Fig. 4

Developmental stage-specificity of the expression of each gene category classified by gene length (a, c, e, g, i) or gene age grade (b, d, f, h, j) of the five species. Developmental stage-specificity (SS) of a given gene is simply represented by the number of stages in which the gene is expressed. The values of upper and lower quartile are indicated as upper and lower edges of the box, and the values of median are indicated as a red bar in the box. The differences of SS distribution between the neighboring classes are examined by Mann–Whitney U test. The corrected P values are shown in the top of each panel. The P values marked with red color are those less than 0.05. The abbreviations of the gene age grades are the same as those in Fig. 3