ABSTRACTAutophagy is a conserved degradation and recycling pathway in eukaryotes and is important for their normal growth and development. An appropriate status of autophagy is crucial for organisms which is tightly regulated both temporally and continuously. Transcriptional regulation ofautophagy-related genes(ATGs) is an important layer in autophagy regulation. However, the transcriptional regulators and their mechanisms are still unclear, especially in fungal pathogens. Here, we identified Sin3, a component of the histone deacetylase complex, as a transcriptional repressor ofATGsand negative regulator of autophagy induction in the rice fungal pathogenMagnaporthe oryzae. A loss ofSIN3resulted in upregulated expression ofATGsand promoted autophagy with an increased number of autophagosomes under normal growth conditions. Furthermore, we found that Sin3 negatively regulated the transcription ofATG1,ATG13, andATG17through direct occupancy and changed levels of histone acetylation. Under nutrient-deficient conditions, the transcription ofSIN3was downregulated, and the reduced occupancy of Sin3 from thoseATGsresulted in histone hyperacetylation and activated their transcription and in turn promoted autophagy. Thus, our study uncovers a new mechanism of Sin3 in modulating autophagy through transcriptional regulation.IMPORTANCEAutophagy is an evolutionarily conserved metabolic process and is required for the growth and pathogenicity of phytopathogenic fungi. The transcriptional regulators and precise mechanisms of regulating autophagy, as well as whether the induction or repression ofATGsis associated with autophagy level, are still poorly understood inM. oryzae. In this study, we revealed that Sin3 acts as a transcriptional repressor ofATGsto negatively regulate autophagy level inM. oryzae. Under the nutrient-rich conditions, Sin3 inhibits autophagy with a basal level through directly repressing the transcription ofATG1-ATG13-ATG17. Upon nutrient-deficient treatment, the transcriptional level ofSIN3would decrease and dissociation of Sin3 from thoseATGs associates with histone hyperacetylation and activates their transcriptional expression and in turn contributes to autophagy induction. Our findings are important as we uncover a new mechanism of Sin3 for the first time to negatively modulate autophagy at the transcriptional level inM. oryzae.