Gene Regulatory Network Reconstruction to Decipher the Molecular Mechanisms Governing Bacteriocyte-Based Symbioses.

Intracellular bacteria with beneficial roles for their hosts are present in more than 10% of all insect species. In intracellular nutritional symbioses, these symbionts are typically confined to specialized host cells known as bacteriocytes. Bacteriocytes are remarkable novel cells that arose independently and repeatedly across multiple insect lineages. They are fascinating structures, yet the molecular mechanisms regulating their development, function and even their evolutionary origins, remain largely unknown. Nonetheless, an important role for certain transcription factors in development and homeostasis of bacteriocytes has been highlighted by several studies, hinting at the importance of the transcriptional networks regulated by them. Gene Regulatory Network (GRN) inference facilitates discovery of regulatory interactions underlying complex biological processes, as first shown in the model species Drosophila melanogaster and subsequently successfully applied to several other insect species. Here, we propose de novo computational inference as a strategy to reconstruct GRNs of bacteriocytes. We propose that the pea aphid Acyrthosiphon pisum is best suited to establish the first comparative framework for reconstructing and analyzing GRNs that control bacteriocyte development, function and death. This framework in turn can serve for evo-devo studies, by extending these analyses to other aphids, to other hemipterans and, more broadly, to other insects harboring bacteriocytes.