Figure 6.

Comparison of the severity of nonsynonymous nucleotide polymorphism in modern Arabidopsis populations among function-divergence groups. Average BLOSUM80 score over all nonsynonymous SNPs in each duplicated gene is calculated as a measure of the severity of amino acid changes, with smaller BLOSUM80 scores indicating greater severity. The red lines indicate the genome-wide average of BLOSUM80 scores. A, Comparison of the mean BLOSUM80 scores among function-divergence groups, with error bars indicating se. Mann-Whitney U tests show that there are significantly larger numbers of severe nonsynonymous substitutions in the fully and partially diversified groups than in the conserved group (P = 0.00183 and P = 0.00233). B, Comparison of coding SNP severity and degrees of expression divergence for each duplicated gene pair. Linear regression of the mean BLOSUM80 score is shown as a broken line with the function of the regression line. [See online article for color version of this figure.]