种子萌发的抑制调控机制

种子萌发是植物生命周期中一个重要的生理过程,激素作用、miRNA抑制、mRNA区域化、表观遗传调控等多个层次的分子抑制参与该过程的调控。赤霉素（解除抑制的激素）合成和失活的调控主要发生在转录水平,而脱落酸（引起抑制的激素）信号转导途径的调控则通过蛋白质抑制物的降解来实现。miRNA在转录后水平使其靶基因的mRNA降解,抑制种子的萌发;通过mRNA的区域化抑制与萌发相关基因的翻译属于另一层次的转录后抑制;小RNA介导的表观遗传机制也可能在种子萌发过程基因表达的协同调控中发挥重要作用。与分子水平的抑制类似,胚乳和种皮产生的机械抑制也很重要。     

bHLH转录因子的磷酸化调控植物生理功能的研究进展

bHLH转录因子是植物体内第二大类转录因子,在植物生长发育和胁迫反应的转录调控网络中扮演着非常重要的角色。磷酸化作为蛋白质翻译后重要的调控方式,影响转录因子的转录活性、定位、蛋白间互作、稳定性。为深入了解磷酸化对bHLH转录因子的影响,本文对近年来bHLH家族成员的磷酸化研究进展进行综述,包括bHLH转录因子的结构、分类、功能以及磷酸化位点上的突变对其生理及生化功能的改变,为从磷酸化调控角度提升农作物的营养利用效率、品质和抗逆性等农艺性状提供理论依据。     

铁代谢与蛋白质泛素化．降解调控研究进展

铁元素为几乎所有的生命体所必需,维持铁代谢稳态对机体的正常功能至关重要。铁代谢紊乱与人类多种疾病的发生和发展有关。已知铁代谢稳态受到一系列参与铁代谢环节的关键蛋白质,如IRP2等的精确调节。这些重要蛋白质的稳定性、生理活性的动态变化及其协调作用是细胞维持铁代谢平衡的分子基础。除了转录和转录后水平的调控,泛素化等翻译后修饰方式和蛋白质降解是细胞精确调控参与铁代谢的蛋白质的水平及功能普遍而有效的方式之一;同时,细胞的铁代谢状态也影响细胞内参与泛素化等翻译后修饰途径的酶类的活性和稳定性,从而在铁代谢和蛋白质修饰．降解途径之间形成反馈机制,实时和动态地完成对细胞内铁代谢水平的精确调控。就相关领域的最新进展作简要综述。     

植物多酚通过microRNA调控脂质代谢研究进展

microRNA（简称miRNA）是长度18~25个核苷酸的非编码RNA分子,具有调控mRNA的翻译和/或稳定性的功能,从而在转录后水平调节不同基因的表达。人体内约60%编码蛋白的基因的表达受到miRNA调节,其中包括脂质代谢调控相关基因。植物多酚具有良好的生物活性,可以通过调节脂质代谢相关miRNAs,如miR-122和miR-33的表达进而发挥降血脂等活性。该文综述了miRNA调控脂质代谢相关mRNA的作用机制以及植物多酚在这一过程中的可能作用。     

植物成熟microRNA转录后修饰与降解的研究进展

microRNA(miRNA)是一类长度为20–24 nt的内源小RNA,广泛存在于各种植物体内,参与调控植物器官的形态建成、激素应答、逆境胁迫和营养代谢等一系列过程。虽然miRNA生物合成和功能研究已取得了很大进展,但关于植物成熟miRNA的转录后修饰和降解的研究却报道较少。一方面miRNA如同其它RNA存在半衰期,其降解对于调控细胞内miRNA含量起重要作用,从而调控植物的生长发育或胁迫响应等过程;另一方面,成熟miRNA存在转录后修饰,可影响miRNA的稳定性,最终影响其活性。该文着重从植物成熟miRNA的转录后修饰和降解等方面进行了综述。     

