Ets-related protein that functions as a negative regulator of photoreceptor development acting antagonistically to pnt and the proneural signal mediated by RAS (PubMed:1505027, PubMed:1495974, PubMed:8033205). It acts upstream of SINA to inhibit R7 development (PubMed:1505027, PubMed:1495974). In undifferentiated cells during the early stages of eye development. Expressed in R7 and cone cells of the eye. Expressed in the embryo. Phosphorylated in response to MAPK signaling. May be phosphorylated by rl. 'Pokkuri' means 'dropping dead' in Japanese. Flies lacking aop result in the differentiation of supernumerary photoreceptors in the eye. Belongs to the ETS family.