| Electron-transferring flavoprotein (ETF) and its dehydrogenase (ETFDH) are highly conserved electron carriers and specifically function in mitochondrial fatty acid β oxidation. Here, we report the identification and characterization of two ETF encoding genes(ETFA and ETFE) and one ETFDH encoding gene(ETFDH) by Agrobacterium tumefaciens T-DNA insertion and gene knockout in the rice blast fungus Magnaporthe oryzae. It was demonstrated that the ETF and ETFDH mutations led to severe growth and conidiation defects by impacting fatty acid metabolism, which could be largely rescued by exogenous NaAC or Na2CO3. Furthermore, although the conidial germination and appressorial formation appeared normal in the mutants, most appressoria failed to penetrate host epidermis due to low turgor pressure caused by melanin deficiency, and even a few that succeeded in penetration were severely restricted in invasive growth and consequently failed to cause disease. Moreover, the mutants induced massive ROS accumulation in infected host cells and exogenous antioxidant GSH could accelerate invasive growth of the mutants without increasing the penetration rate. Additionally, the mutants displayed lipid body accumulation and reduced ATP synthesis. Taken together, ETF and ETFDH play an important role in fungal development and plant infection in M. oryzae by regulation of fatty acid metabolism, turgor establishment and host oxidative stress responses. |
