Date of Award
Honors College Thesis
Tick salivary glands serves as the organ of osmoregulation in ticks and are critical to the biological success of ticks both during extended period off the host and also during the feeding periods on the host. The salivary glands are the sites of pathogen development and saliva is the route of transmission. The importance of multifunctional salivary glands to tick survival and vector competency makes the glands a potential target for intervention. The complex process by which tick salivary gland proteins exit the glands and enter the host has been extensively studied, in what is called the SNARE hypothesis, soluble N-ethylmaleimide-sensitive factor attachment proteins (SNAPs) and their receptor proteins (SNAREs) interact to move vesicles rich in tick salivary gland proteins out of the salivary gland cells. In this study, we tested the hypothesis that VTI family of SNARE proteins, VTI1A and VTI1B, are required for the salivary vesicle transport and success of tick to gain an uninterrupted access to blood-meal for several days. Consistent with previous studies, AmVti1A and AmVti1B possess 28% amino acid identity, but much higher amino acid identity to other homologs. These two proteins appear to play different roles in vesicular trafficking and exhibit distinct localization. Transcriptional gene expression using RT-qPCR revealed elevated expression of Vti1A and Vti1B during the early phase of feeding. Knockdown analysis was performed by injecting adult female A. maculatum ticks with dsRNA for AmVti1A, AmVti1B or both genes to further elucidate their function. Whereas Vti1A knockdown ticks did not seem to produce a significant phenotype, Vti1B knockdown ticks produced significantly lower engorgement weights than those of Vti1A knockdown ticks and those treated with a mock control. Previous research suggests that Vti1B, or other identified SNARE partners, may be able to partially compensate for the loss of Vti1A. Our results demonstrate an important role of VTI protein family in uninterrupted prolonged tick feeding on the host. Understanding the basic mechanisms of VTI protein family in salivary glands may lead to better ways to prevent tick and tick-borne diseases.
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Villarreal, Ashley, "Molecular and Functional Characterization of Tick Salivary VTI Protein Family" (2012). Honors Theses. 68.