Functional characterization of electron-transferring flavoprotein and its dehydrogenase required for fungal development and plant infection by the rice blast fungus.

Ya Li,Guodong Lu,Qi Zhang,Jindong Zhu,Xuehang Chen,Kunpeng Zhu,Xiaomin Chen,Jiexiong Hu,Zonghua Wang,Xiuli Meng,Guangpu Li

doi:10.1038/srep24911

Abstract

Electron-transferring flavoprotein (ETF) and its dehydrogenase (ETFDH) are highly conserved electron carriers which mainly function in mitochondrial fatty acid β oxidation. Here, we report the identification and characterization of ETF α and β subunit encoding genes (ETFA and ETFB) and ETFDH encoding gene (ETFDH) in the rice blast fungus Magnaporthe oryzae. It was demonstrated that, by impacting fatty acid metabolism, ETF and ETFDH mutations led to severe growth and conidiation defects, which could be largely rescued by exogenous acetate or carbonate. Furthermore, although conidium germination and appressorium formation appeared to be normal in ETF and ETFDH mutants, most appressoria failed to penetrate the host epidermis due to low turgor pressure. The few appressoria that succeeded in penetration were severely restricted in invasive growth and consequently failed to cause disease. Moreover, ETF mutant etfb− induced ROS accumulation in infected host cells and exogenous antioxidant GSH accelerated mutant invading growth without increasing the penetration rate. In addition, mutant etfb− displayed elevated 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 induction of host ROS accumulation.

Highlights

The melanin layer is formed in the outer appressorium to prevent glycerol efflux and maintain the high turgor pressure[7]
Inherited mutations of electron-transferring flavoprotein (ETF) and/or electron-transferring flavoprotein dehydrogenase (ETFDH) can result in multiple acyl-CoA dehydrogenase deficiency (MADD) and disrupt fatty acid β oxidation leading to a series of metabolic disorders[19,23]
ETFA and ETFDH localized to mitochondria (Fig. S8). These results suggested that ETF and ETFDH of M. oryzae function in mitochondrial fatty acid β oxidation

Summary

Introduction

The melanin layer is formed in the outer appressorium to prevent glycerol efflux and maintain the high turgor pressure[7]. The first dehydrogenation step of mitochondrial fatty acid β oxidation is catalyzed by acyl-CoA dehydrogenases. Acyl-CoA dehydrogenases transfer electrons to an electron-transferring flavoprotein (ETF), which, through an electron-transferring flavoprotein dehydrogenase (ETFDH), delivers the electrons to the ubiquinone pool in the terminal respiratory system for ATP synthesis[19,20]. ETF and ETFDH link the fatty acids oxidation with respiratory system. Inherited mutations of ETF and/or ETFDH can result in multiple acyl-CoA dehydrogenase deficiency (MADD) and disrupt fatty acid β oxidation leading to a series of metabolic disorders[19,23]. Our data demonstrate that both ETF and ETFDH play an important role in vegetative growth, conidiation and infection-related development of M. oryzae through regulation of fatty acid metabolism, turgor establishment and host ROS accumulation

Methods

Results

Conclusion