A single synonymous nucleotide change impacts the male-killing phenotype of prophage WO gene wmk
AbstractWolbachia are the most widespread bacterial endosymbionts in animals. Within arthropods, these maternally-transmitted bacteria can selfishly hijack host reproductive processes to increase the relative fitness of their transmitting females. One such form of reproductive parasitism called male killing, or the selective killing of infected males, is recapitulated to degrees by transgenic expression of the WO-mediated killing gene wmk. Here, we characterize the genotype-phenotype landscape of wmk-induced male killing in D. melanogaster. While phylogenetically distant wmk homologs induce no sex-ratio bias, closely-related homologs exhibit complex phenotypes spanning no death, male death, or death of all hosts. We demonstrate that alternative start codons and, notably, one synonymous mutation in wmk can ablate killing. These findings reveal previously unrecognized relationships of wmk-induced killing and establish new hypotheses for the impacts of post-transcriptional processes in wmk-induced male killing. We conclude that single synonymous sequence changes are not necessarily silent in important nested symbiotic interactions.