Two Pax genes,eye goneandeyeless, act cooperatively in promotingDrosophilaeye development

Abstract

We report the identification of a Drosophila Pax gene, eye gone (eyg), which is required for eye development. Loss-offunction eyg mutations cause reduction or absence of the eye. Similar to the Pax6 eyeless (ey) gene, ectopic expression of eyg induces extra eye formation, but at sites different from those induced by ey. Several lines of evidence suggest that eyg and ey act cooperatively: (1) eyg expression is not regulated by ey, nor does it regulate ey expression, (2) eyginduced ectopic morphogenetic furrow formation does not require ey, nor does ey-induced ectopic eye production require eyg, (3) eyg and ey can partially substitute for the function of the other, and (4) coexpression of eyg and ey has a synergistic enhancement of ectopic eye formation. Our results also show that eyg has two major functions: to promote cell proliferation in the eye disc and to promote eye development through suppression of wg transcription.

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.…”

“…4a,b), intermediate combinations resulted in consistent eye loss or tiny eyes (Fig. 4c) and stronger combinations caused head loss and hence were lethal 31 (Fig. 4d,e).…”

“…Mouse Pax6 can substitute for D. melanogaster Ey in the formation of ectopic eyes 28 , and D. melanogaster Ey or Toy can induce vertebrate-type eyes in the frog embryo 29 . The gene eyegone (eyg) encodes a Pax6-like protein (Eyg) 10 with a truncated paired domain, lacking most of the N terminus 30,31 ( Fig. 1a).…”

“…Biochemical studies showed that Eyg binds through the C terminus of the paired domain to a 5aCON-like site 30 , which corresponds to the high-affinity binding site for mammalian Pax splice isoforms, such as PAX6(5a) [18][19][20] . Eyg is characterized as an eye-specifying factor [31][32][33] , and overexpression studies suggested that Eyg and Ey might substitute for each other functionally 31 . Because the two proteins have distinct paired domain structures (Fig.…”