The Drosophila apical photoreceptor membrane is defined by the presence of two distinct morphological regions, the microvilli-based rhabdomere and the stalk membrane. The subdivision of the apical membrane contributes to the geometrical positioning and the stereotypical morphology of the rhabdomeres in compound eyes with open rhabdoms and neural superposition. Here we describe the characterization of the photoreceptor specific protein PIP82. We found that PIP82’s subcellular localization demarcates the rhabdomeric portion of the apical membrane. We further demonstrate that PIP82 is a phosphorylation target of aPKC. PIP82 localization is modulated by phosphorylation, and in vivo, the loss of the aPKC/Crumbs complex results in an expansion of the PIP82 localization domain. The absence of PIP82 in photoreceptors leads to misshapped rhabdomeres as a result of misdirected cellular trafficking of rhabdomere proteins. Comparative analyses reveal that PIP82 originated de novo in the lineage leading to brachyceran Diptera, which is also characterized by the transition from fused to open rhabdoms. Taken together, these findings define a novel factor that delineates and maintains a specific apical membrane domain, and offers new insights into the functional organization and evolutionary history of the Drosophila retina.

在果蝇心尖感光体的膜是由两个不同的形态的区域，所述基于微绒毛-rhabdomere和秆膜的存在限定。根尖膜的细分有助于在张开的横纹和神经重叠的复眼中横纹的几何定位和定型形态。在这里，我们描述了感光蛋白PIP82的表征。我们发现PIP82的亚细胞定位划定了根尖膜的横纹肌部分。我们进一步证明，PIP82是aPKC的磷酸化目标。PIP82的定位受磷酸化的调节，并且在体内，aPKC / Crumbs复合体的丢失导致PIP82定位域的扩展。由于横纹肌蛋白的错误细胞运输，光感受器中缺乏PIP82会导致横纹肌错配。对比分析显示，PIP82从头起源于导致短臂双翅目的谱系，其特征还在于从融合横纹到开放横纹。综上所述，这些发现定义了一个新的因子，该因子描绘并维持了特定的根尖膜结构域，并为果蝇视网膜的功能组织和进化史提供了新的见解。