Female mosquitoes bite us because they need our blood to produce eggs.

During this feeding process, infected mosquitoes can transmit such diseases as Zika, dengue, and yellow fever, making them one of the deadliest creatures on Earth.

Researchers at Virginia Tech have gained insights into the genetics of mosquito reproduction, which could open new avenues of discovery to control the pest and reduce the number of deaths mosquitoes cause every year.   

“Our research elucidates two hormonal pathways that control the developmental stages before and after blood feeding. If we can disrupt these pathways, the mosquitoes stop producing eggs. Our findings provide a foundation to develop biochemical and genetic tools for mosquito population control,” said Jinsong Zhu, a professor of biochemistry in the College of Agriculture and Life Sciences and a Fralin Life Science Institute affiliate.

Zhu’s lab is interested in the genetic mechanisms that control mosquito reproduction and the interaction between mosquito vectors and transmitted pathogens. Their long-term goal is to use genetic engineering and chemical intervention to suppress mosquito populations and impede their ability to transmit the diseases.

The research from Zhu’s lab was published recently in the journal Proceedings of the National Academy of Science.

Two hormones are needed for mosquito egg production: juvenile hormone, or JH, and 20-hydroxyecdysone, or 20E. In Aedes aegypti mosquitoes, four protein isoforms are generated by the taiman gene, which plays an indispensable role in the action of both JH and 20E.

Zhu’s study indicates that different hormone responses require distinct Taiman isoforms. Moreover, JH controls formation of the Taiman isoforms that are specifically required for 20E-regulated gene expression after blood feeding.

Previously, it was only known that mosquitoes needed to be mature enough to take a blood meal, and that JH and 20E controlled the developmental stages before and after blood feeding, respectively. There was no clear explanation of how the whole process was coordinated at a molecular level.

“Now, we know that the taiman gene bridges these two important pathways to ensure a successful orchestration of mosquito egg maturation. Our research found that JH regulates mRNA alternative splicing of many mosquito genes, including the gene for Taiman, which is also a partner of the JH receptor. Among four isoforms of Taiman, two are specifically required by the 20E pathway. If we deplete these two isoforms by disrupting JH-controlled splicing machinery, the mosquitoes completely stop producing eggs," said Pengcheng Liu, a research associate in Zhu’s lab in the Department of Biochemistry.

In the face of the growing pesticide resistance detected in field populations of mosquito vectors, new environmentally safe chemicals are needed to kill mosquitoes at various developmental stages. The research of Zhu’s team will allow researchers to develop new pesticides to directly target these mechanisms that are unique to mosquitoes and reduce mosquito populations.

If the new pesticides are directly targeting these mosquito pathways, it will reduce any adverse effects to beneficial ecosystems and the environment.

Zhu’s team is planning to screen drugs in the Virginia Tech Center for Drug Discovery that target these pathways, and they will collaborate with synthetic chemists to create these new environmentally safe pesticides.