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1.
Recently, the prenyltransferase SirD was found to be responsible for the O-prenylation of tyrosine in the biosynthesis of sirodesmin PL in Leptosphaeria maculans. In this study, the behavior of SirD towards phenylalanine/tyrosine and tryptophan derivatives was investigated. Product
formation has been observed with 12 of 19 phenylalanine/tyrosine derivatives. It was shown that the alanine structure attached
to the benzene ring and an electron donor, e.g., OH or NH2, at its para-position are essential for the enzyme activity. Modifications were possible both at the side chain and the benzene ring.
Enzyme products from seven phenylalanine/tyrosine derivatives were isolated and characterized by MS and NMR analyses including
HSQC and HMBC and proven to be O- or N-prenylated derivatives at position C4 of the benzene rings. K
M
values of six selected derivatives were found in the range of 0.10–0.68 mM. Catalytic efficiencies (K
cat/K
M
) were determined in the range of 430–1,110 s−1·M−1 with l-tyrosine as the best substrate. In addition, 7 of 14 tested tryptophan analogs were also accepted by SirD and converted to
C7-prenylated derivatives, which was confirmed by comparison with products obtained from enzyme assays using a 7-dimethylallyltryptophan
synthase 7-DMATS from Aspergillus fumigatus. 相似文献
2.
Hypericum perforatum L. (St. John’s wort) produces a number of phytochemicals having medicinal, anti-microbial, anti-viral and anti-oxidative properties. Plant extracts are generally used for treatment of mild to medium cases of depression. Plant regeneration can be achieved in this species by in vitro culture of a variety of explants. However, there are no reports of regeneration from petal explants. In this report plant regeneration from petal explants of St. John’s wort was evaluated. Petals of various ages were cultured on agarized Murashige and Skoog 1962 (MS) medium supplemented with auxin and cytokinin (kinetin), maintained in the dark and callus and shoot regeneration determined after 28 days. At an auxin to cytokinin ratio of 10:1, callus and shoot formation were induced by all levels of indole-3-acetic acid (IAA), indole-3-butyric acid (IBA) and 1-naphthaleneacetic acid (NAA), while 2,4-dichlorophenoxyacetic acid (2,4-D) induced only callus formation. The optimum level of auxin for shoot regeneration was 1.0 and 0.1 mg/l kinetin, where the regeneration frequency was 100 percent for all three auxins. The highest number of shoots per explant (57.4 and 53.4) was obtained with IAA and IBA, respectively. In the absence of auxin, kinetin levels of 0.1 and 0.25 mg/l induce callus and shoot formation at low frequency but not at lower levels. Callus and shoot formation did not occur in the absence of growth regulators. Petal-derived shoots were successfully rooted on half-strength MS medium without a requirement for exogenous auxin and flowering plants were established under greenhouse conditions. From these results it can be concluded that auxin type is a critical factor for plant regeneration from petal explants of Hypericum perforatum and there is no absolute requirement for high levels of cytokinin. 相似文献
3.
Evidence for the enemy release hypothesis in <Emphasis Type="Italic">Hypericum perforatum</Emphasis> 总被引:4,自引:0,他引:4
The enemy release hypothesis (ERH), which has been the theoretical basis for classic biological control, predicts that the success of invaders in the introduced range is due to their release from co-evolved natural enemies (i.e. herbivores, pathogens and predators) left behind in the native range. We tested this prediction by comparing herbivore pressure on native European and introduced North American populations of Hypericum perforatum (St Johns Wort). We found that introduced populations occur at larger densities, are less damaged by insect herbivory and suffer less mortality than populations in the native range. However, overall population size was not significantly different between ranges. Moreover, on average plants were significantly smaller in the introduced range than in the native range. Our survey supports the contention that plants from the introduced range experience less herbivore damage than plants from the native range. While this may lead to denser populations, it does not result in larger plant size in the introduced versus native range as postulated by the ERH. 相似文献
4.
Objectives
To improve H2 production, the green algae Chlamydomonas reinhardtii cc849 was co-cultured with Azotobacter chroococcum.Results
The maximum H2 production of the co-culture was 350% greater than that of the pure algal cultures under optimal H2 production conditions. The maximum growth and the respiratory rate of the co-cultures were about 320 and 300% of the controls, and the dissolved O2 of co-cultures was decreased 74%. Furthermore, the in vitro maximum hydrogenase activity of the co-culture was 250% greater than that of the control, and the in vivo maximum hydrogenase activity of the co-culture was 1.4-fold greater than that of the control. In addition, the maximum starch content of co-culture was 1400% that of the control.Conclusions
Azotobacter chroococcum improved the H2 production of the co-cultures by decreasing the O2 content and increasing the growth and starch content of the algae and the hydrogenase activity of the co-cultures relative to those of pure algal cultures.5.
6.
