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101.
Co-expression of 15 contiguous genes delineates a fumonisin biosynthetic gene cluster in Gibberella moniliformis 总被引:4,自引:0,他引:4
Proctor RH Brown DW Plattner RD Desjardins AE 《Fungal genetics and biology : FG & B》2003,38(2):237-249
Fumonisins are mycotoxins produced by the maize pathogen Gibberella moniliformis and are associated with cancer in rodents. In this study, we determined the nucleotide sequence of a 75-kb region of G. moniliformis DNA and identified 18 heretofore undescribed genes flanking a cluster of five previously identified fumonisin biosynthetic (FUM) genes. Ten of the newly identified genes downstream of the cluster were coregulated with FUM genes and exhibited patterns of expression that were correlated with fumonisin production. BLASTX analyses indicated that the predicted functions of proteins encoded by the 10 genes were consistent with activities expected for fumonisin biosynthesis or self-protection. These data indicate that the 10 newly identified genes and the previously identified FUM genes constitute a fumonisin biosynthetic gene cluster. Disruption of two of the new genes, encoding longevity assurance factors, had no apparent effect on fumonisin production, but disruption of a third, encoding an ABC transporter, had a subtle effect on ratios of fumonisins produced. 相似文献
102.
Variable chlorophyll a (Chl a) fluorescence is composed of a photochemical and a thermal phases of similar amplitudes. The photochemical phase can be induced
by a saturating single turnover flash (STF) and reflects the reduction of the Photosystem II (PS II) QA primary electron acceptor. The thermal phase requires multiple turnover flash (MTF) and is somehow related to the reduction
of the plastoquinone (PQ) molecules. This article aimed to determine the relative contributions of the QB-bound and the free oxidized PQ molecules to the thermal phase of Chl a fluorescence. We thus measured the interactive effects of exogenous PQ (PQex), of an inhibitor (DCMU) acting at the QB site of PS II and of an artificial quencher, 2-methyl-1,4-naphtoquinone, on Chl a fluorescence levels induced by STF (FF) and MTF (FM) in spinach thylakoids. We observed that: (1) the incorporation of PQex in thylakoids stimulated photosynthetic electron
transport but barely affected FF and FM in the absence of DCMU; (2) DCMU significantly increased the amplitude of FF but slightly quenched FM; (3) 2-methyl-1,4-naphtoquinone quenched FM to a larger-extent than FF; (4) DCMU increased the quenching effects of PQex on FF and FM and also, of methyl-1,4-naphtoquinone on FF. These results indicate that: (1) the QB-bound and the free PQ molecules contribute to about 56% and 25%, respectively, to the thermal phase Chl a fluorescence in dark-adapted thylakoids; and (2) the thermal phase of Chl a fluorescence is more susceptible than the photochemical phase to the non-photochemical quenching effect of oxidized quinones.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
103.
Endoplasmic reticulum-mediated phagocytosis is a mechanism of entry into macrophages 总被引:36,自引:0,他引:36
Gagnon E Duclos S Rondeau C Chevet E Cameron PH Steele-Mortimer O Paiement J Bergeron JJ Desjardins M 《Cell》2002,110(1):119-131
Phagocytosis is a key aspect of our innate ability to fight infectious diseases. In this study, we have found that fusion of the endoplasmic reticulum (ER) with the macrophage plasmalemma, underneath phagocytic cups, is a source of membrane for phagosome formation in macrophages. Successive waves of ER become associated with maturing phagosomes during phagolysosome biogenesis. Thus, the ER appears to possess unexpectedly pluripotent fusion properties. ER-mediated phagocytosis is regulated in part by phosphatidylinositol 3-kinase and used for the internalization of inert particles and intracellular pathogens, regardless of their final trafficking in the host. In neutrophils, where pathogens are rapidly killed, the ER is not used as a major source of membrane for phagocytosis. We propose that intracellular pathogens have evolved to adapt and exploit ER-mediated phagocytosis to avoid destruction in host cells. 相似文献
104.
