中国、英国、印度苹果黑星病菌SSR遗传多样性分析

<正>苹果黑星病Venturia inaequalis(Cooke)G.winter(无性型为Spilocaea pomi Fr.)是苹果树上危害非常严重的一种病害,在世界各苹果产区均有发生。欧洲各国对苹果黑星病菌的研究已经比较深入,     

New players in the regulation of ecdysone biosynthesis

Insect ecdysone steroid hormone regulates major developmental transitions, such as molting and metamorphosis. The production of ecdysone correlates well with the timing of these transitions. Finding out how the ecdysone biosynthesis is regulated is crucial to fully understand these sophisticated developmental switches. Here we summarized recent findings in the regulation of ecdysone biosynthesis from the aspects of cell signaling, key biosynthetic enzymes and substrate cholesterol trafficking.     

Cloning, sequencing, and characterization of a gene cluster involved in EDTA degradation from the bacterium BNC1

EDTA is a chelating agent, widely used in many industries. Because of its ability to mobilize heavy metals and radionuclides, it can be an environmental pollutant. The EDTA monooxygenases that initiate EDTA degradation have been purified and characterized in bacterial strains BNC1 and DSM 9103. However, the genes encoding the enzymes have not been reported. The EDTA monooxygenase gene was cloned by probing a genomic library of strain BNC1 with a probe generated from the N-terminal amino acid sequence of the monooxygenase. Sequencing of the cloned DNA fragment revealed a gene cluster containing eight genes. Two of the genes, emoA and emoB, were expressed in Escherichia coli, and the gene products, EmoA and EmoB, were purified and characterized. Both experimental data and sequence analysis showed that EmoA is a reduced flavin mononucleotide-utilizing monooxygenase and that EmoB is an NADH:flavin mononucleotide oxidoreductase. The two-enzyme system oxidized EDTA to ethylenediaminediacetate (EDDA) and nitrilotriacetate (NTA) to iminodiacetate (IDA) with the production of glyoxylate. The emoA and emoB genes were cotranscribed when BNC1 cells were grown on EDTA. Other genes in the cluster encoded a hypothetical transport system, a putative regulatory protein, and IDA oxidase that oxidizes IDA and EDDA. We concluded that this gene cluster is responsible for the initial steps of EDTA and NTA degradation.     

甘草对大鼠小肠动力功能影响的实验研究

目的:初步探讨甘草对大鼠小肠动力的作用,及其作用与胃肠激素的相关性.方法:观察甘草组与空白组移行性综肌电(MMC)周期持续时间、Ⅲ相持续时间、Ⅲ相每分钟快波数(FM)和每簇的快波数(FC)的变化;采用免疫组织化学法结合显微图像定量分析扫描系统检测十二指肠、空肠嗜铬细胞及其肌间神经丛中5-羟色胺(5-HT)、P-物质(SP)、血管活性肠肽(VIP)的相对含量.结果:①甘草组与空白组比较MMCⅢ相FM和FC明显减少,MMC周期明显延长,Ⅲ相持续时间明显缩短,统计有显著性差异(P＜0.05).②甘草组十二指肠、空肠粘膜及肌间神经丛内5-HT表达明显较空白组减少,比较有显著性差异,小肠粘膜无明显SP、VIP阳性免疫反映物表达,但小肠肌间神经丛内SP含量明显减少、VIP含量明显增加,组间比较有显著性差异(P＜0.05,P＜0.01).结论:甘草对大鼠小肠动力有抑制作用,这种抑制作用与5-HT、SP、VIP分泌失调密切相关.     

Coordinated production and utilization of FADH2 by NAD(P)H-flavin oxidoreductase and 4-hydroxyphenylacetate 3-monooxygenase