Rym Ben Dhiab Hatem Ben Ouada Hamadi Boussetta Fabrice Franck Amor Elabed Michel Brouers 《Journal of applied phycology》2007,19(4):293-301
The effect of salt concentration (NaCl) on growth, fluorescence, photosynthetic activities and pigment content of the cyanobacterium
Arthrospira platensis has been investigated over 15 days. It has been observed that high NaCl concentration induces an increase of the growth,
photosynthetic efficiency (α), phycobilin/chlorophyll ratio and a slight decrease of dark respiration and compensation points.
Moreover, high NaCl concentration enhances photosystem II (PSII) activity compared to photosystem I (PSI). Results show that
the phycobilin-PSII energy transfer compared to the chlorophyll-PSII (F695,600/F695,440) increases. However, data obtained about the maximal efficiency of PSII photochemistry are controversial. Indeed, the Fv/Fm
ratio decreases in salt adapted cultures, while at the same time the trapping flux per PSII reaction center (TR0/RC) and the probability of electron transport beyond QA (0) remain unchanged at the level of the donor and the acceptor sites of PSII. This effect can be attributed to the interference
of phycobilin fluorescence with Chl a when performing polyphasic transient measurements. 相似文献
7.
8.
Cytochrome c
6
, (cyt c
6) a soluble monoheme electron transport protein, was isolated and characterized from the chlorophyll d-containing cyanobacterium Acaryochoris marina, the type strain MBIC11017. The protein was purified using ammonium sulfate precipitation, ion exchange and gel filtration
column chromatography, and fast performance liquid chromatography. Its molecular mass and pI have been determined to be 8.87 kDa
and less than 4.2, respectively, by mass spectrometry and isoelectrofocusing (IEF). The protein has an alpha helical structure
as indicated by CD (circular dichroism) spectroscopy and a reduction midpoint potential (E
m) of +327 mV versus the normal hydrogen electrode (NHE) as determined by redox potentiometry. Its potential role in electron
transfer processes is discussed. 相似文献
9.
Morales M Arancibia J Lemus M Silva J Gentina JC Aroca G 《Biotechnology letters》2011,33(11):2141-2145
Sulfolobus metallicus is a hyperthermophilic and chemolithoautotrophic archaeon that uses elemental sulfur as an energy source. Its ability to
oxidize H2S was measured either in the presence or absence of elemental sulphur, showing its ability for using both as an energy source.
A biotrickling filter was set up and a biofilm of S. metallicus was established over the support. The maximum removal capacity of the biotrickling filter reached at 55°C was 40 g S/m3h for input loads higher than 70 g S/m3h. Thus, S. metallicus can be used in a biofiltration system for the treatment of waste gas emissions at high temperatures contaminated with H2S. 相似文献
10.
Two repeated DNA sequences isolated from a partial genomic DNA library of Helianthus annuus, p HaS13 and p HaS211, were shown to represent portions of the int gene of a Ty3 /gypsy retroelement and of the RNase-Hgene of a Ty1 /copia retroelement, respectively. Southern blotting patterns obtained by hybridizing the two probes to BglII- or DraI-digested genomic DNA from different Helianthus species showed p HaS13 and p HaS211 were parts of dispersed repeats at least 8 and 7 kb in length, respectively, that were conserved in all species studied. Comparable hybridization patterns were obtained in all species with p HaS13. By contrast, the patterns obtained by hybridizing p HaS211 clearly differentiated annual species from perennials. The frequencies of p HaS13- and p HaS211-related sequences in different species were 4.3x10(4)-1.3x10(5) copies and 9.9x10(2)-8.1x10(3) copies per picogram of DNA, respectively. The frequency of p HaS13-related sequences varied widely within annual species, while no significant difference was observed among perennial species. Conversely, the frequency variation of p HaS211-related sequences was as large within annual species as within perennials. Sequences of both families were found to be dispersed along the length of all chromosomes in all species studied. However, Ty3 /gypsy-like sequences were localized preferentially at the centromeric regions, whereas Ty1/ copia-like sequences were less represented or absent around the centromeres and plentiful at the chromosome ends. These findings suggest that the two sequence families played a role in Helianthusgenome evolution and species divergence, evolved independently in the same genomic backgrounds and in annual or perennial species, and acquired different possible functions in the host genomes. 相似文献
11.
Jana Koperdáková Hedviga Komarovská Ján Košuth Annalisa Giovannini Eva Čellárová 《Acta Physiologiae Plantarum》2009,31(2):351-358
Hairy root-regenerated clones of Hypericum perforatum L. grown in vitro similarly to those successfully adapted to ex vitro conditions showed phenotype features typical for plants
transformed with Agrobacterium rhizogenes T-DNA. These included reduced apical dominance, increased branching, dwarfing and reduced fertility. Transgenic clones differed
in ability to develop root system as a necessary condition for transfer to the soil. One of the profiling characters, capability
of hypericin biosynthesis was altered as well. Dark glands as the sites of hypericin accumulation and/or synthesis exhibited
significantly higher densities on both, leaves and petals of transgenic clones comparing to controls. In the genome of transgenic
clones, rolABC genes were detected. Both clones harboured similar copy number of individual rol genes. However, copy numbers descended from rolA to rolC gene in both clones. 相似文献
12.
