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101.
Ktia de Lima Nechet Robert Weingart Barreto Eduardo S. G. Mizubuti 《Biological Control》2004,30(3):556-565
Sphaceloma poinsettiae, a scab-causing fungus that attacks wild poinsettia (Euphorbia heterophylla) was evaluated as a mycoherbicide. Plants representing nine different E. heterophylla accessions were tested and variable resistance levels to 10 different isolates of S. poinsettiae were observed. One isolate was selected based on its high aggressiveness; it caused scab that led to stem-girdling in the majority of plants belonging to most wild poinsettia accessions. Plants inoculated with conidial suspension developed low disease severity; suspensions of mycelial fragments caused higher disease severity. Viability of mycelium declined rapidly either in storage under room temperature or at 4 °C. After 25 days, 60% of mycelial fragments kept in distilled water at 4 °C or in 35% sterile sucrose solution germinated. Cultures of S. poinsettiae were capable of growing at temperatures ranging from 10 to 30 °C (maximum growth at 25 °C) whereas the mycelial fragments germinated at 20–30 °C. The highest mycelial yield occurred in potato-dextrose broth after culturing for 12 days at 168 rpm at room temperature. A host-range test involving 37 plant species in addition to wild poinsettia indicated that S. poinsettiae is highly specific to E. heterophylla. The viability of S. poinsettiae as a mycoherbicide depends on the development of suitable mass production, formulation, and inoculum preservation methods. On several occasions, this fungus has been observed to cause devastating epidemics in the field on this host; therefore, it should be considered a potential biocontrol agent of wild poinsettia. 相似文献
102.
103.
The changes in thermoluminescence (TL) signals induced by short-term ozone exposure of leaves are characterized by a down-shift
of the peak-temperature of the TLB-band and an increase of a TL band at 55°C. We investigated the relationship of these changes
to photosystem 2 (PS2) photochemistry. The changes were not only detectable in the presence of ozone, but also after irradiation
of dark-adapted leaves and after aging of irradiated detached leaf segments. The opposite effect on TL, an up-shift of the
peak-temperature of the B-band and the decrease of the intensity of the band at 55°C were found after infiltration of leaves
with nigericin, antimycin A, and diphenyleneiodonium chloride (DPI). Propyl gallate down-shifted the peak-temperature of the
B-band. 2,5-dimethyl-1,4-benzoquinone up-shifted the peak-temperature of the B-band and decreased the intensity of the 55°C
band. The intensity of the 55°C band did not change significantly in the presence of oxygen in comparison to that in nitrogen
atmosphere. It decreased with time of dark adaptation (50% intensity was observed after 3 h of dark adaptation at room temperature),
however, it was reactivated to its initial value (at 5 min of dark adaptation) after 1 single-turnover flash. The 55°C band
was not significantly changed in the presence of DCMU. Thus the ozone-induced band at 55°C is assigned to charge recombination
in PS2. Changes in the electron transport chain at the acceptor side of PS2, probably related to the cyclic electron transport
around photosystem 1 and/or chlororespiration, could play an important role in the increase of the 55°C band and the down-shift
of the B-band. The changes at the acceptor side indicated by TL can be an ex pression of a physiological regulatory mechanism
functional under stress conditions. 相似文献
104.
105.
Blossoms are important sites of infection for Erwinia amylovora, the causal agent of fire blight of rosaceous plants. Before entering the tissue, the pathogen colonizes the stigmatic surface and has to compete for space and nutrient resources within the epiphytic community. Several epiphytes are capable of synthesizing antibiotics with which they antagonize phytopathogenic bacteria. Here, we report that a multidrug efflux transporter, designated NorM, of E. amylovora confers tolerance to the toxin(s) produced by epiphytic bacteria cocolonizing plant blossoms. According to sequence comparisons, the single-component efflux pump NorM is a member of the multidrug and toxic compound extrusion protein family. The corresponding gene is widely distributed among E. amylovora strains and related plant-associated bacteria. NorM mediated resistance to the hydrophobic cationic compounds norfloxacin, ethidium bromide, and berberine. A norM mutant was constructed and exhibited full virulence on apple rootstock MM 106. However, it was susceptible to antibiotics produced by epiphytes isolated from apple and quince blossoms. The epiphytes were identified as Pantoea agglomerans by 16S rRNA analysis and were isolated from one-third of all trees examined. The promoter activity of norM was twofold greater at 18 degrees C than at 28 degrees C. The lower temperature seems to be beneficial for host infection because of the availability of moisture necessary for movement of the pathogen to the infection sites. Thus, E. amylovora might employ NorM for successful competition with other epiphytic microbes to reach high population densities, particularly at a lower temperature. 相似文献
106.
