Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), Faculty of Natural and Agricultural Sciences, University of Pretoria, South Africa.
Department of Zoology and Entomology, FABI, Faculty of Natural and Agricultural Sciences, University of Pretoria, South Africa.
Fungal Biol. 2021 Dec;125(12):1036-1047. doi: 10.1016/j.funbio.2021.07.002. Epub 2021 Jul 9.
Fusarium circinatum is an important pathogen of pine trees. However, little is known regarding the molecular processes underlying its pathogenesis. We explored the potential role of the phytotoxin fusaric acid (FA) in the pathogenicity of the fungus. FA is produced by products of the FUB biosynthesis gene cluster, containing FUB1-12. Of these, FUB1 encodes the core polyketide synthase, which we disrupted. We used the resulting mutant strain to investigate whether FUB1 and FA production play a role in the virulence of F. circinatum on pine. Our results showed that FA production was abolished both in vitro and in planta. However, bikaverin production was increased in the knockout mutant. FUB1 disruption also corresponded with downregulation of a F. circinatum homologue of LaeA, a master transcriptional regulator of secondary metabolism. Lesion lengths produced by the FUB1 knockout mutant on inoculated Pinus patula seedlings were significantly smaller than those produced by the wild type strain. Collectively, these results show that FUB1 plays a role in FA production in F. circinatum, and that this gene contributes to the aggressiveness of F. circinatum on P. patula. This study will contribute to the limited knowledge we have about the molecular basis of pathogenicity in this fungus.
尖孢镰刀菌是松树的重要病原体。然而，人们对其致病机制的分子过程知之甚少。我们探讨了植物毒素镰刀菌酸（FA）在真菌致病性中的潜在作用。FA 是由 FUB 生物合成基因簇的产物产生的，该基因簇包含 FUB1-12。其中，FUB1 编码核心聚酮合酶，我们对其进行了破坏。我们使用由此产生的突变株来研究 FUB1 和 FA 产生是否在尖孢镰刀菌对松树的毒力中起作用。我们的结果表明，FA 的产生无论是在体外还是在体内都被完全消除。然而，在敲除突变体中，bikaverin 的产生增加了。FUB1 缺失也与 LaeA 的尖孢镰刀菌同源物的下调相对应，LaeA 是次级代谢物的主要转录调控因子。FUB1 敲除突变体在接种的辐射松幼苗上产生的病变长度明显小于野生型菌株产生的病变长度。总的来说，这些结果表明 FUB1 在尖孢镰刀菌的 FA 产生中起作用，并且该基因有助于尖孢镰刀菌在辐射松上的侵袭性。本研究将有助于我们对该真菌致病机制的有限认识。
