Assembling the genome of a bat (Epomophorus labiatus) with an XO sex determination system
Several members of the Pteropodidae family of bats are among the few mammals described without a Y chromosome. In these animals, sex is presumably determined by the dosage of the X chromosome. Additionally, bat genomes can reveal the genes involved with viral tolerance, as bats are notably asymptomatic to certain viruses. Therefore, we assembled the genome of a male epauletted fruit bat (Epomophorus labiatus) using Pacbio HiFi reads and Hi-C sequencing data to generate chromosome-scale scaffolds. The resulting assembly spans 2.1 billion bases, with a BUSCO completeness score of 99.56%. With visualization tools PretextView and HiGlass, we manually curated the assembly into 17 autosomes and an X chromosome. Annotation was performed with TSEBRA, which integrates gene predictions from the TOGA2 and Stringtie pipelines. These annotations will enable us to perform comparative genomics to identify positively-selected immune-related genes across bat lineages. Additionally, we plan to obtain a karyotype from samples collected in Uganda to confirm the absence of a Y chromosome in this species. We are currently identifying the genes under selection that facilitate this XO sex determination, including genes found on autosomes that are present on Y chromosomes in other bat species. Ultimately, this work will increase our understanding of the evolution of mammalian sex determination and the evolutionary genomics of bat immunity.