title: Expression of genes of the aflatoxin biosynthetic pathway in Aspergillus flavus isolates from keratitis.
abstract: OBJECTIVE
  To document transcriptional activation (expression) of key aflatoxin biosynthetic pathway genes in corneal isolates of Aspergillus flavus.
  
  
  METHODS
  The expression of certain regulatory (aflatoxin regulatory [aflR] and aflatoxin J [aflJ]) and structural (polyketide synthase acetate [pksA] and norsolonic acid-1 [nor-1]) genes in four corneal A. flavus isolates was evaluated by reverse transcription PCR. The aflatoxin-producing potential of each strain was determined by thin-layer chromatography and quantified by spectrophotometry. Four environmental isolates were used for comparison. The mean expression levels of these genes were compared in the corneal and environmental A. flavus isolates. In addition, the mean expression levels were also correlated with the aflatoxin production levels.
  
  
  RESULTS
  All isolates expressed aflJ, nor-1, and pksA, while all but one expressed aflR. Overall, significantly higher mean expression levels occurred in aflatoxigenic than in non-aflatoxigenic corneal isolates. A significant positive correlation was noted between the mean expression level of aflR and the quantum of aflatoxin production by the corneal isolates. Essentially similar patterns of expression of these genes were noted in four environmental A. flavus isolates used for comparison.
  
  
  CONCLUSIONS
  For the first time, isolates of A. flavus from human keratitis patients have been shown to express regulatory and structural aflatoxin biosynthetic pathway genes. Further studies are needed to clarify the precise influence of the corneal microenvironment on expression of these genes and aflatoxin production by A. flavus infecting the cornea.
authors: Department of Animal Science, School of Life Sciences, Bharathidasan University, Tamil Nadu, India.
authors: George
authors: G
authors: Leema
authors: Duen-Suey
authors: DS
authors: Chou
authors: Christadoss A Nelson
authors: CA
authors: Jesudasan
authors: Pitchairaj
authors: P
authors: Geraldine
authors: Philip A
authors: PA
authors: Thomas
mesh_terms: D000348:Aflatoxins / Q000096:biosynthesis* / Q000235:genetics; D001231:Aspergillus flavus / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D053898:Biosynthetic Pathways / Q000235:genetics*; D002855:Chromatography, Thin Layer; D003315:Cornea / Q000382:microbiology* / Q000473:pathology; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D005656:Fungal Proteins / Q000096:biosynthesis* / Q000235:genetics; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D006801:Humans; D007634:Keratitis / Q000382:microbiology* / Q000473:pathology; D048630:Polyketide Synthases / Q000096:biosynthesis* / Q000235:genetics; D016133:Polymerase Chain Reaction; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D015533:Transcriptional Activation
chemical_list: C113837:AFLR protein, Aspergillus; D000348:Aflatoxins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D014157:Transcription Factors; D048630:Polyketide Synthases