Illustration of mosquito hormone regulation of digestive enzymes.

Mosquitoes' Secret Weapon: How Juvenile Hormones Control Blood-Digesting Enzymes

Rhea Morgan in Science & Nature September 2025 • 4 min read.

"Unraveling the Connection Between Hormones and Trypsin Production in Mosquitoes Could Lead to Novel Pest Control Strategies"

Mosquitoes are more than just a summertime nuisance; they are vectors of serious human diseases like malaria, dengue, and yellow fever. Female mosquitoes require a blood meal to produce eggs, and this process depends on their ability to digest blood efficiently. Enzymes called trypsin and chymotrypsin are key players in this blood-digestion process, breaking down proteins into amino acids that are then used to create eggs.

For decades, scientists have been studying the intricate processes that govern trypsin production in mosquitoes. Early research identified two distinct phases of trypsin production: an initial phase that relies on existing trypsin transcripts and a later phase that involves the creation of new transcripts. Researchers have also discovered that factors like blood meals, sugar intake, and hormones can influence trypsin production.

Now, a groundbreaking study sheds new light on the role of juvenile hormones (JH) in regulating the production of trypsin. The research, published in Archives of Insect Biochemistry and Physiology, reveals that JH not only influences the amount of trypsin produced but also controls the splicing of the messenger RNA (mRNA) that carries the instructions for making trypsin. This discovery opens new avenues for developing targeted mosquito control strategies.

The Discovery: JH's Role in Splicing Early Trypsin mRNA

Illustration of mosquito hormone regulation of digestive enzymes.

The research team, led by Dov Borovsky, Robert G. Hancock, Pierre Rougé, Charles A. Powell, and Robert G. Shatters Jr., focused on Culex quinquefasciatus, a common mosquito species. They discovered that juvenile hormone III (JH III), a key hormone in insect development and reproduction, plays a critical role in the splicing of early trypsin mRNA.

mRNA splicing is a crucial step in gene expression. Genes contain both coding regions (exons) and non-coding regions (introns). Before a gene can be used to make a protein, the introns must be removed, and the exons must be joined together. This process is called splicing.

Here's what the study revealed:

In the absence of JH III, the early trypsin mRNA remains unspliced.
This unspliced transcript is linked to RNA ribonucleoproteins (RNPs).
When JH III levels are high (typically after a sugar meal), the pre-mRNA transcript converts into a spliced transcript.
This splicing process is essential for producing functional trypsin.

These findings suggest that JH III acts as a switch, controlling whether the early trypsin mRNA is spliced and ready to be translated into the trypsin enzyme. When JH III levels are low, the mRNA remains in an inactive, unspliced state. When JH III levels rise, the mRNA is spliced, allowing trypsin production to proceed.

New Avenues for Mosquito Control

These findings open exciting new possibilities for mosquito control. By understanding how JH III regulates trypsin production, scientists can explore strategies to disrupt this process and prevent mosquitoes from digesting blood. This could lead to the development of novel insecticides or other control methods that specifically target the hormonal regulation of trypsin production. Further research is needed to fully understand the intricacies of JH III signaling and its impact on mosquito physiology, but this study provides a significant step forward in the fight against mosquito-borne diseases.

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Everything You Need To Know

What are juvenile hormones, and why are they important in mosquitoes?

Juvenile hormones (JH) are a group of hormones crucial for insect development and reproduction. In mosquitoes, they play a vital role in regulating the production of trypsin, an enzyme essential for digesting blood. This is significant because female mosquitoes need blood to produce eggs, and trypsin facilitates the breakdown of blood proteins into amino acids used for egg production. The implications are that by understanding how juvenile hormones control trypsin, scientists can develop strategies to disrupt this process and potentially control mosquito populations. Other hormones and hormone related processes in insects such as ecdysone and neuropeptide signaling could also be crucial targets for pest control.

What is trypsin, and why is it so important for mosquitoes?

Trypsin is an enzyme that is essential for blood digestion in mosquitoes. It works by breaking down proteins in the blood into amino acids. These amino acids are then used by the female mosquito to produce eggs. Trypsin's role is crucial because without it, female mosquitoes cannot efficiently digest blood and therefore cannot reproduce effectively. This makes it a key target for potential mosquito control strategies. The role of other enzymes like chymotrypsin is also vital in blood digestion.

What is mRNA splicing, and why is it important?

mRNA splicing is a critical step in gene expression. Genes contain coding regions (exons) and non-coding regions (introns). Before a gene can be used to make a protein, the introns must be removed, and the exons must be joined together. This process ensures that the correct protein is produced. In the context of trypsin production in mosquitoes, mRNA splicing is regulated by juvenile hormones, affecting how much functional trypsin is produced. If splicing is disrupted, non-functional proteins or reduced amounts of critical proteins will be produced. This process is also important in many other biological functions beyond mosquito physiology.

What did the study discover about the relationship between juvenile hormone III and trypsin production in mosquitoes?

The study found that Juvenile Hormone III (JH III) acts as a switch in the production of trypsin in *Culex quinquefasciatus* mosquitoes. When levels of JH III are low, the early trypsin mRNA remains unspliced and inactive. When JH III levels increase (typically after a sugar meal), the pre-mRNA transcript converts into a spliced transcript, allowing trypsin production to proceed. This hormonal control is significant because it provides a specific target for disrupting blood digestion in mosquitoes. This mechanism can be considered as a drug target in mosquito control.

How could these findings about juvenile hormones and trypsin be used to control mosquitoes?

Targeting juvenile hormone III (JH III) regulation of trypsin production could lead to new mosquito control methods. If scientists can disrupt the splicing process or interfere with JH III signaling, they might be able to prevent mosquitoes from digesting blood properly. This could involve developing insecticides that specifically target these processes or other control methods that interfere with hormonal regulation. This is important because it offers a more targeted approach compared to broad-spectrum insecticides, potentially reducing harm to non-target species and the environment. Further research is required before this can be implemented.