Brousseau D Desjardins JF Jasmin G Dumont L 《Canadian journal of physiology and pharmacology》2002,80(3):218-225
Although the influence of the adrenergic system has been studied in the presence of heart failure, controversies still exist. Since cyclooxygenase derivatives appear to modulate coronary and cardiac adaptation in the failing heart, we hypothesized that cyclooxygenase derivatives may participate in the altered adrenergic responses in this situation. Isolated hearts from cardiomyopathic (UM-X7.1 subline) and normal hamsters, aged > 240 days, were utilized. Coronary and cardiac response to alpha1-, beta1-, and beta2-adrenergic stimulations was observed before and after pretreatment with indomethacin, a cyclooxygenase inhibitor. Reduction of coronary flow elicited by alpha1-adrenergic stimulation was unchanged in the presence of heart failure, while beta1- and beta2-induced vasodilatations were reduced. Inotropic response to alpha1 and beta1 stimulations were also reduced in failing hearts, while beta2-adrenergic action was unchanged. Pretreatment with indomethacin exacerbated coronary flow reduction observed with alpha1 stimulation in failing hearts only. Beta2-induced coronary vasodilatation and inotropic response to alpha1 and beta2 stimulations were impaired similarly in the presence of indomethacin in normal and failing hearts. The results suggest a complex interaction between adrenergic and cyclooxygenase activation. 相似文献
105.
Fumonisin production and other traits of Fusarium moniliforme strains from maize in northeast Mexico.
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Strains of Fusarium moniliforme from maize seed collected in four fields in northeast Mexico were tested for fumonisin production in culture, for sexual compatibility, and for vegetative compatibility by using non-nitrate-utilizing mutants. The test results indicate that a diverse population of fumonisin-producing strains of F. moniliforme (Gibberella fujikuroi) mating population A predominates and that a potential exists for production of fumonisins in Mexican maize. 相似文献
106.
107.
Trichothecene biosynthesis in Fusarium species: chemistry, genetics, and significance. 总被引:9,自引:0,他引:9
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Several species of the genus Fusarium and related fungi produce trichothecenes which are sesquiterpenoid epoxides that act as potent inhibitors of eukaryotic protein synthesis. Interest in the trichothecenes is due primarily to their widespread contamination of agricultural commodities and their adverse effects on human and animal health. In this review, we describe the trichothecene biosynthetic pathway in Fusarium species and discuss genetic evidence that several trichothecene biosynthetic genes are organized in a gene cluster. Trichothecenes are highly toxic to a wide range of eukaryotes, but their specific function, if any, in the survival of the fungi that produce them is not obvious. Trichothecene gene disruption experiments indicate that production of trichothecenes can enhance the severity of disease caused by Fusarium species on some plant hosts. Understanding the regulation and function of trichothecene biosynthesis may aid in development of new strategies for controlling their production in food and feed products. 相似文献
108.
Photosynthesis and phosphoenolpyruvate carboxylase activity were investigated in 5, 10 and 28 day-old micropropagated strawberry plantlets (Fragaria x ananassa Duch. cv Kent) rooted in vitro with different levels of sucrose (0, 1, 3 and 5%) on cellulose plugs (Sorbarods). The photosynthetic capability was influenced by the level of sucrose in the culture medium with the largest rates of photosynthesis corresponding to the cultures with 0 and 1% sucrose. The apparent quantum yield and the ratio of variable fluorescence to maximum fluorescence were also reduced in plantlets cultured with 3 or 5% sucrose as compared to those with 0 or 1%. Phosphoenolpyruvate carboxylase activity was largest 5 and 10 days after the onset of culture and decreased in the absence of sucrose in the culture medium. At 28 days after the onset of culture, the activity of this carboxylating enzyme was lower than at the beginning of culture and independent of the concentration of sucrose in the culture medium. Phosphoenolpyruvate carboxylase appears to be an important carboxylating enzyme in micropropagated plantlets. 相似文献
109.
Virus-like spherical particles found in laboratory-reared citrus red mites but not in field populations were independent of the pathogenic virus affecting this species. Three sizes of particles are present: 18-nm spheres occuring in crystalline array, and 30- and 37-nm spheres. The particles possess antigenic properties and contain RNA. 相似文献
110.