Arabidopsis ethylene-responsive element binding factors act as transcriptional activators or repressors of GCC box-mediated gene expression

Ethylene-responsive element binding factors (ERFs) are members of a novel f amily of transcription factors that are specific to plants, A highly conser ved DNA binding domain known as the ERF domain is the unique feature of thi s protein family, To characterize in detail this family of transcription fa ctors, we isolated Arabidopsis cDNAs encoding five different ERF proteins ( AtERF1 to AtERF5) and analyzed their structure, DNA binding preference, tra nsactivation ability, and mRNA expression profiles, The isolated AtERFs wer e placed into three classes based on amino acid identity within the ERF dom ain, although all five displayed GCC box-specific binding activity. AtERF1, AtERF2, and AtERF5 functioned as activators of GCC box-dependent transcrip tion in Arabidopsis leaves, By contrast, AtERF3 and AtERF4 acted as repress ors that downregulated not only basal transcription levels of a reporter ge ne but also the transactivation activity of other transcription factors. Th e AtERF genes were differentially regulated by ethylene and by abiotic stre ss conditions, such as wounding, cold, high salinity, or drought, via ETHYL ENE-INSENSITIVE2 (EIN2)-dependent or -independent pathways, Cycloheximide, a protein synthesis inhibitor, also induced marked accumulation of AtERF mR NAs, Thus, we conclude that AtERFs are factors that respond to extracellula r signals to modulate GCC box-mediated gene expression positively or negati vely.