The eyeless homeodomain is dispensable for eye development in Drosophila

Pax-6 genes, known to be essential for eye development, encode an evolutionarily conserved transcription factor with two DNA-binding domains. To corroborate the contribution of each DNA-binding domain to eye formation, we generated truncated forms of the Drosophila Pax-6 gene eyeless and tested their capacity to rescue the ey² mutant. Surprisingly, EY deleted of the homeodomain rescued the ey² mutant and triggered ectopic eyes morphogenesis. In contrast, EY lacking the paired domain failed to rescue the ey² mutant, led to truncation of appendages, and repressed Distal-less when misexpressed. This result suggests distinct functions mediated differentially by the two DNA-binding domains of eyeless.