Figure 2

Intron-exon structure of Myb genes. (a) Locations of introns 1 and 2 splice sites in R2R3 domains. Six representative Myb R2R3 domain sequences are shown. The extent of the R2 and R3 repeats is indicated at bottom of the alignment. The triangles indicate the positions of the splice sites, and the numbers above the triangles indicate the phases of introns. Subgroup G13 represents the major splicing pattern; that is, 77 (of 130) Myb genes in Arabidopsis, and 45 (of 85) Myb genes in rice have this splicing pattern. The shaded W residues indicate the regularly spaced tryptophan residues. The representative sequences of the six subgroups are: G13, At1g57560; G12, At2g32460; G16, At4g32730; N08, Scaffold479_5; N19, At2g39880; N21, At2g25230. The table at the right of the alignment lists the number of Myb genes with each splicing pattern and the total number of Myb genes in Arabidopsis and rice. Note that 22 Arabidopsis and 18 rice genes have the typical G13 splicing pattern, except that they lack either intron 1 or intron 2. Additionally, six Arabidopsis and 12 rice genes have no introns within the R2R3 domain. Finally, two Arabidopsis and four rice Myb genes have other atypical splicing patterns (data not shown). (b,c) The conserved exon-intron structure of all member genes in subgroups G13 and N21. Boxes and lines indicate exons and introns, respectively. Additional examples are provided in Additional data file 8.