Molecular cloning of two caspase-like genes from the hard tick Haemaphysalis longicornis.

We identified two caspase-like genes from the midgut cDNA library of the hard tick, Haemaphysalis longicornis. Sequence analysis showed that these cDNAs encoded homologues of caspase-2 and caspase-8 that were categorized as apoptosis initiators. The H. longicornis caspase-2 (Hlcaspase-2) cDNA encodes 340 amino acid residues with a predicted molecular weight (Mw) of 38.5 kDa. Another cDNA identified as the H. longicornis caspase-8 (Hlcaspase-8) encodes 306 amino acid residues with an estimated Mw of 35.3 kDa. A catalytic active site was highly conserved in Hlcaspase-8 but not in Hlcaspase-2. RT-PCR analysis showed that both Hlcaspase-2 and Hlcaspase-8 were expressed in tick midgut and salivary glands. This is the first report of the molecular cloning of apoptosis-related genes in the tick.