Functional Characterization of New Polyketide Synthase Genes Involved in Ochratoxin A Biosynthesis in Aspergillus Ochraceus fc-1

Wang, Liuqing; Wang, Yan; Wang, Qi; Liu, Fei; Selvaraj, Jonathan Nimal; Liu, Lingna; Xing, Fuguo; Zhao, Yang; Zhou, Lu; Liu, Yang

doi:10.3390/toxins7082723

Cited by 32 publications

(32 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The intriguing absence of AoOTApks1 transcripts in an OTA‐producing strain and the presence of the other three genes confirmed in the transcriptome assembled from the total RNA sequencing characterization suggest the possible involvement of a molecular pathway to synthetize OTA different from that previously suggested (Sartori et al ., ; Wang et al ., ). Furthermore, the lack of virus‐induced differential transcript accumulation suggests a possible AoV‐mediated direct/indirect post‐transcriptional or post‐translational modification of the genes analysed, including a potential interference with mycotoxin secretion, as is the case for the hydrophobin cryparin in the CHV1‐ C. parasitica system (Kazmierczak et al ., ).…”

Section: Resultsmentioning

confidence: 97%

“…Several genes have been reported in the literature as being putatively involved in OTA biosynthesis. Two of these genes belong to the polyketide synthase (pks) family (Wang et al ., ), one belongs to the cytochrome P450 family, and one is an oxygenase (Sartori et al ., ). Polyketide synthase 1 ( AoOTApks1 ) was not amplified in any of the samples analysed, while polyketide synthase 2 ( AoOTApks2 ) was equally expressed in the two isolates (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Nine replicates for each isolate and time point (48 h, 96 h and 144 h) were pooled (three by three) to obtain three biological replicates for each isolate. Total RNA was extracted, cDNA was synthetized and iTaq universal SYBR Green supermix (Bio‐Rad) with specific primers (Supporting Information Table 6) was used to amplify four genes of the OTA metabolic pathway: AoOTApks1 (Wang et al ., ), AoOTApks2 (Wang et al ., ), AoOTAP450 (Sartori et al ., ), and AoOTAOxi1 (Sartori et al ., ). β‐Tubulin ( AoβTub ) was used as a housekeeping gene.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Mycoviruses mediate mycotoxin regulation in Aspergillus ochraceus

Nerva

Chitarra

Siciliano

et al. 2018

Environmental Microbiology

View full text Add to dashboard Cite

Summary To date, no demonstration of a direct correlation between the presence of mycoviruses and the quantitative or qualitative modulation of mycotoxins has been shown. In our study, we transfected a virus‐free ochratoxin A (OTA)‐producing isolate of Aspergillus ochraceus with purified mycoviruses from a different A. ochraceus isolate and from Penicillium aurantiogriseum. Among the mycoviruses tested, only Aspergillus ochraceus virus (AoV), a partitivirus widespread in A. ochraceus, caused a specific interaction that led to an overproduction of OTA, which is regulated by the European Commission and is the second most important contaminant of food and feed commodities. Gene expression analysis failed to reveal a specific viral upregulation of the mRNA of genes considered to play a role in the OTA biosynthetic pathway. Furthermore, AoOTApks1, a polyketide synthase gene considered essential for OTA production, is surprisingly absent in the genome of our OTA‐producing isolate. The possible biological and evolutionary implications of the mycoviral regulation of mycotoxin production are discussed.

show abstract

Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Mycoviruses mediate mycotoxin regulation in Aspergillus ochraceus

Nerva

Chitarra

Siciliano

et al. 2018

Environmental Microbiology

View full text Add to dashboard Cite

show abstract

“…A proposed OTA biosynthetic pathway. To confirm the involvement of these putative biosynthetic genes in OTA biosynthesis, each of the cluster genes was individually inactivated by a homologous recombination strategy using polyethylene glycol (PEG)-mediated genetic transformation (14). The growth rates of the deletion mutants on peptone-dextrose agar (PDA) and yeast extract and sucrose (YES) medium were not significantly different (P Ͼ 0.01) (data not shown).…”

Section: Resultsmentioning

confidence: 99%

“…Gallo et al proposed that ochratoxin ␤ and L-phenylalanine were biotransformed to ochratoxin B (OTB) by a nonribosomal peptide synthetase (NRPS) and that the OTB was transformed to OTA through chlorination in Aspergillus carbonarius (13). Wang et al characterized two polyketide synthases (PKSs) involved in OTA biosynthesis in A. ochraceus (14). Farber and Geisen demonstrated the potential role of a putative halogenase through the analysis of differentially expressed OTA biosynthesis genes in Penicillium nordicum (15), and Ferrara et al identified a halogenase involved in OTA biosynthesis in A. carbonarius (16).…”

mentioning

confidence: 99%

A Consensus Ochratoxin A Biosynthetic Pathway: Insights from the Genome Sequence of Aspergillus ochraceus and a Comparative Genomic Analysis

Wang

et al. 2018

Appl Environ Microbiol

Self Cite

View full text Add to dashboard Cite

Ochratoxin A (OTA) is a toxic secondary metabolite produced by and species that widely contaminate food and feed. We sequenced and assembled the complete ∼37 Mb genome of fc-1, a well-known producer of OTA. Key genes of the OTA biosynthetic pathway were identified by comparative genomic analyses with five other sequenced OTA-producing fungi,, ,, , and OTA production was completely inhibited in the deletion mutants (- and ), and OTA biosynthesis was restored by feeding a post-block substrate to the corresponding mutant. The OTA biosynthetic pathway was unblocked with the addition of heterologously expressed halogenase in the mutant. OTA biosynthesis begins with PKS (), utilizing acetyl-CoA and malonyl-CoA to synthesize 7-methylmellein, which is oxidized to OTβ by cytochrome P450 monooxygenase (). OTβ and L-β-phenylalanine are combined by NRPS () to form an amide bond to synthesize OTB. Finally, OTB is chlorinated by halogenase () to OTA. The - genes were expressed at low levels in the mutant. A second regulator, otaR2, which is adjacent to the biosynthetic gene, could modulate only the expression of, and Thus, we have identified a consensus OTA biosynthetic pathway that can be used to prevent and control OTA synthesis, and to understand variation and production of the intermediate components in the biosynthetic pathway. Ochratoxin A (OTA) is a significant mycotoxin that contaminates cereal products, coffee, grapes, wine, cheese and meat. OTA is nephrotoxic, carcinogenic, teratogenic and immunotoxic. OTA contamination is a serious threat to food safety, endangers human health and can cause huge economic losses. At present, more than 20 species of the genera and are known to produce OTA. Here, we demonstrate that a consensus OTA biosynthetic pathway exists in all OTA-producing fungi and that is encoded by a gene cluster containing four highly conserved biosynthetic genes and a bZIP transcription factor.

show abstract