Regulatory gene function handoff allows essential gene loss in mosquitoes

• Published in: Communications biology Vol. 3; no. 1; p. 540
• Main Authors: Cheatle Jarvela, Alys M., Trelstad, Catherine S., Pick, Leslie
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 30.09.2020; Nature Publishing Group
• Subjects: 14/32; 45/70; 631/136/756; 631/181/2806; 64/24; Anopheles stephensi; Biology; Biomedical and Life Sciences; CRISPR; Culicidae; Drosophila; Evolutionary conservation; Gene expression; Genomes; Insects; Life Sciences; Malaria; Mosquitoes; Mutants; Paired gene; Phenotypes; Species
• ISSN: 2399-3642; 2399-3642
• DOI: 10.1038/s42003-020-01203-w

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. Cheatle Jarvela et al. demonstrate in the mosquito Anopheles stephensi that the paired gene was functionally replaced by the gene gooseberry , even though paired is essential in other insects such as fruit flies and beetles. This study contributes to the understanding of how essential genes are lost despite their importance during development.