Identification of transcription factors that regulate ATG8 expression and autophagy in Arabidopsis

Autophagy is a conserved catabolic process in eukaryotes that contributes to cell survival in response to multiple stresses and is important for organism fitness. In Arabidopsis thaliana, the core machinery of autophagy is well defined, but its transcriptional regulation is largely unknown. The ATG8 (autophagy-related 8) protein plays central roles in decorating autophagosomes and binding to specific cargo receptors to recruit cargo to autophagosomes. We propose that the transcriptional control of ATG8 genes is important during the formation of autophagosomes and therefore contributes to survival during stress. Here, we describe a yeast one-hybrid (Y1H) screen for transcription factors (TFs) that regulate ATG8 gene expression in Arabidopsis, using the promoters of 4 ATG8 genes. We identified a total of 225 TFs from 35 families that bind these promoters. The TF-ATG8 promoter interactions revealed a wide array of diverse TF families for different promoters, as well as enrichment for families of TFs that bound to specific fragments. These TFs are not only involved in plant developmental processes but also in the response to environmental stresses. TGA9 (TGACG (TGA) motif-binding protein 9)/AT1G08320 was confirmed as a positive regulator of autophagy. TGA9 overexpression activated autophagy under both control and stress conditions and transcriptionally up-regulated expression of ATG8B, ATG8E and additional ATG genes via binding to their promoters. Our results provide a comprehensive resource of TFs that regulate ATG8 gene expression and lay a foundation for understanding the transcriptional regulation of plant autophagy.