Identification of Tick Ixodes ricinus Midgut Genes Differentially Expressed During the Transmission of Borrelia afzelii Spirochetes Using a Transcriptomic Approach

Abstract

Lyme borreliosis is an emerging tick-borne disease caused by spirochetes Borrelia burgdorferi sensu lato. In Europe, Lyme borreliosis is predominantly caused by Borrelia afzelii and transmitted by Ixodes ricinus. Although Borrelia behavior throughout tick development is quite well documented, specific molecular interactions between Borrelia and the tick have not been satisfactorily examined. Here, we present the first transcriptomic study focused on the expression of tick midgut genes regulated by Borrelia. By using massive analysis of cDNA ends (MACE), we searched for tick transcripts expressed differentially in the midgut of unfed, 24h-fed, and fully fed I. ricinus nymphs infected with B. afzelii. In total, we identified 553 upregulated and 530 downregulated tick genes and demonstrated that B. afzelii interacts intensively with the tick. Technical and biological validations confirmed the accuracy of the transcriptome. The expression of five validated tick genes was silenced by RNA interference. Silencing of the uncharacterized protein (GXP_Contig_30818) delayed the infection progress and decreased infection prevalence in the target mice tissues. Silencing of other genes did not significantly affect tick feeding nor the transmission of B. afzelii, suggesting a possible role of these genes rather in Borrelia acquisition or persistence in ticks. Identification of genes and proteins exploited by Borrelia during transmission and establishment in a tick could help the development of novel preventive strategies for Lyme borreliosis.

De novo assembly and annotation of the Amblyomma hebraeum tick midgut transcriptome response to Ehrlichia ruminantium infection

“…Although the midgut transcriptomes of several tick species have been previously described in efforts to identify DEGs involved in blood meal digestion and other physiological processes [ 28 , 31 , 61 , 62 ], transcriptome studies investigating the role of midgut DEGs that act as barriers or gateway to pathogen invasion are scant. In our analysis, we noted a number of genes in the infected midgut which had been previously reported to be involved in host-pathogen interactions and immunity [ 63 , 64 ].…”

“…Advances in high throughput sequencing technologies have accelerated genomic research [ 26 ] and enabled the uncovering of many disease-causing pathogens in ticks [ 27 ]. High throughput transcriptomic sequencing has facilitated the determination of pathogen’s and vector tissues’ gene expression during pathogen acquisition and transmission [ 28 , 29 ]. In-depth analysis of midgut transcriptomes provides an avenue for the identifying and development of potential targets for novel tick control methods.…”

Infection with Borrelia burgdorferi Increases the Replication and Dissemination of Coinfecting Powassan Virus in Ixodes scapularis Ticks

“…Infection of ticks with B. burgdorferi or tick-borne flaviviruses has previously been shown to induce a transcriptional response in both the tick midguts and salivary glands. Infection of ticks with B. burgdorferi or its European analog, B. afzelii, induces alterations to tick metabolism as well as to the tick’s immune and antimicrobial response [ 35 , 36 , 37 ]. Changes have also been observed in the salivary glands in response to spirochete infection [ 38 ] as well as tick-borne flaviviruses [ 39 , 40 ].…”

What do we know about the microbiome of I. ricinus?

“…The segmented midgut is well adapted to accommodate an enormous amount of host blood and fills most of the internal body space. Since digestion in ticks occurs intracellularly, the midgut also functions as a storage organ, enabling continuous digestion of its content over long periods ( Sonenshine and Anderson, 2014 ; Mahmood et al., 2020 ). The hindgut is composed of the intestine, the rectal sac, a large bulbous excretory organ, and the rectum ( Sonenshine and Anderson, 2014 ; Šimo and Park, 2014 ).…”