Effect of Dichlorvos on Aflatoxin and Versicolorin a Production in Aspergillus parasiticus

1976 ◽  
Vol 137 (4) ◽  
pp. 318-324 ◽  
Author(s):  
J. W. Bennett ◽  
L. S. Lee ◽  
A. F. Cucullu
Keyword(s):  
Aspergillus Parasiticus ◽  
Versicolorin A

scholarly journals The Aspergillus parasiticus estA-Encoded Esterase Converts Versiconal Hemiacetal Acetate to Versiconal and Versiconol Acetate to Versiconol in Aflatoxin Biosynthesis

2004 ◽  
Vol 70 (6) ◽  
pp. 3593-3599 ◽  
Author(s):  
Perng-Kuang Chang ◽  
Kimiko Yabe ◽  
Jiujiang Yu
Keyword(s):  
Aspergillus Parasiticus ◽  
Enzyme Assays ◽  
Aflatoxin Biosynthesis ◽  
Cell Extracts ◽  
Esterase Gene ◽  
Versicolorin A ◽  
Versiconal Hemiacetal Acetate ◽  
Esterase Activities ◽  
Esterase Inhibitor

ABSTRACT In aflatoxin biosynthesis, the pathway for the conversion of 1-hydroxyversicolorone to versiconal hemiacetal acetate (VHA) to versiconal (VHOH) is part of a metabolic grid. In the grid, the steps from VHA to VHOH and from versiconol acetate (VOAc) to versiconol (VOH) may be catalyzed by the same esterase. Several esterase activities are associated with the conversion of VHA to VHOH, but only one esterase gene (estA) is present in the complete aflatoxin gene cluster of Aspergillus parasiticus. We deleted the estA gene from A. parasiticus SRRC 2043, an O-methylsterigmatocystin (OMST)-accumulating strain. The estA-deleted mutants were pigmented and accumulated mainly VHA and versicolorin A (VA). A small amount of VOAc and other downstream aflatoxin intermediates, including VHOH, versicolorin B, and OMST, also were accumulated. In contrast, a VA-accumulating mutant, NIAH-9, accumulated VA exclusively and neither VHA nor VOAc were produced. Addition of the esterase inhibitor dichlorvos (dimethyl 2,2-dichlorovinylphosphate) to the transformation recipient strain RHN1, an estA-deleted mutant, or NIAH-9 resulted in the accumulation of only VHA and VOAc. In in vitro enzyme assays, the levels of the esterase activities catalyzing the conversion of VHA to VHOH in the cell extracts of two estA-deleted mutants were decreased to approximately 10% of that seen with RHN1. Similar decreases in the esterase activities catalyzing the conversion of VOAc to VOH were also obtained. Thus, the estA-encoded esterase catalyzes the conversion of both VHA to VHOH and VOAc to VOH during aflatoxin biosynthesis.

Biosynthesis of aflatoxin B1. Conversion of versicolorin A to aflatoxin B1 by Aspergillus parasiticus

1976 ◽  
Vol 24 (6) ◽  
pp. 1167-1170 ◽  
Author(s):  
Louise S. Lee ◽  
Joan W. Bennett ◽  
Alva F. Cucullu ◽  
Robert L. Ory
Keyword(s):  
Aflatoxin B1 ◽  
Aspergillus Parasiticus ◽  
Versicolorin A

scholarly journals Nonfunctionality of Aspergillus sojae aflR in a Strain of Aspergillus parasiticus with a Disrupted aflR Gene

2002 ◽  
Vol 68 (8) ◽  
pp. 3737-3743 ◽  
Author(s):  
Tadashi Takahashi ◽  
Perng-Kuang Chang ◽  
Kenichiro Matsushima ◽  
Jiujiang Yu ◽  
Keietsu Abe ◽  
...  
Keyword(s):  
Aspergillus Oryzae ◽  
Aspergillus Parasiticus ◽  
Transcription Activation ◽  
Aflatoxin Production ◽  
Activation Domain ◽  
Aspergillus Sojae ◽  
Coding Regions ◽  
Transcription Activation Domain ◽  
Chimeric Construct ◽  
Versicolorin A

ABSTRACT Aspergillus sojae belongs to the Aspergillus section Flavi but does not produce aflatoxins. The functionality of the A. sojae aflR gene (aflRs) was examined by transforming it into an ΔaflR strain of A. parasiticus, derived from a nitrate-nonutilizing, versicolorin A (VERA)-accumulating strain. The A. parasiticus aflR gene (aflRp) transformants produced VERA, but the aflRs transformants did not. Even when aflRs was placed under the control of the amylase gene (amyB) promoter of Aspergillus oryzae, the amy(p)::aflRs transformants did not produce VERA. A chimeric construct containing the aflRs promoter plus the aflRs N- and aflRp C-terminal coding regions could restore VERA production, but a construct containing the aflRp promoter plus the aflRp N- and aflRs C-terminal coding regions could not. These results show that the A. sojae aflR promoter is functional in A. parasiticus and that the HAHA motif does not affect the function of the resulting hybrid AflR. We conclude that the lack of aflatoxin production by A. sojae can be attributed, at least partially, to the premature termination defect in aflRs, which deletes the C-terminal transcription activation domain that is critical for the expression of aflatoxin biosynthetic genes.

