Department of Genetics, Institute of Biology and Ecology, Faculty of Science, Pavol Jozef Šafárik University in Košice, Mánesova 23, Košice, 04154, Slovakia.
BMC Genomics. 2024 Jun 3;25(1):555. doi: 10.1186/s12864-024-10475-z.
The search for new bioactive natural compounds with anticancer activity is still of great importance. Even though their potential for diagnostics and treatment of cancer has already been proved, the availability is still limited. Hypericin, a naphthodianthrone isolated essentially from plant source Hypericum perforatum L. along with other related anthraquinones and bisanthraquinones belongs to this group of compounds. Although it has been proven that hypericin is synthesized by the polyketide pathway in plants, none of the candidate genes coding for key enzymes has been experimentally validated yet. Despite the rare occurrence of anthraquinones in plants, their presence in microorganisms, including endophytic fungi, is quite common. Unlike plants, several biosynthetic genes grouped into clusters (BGCs) in fungal endophytes have already been characterized.
The aim of this work was to predict, identify and characterize the anthraquinone BGCs in de novo assembled and functionally annotated genomes of selected endophytic fungal isolates (Fusarium oxysporum, Plectosphaerella cucumerina, Scedosporium apiospermum, Diaporthe eres, Canariomyces subthermophilus) obtained from different tissues of Hypericum spp. The number of predicted type I polyketide synthase (PKS) BGCs in the studied genomes varied. The non-reducing type I PKS lacking thioesterase domain and adjacent discrete gene encoding protein with product release function were identified only in the genomes of C. subthermophilus and D. eres. A candidate bisanthraquinone BGC was predicted in C. subthermophilus genome and comprised genes coding the enzymes that catalyze formation of the basic anthraquinone skeleton (PKS, metallo-beta-lactamase, decarboxylase, anthrone oxygenase), putative dimerization enzyme (cytochrome P450 monooxygenase), other tailoring enzymes (oxidoreductase, dehydrogenase/reductase), and non-catalytic proteins (fungal transcription factor, transporter protein).
The results provide an insight into genetic background of anthraquinone biosynthesis in Hypericum-borne endophytes. The predicted bisanthraquinone gene cluster represents a basis for functional validation of the candidate biosynthetic genes in a simple eukaryotic system as a prospective biotechnological alternative for production of hypericin and related bioactive anthraquinones.
寻找具有抗癌活性的新型生物活性天然化合物仍然非常重要。尽管它们在癌症的诊断和治疗方面的潜力已经得到证实，但可用性仍然有限。金丝桃素是一种从植物源贯叶连翘中分离出来的萘并二蒽酮，以及其他相关的蒽醌和双蒽醌都属于这一类化合物。尽管已经证明金丝桃素是由植物中的聚酮途径合成的，但尚未通过实验验证编码关键酶的候选基因。尽管植物中蒽醌的含量很少，但在微生物中，包括内生真菌中，蒽醌的含量相当普遍。与植物不同，真菌内生菌中的几个生物合成基因已被分组为簇（BGCs），并已得到描述。
本工作的目的是预测、鉴定和表征从不同组织中分离出的内生真菌（尖孢镰刀菌、黄瓜匍柄霉、枝顶孢属、地霉属、嗜热侧孢酵母）的从头组装和功能注释基因组中的蒽醌 BGCs。在所研究的基因组中，预测的 I 型聚酮合酶（PKS） BGC 数量有所不同。仅在 C. subthermophilus 和 D. eres 的基因组中鉴定到缺乏硫酯酶结构域和相邻离散基因的非还原型 I 型 PKS，该基因编码具有产物释放功能的蛋白。在 C. subthermophilus 基因组中预测到一个候选的双蒽醌 BGC，该 BGC 包含催化形成基本蒽醌骨架的酶（PKS、金属β-内酰胺酶、脱羧酶、蒽酮加氧酶）、假定的二聚化酶（细胞色素 P450 单加氧酶）、其他修饰酶（氧化还原酶、脱氢酶/还原酶）和非催化蛋白（真菌转录因子、转运蛋白）的基因。
研究结果深入了解贯叶连翘内生菌中蒽醌生物合成的遗传背景。预测的双蒽醌基因簇为在简单真核系统中对候选生物合成基因进行功能验证提供了依据，这是生产金丝桃素和相关生物活性蒽醌的一种有前景的生物技术替代方法。
