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Rhodnius prolixus not only has served as a model organism for the study of insect physiology, but also is a major vector of Chagas disease, an illness that affects approximately seven million people worldwide. We sequenced the genome of R. prolixus, generated assembled sequences covering 95% of the genome (∼ 702 Mb), including 15,456 putative protein-coding genes, and completed comprehensive genomic analyses of this obligate blood-feeding insect. Although immune-deficiency (IMD)-mediated immune responses were observed, R. prolixus putatively lacks key components of the IMD pathway, suggesting a reorganization of the canonical immune signaling network. Although both Toll and IMD effectors controlled intestinal microbiota, neither affected Trypanosoma cruzi, the causal agent of Chagas disease, implying the existence of evasion or tolerance mechanisms. R. prolixus has experienced an extensive loss of selenoprotein genes, with its repertoire reduced to only two proteins, one of which is a selenocysteine-based glutathione peroxidase, the first found in insects. The genome contained actively transcribed, horizontally transferred genes from Wolbachia sp., which showed evidence of codon use evolution toward the insect use pattern. Comparative protein analyses revealed many lineage-specific expansions and putative gene absences in R. prolixus, including tandem expansions of genes related to chemoreception, feeding, and digestion that possibly contributed to the evolution of a blood-feeding lifestyle. The genome assembly and these associated analyses provide critical information on the physiology and evolution of this important vector species and should be instrumental for the development of innovative disease control methods.

Rhodnius prolixus oocyte extracts were chromatographed on an ion exchange column in order to purify vitellin (VT). Three VT heterogeneous populations were identified and named VT(1), VT(2), and VT(3) according to their order of elution from the column. The phosphate content of each population was determined, after lipid extraction, and a heterogeneous distribution was found: VT(1) being the less phosphorylated (50 mol P/mol protein) and VT(3) the heavily phosphorylated population (281 mol P/mol protein). Analysis of radioactivity associated with each VT population purified from animals fed with (32)Pi showed the same phosphorylation profile. Due to the fact that vitellogenin is the known precursor of VT, we have also chromatographed 32P-VG in the same way as we purified VT. Only one VG's population was detected and resembled to VT(3) with respect to its elution profile. All VT populations contain the same neutral lipids, but they were heterogeneous with respect to phospholipid composition. VT(1) presents phosphatidylcholine and phosphatidylethanolamine whereas VT(2) and VT(3) also showed cardiolipin and probably phosphatidylserine. Sugar composition of VT(2) and VT(3) includes mannose as the main associated carbohydrate but VT(1) also contains glucose resembling VG. Although VG and VT are similar with respect to the elution profile, their sugar composition is different. These results suggest a post-endocytosis processing on VG molecule. The possible biological function of VT heterogeneous populations is discussed.

The synthesis and secretion of vitellogenin by the ovary of Rhodnius prolixus was investigated. Using whole ovary or epithelial cells isolated from follicles of different sizes, it is shown that the follicle cells are a site of synthesis for this protein in the ovary. The ovaries or follicle cells were incubated in vitro with [(35)S]-methionine or (32)Pi and the secretion of newly synthesized ovarian vitellogenin (O-Vg) was estimated by the radioactivity associated with the immunoprecipitate or acid-precipitate proteins in the culture medium. The radioactive O-Vg was analyzed by SDS-PAGE followed by autoradiography or after elution from a DEAE-Toyopearl column. The presence of O-Vg inside the follicle cells was detected by immunofluorescence and immunogold labels. Both methods revealed strong labeling inside the follicle cells. While the capacity for total protein synthesis by the follicle cells was maximal during the early phase of vitellogenesis (in small follicles), the synthesis of O-Vg reached its peak during the late phase of oocyte growth, just before formation of the chorion. A possible role for ovarian vitellogenin in Rhodnius and its relationship with Vg synthesis by the fat body is discussed.