Transcription Factor Evolution Associated with Social Transitions in Blattodea

The phenotypic diversity between castes in social species has been associated with increased regulation of gene expression. while the regulatory role of transcription factors (TFs) in the social transitions of Hymenoptera (bees, ants and wasps) is well studied, it remains poorly explored in Blattodea (cockroaches and termites). By analysing three cockroach and five termite genomes, we show that while Blattodea share some convergent regulatory signatures with Hymenoptera, their transition is mostly characterised by distinct regulatory changes. We identified convergent patterns such as TF families with more relaxed selection compared to intensified selection and lineage-specific gene family expansions in termites, which has also been reported in Hymenoptera. There are also key differences in Blattodea TF regulation in comparison with Hymenoptera with contractions in TF gene families and no compensatory changes in TF DNA binding motifs either in frequency or diversity in TF promoter regions. Furthermore, we show that an increase in social complexity associates with greater diversity in TF activating domains, one of the evolutionary and structural building blocks of TFs; meanwhile, DNA-binding domains, undergo very little change. This study highlights similarities in social transitions between Hymenoptera and Blattodea, with evidence of large changes in transcriptional regulation followed by lineage specific adaptations. Our results indicate that at least in the case of Blattodea, the transcriptional diversity linked to social complexity is not attributable to transcription factors alone, but is instead likely driven in combination with alternative mechanisms.