The Pax-homeobox geneeyegoneis involved in the subdivision of the thorax ofDrosophila

Abstract

The eyegone (eyg) gene is known to be involved in the development of the eye structures of Drosophila. We show that eyg and its related gene, twin of eyegone (toe), are also expressed in part of the anterior compartment of the adult mesothorax (notum). We report experiments concerning the role of these genes in the notum. In the absence of eyg function the anterior-central region does not develop, whereas ectopic activity of either eyg or toe induces the formation of the anterior-central pattern in the posterior or lateral region of the notum. These results demonstrate that eyg and toe play a role in the genetic subdivision of the notum, although the experiments indicate that eyg exerts the principal function. However, by itself the Eyg product cannot induce the formation of notum patterns; its thoracic function requires co-expression with the Iroquois (Iro) genes. We show that the restriction of eyg activity to the anterior-central region of the wing disc is achieved by the antagonistic regulatory activities of the Iro and pnr genes, which promote eyg expression, and those of the Hh and Dpp pathways, which act as repressors. We argue that eyg is a subordinate gene of the Iro genes, and that pnr mediates their thoracic patterning function. The activity of eyg gives rise to a new notum subdivision that acts upon the pre-extant one generated by the Iro genes and pnr. As a result the notum becomes subdivided into four distinct genetic domains.

Growth and specification of the eye are controlled independently by Eyegone and Eyeless in Drosophila melanogaster

“…4c,e), which correlated well with the pattern of eyg expression in other imaginal discs (Fig. 3a,d) 30,31,37 .…”

“…Apart from eyg 1 , all new eyg alleles produced various phenotypes unrelated to eye development 30,31,37 (Fig. 4c,e), which correlated well with the pattern of eyg expression in other imaginal discs (Fig.…”

“…We used the following primary antibodies: mAbdac2-3, mAbEya10H6, mAb4D4, mAb24B10 (Developmental Studies Hybridoma Bank), rabbit pH3, rabbit and mouse β-galactosidase, antibody to Distal-less, guinea pig antibody to Eyg (gift from N. Azpiazu; Centro de Biología Molecular, Universidad Autónoma de Madrid, Spain). The antibody to Eyg recognizes both Eyg and the Eyg-like protein Toe 37 . We used secondary antibodies from Jackson and Amersham.…”

“…To test this hypothesis, we assayed the eye-growth capability of flies expressing each Pax6 protein, including Eyg and the novel Eyg-like protein (Toe) encoded by the gene twin of eyegone (toe; also known as CG10704), identified by the Berkeley Drosophila Genome Project. Using ey-GAL4-mediated expression of UAS-regulated Pax transgenes 27,28,37,38 , we compared the eye size of flies coexpressing the Pax proteins and Fng with that of flies expressing Fng alone.…”

The prepattern transcription factor Irx3 directs nephron segment identity

“…Overexpression of Iro-C genes imposes notum differentiation fate on cells of the imaginal wing disc (Wang et al 2000;Aldaz et al 2003). Interestingly, the gain-of-function experiments reported here demonstrate unequivocally that Xenopus irx3 acts as a master regulator of intermediate tubule development that is sufficient to specify intermediate tubule fate in vivo.…”