School of Biotechnology and Environmental Engineering, Myongji University, Yongin 449-728, Korea.
Plant Physiol. 2012 Jul;159(3):1111-24. doi: 10.1104/pp.112.194928. Epub 2012 May 7.
Abiotic stress, including drought, salinity, and temperature extremes, regulates gene expression at the transcriptional and posttranscriptional levels. Expression profiling of total messenger RNAs (mRNAs) from rice (Oryza sativa) leaves grown under stress conditions revealed that the transcript levels of photosynthetic genes are reduced more rapidly than others, a phenomenon referred to as stress-induced mRNA decay (SMD). By comparing RNA polymerase II engagement with the steady-state mRNA level, we show here that SMD is a posttranscriptional event. The SMD of photosynthetic genes was further verified by measuring the half-lives of the small subunit of Rubisco (RbcS1) and Chlorophyll a/b-Binding Protein1 (Cab1) mRNAs during stress conditions in the presence of the transcription inhibitor cordycepin. To discern any correlation between SMD and the process of translation, changes in total and polysome-associated mRNA levels after stress were measured. Total and polysome-associated mRNA levels of two photosynthetic (RbcS1 and Cab1) and two stress-inducible (Dehydration Stress-Inducible Protein1 and Salt-Induced Protein) genes were found to be markedly similar. This demonstrated the importance of polysome association for transcript stability under stress conditions. Microarray experiments performed on total and polysomal mRNAs indicate that approximately half of all mRNAs that undergo SMD remain polysome associated during stress treatments. To delineate the functional determinant(s) of mRNAs responsible for SMD, the RbcS1 and Cab1 transcripts were dissected into several components. The expressions of different combinations of the mRNA components were analyzed under stress conditions, revealing that both 3' and 5' untranslated regions are necessary for SMD. Our results, therefore, suggest that the posttranscriptional control of photosynthetic mRNA decay under stress conditions requires both 3' and 5' untranslated regions and correlates with differential polysome association.
非生物胁迫，包括干旱、盐度和极端温度，在转录和转录后水平上调节基因表达。对在胁迫条件下生长的水稻（Oryza sativa）叶片中总信使 RNA（mRNA）的表达谱进行分析表明，与其他基因相比，光合作用基因的转录水平下降得更快，这种现象被称为胁迫诱导的 mRNA 衰减（SMD）。通过比较 RNA 聚合酶 II 与稳态 mRNA 水平的结合，我们在这里表明 SMD 是一个转录后事件。通过在 cordycepin 存在的情况下测量胁迫条件下 Rubisco（RbcS1）小亚基和叶绿素 a/b-结合蛋白 1（Cab1）mRNA 的半衰期，进一步验证了光合作用基因的 SMD。为了辨别 SMD 与翻译过程之间的任何相关性，在胁迫后测量了总 mRNA 和多核糖体相关 mRNA 水平的变化。在胁迫后，两种光合作用（RbcS1 和 Cab1）和两种应激诱导（脱水应激诱导蛋白 1 和盐诱导蛋白）基因的总 mRNA 和多核糖体相关 mRNA 水平均发生明显变化。这表明在胁迫条件下，多核糖体相关对于转录本稳定性很重要。对总 mRNA 和多核糖体 mRNA 进行的微阵列实验表明，在 SMD 过程中，大约一半的 mRNA 仍然与多核糖体相关。为了描绘负责 SMD 的 mRNA 的功能决定因素，将 RbcS1 和 Cab1 转录物分解成几个组成部分。在胁迫条件下分析不同组合的 mRNA 成分的表达，结果表明 3' 和 5' 非翻译区对于 SMD 都是必需的。因此，我们的研究结果表明，胁迫条件下光合作用 mRNA 衰减的转录后控制需要 3' 和 5' 非翻译区，并与差异多核糖体相关联。
