乙烯利诱导玉米根皮层通气组织的形成与程序化细胞死亡的关系

乙烯利可诱导玉米根皮层细胞发生死亡解体而形成通气组织，随着乙烯利浓度的升高，根皮层细胞的死亡数目升高，利用TUNEL（末端标记法）实验显示，根皮层细胞核DNA发生了断裂现象，出现了暴露的3′－OH末端，这为乙烯利诱导的通气组织形成中有程序化细胞死亡（PCO）的发生首次提供了直接证据；同时在外源乙烯利处理的玉米根部发现SOD和CAT活性显著下降，继而造成活性氧的积累，由于活性氧是诱导PCD的重要原因，因此，外源乙烯利诱发的PCD的发生极有可能是通过活性氧介导的。     

Cyclic GMP is involved in the excitation of invertebrate photoreceptors

The hyperpolarizing receptor potential in vertebrate rod photoreceptors appears to be mediated by the second messenger, cyclic GMP. Injection of cGMP into rods or application of cGMP to inside-out membrane patches activates a conductance resembling that produced by light. Light produces a rapid reduction of cGMP in living rods, leading to closure of sodium channels and membrane hyperpolarization. In most invertebrate photoreceptors the response to light is depolarizing. We have investigated whether cGMP is involved in controlling the increase in sodium conductance that underlies this depolarization. We show here that injection of cGMP into Limulus photoreceptors produces a depolarization that mimics the receptor potential. We also show that the cGMP concentration of the squid retina increases rapidly during exposure to light. These results support the hypothesis that cGMP mediates the light-induced depolarization in invertebrate photoreceptors and suggests that vertebrate and invertebrate phototransduction may be more similar than previously thought.     

微量水分对喷气燃料中悬浮物形成的影响

采用在喷气燃料中直接加入水分和加入水分后再蒸馏等方法,分别用SC-6微量水分测定仪和Abakus颗粒测量分析仪测定了喷气燃料中的微量水分和悬浮物的颗粒数及粒度分布,考察了水分对喷气燃料中悬浮物形成的影响。实验结果表明,水分的存在是影响喷气燃料中悬浮物形成的重要因素之一。加水后再蒸馏的喷气燃料中,密封静置120 d后基本没有悬浮物产生。喷气燃料中的水分含量控制在21.50×10-6时,能抑制悬浮物的生成。     

微量水分对喷气燃料中悬浮物形成的影响

采用在喷气燃料中直接加入水分和加入水分后再蒸馏等方法,分别用SC-6微量水分测定仪和Abakus颗粒测量分析仪测定了喷气燃料中的微量水分和悬浮物的颗粒数及粒度分布,考察了水分对喷气燃料中悬浮物形成的影响.实验结果表明,水分的存在是影响喷气燃料中悬浮物形成的重要因素之一.加水后再蒸馏的喷气燃料中,密封静置120 d后基本没有悬浮物产生.喷气燃料中的水分含量控制在21.50×10-6时,能抑制悬浮物的生成.     

Superoxide anion is involved in the breakdown of endothelium-derived vascular relaxing factor

Endothelium-derived vascular relaxing factor (EDRF) is a humoral agent that is released by vascular endothelium and mediates vasodilator responses induced by various substances including acetylcholine and bradykinin. EDRF is very unstable, with a half-life of between 6 and 50 s, and is clearly distinguishable from prostacyclin. The chemical structure of EDRF is unknown but it has been suggested that it is either a hydroperoxy- or free radical-derivative of arachidonic acid or an unstable aldehyde, ketone or lactone. We have examined the role of superoxide anion (O-2) in the inactivation of EDRF released from vascular endothelial cells cultured on microcarrier beads and bioassayed using a cascade of superfused aortic smooth muscle strips. With this system, we have now demonstrated that EDRF is protected from breakdown by superoxide dismutase (SOD) and Cu2+, but not by catalase, and is inactivated by Fe2+. These findings indicate that O-2 contributes significantly to the instability of EDRF.     

Functional genomic screen reveals genes involved in lipid-droplet formation and utilization

Eukaryotic cells store neutral lipids in cytoplasmic lipid droplets enclosed in a monolayer of phospholipids and associated proteins. These dynamic organelles serve as the principal reservoirs for storing cellular energy and for the building blocks for membrane lipids. Excessive lipid accumulation in cells is a central feature of obesity, diabetes and atherosclerosis, yet remarkably little is known about lipid-droplet cell biology. Here we show, by means of a genome-wide RNA interference (RNAi) screen in Drosophila S2 cells that about 1.5% of all genes function in lipid-droplet formation and regulation. The phenotypes of the gene knockdowns sorted into five distinct phenotypic classes. Genes encoding enzymes of phospholipid biosynthesis proved to be determinants of lipid-droplet size and number, suggesting that the phospholipid composition of the monolayer profoundly affects droplet morphology and lipid utilization. A subset of the Arf1-COPI vesicular transport proteins also regulated droplet morphology and lipid utilization, thereby identifying a previously unrecognized function for this machinery. These phenotypes are conserved in mammalian cells, suggesting that insights from these studies are likely to be central to our understanding of human diseases involving excessive lipid storage.     

