Substrate-induced lipase gene expression and aflatoxin production in Aspergillus parasiticus and Aspergillus flavus.
OBJECTIVE
To establish a relationship between lipase gene expression and aflatoxin production by cloning the lipA gene and studying its expression pattern in several aflatoxigenic and nontoxigenic isolates of Aspergillus flavus and A. parasiticus.


RESULTS
We have cloned a gene, lipA, that encodes a lipase involved in the breakdown of lipids from aflatoxin-producing A. flavus, A. parasiticus and two nonaflatoxigenic A. flavus isolates, wool-1 and wool-2. The lipA gene was transcribed under diverse media conditions, however, no mature mRNA was detected unless the growth medium was supplemented with 0.5% soya bean or peanut oil or the fungus was grown in lipid-rich medium such as coconut medium. The expression of the lipase gene (mature mRNA) under substrate-induced conditions correlated well with aflatoxin production in aflatoxigenic species A. flavus (SRRC 1007) and A. parasiticus (SRRC 143).


CONCLUSIONS
Substrate-induced lipase gene expression might be indirectly related to aflatoxin formation by providing the basic building block 'acetate' for aflatoxin synthesis. No direct relationship between lipid metabolism and aflatoxin production can be ascertained, however, lipase gene expression correlates well with aflatoxin formation.


CONCLUSIONS
Lipid substrate induces and promotes aflatoxin formation. It gives insight into genetic and biochemical aspects of aflatoxin formation.
Yu
J
J
USDA/ARS, Southern Regional Research Center, New Orleans, LA, USA. jiuyu@srrc.ars.usda.gov
Mohawed
S M
SM
Bhatnagar
D
D
Cleveland
T E
TE
D000348:Aflatoxins / Q000096:biosynthesis*; D000595:Amino Acid Sequence; D001230:Aspergillus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D001231:Aspergillus flavus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics; D002855:Chromatography, Thin Layer; D003001:Cloning, Molecular; D003470:Culture Media; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D005798:Genes, Bacterial; D008049:Lipase / Q000235:genetics / Q000378:metabolism*; D008055:Lipids / Q000494:pharmacology; D008969:Molecular Sequence Data; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000348:Aflatoxins; D001426:Bacterial Proteins; D003470:Culture Media; C079999:LipA protein, Bacteria; D008055:Lipids; D008049:Lipase