植物转基因沉默

转基因沉默分为两种水平:第一种是转录水平上的基因沉默,发生原因主要是位置效应、异染色质化以及甲基化;第二种是转录后水平上的基因沉默,发生原因是通过对靶标RNA进行特异性降解而使基因失活,并就此研究提出RNA阈值模型、异常RAN模型、分子间(内)配对模型与RNA干涉模型来解释这种现象产生的机制。     

RNA干涉技术

RNAi是双链RNA介导的、序列特异性的转录后基因沉默，自1998年发现至今已有很大进展。本文综述了RNA干涉的分子机理及其应用研究进展。     

基因沉默及其生理学意义

基因沉默包括转录水平上的基因沉默和转录后水平上的基因沉默。发生沉默的基因可以是外源性转移基因,也可以是入侵的病毒或宿主内源性基因。双链RNA(dsRNA)作为启动因素或中间体为不同生物基因沉默所共有。基因沉默是生物体在基因调控水平上的一种自我保护机制。通过基因沉默,可以限制外来核酸的入侵;同时,基因沉默还与生物的生长发育有关。     

Understanding silence: an investigation of the processes of silencing in parent–teacher conferences with Somali diaspora parents in Danish public schools

This article questions the dominant understanding that immigrant and refugee parents in parent–teacher conferences are silent because they come from a culture where one does not question the authority of the teacher. Instead, it is argued that they become silent through certain interactional processes. Building on material from an explorative case study of the home–school relations of Somali diaspora families in Danish public schools, the article argues that while these parents have many opinions about their children’s education that they wish to convey, there are institutional and interactional processes in the parent–teacher conference that systematically silence their voices. The understanding of culture as a stable structure that persons are situated within in a top-down manner is thus challenged, arguing that dynamic here-and-now interactions unfolding in a specific practice result in persons becoming, rather than being, silent.     

Silencing and freedom of speech in UK higher education

Freedom of speech in universities is currently an issue of widespread concern and debate. Recent empirical findings in the UK shed some light on whether speech is unduly restricted in the university, but it suffers from two limitations. First, the results appear contradictory. Some studies show that the issue of free speech is overblown by media reportage, whilst others track serious concerns about free speech arising from certain university policies. Second, the findings exclude important issues concerning restrictions to speech on campus that fall outside the traditional debate around violations to free speech rights. This is particularly the case when certain voices are excluded from important policy conversations, and in issues around diversifying the curriculum. This article overcomes these two limitations by developing a novel conceptual framework within which to situate current debates concerning speech-related matters in universities. It does so by developing a taxonomy around the concept of ‘silencing’. It then considers the current issue of speech matters in universities within this framework to determine whether, and to what extent, speech is indeed unduly restricted, and where this is a concern for free speech violations, and where it falls outside this issue.     

发展基因沉默技术,控制作物土传真菌病害

作物土传真菌病害是当前农业所面临的最重要问题之一,由于防治困难,正日趋成为限制我国农业生产可持续发展的重要因素。基因沉默(或RNA沉默,RNAi)是广泛存在于真核生物中,基于同源序列调控基因表达的一条重要途径,而由此发展起来的基因沉默技术,作为一种新防治策略被广泛地应用于防控植物有害生物的研究中。文章综合介绍了作物土传真菌病害的发生与防治现状、RNA沉默及其在植物有害生物防控应用的最新研究进展,客观分析了基因沉默技术在防治作物土传真菌病害的巨大潜力和亟需解决的主要问题,阐述了研发基因沉默技术对可持续控制作物土传真菌病害的重要性及其巨大应用前景。     

RNAi的研究进展

RNAi是通过双链RNA的介导特异性降解相应序列的mRNA,从而导致转录后水平的基因沉默．广泛存在于真菌、植物和动物等真核生物中．RNAi是自然界存在的生物抵抗病毒入侵、抑制转座子活动的一种防御机制,现已发展成为功能基因组学研究的重要手段之一．     

植物转基因沉默的机制及消除

随着转基因技术在各个领域的深入发展 ,转基因沉默已引起越来越多的人关注 .其作用机制主要有三种 :位置效应、转录水平的基因沉默和转录后水平的基因沉默 .实验表明 ,MAR不仅能提高植物中转基因的整体表达水平 ,同时还可以降低不同转化体之间的差异 ,有效消除植物转基因沉默     

‘I was always the good girl’: the twofold silencing of teachers as a force fostering a low sense of professional self-efficacy

The purpose of this study was to expand the theory of self-efficacy in relation to feminist perspectives by exploring the factors and the dynamics that foster a low sense of professional self-efficacy in Israeli female teachers. Listening to their voices enables us to learn about their past experiences in the nuclear family and consider their repercussions for professional self-efficacy in the present. Fourteen teachers who were identified as having a low sense of professional self-efficacy participated in in-depth open interviews. Data were analysed according to Grounded Theory methodology, implementing the axial coding procedure. Findings indicated that these teachers’ sense of professional self-efficacy was affected by their experience of having been silenced by the dominant authority figures in two spheres of life: the nuclear family (parents) and the workplace (school principal). Similar patterns in the two spheres and their implications for teachers and principals are discussed.