1,721,049 research outputs found
Molecular cloning of glutamate dehydrogenase genes of Nicotiana plumbaginifolia: structure analysis and regulation of their expresion by physiological and stress conditions
No full textTwo Nicotiana plumbaginifolia gdh genes (gdhA and gdhB) encoding for NADH dependent
glutamate dehydrogenase (GDH) were isolated by PCR and I-PCR (inverse-PCR) and sequenced.
The coding sequence is interrupted by eight introns that are located in the same positions in both
genes. Computer analysis of the promoter regions of gdhA (650 nt) and gdhB (1800 nt) revealed
several conserved motifs and, for gdhB, the presence of an I-Box element known to have light
dependent regulatory functions in plants. The response of the gdh genes to carbohydrate deprivation
and to ammonium feeding and to various stress conditions (salinity, temperature shifts and heavy
metals) was examined in callus culture. The results clearly showed that the carbohydrate status of
the cell is the main factor affecting gdh genes expression. Stress condition may depress or increase
gdh transcript levels, but theses are not always correlated to the corresponding levels of GDH
activity. Altogether these results point to the existence of multiple levels of regulation
(transcriptional and post-transcriptional) of gdh genes
Effect of 5-fluorouracil on growth and mophogenesis of tissue cultures of Nicotiana sylvestris
No full textDevelopment of a simple and high-throughput method for detecting aflatoxins production in culture media.
No full textAims: To develop a simple, high-throughput and inexpensive procedure to detect and quantify aflatoxins into the culture media of growing mycelia. Methods and Results: Fungal conidia (Aspergillus flavus) were inoculated into the wells of a microplate containing 200mul of different formulations of coconut-derived liquid medium. Time-dependent production of aflatoxins in the culture media was evaluated by a procedure relying on the UV-induced fluorescence emission by the toxin, using a microplate reader. These data were validated by comparison with the outputs of a conventional HPLC-based procedure. Determinations of aflatoxin concentration, according to the fluorimetric procedure, were performed either by withdrawing samples from the plates or by direct 'in situ' readings, the latter method reinforcing the high-throughput feature of the procedure. Fluorescence enhancers (cyclodextrins) did not ameliorate the sensitivity of the procedure to low concentrations of the toxin into the medium. The efficacy of the procedure was also validated by testing the effect on toxin yield of adding an antioxidant agent (alpha-lipoic acid) to the medium. Conclusions: We give evidence that our improved procedure is reliable and suitable to analyse aflatoxin accumulation time course in coconut-derived culture medium. Significance and Impact of the Study: This study shows that our procedure may profitably be used to give insights into the mechanisms of regulation of mycotoxin production and, consequently, to implement different strategies for the containment of aflatoxin contamination of food and feed commodities
Glutamate dehydrogenase specific activity and its isoenzymatic pattern are carbon source dependent in callus cultures of Nicotiana plumbaginifolia.
No full textBiocompetition as a tool to cope with the problem of aflatoxin contamination of food and feed commodities: may phenotype microarray technology contribute to the individuation of "good" competitors?
No full textAspergillus flavus is a well known plant pathogen responsible of economic losses and food safety concern due to the ability of mycotoxin production. Aflatoxin contamination of crops is a significant problem worldwide, and many Countries have set more or less strict limits for mycotoxin presence in feed and food commodities. An interesting strategy to cope with aflatoxin contamination in susceptible crops involves the use of intraspecific competition to interfere with mycotoxin production by the relevant Aspergillus flavus strains. Atoxigenic A. flavus strains (afla-), unable to produce the relevant mycotoxin, have been already used as bio-competitors to decrease aflatoxin accumulation on cotton, maize and peanuts fields. Selecting a strain performing as a strong bio-competitor is not a straightforward task since it depends on previous assessment of various interacting factors conditioning the relative fitness of the strains in a given ecological niche. Reconstruction experiment have been generally performed in laboratory conditions to uncover the biological mechanisms underlying the efficacy of atoxigenic strains in preventing aflatoxin production and/or to give a preliminary indication of strain performance when released in the field.
Our present goal is 1) characterization of A. flavus population colonizing the corn field of the Po valley and 2) setting a strategy for the identification of “good” competitors among afla- strains isolated from the above mentioned A. flavus population. For this purpose we are performing competition experiments in laboratory conditions and designing “high throughput” procedures to test as many as possible environmental conditions that may affect competition efficacy. Moreover, afla- strains are generally considered to be derived from aflatoxin producer strains (afla+) that have lost the capacity to produce the relevant mycotoxin as a result of mutation(s) affecting gene(s) belonging to the Aflatoxin biosynthetic cluster. afla- strains are obviously expected to be altered in one or more steps of secondary metabolism. However the story might be more complex than expected, since regulatory interactions between pathways of primary and secondary metabolism have already been described. In this respect, Phenotype MicroArray technology may represent an additional value for our goal if the specific metabolic features of different afla- strains could be correlated to their competitive ability. In the present study we have performed, as a preliminary approach, experiments to verify if afla+ and afla- strains may be differentiated by the use of the Biolog FF physiological identification kit
Potential of biocontrol agents, antioxidant compounds and natural extracts on aflatoxin containment: a simple and highthroughput procedure
No full textAflatoxin B1 is considered one of the most dangerous mycotoxin for humans and animals health. Moreover severe economic losses may be encountered due to its possible contamination of food and feed during each step of their transformation process (from field to table). Preventing fungal infection/ toxin contamination of crops in the field is considered the preferred strategy to cope with the “aflatoxin risk”.
Biocontrol by competitive inhibition using atoxigenic (afla–) Aspergillus flavus strains has been shown to be an effective method in aflatoxin containment in peanuts, maize and cottonseed(1). Naturally occurring populations of afla– strains are considered reservoirs from which to select the strongest biocompetitors. However, the selection of biocontrol strains is not an easy task, due both to the small amount of afla– strains and to the various environmental conditions that may affect their efficacy in the field(2). High throughput procedures are therefore desirable to screen large amount of isolates in order to identify “good competitors”. Moreover, as field trials required to assess their efficiency are expensive and laborious, reconstruction experiments have been generally performed under laboratory conditions to investigate the biological mechanisms underlying the efficacy of afla– strains in preventing aflatoxin production and/or to give a preliminary indication of strain performance when released in the crops.
We developed a simple and inexpensive fluorescence-based procedure that may be used: 1) to scale-up the screening process(3) and also 2) to increase knowledge on the mechanisms interfering with mycotoxin production during intraspecific competition and 3) to analyze the effect of natural and/or synthetic compounds for their possible effects on aflatoxin biosynthesis.
Here we give a report of our results concerning the evaluation of the potential of afla– strains, colonizing the corn fields of the Po Valley, in reducing aflatoxin accumulation, and show some preliminary evidence that suggest the possible use of antioxidants as part of an additional strategy to contain aflatoxin contamination of food and feed commodities. Conversely the procedure may be used to uncover the presence of antioxidant agents in complex mixtures deriving from natural sources
Isolation and characterization of two cDNA clones encoding for glutamate dehydrogenase in Nicotiana plumbaginifolia
No full textGlucose regulation in Nicotiana plumbaginifolia: variations of glutamate dehydrogenase isoenzymatic patterns
No full textCaratterizzazione dei prodotti della trascrizione e della traduzione in colture di calli di gerbera sottoposte a deprivazione di fonti di carbonio.
No full textRisposta allo stress da deprivazione di fonti di carbonio: modificazioni del metabolismo cellulare e della sintesi proteica in colture di calli di Gerbera jamesonii var. hybrida.
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