IMMUNOGOLD COLOCALIZATION OF OPSIN AND ACTIN IN DROSOPHILA PHOTORECEPTORS THAT UNDERGO ACTIVE RHABDOMERE MORPHOGENESIS

This paper describes the localization of visual pigment opsin and its association with actin in the photoreceptors of newly emerged (within 12 hr after emergence) Drosophila melanogaster. The photoreceptor of n ewly emerged flies was characterized by the rich content of rough-surf aced endoplasmic reticulum (rER) and the small rhabdomere: the photore ceptor is actively constructing rhabdomere, and therefore suitable to study the mechanism of rhabdomere morphogenesis. The photoreceptor spe cifically contained opsin-bearing structures some of which were enclos ed by several layers of membranes. The structure became sparse in 10 d old flies. Opsins in the structure may be incorporated into the new r habdomere. The antiopsin also labeled the plasma membrane facing to th e intraommatidial space and the endomembranes in the cell body. Both r egions were furnished by uniformly oriented actin filaments with the p lus ends towards the rhabdomere. Such orientation makes the actin fila ments possible to be involved in the vectorial transport of materials towards the rhabdomere by a presumptive interaction with the myosin-li ke ninaC proteins identified in Drosophila photoreceptors.