PubMed · 4368389
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
S Sen. 1974-03-01. Aflatoxin hepatitis (an experimental comparative study).. https://pubmed.ncbi.nlm.nih.gov/4368389/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Aflatoxin (AF) contamination poses a severe global threat to food and medicinal material safety, yet existing research focuses on terminal AF metabolites while neglecting residual biosynthetic precursors, leading to potential underestimation of contamination risks. In this study, a UPLC-MS/MS method was established for the simultaneous quantification of six AFs and their five precursors in lotus seeds, with optimization of mass spectrum parameters, chromatographic separation conditions, and sample pretreatment. Method validation confirmed linearity (R2 > 0.99), LODs (0.03-0.36 μg/kg), and recoveries (76.53%-120.0%, RSD < 15%). Analysis of 41 natural lotus seed samples revealed a 63.4% AF contamination rate, dominated by B-group AFs, while O-methylsterigmatocystin (OMST) and versicolorin hemiacetal (VOH) were identified as the primary co-residual precursors with co-occurrence rates ≥ 50%. Notably, AFM1 was predominantly detected in natural samples with AFB1 concentrations exceeding 100 μg/kg. Artificial inoculation experiments further demonstrated that sterilization and sealing conditions modulated AF biosynthesis in lotus seeds, with non-sterilized and non-sealed groups showing delayed fungal metabolism and lower toxin accumulation. A significant linear correlation was observed between AFM1 and AFB1 levels (r = 0.94) in infected samples, demonstrating their accumulation levels are coupled with fungal overall metabolic flux. Given the high co-occurrence rate of OMST/VOH with AFB1 in natural samples, their individual and combined toxicities require in-depth investigation. This work deciphers matrix-specific AF dynamics in lotus seeds, supporting regulatory standard refinement (e.g., precursor inclusion) and targeted control (e.g., time-sensitive drying after harvest). Further studies will focus on exploring the molecular mechanisms of substrate-dependent AF synthesis.
AFLR is a Zn2Cys6-type sequence-specific DNA-binding protein that is thought to be necessary for expression of most of the genes in the aflatoxin pathway gene cluster in Aspergillus parasiticus and A. flavus, and the sterigmatocystin gene cluster in A. nidulans. However, it was not known whether AFLR bound to the promoter regions of each of the genes in the cluster. Recently, A. nidulans AFLR was shown to bind to the motif 5'-TCGN5CGA-3'. In the present study, we examined the binding of AFLR to promoter regions of 11 genes in the A. parasiticus cluster. Based on electrophoretic mobility shift assays, the genes nor1, pksA, adhA, norA, ver1, omtA, ordA, and, vbs, had at least one 5'-TCGN5CGA-3' binding site within 200bp of the translation start site, and pksA and ver1 had an additional binding site further upstream. Although the promoter region of avnA lacked this motif, AFLR bound weakly to the sequence 5'-TCGCAGCCCGG-3' at -110bp. One region in the promoter of the divergently transcribed genes aflR/aflJ bound weakly to AFLR even though it contained a site with at most only 7bp of the 5'-TCGN5CGA-3' motif. This partial site may be recognized by a monomeric form of AFLR. Based on a comparison of 16 possible sites, the preferred binding sequence was 5'-TCGSWNNSCGR-3'.
Most genes in the aflatoxin biosynthetic pathway in Aspergillus parasiticus are regulated by the binuclear zinc cluster DNA-binding protein AFLR. The aflR promoter was analyzed in beta-glucuronidase reporter assays to elucidate some of the elements involved in the gene's transcription control. Truncation at 118 bp upstream of the translational start site increased promoter activity 5-fold, while truncation at -100 reduced activity about 20-fold. These findings indicate the presence of an important positive regulatory element between -100 and -118 and a negative regulatory region further upstream. Electrophoretic mobility shift assays on nuclear extracts from A. parasiticus induced for aflatoxin expression suggest that AFLR and another, possibly more abundant, protein bind to the -100/-118 region. Another protein binds to a sequence at position -159 to -164 that matches the consensus binding site for the transcription factor involved in pH-dependent gene regulation, PACC.