FIGURE 9.

Model of a potential regulatory pathway involved in Rhopr-TRET transcript expression in the fat body and ovaries of females of Rhodnius prolixus during unfed and fed stages. In R. prolixus, after a blood meal, we propose that insulin signaling is activated in ovaries and fat body and, along with other regulatory mechanisms, triggers vitellogenesis (Leyria et al., 2020a). Here, we demonstrate that trehalose content increases in the fat body and ovaries as days post-blood meal progress, as do the circulating levels in the hemolymph. We suggest that insulin-signaling activation, via Rhopr-IR1 (InR), is involved in Rhopr-TRET transcript expression that could then result in mediating a TRET facilitated bidirectional transfer of trehalose; the release of trehalose from the fat body and the uptake by the ovaries, satisfying the physiological needs required for egg formation. The potential up-regulation of Rhopr-TRET transcript via Rhopr-AKH signaling during vitellogenesis is also suggested, as well as a positive feedback of hemolymph trehalose levels on insulin signaling. In the unfed condition, Rhopr-AKH signaling might be involved in the release of trehalose from ovaries via Rhopr-TRET, thereby providing a source of energy for the insect during stressful situations such as starvation. The role of AKH signaling in promoting the glycolysis in unfed conditions to generate glucose as an energy source and/or trehalose to carbohydrate mobilization, as well as the release of Rhopr-ILP1/Rhopr-IGF and Rhopr-AKH after feeding, are assumed (gray dashed arrows). Rhopr-AKHR (AKHR).