Area of Microbiology, University School of Agricultural Engineers, University of León, Campus de Ponferrada, Avda. Astorga s/n, 24400 Ponferrada, Spain.
Appl Environ Microbiol. 2011 Jul;77(14):4867-77. doi: 10.1128/AEM.00595-11. Epub 2011 Jun 3.
Trichothecenes are mycotoxins produced by Trichoderma, Fusarium, and at least four other genera in the fungal order Hypocreales. Fusarium has a trichothecene biosynthetic gene (TRI) cluster that encodes transport and regulatory proteins as well as most enzymes required for the formation of the mycotoxins. However, little is known about trichothecene biosynthesis in the other genera. Here, we identify and characterize TRI gene orthologues (tri) in Trichoderma arundinaceum and Trichoderma brevicompactum. Our results indicate that both Trichoderma species have a tri cluster that consists of orthologues of seven genes present in the Fusarium TRI cluster. Organization of genes in the cluster is the same in the two Trichoderma species but differs from the organization in Fusarium. Sequence and functional analysis revealed that the gene (tri5) responsible for the first committed step in trichothecene biosynthesis is located outside the cluster in both Trichoderma species rather than inside the cluster as it is in Fusarium. Heterologous expression analysis revealed that two T. arundinaceum cluster genes (tri4 and tri11) differ in function from their Fusarium orthologues. The Tatri4-encoded enzyme catalyzes only three of the four oxygenation reactions catalyzed by the orthologous enzyme in Fusarium. The Tatri11-encoded enzyme catalyzes a completely different reaction (trichothecene C-4 hydroxylation) than the Fusarium orthologue (trichothecene C-15 hydroxylation). The results of this study indicate that although some characteristics of the tri/TRI cluster have been conserved during evolution of Trichoderma and Fusarium, the cluster has undergone marked changes, including gene loss and/or gain, gene rearrangement, and divergence of gene function.
单端孢霉烯族化合物是由木霉属、镰刀菌属和至少四个其他在真菌Hypocreales 目中的属产生的霉菌毒素。镰刀菌属具有一个单端孢霉烯族化合物生物合成基因（TRI）簇，该簇编码运输和调节蛋白以及形成霉菌毒素所需的大多数酶。然而，对于其他属中的单端孢霉烯族化合物生物合成知之甚少。在这里，我们鉴定并表征了木霉属和短密木霉中的 TRI 基因直系同源物（tri）。我们的结果表明，这两个木霉种都有一个 tri 簇，该簇由存在于镰刀菌 TRI 簇中的七个基因的直系同源物组成。簇中基因的组织在两个木霉种中是相同的，但与镰刀菌中的组织不同。序列和功能分析表明，负责单端孢霉烯族化合物生物合成第一步的基因（tri5）位于两个木霉种的簇外，而不是像在镰刀菌中那样位于簇内。异源表达分析表明，两个木霉属簇基因（tri4 和 tri11）在功能上与它们的镰刀菌直系同源物不同。Tatri4 编码的酶仅催化四个氧合反应中的三个，而其在镰刀菌中的同源酶则催化四个。Tatri11 编码的酶催化的反应与 Fusarium 中的酶（单端孢霉烯族化合物 C-15 羟化）完全不同（单端孢霉烯族化合物 C-4 羟化）。本研究结果表明，尽管 tri/TRI 簇的某些特征在木霉属和镰刀菌属的进化过程中得到了保守，但该簇发生了明显的变化，包括基因丢失和/或获得、基因重排和基因功能的分化。
