Differences in gene expression patterns between parthenogenetically and sexually produced offspring during early...

Social insects exhibit reproductive division of labour, governed by both external and internal factors influencing caste determination. In termites with a unique reproductive system known as asexual queen succession (AQS), queens produce neotenic queens via parthenogenesis, while workers and alates arise through sexual reproduction. This inherent caste differentiation bias may have resulted from differences in gene expression potentially influenced by the parent-of-origin effect, as parthenogenetic daughters inherit only maternal genomes, while sexually produced daughters inherit both paternal and maternal genomes. Here, we show that gene expression patterns in developing embryos of the termite Reticulitermes speratus differ significantly between parthenogenetic and sexually produced offspring. However, SNP analysis indicated that these differences were not attributable to the parent-of-origin effect. Through RNA-seq analysis of female embryos post-katatrepsis, we identified 21 genes, including jhbp, nlk, and wge, which are known to be involved in caste differentiation and morphogenesis, with significant expression differences between parthenogenetic and sexually produced daughters. SNP analysis of sexually produced embryos did not reveal any parent-of-origin biased expression except for mitochondrial genes, though 12 genes exhibited colony-specific expression patterns. These findings suggested that early developmental gene expression partly explained caste differentiation biases. Further research is essential to elucidate the molecular mechanisms behind these transgenerational effects, providing insight into the evolution of AQS and complex caste determination in social insects from a gene expression perspective.