De novo assembly and analysis of the transcriptome of the Dermacentor marginatus genes differentially expressed after blood-feeding and long-term starvation

Abstract

Background The ixodid tick Dermacentor marginatus is a vector of many pathogens wide spread in Eurasia. Studies of gene sequence on many tick species have greatly increased the information on tick protective antigen which might have the potential to function as effective vaccine candidates or drug targets for eco-friendly acaricide development. In the current study, RNA-seq was applied to identify D. marginatus sequences and analyze differentially expressed unigenes. Methods To obtain a broader picture of gene sequences and changes in expression level, RNA-seq was performed to obtain the whole-body transcriptome data of D. marginatus adult female ticks after engorgement and long-term starvation. Subsequently, the real-time quantitative PCR (RT-qPCR) was applied to validate the RNA-seq data. Results RNA-seq produced 30,251 unigenes, of which 32% were annotated. Gene expression was compared among groups that differed by status as newly molted, starved and engorged female adult ticks. Nearly one third of the unigenes in each group were differentially expressed compared to the other two groups, and the most numerous were genes encoding proteins involved in catalytic and binding activities and apoptosis. Selected up-regulated differentially expressed genes in each group were associated to protein, lipids, carbohydrate and chitin metabolism. Blood-feeding and long-term starvation also caused genes differentially expressed in the defense response and antioxidant response. RT-qPCR results indicated 6 differentially expressed transcripts showed similar trends in expression changes with RNA-seq results confirming that the gene expression profiles in transcriptome data is in consistent with RT-qPCR validation. Conclusions Obtaining the sequence information of D. marginatus and characterizing the expression pattern of the genes involved in blood-feeding and during starvation would be helpful in understanding molecular physiology of D. marginatus and provides data for anti-tick vaccine and drug development for controlling the tick.

Proteomic changes in various organs of Haemaphysalis longicornis under long-term starvation

“…Although the expression of these proteins found in this study has not been clearly reported in the other research about long-term starving ticks, the mRNA expression of some genes (such as 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase) related to carbohydrate metabolism in the long-term starved tick Dermacentor marginatus was significantly increased. Most of these proteins were also involved in glycolysis and other cycle reactions related to energy production, but unfortunately, the tissue-specific expression was not clearly given, so it is impossible to accurately compare them with the significantly up-regulated proteins found in this study [ 26 ].…”

“…In the study of the long-term starved tick D . marginatus , the transcription levels of mRNAs of proteins associated with metabolism and lipid metabolism plus the mRNAs of carbohydrate metabolism related proteins, were also up-regulated [ 26 ]. Hence, this elevated oxidative phosphorylation activity during prolonged starvation enhances substrate oxidation with the corresponding ATP supply and this could be responsible for the ability of most ticks to survive more than a year without blood acquisition.…”

“…We found that the high expression of HSPs found in this study were consistent with the significant increase of transcription levels of almost all mRNAs of HSPs (60, 70, 90, small heat shock protein) found in long-term starving tick D . marginatus [ 26 ]. This strongly corroborates the high expression of HSPs in previous studies during prolonged food deprivation in insects [ 34 – 36 ].…”

“…To further corroborate these findings, a study performed with the tick D . marginatus subjected to long-term starvation exhibited antioxidant response via the up-regulation of mRNA of antioxidant genes including SOD, GST, catalase, and glutathione peroxidase [ 26 ]. When starvation prolongs and exceeds the tolerance threshold of cells, the resultant accumulation of reactive oxygen species (ROS) in the mitochondria leads to extensive autophagy.…”

“…The increased expression of ferritin mRNA in long-term starving tick D . marginatus has been found [ 26 ]. Our results further confirmed this conclusion from the protein level.…”