cDNA cloning and gene characterization of the mitochondrial large subunit (LSU) rRNA from the liver fluke Fasciola hepatica. Evidence of heterogeneity in the fluke mitochondrial genome.

A cDNA clone that encodes the large subunit of mitochondrial ribosomal RNA (LSU rRNA) from the liver fluke F. hepatica was isolated and characterized. This RNA molecule is polyadenylated at the 3' end and represents 10% of the poly A+RNA in adult F. hepatica. Fluke LSU rRNA has significant sequence homology to mosquito mitochondria LSU rRNA and is more closely related to the mitochondrial rRNA of hermaphroditic than dioecious trematodes. Mitochondrial DNA constitutes approximately 10% of the total cellular DNA of adult flukes. This percentage is lower in non-embryonated eggs as are the levels of LSU rRNA indicating eggs have lower metabolic activity. Analysis of transcription and the number of mitochondrial genomes in S. mansoni shows that the LSU rRNA is more abundant in females than in males. Restriction endonuclease analysis of the fluke mitochondrial LSU rRNA genes suggests the presence of heterogeneous repeated copies in the mitochondrial genome or heterogeneity among individual genomes of mitochondria.