one proteasome protein were simultaneously upregulated in old leaves but not in young leaves. We propose that during the response to alkali stress, old leaves may programmatically degrade ribosomes through the ubiquitin-proteasome pathway to generate amino acids, which will increase tissue tolerance. Alkali stress induced remarkable enhancement of almost all free amino acids and ribose contents in old leaves, thus supporting this hypothesis. In addition, we observed that, for some salinity-tolerant protein-triads, the A, B, and D homoeologous proteins showed different response to alkali stress. This suggests that alkali stress may influence the translation of homoeologous genes, resulting in imbalanced translation of A, B, and D homoeologous genes in some gene triads.

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六倍体小麦老叶和幼叶对碱胁迫的比较适应策略

摘要 碱胁迫是农业生产的重要限制因素。本研究的目的是研究老叶和幼叶是否对六倍体小麦的碱胁迫有不同的生化反应，并在蛋白质组学分析的基础上对这些不同的反应进行分子剖析。在碱胁迫下，六倍体小麦在老叶中积累了更高浓度的 Na+ 以保护幼叶。嫩叶积累氨基酸、碳水化合物和脱水蛋白，以减轻 Na+ 毒性。在碱胁迫下，老叶中 14-3-3 蛋白质丰度增加，以加速液泡中的 Na+ 区室。27 种核糖体蛋白的丰度在老叶中显着降低，但在幼叶中没有显着降低，许多蛋白酶和核糖核酸酶也受到老叶碱胁迫的显着上调。有趣的是，一种 E3 泛素蛋白连接酶、一种泛素蛋白和一种蛋白酶体蛋白在老叶中同时上调，但在幼叶中没有上调。我们提出，在对碱胁迫的反应过程中，老叶可能会通过泛素-蛋白酶体途径有程序地降解核糖体以产生氨基酸，这将增加组织耐受性。碱胁迫诱导了老叶中几乎所有游离氨基酸和核糖含量的显着增加，从而支持了这一假设。此外，我们观察到，对于一些耐盐蛋白三联体，A、B 和 D 同源蛋白对碱胁迫表现出不同的反应。