MSG is involved in sperm gelatinolytic activity in the prawn, Macrobrachium rosenbergii

Proteases in male reproductive tract are considered to play key roles in fertilization processes.In contrast to mammals,there are limited data concerning crustacean sperm proteases.We previously identified a novel sperm gelatinase(MSG) from Macrobrachium rosenbergii that was inhibited by a male reproduction-related Kazal-type protease inhibitor(MRPINK) specifically.In the present study,MSG was found to be distributed on the vas deferens and terminal ampullae by Western blot.Immunohistochemical analyses revealed that MSG was expressed in secretory epithelial cells and sperm distributed mainly at the base zone.RNA interference(RNAi) mediated knock-down of MSG resulted in a marked loss of sperm gelatinolytic activity.Taken together,the results show that MSG is closely linked to and probably involved in the fertilization process.     

Muscarinic acetylcholine receptor is involved in acetylcholine regulating stomatal movement

In animal cells, action of acetylcholine depends on its binding with its two specific receptors on the plasma membrane: the nicotinic and muscarinic respectively. The present investigation has shown that agonists of muscarinic receptor (muscarine) could induce stomatal opening, while the antagonists (atropine) could block stomatal opening induced by acetylcholine. Their effects can only be realized in medium containing Ca²⁺, but not in medium containing K⁺. The results tend to reveal that the muscarinic receptor is involved in acetylcholine-induced stomatal movement.     

The mahogany protein is a receptor involved in suppression of obesity

Genetic studies have shown that mutations within the mahogany locus suppress the pleiotropic phenotypes, including obesity, of the agouti-lethal-yellow mutant. Here we identify the mahogany gene and its product; this study, to our knowledge, represents the first positional cloning of a suppressor gene in the mouse. Expression of the mahogany gene is broad; however, in situ hybridization analysis emphasizes the importance of its expression in the ventromedial hypothalamic nucleus, a region that is intimately involved in the regulation of body weight and feeding. We present new genetic studies that indicate that the mahogany locus does not suppress the obese phenotype of the melanocortin-4-receptor null allele or those of the monogenic obese models (Lep(db), tub and Cpe(fat)). However, mahogany can suppress diet-induced obesity, the mechanism of which is likely to have implications for therapeutic intervention in common human obesity. The amino-acid sequence of the mahogany protein suggests that it is a large, single-transmembrane-domain receptor-like molecule, with a short cytoplasmic tail containing a site that is conserved between Caenorhabditis elegans and mammals. We propose two potential, alternative modes of action for mahogany: one draws parallels with the mechanism of action of low-affinity proteoglycan receptors such as fibroblast growth factor and transforming growth factor-beta, and the other suggests that mahogany itself is a signalling receptor.     

Deg1 is involved in the degradation of the PsbO oxygen-evolving protein of photosystem II in Arabidopsis

Deg1, a thylakoid lumen-localized protease, retains both chaperone and protease activities. The in vivo function of Deg1 has been shown to be involved not only in PSII assembly but also in the degradation of PSII reaction center protein D1. Here we used the transgenic plants with reduced Deg1 to examine whether the lumen-localized proteins are also the substrates of Deg1 in vivo. Our results showed that the transgenic plants accumulated degradation products of the PsbO protein while the levels of full-length PsbO were not affected. The PsbO degradation products could be efficiently degraded by the recombinant Deg1. These results suggest that Deg1 is involved in the degradation of the PsbO degradation fragments, but not in the initial cleavage event itself.     

Protein phosphorylation is involved in the water stress-induced ABA accumulation in the roots ofMalus hupehensis Rehd

Water stress-induced ABA accumulation plays a key role in the root to shoot communication and/or the cell to cell signaling under the soil stresses. The signaling of the water stress itself that leads to the accumulation, however, is less known. In this study, we subjected the roots of Malus hupehensis seedlings to water stress treatment and investigated the ABA accumulation in relation to protein phosphorylation. Our results showed that ABA accumulation could be substantially triggered in 40 min and reached 4 folds in 100 min after treatment with 30% PEG 6000 (polyethylene glycol). The water stress treatment also led to a substantial enhancement of total kinase activity, assessed with histone-Ⅲ as substrate, in 15 min and a maximum enhancement in 30 min before it declined to initial level. The Ca²⁺-dependent kinase activity showed a similar, if not more sensitive, trend. When the roots were fed with labeled ³²P- ATP, water stress enhanced the labeling of proteins, which showed a maximum labeling at 40 min. Two inhibitors of protein kinases, Quercetin and H7, effectively diminished or completely blocked the ABA accumulation under the stress treatment. It is therefore suggest that protein phosphorylation is involved in the signaling of the water stress-induced ABA accumulation.     

