植物转基因沉默与病毒抗性

对植物基因沉默的机制及其在植物抗病毒基因工程中的应用作了综述 .植物转基因沉默是转基因植株中普遍发生的一种现象 ,引起植物转基因沉默的原因是多方面的 ,但主要涉及转录水平的基因沉默和转录后水平的基因沉默 .

DNA甲基化与植物转基因沉默研究进展

基因沉默现象已成为转基因植物商品化生产的严重阻碍。本文就DNA甲基化的作用机制及由其引起转基因沉默的研究作了简要综述。另外 ,结合基因表达的抑制因素 ,对如何消除DNA甲基化 ,促使外源基因高效表达的策略进行了初步探讨。

植物基因工程中的转基因沉默机制

植物转基因沉默可以发生在染色体DNA、转录和转录后三种不同的层次上，转录水平基因沉默机制涉及DNA甲基化、位置效应、重复序列、同源序列等作用。转录后水平基因沉默机制常用RNA域值模型、异常RNA模型、双链RNA模型、未成熟翻译终止模型等解释。目前没有一种通用的模型可以解释所有的转基因沉默现象，但不同模型从不同方面解释了转基因机制的某些方面。

植物RNAi的特点及其应用研究进展

RNAi是真核生物中普遍存在的抵抗病毒复制表达、抑制转座子转座及调控基因表达的监控机制。清楚植物体内的RNAi途径,将对认识植物基因组功能和转基因研究工作具有积极意义。就国内外与植物RNAi有关的研究作了综述,重点介绍了植物RNAi特征和该技术在植物基因工程中的应用。

SlMYC2转录因子对番茄伤害诱导抗性相关基因的调控研究

MYC2作为茉莉酸信号途径中一个重要的转录因子,在调控植物对昆虫取食和腐生型病原菌的抗性反应中发挥重要作用。但迄今为止,在番茄中仍未有关于SlMYC2突变体(或SlMYC2沉默转基因植物)的报道。在改造pCAMBIA1301表达载体的基础上,利用RNAi方法构建SlMYC2沉默的转基因植物。利用荧光定量PCR方法,证明这些转基因植物中SlMYC2表达量显著下降,达到沉默SlMYC2的目的。通过检测SlMYC2-RNAi转基因植物中伤害诱导标记基因的表达情况,发现SlMYC2-RNAi转基因植物中伤害诱导的早期响应基因和晚期响应基因的表达都受到明显抑制,结果表明SlMYC2转录因子在调控番茄伤害诱导相关抗性基因的表达中发挥重要作用。

Features,Mechanisms and Applies of Post-transcriptional Gene Silencing in Transgenic Plants

Since transgene silencing was found in transgenic plants,many scholars have studied it extensively and considered that it has three functional mechanisms:post dependent gene silencing,transcriptional gene silencing,post transcriptional gene silencing.At the moment,people have mainly focused on the study of post transcriptional gene silencing and found its features:extensivity,conduction and peculiarity,also put forward some hypothesis for its mechanisms,for example,RNA threshold model,aberrant RNA model,inter or intra molecular base pairing model and so on.Furthermore,post transcriptional gene silencing is being applied in gene engineering of plants.Recently the people have found that post transcriptional gene silencing has bearing on capacity plants resisting virus.Many researchers have studied post transcriptional gene silencing,but there are some questions which need be solved in the future.This article summarizes progresses in features,mechanisms,applies of post transcriptional gene silencing about transgenic plants.

Cumulus-specific genes are transcriptionally silent following somatic cell nuclear transfer in a mouse model

This study investigated whether four cumulus-specific genes: follicular stimulating hormone receptor (FSHr), hyaluronan synthase 2 (Has2), prostaglandin synthase 2 (Ptgs2) and steroidogenic acute regulator protein (Star), were correctly reprogrammed to be transcriptionally silent following somatic cell nuclear transfer (SCNT) in a murine model. Cumulus cells of C57×CBA F1 female mouse were injected into enucleated oocytes, followed by activation in 10 μmol/L strontium chloride for 5 h and subsequent in vitro culture up to the blastocyst stage. Expression of cumulus-specific genes in SCNT-derived embryos at 2-cell, 4-cell and day 4.5 blastocyst stages was compared with corresponding in vivo fertilized embryos by real-time PCR. It was demonstrated that immediately after the first cell cycle, SCNT-derived 2-cell stage embryos did not express all four cumulus-specific genes, which continually remained silent at the 4-cell and blastocyst stages. It is therefore concluded that all four cumulus-specific genes were correctly reprogrammed to be silent following nuclear transfer with cumulus donor cells in the mouse model. This would imply that the poor preimplantation developmental competence of SCNT embryos derived from cumulus cells is due to incomplete reprogramming of other embryonic genes, rather than cumulus-specific genes.

小麦对小麦孢囊线虫抗病性研究进展

由小麦孢囊线虫引起的小麦孢囊线虫病发生分布范围广,防治困难,严重危害我国小麦生产。在我国危害小麦的孢囊线虫主要包括禾谷孢囊线虫(Heterodera avenae)和菲利普孢囊线虫(H.filipjevi)。种植抗病小麦品种是防治小麦孢囊线虫病最经济有效的措施,近10年来,我国科学家制定了小麦孢囊线虫抗性评价标准,测试了我国主推小麦品种和部分引进种质资源对小麦孢囊线虫的抗感性,鉴定到太空6号、新麦11、VP1620和Madsen等抗小麦孢囊线虫的优良材料,利用抗源创制了一系列的抗小麦孢囊线虫种质材料,从组织细胞学、基因组和转录组等解析了小麦抗孢囊线虫的机制。本文主要从小麦孢囊线虫致病型分化、抗性评价、抗性基因鉴定、抗性机制解析和抗病基因利用等方面进行综述。

Post-transcriptional gene silencing in plants： a double-edged sword

In plants, post-transcriptional gene silencing(PTGS) protects the genome from foreign genes and restricts the expression of certain endogenous genes for proper development. Here, we review the recent progress about how the unwanted PTGS is avoided in plants. As a decision-making step of PTGS, aberrant transcripts from most endogenous coding genes are strictly sorted to the bidirectional RNA decay pathways in cytoplasm but not to the short interference RNA(si RNA)-mediated PTGS, with the exception of a few development-relevant endogenous si RNA-producing genes. We also discuss a finely balanced PTGS threshold model that plants fully take advantage of the power of PTGS without self-harm.

Viral suppression of RNA silencing

Gene silencing (RNA silencing) plays a fundamental role in antiviral defense in plants, fungi and invertebrates. Viruses encode proteins that suppress gene silencing to counter host defense. Viral suppressors of RNA silencing (VSRs) have been identified from almost all plant virus genera and some viruses of insects and mammals. Recent studies have revealed that VSRs counter host defense and interfere with host gene regulation by interacting with RNA or important components of the RNA silencing pathway. Here, we review the current understanding of the complex mechanisms of VSRs that have been revealed by recent studies.

Virus-induced gene silencing and its application in plant functional genomics

Virus-induced gene silencing is regarded as a powerful and efficient tool for the analysis of gene function in plants because it is simple, rapid and transformation-free. It has been used to perform both forward and reverse genetics to identify plant functional genes. Many viruses have been developed into virus-induced gene silencing vectors and gene functions involved in development, biotic and abiotic stresses, metabolism, and cellular signaling have been reported. In this review, we discuss the development and application of virus-induced gene silencing in plant functional genomics.