Cold acclimation and vegetative/reproductive transition are two important evolutionary adaptive mechanisms for winter wheat surviving the freezing temperature in winter and successful seeds setting in the next year. MicroRNA (miRNA) is a class of regulatory small RNAs (sRNAs), which plays critical roles in the growth and development of plants. However, the regulation mechanism of miRNAs during cold acclimation and vegetative/reproductive transition of winter wheat is not much understood. In this study, four sRNA libraries from leaves of winter wheat grown in the field at the three-leaf stage, winter dormancy stage, spring green-up stage, and jointing stage were analyzed to identify known and novel miRNAs and to understand their potential roles in the growth and development of winter wheat. We examined miRNA expression using a high-throughput sequencing technique. A total of 373 known, 55 novel, and 27 putative novel miRNAs were identified. Ninety-one miRNAs were found to be differentially expressed at the four stages. Among them, the expression of six known and eight novel miRNAs was significantly suppressed at the winter dormancy stage, whereas the expression levels of seven known and eight novel miRNAs were induced at this stage; three known miRNAs and three novel miRNAs were significantly induced at the spring green-up stage; six known miRNAs were induced at the spring green-up stage and reached the highest expression level at the jointing stage; and 20 known miRNAs and 10 novel miRNAs were significantly induced at the jointing stage. Expression of a number of representative differentially expressed miRNAs was verified using quantitative real-time polymerase chain reaction (qRT-PCR). Potential target genes for known and novel miRNAs were predicted. Moreover, six novel target genes for four Pooideae species-specific miRNAs and two novel miRNAs were verified using the RNA ligase-mediated 5′-rapid amplification of cDNA ends (RLM-5’RACE) technique. These results indicate that miRNAs are key non-coding regulatory factors modulating the growth and development of wheat. Our study provides valuable information for in-depth understanding of the regulatory mechanism of miRNAs in cold acclimation and vegetative/reproductive transition of winter wheat grown in the field.

基于高通量测序的RNA-Seq广泛被用于检测组织和细胞中基因的表达和调控机理研究,然而已有的文献表明mRNA水平并不能反映蛋白质的丰度,而研究正在翻译的mRNA的翻译组则比转录组更能反映蛋白组的实际水平,因此翻译组研究比转录组研究更具有理论和实践意义.对翻译组研究最为经典的多聚核糖体图谱技术到最近发展起来的核糖体图谱技术、核糖体亲和纯化技术以及翻译谱分析技术进行了综述比较,并介绍了翻译组研究前景,以便为翻译组研究提供参考.

BACKGROUND:Soil salinity is one of the primary causes of yield decline in rice. Pokkali (Pok) is a highly salt-tolerant landrace, whereas IR29 is a salt-sensitive but widely cultivated genotype. Comparative analysis of these genotypes may offer a better understanding of the salinity tolerance mechanisms in rice. Although most stress-responsive genes are regulated at the transcriptional level, in many cases, changes at the transcriptional level are not always accompanied with the changes in protein abundance, which suggests that the transcriptome needs to be studied in conjunction with the proteome to link the phenotype of stress tolerance or sensitivity. Published reports have largely underscored the importance of transcriptional regulation during salt stress in these genotypes, but the regulation at the translational level has been rarely studied. Using RNA-Seq, we simultaneously analyzed the transcriptome and translatome from control and salt-exposed Pok and IR29 seedlings to unravel molecular insights into gene regulatory mechanisms that differ between these genotypes.RESULTS:Clear differences were evident at both transcriptional and translational levels between the two genotypes even under the control condition. In response to salt stress, 57 differentially expressed genes (DEGs) were commonly upregulated at both transcriptional and translational levels in both genotypes; the overall number of up/downregulated DEGs in IR29 was comparable at both transcriptional and translational levels, whereas in Pok, the number of upregulated DEGs was considerably higher at the translational level (544 DEGs) than at the transcriptional level (219 DEGs); in contrast, the number of downregulated DEGs (58) was significantly less at the translational level than at the transcriptional level (397 DEGs). These results imply that Pok stabilizes mRNAs and also efficiently loads mRNAs onto polysomes for translation during salt stress.CONCLUSION:Under salt stress, Pok is more efficient in maintaining cell wall integrity, detoxifying reactive oxygen species (ROS), translocating molecules and maintaining photosynthesis. The present study confirmed the known salt stress-associated genes and also identified a number of putative new salt-responsive genes. Most importantly, the study revealed that the translational regulation under salinity plays an important role in salt-tolerant Pok, but such regulation was less evident in the salt-sensitive IR29.

MicroRNA(miRNA)是真核生物中具有重要调控功能的一类小分子RNA.植物miRNA通过碱基互补配对方式引导RNA沉默复合体识别靶基因并介导靶基因mRNA被剪切或蛋白质翻译被抑制,所以对植物miRNA靶基因的分析和验证是研究miRNA功能必不可少的一部分.植物miR-NA靶基因可通过生物信息学方法预测,主要根据miRNA与mRNA的互补程度进行,然而理论上预测的靶基因尚有待于进一步的试验验证.简要介绍了植物miRNA产生过程的最新研究进展以及靶基因的预测方法,重点综述了植物miRNA靶基因的验证方法,包括RLM-5′RACE、降解组测序、瞬时共表达和转基因系统,为更深入地研究植物miRNA介导的调控机制提供参考.