Functional characterization of maternally accumulated hydrolases in the mature oocytes of the vector Rhodnius prolixus reveals a new protein phosphatase essential for the activation of the yolk mobilization and embryo development

Functional characterization of vitellogenin unveils novel roles in RHBP uptake and lifespan regulation in the insect vector Rhodnius prolixus

In insects, vitellogenesis plays a critical role in providing the energy reserves needed for embryonic development as it ensures the accumulation of yolk in the oocytes. Vitellogenin (Vg), the precursor to vitellin (Vt), is primarily synthesized in the fat body of females and transported to the oocytes via receptor-mediated endocytosis. In Rhodnius prolixus, a key vector of Chagas disease, two Vg genes, Vg1 and Vg2, were characterized. These genes share 65 % amino acid identity and present the conserved Vitellogenin_N, DUF1943, and VWD domains typical of Vg proteins across various species. We found that Vg1 is expressed at significantly higher levels than Vg2 in adult females. Still, the expression of both isoforms was also detected in organs such as the flight muscle, midgut, and ovary, as well as in males and nymphs. RNAi-mediated knockdown of Vg1 and Vg2 in adult females resulted in the production of yolk-depleted eggs with drastically reduced levels of Vg and RHBP, the second most import yolk protein in this species. Despite regular oviposition rates, most of these eggs were inviable, highlighting the essential role of Vg and RHBP in embryo development. Although Vg expression was detected in adult males, the mating of Vg-knockdown males with wild-type females did not impact oviposition or egg viability, indicating that male Vg is not crucial for oogenesis in this species. Interestingly, Vg knockdown increased lifespan for both males and females, suggesting additional physiological functions beyond reproduction. These findings reveal the importance of Vg in oogenesis and embryonic development in R. prolixus while also suggesting potential non-reproductive roles of Vg in adult insect physiology.

Refining the annotation of Rhodnius prolixus aspartic proteases A1 family genes through proteogenomics

Rhodnius prolixus Stål (Hemiptera: Reduviidae: Triatominae) a hematophagous model organism and vector of Chagas disease, relies on a complex repertoire of digestive enzymes to process its blood meals. Among these, aspartic proteases from the A1 peptidase family play a crucial role in nutrient breakdown. This study aims to refine the gene annotation of the A1 peptidase family in this organism through proteogenomics. A comprehensive analysis of aspartic protease gene sequences and protein isoforms, identified by proteomics, revealed discrepancies in existing gene annotations, including the identification of novel open reading frames and the consolidation of previously separated gene sequences. Our efforts led to the correction of seven gene annotations, reducing the total count of A1 peptidase genes from 19 to 15. Notably, 11 of these genes were confirmed at the protein level, while two were supported by transcriptomic data. Furthermore, our findings highlight instances of alternative splicing, as seen in RPRC015076, where proteoforms T1IFK7 and R4G5J6 are expressed through intron retention. This study not only provides a more accurate and comprehensive genomic framework for the A1 peptidase family but also offers new insights into the functional complexity and regulation of digestive enzymes in R. prolixus. These findings pave the way for future studies on insect digestive biology and their potential applications in vector control strategies.

Maternal lipid mobilization is essential for embryonic development in the malaria vector Anopheles gambiae

Lipid metabolism is an essential component in reproductive physiology. While lipid mobilization has been implicated in the growth of Plasmodium falciparum malaria parasites in their Anopheles vectors, the role of this process in the reproductive biology of these mosquitoes remains elusive. Here, we show that impairing lipolysis in Anopheles gambiae, the major malaria vector, leads to embryonic lethality. Embryos derived from females in which we silenced the triglyceride lipase AgTL2 or the lipid storage droplet AgLSD1 develop normally during early embryogenesis but fail to hatch due to severely impaired metabolism. Embryonic lethality is efficiently recapitulated by exposing adult females to broad-spectrum lipase inhibitors prior to blood feeding, unveiling lipolysis as a potential target for inducing mosquito sterility. Our findings provide mechanistic insights into the importance of maternal lipid mobilization in embryonic health that may inform studies on human reproduction.

Pre-Embryonic Period Observation Shows a Unique Reproductive Strategy of the Critically Endangered Anji Salamander (Hynobius amjiensis)

Hynobius amjiensis, also known as the Anji salamander, is an amphibian species currently categorized as endangered due to its limited geographical distribution, primarily in China. To address the critical conservation status of this species, artificial breeding is essential for population expansion. However, progress in artificial breeding efforts has been hindered by the scarcity of research on the reproductive biology of the Anji salamander. In this study, we identified 25 distinct early stages of embryo development. Additionally, we observed that Anji salamander embryos contain a lesser amount of yolk compared to other salamanders or frogs. We further discovered that the Anji salamander employs a highly competitive reproductive strategy, producing a smaller number of high-quality offspring. This strategy aims to generate adaptive individuals through intense intraspecific competition, driven by three factors: extremely confined breeding habitats, a substantial number of eggs, and a reduced yolk content. We introduce the term "mass escape" to describe this strategy, which provides a novel perspective on cannibalization, focusing on the consumption of specific body parts rather than a single-individual activity. This study offers valuable insights into artificial breeding techniques designed to mitigate inherent intraspecific competitive pressure, thereby improving metamorphosis and survival rates. Additionally, it provides a comprehensive table detailing the pre-embryonic developmental stages of the Anji salamander.