基于转录组与翻译组的海洋食烷菌(Alcanivorax)烷烃代谢调控研究

【目的】食烷菌是海洋烃类降解优势菌,其烷烃代谢调控机制有待深入研究。本研究拟从食烷菌转录和翻译水平上认识烷烃降解的调控过程。【方法】分别以乙酸和正十六烷(C16)为唯一碳源与能源,获取柴油食烷菌(Alcanivorax dieselolei) B5菌株的转录组和翻译组数据,并整合数据计算得到该菌在2种碳源培养条件下基因的翻译效率。采用基因本体论(gene ontology, GO)和京都基因和基因组百科全书(Kyoto encyclopedia of genes and genomes, KEGG)对差异翻译和翻译效率基因进行功能和代谢通路注释。【结果】当以C16为唯一碳源与能源时,B5菌株烷烃代谢途径的关键基因在转录与翻译水平均大量提升,包括烷烃单加氧酶、细胞色素P450氧化酶、醇脱氢酶和醛脱氢酶等。KEGG富集结果表明,翻译水平显著上调基因参与了肽聚糖生物合成、脂肪酸降解、氯代烷烃降解、氧化磷酸化和生物膜形成等通路;翻译效率差异基因主要富集在铁载体非核糖体肽的生物合成、氧化磷酸化和不饱和脂肪酸的生物合成等途径。通过转录组和翻译组学的联合分析显示,为了适应烷烃氧化,B5有效地协调了转...     

RNA结合蛋白与巨噬细胞炎症因子表达

RNA结合蛋白(RNA-binding proteins,RBPs)是转录后基因表达的关键调控因子,参与剪接、出核、翻译和稳定性等RNA代谢调控。RBPs表达或功能异常可导致炎症性疾病、代谢性疾病以及神经系统疾病等多种疾病的发生发展。炎症是机体对外界刺激及损伤的防御性免疫反应。巨噬细胞作为机体重要的免疫细胞,通过快速响应刺激并且释放大量炎症因子,进而调控炎症反应。巨噬细胞中炎症因子的表达受到转录以及转录后水平的调控。其中,RBPs参与大量RNA的转录后调控过程。研究发现,一方面,RBPs直接结合炎症因子mRNA中的顺式作用元件,参与其mRNA稳定性和翻译等过程,例如TTP(tristetraprolin);另一方面,某些RBPs通过参与炎症信号通路中一些关键基因mRNA的稳定性、翻译或选择性剪接调控,进而间接影响炎症因子表达及分泌。例如,剪接因子3A亚基1(splicing factor 3A subunit 1, SF3A1)。本文主要总结RBPs在mRNA稳定性、翻译和选择性剪接不同转录后水平调控巨噬细胞炎症因子表达的作用机制。这些RBPs从不同的层面直接或者间接参与调控炎症因子的表达,有些相互协同,有些相互拮抗,是宏观的、整体的对机体炎症反应的调控。深入探讨RBPs调控巨噬细胞炎症因子以及炎症反应的作用机制,对于从不同角度认识、预防以及治疗炎症性相关疾病,具有重要意义。     

植物microRNAs研究进展

植物microRNAs(miRNAs)是一类与RNA诱导沉默复合体相关的约由22个核苷酸组成的单链小RNA分子, 其主要功能是, 通过特异性剪切靶mRNA或阻遏靶mRNA的正常翻译在转录后水平调控基因的负表达。植物miRNAs的靶标主要是参与调控植物生长发育和防御应答的转录因子家族。文章主要综述miRNAs在植物体内的生物发生、作用机制及其调控作用研究新进展。     

蛋白质组学研究揭示的植物根盐胁迫响应机制

植物根是感知外界盐胁迫信号的首要器官。近年来,人们利用高通量的差异表达蛋白质组学技术,分析了水稻(Oryzasativa)、拟南芥(Arabidopsis thaliana)、大豆(Glycine max)、大麦(Hordeum vulgare)、小麦(Triticum aestivum)、木榄(Bruguieragymnorhiza)和匍匐翦股颖(Agrostis stolonifera)等植物根应答盐胁迫过程中蛋白质组的动态变化特征。通过整合植物根响应盐胁迫蛋白质组学研究结果,揭示了植物根部响应盐胁迫的多种调节机制,包括:利用多种信号通路与蛋白质磷酸化/去磷酸化感知并传递盐胁迫信号;通过膜蛋白与转运蛋白调节离子吸收/外排与区室化;通过抗氧化酶系统活性清除活性氧,并通过合成多种渗透调节物质与防御物质减轻细胞受到的伤害;通过改变参与糖类与能量代谢相关酶的表达调节能量代谢水平;通过细胞骨架动态重塑保持正常的细胞结构、物质运输与信息传递;通过转录、翻译与翻译后调控调节各种蛋白质的动态变化与相互作用;通过调控各种基础代谢与次生代谢水平保持细胞结构与代谢状态正常。     

