蜡样芽孢杆菌中锰超氧化物歧化酶基因的表达差异性

对蜡样芽孢杆菌(Bacilluscereus)905中2个不同的锰超氧化物歧化酶(MnSOD)基因(sodA1和sodA2)转录水平的差异性进行分析.结果发现:sodA1和 sodA2在细菌的不同生长阶段为组成性表达,sodA1基因启动子的活性比sodA2高3~4倍;超氧化物歧化酶(SOD)的缺失能同时诱导sodA1和sodA2的转录.该研究结果解释了这2个不同的MnSOD在细胞内的酶活性差异,并推测在sodA1和sodA2基因启动子上可能存在与氧自由基代谢相关的调控元件;同时,本研究也成功实现了LacZ在芽孢杆菌上的标记.     

百子莲2个ARF基因与2个Aux/IAA基因的全长克隆与序列分析

采用不同浓度外源生长素类调节物质毒莠定(PIC)对百子莲(Agapanthus praecox ssp. orientalis)进行继代培养,并对其胚性愈伤组织进行比较转录组学研究,获得了百子莲生长素信号转导途径中的2个ARF和2个Aux/IAA家族基因,推测其为体胚发生过程中生长素信号传导途径相关的重要调控因子。采用RACE技术获得ApARF1、ApARF2、ApAux/IAA2与ApAux/IAA3的cDNA全长,分别为2 343、2 888、1 034和821 bp,开放阅读框(ORF)长度分别为1 770、2 349、480和549 bp,分别编码589、782、159和182个氨基酸残基。生物学分析表明,ApARF1与ApARF2蛋白均具有ARF家族的典型结构,ApAux/IAA2蛋白结构域Ⅳ不完整,ApAux/IAA3结构域Ⅱ部分缺失,但仍具有Aux/IAA蛋白的典型功能。转基因实验表明,ApAux/IAA过表达植株表现出生长延缓及发育受阻的表型,ApARF过表达植株表现出生长促进、花期提前的表型,验证了百子莲ApARF和ApAux/IAA家族蛋白对植物生长发育的调控作用。     

Two distinct cytokines released from a human aminoacyl-tRNA synthetase

Aminoacyl-tRNA synthetases catalyze aminoacylation of transfer RNAs (tRNAs). It is shown that human tyrosyl-tRNA synthetase can be split into two fragments with distinct cytokine activities. The endothelial monocyte-activating polypeptide II-like carboxy-terminal domain has potent leukocyte and monocyte chemotaxis activity and stimulates production of myeloperoxidase, tumor necrosis factor-alpha, and tissue factor. The catalytic amino-terminal domain binds to the interleukin-8 type A receptor and functions as an interleukin-8-like cytokine. Under apoptotic conditions in cell culture, the full-length enzyme is secreted, and the two cytokine activities can be generated by leukocyte elastase, an extracellular protease. Secretion of this tRNA synthetase may contribute to apoptosis both by arresting translation and producing needed cytokines.     

Genetics. Motivating hotspots

Only recently have we begun to characterize fine-scale recombination rates in mammals. In her Perspective, Przeworski discusses the work by Myers et al. in which linkage disequilibrium data have been used to produce a high-resolution recombination map for most of the human genome. More than 25,000 putative hotspots have been identified, as well as the first motifs that appear to influence their intensity.