Department of Plant Pathology, College of Plant Protection, Anhui Agricultural University, 130 West of Changjiang Road, 230036, Hefei, People's Republic of China.
Department of Plant Pathology, College of Plant Protection, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
Curr Genet. 2019 Feb;65(1):223-239. doi: 10.1007/s00294-018-0864-2. Epub 2018 Jun 26.
In fungi, O-mannosylation is one type of conserved protein modifications that add the carbohydrate residues to specific residues of target proteins by protein O-mannosyltransferases. Previously, three members of O-mannosyltransferases were identified in Magnaporthe oryzae, with MoPmt2 playing important roles in fungal growth and pathogenicity. However, the biological roles of the rest Pmt proteins remain unclear. In this study, to understand if O-mannosyltransferases are crucial for fungal pathogenicity of M. oryzae, the Pmt-coding genes MoPmt1 and MoPmt4 were separately disrupted and their roles in pathogenesis were analyzed. Of the two genes, only MoPmt4 is specifically required for full virulence of M. oryzae. Deletion of MoPmt4 resulted in defects on radial growth, with more branching hyphae and septa as compared to Guy11. The MoPmt4 mutant was severely impaired not only in conidiation, but also in both penetration and biotrophic invasion in susceptible rice plants. This mutant also had defects in suppression of host-derived ROS-mediated plant defense responses that might be ascribed from the reduced activities of extracellular enzymes. Furthermore, like their fungi counterparts, MoPmt4 localized in the ER and had O-mannosyltransferase activity. Domain disruption analysis indicated that mannosyltransferase activity regulated by PMT domain of MoPmt4 is crucial for fungal development and pathogenicity of M. oryzae. Taken together, these data suggest that MoPmt4 is a protein O-mannosyltransferase essential for fungal development and full virulence of M. oryzae.
在真菌中，O-甘露糖基化是一种保守的蛋白质修饰类型，通过蛋白质 O-甘露糖基转移酶将碳水化合物残基添加到靶蛋白的特定残基上。先前，在稻瘟病菌中鉴定出三种 O-甘露糖基转移酶成员，MoPmt2 在真菌生长和致病性中起重要作用。然而，其余 Pmt 蛋白的生物学作用仍不清楚。在这项研究中，为了了解 O-甘露糖基转移酶是否对稻瘟病菌的真菌致病性至关重要，分别敲除了编码 Pmt 的基因 MoPmt1 和 MoPmt4，并分析了它们在发病机制中的作用。在这两个基因中，只有 MoPmt4 是稻瘟病菌完全毒力所必需的。MoPmt4 的缺失导致径向生长缺陷，与 Guy11 相比，分枝菌丝和隔膜更多。MoPmt4 突变体不仅在产孢方面受到严重影响，而且在易感水稻植物中的穿透和生物营养入侵方面也受到严重影响。该突变体还在抑制宿主来源的 ROS 介导的植物防御反应方面存在缺陷，这可能归因于细胞外酶活性的降低。此外，与真菌对应物一样，MoPmt4 定位于内质网并具有 O-甘露糖基转移酶活性。结构域破坏分析表明，PMT 结构域调节的甘露糖基转移酶活性对于稻瘟病菌的发育和致病性至关重要。总之，这些数据表明 MoPmt4 是一种蛋白质 O-甘露糖基转移酶，对于稻瘟病菌的发育和完全毒力是必不可少的。
