Transcriptional regulation of secondary metabolism and autophagy genes in response to DNA replication stress in Setosphaeria turcica

The fungal pathogen Setosphaeria turcica causes northern corn leaf blight(NCLB),which leads to considerable crop losses.Setosphaeria turcica elaborates a specialized infection structures called appressorium for maize infection.Previously,we demonstrated that the S.turcica triggers an S-phase checkpoint and ATR(Ataxia Telangiectasia and Rad3 related)-dependent self-protective response to DNA genotoxic insults during maize infection.However,how the regulatory mechanism works was still largely unknown.Here,we report a genome wide transcriptional profile analysis during appressorium formation in the present of DNA replication stress.We performed RNA-Seq analysis to identify S.tuicica genes responsive to DNA replication stress.In the current work,we found that appressorium-mediated maize infection by S.turcica is significantly blocked by S-phase checkpoint.A large serial of secondary metabolite and melanin biosynthesis genes were blocked in appressorium formation of S.turcica during the replication stress.The secondary metabolite biosynthesis genes including alcohol dehydrogenase GroES-like domain,multicopper oxidase,ABCtransporter families,cytochrome P450 and FAD-containing monooxygenase were related to plant pathogen infection.In addition,we demonstrated that autophagy in S.turcica is up-regulated by ATR as a defense response to stress.We identified StATG3,StATG4,StATG5,StATG7 and StATG16 genes for autophagy were induced by ATR-mediated S-phase checkpoint.We therefore propose that in response to genotoxic stress,S.turcica utilizes ATR-dependent pathway to turn off transcription of genes governing appressorium-mediated infection,and meanwhile inducing transcription of autophagy genes likely as a mechanism of self-protection,aside from the more conservative responses in eukaryotes.