Allelic asymmetry of the Lethal hybrid rescue (Lhr) gene expression in the hybrid between Drosophila melanogaster and D. simulans: confirmation by using genetic variations of D. melanogaster

Abstract

In the cross between Drosophila melanogaster females and D. simulans males, hybrid males die at the late larval stage, and the sibling females also die at later stages at high temperatures. Removing the D. simulans allele of the Lethal hybrid rescue gene (Lhr (sim) ) improves the hybrid incompatibility phenotypes. However, the loss-of-function mutation of Lhr (sim) (Lhr (sim0) ) does not rescue the hybrid males in crosses with several D. melanogaster strains. We first describe the genetic factor possessed by the D. melanogaster strains. It has been suggested that removing the D. melanogaster allele of Lhr (Lhr (mel) ), that is Lhr (mel0) , does not have the hybrid male rescue effect, contrasting to Lhr (sim0) . Because the expression level of the Lhr gene is known to be Lhr (sim) > Lhr (mel) in the hybrid, Lhr (mel0) may not lead to enough of a reduction in total Lhr expression. Then, there is a possibility that the D. melanogaster factor changes the expression level to Lhr (sim) < Lhr (mel) . But in fact, the expression level was Lhr (sim) > Lhr (mel) in the hybrid irrespectively of the presence of the factor. At last, we showed that Lhr (mel0) slightly improves the viability of hybrid females, which was not realized previously. All of the present results are consistent with the allelic asymmetry model of the Lhr gene expression in the hybrid.

Variable post‐zygotic isolation in Drosophila melanogaster/D. simulans hybrids

“…Taking the same approach as in Gérard & Presgraves () and Shirata et al . (), we scored the number of offspring produced in interspecific crosses. Vials were tended by standard fly husbandry methods.…”

“…Studies of hybrids between these two species have led to great advancements in our understanding of the genetic basis of hybrid inviability (Hutter & Ashburner, ; Sawamura & Yamamoto, , ; Sawamura et al ., ,b; Coyne et al ., ; Barbash et al ., , ; Presgraves, ; Presgraves et al ., ; Ferree & Barbash, ; Tang & Presgraves, ). However, the variance of the hybrid inviability trait due to effects of genetic background is unknown (but see Watanabe et al ., and Shirata et al ., ).…”

Gene Regulation and Speciation

“…Supporting this hypothesis, transcriptional differences between Lhr orthologs in hybrids has been linked to compensatory cis -by- trans divergence between species in allele-specific expression [92,93]. …”

A Test of Double Interspecific Introgression of Nucleoporin Genes in Drosophila

“…Interestingly, dominance of Nup96 sim was changed by the presence of a balancer TM3 ( Table 4 ). Reproductive isolation might be easily affected by the genetic background, as has been suggested in the other hybrid incompatibility ( Lhr vs. Hmr ) in the same species cross ( Matute et al 2014 ; Shirata et al 2014 ). Finally, double introgression carrying homozygous Nup96 sim and hemizygous Nup160 sim resulted in lethality in the hybrids ( Table 4 and Figure 1E ).…”