共查询到20条相似文献，搜索用时 31 毫秒
1.
Kobayashi KS Chamaillard M Ogura Y Henegariu O Inohara N Nuñez G Flavell RA 《Science (New York, N.Y.)》2005,307(5710):731-734
The gene encoding the Nod2 protein is frequently mutated in Crohn's disease (CD) patients, although the physiological function of Nod2 in the intestine remains elusive. Here we show that protective immunity mediated by Nod2 recognition of bacterial muramyl dipeptide is abolished in Nod2-deficient mice. These animals are susceptible to bacterial infection via the oral route but not through intravenous or peritoneal delivery. Nod2 is required for the expression of a subgroup of intestinal anti-microbial peptides, known as cryptdins. The Nod2 protein is thus a critical regulator of bacterial immunity within the intestine, providing a possible mechanism for Nod2 mutations in CD. 相似文献
2.
Giraud E Moulin L Vallenet D Barbe V Cytryn E Avarre JC Jaubert M Simon D Cartieaux F Prin Y Bena G Hannibal L Fardoux J Kojadinovic M Vuillet L Lajus A Cruveiller S Rouy Z Mangenot S Segurens B Dossat C Franck WL Chang WS Saunders E Bruce D Richardson P Normand P Dreyfus B Pignol D Stacey G Emerich D Verméglio A Médigue C Sadowsky M 《Science (New York, N.Y.)》2007,316(5829):1307-1312
Leguminous plants (such as peas and soybeans) and rhizobial soil bacteria are symbiotic partners that communicate through molecular signaling pathways, resulting in the formation of nodules on legume roots and occasionally stems that house nitrogen-fixing bacteria. Nodule formation has been assumed to be exclusively initiated by the binding of bacterial, host-specific lipochito-oligosaccharidic Nod factors, encoded by the nodABC genes, to kinase-like receptors of the plant. Here we show by complete genome sequencing of two symbiotic, photosynthetic, Bradyrhizobium strains, BTAi1 and ORS278, that canonical nodABC genes and typical lipochito-oligosaccharidic Nod factors are not required for symbiosis in some legumes. Mutational analyses indicated that these unique rhizobia use an alternative pathway to initiate symbioses, where a purine derivative may play a key role in triggering nodule formation. 相似文献
3.
群体感应是微生物之间相互交流的一种重要联络方式,它协助细菌能感应群体密度从而调节基因表达。20世纪80年代以来,多种群体感应信号及其传导机制得以阐明。DSF（diffusible signal factor）是近年来在野油菜黄单胞菌中首先鉴定的1个新型群体感应信号,化学结构为顺式11?甲基?2?十二碳烯酸,其信号传导途径包括RpfC/RpfG双组分感应系统、二级信使环二鸟苷酸（c-di-GMP）、全局性转录因子Clp等。在野油菜黄单胞菌中,DSF群体感应信号调控3类生物学功能：一是促进致病相关基因的表达;二是抑制生物膜形成;三是促进黄单胞菌作出代谢调整,适应高群体密度环境。RpfF是DSF信号生物合成过程中的关键酶,黄单胞菌在高群体密度条件下通过一种新型自我诱导机制大量合成DSF。DSF信号不仅存在于所有黄单胞菌属细菌中,也广泛存在于苛养木杆菌、嗜麦芽寡养单胞菌、伯克氏菌、铜绿假单胞菌和许多海洋细菌中,其传导途径和生物学功能还有待进一步阐明。 相似文献
4.
Although much is known about the bacterial genetics of early nodulation, little is known about the plant cell response. Alfalfa root hair cells were impaled with intracellular microelectrodes to measure a membrane potential depolarizing activity in Rhizobium meliloti cell-free filtrates, a plant response dependent on the bacterial nodulation genes. The depolarization was desensitized by repeated exposure to factors and was not observed in a representative nonlegume. A purified extracellular Nod factor, NodRm-IV(S), caused membrane potential depolarization at nanomolar concentrations. This rapid single-cell assay provides a tool for dissecting the mechanisms of host cell response in early nodulation. 相似文献
5.
