Abstract
In recent years, many examples have been reported in which complex adaptive traits are regulated by supergene units consisting of multiple genes adjacent to each other on the chromosome. However, few supergene units have been functionally characterized, and it has not been demonstrated that multiple genes in a supergene unit are involved in the adaptive trait. The H locus on chromosome 25 has been shown to be responsible for the female-limited Batesian mimicry in Papilio polytes. The mimetic H locus, about 130 kb, is inverted at both ends from the non-mimetic h locus, and the sequences between H and h locus are diversified (Highly Diversified Region: HDR). The HDR of the H locus contains three genes, doublesex (dsx), U3X, and UXT, and RNAi analyses have shown that dsx is involved in the mimetic pattern formation. Here, we showed that knockdown by RNAi and knockout by Crspr/Cas9 of the transcriptional regulator UXT altered the mimetic pattern to the non-mimetic like pattern in hindwings. In addition, it was also shown by RNAi that long non-coding RNA U3X was functionally involved in the mimetic pattern formation, and by RNA-seq analysis that U3X induced the dsx expression and repressed the UXT expression. In addition, the knockdown of prospero and sir2 genes adjacent to the HDR also affected the hindwing pattern formation. These results indicate that not only genes within the HDR but also adjacent genes outside the HDR may be involved in the mimicry supergene function. This suggests that cis-elements regulating multiple gene expression exists within the HDR of the H-allele, and the need to consider a more extended functional unit of the supergene. This paper shows that multiple genes inside and outside the HDR are functionally involved in the formation of complex adaptive traits, and provides a new perspective on the evolution of the structure and functional units of the supergene.
Competing Interest Statement
The authors have declared no competing interest.