Binary cell fate decisions and fate transformation in the Drosophila larval eye

摘要

Controlling cellular diversity requires a complex interplay of transcription factors. Using the Drosophila larval eye as genetic model we identify distinct mechanisms of how binary cell fate decisions are made, how sensory receptor gene expression is regulated and how cell fate identity is switched during metamorphosis. We show that the transcription factor Senseless fulfills three temporally and functionally separable roles in the same cells by (1) initiating a binary cell fate decision by controlling the cell fate determinants Spalt and Seven-up, (2) suppressing apoptosis during metamorphosis and (3) promoting Rhodopsin expression after metamorphosis. We further show that the transcription factor Hazy provides is required for early embryonic PR differentiation and that maintained Hazy expression is essential for Rhodopsin expression. Hazy provides a third function during metamorphosis by repressing Sens in one PR-subtype allowing it to undergo apoptotic cell death. We identified a novel mode of Rhodopsin regulation in which the highly conserved RCSI motif is dispensable for expression, demonstrating that the regulation of the Rhodopsin promoter is distinct in different visual organs. Our findings provide a unique example of how the same regulators control very distinct key aspects of development at distinct stages.