植物中硝酸还原酶和亚硝酸还原酶的作用

植物通过硝酸盐同化途径以硝酸盐和氨的形式吸收氮元素。硝酸盐的同化是一个受到严格控制的过程,其中两个先后参加反应的酶——硝酸还原酶(NR)和亚硝酸还原酶(NiR)对初级氮的同化起主要调控。在高等植物中,NR和NiR基因的转录及转录后加工受到各种内在和外在因素的影响,翻译后调控是消除亚硝酸盐积累的重要机制。随着分子生物学技术的发展,可以更容易地通过突变体和转基因方式来研究NR和NiR基因的调控。     

硝酸还原酶活性的调节及可能机制的研究进展

氮素是农业研究的重点 ,硝酸还原酶是氮代谢中的一个关键酶。有关硝酸还原酶的研究一直是植物生理生化研究的重点。该文就近年来有关硝酸还原酶活性调节的可能机制的研究进展作了简要的综述     

Molecular approaches to the analysis of nitrate assimilation

Abstract. The application of molecular approaches such as mutant analysis and recombinant DNA technology, in conjunction with immunology, are set to revolutionize our understanding of the nitrate assimilation pathway. Mutant analysis has already led to the identification of genetic loci encoding a functional nitrate reduction step and is expected to lead ultimately to the identification of genes encoding nitrate uptake and nitrite reduction. Of particular significance would be identification of genes whose products contribute to regulatory networks controlling nitrogen metabolism. Recombinant DNA techniques are particularly powerful and have already allowed the molecular cloning of the genes encoding the apoprotein of nitrate reductase and nitrite reductase. These successes allow for the first lime the possibility to study directly the role of environmental factors such as type of nitrogen source (NO₃⁻ or NH₄⁺) available to the plant, light, temperature water potential and CO₂ and O₂ tensions on nitrate assimilation gene expression and its regulation at the molecular level. This is an important advance since our current understanding of the regulation of nitrate assimilation is based largely on changes of activity of the component steps. The availability of mutants, cloned genes, and gene transfer systems will permit attempts to manipulate the nitrate assimilation pathway.     

Comparative studies of diurnal variations of nitrate reductase activity in wheat, oat and barley

Diurnal variations of in vitro and in vivo (intact tissue assay) nitrate reductase (EC 1.6.6.1) activity and stability were examined in leaves of wheat ( Triticum aestivum L. cv. Runar), oat ( Avcna saliva L. cv. Mustang) and barley ( Hordeum vulgure L. cv. Agneta and cv. Gunillu). Nitrate reductase activity was generally higher for wheat than for oat and barley. However, the diurnal variations of nitrate reductase activity and stability were principally the same for all species, e.g. the high activity during the photoperiod was associated with low stability. All species showed a rapid (30-60 min) increase in the in vitro and in vivo activity when the light was switched on. When light was switched off the in vitro activity decreased rapidly whereas decrease in in vivo activity was slower. These experiments support the hypothesis that an activation/ deactivation mechanism is involved in the regulation of diurnal variations in nitrate reductase activity. Red light enhanced nitrate reductase activity in etiolated wheat and barley leaves. In green leaves, however, the daily increase in nitrate reductase activity was not induced by a brief red light treatment. Indications of different regulation mechanisms for the diurnal variations of nitrate reductase activity among the cereals were not found.     

Nitrate reductase and its role in nitrate assimilation in plants

Nitrate reductase (EC 1.6.6.1) is an enzyme found in most higher plants and appears to be a key regulator of nitrate assimilation as a result of enzyme induction by nitrate. The biochemistry of nitrate reductase has been elucidated to a great extent and the role that nitrate reductase plays in regulation of nitrate assimilation is becoming understood.     

A comparison of the influence of iron on the growth and nitrate metabolism of Anabaena and Scenedesmus

A comparative study of growth and nitrate metabolism of Anabaena flos-aquae (Lyng.) Bréb. and Scenedesmus bijugatus var. seriatus Chodat investigated possible mechanisms for the iron-stimulated increases in growth specific for blue-green algae in mixed algal communities. Algae were separately grown in an morganic medium with varying concentrations of iron and nitrate to determine the effects on each organism. Iron was found to be a limiting nutrient for cultures of both Anabaena and Scenedesmus as determined by chlorophyll a concentrations and cell enumeration. Both iron and nitrate stimulated the specific activity of nitrate reductase, nitrite reductase, and glutamine synthetase in Anabaena. Iron enrichment did not increase the activity of the enzymes in Scenedesmus, but inhibited the activity of nitrate reductase and glutamine synthetase. The stimulation of growth by iron in cells grown under iron limiting conditions was associated with increased nitrate metabolism in Anabaena but not in Scenedesmus.