Drosophila spermatid individualization is sensitive to temperature and fatty acid metabolism

Abstract

Fatty acids are precursors of potent lipid signaling molecules. They are stored in membrane phospholipids and released by phospholipase A2 (PLA2). Lysophospholipid acyltransferases (ATs) oppose PLA2 by re-esterifying fatty acids into phospholipids, in a biochemical pathway known as the Lands Cycle. Drosophila Lands Cycle ATs oys and nes, as well as 7 predicted PLA2 genes, are expressed in the male reproductive tract. Oys and Nes are required for spermatid individualization. Individualization, which occurs after terminal differentiation, invests each spermatid in its own plasma membrane and removes the bulk of the cytoplasmic contents. We developed a quantitative assay to measure individualization defects. We demonstrate that individualization is sensitive to temperature and age but not to diet. Mutation of the cyclooxygenase Pxt, which metabolizes fatty acids to prostaglandins, also leads to individualization defects. In contrast, modulating phospholipid levels by mutation of the phosphatidylcholine lipase Swiss cheese (Sws) or the ethanolamine kinase Easily shocked (Eas) does not perturb individualization, nor does Sws overexpression. Our results suggest that fatty acid derived signals such as prostaglandins, whose abundance is regulated by the Lands Cycle, are important regulators of spermatogenesis.