Comparative effect of allopolyploidy on transposable element composition and gene expression between Gossypium hirsutum and its two diploid progenitors

An allopolyploidization event formed allotetraploid Gossypium species from an A-genome diploid species and a D-genome diploid species. To explore the responses of transposable elements(TEs) to allopolyploidy, we assembled parallel TE datasets from G. hirsutum, G. arboreum and G. raimondii and analyzed the TE types and the effects of TEs on orthologous gene expression in the three Gossypium genomes.Gypsy was the most abundant TE type and most TEs were located $500 bp from genes in all three genomes. In G. hirsutum, 35.6% of genes harbored TE insertions, whereas insertions were more frequent in G. arboreum and G. raimondii. G. hirsutum had the highest proportion of uniquely matching 24-nt small interfering RNAs(siRNAs) that targeted TEs. TEs,particularly those targeted by 24-nt siRNAs, were associated with reduced gene expression, but the effect of TEs on orthologous gene expression varied substantially among species. Orthologous gene expression levels in G. hirsutum were intermediate between those of G. arboreum and G. raimondii, which did not experience TE expansion or reduction resulting from allopolyploidization. This study underscores the diversity of TEs co-opted by host genes and provides insights into the roles of TEs in regulating gene expression in Gossypium.     

Human PIWI(HIWI) is an azoospermia factor

正Transposable elements(TEs)make up nearly half of the mammalian genome.Recent probabilistic re-annotation of genome sequences indicated that as much as two-thirds or more of the human genome may be derived from TEs(de Koning et al.,2011).Their ability to mobilize in the genome represents a constant threat to the host by creating insertion mutations,which may lead to progressive deterioration of genetic information.To counteract this threat,host cells     

纪念冯德培先生百年诞辰

今年是冯德培先生百年诞辰,他离开我们已经12个年头了。冯先生一生在科学上有很多重要的建树和发现,在这里我仅仅根据我对他不是很多的接触来回忆他对科学问题的敏锐觉察和掌握,毕生追求科学真理的高尚品质,以及他对中国生理学和神经科学发展不可磨灭的贡献。     

"光合作用发现史"教学的组织

以高中生物学"光合作用发现史"的教学为例,对科学发现史教学的目标确定、内容组织、教学策略等方面进行了一些富有启发性的探讨.强调科学方法训练既包括科学研究方法和科学思维方式,又涉及创新意识、科学态度和科学精神.     

转基因大米品尝会:中国情境下的公众参与科学

以转基因大米品尝会为例,通过问卷调查、访谈法、观察法研究由公众主动发起的科学传播活动及其参与者。描述了该类活动的发起和组织过程,发现参与者是一群热爱科学、认同科学价值并愿意传播科学的人,他们的行动对自己、对亲友、对社会都产生了一定的影响。转基因大米品尝会以及类似的活动是转型期中国情境下的公众参与科学实践。     

做科学的困惑及视角

走近科学前沿的人,感觉就像被困在一个古堡里的斗士,当你在黑暗中费了九牛二虎之力终于把一扇门打开时,发现出现在你面前的是另外几个锁住的门。这种困惑是痛苦的,很多情况下令人沮丧不堪。这曾经一度让我觉得做科学是入错行了。大多数做科学的人都会经历这几种困惑,不能从这些困惑中走出来的人,常常会因此而放弃做科学。问题越来越多通常人们总是希望干完一件事后能享受一下完成任务的喜悦,但这一点做科学的人很难体验到,即使偶尔体验到,也是稍纵即逝。这使我联想     

科学探究中问题的发现、形成与表述

探究性学习是指学生以类似于科学家进行科学探究的方式进行学习,是学习生物学知识的重要途径。问题是科学探究的起点,并贯穿于科学探究全过程,也是科学探究活动逐步深入的原动力。通过案例分析,探讨了如何从客观事物中发现并提出有价值的生物学探究问题以及如何科学准确地表述问题。     

Embryo and Endosperm Function and Failure inSolanumSpecies and Hybrids

Although the importance of the endosperm as a food store inmany angiosperm seeds is well known, its significance duringearly embryogenesis has been neglected. In many interspecifichybrids, and in some other situations, embryos do not developfully and abort. It has often been stated that this is causedby the endosperm failing to conduct sufficient nutrients tothe embryo, but seldom has it been suggested that the endospermactively controls most of the early stages of morphogenesisof the embryo. Information gleaned from a broad survey of theliterature, combined with additional evidence presented here,obtained fromSolanum incanumand interspecific hybrids, indicatethat the endosperm is dynamic and very active in regulatingearly embryo development. This requires highly integrated geneticcontrol of rapidly changing metabolism in the endosperm. Ininterspecific hybrids, lack of coordination may cause unbalancedproduction of growth regulating substances by the endospermand hence abortion of the embryo, or even unregulated productionof nucleases and proteases resulting firstly in autolysis ofthe endosperm and then digestion of the embryo. The endospermmay thus serve to detect inappropriate hybridization of speciesor ploidy levels and so prevent waste of resources by producingseeds that would result in sterile hybrids or unthrifty subsequentgenerations. This discriminatory function of the endosperm hasdiminished during evolution and domestication of the crop plantSolanummelongenaL.Copyright 1998 Annals of Botany Company Solanum, embryo morphogenesis, endosperm, hybrid, seed development.     

环腺苷酸应答元件结合蛋白与学习记忆

环腺苷酸(cAMP)应答元件结合蛋白(cAMP response element binding protein,CREB)是一种核转录因子,可与cAMP反应元件结合,调节基因转录,具有调节精子生成,昼夜节律,学习记忆等功能.近年来关于其在学习记忆中的作用成为医学研究热点.CREB是神经元内多条信息传递途径的汇聚点,参与长时记忆形成和突触可塑性.长时记忆(long-term memory)形成需依赖CREB介导的基因转录,干扰或抑制CREB活性可破坏长时记忆.长时程增强(long-term potentiation,LTP)是研究学习记忆的理想模型,在LTP诱导和维持过程中均可观察到CREB活性持续升高.但增龄过程中,海马CREB活性下降,影响学习记忆功能,与许多神经退行性疾病发生有关.     

HIFs and tumors--causes and consequences

For most organisms oxygen is essential fo life. When oxygen levels drop below those required to maintain the minimum physiological oxygen requirement of an organism or tissue it is termed hypoxia. To counter act possible deleterious effects of such a state, an immediate molecular response is initiated causing adaptation responses aimed at cell survival. This response is mediated by the hypoxia-inducible factor-1 (HIF-1), which is a heterodimer consisting of an alpha- and a beta-subunit. HIF-1 alpha protein is stabilized under hypoxic conditions and therefore confers selectivity to this response. Hypoxia is characteristic of tumors, mainly because of impaired blood supply resulting from abnormal growth. Over the past few years enormous progress has been made in the attempt to understand how the activation of the physiological response to hypoxia influences neoplastic growth. In this review some aspects of HIF-1 pathway activation in tumors and the consequences for pathophysiology and treatment of neoplasia are discussed.