Abstract
Regulatory genes are often multifunctional and constrained, which results in evolutionary conservation. It is difficult to understand how a regulatory gene could be lost from one species’ genome when it is essential for viability in closely related species. The gene paired is a classic Drosophila pair-rule gene, required for formation of alternate body segments in diverse insect species. Surprisingly, paired was lost in mosquitoes without disrupting body patterning. Here, we demonstrate that a paired family member, gooseberry, has acquired paired-like expression in the malaria mosquito Anopheles stephensi. Anopheles-gooseberry CRISPR-Cas9 knock-out mutants display pair-rule phenotypes and alteration of target gene expression similar to what is seen in Drosophila and beetle paired mutants. Thus, paired was functionally replaced by the related gene, gooseberry, in mosquitoes. Our findings document a rare example of a functional replacement of an essential regulatory gene and provide a mechanistic explanation of how such loss can occur.
Highlights
Regulatory genes are often multifunctional and constrained, which results in evolutionary conservation
Drosophila melanogaster (Dmel)-Prd’s pair-rule function is shared by beetles, the only other member of this clade in which functional tests have been carried out. These results apply to two long-diverged beetle species, the flour beetle, Tribolium castaneum (Tcas), and the hide beetle Dermestes maculatus (Dmac)
We demonstrate that gsb has taken on the functionality of prd through analysis of a gsb loss-offunction mutant line, that we generated by CRISPR-Cas[9]
Summary
Regulatory genes are often multifunctional and constrained, which results in evolutionary conservation. Drosophila melanogaster (Dmel) segmentation genes paired (prd) and gooseberry (gsb), encoding paralogous Pax3/7 family transcription factors, were among the first genes demonstrated to have diverged by subfunctionalization[3]. Both genes were discovered in a genetic screen in Drosophila for embryonic lethal mutations that disrupt body patterning. In light of the evolutionary conservation of prd as a pair-rule gene, it was surprising that prd was predicted to be absent in early versions of mosquito genomes and transcriptomes[16] This loss was puzzling because of Prd’s essential role in segmentation and embryonic viability in both closely related Dipterans (flies) as well as other more distantly diverged insects, as mentioned above. In mosquitoes, gsb has seamlessly replaced prd in the segmentation gene network
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
