Figure 4.

Tandem duplication and fusion of CA genes in sorghum. Postulated evolution of sorghum CA genes through four tandem duplication events and a gene fusion event is displayed. We show distribution and structures of CA genes, and their peptide-encoding exons, on sorghum chromosome 3. Genes are shown as the large arrows with differently colored outlines and exons are shown as colored blocks contained in the arrows. Homologous exons are in the same color. A chloroplast transit peptide is in dark red. A tandem duplication event is shown by two small black arrows pointing in divergent directions, and a gene fusion event is shown by two small black arrows pointing in convergent directions. A new gene produced by tandem duplication is shown with an arrow in a new color not used by the ancestral genes. A gene produced by fusion of two neighboring genes is shown as a bipartite structure, each part with the color of one of the fused genes. A stop codon mutation is shown by a lightning-bolt symbol, and an exon-splitting event by a narrow triangle.