植物蔗糖非发酵-1相关蛋白激酶家族研究进展

蛋白质磷酸化与去磷酸化过程在细胞的信号转导网络中起关键的作用,是生物体中普遍存在的一种调节机制。植物中的蛋白激酶通过磷酸化和去磷酸化在调节ABA信号传导、能量缺失反应和非生物胁迫反应过程中有着重要的作用。其中,植物蔗糖非发酵-1相关蛋白激酶(sucrose non-fermenting-1-related protein kinase,SnRK)是植物蛋白激酶家族中一个重要家族,它们与酵母中的SNF1(sucrose non-fermenting-1,SNF1)和哺乳动物中的AMPK(AMP-activated protein kinase,AMPK)同源,具有与它们相似和自身独特的功能,根据其氨基酸序列的同源性和表达模式的差异可分为3个亚组:SnRK1、SnRK2和SnRK3。目前,在拟南芥、水稻、豆科植物、高粱以及苔藓植物等基因组中都发现了大量的SnRK蛋白激酶,它们广泛参与了植物的生长发育、病虫害防御、ABA和非生物胁迫等各种信号的应答反应。     

Computational method for discovery of estrogen responsive genes

Estrogen has a profound impact on human physiology and affects numerous genes. The classical estrogen reaction is mediated by its receptors (ERs), which bind to the estrogen response elements (EREs) in target gene's promoter region. Due to tedious and expensive experiments, a limited number of human genes are functionally well characterized. It is still unclear how many and which human genes respond to estrogen treatment. We propose a simple, economic, yet effective computational method to predict a subclass of estrogen responsive genes. Our method relies on the similarity of ERE frames across different promoters in the human genome. Matching ERE frames of a test set of 60 known estrogen responsive genes to the collection of over 18,000 human promoters, we obtained 604 candidate genes. Evaluating our result by comparison with the published microarray data and literature, we found that more than half (53.6%, 324/604) of predicted candidate genes are responsive to estrogen. We believe this method can significantly reduce the number of testing potential estrogen target genes and provide functional clues for annotating part of genes that lack functional information.     

药源植物盾叶薯蓣甾体皂苷及皂苷元的研究进展

盾叶薯蓣是重要的甾体激素类药源植物,其根茎中薯蓣皂苷元含量居薯蓣属植物之冠,为我国的特有种。为了寻找高含量的资源、筛选新的生理活性成分,多年来我国学者做了大量的研究工作。主要概括了盾叶薯蓣的资源分布、薯蓣皂苷元的提取工艺、化学成分、药理、含量测定等方面的研究。     

RNAi and microRNA: breakthrough technologies for the improvement of plant nutritional value and metabolic engineering

This article raises the complex issue of improving plant nutritional value through metabolic engineering and the potential of using RNAi and micro RNA technologies to overcome this complexity, focusing on a few key examples. It also highlights current knowledge of RNAi and microRNA functions and discusses recent progress in the development of new RNAi vectors and their applications. RNA interference (RNAi) and microRNA (miRNA) are recent breakthrough discoveries in the life sciences recognized by the 2006 Nobel Prize in Physiology or Medicine. The importance of these discoveries relates not only to elucidating the fundamental regulatory aspects of gene expression, but also to the tremendous potential of their applications in plants and animals. Here, we review recent applications of RNAi and microRNA for improving the nutritional value of plants, discuss applications of metabolomics technologies in genetic engineering, and provide an update on the related RNAi and microRNA technologies.     

Bayesian analysis of population structure based on linked molecular information

The Bayesian model-based approach to inferring hidden genetic population structures using multilocus molecular markers has become a popular tool within certain branches of biology. In particular, it has been shown that heterogeneous data arising from genetically dissimilar latent groups of individuals can be effectively modelled using an unsupervised classification formulation. However, most currently employed models ignore potential linkage within the employed molecular information, and can therefore lead to biased inferences under certain circumstances. Utilizing the general theory of graphical models, we develop a framework that accounts for dependences both within linked molecular marker loci and DNA sequence data. Due to a high level of sequence conservation among eukaryotic species, the latter aspect is particularly relevant for analyzing rapidly evolving microbial species. The advantages of incorporating the dependence due to linkage in the classification models are illustrated by analyses of both simulated data and real samples of Bacillus cereus.     

