Figure 3.

Populus TUA and TUB gene structure. A, Class I TUAs contain three introns, while class II TUAs have four. Intron positions are conserved within each class, but only the second intron is conserved in all TUA genes (dashed lines denote position conservation). B, All TUB genes have two introns within their coding sequences at conserved positions. Class I members contain an additional intron in the 5′-UTR. Class designation is marked by vertical lines on the left, with a dashed line representing the class I-like TUB group.