4-Hydroxyphenylacetate (4HPA) 3-monooxygenase (HpaB) is a reduced flavin adenine dinucleotide (FADH(2)) utilizing monooxygenase. Its cosubstrate, FADH(2), is supplied by HpaC, an NAD(P)H-flavin oxidoreductase. Because HpaB is the first enzyme for 4HPA metabolism, FADH(2) production and utilization become a major metabolic event when Escherichia coli W grows on 4HPA. An important question is how FADH(2) is produced and used, as FADH(2) is unstable in the presence of free O(2). One solution is metabolic channeling by forming a transitory HpaB-HpaC complex. However, our in vivo and in vitro data failed to support the interaction. Further investigation pointed to an alternative scheme for HpaB to sequester FADH(2). The intracellular HpaB concentration was about 122 microM in 4HPA-growing cells, much higher than the total intracellular FAD concentration, and HpaB had a high affinity for FADH(2) (K(d) of 70 nM), suggesting that most FADH(2) is bound to HpaB in vivo. The HpaB-bound FADH(2) was either used to rapidly oxidize 4HPA or slowly oxidized by O(2) to FAD and H(2)O(2) in the absence of 4HPA. Thus, HpaB's high intracellular concentration, its high affinity for FADH(2), its property of protecting bound FADH(2) in the absence of 4HPA, and its ability to rapidly use FADH(2) to oxidize 4HPA when 4HPA is available can coordinate FADH(2) production and utilization by HpaB and HpaC in vivo. This type of coordination, in responding to demand, for production and utilization of labile metabolites has not been reported to date.     

Genetic and biochemical characterization of a 2,4,6-trichlorophenol degradation pathway in Ralstonia eutropha JMP134

Ralstonia eutropha JMP134 can grow on several chlorinated aromatic pollutants, including 2,4-dichlorophenoxyacetate and 2,4,6-trichlorophenol (2,4,6-TCP). Although a 2,4,6-TCP degradation pathway in JMP134 has been proposed, the enzymes and genes responsible for 2,4,6-TCP degradation have not been characterized. In this study, we found that 2,4,6-TCP degradation by JMP134 was inducible by 2,4,6-TCP and subject to catabolic repression by glutamate. We detected 2,4,6-TCP-degrading activities in JMP134 cell extracts. Our partial purification and initial characterization of the enzyme indicated that a reduced flavin adenine dinucleotide (FADH2)-utilizing monooxygenase converted 2,4,6-TCP to 6-chlorohydroxyquinol (6-CHQ). The finding directed us to PCR amplify a 3.2-kb fragment containing a gene cluster (tcpABC) from JMP134 by using primers designed from conserved regions of FADH2-utilizing monooxygenases and hydroxyquinol 1,2-dioxygenases. Sequence analysis indicated that tcpA, tcpB, and tcpC encoded an FADH2-utilizing monooxygenase, a probable flavin reductase, and a 6-CHQ 1,2-dioxygenase, respectively. The three genes were individually inactivated in JMP134. The tcpA mutant failed to degrade 2,4,6-TCP, while both tcpB and tcpC mutants degraded 2,4,6-TCP to an oxidized product of 6-CHQ. Insertional inactivation of tcpB may have led to a polar effect on downstream tcpC, and this probably resulted in the accumulation of the oxidized form of 6-CHQ. For further characterization, TcpA was produced, purified, and shown to transform 2,4,6-TCP to 6-CHQ when FADH2 was supplied by an Escherichia coli flavin reductase. TcpC produced in E. coli oxidized 6-CHQ to 2-chloromaleylacetate. Thus, our data suggest that JMP134 transforms 2,4,6-TCP to 2-chloromaleylacetate by TcpA and TcpC. Sequence analysis suggests that tcpB may function as an FAD reductase, but experimental data did not support this hypothesis. The function of TcpB remains unknown.     

转基因油菜应用研究

油菜是重要油料作物,我国60％以上人口食用菜油,我国油菜面积和总产居世界首位。在油菜育种和品种改良中,常用的方法是有性杂交的方法,通过亲本染色体组的分离和重组,进行多代选择,以创造新类型。但这种方法有一定的局限性,受生物分类的限制,使远缘类型之间不可以进行基因交换。70年代以来,随着植物基因工程技术的发展,应用遗传转化的方法,能够突破物种间的界限,转移有用的基因,使远缘类型之间可以进行基因的交换,为创造新的生命类型开拓了无限广阔的前景。其次,还可以获得生物的定向变异,即     

鼠类危害农作物临界数量近似值的估计

鼠类对于农作物的危害,害情严重程度往往与田间害鼠的密度成正比。田间害鼠密度较低时,并不足以为大患,为节省人力和物力,只需及时组织少数人力进行人工捕打,即可获效,而不必兴师动众,采用大面积化学防除;但是,一旦害鼠数量锐增,大量聚集田间,不进行大面积毒杀不足以控制害情的发展时,则需不失时机,恰如其分地采取化学防除的手段,防止或减轻经济损失。 但究竟在什么时候,采取什么方式进行灭鼠,才能够以最少的人力和物力取得最大的植