Heat shock protein 70 is translocated to lipid droplets in rat adipocytes upon heat stimulation

In mammalian cells, lipid storage droplets contain a triacylglycerol and cholesterol ester core surrounded by a phospholipid monolayer into which a number of proteins are imbedded. These proteins are thought to be involved in modulating the formation and metabolic functions of the lipid droplet. In this study, we show that heat stress upregulates several heat shock proteins (Hsps), including Hsp27, Hsp60, Hsp70, Hsp90, and Grp78, in primary and differentiated adipocytes. Immunostaining and immunoblotting data indicate that among the Hsps examined, only Hsp70 is induced to redirect to the lipid droplet surface in heat-stressed adipocytes. The thermal induction of Hsp70 translocation to lipid droplet does not typically happen in a temperature- or time-dependent manner and occurs abruptly at 30-40 min and rapidly achieves a steady state within 60 min after 40 degrees C stress of adipocytes. Though Hsp70 is co-localized with perilipin on the lipid droplets in stressed adipocytes, immunoprecipitation experiments suggest that Hsp70 does not directly interact with perilipin. Alkaline treatments indicate that Hsp70 associates with the droplet surface through non-hydrophobic interactions. We speculate that Hsp70 might noncovalently associate with monolayer microdomains of the lipid droplet in a manner similar to its interaction with lipid bilayer moieties composed of specific fatty acids. As an acute and specific cellular response to the heat stimulation, accumulation of Hsp70 on adipocytes lipid droplets might be involved in stabilizing the droplet monolayer, transferring nascent proteins to the lipid droplets, or chaperoning denatured proteins on the droplet for subsequent refolding.     

A kinetic model describing Shewanella oneidensis MR-1 growth, substrate consumption, and product secretion

Aerobic growth of Shewanella oneidensis MR-1 in minimal lactate medium was studied in batch cultivation. Acetate production was observed in the middle of the exponential growth phase and was enhanced when the dissolved oxygen (DO) concentration was low. Once the lactate was nearly exhausted, S. oneidensis MR-1 used the acetate produced during growth on lactate with a similar biomass yield as lactate. A two-substrate Monod model, with competitive and uncompetitive substrate inhibition, was devised to describe the dependence of biomass growth on lactate, acetate, and oxygen and the acetate growth inhibition across a broad range of concentrations. The parameters estimated for this model indicate interesting growth kinetics: lactate is converted to acetate stoichiometrically regardless of the DO concentration; cells grow well even at low DO levels, presumably due to a very low K(m) for oxygen; cells metabolize acetate (maximum specific growth rate, micro(max,A) of 0.28 h(-1)) as a single carbon source slower than they metabolize lactate (micro(max,L) of 0.47 h(-1)); and growth on acetate is self-inhibiting at a concentration greater than 10 mM. After estimating model parameters to describe growth and metabolism under six different nutrient conditions, the model was able to successfully estimate growth, oxygen and lactate consumption, and acetate production and consumption under entirely different growth conditions.     

Ganoderic acid T from Ganoderma lucidum mycelia induces mitochondria mediated apoptosis in lung cancer cells

