title: Distal-less regulates eyespot patterns and melanization in Bicyclus butterflies.
abstract: Butterfly eyespots represent novel complex traits that display substantial diversity in number and size within and across species. Correlative gene expression studies have implicated a large suite of transcription factors, including Distal-less (Dll), Engrailed (En), and Spalt (Sal), in eyespot development in butterflies, but direct evidence testing the function of any of these proteins is still missing. Here we show that the characteristic two-eyespot pattern of wildtype Bicyclus anynana forewings is correlated with dynamic progression of Dll, En, and Sal expression in larval wings from four spots to two spots, whereas no such decline in gene expression ensues in a four-eyespot mutant. We then conduct transgenic experiments testing whether over-expression of any of these genes in a wild-type genetic background is sufficient to induce eyespot differentiation in these pre-patterned wing compartments. We also produce a Dll-RNAi transgenic line to test how Dll down-regulation affects eyespot development. Finally we test how ectopic expression of these genes during the pupal stages of development alters adults color patters. We show that over-expressing Dll in larvae is sufficient to induce the differentiation of additional eyespots and increase the size of eyespots, whereas down-regulating Dll leads to a decrease in eyespot size. Furthermore, ectopic expression of Dll in the early pupal wing led to the appearance of ectopic patches of black scales. We conclude that Dll is a positive regulator of focal differentiation and eyespot signaling and that this gene is also a possible selector gene for scale melanization in butterflies.
authors: Department of Biological Sciences, University at Buffalo, Buffalo, New York, USA. antonia.monteiro@yale.edu
authors: Antónia
authors: A
authors: Monteiro
authors: Bin
authors: B
authors: Chen
authors: Diane M
authors: DM
authors: Ramos
authors: Jeffrey C
authors: JC
authors: Oliver
authors: Xiaoling
authors: X
authors: Tong
authors: Min
authors: M
authors: Guo
authors: Wen-Kai
authors: WK
authors: Wang
authors: Lisa
authors: L
authors: Fazzino
authors: Firdous
authors: F
authors: Kamal
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002080:Butterflies / Q000235:genetics / Q000254:growth & development; D003116:Color; D015536:Down-Regulation; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics; D007814:Larva / Q000235:genetics / Q000254:growth & development; D009024:Morphogenesis / Q000235:genetics*; D010858:Pigmentation / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics; D014921:Wings, Animal / Q000254:growth & development* / Q000378:metabolism
chemical_list: D018398:Homeodomain Proteins; D014157:Transcription Factors