The apicoplast genome of Leucocytozoon caulleryi, a pathogenic apicomplexan parasite of the chicken

Leucocytozoon caulleryi, a haemosporidian parasite of the chicken (Gallus gallus domesticus), can be highly pathogenic and often fatal. Although this parasite is extremely relevant to veterinary science, knowledge of its genomic features is limited. To gain information applicable to developing novel control methods for the parasite, we analyzed the apicoplast genome of L. caulleryi. This extranuclear organellar DNA of 85.1 % A + T and a unit of 34,779 bp was found to encode almost the same set of genes as the plastid genome of Plasmodium falciparum, including 16 tRNA and 30 protein coding genes, and except for one open reading frame, ORF91 absent in L. caulleryi. As in P. falciparum, the L. caulleryi apicoplast DNA contains two sets of a unique inverted repeat (IR), each one 5,253 bp and encoding genes specifying one large and one small rRNA subunit and nine tRNAs but no protein, and separated by a unique 13 bp sequence. Studies of several haemosporidian apicoplast DNA sequences have identified a corresponding IR region; however, none of these studies has looked at the complete sequence, even for well-studied species such as P. falciparum. Phylogenetic studies using a concatenated amino acid sequence based on the open reading frames confirmed the close relationship between L. caulleryi and Plasmodium spp. In this study, we determined the nucleotide sequence of the entire L. caulleryi apicoplast genome, including the region connecting the two IR units. This is the first report of the complete nucleotide sequence of a haemosporidian apicoplast DNA with a canonical IR.