实时荧光定量分析小黑杨应拉木相关基因及转录因子的表达

利用实时定量RT-PCR技术,比较了不同时期小黑杨应拉木中与木材形成相关的基因及其转录因子的表达模式。研究结果表明,与纤维素合成相关的基因如纤维素合成酶基因（CesA）、蔗糖合成酶基因（SUSY）、ACC氧化酶基因（ACO）等基因胁迫后在弯曲茎的上侧中表达量高于其在弯曲茎的下侧中的表达;尤其是FLA基因家族在弯曲茎的上侧中大量表达,而在弯曲茎的下侧中几乎不表达。与之相反,与木质素合成相关的基因如咖啡酰辅酶A-O-甲基转移酶（CCoAOMT）、苯丙氨酸裂解酶（PAL）、漆酶（laccase）、过氧化物酶（POD）等基因在弯曲茎的上侧中表达量低而在弯曲茎的下侧中表达量高,转录因子MYB基因在弯曲茎的上侧中表达量高于其在弯曲茎的下侧中的。     

Oxygen‐induced transcriptional dynamics in human osteoblasts are most prominent at the onset of mineralization

Oxygen tension plays an important role in the regulation of cellular processes. During hematopoietic stem cell (HSC) differentiation, HSCs migrate from one stem cell niche to the next, each with a different oxygen tension that determines which signaling pathways are on and off, determining the differentiation stage of the cell. Oxygen tension influences osteoblast differentiation and mineralization. Low oxygen levels inhibit matrix formation and mineralization. We were interested in the regulatory mechanisms that underlie this inhibition and wondered whether a switch in oxygen tension could have varying effects depending on the differentiation phase of the osteoblasts. We performed an oxygen tension switch phase study in which we switched osteoblasts from high to low oxygen tension during their 3 week differentiation and mineralization process. We performed microarray expression profiling on samples collected during this 3 week period and analyzed biochemical and histo‐chemical endpoint parameters to determine the effect of a switch in oxygen levels on mineralization. We found that low oxygen tension has the most profound impact on mineralization when administered during the period of matrix maturation. Additionally, a large set of genes was regulated by oxygen, independent of the differentiation phase. These genes were involved in cell metabolisms and matrix formation. Our study demonstrates that variation in oxygen tension strongly affects gene expression in differentiating osteoblasts. The magnitude of this change for either expression levels or the number of regulated probes, depends on the osteoblast differentiation stage, with the phase prior to the onset of mineralization being most sensitive. J. Cell. Physiol. 228: 1863–1872, 2013. © 2013 Wiley Periodicals, Inc.     

Effects of light and low oxygen tension on pigment biosynthesis in Halobacterium salinarum, revealed by a novel method to quantify both retinal and carotenoids

A novel method for analyzing halobacterial pigments was developed, in which retinal was liberated from halobacterial rhodopsins as retinal oxime by hydroxylamine, ethyl beta-apo-8'-carotenoate was introduced as an internal standard, and the pigments including bacterioruberin and beta-carotene were analyzed by HPLC at the same time. With this method, we revealed that light enhances the biosynthesis of bacterioruberin and the conversion of beta-carotene to retinal, but does not affect beta-carotene biosynthesis in Halobacterium salinarum strain Oyon Moussa-16. Low oxygen tension given in the light brought a slight increase in retinal accumulation, although its biosynthesis from beta-carotene is an oxygenation reaction. This paradox could be explained by the increase in beta-carotene biosynthesis.     

高等植物脯氨酸代谢研究进展

很多植物在胁迫条件下可以通过增加合成、减少降解而在体内累积大量脯氨酸,这对于调节渗透平衡、防止渗透胁迫对植物造成伤害、清除自由基、保护细胞结构具有重要意义。脯氨酸合成、降解相关酶的编码基因大都已经克隆到,但对脯氨酸在植物发育中的具体作用、胁迫条件下脯氨酸累积的分子机理了解还比较少。概述了植物控制脯氨酸合成、降解相关酶的编码基因的研究进展情况。     

Oxygen-regulated expression of genes for pigment binding proteins in Rhodobacter capsulatus

Oxygen is the major external factor affecting the expression of photosynthesis genes in facultatively photosynthetic bacteria. Many investigations over the last years mainly carried out on the closely related species Rhodobacter capsulatus and Rhodobacter sphaeroides have identified a number of proteins involved in the oxygen-regulated signal pathway, in which the RegB/RegA two component system plays a central role. While the RegB/RegA system activates photosynthesis genes under low oxygen tension other proteins like CrtJ and PPBP have a repressing function under high oxygen tension. Additional DNA binding proteins like the integration host factor can modulate the expression of photosynthesis genes. The role of alternative sigma factors in this signal pathway is still unclear.     

