Differential Expression of Hormone-Related Genes in the Heads of Adult and Nymphal Woodroaches (Cryptocercus)

Termites are eusocial cockroaches, but the crucial distinctions in gene expression during the evolution of eusociality remain unclear. One reason for the lack of this information is that comparative transcriptome analysis of termites with their sister group, the cockroach genus Cryptocercus, has not been conducted. We identified genes associated with three vital hormones (juvenile hormone [JH], 20-hydoroxyecdysone [20E], and insulin) from the genome sequence of Cryptocercus punctulatus and conducted RNA-seq analysis using the heads of female/male adults and nymphs to elucidate their expression levels. The comprehensive gene expression analysis revealed a multitude of genes exhibiting differences in expression between developmental stages rather than between sexes. Subsequently, we compared the differences in expression patterns of each hormone-related gene by combining the results of a previous RNA-seq study conducted on the heads of castes (reproductives, workers, and soldiers) in the termite Reticulitermes speratus. The results indicated that genes with expression differences among castes in R. speratus, particularly those related to JH and 20E, were significantly more abundant compared to genes with expression differences between adults and nymphs in C. punctulatus. While no significant difference was observed in the number of genes within the insulin signaling pathway, a trend of homologs highly expressed in adult woodroaches but not in adult termites was observed, and the expression patterns of positive and negative regulators in the pathway differed significantly between adults and nymphs. The differences in the expression patterns between Cryptocercus and termites are believed to reflect variations in hormone levels and signaling activities between adults and juveniles, the latter encompassing workers and soldiers in the case of termites.