Particularly, otd is required for the development of the dorsal region of the adult Drosophila head, that forms from the fusion of two eye-antennal discs.
Rapid expression of otd in all OPRs and IPRs is found following neuronal cell specification in the late larval stage and persists through photoreceptor differentiation.
In later development of pupation through to adulthood, otd activates light detecting rhodopsin proteins Rh3 and Rh5 in IPRs while repressing Rh6 in OPRs.
[1][7] Groucho-independent repression of otd by runt, a pair-rule gene, has also been observed in the anterior and posterior regions of the syncytial and cellular blastoderm.
[11] Another characteristic of the oc phenotype is the abnormal or deleted bristles in the ocellus region,[12] which relates back to the wild type otd gene’s role in mediating anterior patterning.