Fig. 1. eyc is required for normal Drosophila photoreceptor morphogenesis. (A) In wild-type eyes, the closely packed photosensitive microvilli of the rhabdomere (r) appear as dark circular ovals arranged in a trapezoid. Rhabdomeres are positioned in the inter-rhabdomeral space (IRS) by a surrounding membrane domain, the stalk (s). Together, the rhabdomere and stalk constitute the photoreceptor apical plasma membrane. (B) In eyc¹ eyes, abnormal apical membrane contacts, including rhabdomere-rhabdomere and rhabdomere-stalk contacts, disrupt the rhabdomere trapezoid and partition the IRS into irregular chambers. (C) eyc^P and (D) eyc^P in trans with Df(2R)Px2 show similar disturbances of rhabdomere topology. (E,F) In 37% p.d. wild-type (E) and eyc¹ (F) ommatidia, irregularly infolded photoreceptor apical surfaces, which are bounded by zonula adherens (z.a.) junctions, face each other in a trapped apical cavity. (G) By 55% p.d., wild-type photoreceptor apical surfaces have differentiated well-ordered stalk and rhabdomere subdomains. Face to face contacts have been released and the IRS has opened. Processes of the four cone cells (ccp) appear as small circular profiles ‘behind’ z.a. junctions between photoreceptors. (H) In 55% p.d. eyc¹ ommatidia, distinct rhabdomere and stalk membrane can be recognized, but these are irregularly ordered. Face to face apical contacts have not released and the IRS is fragmented into small chambers. Loops of stalk membrane (arrows) are trapped by abnormal adhesions. Scale bar: 2 µm. Anterior is towards the right.

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