DUTTA, SHRABONITicks are prevalent throughout the world and are capable of transmitting a variety of pathogens (e.g., bacteria, protozoa, and viruses) to humans. Incidence rates for tick-borne diseases (TBD) are also increasing globally, and effective vaccinations to combat tick infestations and TBD transmission remain a critical unmet need. Of the six major tick genera that spread human illnesses worldwide, Ixodes ticks are the most prevalent. Specifically, Ixodes scapularis (also known as the blacklegged or deer tick) is an obligate blood-feeding arthropod that transmits several human and animal pathogens that include Borrelia burgdorferi sensu lato complex – the causative agent for Lyme disease. Unlike many hematophagous insects and soft ticks, I. scapularis (hard ticks) remain attached to their hosts for several days and are capable of uptaking bloodmeals that are 100 times greater than their initial body weight. A large and nutrient-dense bloodmeal is essential for their sub-adult and adult development processes and fecundity. However, the molecular and cellular processes that regulate tick blood feeding (hematophagy) and development have not been extensively elucidated. Therefore, our major objective is to characterize tick molecular components that are critical in the tick parasitism and life cycle in order to develop new strategies to combat tick infestations and spread of tick-borne diseases. Herein, we describe the structural and functional properties of a newly identified I. scapularis protein isolated from the partially fed nymphal ticks. Although the protein displays minor homology to proteins of known functions, structurally, it resembles some features of arthropod Odorant Binding Proteins (OBP). Therefore, we refer to this protein as, Ixodes Gut OBP (IGOBP). We show that the knockdown of IGOBP via RNA interference in ticks results in impaired blood feeding (hematophagy) and significantly decreases their post-fed weights. In addition, systemic IGOBP knockdown gives rise to aberrant phenotypes, significantly reduces tick molting rate, and compromises the structural integrity of the cuticle, specifically the flexible alloscutum components. Notably, IGOBP knockdown has profound effects on the molting efficacy and fitness of females than males. This is likely due to the fact that female adults consume a greater volume of bloodmeal than male adults, necessitating a more pronounced expansion of the alloscutum. Subsequently, our RNA sequencing data identifies multiple genes whose expressions are regulated by IGOBP. The underlying mechanism of possible IGOBP or associated gene functions may aid in identifying future targets for anti-tick vaccines. In summary, our studies characterized a novel I. scapularis protein revealing that the protein is essential for tick hematophagy and development. To the best of our knowledge, this is the first characterization of a tick odorant-binding protein (OBP), using structural and functional genomic tools that unearthed the unique and possibly multifunctional role of IGOBP in vector biology and parasitism. We anticipate that the presented data will enhance our fundamental understanding of tick biology and contribute to the development of potential anti-tick measures.enDissertationBiologyCellular biologyMolecular biologyTick biologyVector Biology