Participation in aflatoxin biosynthesis by a reductase enzyme encoded by vrdA gene outside the aflatoxin gene cluster.
Three reactions from hydroxyversicolorone to versicolorone, from versiconal hemiacetal acetate to versiconol acetate, and from versiconal to versiconol are involved in a metabolic grid in aflatoxin biosynthesis. This work demonstrated that the same reductase of Aspergillus parasiticus catalyzes the three reactions. The gene (named vrdA) encoding the reductase was cloned, and its sequence did not show homology to any regions in aflatoxin gene cluster. Its cDNA encoding a 38,566Da protein was separated by three introns in the genome. Deletion of the vrdA gene in A. parasiticus caused a significant decrease in enzyme activity, but did not affect aflatoxin productivity of the fungi. Although the vrdA gene was expressed in culture conditions conducive to aflatoxin production, it was expressed even in the aflR deletion mutant. These results suggest that the vrdA is not an aflatoxin biosynthesis gene, although it actually participates in aflatoxin biosynthesis in cells.
Shima
Yoko
Y
National Food Research Institute, National Agriculture and Food Research Organization (NARO), Tsukuba, Ibaraki, Japan.
Shiina
Marisa
M
Shinozawa
Takao
T
Ito
Yasuhiro
Y
Nakajima
Hiromitsu
H
Adachi
Yoshikazu
Y
Yabe
Kimiko
K
D000348:Aflatoxins / Q000096:biosynthesis*; D000595:Amino Acid Sequence; D000880:Anthraquinones / Q000378:metabolism; D001230:Aspergillus / Q000201:enzymology* / Q000235:genetics; D001483:Base Sequence; D003001:Cloning, Molecular; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D007438:Introns; D008969:Molecular Sequence Data; D008970:Molecular Weight; D005810:Multigene Family; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D000348:Aflatoxins; D000880:Anthraquinones; D004271:DNA, Fungal; D005656:Fungal Proteins; C072370:versiconol; C009653:versiconal; C027121:versiconal hemiacetal acetate; C072371:versiconol acetate; D010088:Oxidoreductases