Phylogenetic trees and relative expression ratios of the genes at the Z-locus (A) and the S-locus (B). The phylogenetic trees and relative expression ratios are ordered according to the physical gene order as seen in Lolium perenne L. genotype Kyuss, and gene expression data is from the genotype S23 Z. The flanking genes are boxed in gray, whereas the self-incompatibility candidate genes are boxed in teal and blue. The scale bar in the top left corner represents one amino acid change per site, and the legend below shows the color code for the three tissue types used in the gene expression analysis. For the LpsS, LpsZ, and the SI-DUF247s, the relative expression ratio measurement was explicitly performed for each allele present in the genotype. The two different alleles are displayed stacked on top of each other. For the remaining S- and Z-locus genes, the expression pattern was investigated with primers amplifying both alleles, and therefore only one polar plot is presented per gene. Only data points were included where the C_t difference was below 0.5, and the percent deviation was below 3% between the two technical replicates. Therefore, the standard error is not displayed in the figure.