Op den Camp R Streng A De Mita S Cao Q Polone E Liu W Ammiraju JS Kudrna D Wing R Untergasser A Bisseling T Geurts R 《Science (New York, N.Y.)》2011,331(6019):909-912
Rhizobium-root nodule symbiosis is generally considered to be unique for legumes. However, there is one exception, and that is Parasponia. In this nonlegume, the rhizobial nodule symbiosis evolved independently and is, as in legumes, induced by rhizobium Nod factors. We used Parasponia andersonii to identify genetic constraints underlying evolution of Nod factor signaling. Part of the signaling cascade, downstream of Nod factor perception, has been recruited from the more-ancient arbuscular endomycorrhizal symbiosis. However, legume Nod factor receptors that activate this common signaling pathway are not essential for arbuscular endomycorrhizae. Here, we show that in Parasponia a single Nod factor-like receptor is indispensable for both symbiotic interactions. Therefore, we conclude that the Nod factor perception mechanism also is recruited from the widespread endomycorrhizal symbiosis. 相似文献
6.
NSP1 of the GRAS protein family is essential for rhizobial Nod factor-induced transcription 总被引：1，自引：0，他引：1
Smit P Raedts J Portyanko V Debellé F Gough C Bisseling T Geurts R 《Science (New York, N.Y.)》2005,308(5729):1789-1791
7.
Limpens E Franken C Smit P Willemse J Bisseling T Geurts R 《Science (New York, N.Y.)》2003,302(5645):630-633
The rhizobial infection of legumes has the most stringent demand toward Nod factor structure of all host responses, and therefore a specific Nod factor entry receptor has been proposed. The SYM2 gene identified in certain ecotypes of pea (Pisum sativum) is a good candidate for such an entry receptor. We exploited the close phylogenetic relationship of pea and the model legume Medicago truncatula to identify genes specifically involved in rhizobial infection. The SYM2 orthologous region of M. truncatula contains 15 putative receptor-like genes, of which 7 are LysM domain-containing receptor-like kinases (LYKs). Using reverse genetics in M. truncatula, we show that two LYK genes are specifically involved in infection thread formation. This, as well as the properties of the LysM domains, strongly suggests that they are Nod factor entry receptors. 相似文献
8.
Nod2 mutation in Crohn's disease potentiates NF-kappaB activity and IL-1beta processing 总被引：1，自引：0，他引：1
Maeda S Hsu LC Liu H Bankston LA Iimura M Kagnoff MF Eckmann L Karin M 《Science (New York, N.Y.)》2005,307(5710):734-738
Variants of NOD2, an intracellular sensor of bacteria-derived muramyl dipeptide (MDP), increase susceptibility to Crohn's disease (CD). These variants are thought to be defective in activation of nuclear factor kappaB (NF-kappaB) and antibacterial defenses, but CD clinical specimens display elevated NF-kappaB activity. To illuminate the pathophysiological function of NOD2, we introduced such a variant to the mouse Nod2 locus. Mutant mice exhibited elevated NF-kappaB activation in response to MDP and more efficient processing and secretion of the cytokine interleukin-1beta (IL-1beta). These effects are linked to increased susceptibility to bacterial-induced intestinal inflammation and identify NOD2 as a positive regulator of NF-kappaB activation and IL-1beta secretion. 相似文献
9.
Gobert V Gottar M Matskevich AA Rutschmann S Royet J Belvin M Hoffmann JA Ferrandon D 《Science (New York, N.Y.)》2003,302(5653):2126-2130
The Toll-dependent defense against Gram-positive bacterial infections in Drosophila is mediated through the peptidoglycan recognition protein SA (PGRP-SA). A mutation termed osiris disrupts the Gram-negative binding protein 1 (GNBP1) gene and leads to compromised survival of mutant flies after Gram-positive infections, but not after fungal or Gram-negative bacterial challenge. Our results demonstrate that GNBP1 and PGRP-SA can jointly activate the Toll pathway. The potential for a combination of distinct proteins to mediate detection of infectious nonself in the fly will refine the concept of pattern recognition in insects. 相似文献
10.
