Fig. 4

Model building of 3D structure of wheat expansin protein TaEXPA1-A. The N-termintal conserved domain I and C-termintal conserved domain II were marked in blue and pink, respectively. Sites responsible for both functional divergence and positive selection are marked as colored red while sites responsible for coevolution are marked as colored yellow. a The overall view of critical amino acid sites on the three-dimensional structure. b View of critical amino acid sites on the surface of TaEXPA1-A. Four amino acid sites responsible for both functional divergence and positive selection, five groups amino acid sites related to co-evolution are located on the surface of the 3D structure. c 3D structure rotated 180° to show different view sides of the expansin