重要的种子储存物质长寿命mRNA

Indispensable Material for Germination:Long-lived mRNAs of Plant Seed

高等植物通常从种子萌发开始,经过营养生长和生殖发育后重新形成种子,由此完成世代更迭。种子中积累的碳水化合物、脂质、蛋白质及mRNA等大分子物质对于维持其发芽潜力至关重要,其中部分mRNA可长期保存而不被降解,被称为长寿命mRNA (即long-lived mRNA)。在水稻(Oryza sativa)中,与萌发相关的long-lived mRNA在花后10–20天开始转录积累,花后20天至种子完全成熟期间,一些与休眠和胁迫响应相关的long-livedmRNA转录并保存在细胞中。Long-lived mRNA种类繁多,主要包括蛋白质合成类mRNA、能量代谢类mRNA、细胞骨架类mRNA及逆境响应相关的mRNA,如小热激蛋白和LEA家族蛋白。Long-livedmRNA的转录组分析表明,很多基因的启动子区域都包含脱落酸(ABA)或赤霉素(GA)相关的顺式作用元件,拟南芥(Arabidopsisthaliana)atabi5突变体种子中约有500个不同于野生型的差异表达long-lived mRNA,暗示ABA和GA是影响long-livedmRNA种类的关键激素。Long-livedmRNA通常与单核糖体和RBP蛋白交联在一起,以PBs (P-bodies)形式存在于细胞中,保护mRNA不被降解。与种子休眠相关的long-lived mRNA在种子后熟过程中逐渐被降解,而且一些特定long-lived mRNA的氧化修饰是种子打破休眠的一种生物现象。在种子长期贮藏过程中, long-lived mRNA的随机降解直接关系到种子的寿命和活力,保留下来的mRNA在种子吸胀初期被翻译成蛋白质,促进种子在吸胀早期快速萌发。该文综述了种子重要储存物质long-livedmRNA的特征和功能,并提出了本领域需要进一步研究的科学问题,以期为深入理解种子休眠、萌发与寿命的分子机制提供参考。

Higher plants usually start from seed germination and re-form seeds after vegetative growth and reproductive development,thus completing the life cycle.Carbohydrates,lipids,proteins,mRNA and other macromolecular substances accumulated in seeds are crucial to maintain the germination potential of seeds,some of mRNA can be preserved for a long time without degradation,known as long-lived mRNA.In rice,long-lived mRNA associated with germination began to be transcribed and accumulated 10 to 20 days after flowering,and some long-lived mRNA associated with dormancy and stress response were transcribed and preserved in cells from 20 days after flowering to seed maturity.There are many kinds of long-lived mRNA,mainly including some protein synthesis mRNA,energy metabolism mRNA,cytoskeleton mRNA and some stress response related mRNA,such as small heat shock protein,LEA(late embryogenesis abundant)family proteins.Transcriptomic analysis found that the promoter regions of many genes contain ABA-or GA-associated cis-acting elements,and there are about 500 differentially expressed long-lived mRNAs in the Arabidopsis atabi5(ABA-insensitive 5)mutant seeds that differ from the wild type,suggesting that abscisic acid(ABA)and gibberellin(GA)are the key hormones that influence the type of long-lived mRNA.Long-lived mRNAs are usually cross-linked with a single ribosome,RNA binding protein,which exists in cells in the form of P-bodies(PBs)to protect the mRNA from degradation.However,long-lived mRNAs associated with seed dormancy are gradually degraded during seed post-ripening,and the oxidative modification of some specific long-lived mRNAs is also a biological phenomenon to break seed dormancy.During the long-term storage of seeds,the random degradation of long-lived mRNA is directly related to the life and vitality of seeds,and the retained mRNA is translated into protein to help the rapid germination of seeds in the early stage of imbibition.In this paper,the characteristics and functions of long-lived mRNA are reviewed,and some future scientific issues are discussed to provide a reference for further understanding of the molecular mechanisms of seed dormancy,germination and longevity.