Role of microRNAs in plant and animal development

Small RNAs, including microRNAs (miRNAs) and short interfering RNAs (siRNAs), are key components of an evolutionarily conserved system of RNA-based gene regulation in eukaryotes. They are involved in many molecular interactions, including defense against viruses and regulation of gene expression during development. miRNAs interfere with expression of messenger RNAs encoding factors that control developmental timing, stem cell maintenance, and other developmental and physiological processes in plants and animals. miRNAs are negative regulators that function as specificity determinants, or guides, within complexes that inhibit protein synthesis (animals) or promote degradation (plants) of mRNA targets.     

小分子microRNA及其生物学特征

MicroRNA(miRNA)是机体内源性表达的一类长20～24nt的非编码RNA调控因子,在动植物细胞中导致转录后基因沉默。近来发现miRNA家族成员众多,广泛地存在于各种真核细胞中,对诸如生长、发育、分化、死亡等生物过程进行调控。文章就其发现、形成及功能加以综述。     

Degradation of microRNAs by a family of exoribonucleases in Arabidopsis

microRNAs (miRNAs) play crucial roles in numerous developmental and metabolic processes in plants and animals. The steady-state levels of miRNAs need to be properly controlled to ensure normal development. Whereas the framework of miRNA biogenesis is established, factors involved in miRNA degradation remain unknown. Here, we show that a family of exoribonucleases encoded by the SMALL RNA DEGRADING NUCLEASE (SDN) genes degrades mature miRNAs in Arabidopsis. SDN1 acts specifically on single-stranded miRNAs in vitro and is sensitive to the 2'-O-methyl modification on the 3' terminal ribose of miRNAs. Simultaneous knockdown of three SDN genes in vivo results in elevated miRNA levels and pleiotropic developmental defects. Therefore, we have uncovered the enzymes that degrade miRNAs and demonstrated that miRNA turnover is crucial for plant development.     

miRNA-mediated gene silencing by translational repression followed by mRNA deadenylation and decay

microRNAs (miRNAs) regulate gene expression through translational repression and/or messenger RNA (mRNA) deadenylation and decay. Because translation, deadenylation, and decay are closely linked processes, it is important to establish their ordering and thus to define the molecular mechanism of silencing. We have investigated the kinetics of these events in miRNA-mediated gene silencing by using a Drosophila S2 cell-based controllable expression system and show that mRNAs with both natural and engineered 3' untranslated regions with miRNA target sites are first subject to translational inhibition, followed by effects on deadenylation and decay. We next used a natural translational elongation stall to show that miRNA-mediated silencing inhibits translation at an early step, potentially translation initiation.     

植物微小RNA（microRNA）研究进展

真核细胞中存在大量的非编码RNA,～22nt的小RNA是其中一类非常重要的调控RNA,主要包括siRNA和miRNA两种类型,二者均由类似RNaseⅢ的核酸内切酶一Dicer加工产生,随后进入沉默复合体抑制靶基因表达。miRNA分子与siRNA类似,但miRNA的前体在基因组上具有独立的转录单位,可自身折叠成发卡结构,其靶基因主要是与器官发生及生长发育相关的转录因子以及调控蛋白。miRNA在生物生长发育的各个时期都扮演着重要的角色,调控许多重要的生物途径,处于基因调控网络的核心位置。     

The TaFIM1 gene mediates wheat resistance against Puccinia striiformis f. sp. tritici and responds to abiotic stress

Fimbrin, a regulator of actin cytoskeletal dynamics that participates in numerous physiological and biochemical processes, controls multiple developmental processes in a variety of tissues and cell types. However, the role of fimbrin in pathogen defense of wheat and the mechanisms have not been well studied. Here, we investigated that the expression of TaFIM1 gene of wheat was significantly induced in response to avirulent race of Puccinia striiformis f. sp. tritici(Pst) and silencing of TaFIM1 by virus-induced gene silencing method. The results show that silencing of TaFIM1 resulted in a reduction of resistance against the stripe rust indicated by both phenotypes and a histological examination of Pst growth. Additionally, the expression level of Ta FIM1 gene was up-regulated under abiotic stresses. These findings suggest that Ta FIM1 functions as a positive regulator of pathogen resistance of wheat plants and response to abiotic stress. Our work may show new light on understanding the roles of fimbrin in wheat.     

