Effect of curcumin on aspergillus parasiticus growth and expression of major genes involved in the early and late stages of aflatoxin biosynthesis

The effect of curcumin as a natural safe compound with different biological activities was examined on fungal growth and aflatoxin production in Aspergillus parasiticus NRRL 2999. The fungus was cultured in presence of serial two-fold concentrations of curcumin [125-2000 micro g/ml] in yeast extract sucrose broth for 3 days at 28°C. Mycelia dry weight was determined as an index of fungal growth, while aflatoxin production was assessed by high performance liquid chromatography [HPLC]. The expression of ver-1, nor-1, pksA, omtA and aflR genes in aflatoxin biosynthetic pathway was evaluated by real time PCR. Curcumin strongly inhibited aflatoxin B1 production in the range of 26.6 to 94.9% by serial two-fold concentrations from 125 to 2000 micro g/ml. Fungal growth was also inhibited by the compound in the range of 34.0 to 60.8%. Analysis of the expression of aflatoxin pathway genes by real time PCR showed that curcumin inhibited the expression of ver-1, nor-1, pksA, omtA and aflR genes at concentrations of 250 and 1000 micro g/ml. In concentration of 1000 micro g/ml, gene expression was reduced by 31.3%, 44.6%, 57.1% 110.9% and 286.7% accordingly. Reduction in the expression of aflatoxin biosynthesis genes was significant only for aflR. In ferric reducing ability of plasma [FRAP] assay, curcumin showed strong antioxidant activity at all concentrations tested. Curcumin may be employed successfully as a good candidate in controlling of toxigenic fungal growth on food and feed and subsequent contamination with aflatoxins in practice

Molecular characterization of GTP binding protein gene in dermatophyte pathogen trichophyton rubrum

Trichophyton rubrum [T. rubrum] is an anthropophilic dermatophyte that is distributed worldwide and causes common cutaneous disease such as mycosis. Although several properties of this fungus have been investigated so far, however a few studies were carried out in the field of molecular biology of this fungus. In the present study we tried to identify its molecular characterization of the goanosin three phosphat [GTP] binding protein gene. Pairs of 21 nt primers were designed from highly conserved regions of the gene in other fungi. The primers were utilized in PCR by using isolated genomic DNA tem-plate as well as cytoplasmic RNA of T. rubrum and the PCR and RT-PCR fragments were then sequenced. About 645 nucleotides have been sequenced which encodes a polypeptide with 214 amino acids. Nucleotide sequence comparison in gene data banks [NCBI, NIH] for both the DNA and its deduced amino acid sequence revealed significant homology with GTP binding protein genes and proteins of other eukaryotic cells. The amino acid sequence of the encoded protein was about 64% identical to the sequence of GTP binding protein from other fungi. In summary, we have cloned the first GTP binding protein of dermatophytes and characterized it as a member of this gene family in other eukaryotic cells