title: Functional and phylogenetic analysis of the Aspergillus ochraceoroseus aflQ (ordA) gene ortholog.
abstract: Within the Aspergillus parasiticus and A. flavus aflatoxin (AF) biosynthetic gene cluster the aflQ (ordA) and aflP (omtA) genes encode respectively an oxidoreductase and methyltransferase. These genes are required for the final steps in the conversion of sterigmatocystin (ST) to aflatoxin B(1) (AFB(1)). Aspergillus nidulans harbors a gene cluster that produces ST, as the aflQ and aflP orthologs are either non-functional or absent in the genome. Aspergillus ochraceoroseus produces both AF and ST, and it harbors an AF/ST biosynthetic gene cluster that is organized much like the A. nidulans ST cluster. The A. ochraceoroseus cluster also does not contain aflQ or aflP orthologs. However the ability of A. ochraceoroseus to produce AF would indicate that functional aflQ and aflP orthologs are present within the genome. Utilizing degenerate primers based on conserved regions of the A. flavus aflQ gene and an A. nidulans gene demonstrating the highest level of homology to aflQ, a putative aflQ ortholog was PCR amplified from A. ochraceoroseus genomic DNA. The A. ochraceoroseus aflQ ortholog demonstrated 57% amino acid identity to A. flavus AflQ. Transformation of an O-methylsterigmatocystin (OMST)-accumulating A. parasiticus aflQ mutant with the putative A. ochraceoroseus aflQ gene restored AF production. Although the aflQ gene does not reside in the AF/ST cluster it appears to be regulated in a manner similar to other A. ochraceoroseus AF/ST cluster genes. Phylogenetic analysis of AflQ and AflQ-like proteins from a number of ST- and AF-producing Aspergilli indicates that A. ochraceoroseus might be ancestral to A. nidulans and A. flavus.
authors.affiliation: Southern Regional Research Center, Agricultural Research Service, U. S. Department of Agriculture, New Orleans, LA, USA. Jeff.Cary@ars.usda.gov
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Cary
authors.forename: Pamela Y
authors.initials: PY
authors.lastname: Harris-Coward
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Ehrlich
authors.forename: Geromy G
authors.initials: GG
authors.lastname: Moore
authors.forename: Qijian
authors.initials: Q
authors.lastname: Wei
authors.forename: Deepak
authors.initials: D
authors.lastname: Bhatnagar
mesh_terms: D000348:Aflatoxins / Q000235:genetics* / Q000378:metabolism; D001230:Aspergillus / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D017124:Conserved Sequence; D003470:Culture Media / Q000737:chemistry; D017931:DNA Primers / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism; D005810:Multigene Family; D016533:Mycological Typing Techniques; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity; D013241:Sterigmatocystin / Q000031:analogs & derivatives / Q000378:metabolism; D014170:Transformation, Genetic
chemical_list: D000348:Aflatoxins; D003470:Culture Media; D017931:DNA Primers; D004271:DNA, Fungal; D005656:Fungal Proteins; D013241:Sterigmatocystin; C039904:O-methylsterigmatocystin; D008780:Methyltransferases; C096006:omtA protein, Aspergillus