Molecular traces of alternative social organization in a termite genome

Although eusociality evolved independently within several orders of insects, research into the molecular underpinnings of the transition towards social complexity has been confined primarily to Hymenoptera (for example, ants and bees). Here we sequence the genome and stage-specific transcriptomes of the dampwood termite Zootermopsis nevadensis (Blattodea) and compare them with similar data for eusocial Hymenoptera, to better identify commonalities and differences in achieving this significant transition. We show an expansion of genes related to male fertility, with upregulated gene expression in male reproductive individuals reflecting the profound differences in mating biology relative to the Hymenoptera. For several chemoreceptor families, we show divergent numbers of genes, which may correspond to the more claustral lifestyle of these termites. We also show similarities in the number and expression of genes related to caste determination mechanisms. Finally, patterns of DNAmethylation and alternative splicing support

The neuropeptide corazonin controls social behavior and caste identity in ants

Social insects are emerging models to study how gene regulation affects behavior because their colonies comprise individuals with the same genomes but greatly different behavioral repertoires. To investigate the molecular mechanisms that activate distinct behaviors in different castes, we exploit a natural behavioral plasticity in Harpegnathos saltator, where adult workers can transition to a reproductive, queen-like state called gamergate. Analysis of brain transcriptomes during the transition reveals that corazonin, a neuropeptide homologous to the vertebrate gonadotropin-releasing hormone, is downregulated as workers become gamergates. Corazonin is also preferentially expressed in workers and/or foragers from other social insect species. Injection of corazonin in transitioning Harpegnathos individuals suppresses expression of vitellogenin in the brain and stimulates worker-like hunting behaviors, while inhibiting gamergate behaviors, such as dueling and egg deposition. We propose that corazonin is a central regulator of caste identity and behavior in social insects.R.B. acknowledges support from the NIH (DP2MH107055), the Searle Scholars Program (15-SSP-102), the March of Dimes Foundation (1-FY-15-344), a Linda Pechenik Montague Investigator Award, and the Charles E. Kaufman Foundation (KA2016-85223). E.J.S. acknowledges financial support from the NIH (T32HG000046). The ant projects in the laboratories of S.L.B., D.R., and J.L. were funded by a Howard Hughes Medical Institute Collaborative Innovation Award (#2009005). T.A.L. was supported by an NSF award (IOS-1452520). H.Y. was supported by the NIH F32 postdoctoral fellowship (F32AG044971)