What happens after a blood meal? A transcriptome analysis of the main tissues involved in egg production in Rhodnius prolixus, an insect vector of Chagas disease

Abstract

The blood-sucking hemipteran Rhodnius prolixus is a vector of Chagas disease, one of the most neglected tropical diseases affecting several million people, mostly in Latin America. The blood meal is an event with a high epidemiological impact since adult mated females feed several times, with each meal resulting in a bout of egg laying, and thereby the production of hundreds of offspring. By means of RNA-Sequencing (RNA-Seq) we have examined how a blood meal influences mRNA expression in the central nervous system (CNS), fat body and ovaries in order to promote egg production, focusing on tissue-specific responses under controlled nutritional conditions. We illustrate the cross talk between reproduction and a) lipids, proteins and trehalose metabolism, b) neuropeptide and neurohormonal signaling, and c) the immune system. Overall, our molecular evaluation confirms and supports previous studies and provides an invaluable molecular resource for future investigations on different tissues involved in successful reproductive events. These analyses serve as a starting point for new investigations, increasing the chances of developing novel strategies for vector population control by translational research, with less impact on the environment and more specificity for a particular organism.

Regulation of a Trehalose-Specific Facilitated Transporter (TRET) by Insulin and Adipokinetic Hormone in Rhodnius prolixus, a Vector of Chagas Disease

“…Standardized conditions of insect rearing were previously described ( Leyria et al, 2020a ). It is important to note that under our standardized conditions, female insects can only lay eggs after a blood meal ( Leyria et al, 2020a , b ). Thus, some experiments required females to take a blood meal in order to promote egg growth.…”

“…In addition, using VectorBase and orthoMCL DB ( Li et al, 2003 ), potential orthologs were identified. RNA-seq data, available from the National Center for Biotechnology Information (NCBI) database (accession numbers PRJNA624187 and PRJNA624904 BioProjects) ( Leyria et al, 2020a , b ), was used to analyze the transcript expression of putative orthologs in the fat body and ovaries of unfed and fed R. prolixus females. Maxima structural model was built based on crystallographic data from proteins with similar secondary structure arrangements, using Phyre2 server ( Kelley et al, 2015 ).…”

“…The spatial distribution of the Rhopr-TRET transcript in different tissues (CNS, ovaries, oviducts, fat body, foregut, anterior midgut, posterior midgut, salivary glands, accessory reproductive glands, hemocytes, hindgut, Malpighian tubules and dorsal vessel) was evaluated during the unfed condition (baseline stage). Tissue dissection was performed as previously reported ( Leyria et al, 2020a , b ). Briefly, the tissues were dissected from females during different time points of unfed and fed states, in cold autoclaved PBS.…”

“…The presence of the AKH receptor ( AKHR ) transcript and ILP/IGF signaling activation in ovaries of R. prolixus has been reported ( Zandawala et al, 2015 ; Alves-Bezerra et al, 2016 ; Leyria et al, 2020a ), suggesting that both peptide hormones may also have a role in controlling aspects of reproductive physiology in ovaries. In addition, a transcriptome analysis of ovaries from fed females of R. prolixus suggests that the trehalose which is taken up by that tissue comes from extra-ovarian sources ( Leyria et al, 2020b ). Although in the ovaries of R. prolixus females, the percentage of carbohydrates stored during vitellogenesis is lower (around 6–10%) compared to those found for other nutrients, such as lipids and proteins ( Santos et al, 2008 , 2012 ; Leyria et al, 2020b ), the use of glycogen has been related to successful embryonic development, revealing the importance of carbohydrate accumulation by oocytes.…”

“…In addition, a transcriptome analysis of ovaries from fed females of R. prolixus suggests that the trehalose which is taken up by that tissue comes from extra-ovarian sources ( Leyria et al, 2020b ). Although in the ovaries of R. prolixus females, the percentage of carbohydrates stored during vitellogenesis is lower (around 6–10%) compared to those found for other nutrients, such as lipids and proteins ( Santos et al, 2008 , 2012 ; Leyria et al, 2020b ), the use of glycogen has been related to successful embryonic development, revealing the importance of carbohydrate accumulation by oocytes. Here, we present results supporting the hypothesis that a direct trehalose uptake through the R. prolixus TRET (Rhopr-TRET), regulated by insulin and/or AKH-signaling, is important for the storage of carbohydrates by the ovaries.…”