ABSTRACT
Argentina is the first popcorn exporting country worldwide. In 1997-1998 harvest season, 40,000 ha were sown with a production of 125,000 tons; 120,000 tons of this production were exported to more than 40 countries. The objectives of this study were to isolate and to identify the fungi present in this cereal and to assess the occurrence of mycotoxins in freshly harvested popcorn in Buenos Aires province, Argentina, in 1999. All popcorn samples showed fungal contamination. A total of 4,211 isolates were recovered from popcorn kernel samples. The prevalent species isolated wasFusarium verticillioides followed byPenicillium funiculosum, F. graminearum andAlternaria alternata. No aflatoxins, zearalenone, deoxynivalenol or ochratoxin A were detected in the 42 popcorn simples. All samples but one were contaminated with fumonisins (FB) in a range in ug/kg of (not detected-529) for FB1; (not detected-216) for FB2 and (not detected-103) for FB3. Fumonisin contamination levels in Argentinean popcorn were lower than observed in flint corn. No significant differences in fungal and fumonisins contamination levels were observed in the different tested hybrids.
ABSTRACT
The region flanking the 5'-end of the rat gene encoding the cytoplasmic precursor of carbamyl-phosphate synthetase I, a mitochondrial matrix enzyme, has been cloned and partially characterized. S1 nuclease and primer extension analyses position the starts of transcription 138-140 nucleotides upstream of the translation initiation codon. Exon 1 contains this untranslated sequence and extends downstream to include the coding region for the pre-enzyme signal peptide (38 amino acids) plus 4 amino acids from the amino terminus of the mature protein. The 5'-flanking sequence contains typical promoter elements, including putative TATA and CAAT motifs at -21 and -82 nucleotides, respectively. In addition, several copies of consensus sequences corresponding to the H4TF-1 recognition element, GATTTC, together with the enhancer-like octamer, ATTTGCAT, are also present. Carbamyl-phosphate synthetase I is a cell-type specific enzyme, being expressed only in hepatocytes and epithelial cells of the intestinal mucosa. It is also synthesized at relatively high levels in the hepatoma cell line, Hep G2. Employing pCPS2.1, a minigene containing the promoter and part of exon 1, we show that nuclear extracts from Hep G2 support accurate carbamyl-phosphate synthetase I gene transcription in vitro. No such activity was observed, however, in extracts from HeLa, a cell line which does not express carbamyl-phosphate synthetase I.