Bacterial regulatory networks include direct contact of response regulator proteins: interaction of RegA and NtrX in Rhodobacter capsulatus

The formation of photosynthetic complexes in facultatively photosynthetic bacteria is controlled by the oxygen tension in the environment. In Rhodobacter capsulatus the two-component system RegB/RegA plays a major role in the redox control of photosynthesis genes but also controls other redox-dependent systems. The response regulator RegA is phosphorylated under low oxygen tension and activates the puf and puc operons, which encode pigment binding proteins, by binding to their promoter regions. Data from a yeast two-hybrid analysis as well as an in vitroanalysis indicate that RegA interacts with the NtrX protein, the response regulator of the NtrY/NtrX two-component system which is believed to be involved in regulation of nitrogen fixation genes. Our further analysis revealed that NtrX is indeed involved in the regulation of the puf and puc operons. Furthermore, we showed that an altered NtrX protein, which is predicted to adopt the conformation of phosphorylated NtrX protein, binds within the puf promoter region close to the RegA binding sites. We conclude that a direct interaction of two response regulators connects the regulatory systems for redox control and nitrogen control.     

Bacteriochlorophyll-dependent expression of genes for pigment-binding proteins in<Emphasis Type="Italic"> Rhodobacter capsulatus</Emphasis> involves the RegB/RegA two-component system

Expression of the puf and puc operons, which encode proteins of the photosynthetic apparatus of Rhodobacter capsulatus, is regulated by oxygen. A drop in the oxygen tension in the environment leads to an increase in the levels of puf and puc mRNAs. In strains lacking bacteriochlorophyll (Bchl) due to mutations in bch genes, the rise in puf and puc mRNA levels observed on reduction of oxygen tension is much less pronounced than in wild-type cells, indicating co-regulation of the syntheses of pigments and pigment-binding proteins. Here we show that Bchl synthesis also affects the expression of the bchC gene, which codes for a subunit of bacteriochlorophyll synthase, suggesting an autoregulatory mechanism for the Bchl biosynthetic pathway. Furthermore, our data provide evidence that the RegB/RegA two-component system, which is known to play a central role in oxygen-controlled expression of photosynthesis genes, is also involved in the Bchl-dependent regulation. Mutant strains which do not synthesize RegB or RegA show similar oxygen-dependent puf and puc expression in the presence and absence of Bchl. Our results support the view that the RegB/RegA system can directly or indirectly sense whether Bchl synthesis takes place or not.     

Prostacyclin does not change during an oxygen induced increase in pulmonary blood flow in the fetal lamb

The role of prostacyclin in mediating the increase in pulmonary blood flow caused by an increase in oxygen tension in the fetal lamb was investigated. Plasma concentrations of 6-keto-PGF1 alpha, the hydrolysis product of prostacyclin, were measured during an increase in pulmonary blood flow caused by a rise in oxygen tension in eight intrauterine fetal lambs. Fetal oxygen tension was increased by placing the pregnant ewes in a hyperbaric chamber and having them breathe 100% oxygen at three atmospheres absolute pressure. This increased fetal PaO2 from 27 +/- 3 to 60 +/- 6 torr (mean +/- S.E., p less than or equal to 0.0001) and increased the proportion of right ventricular output distributed to the fetal lungs from 6 +/- 2 to 45 +/- 7% (mean +/- S.E., p less than or equal to 0.001). However, the fetal plasma concentration of 6-keto-PGF1 alpha did not change, 186 +/- 26 to 208 +/- 40 pg/ml (mean +/- S.E.). Indomethacin decreased plasma concentrations of 6-keto-PGF1 alpha in each of three fetuses but did not decrease the proportion of right ventricular output distributed to their lungs. The increase in pulmonary blood flow caused by an increase in oxygen tension in the fetal lamb is not associated with an increase in plasma concentrations of 6-keto-PGF1 alpha. Prostacyclin does not appear to be involved in the increase in pulmonary blood flow caused by the increase in oxygen tension at birth.     

