Developmental Stage- and Organ-Specific Expression Profiles of Asparaginyl Endopeptidases/Legumains in the Ixodid Tick Haemaphysalis longicornis

We previously identified two cDNAs from the midgut or adult Haemaphysalis longicornis that encode asparaginyl endopeptidases/legumains, HILgm and HILgm2. Functionally, both recombinant HILgm and HILgm2 efficiently digested blood proteins, haemoglobin and bovine serum albumin. Here, we investigated the expression profiles of legumain genes in the developmental stages in the life cycle of H. longicornis and in different tissues of adult ticks. Both HILgm and HILgm2 were well expressed in larvae, nymphs and adults. Legumain transcripts were expressed specifically in the midgut and were localized in some digestive vacuoles of gut epithelial cells. Furthermore, expression of either transcript was up-regulated by blood feeding in larvae and nymphs, Suggesting the important roles of legumains in blood feeding and blood-meal digestion in ticks.