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Secondary metabolism in fungi is frequently associated with asexual and sexual development. Aspergillus parasiticus produces aflatoxins known to contaminate a variety of agricultural commodities. This strictly mitotic fungus, besides producing
conidia asexually, produces sclerotia, structures resistant to harsh conditions and for propagation. Sclerotia are considered
to be derived from the sexual structure, cleistothecia, and may represent a vestige of ascospore production. Introduction
of the aflatoxin pathway-specific regulatory gene, aflR, and aflJ, which encoded a putative co-activator, into an O-methylsterigmatocystin (OMST)-accumulating strain,A. parasiticus SRRC 2043, resulted in elevated levels of accumulation of major aflatoxin precursors, including norsolorinic acid (NOR),
averantin (AVN), versicolorin A (VERA) and OMST. The total amount of these aflatoxin precursors, NOR, VERA, AVN and OMST,
produced by the aflR plus aflJ transformants was two to three-fold that produced by the aflR transformants. This increase indicated a synergisticeffect of aflR and aflJ on the synthesis of aflatoxin precursors. Increased production of the aflatoxin precursors was associated with progressive
decrease in sclerotial size, alteration in sclerotial shape and weakening in the sclerotial structure of the transformants.
The results showed that sclerotial development and aflatoxin biosynthesis are closely related. We proposed that competition
for a common substrate, such as acetate, by the aflatoxin biosynthetic pathway could adversely affect sclerotial development
in A. parasiticus.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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AFLR is a Zn2Cys6-type sequence-specific DNA-binding protein that is thought to be necessary for expression of most of the genes in the aflatoxin pathway gene cluster in Aspergillus parasiticus and A. flavus, and the sterigmatocystin gene cluster in A. nidulans. However, it was not known whether AFLR bound to the promoter regions of each of the genes in the cluster. Recently, A. nidulans AFLR was shown to bind to the motif 5′-TCGN5CGA-3′. In the present study, we examined the binding of AFLR to promoter regions of 11 genes in the A. parasiticus cluster. Based on electrophoretic mobility shift assays, the genes nor1, pksA, adhA, norA, ver1, omtA, ordA, and, vbs, had at least one 5′-TCGN5CGA-3′ binding site within 200 bp of the translation start site, and pksA and ver1 had an additional binding site further upstream. Although the promoter region of avnA lacked this motif, AFLR bound weakly to the sequence 5′-TCGCAGCCCGG-3′ at −110 bp. One region in the promoter of the divergently transcribed genes aflR/aflJ bound weakly to AFLR even though it contained a site with at most only 7 bp of the 5′-TCGN5CGA-3′ motif. This partial site may be recognized by a monomeric form of AFLR. Based on a comparison of 16 possible sites, the preferred binding sequence was 5′-TCGSWNNSCGR-3′. 相似文献
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Generation of aflR disruption mutants of Aspergillus parasiticus 总被引:1,自引:0,他引:1
Cary JW Ehrlich KC Wright M Chang PK Bhatnagar D 《Applied microbiology and biotechnology》2000,53(6):680-684
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Green Fluorescent Protein as a Reporter To Monitor Gene Expression and Food Colonization by Aspergillus flavus 总被引:1,自引:0,他引:1 下载免费PDF全文
Wanglei Du Zhengyu Huang Joseph E. Flaherty Kevin Wells Gary A. Payne 《Applied microbiology》1999,65(2):834-836
Transformants of Aspergillus flavus containing the Aequorea victoria gfp gene fused to a viral promoter or the promoter region and 483 bp of the coding region of A. flavus aflR expressed green fluorescence detectable without a microscope or filters. Expression of green fluorescent protein fluorescence was correlated with resistance to aflatoxin accumulation in five corn genotypes inoculated with these transformants. 相似文献
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Miguel A. Moreno Cristina Pascual Alicia Gibello Sergi Ferrer Cees J. Bos Alfons J.M. Debets Guillermo Suárez 《FEMS microbiology letters》1994,124(1):35-41
Abstract A genetic transformation system for the aflatoxin-producing fungus Aspergillus parasiticus using two autonomously replicating plasmids from A. nidulans (ARp1 and pDHG25) is reported. Transformation frequencies using the plasmid pDHG25 were from 5 × 102 to 2.5 × 104 transformants per 106 viable protoplasts and μg DNA. The stability of the plasmids in the transformants was also studied. This transformation system offers a new opportunity to clone genes related to aflatoxin production using appropriate aflatoxin-defective mutants. 相似文献
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Binding of the C6-zinc cluster protein, AFLR, to the promoters of aflatoxin pathway biosynthesis genes in Aspergillus parasiticus 总被引:1,自引:0,他引:1
AFLR is a Zn2Cys6-type sequence-specific DNA-binding protein that is thought to be necessary for expression of most of the genes in the aflatoxin pathway gene cluster in Aspergillus parasiticus and A. flavus, and the sterigmatocystin gene cluster in A. nidulans. However, it was not known whether AFLR bound to the promoter regions of each of the genes in the cluster. Recently, A. nidulans AFLR was shown to bind to the motif 5′-TCGN5CGA-3′. In the present study, we examined the binding of AFLR to promoter regions of 11 genes in the A. parasiticus cluster. Based on electrophoretic mobility shift assays, the genes nor1, pksA, adhA, norA, ver1, omtA, ordA, and, vbs, had at least one 5′-TCGN5CGA-3′ binding site within 200 bp of the translation start site, and pksA and ver1 had an additional binding site further upstream. Although the promoter region of avnA lacked this motif, AFLR bound weakly to the sequence 5′-TCGCAGCCCGG-3′ at −110 bp. One region in the promoter of the divergently transcribed genes aflR/aflJ bound weakly to AFLR even though it contained a site with at most only 7 bp of the 5′-TCGN5CGA-3′ motif. This partial site may be recognized by a monomeric form of AFLR. Based on a comparison of 16 possible sites, the preferred binding sequence was 5′-TCGSWNNSCGR-3′. 相似文献