Accessory-gland expression level and X-linkage. (A) Boxplots show the distribution of the accessory gland expression level (S) for genes on each chromosome arm in D. melanogaster (chromosome 4 was omitted). (Boxes) Interquartile range; (horizontal line in the middle of the boxes) median value; (whiskers) 1.5× the interquartile range (outliers were omitted), (dashed line) genome-wide average. Genes were divided into those with accessory-gland-biased expression (τ > 0.7) or those that are broadly expressed (τ ≤ 0.4). Significant differences in the expression level for a given chromosome and the rest of the genome were assessed using a Mann-Whitney test; (*) P < 0.05; (**) P < 0.005. (B) D. melanogaster genes were divided into those with low expression in accessory gland (S < 100), moderate expression in accessory gland (100 ≤ S < 1000), and highly expressed in accessory gland (S ≥ 1000). Within each panel is shown the percent of genes with female-biased (F), male-biased (M), and unbiased (U) expression that are X-linked. Genes were assigned to sex-biased expression classes using RNA-seq data (BWA alignments and edgeR to call differential expression). (*) Observed values that significantly differ from the expectation based on the size of the X chromosome as determined by a permutation test; (*) P < 0.05, (**) P < 0.01, (***) P < 0.001.
