Functional involvement of multiple genes as members of the supergene unit in the female-limited Batesian mimicry of Papilio polytes

Abstract

Supergenes are sets of genes and genetic elements that are inherited like a single gene and control complex adaptive traits, but their functional roles and units are poorly understood. In Papilio polytes, female-limited Batesian mimicry is thought to be regulated by a ~130kb inversion region (highly diversified region: HDR) containing three genes, UXT, U3X and doublesex (dsx) which switches non-mimetic and mimetic types. To determine the functional unit, we here performed electroporation-mediated RNAi analyses (and further Crispr/Cas9 for UXT) of genes within and flanking the HDR in pupal hindwings. We first clarified that non-mimetic dsx-h had a function to switch from male to non-mimetic female and only dsx-H isoform 3 had an important function in the formation of mimetic traits. Next, we found that UXT was involved in making mimetic type pale-yellow spots and adjacent gene sir2 removed excess red spots in hindwings, both of which refine more elaborate mimicry. Furthermore, downstream gene networks of dsx, U3X and UXT screened by RNA sequencing showed that U3X upregulated dsx expression and repressed UXT expression. These findings demonstrate that a set of multiple genes, not only inside but also flanking HDR, can function as supergene members, which extends the definition of supergene unit than we considered before. Also, our results indicate that dsx-H functions as the switching gene and some other genes such as UXT and sir2 within the supergene unit work as the modifier gene. Article summarySupergenes are thought to control complex adaptive traits, but their detailed function are poorly understood. In Papilio polytes, female-limited Batesian mimicry is regulated by an ~130kb inversion region (highly divergent region: HDR) containing three genes. Our functional analysis showed that doublesex switches the mimicry polymorphism, and that an inside gene UXT and an outside gene sir2 to the HDR work to refine more elaborate mimicry. We here succeed in defining the unit of mimicry supergene and some novel modifier genes.