Comparative analysis of gene expression between Babesia bovis blood stages and kinetes allowed by improved genome annotation.

Authors: Ueti, Massaro; Johnson, Wendell; Kappmeyer, Lowell; Herndon, David; Mousel, Michelle; REIF, KATHRYN - Kansas State University; Taus, Naomi; IFEONU, OLUKEMI - University Of Maryland; SILVA, JOANA - University Of Maryland; Suarez, Carlos; BRAYTON, KELLY - Washington State University

Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/3/2020
Publication Date: 11/23/2020
Citation: Ueti, M.W., Johnson, W.C., Kappmeyer, L.S., Herndon, D.R., Mousel, M.R., Reif, K.E., Taus, N.S., Ifeonu, O.O., Silva, J.C., Suarez, C.E., Brayton, K.A. 2020. Comparative analysis of gene expression between Babesia bovis blood stages and kinetes allowed by improved genome annotation.. International Journal for Parasitology. 51(2-3):123-136. https://doi.org/10.1016/j.ijpara.2020.08.006.
DOI: https://doi.org/10.1016/j.ijpara.2020.08.006

Interpretive Summary: Cattle tick fever, caused by Babesia bovis, poses a significant challenge to livestock production. The vast majority of cattle populations that live in tropical and subtropical regions are at constant risk of Babesia infection via tick transmission. The goal of this study was to understand gene expression by B. bovis during development within the mammalian host and tick vector and identify genes expressed in these stages that could serve as potential vaccine targets for preventing infection/disease or blocking parasite transmission. In this study, we closed a large physical gap in the B. bovis genome sequence. We used the massive transcriptome data to improve the structural annotation of the genome, thus allowing accurate RNA-Seq analysis. Up-regulated genes identified in this study may serve as suitable targets for vaccine development to control bovine babesiosis.

Technical Abstract: Throughout their life cycle, Babesia parasites alternate between a mammalian host, where they cause babesiosis, and the tick vector. Transition between hosts provides an environmental signal that results in altered gene expression and allows the completion of the parasite’s life cycle. A comparison of stages that occur within mammalian and tick hosts can provide insight into the adaptation of Babesia to these different environments. Here, we improved the genome assembly of Babesia bovis, a bovine hemoparasite, closing a 139 kbp gap, and used RNA-Seq datasets derived from mammalian blood and tick kinete stages to greatly improve the genome annotation. Approximately 1/3 of the originally annotated genes required structural changes and 334 new genes were identified, leading to a different predicted proteome compared to the original annotation. Next, the RNA-Seq data was used to identify B. bovis genes that were differentially expressed in the two hosts. In blood stages, 28% of the genes were upregulated up to 300-fold, whereas, 26% of the genes in kinetes were upregulated, reaching >19,000-fold increase. We identified differentially expressed genes that may serve as suitable targets for the development of vaccines to control bovine babesiosis, one of the most economically devastating tick-borne diseases of cattle.