AUTHOR=Li Ya , Zheng Xiuxia , Zhu Minghui , Chen Mengting , Zhang Shengnan , He Fangyuan , Chen Xiaomin , Lv Jiarui , Pei Mengtian , Zhang Ye , Zhang Yunhui , Wang Wenzong , Zhang Jing , Wang Mo , Wang Zonghua , Li Guangpu , Lu Guodong 

TITLE=MoIVD-Mediated Leucine Catabolism Is Required for Vegetative Growth, Conidiation and Full Virulence of the Rice Blast Fungus Magnaporthe oryzae

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.00444

DOI=10.3389/fmicb.2019.00444

ISSN=1664-302X

ABSTRACT=<p>Isovaleryl-CoA dehydrogenase (IVD), a member of the acyl-CoA dehydrogenase (ACAD) family, is a key enzyme catalyzing the conversion of isovaleryl-CoA to β-methylcrotonyl-CoA in the third reaction of the leucine catabolism pathway and simultaneously transfers electrons to the electron-transferring flavoprotein (ETF) for ATP synthesis. We previously identified the ETF ortholog in rice blast fungus <italic>Magnaporthe oryzae</italic> (<italic>MoETF</italic>) and showed that <italic>MoETF</italic> was essential for fungal growth, conidiation and pathogenicity. To further investigate the biological function of electron-transferring proteins and clarify the role of leucine catabolism in growth and pathogenesis, we characterized <italic>MoIVD</italic> (<italic><underline>M</underline>. <underline>o</underline>ryzae</italic><underline>i</underline>so<underline>v</underline>aleryl-CoA <underline>d</underline>ehydrogenase). MoIvd is highly conserved in fungi and its expression was highly induced by leucine. The Δ<italic>moivd</italic> mutants showed reduced growth, decreased conidiation and compromised pathogenicity, while the conidial germination and appressorial formation appeared normal. Consistent with a block in leucine degradation, the Δ<italic>moivd</italic> mutants accumulated isovaleric acid, grew more slowly, fully lacked pigmentation and completely failed to produce conidia on leucine-rich medium. These defects were largely rescued by raising the extracellular pH, suggesting that the accumulation of isovaleric acid contributes to the growth and conidiation defects. However, the reduced virulence of the mutants was probably due to their inability to overcome oxidative stress, since a large amount of ROS (reactive oxygen species) accumulated in infected host cell. In addition, MoIvd is localized to mitochondria and interacted with its electron receptor MoEtfb, the β subunit of MoEtf. Taken together, our results suggest that <italic>MoIVD</italic> functions in leucine catabolism and is required for the vegetative growth, conidiation and full virulence of <italic>M. oryzae</italic>, providing the first evidence for IVD-mediated leucine catabolism in the development and pathogenesis of plant fungal pathogens.</p>