Mating could be a weakness for Zika mosquitoes

"We are focusing on reproduction because we see it as the Achilles heel of the mosquito," says Laura Harrington. Above: Pupae of Aedes mosquitoes. (Credit: IAEA Imagebank/Flickr)

Scientists are studying the genetic changes that happen after Aedes aegypti mosquitoes mate. They’re looking for information that could be exploited to fight mosquito-borne diseases, such as dengue fever, chikungunya, and Zika virus.

“We are focusing on reproduction because we see it as the Achilles heel of the mosquito,” says Laura Harrington, professor of entomology at Cornell University.

She and colleagues used sequencing to identify changes in RNA populations in the lower reproductive tract of female mosquitoes in response to mating. RNA is the chemical messenger by which the information in genes is translated into protein.

“We have two main goals,” says Harrington, coauthor of a paper published in the PLOS Neglected Tropical Diseases. “The first is to understand the basic biology of the mosquito mating system, and the second is to try to understand it in a way that we can develop novel strategies for controlling the mosquito.”

The research draws from previous findings by molecular biology and genetics professor and study coauthor Mariana Wolfner on how Drosophila females’ gene expression, behavior and physiology are changed by mating. That work revealed that after mating, seminal fluid proteins passed from males to females led to changes in gene expression in females and led females to increase egg production, reduce feeding and decrease their likelihood to mate again.

Hours after mating

In the new study, Harrington and colleagues measured changes in the levels of specific RNAs in the A.aegypti female after mating to determine which proteins became more and less abundant. The findings are a step toward understanding what molecules are necessary to prepare a female for producing progeny.

The research team compared RNAs from reproductive tracts from female mosquitoes that had not mated with those that had—immediately after mating, and six and 24 hours afterward.

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Sixty RNAs were more abundant in females immediately after mating compared with females that hadn’t mated, suggesting that these RNAs had been transferred directly by the male. At six and 24 hours post-mating, 150 transcripts were found in greater abundance, while 130 transcripts were found in lower abundance, in mated females relative to virgins.

The results revealed broad changes in the regulation of genes in the female reproductive tract. These affected genes could influence processes related to blood feeding, egg development, and immune defense.

Smart insecticide

The paper provides a foundation for future studies of female mosquito reproduction, according to the researchers. The data are already being used to improve gene information and expression on VectorBase, a National Institute of Allergy and Infectious Diseases resource center for the scientific community.

The researchers hope to uncover a molecule critical for female fertility; scientists could engineer inhibitors of this molecule, that could then be used to block a female’s ability to produce fertile eggs or that prevent eggs from traveling through the oviduct.

“We can either genetically engineer males not to induce this specific molecule, or we can create a smart insecticide that binds with the molecule and makes it inaccessible to the female,” Harrington says.

Such a “smart insecticide” could target mosquitoes without affecting other insects, Wolfner adds.

Grants from the National Institutes of Health and US Department of Agriculture funded the work.

Source: Cornell University