Genome-wide identification of DNA double-strand break repair genes and transcriptional modulation in response to benzo[α]pyrene in the monogonont rotifer Brachionus spp

•Rotifer DSB repair genes were separated into the same groups, showing clear orthologous relationship.•Brachionus spp. DSB repair genes have less numbers of exon/intron compared to A. vaga.•In B. koreanus, DSBs and DSB repair induced by B[α]P were observed.•The expression of Ku70, Ku80, RECQL5, and TOP3A was downregulated at 10 μg/L B[α]P. The DNA repair system has evolved from the common ancestor of all life forms and its function is highly conserved within eukaryotes. In this study, to reveal the role of DNA double-strand break repair (DSB) genes in response to benzo[α]pyrene (B[α]P), we first identified DSB genes in relation to homologous recombination and non-homologous end joining events in four Brachionus rotifer spp.: B. calyciflorus, B. koreanus, B. plicatilis, and B. rotundiformis. In all the Brachionus spp., 39 orthologous genes to human DSB repair genes were identified. Furthermore, three genes in B. koreanus, two genes in B. plicatilis, and one gene in B. calyciflorus and B. rotundiformis were present as duplicated genes, indicating that these genes were diversified over speciation in the genus Brachionus. Moreover, we compared DSB repair genes on the gene structures in four monogonont Brachionus rotifers and the bdelloid rotifer Adineta vaga, which possesses highly efficient DNA repair ability. The transcriptional responses of four monogonont Brachionus rotifers in response to B[α]P exposure showed how B[α]P exposure led to DSBs and subsequently recruited DNA DSB repair pathways in the rotifer B. koreanus. Taken together, this study provides a better understanding of the potential role of DSB repair genes in the monogonont rotifer Brachionus spp. in response to B[α]P.