An Arabidopsis ctpA homologue is involved in the repair of photosystem II under high light

A T-DNA insertion mutant AtctpA1 was identified to study the physiological roles of a carboxyl-terminal processing protease (CtpA) homologue in Arabidopsis. Under normal growth conditions, disruption of AtctpA1 did not result in any apparent alterations in growth rate and thylakoid membrane protein components. However the mutant plants exhibited increased sensitivity to high irradiance. Degradation of PSII reaction center protein D1 was accelerated in the mutant during photoinhibition. These results demostrated that AtctpA1 was required for efficient repair of PSII in Arabidopsis under high irradiance.     

RACK1依赖的miRNA途径参与调节植物叶绿素的生物合成

为深入探索活化C激酶受体1(receptor of activated C kinase 1,RACK 1)在调节植物microRNA(miRNA)的生物发生,以及其靶基因中的关键作用,对在美国国家生物技术信息中心(National Center for Biotechnology Information,NCBI)网站上共享的基因表达综合数据库(Gene Expression Omnibus,GEO)中有关rack1突变体的小RNA序列数据重新进行了系统分析和挖掘,找到了19个新miRNA.通过解析差异miRNA表达,鉴定到了特异调控叶绿素合成相关基因HEMA和HEMC表达的miRNA,为今后深入系统地研究RACK1在调节叶绿体发育和光合作用机理提供了关键的理论依据,也为利用公共数据库挖掘潜在的数据信息提供了基本的研究设想和思路.     

一个与ABA信号通路相关未知基因AB的亚细胞定位研究

本研究通过构建一个与脱落酸（ABA）信号传导途径相关的未知基因AB和绿色荧光蛋白（GFP）编码基因的重组质粒,利用基因枪技术将该重组质粒成功转入洋葱表皮细胞,观察并确定了该基因编码蛋白细胞核和细胞质的亚细胞定位,为进一步研究该未知基因的生物学功能及其分子机制提供了思路.     

Phosphatidylglycerol is involved in protein translocation across Escherichia coli inner membranes

Newly synthesized proteins to be exported out of the cytoplasm of bacterial cells have to pass across the inner membrane. In Gram-negative bacteria ATP, a membrane potential, the products of the sec genes and leader peptidases (enzymes which cleave the N-terminal signal peptides of the precursor proteins) are required. The mechanism of translocation, however, remains elusive. Important additional roles for membrane lipids have been repeatedly suggested both on theoretical grounds and on the basis of experiments with model systems but no direct evidence had been obtained. We demonstrate here, using mutants of Escherichia coli defective in the synthesis of the major anionic membrane phospholipids, that phosphatidylglycerol is involved in the translocation of newly synthesized outer-membrane proteins across the inner membrane.     

Sleep in Drosophila is regulated by adult mushroom bodies

Sleep is one of the few major whole-organ phenomena for which no function and no underlying mechanism have been conclusively demonstrated. Sleep could result from global changes in the brain during wakefulness or it could be regulated by specific loci that recruit the rest of the brain into the electrical and metabolic states characteristic of sleep. Here we address this issue by exploiting the genetic tractability of the fruitfly, Drosophila melanogaster, which exhibits the hallmarks of vertebrate sleep. We show that large changes in sleep are achieved by spatial and temporal enhancement of cyclic-AMP-dependent protein kinase (PKA) activity specifically in the adult mushroom bodies of Drosophila. Other manipulations of the mushroom bodies, such as electrical silencing, increasing excitation or ablation, also alter sleep. These results link sleep regulation to an anatomical locus known to be involved in learning and memory.     

A discrete sequence in a platelet integrin is involved in ligand recognition

Platelet membrane glycoprotein IIb-IIIa (gpIIb-IIIa; alpha IIb-beta 3), the most prominent member of the integrin family of adhesion receptors on these cells, mediates platelet aggregation by binding fibrinogen and is critical in thrombosis and haemostasis. A short amino-acid sequence at the carboxy terminus of the gamma chain of fibrinogen is recognized by gpIIb-IIIa and peptides containing this sequence are selectively crosslinked to residues 294-314 of gpIIb. Here we show that an 11-residue peptide from this region of gpIIb inhibits platelet aggregation and binding of fibrinogen to platelets and to purified gpIIb-IIIa, and that it interacts directly with fibrinogen. These results implicate this segment of gpIIb-IIIa in the ligand-binding function of the receptor. Moreover, as this region is highly conserved among integrins, it may have a general function in ligand recognition by this broadly distributed family of adhesion receptors.