Recent approaches lead to a deeper understanding of diverse segmentation mechanisms in insects, with a focus on the pair-rule genes

The division of the insect embryo into repeated units — segments — is a fundamental feature of the body plan. The genes controlling this process in Drosophila melanogaster were identified in genetic screens and characterized in that species in numerous studies in the 1980s and 1990s. These genes form a well-established hierarchy and have been leveraged to examine gene regulation, transcriptional machinery, chromatin structure, and more. Much of the genetic toolkit identified in Drosophila is highly conserved throughout the animal kingdom, spearheading the field of evolutionary developmental biology or Evo-Devo. Accordingly, a ‘Drosophila-centric’ approach has examined the evolutionary conservation of orthologs of Drosophila segmentation genes in closely and distantly related insects. Here, we report on progress in both Drosophila and emerging model insects in recent years (2022 to present), with much of the new research related to the pair-rule subset of segmentation genes. We highlight new findings on ‘classic’ Drosophila genes, revealing unexpected roles of genes and cis-regulatory elements in this species. We further report on the expanding knowledge about mechanisms regulating to segmentation in emerging model insects that are distantly related to Drosophila, including those that pattern segments sequentially. We also describe technical advances in both Drosophila and nonmodel species that are currently progressing research in this field. •Technical innovations allow live imaging of transcriptional dynamics in embryos.•Digging deeper brought new insights into Drosophila gene regulation and function.•Insects use multiple modes of segment formation relying on a changing gene cohort.•Much remains to be learned about the evolution of insect segmentation mechanisms.