IMMUNOLOCALIZATION OF DROSOPHILA EYE-SPECIFIC DIACYLGYLCEROL KINASE, RDGA, WHICH IS ESSENTIAL FOR THE MAINTENANCE OF THE PHOTORECEPTOR

The Drosophila retinal degeneration A (rdgA) mutant has photoreceptor cells that degenerate within a week after eclosion. The degeneration s tarts with the disruption of the subrhabdomeric cisternae (SRC), which are the organelles essential for the transport of phospholipids to th e photoreceptive membranes. Our previous biochemical and molecular stu dies suggested that the rdgA gene encodes an eye-specific diacylglycer ol kinase (DGR). In this study, we show that retinal degeneration is p revented by the introduction of the eye-DGK gene in the rdgA mutant ge nome, suggesting that the DGK activity is crucial for the maintenance of the photoreceptor. Furthermore, by immunohistochemical analysis, we have demonstrated that the rdgA protein is predominantly associated w ith the SRC, suggesting that the conversion from diacylglycerol (DG) t o phosphatidic acid (PA) most actively occurs in SRC. The analysis of the eyes of mutants homozygous for rdgA and eye-protein kinase C mutat ions indicates that retinal degeneration is caused by the deficiency o f PA rather than excessive accumulation of DG. From these data, we con clude that the production of PA in the SRC membranes is essential for the maintenance of the photoreceptor. (C) 1997 John Wiley & Sons, Inc.