Aspergillus parasiticus Accumulates Averufin and Versicolorin A in the Presence of Bicarbonate

1989 ◽  
Vol 52 (7) ◽  
pp. 493-495 ◽  
Author(s):  
ANWAAR EL-NABARAWY ◽  
THOMAS HARTMAN ◽  
JOSEPH D. ROSEN ◽  
THOMAS J. MONTVILLE
Keyword(s):  
Sodium Bicarbonate ◽  
Thin Layer ◽  
Aspergillus Parasiticus ◽  
Aflatoxin Production ◽  
Ionization Mass ◽  
Desorption Chemical Ionization ◽  
Norsolorinic Acid ◽  
Solvent Systems ◽  
Versicolorin A ◽  
Abnormal Pigmentation

Sodium bicarbonate has previously been shown to inhibit aflatoxin production by Aspergillus parasiticus. The abnormal pigmentation of colonies grown in the presence of bicarbonate suggested that intermediates of the aflatoxin biosynthetic pathway were accumulating. Aspergillus parasiticus NRRL 2999 cultures grown in the presence of sodium bicarbonate were extracted with acetone and chloroform. Thin layer chromatograms of these extracts were compared to the thin layer chromatograms of extracts from mutant strains which accumulate norsolorinic acid, averufin, and versicolorin A. Development by four separate solvent systems suggested that averufin and versicolorin A accumulated in the bicarbonate-grown wild type cultures. The identity of these intermediates was confirmed by desorption chemical ionization mass spectrometry which showed M+1 peaks of 369 and 339 where M is the molecular weight of averufin and versicolorin, respectively.

scholarly journals An Aflatoxin Biosynthesis Cluster Gene Encodes a Novel Oxidase Required for Conversion of Versicolorin A to Sterigmatocystin

2005 ◽  
Vol 71 (12) ◽  
pp. 8963-8965 ◽  
Author(s):  
Kenneth C. Ehrlich ◽  
Beverly Montalbano ◽  
Stephen M. Boué ◽  
Deepak Bhatnagar
Keyword(s):  
Aspergillus Parasiticus ◽  
Aflatoxin Biosynthesis ◽  
Versicolorin A ◽  
Cluster Gene

ABSTRACT Disruption of the aflatoxin biosynthesis cluster gene aflY (hypA) gave Aspergillus parasiticus transformants that accumulated versicolorin A. This gene is predicted to encode the Baeyer-Villiger oxidase necessary for formation of the xanthone ring of the aflatoxin precursor demethylsterigmatocystin.

scholarly journals Enzymatic Conversion of Averufin to Hydroxyversicolorone and Elucidation of a Novel Metabolic Grid Involved in Aflatoxin Biosynthesis

2003 ◽  
Vol 69 (1) ◽  
pp. 66-73 ◽  
Author(s):  
Kimiko Yabe ◽  
Naomi Chihaya ◽  
Shioka Hamamatsu ◽  
Emi Sakuno ◽  
Takashi Hamasaki ◽  
...  
Keyword(s):  
Aspergillus Parasiticus ◽  
Cell Extract ◽  
Aflatoxin Biosynthesis ◽  
Cytosol Fraction ◽  
Feeding Experiments ◽  
A Cell ◽  
Molecular Masses ◽  
Microsome Fraction ◽  
Versicolorin A ◽  
Versiconal Hemiacetal Acetate

ABSTRACT The pathway from averufin (AVR) to versiconal hemiacetal acetate (VHA) in aflatoxin biosynthesis was investigated by using cell-free enzyme systems prepared from Aspergillus parasiticus. When (1′S,5′S)-AVR was incubated with a cell extract of this fungus in the presence of NADPH, versicolorin A and versicolorin B (VB), as well as other aflatoxin pathway intermediates, were formed. When the same substrate was incubated with the microsome fraction and NADPH, hydroxyversicolorone (HVN) and VHA were formed. However, (1′R,5′R)-AVR did not serve as the substrate. In cell-free experiments performed with the cytosol fraction and NADPH, VHA, versicolorone (VONE), and versiconol acetate (VOAc) were transiently produced from HVN in the early phase, and then VB and versiconol (VOH) accumulated later. Addition of dichlorvos (dimethyl 2,2-dichlorovinylphosphate) to the same reaction mixture caused transient formation of VHA and VONE, followed by accumulation of VOAc, but neither VB nor VOH was formed. When VONE was incubated with the cytosol fraction in the presence of NADPH, VOAc and VOH were newly formed, whereas the conversion of VOAc to VOH was inhibited by dichlorvos. The purified VHA reductase, which was previously reported to catalyze the reaction from VHA to VOAc, also catalyzed conversion of HVN to VONE. Separate feeding experiments performed with A. parasiticus NIAH-26 along with HVN, VONE, and versicolorol (VOROL) demonstrated that each of these substances could serve as a precursor of aflatoxins. Remarkably, we found that VONE and VOROL had ring-opened structures. Their molecular masses were 386 and 388 Da, respectively, which were 18 Da greater than the molecular masses previously reported. These data demonstrated that two kinds of reactions are involved in the pathway from AVR to VHA in aflatoxin biosynthesis: (i) a reaction from (1′S,5′S)-AVR to HVN, catalyzed by the microsomal enzyme, and (ii) a new metabolic grid, catalyzed by a new cytosol monooxygenase enzyme and the previously reported VHA reductase enzyme, composed of HVN, VONE, VOAc, and VHA. A novel hydrogenation-dehydrogenation reaction between VONE and VOROL was also discovered.

Synthesis of versicolorin A by a mutant strain of Aspergillus parasiticus deficient in aflatoxin production

1975 ◽  
Vol 23 (6) ◽  
pp. 1132-1134 ◽  
Author(s):  
Louise S. Lee ◽  
Joan W. Bennett ◽  
Alva F. Cucullu ◽  
James B. Stanley
Keyword(s):  
Mutant Strain ◽  
Aspergillus Parasiticus ◽  
Aflatoxin Production ◽  
Versicolorin A
Sign in / Sign up

Export Citation Format

Share Document