title: The Pax6 genes eyeless and twin of eyeless are required for global patterning of the ocular segment in the Tribolium embryo.
abstract: The transcription factor gene Pax6 is widely considered a master regulator of eye development in bilaterian animals. However, the existence of visual organs that develop without Pax6 input and the considerable pleiotropy of Pax6 outside the visual system dictate further studies into defining ancestral functions of this important regulator. Previous work has shown that the combinatorial knockdown of the insect Pax6 orthologs eyeless (ey) and twin of eyeless (toy) perturbs the development of the visual system but also other areas of the larval head in the red flour beetle Tribolium castaneum. To elucidate the role of Pax6 during Tribolium head development in more detail, we studied head cuticle morphology, brain anatomy, embryonic head morphogenesis, and developmental marker gene expression in combinatorial ey and toy knockdown animals. Our experiments reveal that Pax6 is broadly required for patterning the anterior embryonic head. One of the earliest detectable roles is the formation of the embryonic head lobes, which originate from within the ocular segment and give rise to large parts of the supraesophageal brain including the mushroom body, a part of the posterior head capsule cuticle, and the visual system. We present further evidence that toy continues to be required for the development of the larval eyes after formation of the embryonic head lobes in cooperation with the eye developmental transcription factor dachshund (dac). The sum of our findings suggests that Pax6 functions as a competence factor throughout the development of the insect ocular segment. Comparative evidence identifies this function as an ancestral aspect of bilaterian head development.
authors.affiliation: Department of Biological Sciences, Wayne State University, 5047 Gullen Mall, Detroit, MI 48202, USA; Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR 97403, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Luan
authors.affiliation: Department of Biological Sciences, Wayne State University, 5047 Gullen Mall, Detroit, MI 48202, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Department of Biological Sciences, Wayne State University, 5047 Gullen Mall, Detroit, MI 48202, USA; Department of Anatomy and Cell Biology, Wayne State University, School of Medicine, 540 East Canfield Avenue, Detroit, MI 48201, USA. Electronic address: friedrichm@wayne.edu.
authors.forename: Markus
authors.initials: M
authors.lastname: Friedrich
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000235:genetics / Q000502:physiology*; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D055785:Gene Knockdown Techniques; D006257:Head / Q000196:embryology*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D017403:In Situ Hybridization; D019476:Insect Proteins / Q000378:metabolism*; D008857:Microscopy, Interference; D009024:Morphogenesis / Q000502:physiology*; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014231:Tribolium / Q000196:embryology* / Q000235:genetics
chemical_list: D005136:Eye Proteins; D018398:Homeodomain Proteins; D019476:Insect Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins
keywords: Bilaterian brain; Dachshund; Drosophila; Evolution of development; Eye; Eyeless; Mushroom body; Pax6; Tribolium; Visual system