Oliver?Weingart Artur?Nenov Piero?Altoè Ivan?Rivalta Javier?Segarra-Martí Irina?Dokukina Marco?GaravelliEmail author 《Journal of molecular modeling》2018,24(9):271
We present a new version of the simulation software COBRAMM, a program package interfacing widely known commercial and academic software for molecular modeling. It allows a problem-driven tailoring of computational chemistry simulations with effortless ground and excited-state electronic structure computations. Calculations can be executed within a pure QM or combined quantum mechanical/molecular mechanical (QM/MM) framework, bridging from the atomistic to the nanoscale. The user can perform all necessary steps to simulate ground state and photoreactions in vacuum, complex biopolymer, or solvent environments. Starting from ground-state optimization, reaction path computations, initial conditions sampling, spectroscopy simulation, and photodynamics with deactivation events, COBRAMM is designed to assist in characterization and analysis of complex molecular materials and their properties. Interpretation of recorded spectra range from steady-state to time-resolved measurements. Various tools help the user to set up the system of interest and analyze the results. 相似文献
107.
Dott. CL. CH. Mathon 《Plant biosystems》2013,147(2-3):345-356
Resumé Chez les Blés branchus de l'espèce «turgidum» (Triticum turgidum compositum), il existe des sortes à thermostade plutôt froid (Blés d'hiver ou de semi-hiver) et des sortes à thermostade chaud, tièe ou «indifférent» (Blés de printemps). Les Blés branchus de l'espèce «turgidum» apparaissent comme étant des plantes à photostade de jour long. La plus ou moins grande rapidité de l'accomplissement du photostade, par rapport à la rapidité de l'assimilation des matières plastiques, détermine la structure, — non ramifiée ou ramifiée — de l'épi. 相似文献
108.
SGO1 but not SGO2 is required for maintenance of centromere cohesion in Arabidopsis thaliana meiosis
L. Zamariola N. De Storme CL. Tiang S. J. Armstrong F. C. H. Franklin D. Geelen 《Sexual plant reproduction》2013,26(3):197-208
Shugoshin is a protein conserved in eukaryotes and protects sister chromatid cohesion at centromeres in meiosis. In our study, we identified the homologs of SGO1 and SGO2 in Arabidopsis thaliana. We show that AtSGO1 is necessary for the maintenance of centromere cohesion in meiosis I since atsgo1 mutants display premature separation of sister chromatids starting from anaphase I. Furthermore, we show that the localization of the specific centromeric cohesin AtSYN1 is not affected in atsgo1, suggesting that SGO1 centromere cohesion maintenance is not mediated by protection of SYN1 from cleavage. Finally, we show that AtSGO2 is dispensable for both meiotic and mitotic cell progression in Arabidopsis. 相似文献
109.
Daniel Pletzer Corinne Lafon Yvonne Braun Thilo K?hler Malcolm G. P. Page Michael Mourez Helge Weingart 《PloS one》2014,9(10)
In this study, we show that the dppBCDF operon of Pseudomonas aeruginosa PA14 encodes an ABC transporter responsible for the utilization of di/tripeptides. The substrate specificity of ABC transporters is determined by its associated substrate-binding proteins (SBPs). Whereas in E. coli only one protein, DppA, determines the specificity of the transporter, five orthologous SBPs, DppA1–A5 are present in P. aeruginosa. Multiple SBPs might broaden the substrate specificity by increasing the transporter capacity. We utilized the Biolog phenotype MicroArray technology to investigate utilization of di/tripeptides in mutants lacking either the transport machinery or all of the five SBPs. This high-throughput method enabled us to screen hundreds of dipeptides with various side-chains, and subsequently, to determine the substrate profile of the dipeptide permease. The substrate spectrum of the SBPs was elucidated by complementation of a penta mutant, deficient of all five SBPs, with plasmids carrying individual SBPs. It became apparent that some dipeptides were utilized with different affinity for each SBP. We found that DppA2 shows the highest flexibility on substrate recognition and that DppA2 and DppA4 have a higher tendency to utilize tripeptides. DppA5 was not able to complement the penta mutant under our screening conditions. Phaseolotoxin, a toxic tripeptide inhibiting the enzyme ornithine carbamoyltransferase, is also transported into P. aeruginosa via the DppBCDF permease. The SBP DppA1, and with much greater extend DppA3, are responsible for delivering the toxin to the permease. Our results provide a first overview of the substrate pattern of the ABC dipeptide transport machinery in P. aeruginosa. 相似文献
110.
Braz Tavares da Hora Júnior Davi Mesquita de Macedo Robert Weingart Barreto Harry C. Evans Carlos Raimundo Reis Mattos Luiz Antonio Maffia Eduardo S. G. Mizubuti 《PloS one》2014,9(8)