miRNAs在植物色泽调控中的研究进展

色泽是影响植物外观品质及其商品价值的重要因素,目前关于植物色泽的研究主要集中于生理生化及转录水平上,而在转录后水平上报道较少。microRNA(miRNA)是一类在真核生物中广泛存在的非编码单链RNA分子,它可以通过对靶标mRNA的互补配对而降解或抑制m RNA的翻译,从而在转录后水平上对基因的表达进行负调控。简述了miRNA的作用机理,并对近几年miRNA在植物色泽调控中的研究进展进行了综述,以期为植物色泽在转录后水平上的调控奠定基础。     

Identification of virus-encoded microRNAs

RNA silencing processes are guided by small RNAs that are derived from double-stranded RNA. To probe for function of RNA silencing during infection of human cells by a DNA virus, we recorded the small RNA profile of cells infected by Epstein-Barr virus (EBV). We show that EBV expresses several microRNA (miRNA) genes. Given that miRNAs function in RNA silencing pathways either by targeting messenger RNAs for degradation or by repressing translation, we identified viral regulators of host and/or viral gene expression.     

人类Ago2蛋白与肿瘤的关系研究

Argonaute2 （Ago2）蛋白是RNA诱导沉默复合体（RNA-induced silencing complex、RISC）的核心元件,不仅在miRNA/siRNA通路中促使靶mRNA降解或抑制其蛋白质翻译,调节miRNAs生物合成和成熟,对生物生长发育、干细胞分化和肿瘤形成等有密切关系.     

新奇的调控分子——microRNA

microRNA(miRNA)是一类内源性表达的在转录后基因调控中发挥重要作用的小分子非编码RNA。在动植物细胞中,miRNA通过翻译抑制和靶mRNA去稳定性来调控靶基因,从而调控生长、发育、分化、死亡等生物过程。综述了miRNA的发现、形成、特点及调控机制。     

园艺植物 WRKY 基因功能研究进展

WRKY 转录因子是植物中特有的一类反式作用因子。WRKY 基因家族成员众多,是植物中最大的转录因子家族之一。目前,已在多种园艺植物中对该家族进行了全基因组鉴定。大量研究表明,WRKY 转录因子参与了植物中多种生物学过程,如营养剥夺、胚胎发生、种子发育、毛状体发育、叶片衰老及其他发育和激素调节的过程,是许多调控信号网络的重要组成部分。WRKY 转录因子还可参与植物适应各种逆境的转录调控,已被证明其在生物应激反应中发挥重要作用并参与植物的防御机制,其在植物防御病菌、病毒和虫害调控过程中的重要作用正被逐步揭示。此外,WRKY 转录因子在植物响应环境中非生物胁迫方面的作用也被不断解析,其可参与调控植物对干旱、温度、盐及渗透的响应,并在此过程中发挥正向或负向调节作用。本文基于近年来的相关研究成果,重点综述了 WRKY 转录因子在园艺植物生长发育、胁迫响应和代谢合成方面所发挥的作用和调控机理,进一步明确园艺植物 WRKY 转录因子的重要生物学功能,阐明 WRKY 转录因子介导的转录调控网络,为园艺植物优良性状相关的遗传资源挖掘和分子育种提供理论支撑。     

小果野蕉microRNAs及其靶基因的生物信息学预测

通过基于表达序列标签（EST）、基因组勘测序列（GSS）和高通量测序基因组序列（HTGS）的同源序列比对搜索,以及一系列的标准筛选,最终预测到属于8个家族的10条小果野蕉miRNAs。在线软件psRNATarget预测到24对miRNAs与靶基因的互作,这些靶基因主要参与小果野蕉的新陈代谢、生长发育以及胁迫响应等过程。