11.
Odenbreit S Püls J Sedlmaier B Gerland E Fischer W Haas R 《Science (New York, N.Y.)》2000,287(5457):1497-1500
The Gram-negative bacterium Helicobacter pylori is a causative agent of gastritis and peptic ulcer disease in humans. Strains producing the CagA antigen (cagA(+)) induce strong gastric inflammation and are strongly associated with gastric adenocarcinoma and MALT lymphoma. We show here that such strains translocate the bacterial protein CagA into gastric epithelial cells by a type IV secretion system, encoded by the cag pathogenicity island. CagA is tyrosine-phosphorylated and induces changes in the tyrosine phosphorylation state of distinct cellular proteins. Modulation of host cells by bacterial protein translocation adds a new dimension to the chronic Helicobacter infection with yet unknown consequences. 相似文献
12.
13.
结瘤因子(脂壳寡糖,lipo-chito-oligosaccharides,LCOs)是根瘤菌在宿主植物根系分泌的类黄酮的作用下,合成并分泌的一类多糖信号分子,在根瘤菌与植物的共生结瘤过程中起重要作用。结瘤因子通过一定的机制感知,与某种特定受体(结瘤因子结合蛋白)结合,通过结瘤因子激活的信号转导途径如Ca2 介导的信号转导途径或磷酸类脂信号转导途径,诱导宿主植物的一系列反应,如根毛质膜去极化、皮层细胞分裂和结瘤素基因表达等。同时,结瘤因子的感知与信号转导也受一定基因和反馈机制调控。就豆科植物根瘤菌结瘤因子感知机制、信号转导途径及反馈调控等方面的研究进展进行了全面阐述。 相似文献
14.
Thoma-Uszynski S Stenger S Takeuchi O Ochoa MT Engele M Sieling PA Barnes PF Rollinghoff M Bolcskei PL Wagner M Akira S Norgard MV Belisle JT Godowski PJ Bloom BR Modlin RL 《Science (New York, N.Y.)》2001,291(5508):1544-1547
The mammalian innate immune system retains from Drosophila a family of homologous Toll-like receptors (TLRs) that mediate responses to microbial ligands. Here, we show that TLR2 activation leads to killing of intracellular Mycobacterium tuberculosis in both mouse and human macrophages, through distinct mechanisms. In mouse macrophages, bacterial lipoprotein activation of TLR2 leads to a nitric oxide-dependent killing of intracellular tubercle bacilli, but in human monocytes and alveolar macrophages, this pathway was nitric oxide-independent. Thus, mammalian TLRs respond (as Drosophila Toll receptors do) to microbial ligands and also have the ability to activate antimicrobial effector pathways at the site of infection. 相似文献
15.
黏细菌的筛选及其抗菌活性的初步分析 总被引：1，自引：0，他引：1
为了从黏细菌中筛选生物活性物质,以兔粪、腐木为原料,采用选择培养基、加热、冷冻等方法分离到3株黏细菌;重点研究了1号菌,发现1号菌胞外物、胞内物均具有抗菌活性,且抗菌谱不同,其中胞外物对G+细菌有较强的抑菌作用,胞内物对部分G+细菌及G-细菌有抑菌作用,两者对真菌均无抑菌作用。将1号菌胞外物进行薄层层析和硅胶柱层析,得到了抑制放线菌生长的单一组分。 相似文献
16.
