The Mitochondrial Distribution and Morphology Family 33 Gene FgMDM33 Is Involved in Autophagy and Pathogenesis in Fusarium graminearum

The mitochondrial distribution and morphology family 33 gene (<i>MDM33</i>) regulates mitochondrial homeostasis by mediating the mitochondrial fission process in yeast. The wheat head blight <i>Fusarium graminearum</i> contains an FgMdm33 protein that is orthologous to <i>Saccharomyces cerevisiae</i> Mdm33, albeit its function remains unknown. We have reported here the roles of FgMdm33 in regulating fungal morphogenesis, mitochondrial morphology, autophagy, apoptosis, and fungal pathogenicity. The Δ<i>Fgmdm33</i> mutants generated through a homologous recombination strategy in this study exhibited defects in terms of mycelial growth, conidia production, and virulence. Hyphal cells lacking <i>FgMDM33</i> displayed elongated mitochondria and a dispensable respiratory-deficient growth phenotype, indicating the possible involvement of <i>FgMDM33</i> in mitochondrial fission. The Δ<i>Fgmdm33</i> mutants displayed a remarkable reduction in the proteolysis of GFP-FgAtg8, whereas the formation of autophagic bodies in the hyphal cells of mutants was recorded under the induction of mitophagy. In addition, the transcriptional expression of the apoptosis-inducing factor 1 gene (<i>FgAIF1</i>) was significantly upregulated in the Δ<i>Fgmdm33</i> mutants. Cumulatively, these results indicate that <i>FgMDM33</i> is involved in mitochondrial fission, non-selective macroautophagy, and apoptosis and that it regulates fungal growth, conidiation, and pathogenicity of the head blight pathogen.