Abstract
Although all insects are segmented, the genes that control this process vary across species. Many of the pair-rule (PR) genes that direct segment formation in Drosophila are similarly utilized in other holometabolous insects, but more distantly related species use different genes for PR-patterning. Previously, we showed that Lepidoptera lack a highly conserved PR-gene, paired. Here, we used the painted lady butterfly Vanessa cardui as a lepidopteran model to explore the expression and function of PR-genes in this large clade of moths and butterflies. Orthologs of four Drosophila PR-genes are expressed in PR-like stripes and at least one displays PR-like function. Neither of the two genes that have PR-function in Hemiptera but not in Drosophila have PR-roles in Vanessa. Rather, the hemipteran PR-gene Blimp1 functions in a novel fashion in abdominal segmentation in Vanessa . Thus, while butterflies appear to share PR-patterning mechanisms with other insects, they utilize only a subset of the Drosophila PR-gene orthologs and have not taken on hemipteran PR-orthologs for this process. These findings suggest extensive rewiring of the segmentation gene regulatory network in Lepidoptera.
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