ABSTRACTAutophagy and apoptosis are evolutionarily conserved catabolic processes involved in regulating development and cellular homeostasis. Bax inhibitor 1 (BI-1) and autophagy protein 6 (ATG6) perform essential functions in these roles, such as cellular differentiation and virulence in various filamentous fungi. However, the functions of ATG6 and BI-1 proteins in development and virulence in the rice false smut fungusUstilaginoidea virensare still poorly understood. In this study, UvATG6 was characterized inU. virens. The deletion ofUvATG6almost abolished autophagy inU. virensand reduced growth, conidial production and germination, and virulence. Stress tolerance assays showed thatUvATG6mutants were sensitive to hyperosmotic, salt, and cell wall integrity stresses but were insensitive to oxidative stress. Furthermore, we found that UvATG6 interacted with UvBI-1 or UvBI-1b and suppressed Bax-induced cell death. We previously found that UvBI-1 could suppress Bax-induced cell death and was a negative regulator of mycelial growth and conidiation. Unlike UvBI-1, UvBI-1b could not suppress cell death.UvBI-1b-deleted mutants exhibited decreased growth and conidiation, while theUvBI-1andUvBI-1bdouble deletion reduced the phenotype, indicating thatUvBI-1andUvBI-1bantagonistically regulate mycelial growth and conidiation. In addition, theUvBI-1band double mutants exhibited decreased virulence. Our results provide evidence of the cross talk of autophagy and apoptosis inU. virensand give clues for studying other phytopathogenic fungi.IMPORTANCEUstilaginoidea virenscauses destructive panicle disease in rice, significantly threatening agricultural production. UvATG6 is required for autophagy and contributes to growth, conidiation, and virulence inU. virens. Additionally, it interacts with the Bax inhibitor 1 proteins UvBI-1 and UvBI-1b. UvBI-1 suppresses cell death induced by Bax, unlike UvBI-1b.UvBI-1negatively regulates growth and conidiation, whileUvBI-1bis required for these phenotypes. These results indicate that UvBI-1 and UvBI-1b may antagonistically regulate growth and conidiation. In addition, both of them contribute to virulence. Additionally, our results suggest cross talk between autophagy and apoptosis, contributing to the development, adaptability, and virulence ofU. virens.