Unravelling the biosynthesis of pyriculol in the rice blast fungus Magnaporthe oryzae
作者:Stefan Jacob、Thomas Grötsch、Andrew J Foster、Anja Schüffler、Patrick H Rieger、Louis P Sandjo、Johannes C Liermann、Till Opatz、Eckhard Thines
DOI:10.1099/mic.0.000396
日期:2017.4.1
Pyriculol was isolated from the rice blast fungus Magnaporthe oryzae and found to induce lesion formation on rice leaves. These findings suggest that it could be involved in virulence. The gene MoPKS19 was identified to encode a polyketide synthase essential for the production of the polyketide pyriculol in the rice blast fungus M. oryzae. The transcript abundance of MoPKS19 correlates with the biosynthesis rate of pyriculol in a time-dependent manner. Furthermore, gene inactivation of MoPKS19 resulted in a mutant unable to produce pyriculol, pyriculariol and their dihydro derivatives. Inactivation of a putative oxidase-encoding gene MoC19OXR1, which was found to be located in the genome close to MoPKS19, resulted in a mutant exclusively producing dihydropyriculol and dihydropyriculariol. By contrast, overexpression of MoC19OXR1 resulted in a mutant strain only producing pyriculol. The MoPKS19 cluster, furthermore, comprises two transcription factors MoC19TRF1 and MoC19TRF2, which were both found individually to act as negative regulators repressing gene expression of MoPKS19. Additionally, extracts of ΔMopks19 and ΔMoC19oxr1 made from axenic cultures failed to induce lesions on rice leaves compared to extracts of the wild-type strain. Consequently, pyriculol and its isomer pyriculariol appear to be the only lesion-inducing secondary metabolites produced by M. oryzae wild-type (MoWT) under these culture conditions. Interestingly, the mutants unable to produce pyriculol and pyriculariol were as pathogenic as MoWT, demonstrating that pyriculol is not required for infection.
吡菌醇是从水稻稻瘟病菌中分离出来的,发现它能够诱导水稻叶片形成病斑。这些发现表明它可能与致病性有关。MoPKS19基因被确定为编码一种多聚酮合成酶,该酶对于水稻稻瘟病菌中多聚酮吡菌醇的产生至关重要。MoPKS19的转录丰度与吡菌醇的生物合成速率呈时间依赖性相关。此外,MoPKS19基因的失活导致突变体无法产生吡菌醇、吡菌醇及其二氢衍生物。假定的氧化酶编码基因MoC19OXR1的失活导致突变体仅产生二氢吡菌醇和二氢吡菌醇。相比之下,MoC19OXR1的过度表达导致突变株仅产生吡菌醇。此外,MoPKS19簇包括两个转录因子MoC19TRF1和MoC19TRF2,它们都被单独发现作为负调控因子抑制MoPKS19的基因表达。此外,与野生型菌株的提取物相比,由无菌培养物制成的ΔMopks19和ΔMoC19oxr1的提取物未能诱导水稻叶片形成病斑。因此,吡菌醇及其异构体吡菌醇似乎是野生型(MoWT