Ferritin Gene Coding Sequences Are Conserved Among Eight Hard Tick Species (Ixodida: Ixodidae)

Eight complete cDNAs encoding for ferritins from the hard tick species Amblyomma americanum (L.), Amblyomma maculatum Koch, Boophilus microplus (Canestrini), Dermacentor albipictus (Packard), Dermacentor variabilis (Say), Hemaphysalis longicornis Neumann, Ixodes scapularis Say, and Rhipicephalus sanguineus (Latreille) were obtained using the techniques of rapid amplification of cDNA ends. The deduced amino acid sequences from these tick ferritin genes share high identities (84–98%) with those of two published tick ferritins. The sequences and positions of the iron-responsive element in the 5′-untranslated region of the cDNAs are highly conserved in ticks. Similar to other known animal ferritins, a ferroxidase center, consisting of seven conserved amino acid residues, was identified in the deduced tick ferritins. Sequence comparison indicates that these tick ferritin genes belong to the type of invertebrate cytosolic heavy chain homologue. Two separate phylogenetic analyses of ferritin amino acid sequences, one with 52 arthropod ferritin sequences and another one using 10 tick ferritins, suggested that ferritin is a suitable nuclear protein-encoding gene for tick phylogenetic reconstruction.