Analysis of gene expression in non-regressed and regressed bovine corpus luteum tissue using a customized ovarian cDNA array

The lifespan of the bovine corpus luteum (CL) is an important factor in the control of normal ovarian cyclicity and the establishment and maintenance of pregnancy. There is increasing evidence that CL lifespan is regulated by alternative expression of genes that promote or inhibit luteolysis. To gain further insights into these events a 434 character ovarian cDNA array comprising genes attributed to key aspects of CL function including more than 100 anonymous expressed sequence tags (ESTs) was constructed and screened with alpha(33)P dATP labeled RNA isolated from non-regressed (n=6) and regressed (n=6) CL tissue. Significance analysis of microarrays (SAM) identified 15 genes that changed expression 1.7-fold or more with a false discovery rate of <5%. The differentially expressed genes encoded enzymes involved in steroid biosynthesis and oxygen radical metabolism and proteins involved in extracellular matrix remodeling, apoptosis and cell structure. Results for five of the differentially expressed genes including matrix gla protein and collagen alpha1(I) (extracellular matrix), glutathione-S-transferase alpha I (oxygen metabolism), clusterin (apoptosis) and scavenger receptor BI (steroid biosynthesis) were confirmed by Northern blot analysis and found to be significantly different (P<0.01) between non-regressed and regressed CL tissue. Collectively this study identified genes with recognized roles in CL regression, genes with potential roles in this process and genes whose function have yet to be defined in this event.     

Gene expression profiling of the long-term adaptive response to hypoxia in the gills of adult zebrafish

Low oxygen levels (hypoxia) play a role in clinical conditions such as stroke, chronic ischemia, and cancer. To better understand these diseases, it is crucial to study the responses of vertebrates to hypoxia. Among vertebrates, some teleosts have developed the ability to adapt to extremely low oxygen levels. We have studied long-term adaptive responses to hypoxia in adult zebrafish. We used zebrafish that survived severe hypoxic conditions for 3 wk and showed adaptive behavioral and phenotypic changes. We used cDNA microarrays to investigate hypoxia-induced changes in expression of 15,532 genes in the respiratory organs (the gills). We have identified 367 differentially expressed genes of which 117 showed hypoxia-induced and 250 hypoxia-reduced expressions. Metabolic depression was indicated by repression of genes in the TCA cycle in the electron transport chain and of genes involved in protein biosynthesis. We observed enhanced expression of the monocarboxylate transporter and of the oxygen transporter myoglobin. The hypoxia-induced group further included the genes for Niemann-Pick C disease and for Wolman disease [lysosomal acid lipase (LAL)]. Both diseases lead to a similar intra- and extracellular accumulation of cholesterol and glycolipids. The Niemann-Pick C protein binds to cholesterol from internal lysosomal membranes and is involved in cholesterol trafficking. LAL is responsible for lysosomal cholesterol degradation. Our data suggest a novel adaptive mechanism to hypoxia, the induction of genes for lysosomal lipid trafficking and degradation. Studying physiological responses to hypoxia in species tolerant for extremely low oxygen levels can help identify novel regulatory genes, which may have important clinical implications.     

真菌对唑类抗真菌药物的耐受机制

唑类抗真菌药物广泛用于临床和农业。唑类药物通过与羊毛甾醇14α-去甲基化酶（Erg11p/Cyp51）结合,抑制麦角甾醇合成,同时导致有毒甾醇积累。真菌可快速在转录水平上对唑类药物胁迫作出响应而导致耐药性,尤其是唑类药物外排泵基因和麦角甾醇合成相关基因表达的上调。农业和临床上绝大多数唑类药物耐药菌株的形成都是由麦角甾醇合成基因和唑类药物外排泵表达的变化或是突变所致。一些转录因子（如Pdr1p、Pdr3p、Upc2p、Yap1p、Tac1p、Mrr1p、CCG-8）和信号通路（如cAMP途径、PKC-MAPK途径、HOG MAPK途径、钙调磷酸酶途径）均参与对药物外排泵基因和麦角甾醇合成基因等的调控,影响唑类药物耐药性。针对于这些调控因子设计的抑制剂将有助于提高唑类药物的治疗效果。本文概述了唑类药物的抑菌机制、真菌对唑类药物耐药性形成的原因、真菌对唑类药物适应性响应机理,并对未来此领域的热点和方向进行了展望。     

多杀菌素的生物合成

多杀菌素是一种新颖大环内酯类杀虫剂,具有对害虫高效、对环境安全、对哺乳动物低毒的优异特点。介绍了多杀菌素生物合成的步骤,及参与这些合成步骤的有关酶系统和基因簇。通过对刺糖多孢菌中多杀菌素合成基因的克隆鉴定与分析,已基本了解多杀菌素生物合成的限速步骤及相关控制基因,从而可通过遗传工程的办法改造刺糖多孢菌,提高多杀菌素的产量 。