The ion channel ppk301 controls freshwater egg-laying in the mosquito Aedes aegypti.

Benjamin J Matthews,Meg A Younger,Leslie B Vosshall

doi:10.7554/elife.43963

Benjamin J Matthews, Meg A Younger + Show 1 more

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https://doi.org/10.7554/elife.43963

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Abstract

Female Aedes aegypti mosquitoes are deadly vectors of arboviral pathogens and breed in containers of freshwater associated with human habitation. Because high salinity is lethal to offspring, correctly evaluating water purity is a crucial parenting decision. We found that the DEG/ENaC channel ppk301 and sensory neurons expressing ppk301 control egg-laying initiation and choice in Ae. aegypti. Using calcium imaging, we found that ppk301-expressing cells show ppk301-dependent responses to water but, unexpectedly, also respond to salt in a ppk301-independent fashion. This suggests that ppk301 is instructive for egg-laying at low-salt concentrations, but that a ppk301-independent pathway is responsible for inhibiting egg-laying at high-salt concentrations. Water is a key resource for insect survival and understanding how mosquitoes interact with water to control different behaviors is an opportunity to study the evolution of chemosensory systems.

Highlights

Ae. aegypti females must take a blood-meal, typically from a human host, to develop eggs
To investigate freshwater egg-laying preference in the ppk mutants, we introduced single female mosquitoes into individual chambers containing a choice between freshwater (0 mOsm/kg NaCl) or 200 mOsm/kg NaCl
To facilitate our understanding of the neuroanatomy of Ae. aegypti in general, and the projection pattern of the ppk[301] driver line in particular, we built a threedimensional female mosquito brain atlas, in which we identified and named the major neuropils in accordance with nomenclature established by the Insect Brain Name Working Group[23] (Fig. 3h and http://mosquitobrains.org)

Summary

Introduction

Ae. aegypti females must take a blood-meal, typically from a human host, to develop eggs. To investigate freshwater egg-laying preference in the ppk mutants, we introduced single female mosquitoes into individual chambers containing a choice between freshwater (0 mOsm/kg NaCl) or 200 mOsm/kg NaCl. Even when ppk[301] mutant animals laid eggs, they laid fewer eggs than wild-type on water and more eggs than wild-type on 200 mOsm/kg NaCl (Fig. 2d). We noted that projections of ppk301-expressing neurons are present in the male brain and ventral nerve cord (Extended Data Fig. 2b,c), consistent with a role for ppk[301] in behaviours other than egg-laying.

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Conclusion