Perturbation of DNA repair gene expression due to interspecies hybridization

The effect of interspecies hybridization on gene regulation was examined using real-time polymerase chain reaction (RT-PCR) to measure the expression of five base-excision repair genes in brain, eye, gill, liver, and tailfin tissues from Xiphophorus parental species and F1 hybrids. Relative mRNA levels of uracil N-glycosylase (Ung), Apurinic/apyrimidinic endonuclease (Ape1), polymerase-β (Polb), flap endonuclease (Fen1), and DNA ligase (Lig1) were measured in three parental Xiphophorus species (X. maculatus Jp 163 B, X. helleri Sarabia, and X. andersi andC) and in two interspecies F1 hybrids, the Sp-helleri hybrid (X. maculatus Jp 163 B×X. helleri Sarabia) and the Sp-andersi hybrid (X. maculatus Jp 163 B×X. andersi) to identify genes that undergo changes in expression levels upon interspecies hybridization. Significant differences in gene expression were observed between parental animals and their respective F1 hybrids in both interspecies crosses. Generally, marked increases in DNA repair gene mRNA levels were observed across all tissues in F1 hybrid animals from the Sp-helleri cross compared to either X. maculatus or X. helleri parents. In contrast, the Sp-andersi F1 hybrid animals generally exhibited decreased base-excision repair gene expression, although this trend was more specific to individual tissues than observed for Sp-helleri hybrids.