Study On The Molecular Mechanism Of Salivary Gland Degeneration Of Haemaphysalis Longicornis

Ticks are exclusively hematophagous ectoparasites carrying and spreading pathogens which can bring various diseases to wild animals,livestock and human beings.They are detrimental to not only human health,but also animal husbandry.Ticks can be classified into three taxonomy families,Ixodidae,Argasida and Nuttalliellidae,while Ixodidae is the most fatal and widespread species which is also largest in population.In this study,Haemaphysalis longicornis is classified into Haemaphysalis genus under Ixodidae family.It widely spreads in East Asia and Australia.In China,H.longicornis is also widespread and can damage human health and animal husbandry.The study on H.longicornis shows great social and economic prospect.In order to secure a fast and continuous blood-feeding from the host,a pair of special salivary glands have been evolved in ticks.The specified glands possess a capability to secrete plenty of big or small bloodsucking-supporting molecules with abilities of anticoagulation and immune response resistance against the host.Comparing with males,female ticks are more fatale.Female ticks have a super strong reproducing ability.In order to complete their life circle,females need a huge blood intake from the host and thus spread the pathogens continuously.After engorgement,blood feeding stops and ticks detached spontaneously from their host skin,meanwhile the salivary glands lose their necessity of existence and thus quickly get degenerated.Studying the degeneration of tick salivary glands is important to unravel the function and regulation mechanism of tick salivary glands,as well as limiting their blood feeding and improve the prevention and control methods on tick transmitted diseases.To unravel the molecular mechanisms of tick salivary glands degeneration,quantitative proteomics technology was applied to analyze the dynamic changes of all proteins in female H.longicornis,in order to target the proteins crucial to regulate the salivary glands degeneration and thus theoretically promote the biological prevention and control of ticks.In this study,an iTRAQ proteomic assay was carried out on female H.longicornis salivary glands,differences of proteins expressed at 4 timepoints during the salivary glands degeneration were quantitatively analyzed and 2302 differences in protein expression were detected.Bioinformatics analysis showed that apoptosis signaling pathway and tricarboxylic acid circle play a role in salivary gland degeneration.Several important proteins(F0F1-type ATP synthase,NADH-ubiquinone oxidoreductase,Cytochrome C,Apoptosis inducing factor,Lysosomal acid phosphatase)were screened and further analyzed of their function.Single gene that encodes the above proteins were respectively yield to RNA interfere(RNAi)and their expression consequently dropped in different level.The engorgement weight,the amount of spawning and egg mass conversion ratio of female H.longicornis dropped after RNAi on the four genes of F0F1-type ATP synthase,NADH-ubiquinone oxidoreductase,Cytochrome C,Apoptosis inducing factor.These proteins have a prospect of becoming medical targets in tick prevention and control in future.This study unraveled the molecular mechanism of H.longicornis salivary gland degeneration and provided theoretical support to tick prevention and control.