Skip to main content
Article thumbnail
Location of Repository

Temporal monitoring of the nor-1 (aflD) gene of Aspergillus flavus in relation to aflatoxin B-1 production during storage of peanuts under different water activity levels

By Ahmed Abdel-Hadi, D Carter and Naresh Magan


Aims: A relative quantification system (RQ-PCR) was used to monitor the correlations between the activity of the nor-1 (=aflD) gene of Aspergillus flavus using real-time PCR in relation to phenotypic aflatoxin B-1 (AFB(1)) production and populations of A. flavus in stored peanuts at three water activity levels (a(w), 0.95, 0.90 and 0.85) for 6 weeks. Methods and Results: Real-time PCR was used to amplify the nor-1 gene (target gene), and benA56 (beta-tubulin gene) used as a control gene. Expression of three structural genes, nor-1 (=aflD), ver-1 (=aflM), and omtA (=aflP), and the regulatory gene aflR of the aflatoxin biosynthetic pathway were also assayed. There were significant differences between nor-1 gene expression at the three a(w) levels; higher expression at 0.90 a(w) in weeks 1-3, when compared to 0.95. In contrast, in the driest treatment (0.85 a(w)) none or very low nor-1 expression occurred. The populations of A. flavus colony-forming units (CFUs g(-1)) increased over time with the highest at 0.95 a(w). Highest AFB(1) production was at 0.90 and 0.95 a(w) from weeks 3-6. A(w) had a significant effect on aflR transcription at 0.95 a(w) over the 6-week period, while at 0.90 a(w), only in the last 2 weeks. Conclusions: Correlations between different factors showed that log AFB(1) x log CFUs, log AFB(1) x a(w), and log CFUs x a(w) were statistically significant, while log CFUs x RQ-PCR and RQ-PCR x a(w) were not. The AflR gene may not have an important role in the regulation of nor-1 expression in food matrices (e. g. peanuts). Significance and Impact of the study: Determination of correlations between nor-1 expression and aflatoxin production by A. flavus in raw peanuts under different a(w) levels could be helpful to predict potential risk of aflatoxin production during storage of this hygroscopic food product and minimize contamination with the AFB(1)

Topics: aflatoxin genes aflatoxins Aspergillus flavus CFUs peanuts real-time PCR polymerase-chain-reaction real-time pcr section flavi united-states rt-pcr biosynthesis growth quantification parasiticus mycotoxins
Publisher: Blackwell Publishing Ltd
Year: 2010
DOI identifier: 10.1111/j.1365-2672.2010.04820.x
OAI identifier:
Provided by: Cranfield CERES

Suggested articles


  1. (1998). (2010)Detection and quantification of Aspergillus section Flavi spp. in stored peanuts by real time PCR of nor-1 gene, and effects of storage conditions on aflatoxin production. doi
  2. (2007). A microarray for monitoring the production of mycotoxins in food. doi
  3. (2007). A multiplex RT-PCR approach to detect aflatoxigenic strains of Aspergillus flavus. doi
  4. (2001). A new mathematical model for relative quantification in real-time RTPCR. doi
  5. (2009). A polyphasic approach to the identification of aflatoxigenic and non-aflatoxigenic strains of Aspergillus section Flavi isolated from Portuguese almonds. doi
  6. (2005). Aflatoxin conducive and non-conducive growth conditions reveal new gene associations with aflatoxin production. doi
  7. (1997). Aflatoxin-producing potential of communities of Aspergillus Flavi from cotton producing areas in the United States. doi
  8. (1998). Amaranth grain as substrate for aflatoxin and zearalenone production at different water activity levels. doi
  9. (2000). An improved method for the isolation of total RNA from Malva pusilla tissues infected with Colletotrichum gloeosporioides. doi
  10. (2004). Association of Official Analytical Chemist, Official methods of analysis. Natural toxins, 17 th edn.,
  11. (2007). Biodiversity of Aspergillus section Flavi in the United States: a review Food Add doi
  12. (1992). Cloning of a gene associated with aflatoxin B1 biosynthesis in Aspergillus parasiticus. doi
  13. (2004). Clustered pathway genes in aflatoxin biosynthesis. doi
  14. (2005). Comparison of the effect of environmental factors on deoxynivalenol production by F. culmorum doi
  15. (2009). Complex regulation of the aflatoxin biosynthesis gene cluster of Aspergillus flavus in relation to various combinations of water activity and temperature. doi
  16. (1996). Detection of aflatoxigenic molds in grains by PCR.
  17. (2005). Detection of transcripts of the aflatoxin genes aflD, aflO, and aflP by reverse transcriptionpolymerase chain reaction allows differentiation of aflatoxin-producing and nonproducing isolates of Aspergillus flavus and Aspergillus parasiticus. doi
  18. (2009). Ecology of Aspergillus flavus, regulation of aflatoxin production, and management strategies to reduce aflatoxin contamination of corn. doi
  19. (1980). Effect of temperature and moisture content on Egyptian peanut seed-borne fungi. doi
  20. (2000). Genetic and biological control of aflatoxigenic fungi. doi
  21. (2009). Genetic regulation of aflatoxin biosynthesis: from gene to genome. doi
  22. (2004). Isolation, enumeration and PCR characterization of aflatoxigenic fungi from food and feed samples in India. doi
  23. (2004). Lack of interaction between AFLR and AFLJ contributes to nonflatoxigenicity of Aspergillus sojae. doi
  24. (2007). Molecular and chemical monitoring of growth and ochratoxin A biosynthesis of P. verrucosum in wheat stored at different moisture conditions. doi
  25. (1994). Molecular characterization of aflR, a regulatory locus for aflatoxin biosynthesis.
  26. (1996). Multiplex polymerase chain reaction for the detection of potential aflatoxin and sterigmatocystin producing fungi. doi
  27. (2010). Mycotoxigenic fungi in peanuts from different geographic regions of Egypt. doi
  28. (1992). Mycotoxin contamination of spices-an update. doi
  29. (1987). Mycroflora and mycotoxins of peanut (Archis hypogaea L.) seeds in Egypt. 1- sugar fungi and natural occurrence of mycotoxins. doi
  30. (1988). Natural occurrence of mycotoxin in food and feeds-an update review.
  31. (2007). Post-harvest control strategies: minimising mycotoxins in the food chain. doi
  32. (2003). Post-harvest fungal ecology: impact of fungal growth and mycotoxin accumulation in stored grain. doi
  33. (2003). Quantification of the number of nor-1, a gene of the aflaxtoxin biosynthetic pathway by real-time PCR, and its correlation to the CFUs of Aspergillus flavus in foods. doi
  34. (2008). Relationship between solute and matric potential stress, temperature, growth, and FUM1 gene expression in two Fusarium verticillioides strains from Spain. doi
  35. (2008). Stress induction of mycotoxin biosynthesis genes by abiotic factors. doi
  36. (1994). Structural and functional analysis of the nor-1 gene involved in the biosynthesis of aflatoxins by Aspergillus parasiticus.

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.