title: Over-expression of Ultrabithorax alters embryonic body plan and wing patterns in the butterfly Bicyclus anynana.
abstract: In insects, forewings and hindwings usually have different shapes, sizes, and color patterns. A variety of RNAi experiments across insect species have shown that the hox gene Ultrabithorax (Ubx) is necessary to promote hindwing identity. However, it remains unclear whether Ubx is sufficient to confer hindwing fate to forewings across insects. Here, we address this question by over-expressing Ubx in the butterfly Bicyclus anynana using a heat-shock promoter. Ubx whole-body over-expression during embryonic and larvae development led to body plan changes in larvae but to mere quantitative changes to adult morphology, respectively. Embryonic heat-shocks led to fused segments, loss of thoracic and abdominal limbs, and transformation of head limbs to larger appendages. Larval heat-shocks led to reduced eyespot size in the expected homeotic direction, but neither additional eyespots nor wing shape changes were observed in forewings as expected of a homeotic transformation. Interestingly, Ubx was found to be expressed in a novel, non-characteristic domain - in the hindwing eyespot centers. Furthermore, ectopic expression of Ubx on the pupal wing activated the eyespot-associated genes spalt and Distal-less, known to be directly repressed by Ubx in the fly׳s haltere and leg primordia, respectively, and led to the differentiation of black wing scales. These results suggest that Ubx has been co-opted into a novel eyespot gene regulatory network, and that it is capable of activating black pigmentation in butterflies.
authors.affiliation: Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511, USA; State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China. Electronic address: xiaoling.tonger@gmail.com.
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Tong
authors.affiliation: Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Hrycaj
authors.affiliation: Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511, USA.
authors.forename: Ondrej
authors.initials: O
authors.lastname: Podlaha
authors.affiliation: Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA.
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Popadic
authors.affiliation: Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511, USA; Department of Biological Sciences, National University of Singapore, Singapore 117543; Yale-NUS College, Singapore 138614. Electronic address: antonia.monteiro@nus.edu.sg.
authors.forename: Antónia
authors.initials: A
authors.lastname: Monteiro
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning / Q000502:physiology*; D002080:Butterflies / Q000196:embryology* / Q000378:metabolism; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D018869:Heat-Shock Response / Q000502:physiology; D018398:Homeodomain Proteins / Q000378:metabolism*; D007814:Larva / Q000378:metabolism / Q000502:physiology; D010858:Pigmentation / Q000235:genetics / Q000502:physiology; D060888:Real-Time Polymerase Chain Reaction; D014157:Transcription Factors / Q000378:metabolism*; D014921:Wings, Animal / Q000196:embryology* / Q000378:metabolism
chemical_list: D017931:DNA Primers; D018398:Homeodomain Proteins; D014157:Transcription Factors
keywords: Bicyclus anynana; Eyespot; Homeotic transformation; Over-expression; Ultrabithorax; Wing