title: Complex regulation of the aflatoxin biosynthesis gene cluster of Aspergillus flavus in relation to various combinations of water activity and temperature.
abstract: A microarray analysis was performed to study the effect of varying combinations of water activity and temperature on the activation of aflatoxin biosynthesis genes in Aspergillusflavus grown on YES medium. Generally A. flavus showed expression of the aflatoxin biosynthetic genes at all parameter combinations tested. Certain combinations of a(w) and temperature, especially combinations which imposed stress on the fungus resulted in a significant reduction of the growth rate. At these conditions induction of the whole aflatoxin biosynthesis gene cluster occurred, however the produced aflatoxin B(1) was low. At all other combinations (25 degrees C/0.95 and 0.99; 30 degrees C/0.95 and 0.99; 35 degrees C/0.95 and 0.99) a reduced basal level of cluster gene expression occurred. At these combinations a high growth rate was obtained as well as high aflatoxin production. When single genes were compared, two groups with different expression profiles in relation to water activity/temperature combinations occurred. These two groups were co-ordinately localized within the aflatoxin gene cluster. The ratio of aflR/aflJ expression was correlated with increased aflatoxin biosynthesis.
authors.affiliation: Max Rubner Institute, Haid-und-Neu-Str. 9, 76131 Karlsruhe, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Schmidt-Heydt
authors.forename: Ahmed
authors.initials: A
authors.lastname: Abdel-Hadi
authors.forename: Naresh
authors.initials: N
authors.lastname: Magan
authors.forename: Rolf
authors.initials: R
authors.lastname: Geisen
mesh_terms: D000348:Aflatoxins / Q000096:biosynthesis / Q000235:genetics*; D001231:Aspergillus flavus / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D020869:Gene Expression Profiling; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D046228:Microarray Analysis; D005810:Multigene Family; D013312:Stress, Physiological; D013696:Temperature; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014867:Water / Q000502:physiology*
chemical_list: C113837:AFLR protein, Aspergillus; D000348:Aflatoxins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D014157:Transcription Factors; D014867:Water