G. S. Minyuk E. S. Chelebieva I. N. Chubchikova N. V. Dantsyuk I. V. Drobetskaya E. G. Sakhon O. B. Chivkunova K. A. Chekanov E. S. Lobakova R. A. Sidorov A. E. Solovchenko 《Russian Journal of Plant Physiology》2016,63(4):566-574
We studied effects of рН and СО2 enrichment on the physiological condition and biochemical composition of a carotenogenic microalga Coelastrella (Scotiellopsis Vinatzer) rubescens Kaufnerová et Eliás (Scenedesmaceae, Sphaeropleales, Chlorophyceae), a promising source of natural astaxanthin. The microalga was grown at a constant pH (5, 6, 7 or 8) maintained by direct СО2 injection. The air-sparged culture served as the control. Cell division rate and size, dry biomass productivity, the rates of nitrogen and phosphorus uptake as well as photosynthetic pigment and total lipid content and fatty acid composition were followed. С. rubescens possessed a narrow-range рН tolerance (the optimum рН 6–7). Under these conditions, the highest values of the maximum (1.0–1.1 1/day) and average (0.3–0.35 1/day) specific growth rate, chlorophyll а (4.8–4.9%) and total carotenoid dry weight percentages (1.7–1.8%) were recorded. Cell lipid fatty acid unsaturation index (1.851) and polyunsaturated fatty acid percentage (36–39%) and С18:3 ω3/С18:1 ω9 ratio (3.8–4.5) were also the highest under these conditions. A decline of рН to 5 brought about severe stress manifesting itself as a cell division cessation, photosynthetic apparatus reduction, two-fold increase in cell volume, accumulation of dry weight and lipids and a considerable decline in fatty acid unsaturation. Cultivation of С. rubescens without СО2 enrichment resulted in a rapid alkalization of the medium to рН 9.5–10.5 impairing the physiological condition of the cells. Reasons of the deteriorative effects of suboptimal pH values on the physiological condition of C. rubescens are discussed. 相似文献
13.
Patocchi A Bigler B Koller B Kellerhals M Gessler C 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2004,109(5):1087-1092
Reports from several European countries of the breakdown of the Vf resistance, the most frequently used source of resistance in breeding programs against apple scab, emphasize the urgency of diversifying the basis of apple scab resistance and pyramiding different apple scab resistances with the use of their associated molecular markers. GMAL 2473 is an apple scab resistant selection thought to carry the resistance gene Vr. We report the identification by BSA of three AFLP markers and one RAPD marker associated with the GMAL 2473 resistance gene. SSRs associated with the resistance gene were found by (1) identifying the linkage group carrying the apple scab resistance and (2) testing the SSRs previously mapped in the same region. One such SSR, CH02c02a, mapped on linkage group 2, co-segregates with the resistance gene. GMAL 2473 was tested with molecular markers associated with other apple scab resistance genes, and accessions carrying known apple scab resistance genes were tested with the SSR linked to the resistance gene found in GMAL 2473. The results indicate that GMAL 2473 does not carry Vr, and that a new apple scab resistance gene, named Vr
2, has been identified. 相似文献
14.
Ryan M. Taylor Larry Sallans Laurie K. Frankel Terry M. Bricker 《Photosynthesis research》2018,137(1):141-151
The cytochrome b 6 f complex of oxygenic photosynthesis produces substantial levels of reactive oxygen species (ROS). It has been observed that the ROS production rate by b 6 f is 10–20 fold higher than that observed for the analogous respiratory cytochrome bc1 complex. The types of ROS produced (O2??, 1O2, and, possibly, H2O2) and the site(s) of ROS production within the b 6 f complex have been the subject of some debate. Proposed sources of ROS have included the heme b p , PQ p ?? (possible sources for O2??), the Rieske iron–sulfur cluster (possible source of O2?? and/or 1O2), Chl a (possible source of 1O2), and heme c n (possible source of O2?? and/or H2O2). Our working hypothesis is that amino acid residues proximal to the ROS production sites will be more susceptible to oxidative modification than distant residues. In the current study, we have identified natively oxidized amino acid residues in the subunits of the spinach cytochrome b 6 f complex. The oxidized residues were identified by tandem mass spectrometry using the MassMatrix Program. Our results indicate that numerous residues, principally localized near p-side cofactors and Chl a, were oxidatively modified. We hypothesize that these sites are sources for ROS generation in the spinach cytochrome b 6 f complex. 相似文献
15.
