Institute of Molecular Biology, National Chung Hsing University, Taichung, Taiwan.
Rapid Commun Mass Spectrom. 2012 Aug 15;26(15):1649-60. doi: 10.1002/rcm.6271.
Ubiquitination of proteins plays an important role in regulating a myriad of physiological functions in plants such as xylogenesis, senescence, cell cycle control, and stress response. However, only a limited number of proteins in plants have been identified as being ubiquitinated in response to salt stress. The relationships between ubiquitination and salt-stress responses in plants are not clear.
Rice (Oryza sativa) seedlings from the same genetic background with various salt tolerances exposed to salt stress were studied. The proteins of roots were extracted then analyzed using western blotting against ubiquitin. Differentially expressed ubiquitinated proteins were identified by nanospray liquid chromatography/tandem mass spectrometry (nano-LC/MS/MS) and quantified by label-free methods based on the Exponentially Modified Protein Abundance Index (emPAI) and on the peak areas of XIC spectra derived from ubiquitinated peptides. In addition, we performed a gel-based shotgun proteomic analysis to detect the ubiquitinated proteome that may be involved in response to salt stress.
The expressions of ubiquitination on pyruvate phosphate dikinase 1, heat shock protein 81-1, probable aldehyde oxidase 3, plasma membrane ATPase, cellulose synthase A catalytic subunit 4 [UDP-forming] and cyclin-C1-1 were identified and compared before and after salt treatment. The functions of those ubiquitinated proteins were further discussed for defence against salt stress. In addition, a large number of ubiquitinated proteins were successfully identified as well in this study.
The ubiquitination of proteins affected the protective mechanisms in rice seedlings to resist the salt stress during the initial phase. The findings in the present study also demonstrate that the regulated mechanisms through protein ubiquitination are important for rice seedlings against salt stress.
蛋白质的泛素化在调节植物的许多生理功能中起着重要作用，如木质部形成、衰老、细胞周期控制和应激反应。然而，只有少数植物蛋白被鉴定为对盐胁迫有泛素化反应。植物中泛素化与盐胁迫反应之间的关系尚不清楚。
研究了具有不同耐盐性的同一遗传背景的水稻（Oryza sativa）幼苗在盐胁迫下的情况。提取根部蛋白质，然后用针对泛素的 Western blot 进行分析。通过纳米喷雾液相色谱/串联质谱（nano-LC/MS/MS）鉴定差异表达的泛素化蛋白，并通过基于指数修饰蛋白丰度指数（emPAI）和来自泛素化肽的 XIC 谱峰面积的无标记方法进行定量。此外，我们还进行了基于凝胶的Shotgun 蛋白质组学分析，以检测可能参与应对盐胁迫的泛素化蛋白质组。
鉴定并比较了丙酮酸磷酸二激酶 1、热休克蛋白 81-1、醛氧化酶 3、质膜 ATP 酶、纤维素合酶 A 催化亚基 4 [UDP 形成]和细胞周期蛋白-C1-1 在盐处理前后的泛素化表达。进一步讨论了这些泛素化蛋白的功能，以防御盐胁迫。此外，本研究还成功鉴定了大量的泛素化蛋白。
蛋白质的泛素化影响了水稻幼苗在初始阶段抵抗盐胁迫的保护机制。本研究的结果还表明，通过蛋白质泛素化调节的机制对水稻幼苗抵抗盐胁迫非常重要。
