Structure of the NAC transcription factor. A: Typical NAC transcription factor, with N-terminal NAC domain, consisting of five conserved subdomains, A-E. The C-terminal part of the protein is more variable and contains the transcriptional activation or repressing region. B: Several variations on the typical NAC transcription factors can be found. A number of characterized NAC proteins have a conserved transmembrane motive, TM, in the far C-terminal region. Other variations include proteins with NAC domain only or proteins with the NAC domain in the C-terminal.