Figure 4.

Analysis of Population Genomic Data in Arabidopsis Indicates That Rapid Evolution of Stamen in Plants May Be Due to Relaxed Functional Constraint.

(A) SNP densities (number of SNPs per gene per 100 bp) identified from the 80 strains of Arabidopsis show no bias across the seven organs. However, genes with higher tissue specificity contain more SNPs than those with lower tissue specificity.

(B) Genes expressed in stamen and seed have higher ratios of nonsynonymous SNPs to synonymous SNPs than do those expressed in vegetative organs.

(C) The fractions of rapidly evolving genes in stamen and seed are higher than in vegetative organs. The rapidly evolving genes were defined as the genes with more nonsynonymous SNPs than synonymous SNPs.

(D) The ratios of interspecific protein divergence rates versus the intraspecific variation rates (rates of nonsynonymous SNPs versus synonymous SNPs) in the seven organs.