Effect of consuming blood-substitute feed on the transcriptome of the medicinal leech, Hirudo orientalis Utevsky and Trontelj, 2005 (Clitellata: Hirudinida)

While leeches in the genus Hirudo have long been models for neurobiology, the molecular underpinnings of nervous system structure and function in this group remain largely unknown. We sequenced the transcriptome of the primary salivary glands of Hirudo orientalis Utevsky and Trontelj, 2005 using short-read sequencing (Illumina) technology. A de novo-assembled transcriptome revealed 28,485 high-quality contigs with an average size of 598 bp. A total of 10,542 contigs had significant BLASTx or tBLASTx hits (E≤1.0E-6) to known proteins, whereas a high percentage (59.36%) of contigs exhibited no apparent protein or nucleotide hits. Comparison of the Hirudo orientalis salivary gland transcriptome against a published full-body transcriptome assembled from Roche-454 reads revealed several contigs with putative annotations associated with salivary gland functions. KEGG pathway analysis revealed that the majority (15 out of the top 20 predicted KEGG pathways) of the salivary gland contig sequences match proteins involved in metabolism. We identified several genes likely to be involved in detoxification and inhibition of plant defense responses including aldehyde dehydrogenase, metalloprotease, glucose oxidase, glucose dehydrogenase, and regucalcin. We also identified several genes that may play a role in the extra-oral digestion of plant structural tissues including b-glucosidase and pectin lyase, in addition to the extra-oral digestion of sugars, including a-amylase, maltase, sucrase, and a-glucosidase. Our results provide information on the genes related to head formation and insights into the function of proboscis-related genes during organogenesis with the potential roles of genes not yet characterized.