Phototrophy and starvation-based induction of autophagy upon removal of Gcn5-catalyzed acetylation of Atg7 in <i>Magnaporthe oryzae</i>

<i>Magnaporthe oryzae</i>, the ascomycete fungus that causes rice blast disease, initiates conidiation in response to light when grown on Prune-Agar medium containing both carbon and nitrogen sources. Macroautophagy/autophagy was shown to be essential for <i>M. oryzae</i> conidiation and induced specifically upon exposure to light but is undetectable in the dark. Therefore, it is inferred that autophagy is naturally induced by light, rather than by starvation during <i>M. oryzae</i> conidiation. However, the signaling pathway(s) involved in such phototropic induction of autophagy remains unknown. We identified an <i>M. oryzae</i> ortholog of <i>GCN5</i> (<i>MGG_03677</i>), encoding a histone acetyltransferase (HAT) that negatively regulates light- and nitrogen-starvation-induced autophagy, by acetylating the autophagy protein Atg7. Furthermore, we unveiled novel regulatory mechanisms on Gcn5 at both transcriptional and post-translational levels, governing its function associated with the unique phototropic response of autophagy in this pathogenic fungus. Thus, our study depicts a signaling network and regulatory mechanism underlying the autophagy induction by important environmental clues such as light and nutrients.