首页> 美国卫生研究院文献>PLoS Clinical Trials >Identification of a Polyketide Synthase Required for Alternariol (AOH) and Alternariol-9-Methyl Ether (AME) Formation in Alternaria alternata
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Identification of a Polyketide Synthase Required for Alternariol (AOH) and Alternariol-9-Methyl Ether (AME) Formation in Alternaria alternata

机译:鉴定Alternaria alternata中Alternariol(AOH)和Alternariol-9-甲基醚(AME)形成所需的聚酮化合物合酶

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摘要

Alternaria alternata produces more than 60 secondary metabolites, among which alternariol (AOH) and alternariol-9-methyl ether (AME) are important mycotoxins. Whereas the toxicology of these two polyketide-based compounds has been studied, nothing is known about the genetics of their biosynthesis. One of the postulated core enzymes in the biosynthesis of AOH and AME is polyketide synthase (PKS). In a draft genome sequence of A. alternata we identified 10 putative PKS-encoding genes. The timing of the expression of two PKS genes, pksJ and pksH, correlated with the production of AOH and AME. The PksJ and PksH proteins are predicted to be 2222 and 2821 amino acids in length, respectively. They are both iterative type I reducing polyketide synthases. PksJ harbors a peroxisomal targeting sequence at the C-terminus, suggesting that the biosynthesis occurs at least partly in these organelles. In the vicinity of pksJ we found a transcriptional regulator, altR, involved in pksJ induction and a putative methyl transferase, possibly responsible for AME formation. Downregulation of pksJ and altR caused a large decrease of alternariol formation, suggesting that PksJ is the polyketide synthase required for the postulated Claisen condensations during the biosynthesis. No other enzymes appeared to be required. PksH downregulation affected pksJ expression and thus caused an indirect effect on AOH production.
机译:链格孢菌可产生60多种次级代谢产物,其中链霉菌素(AOH)和链霉菌素9-甲基醚(AME)是重要的霉菌毒素。尽管已经研究了这两种基于聚酮化合物的化合物的毒理学,但对其生物合成的遗传学却一无所知。 AOH和AME的生物合成中假定的核心酶之一是聚酮化合物合酶(PKS)。在交替拟南芥的基因组序列草案中,我们鉴定了10个假定的PKS编码基因。两个PKS基因pksJ和pksH的表达时间与AOH和AME的产生有关。预测PksJ和PksH蛋白的长度分别为2222和2821个氨基酸。它们都是迭代的I型还原聚酮化合物合酶。 PksJ在C末端带有一个过氧化物酶体靶向序列,这表明生物合成至少部分发生在这些细胞器中。在pksJ附近,我们发现了一个转录调控因子altR,参与pksJ的诱导和一个可能的AME形成负责的甲基转移酶。 pksJ和altR的下调导致交替烯醇的形成大大减少,这表明PksJ是生物合成过程中假定的Claisen缩合反应所需的聚酮化合物合酶。似乎不需要其他酶。 PksH下调影响pksJ表达,从而对AOH产生产生间接影响。

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