Studying Pneumocystis has proven to be a challenge from the perspective of propagating a significant amount of the pathogen in a facile manner.
The study of several fungal pathogens has been aided by the use of invertebrate model hosts. Our efforts to infect the invertebrate
larvae Galleria
mellonella with Pneumocystis proved futile since P. murina neither caused disease nor was able to proliferate within G. mellonella. It did, however, show that the pathogen could be rapidly cleared from the host. 相似文献
16.
Noel H. Holmgren 《Brittonia》2018,70(1):115-139
A revision of Penstemon sect. Saccanthera subsect. Serrulati includes a new species (P. salmonensis), a new variety (P. triphyllus var. infernalis), and the elevation of a subspecies to species (P. curtiflorus), bringing the total number of species to eight, which are keyed and described, complete with nomenclature and type citations. 相似文献
17.
Tocci N Simonetti G D'Auria FD Panella S Palamara AT Valletta A Pasqua G 《Applied microbiology and biotechnology》2011,91(4):977-987
Hypericum perforatum is a well-known medicinal plant which contains a wide variety of metabolites, including xanthones, which have a wide range
of biological properties, including antifungal activity. In the present study, we evaluated the capability of roots regenerated
from calli of H. perforatum subsp. angustifolium to produce xanthones. Root biomass was positively correlated with the indole-3-butyric acid concentration, whereas a concentration
of 1 mg l−1 was the most suitable for the development of roots. High auxin concentrations also inhibited xanthone accumulation. Xanthones
were produced in large amounts, with a very stable trend throughout the culture period. When the roots were treated with chitosan,
the xanthone content dramatically increased, peaking after 7 days. Chitosan also induced a release of these metabolites into
the culture. The maximum accumulation (14.26 ± 0.62 mg g−1 dry weight [DW]) and release (2.64 ± 0.13 mg g−1 DW) of xanthones were recorded 7 days after treatment. The most represented xanthones were isolated, purified, and spectroscopically
characterized. Antifungal activity of the total root extracts was tested against a broad panel of human fungal pathogen strains
(30 Candida species, 12 Cryptococcus neoformans, and 16 dermatophytes); this activity significantly increased when using chitosan. Extracts obtained after 7 days of chitosan
treatment showed high antifungal activity (mean minimum inhibitory concentration of 83.4, 39.1, and 114 μg ml−1 against Candida spp., C. neoformans, and dermatophytes, respectively). Our results suggest that root cultures can be considered as a potential tool for large-scale
production of extracts with stable quantities of xanthones. 相似文献
18.
Liping Xing Li Gao Qiguang Chen Haiyan Pei Zhaocan Di Jin Xiao Haiyan Wang Lulin Ma Peidu Chen Aizhong Cao Xiue Wang 《Plant Growth Regulation》2018,84(3):561-571
Wheat Fusarium Head Blight (FHB), mainly caused by Fusarium graminearum (F.g), is a destructive fungal disease worldwide. FHB can not only cause considerable reduction in yield, but more seriously, can contaminate grain by trichothecene toxins released by the fungus. Here, we report new insights into the function and underlying mechanisms of a UDP-glycosyltransferase gene, Ta-UGT 3 , that is involved in FHB resistance in wheat. In our previous study, Ta-UGT 3 was found to enhance host tolerance against deoxynivalenol (DON) in Arabidopsis. In this study, four transgenic lines over-expressing Ta-UGT 3 in a FHB highly susceptible wheat variety, Alondra’s, were obtained and characterized. 3 years of assays using single floret inoculation with F.g indicated that all four transgenic lines exhibited significantly enhanced type II resistance to FHB and less DON accumulation in the grains compared to the untransformed control. Histological observation using GFP labelled F.g was in agreement with the above test results since over-expression of Ta-UGT 3 dramatically inhibited expansion of F.g. To explore the putative mechanism of resistance mediated by Ta-UGT 3 , microarray analysis, qRT-PCR and hormone measurements were performed. Microarray analysis showed that DON up-regulated genes, such as TaNPR1, in the susceptible control, and down-regulated genes in F.g inoculated transgenic lines, while qRT-PCR showed that some defence related genes were up-regulated in F.g inoculated transgenic lines. Ta-UGT 3 over-expression also changed the contents of the endogenous hormones SA and JA in the spikes. These data suggest that Ta-UGT 3 positively regulates the defence responses to F.g, perhaps by regulating defence-related and DON-induced downstream genes. 相似文献
19.
20.
Mattis Kupferschmid Moyira Osny Aquino-Gil Hosam Shams-Eldin Jörg Schmidt Nao Yamakawa Frédéric Krzewinski Ralph T. Schwarz Tony Lefebvre 《Malaria journal》2017,16(1):485