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Morphological features of organismal body plans are often highly conserved within large taxa. For example, segmentation is a shared and defining feature of all insects. Screens in Drosophila identified genes responsible for the development of body segments, including the "pair-rule" genes (PRGs), which subdivide embryos into double-segment units in a previously unexpected pre-patterning step. Here we show that the milkweed bug Oncopeltus fasciatus also uses a pair rule for embryo subdivision but Oncopeltus employs different genes for this process. We identified the gene Blimp1 as an Oncopeltus PRG based on its expression pattern, tested its function with RNA interference and CRISPR-Cas9, and generated the first PR mutant in this species. Although it does not have PR function in Drosophila , like Drosophila PRGs, Blimp1 encodes a transcription factor required for embryonic viability. Thus, pair-rule subdivision of the insect body plan is more highly conserved than the factors mediating this process, suggesting a developmental constraint on this pre-patterning step.

Insects display a vast array of eye and body colors. Genes encoding products involved in biosynthesis and deposition of pigments are ideal genetic markers, contributing, for example, to the power of Drosophila genetics. Oncopeltus fasciatus is an emerging model for hemimetabolous insects, a member of the piercing-sucking feeding order Hemiptera, that includes pests and disease vectors. To identify candidate visible markers for O. fasciatus, we used parental and nymphal RNAi to identify genes that altered eye or body color while having no deleterious effects on viability. We selected Of-vermilion for CRISPR/Cas9 genome editing, generating three independent loss-of-function mutant lines. These studies mapped Of-vermilion to the X-chromosome, the first assignment of a gene to a chromosome in this species. Of-vermilion homozygotes have bright red, rather than black, eyes and are fully viable and fertile. We used these mutants to verify a role for Of-xdh1, ortholog of Drosophila rosy, in contributing to red pigmentation using RNAi. Rather than wild-type-like red bodies, bugs lacking both vermilion and xdh1 have bright yellow bodies, suggesting that ommochromes and pteridines contribute to O. fasciatus body color. Our studies generated the first gene-based visible marker for O. fasciatus and expanded the genetic toolkit for this model system., (© 2023. The Author(s).)

Background: Halyomorpha halys (Stål), the brown marmorated stink bug, is a highly invasive insect species due in part to its exceptionally high levels of polyphagy. This species is also a nuisance due to overwintering in human-made structures. It has caused significant agricultural losses in recent years along the Atlantic seaboard of North America and in continental Europe. Genomic resources will assist with determining the molecular basis for this species' feeding and habitat traits, defining potential targets for pest management strategies., Results: Analysis of the 1.15-Gb draft genome assembly has identified a wide variety of genetic elements underpinning the biological characteristics of this formidable pest species, encompassing the roles of sensory functions, digestion, immunity, detoxification and development, all of which likely support H. halys' capacity for invasiveness. Many of the genes identified herein have potential for biomolecular pesticide applications., Conclusions: Availability of the H. halys genome sequence will be useful for the development of environmentally friendly biomolecular pesticides to be applied in concert with more traditional, synthetic chemical-based controls.

The discovery of pair-rule genes (PRGs) in Drosophila revealed the existence of an underlying two-segment-wide prepattern directing embryogenesis. The milkweed bug Oncopeltus fasciatus , a hemimetabolous insect, is a more representative arthropod: most of its segments form sequentially after gastrulation. Here, we report the expression and function of orthologs of the complete set of nine Drosophila PRGs in Oncopeltus Seven Of -PRG-orthologs are expressed in stripes in the primordia of every segment, rather than every other segment; Of-runt is PR-like and several orthologs are also expressed in the segment addition zone. RNAi-mediated knockdown of Of-odd-skipped , paired and sloppy-paired impacted all segments, with no indication of PR-like register. We confirm that Of - E75A is expressed in PR-like stripes, although it is not expressed in this way in Drosophila , demonstrating the existence of an underlying PR-like prepattern in Oncopeltus These findings reveal that a switch occurred in regulatory circuits, leading to segment formation: while several holometabolous insects are ' Drosophila -like', using PRG orthologs for PR patterning, most Of- PRGs are expressed segmentally in Oncopeltus , a more basally branching insect. Thus, an evolutionarily stable phenotype - segment formation - is directed by alternate regulatory pathways in diverse species., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2019. Published by The Company of Biologists Ltd.)