Genomic map and orientation of CBF's (A), and gene structures and polymorphism illustrations of CBF1 (B), CBF2 (C) and CBF3 (D). (A): Promoter regions are represented by horizontal lines and transcriptional units (TUs) are indicated by boxes. Bold lines indicate sequenced promoter regions. Grey boxes indicated coding regions. The arrows above TUs represent direction of transcription. The starting and ending positions of CBF TU are indicated (M: mega base pair) based on AtDB Sequence Map. (B), (C), and (D): Promoter regions are represented by horizontal lines, and TUs are indicated by boxes (UTR: white boxes; coding region: labeled boxes). Lines and triangles above the gene structure respectively indicate polymorphisms and indels which are informative, and those below the gene structure indicate singletons; black circles are nonsynonymous substitutions; numbers next to the black circles represents number of nonsynonymous substitutions. Boxes with diamonds are nuclear localization signals; boxes with diagonal lines indicate the AP2 domain; gray boxes with diagonal lines are alpha-helix motifs; heavy gray boxes are transcriptional activation domains; dotted boxes are not functionally defined. Gray lines parallel to the gene structures represent long indel in non-coding regions, coding regions with amino acid deletions (CBF1) and a loss of complete open reading frame (CBF2). See "Materials and methods" and additional files 2, 3, 4. The scale bars indicate 100 bp.