In determining the mechanism of neutrophil elastase (NE)-mediated killing of Escherichia coli, we found that NE degraded outer membrane protein A (OmpA), localized on the surface of Gram-negative bacteria. NE killed wild-type, but not OmpA-deficient, E. coli. Also, whereas NE-deficient mice had impaired survival in response to E. coli sepsis, as compared to wild-type mice, the presence or absence of NE had no influence on survival in response to sepsis that had been induced with OmpA-deficient E. coli. These findings define a mechanism of nonoxidative bacterial killing by NE and point to OmpA as a bacterial target in host defense. 相似文献
17.
Nodulation signaling in legumes requires NSP2, a member of the GRAS family of transcriptional regulators 总被引：1，自引：0，他引：1
Kaló P Gleason C Edwards A Marsh J Mitra RM Hirsch S Jakab J Sims S Long SR Rogers J Kiss GB Downie JA Oldroyd GE 《Science (New York, N.Y.)》2005,308(5729):1786-1789
Rhizobial bacteria enter a symbiotic interaction with legumes, activating diverse responses in roots through the lipochito oligosaccharide signaling molecule Nod factor. Here, we show that NSP2 from Medicago truncatula encodes a GRAS protein essential for Nod-factor signaling. NSP2 functions downstream of Nod-factor-induced calcium spiking and a calcium/calmodulin-dependent protein kinase. We show that NSP2-GFP expressed from a constitutive promoter is localized to the endoplasmic reticulum/nuclear envelope and relocalizes to the nucleus after Nod-factor elicitation. This work provides evidence that a GRAS protein transduces calcium signals in plants and provides a possible regulator of Nod-factor-inducible gene expression. 相似文献
18.
为了确定新疆喀什巴楚县某羊场的羊只出现体温升高、精神沉郁、食欲废绝、咳嗽、喘气、呼吸困难等病因,本研究以病变肺脏组织为研究对象,采用常规细菌培养法、细菌形态学观察和PCR鉴定及PCR分型鉴定确定分离菌株的血清型,然后进行分离株的药敏实验和小鼠致病性实验。结果显示：从病变肺脏组织中分离到1株灰白色、透明、两端钝圆、呈单个或成对排列的革兰氏阴性球杆菌;PCR鉴定及PCR分型鉴定结果显示该分离菌株为血清型为A2型的溶血性曼氏杆菌;分离菌株对替米考星、乳酸环丙沙星高度敏感,对氟本尼考、头孢拉定、盐酸林可霉素、克林霉素、硫酸庆大霉素中度敏感,对硫酸阿米卡星、头孢曲松钠、左氧氟沙星、阿奇霉素不敏感;小鼠致病性实验中18h后小鼠陆续死亡,说明该分离菌株对健康小鼠有一定的致病能力。 相似文献
19.
20.
综述了华癸中生根瘤菌(Mesorhizobium huakuii)遗传多样性、质粒多样性、质粒的功能、结瘤因子、结瘤基因、胞外多糖等方面的研究进展。这类菌只能在紫云英上结瘤,1997年并入Mesorhizobium。选取大量菌株进行REP-PCR、16S和23S rDNAPCR-RFLP等分析,揭示其分为16种16S rDNA基因型。选用不同16S rDNA基因型的部分代表菌株进行部分16S rDNA测序。能够在紫云英上结瘤的根瘤菌可以分为2个类群。表明这类菌具有遗传多样性,存在不同的种。它们多数含共生质粒,共生质粒定位于最大或次大质粒上,质粒数1~5个不等,其分子量范围在53~906 kb之间。质粒缺失菌株表现为不结瘤(Nod-)和结瘤而不固氮(Nod ,Nif-)。某些质粒缺失还影响LPS合成、抗酸性、竞争结瘤能力。其结瘤因子能诱导紫云英根毛变形,它们的结瘤因子结构类似于苜蓿根瘤菌的结瘤因子。它们的结瘤基因具独特性,nodA与nodBC分隔一定距离,且具有保守性。它们产生的胞外多糖在侵染结瘤过程中发挥重要作用。 相似文献