RNA-Seq analysis of blood meal induced gene-expression changes in Aedes aegypti ovaries

Genomic Analysis of Aedes aegypti in the Northern Chihuahuan Desert of Texas and Mexico

Background: Aedes aegypti, is the primary vector of dengue, Chikungunya, Zika, and yellow fever viruses. Both natural and human-impacted landscapes have selective pressures on Ae. aegypti, resulting in strong genomic structure even within close geographical distances. Materials and Methods: We assess the genetic structure of this medically important mosquito species at the northern leading edge of their distribution in Southwestern USA. Ae. aegypti were collected during 2017 in the urban communities of El Paso and Sparks, Texas (USA) and in the city of Ciudad Juárez, Mexico. Results: Thousands of nuclear loci were sequenced across 260 captured Ae. aegypti. First, we recovered the genetic structure of Ae. aegypti following geography, with all four major collection communities being genetically distinct. Importantly, we found population structure and genetic diversity that suggest rapid expansion through active-short distance dispersals, with Anapra being the likely source for the others. Next, tests of selection recovered eight functional genes across six outliers: calmodulin with olfactory receptor function; the protein superfamily C-type lectin with function in mosquito immune system and development; and TATA box binding protein with function in gene regulation. Conclusion: Despite these populations being documented in the early 2000s, we find that selective pressures on specific genes have already occurred and likely facilitate Ae. aegypti range expansion.

Fertility decline in Aedes aegypti (Diptera: Culicidae) mosquitoes is associated with reduced maternal transcript deposition and does not depend on female age

Female mosquitoes undergo multiple rounds of reproduction known as gonotrophic cycles (GC). A gonotrophic cycle spans the period from blood meal intake to egg laying. Nutrients from vertebrate host blood are necessary for completing egg development. During oogenesis, a female prepackages mRNA into her oocytes, and these maternal transcripts drive the first 2 h of embryonic development prior to zygotic genome activation. In this study, we profiled transcriptional changes in 1-2 h of Aedes aegypti (Diptera: Culicidae) embryos across 2 GC. We found that homeotic genes which are regulators of embryogenesis are downregulated in embryos from the second gonotrophic cycle. Interestingly, embryos produced by Ae. aegypti females progressively reduced their ability to hatch as the number of GC increased. We show that this fertility decline is due to increased reproductive output and not the mosquitoes' age. Moreover, we found a similar decline in fertility and fecundity across 3 GC in Aedes albopictus. Our results are useful for predicting mosquito population dynamics to inform vector control efforts.

Long non-coding RNAs as promising targets for controlling disease vector mosquitoes

Hematophagous female mosquitoes are important vectors of numerous devastating human diseases, posing a major public health threat. Effective prevention and control of mosquito-borne diseases rely considerably on progress in understanding the molecular mechanisms of various life activities, and accordingly, the molecules that regulate the various life activities of mosquitoes are potential targets for implementing future vector control strategies. Many long non-coding RNAs (lncRNAs) have been identified in mosquitoes and significant progress has been made in determining their functions. Here, we present a comprehensive overview of the research advances on mosquito lncRNAs, including their molecular identification, function, and interaction with other non-coding RNAs, as well as their synergistic regulatory roles in mosquito life activities. We also highlight the potential roles of competitive endogenous RNAs in mosquito growth and development, as well as in insecticide resistance and virus-host interactions. Insights into the biological functions and mechanisms of lncRNAs in mosquito life activities, viral replication, pathogenesis, and transmission will contribute to the development of novel drugs and safe vaccines.

Gene coexpression network during ontogeny in the yellow fever mosquito, Aedes aegypti

BACKGROUND

The behaviors and ontogeny of Aedes aegypti are closely related to the spread of diseases caused by dengue (DENV), chikungunya (CHIKV), Zika (ZIKV), and yellow fever (YFV) viruses. During the life cycle, Ae. aegypti undergoes drastic morphological, metabolic, and functional changes triggered by gene regulation and other molecular mechanisms. Some essential regulatory factors that regulate insect ontogeny have been revealed in other species, but their roles are still poorly investigated in the mosquito.

RESULTS

Our study identified 6 gene modules and their intramodular hub genes that were highly associated with the ontogeny of Ae. aegypti in the constructed network. Those modules were found to be enriched in functional roles related to cuticle development, ATP generation, digestion, immunity, pupation control, lectins, and spermatogenesis. Additionally, digestion-related pathways were activated in the larvae and adult females but suppressed in the pupae. The integrated protein‒protein network also identified cilium-related genes. In addition, we verified that the 6 intramodular hub genes encoding proteins such as EcKinase regulating larval molt were only expressed in the larval stage. Quantitative RT‒PCR of the intramodular hub genes gave similar results as the RNA-Seq expression profile, and most hub genes were ontogeny-specifically expressed.

CONCLUSIONS

The constructed gene coexpression network provides a useful resource for network-based data mining to identify candidate genes for functional studies. Ultimately, these findings will be key in identifying potential molecular targets for disease control.

Metal ions in insect reproduction: a crosstalk between reproductive physiology and immunity

Most insects exhibit high reproductive capacity, which demands large amounts of energy, including macronutrients and micronutrients. Interestingly, many proteins involved in oogenesis depend on metals ions, in particular iron (Fe), zinc (Zn), and copper (Cu). Mechanisms by which metal ions influence reproduction have been described in Drosophila melanogaster, but remain poorly understood in hematophagous insects where blood meals include significant ingestion of metal ions. Moreover, there is evidence that some proteins involved in reproduction and immunity could have dual function in both processes. This review highlights the importance of metal ions in the reproduction of non-hematophagous and hematophagous insects. In addition, we discuss how insects optimize physiological processes using proteins involved in crosstalk between reproductive physiology and immunity, which is a double-edge sword in allocating their functions to protect the insect and ensure reproduction.

A transcriptomic atlas of Aedes aegypti reveals detailed functional organization of major body parts and gut regional specializations in sugar-fed and blood-fed adult females

Mosquitoes transmit numerous pathogens, but large gaps remain in our understanding of their physiology. To facilitate explorations of mosquito biology, we have created Aegypti-Atlas (http://aegyptiatlas.buchonlab.com/), an online resource hosting RNAseq profiles of Ae. aegypti body parts (head, thorax, abdomen, gut, Malpighian tubules, ovaries), gut regions (crop, proventriculus, anterior and posterior midgut, hindgut), and a gut time course of blood meal digestion. Using Aegypti-Atlas, we provide insights into regionalization of gut function, blood feeding response, and immune defenses. We find that the anterior and posterior midgut possess digestive specializations which are preserved in the blood-fed state. Blood feeding initiates the sequential induction and repression/depletion of multiple cohorts of peptidases. With respect to defense, immune signaling components, but not recognition or effector molecules, show enrichment in ovaries. Basal expression of antimicrobial peptides is dominated by holotricin and gambicin, which are expressed in carcass and digestive tissues, respectively, in a mutually exclusive manner. In the midgut, gambicin and other effectors are almost exclusively expressed in the anterior regions, while the posterior midgut exhibits hallmarks of immune tolerance. Finally, in a cross-species comparison between Ae. aegypti and Anopheles gambiae midguts, we observe that regional digestive and immune specializations are conserved, indicating that our dataset may be broadly relevant to multiple mosquito species. We demonstrate that the expression of orthologous genes is highly correlated, with the exception of a ‘species signature’ comprising a few highly/disparately expressed genes. With this work, we show the potential of Aegypti-Atlas to unlock a more complete understanding of mosquito biology.