PDF(Pubmed)
Abstract：
Fungal polyketides (PKs) are one of the largest families of structurally diverse bioactive natural products biosynthesized by multidomain megasynthases, in which thioesterase (TE) domains act as nonequivalent decision gates determining both the shape and the yield of the polyketide intermediate. The endophytic fungus Preussia isomera XL-1326 was discovered to have an excellent capacity for secreting diverse bioactive PKs, i.e., the hot enantiomers (±)-preuisolactone A with antibacterial activity, the single-spiro minimoidione B with α-glucosidase inhibition activity, and the uncommon heptaketide setosol with antifungal activity, which drive us to illustrate how the unique PKs are biosynthesized. In this study, we first reported the genome sequence information of P. isomera. Based on genome mining, we discovered nine transcriptionally active genes encoding polyketide synthases (PKSs), Preu1-Preu9, of which those of Preu3, Preu4, and Preu6 were cloned and functionally characterized due to possessing complete sets of synthetic and release domains. Through heterologous expression in Saccharomyces cerevisiae, Preu3 and Preu6 could release high yields of orsellinic acid (OA) derivatives [3-methylorsellinic acid (3-MOA) and lecanoric acid, respectively]. Correspondingly, we found that Preu3 and Preu6 were clustered into OA derivative synthase groups by phylogenetic analysis. Next, with TE domain swapping, we constructed a novel \"non-native\" PKS, Preu6-TEPreu3, which shared a very low identity with OA synthase, OrsA, from Aspergillus nidulans but could produce a large amount of OA. In addition, with the use of Preu6-TEPreu3, we synthesized methyl 3-methylorsellinate (synthetic oak moss of great economic value) from 3-MOA as the substrate, and interestingly, 3-MOA exhibited remarkable antibacterial activities, while methyl 3-methylorsellinate displayed broad-spectrum antifungal activity. Taken together, we identified two novel PKSs to biosynthesize 3-MOA and lecanoric acid, respectively, with information on such kinds of PKSs rarely reported, and constructed one novel \"non-native\" PKS to largely biosynthesize OA. This work is our first step to explore the biosynthesis of the PKs in P. isomera, and it also provides a new platform for high-level environment-friendly production of OA derivatives and the development of new antimicrobial agents.
摘要：
真菌聚酮（PKs）是由多结构域megasynthase生物合成的结构多样的生物活性天然产物的最大家族之一，其中硫酯酶（TE）结构域充当非等效的决定门，决定了聚酮中间体的形状和产量。发现内生真菌PreussiaisomeraXL-1326具有分泌多种生物活性PKs的出色能力，即，具有抗菌活性的热对映体（±）-preuisolactoneA，具有α-葡萄糖苷酶抑制活性的单螺环小二烯酮B，和不常见的具有抗真菌活性的heptaketidesetosol，这促使我们说明独特的PKs是如何生物合成的。在这项研究中,我们首次报道了假单胞菌的基因组序列信息。基于基因组挖掘，我们发现了9个编码聚酮合成酶（PKSs）的转录活性基因，Preu1-Preu9，其中Preu3，Preu4和Preu6的那些被克隆和功能表征，由于具有完整的合成和释放域。通过在酿酒酵母中异源表达，Preu3和Preu6可以释放高产率的orsellinic酸（OA）衍生物[3-甲基orsellinic酸（3-MOA）和lecanoric酸，分别]。相应地,通过系统发育分析，我们发现Preu3和Preu6被聚集到OA衍生物合酶组中。接下来,使用TE域交换，我们构建了一个新的“非本地”PKS，Preu6-TEPreu3与OA合酶具有非常低的同一性，OrsA,来自构巢曲霉，但可以产生大量的OA。此外,使用Preu6-TEPreu3，我们以3-MOA为底物合成了3-甲基orsellinate（具有巨大经济价值的合成橡树苔藓），有趣的是，3-MOA具有显著的抗菌活性,而甲基3-甲基orsellinate显示广谱抗真菌活性。一起来看,我们确定了两种新的PKS生物合成3-MOA和莱卡诺酸，分别,关于这类PKS的信息很少报道，并构建了一种新型的“非天然”PKS，以大量生物合成OA。这项工作是我们探索P.isomera中PKs生物合成的第一步，同时也为高等级环保生产OA衍生物和新型抗菌剂的开发提供了新的平台。
