@article {Long2022.07.15.500229, author = {Lijiang Long and Wen Xu and Annalise B. Paaby and Patrick T. McGrath}, title = {A Toxin-Antidote Selfish Element Increases Fitness of its Host}, elocation-id = {2022.07.15.500229}, year = {2022}, doi = {10.1101/2022.07.15.500229}, publisher = {Cold Spring Harbor Laboratory}, abstract = {Selfish genetic elements can promote their transmission at the expense of individual survival, creating conflict between the element and the rest of the genome. Recently, a large number of toxin-antidote (TA) post-segregation distorters have been identified in non-obligate outcrossing nematodes. Their origin and the evolutionary forces that keep them at intermediate population frequencies are poorly understood. Here, we study a TA element in C. elegans called peel-1/zeel-1. Two major haplotypes of this locus, with and without the selfish element, segregate in C. elegans. Here we study the fitness consequences of the peel-1/zeel-1 element outside of its role in gene drive in non-outcrossing animals. We demonstrate that loss of the toxin peel-1 decreased fitness of hermaphrodites and resulted in reductions in fecundity and body size. This fitness advantage is independent of the antidote zeel-1, suggesting that a distinct peel-1 pathway plays a biological role. This work demonstrates that a TA element can provide a fitness benefit to its hosts, either during their initial evolution or by being co-opted by the animals following their selfish spread. These findings guide our understanding on how TA elements can remain in a population where gene drive is minimized, helping resolve the mystery of prevalent TA elements in selfing animals.Competing Interest StatementThe authors have declared no competing interest.}, URL = {https://www.biorxiv.org/content/early/2022/07/15/2022.07.15.500229}, eprint = {https://www.biorxiv.org/content/early/2022/07/15/2022.07.15.500229.full.pdf}, journal = {bioRxiv} }