Ganoderma lucidum is a well-known traditional Chinese medicinal herb containing many bioactive compounds. Ganoderic acid T (GA-T), which is a lanostane triterpenoid purified from methanol extract of G. lucidum mycelia, was found to exert cytotoxicity on various human carcinoma cell lines in a dose-dependent manner, while it was less toxic to normal human cell lines. Animal experiments in vivo also showed that GA-T suppressed the growth of human solid tumor in athymic mice. It markedly inhibited the proliferation of a highly metastatic lung cancer cell line (95-D) by apoptosis induction and cell cycle arrest at G(1) phase. Moreover, reduction of mitochondria membrane potential (Delta psi(m)) and release of cytochrome c were observed during the induced apoptosis. Our data further indicate that the expression of proteins p53 and Bax in 95-D cells was increased in a time-dependent manner, whereas the expression of Bcl-2 was not significantly changed; thus the ratio of Bcl-2/Bax was decreased. The results show that the apoptosis induction of GA-T was mediated by mitochondrial dysfunctions. Furthermore, stimulation of the activity of caspase-3 but not caspase-8 was observed during apoptosis. The experiments using inhibitors of caspases (Z-VAD-FMK, Z-DEVD-FMK and Z-IETD-FMK) confirmed that caspase-3 was involved in the apoptosis. All our findings demonstrate that GA-T induced apoptosis of metastatic lung tumor cells through intrinsic pathway related to mitochondrial dysfunction and p53 expression, and it may be a potentially useful chemotherapeutic agent.     

Rotavirus infection alters peripheral T-cell homeostasis in children with acute diarrhea

The patterns of gene expression and the phenotypes of lymphocytes in peripheral blood mononuclear cells (PBMC) from children with diarrhea caused by rotavirus and healthy children were compared by using DNA microarray, quantitative PCR, and flow cytometry. We observed increased expression of a number of genes encoding proinflammatory cytokines and interferon or interferon-stimulated proteins and demonstrated activation of some genes involved in the differentiation, maturation, activation, and survival of B lymphocytes in PBMC of patients with rotavirus infection. In contrast, we observed a consistent pattern of lower mRNA levels for an array of genes involved in the various stages of T-cell development and demonstrated a reduction in total lymphocyte populations and in the proportions of CD4 and CD8 T lymphocytes from PBMC of patients. This decreased frequency of T lymphocytes was transient, since the proportions of T lymphocytes recovered to almost normal levels in convalescent-phase PBMC from most patients. Finally, rotavirus infection induced the activation and expression of the early activation markers CD83 and CD69 on a fraction of CD19 B cells and the remaining CD4 and CD8 T lymphocytes in acute-phase PBMC of patients; the expression of CD83 continued to be elevated and was predominantly exhibited on CD4 T lymphocytes in convalescent-phase PBMC. On the basis of these findings at the molecular, phenotypic, and physiologic levels in acute-phase PBMC, we conclude that rotavirus infection induces robust proinflammatory and antiviral responses and B-cell activation but alters peripheral T-cell homeostasis in children.     

Tissue-cell- and species-specific expression of gonadotropin-regulated long chain acyl-CoA synthetase (GR-LACS) in gonads, adrenal and brain. Identification of novel forms in the brain

Gonadotropin-regulated long chain acyl-CoA synthetase (GR-LACS) is a novel hormonally regulated fatty acyl-CoA synthetase (FACS) with activity for long-chain fatty acids. The presence of this enzyme in the Leydig cells of the mature rat testis and its mode of regulation suggest that it participates in testicular steroidogenesis. This study demonstrates that GR-LACS expression is tissue, cell and species-specific. The 79 kDa GR-LACS protein is expressed in rodent gonads and brain, and only in the mouse in the adrenal cortex. In the ovary of both species it is associated with follicles undergoing atresia. It is present in the newborn and immature testis tubules and after puberty only in the Leydig cells. A distinct GR-LACS protein species of 64 kDa that was more abundant than the 79 kDa long form was found in the rat brain. Also, a minor 73 kDa form was observed in the rat brain and mouse ovary. Two novel species resulting from alternatively splicing of the GR-LACS gene were identified in a rat brain cDNA library: a short form 1 (S1) lacking exon 8 and short form 2 (S2) lacking exons 6–8. Expression studies revealed that the sizes of the S1/S2 proteins are comparable to those of the endogenous variant species. Neither S form contains FACSs activity, suggesting that exon 8 is essential for the enzymatic function. GR-LACS variants exhibit small but significant dominant negative effects on the FACS activity of the long form. GR-LACS variants may regulate the long form's activity in the brain.