Expression of sec6^{Scer\UAS.P\T.cBa} under the control of Scer\GAL4^ey.PH results in no detectable morphological defects.

Eyes that are mutant for sec6²⁰ (made by inducing sec6²⁰ mutant clones and genetically ablating wild type sister clones) and which also express sec6^{Scer\UAS.P\T.cBa} under the control of Scer\GAL4^ey.PH are referred to as 'sec6(pr)' (for 'partial rescue') eyes. sec6(pr) mutant eyes develop to near normal size in the adult but are slightly rough and interommatidial bristles are virtually absent. Defects in the differentiation of the cornea and the pigment cells are apparent that are more severe in the anterior half of the eye. At 55% pupal development, gross morphological defects are not apparent in sec6(pr) mutant photoreceptors, although there are some defects in the organization of microvilli and a conspicuous increase in cytoplasmic vesicles compared to wild type. At 90% pupal development, sec6(pr) mutant photoreceptors appear swollen and have smaller and flattened rhabdomeres compared to wild type, and their cytoplasm is filled with vesicles of 100-300 nm diameter that are only rarely seen in wild type; the proximal-distal length of sec6(pr) rhabdomeres is significantly reduced compared to wild type, and the sec6(pr) retina as a whole reaches only approximately half the depth of a wild type retina; some sec6(pr) photoreceptor cells also have an enlarged endoplasmic reticulum. In one-day-old adult flies, the photoreceptors and other retinal cells of sec6(pr) eyes show widespread signs of degeneration; the rhabdomeres of photoreceptors are either strongly reduced in size or are missing.