曲霉毒素A（OTA）是由曲霉和青霉菌产生的有毒次级代谢产物，广泛污染食品和饲料。我们对著名的OTA生产者Aspergilluschraceusfc-1的完整~37-Mb基因组进行了测序和组装。通过与其他五种测序的OTA产生真菌进行比较基因组分析，鉴定了OTA生物合成途径的关键基因：A.carbonarius，A.尼日尔,A.Steynii,A.westerdijkiae，在缺失突变体中，北青霉OTA的产生被完全抑制(ΔotaA，ΔotaB,ΔotaC,ΔotaD,和ΔotaR1)，OTA生物合成通过向相应的突变体喂食后阻断底物来恢复。通过添加异源表达的卤化酶，在ΔotaD突变体中解除了OTA生物合成途径的阻断。OTA生物合成始于聚酮合成酶（PKS），OtaA,利用乙酰辅酶A（乙酰辅酶A）和丙二酰辅酶A合成7-甲基mellein，其被细胞色素P450单加氧酶(OtaC)氧化为OTβ。OTβ和1-β-苯丙氨酸通过非核糖体肽合成酶（NRPS）结合，OtaB,形成酰胺键合成OTB。最后,OTB被卤化酶(OtaD)氯化为OTA。在ΔotaR1突变体中，otaABCD基因的表达水平较低。第二个调节器，与生物合成基因相邻的otaR2，只能调节otaA的表达，otaB,因此，我们已经确定了一个可用于预防和控制OTA合成的共有OTA生物合成途径,这将有助于我们了解生物合成途径中中间组分的变异和产生.重要OchratoxinA（OTA）是一种重要的霉菌毒素，会污染谷物产品，咖啡,葡萄,葡萄酒,奶酪,和肉。OTA是肾毒性的，致癌，致畸,和免疫毒性。OTA污染严重威胁食品安全,危害人类健康,会造成巨大的经济损失。目前,已知>20种曲霉属和青霉属产生OTA。在这里，我们证明了共有OTA生物合成途径存在于所有产生OTA的真菌中，并且由包含四个高度保守的生物合成基因和bZIP转录因子的基因簇编码。
Ochratoxin A (OTA) is a toxic secondary metabolite produced by Aspergillus and
Penicillium species that widely contaminates food and feed. We sequenced and assembled the complete ∼37-Mb genome of Aspergillusochraceus 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: A. carbonarius, A. niger, A. steynii, A. westerdijkiae, and
Penicillium nordicum OTA production was completely inhibited in the deletion mutants (ΔotaA, ΔotaB, ΔotaC, ΔotaD, and ΔotaR1), and OTA biosynthesis was restored by feeding a postblock substrate to the corresponding mutant. The OTA biosynthetic pathway was unblocked in the ΔotaD mutant by the addition of heterologously expressed halogenase. OTA biosynthesis begins with a polyketide synthase (PKS), OtaA, utilizing acetyl coenzyme A (acetyl-CoA) and malonyl-CoA to synthesize 7-methylmellein, which is oxidized to OTβ by cytochrome P450 monooxygenase (OtaC). OTβ and l-β-phenylalanine are combined by a nonribosomal peptide synthetase (NRPS), OtaB, to form an amide bond to synthesize OTB. Finally, OTB is chlorinated by a halogenase (OtaD) to OTA. The otaABCD genes were expressed at low levels in the ΔotaR1 mutant. A second regulator, otaR2, which is adjacent to the biosynthetic gene, could modulate only the expression of otaA, otaB, and otaD Thus, we have identified a
consensus OTA biosynthetic pathway that can be used to prevent and control OTA synthesis and will help us understand the variation and production of the intermediate components in the biosynthetic pathway.IMPORTANCE 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, >20 species of the genera Aspergillus and
Penicillium are known to produce OTA. Here we demonstrate that a
consensus OTA biosynthetic pathway exists in all OTA-producing fungi and is encoded by a gene cluster containing four highly conserved biosynthetic genes and a bZIP transcription factor.
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