De novo transcriptome profiling and characterization of voltage-sensitive sodium channel gene of Tropilaelaps mercedesae parasitizing honey bees

Abstract

Tropilaelaps mercedesae (Acari: Laelapidae) is an ectoparasite of the Western honey bee Apis mellifera and has become a major threat to the apiculture in Asia, including Korea. To establish gene resources of T. mercedesae, the whole transcriptome of mixed developmental stages of mites was analyzed by RNA sequencing. An mRNA-focused library was generated from total RNA extracted from the mixed stages (adults, nymphs and larvae) of T. mercedesae using the TruSeq RNA Library Preparation kit and sequenced using the HiSeq 2000 platform. A total of 59,041,198 reads were obtained with 85% Q30 value. Trimmed sequence data was de novo assembled into 64,868 contigs with an average sequence length of 878bp. Transcriptome annotation to the NCBI non-redundant database resulted in a total of 14,336 Blast hits (22.1%). Functional analysis demonstrated that 11,919 contigs were grouped into 45 Gene Ontology (Conesa et al.) terms, and 1226 contigs were assigned to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Based on the transcriptome dataset, a large number of contigs associated with binding, cellular process and catalytic activity were identified. In order to provide basic information for efficient management of potential resistance to fluvalinate, a pyrethroid acaricide most widely used for the control of T. mercedesae, the gene encoding the voltage-sensitive sodium channel α-subunit (vssc), which is the molecular target of fluvalinate, was annotated and characterized.