Farwa Sajadi

Conference 2023 Presentation

Project title

The roles of ITP and ITP-L in the female mosquito, Aedes aegypti

Authors and Affiliations

Farwa Sajadi1, Jean-Paul Paluzzi1

1. Department of Biology, York University, Toronto, Canada

Abstract

Background

The insect ion transport peptide (ITP) and its alternatively spliced variant, ITP-like (ITP-L) belong to the crustacean hyperglycemic hormone family of peptides and are widely conserved among insect species. While limited, various studies have characterized the ITP/ITP-L signaling systems within many insects, and putative functions including regulation of ion and fluid transport, ovarian maturation, and thirst/excretion have been proposed. However, to date, the expression pattern, tissue distribution, and physiological function of either ITP or ITP-L has not been elucidated in the mosquito, Aedes aegypti. Herein, we aim to molecularly investigate ITP and ITP-L expression profiles in A. aegypti, and examine peptide immunolocalization and distribution within adult tissues.

Methods

To examine a temporal and spatial profile of ITP and ITP-L, mRNA transcript levels were measured using quantitative-PCR. Wholemount immunohistochemistry was used to localize both ITP and ITP-L to the central nervous system of the adult mosquito. Lastly, to investigate a putative role in feeding and starvation, adult mosquitoes were isolated post-emergence and placed into a sucrose-fed, non-fed, or water-fed treatment, and were subsequently collected after 24 or 48h and mRNA transcript levels were measured. Additionally, female mosquitoes were allowed to blood feed, and isolated after 1, 6, 12, or 24 hours post-blood-feeding, and mRNA transcript levels of ITP and ITP-L were measured.

Results

Thus far, transcript expression profiles of both ITP and ITP-L reveal enrichment in males, with ITP exclusively expressed in the brain, and ITP-L expressed predominantly in the abdominal ganglia. Using immunohistochemistry, the central nervous system from adult mosquitoes revealed ITP-like immunostaining in one pair of lateral neurosecretory cells in the posterior region of each brain hemisphere. ITP-L-like immunostaining was observed in one neurosecretory cell located medioposteriorly and ventrally on each abdominal ganglia, with nerve processes migrating anteriorly from the neurosecretory cell and emanating laterally through projections to potential putative neurohaemal sites. Lastly, both starvation and blood-feeding caused upregulation of ITP and ITP-L mRNA in adult mosquitoes, suggesting possible functional roles in ionoregulation.

Conclusions

These findings demonstrate the localization of ITP and ITP-L to the central nervous system of the mosquito with potential roles in bloodfeeding and/or reproduction. Gaining a more comprehensive understanding of these pathways and signalling systems can allow us to further unravel the complex neuropeptidergic regulation in the A. aegypti mosquito.