Evolution and structural organisation of mitochondrial DNA control region of myiasis-causing flies

This study reports the molecular characterization of the mtDNA control regi on (called the A + T-rich region in insects) of five dipteran species which cause myiasis: Cochliomyia hominivorax Coquerel, Cochliomyia macellaria Fa bricius, Chrysomya megacephala Fabricius, Lucilia eximia Wiedemann (Diptera : Calliphoridae) and Dermatobia hominis Linnaeus Jr (Diptera: Oestridae). T he control region in these species varies in length from 1000 to 1600 bp. T wo structural domains with specific evolutionary patterns were identified. These were (1) conserved sequence blocks containing primary sequence motifs , including dinucleotide pyrimidine-purine series and long T-stretches, loc ated at the 5' end adjacent to the tRNA(Ile) gene and (2) a hypervariable d omain at the 3' end characterized by increased nucleotide divergence and si ze variation. A high frequency of A <----> T transversions at nucleotide su bstitution level indicated directional mutation pressure. The phylogenetic usefulness of the insect control region is discussed.