Area of Microbiology, University of León, Campus de Ponferrada, Ponferrada, Spain.
National Center for Agricultural Utilization Research, United States Department of Agriculture, Peoria, IL, USA.
Appl Microbiol Biotechnol. 2019 Oct;103(19):8087-8103. doi: 10.1007/s00253-019-10047-2. Epub 2019 Aug 5.
Trichothecenes are sesquiterpene toxins produced by diverse fungi, including some species of Trichoderma that are potential plant disease biocontrol agents. Trichoderma arundinaceum produces the trichothecene harzianum A (HA), which consists of the core trichothecene structure (12,13-epoxytrichothec-9-ene, EPT) with a linear polyketide-derived substituent (octa-2,4,6-trienedioyl) esterified to an oxygen at carbon atom 4. The genes required for biosynthesis of EPT and the eight-carbon polyketide precursor of the octa-2,4,6-trienedioyl substituent, as well as for esterification of the substituent to EPT have been described. However, genes required for conversion of the polyketide (octa-2,4,6-trienoic acid) to octa-2,4,6-trienedioyl-CoA, the immediate precursor of the substituent, have not been described. Here, we identified 91 cytochrome P450 monooxygenase genes in the genome sequence of T. arundinaceum, and provided evidence from gene deletion, complementation, cross-culture feeding, and chemical analyses that one of them (tri23) is required for conversion of octa-2,4,6-trienoic acid to octa-2,4,6-trienedioyl-CoA. The gene was detected in other HA-producing Trichoderma species, but not in species of other fungal genera that produce trichothecenes with an octa-2,4,6-trienoic acid-derived substituent. These findings indicate that tri23 is a trichothecene biosynthetic gene unique to Trichoderma species, which in turn suggests that modification of octa-2,4,6-trienoic acid during trichothecene biosynthesis has evolved independently in some fungi.
多环芳烃是由多种真菌产生的倍半萜毒素，包括一些潜在的植物病害生物防治剂曲霉菌。木霉菌产生的哈茨木霉 A（HA），它由核心多环芳烃结构（12,13-环氧曲霉菌-9-烯，EPT）与线性聚酮衍生的取代基（辛-2,4,6-三烯酰基）酯化在碳原子 4 上的氧上组成。已经描述了用于 EPT 生物合成和辛-2,4,6-三烯酰基取代基的八碳聚酮前体的基因，以及将取代基酯化到 EPT 的基因。然而，用于将聚酮（辛-2,4,6-三烯酸）转化为取代基的辛-2,4,6-三烯酰基-CoA 的前体的基因尚未描述。在这里，我们在木霉菌的基因组序列中鉴定了 91 个细胞色素 P450 单加氧酶基因，并通过基因缺失、互补、交叉培养喂养和化学分析提供了证据，证明其中一个（tri23）是将辛-2,4,6-三烯酸转化为辛-2,4,6-三烯酰基-CoA 所必需的。该基因在其他产生 HA 的曲霉菌种中被检测到，但在产生具有辛-2,4,6-三烯酸衍生取代基的多环芳烃的其他真菌属种中未被检测到。这些发现表明 tri23 是一种独特的多环芳烃生物合成基因，仅存在于曲霉菌种中，这反过来表明多环芳烃生物合成过程中辛-2,4,6-三烯酸的修饰在某些真菌中是独立进化的。
