Cardiolipin hydrolase present at the mitochondrial outer membrane required for piRNA metabolic process. Acts by catalyzing the hydrolysis of cardiolipin (diphosphatidylglycerol) to form phosphatidate (phosphatidic acid or PA) at the mitochondrial outer membrane surface, promoting the piRNA metabolic process. Plays a key role in primary biogenesis of piRNAs and is required during oogenesis to repress transposable elements and prevent their mobilization. piRNAs mediate the repression of transposable elements during meiosis by forming complexes composed of piRNAs and Piwi proteins and govern the methylation and subsequent repression of transposons. Involved in trans-silencing effect (TSE), a homology-dependent repression mechanism by which a P-transgene inserted in subtelomeric heterochromatin via its role in piRNA biogenesis. Homodimer (By similarity). Interacts with miga/CG12125 (PubMed:26711011). Was initially reported to localize to the meiotic nuage, also named P granule (PubMed:17543859). However, it was later shown that the EGFP tag at N-terminus used in initial experiments interfered with mitochondrial localization (PubMed:21397848 and PubMed:20966047). In contrast to other members of the phospholipase D family, contains only one PLD phosphodiesterase domain, suggesting that it has a single half-catalytic and requires homodimerization to form a complete active site. Defects in mid oogenesis. Females are viable but produce eggs with a range of dorso-ventral patterning defects. Flies lay few eggs, all of which are completely ventralized and often collapsed. Effects are due to defects in piRNA biogenesis and derepression of retrotransposons. Defects are not only present in germ cells but also in somatic cells of the ovary. Belongs to the phospholipase D family. MitoPLD/Zucchini subfamily.