Colour pattern specification in the Mocker swallowtail Papilio dardanus : the transcription factor invected is a candidate for the mimicry locus H

Abstract

The swallowtail butterfly, Papilio dardanus , is an iconic example of a polymorphic Batesian mimic. The expression of various female-limited colour forms is thought to be controlled by a single autosomal locus, termed H , whose function in determining the wing pattern remains elusive. As a step towards the physical mapping of H , we established a set of 272 polymorphic amplified fragment length polymorphism (AFLP) markers ( Eco RI- Mse I). Segregation patterns in a ‘female-informative’ brood (exploiting the absence of crossing over in female Lepidoptera) mapped these AFLPs to 30 linkage groups (putative chromosomes). The difference between the hippocoon and cenea female forms segregating in this family resides on a single one of these linkage groups, defined by 14 AFLPs. In a ‘male-informative’ cross (markers segregating within a linkage group), a pair of AFLPs co-segregated closely with the two female forms, except in four recombinants out of 19 female offspring. Linkage with these AFLP markers using four further female-informative families demonstrated that the genetic factor determining other morphs ( poultoni , lamborni and trimeni ) also maps to this same linkage group. The candidate gene invected , obtained in a screen for co-segregation of developmental genes with the colour forms, resides in a 13.9 cM interval flanked by the two AFLP markers. In the male-informative family invected co-segregated perfectly with the hippocoon / cenea factor, despite the four crossovers with the AFLPs. These findings make invected , and possibly its closely linked paralogue engrailed , strong candidates for H . This is supported by their known role in eyespot specification in nymphalid butterfly wings.

Development and evolution of insect pigmentation: Genetic mechanisms and the potential consequences of pleiotropy

“…These expression differences could be caused by cis-regulatory changes in the genes examined or by changes in their transcriptional activators. Although specific genetic changes have not yet been identified, studies mapping the genetic basis of variable wing pigmentation are consistent with changes at pleiotropic regulatory genes: Distal-less is associated with quantitative variation in eyespot size in Bicyclus anynana [31], wingless is associated with wing color in hybrids of Heliconius species [32], and engrailed/invected is associated with wing pattern polymorphism in Papilio dardanus [33]. Increased mapping resolution and/or functional analyses are ultimately needed to separate the effects of these candidate genes from linked loci.…”

Supergenes and their role in evolution

“…Intermediates between morphs are rare to non-existent, and clear dominance hierarchies exist within populations (Ford, 1964;Nijhout, 2003). The H locus has been physically mapped through linkage mapping and SNP-association analysis to a narrow region that includes the candidate genes engrailed and invected (Timmermans et al, personal communication, Clark et al, 2008). In contrast to the situation in H. numata, however, there is no clear evidence for a region of reduced recombination and only limited evidence for enhanced linkage disequilibrium.…”

yellow and ebony Are the Responsible Genes for the Larval Color Mutants of the Silkworm Bombyx mori

“…To determine the responsible genes for color pattern polymorphisms or mutants, an AFLP-based linkage map has been developed in several butterfly species (reviewed in Beldade et al 2008). Recently, the linkage of forewing color pattern and mate preference with the wingless gene in two Heliconius species (Kronforst et al 2006) and the linkage of the mimicry locus H with the invected gene in Papilio dardanus have been reported (Clark et al 2008), although these reports have not elucidated whether wingless or invected is the responsible gene for wing color pattern variation. Until now, no color pattern genes have been elucidated by positional cloning in Lepidoptera.…”