Researchers have discovered a novel method for pinpointing genetic targets that could aid in managing mosquito populations, potentially serving as a substitute for traditional insecticides. Their research examined the genetic foundations of species incompatibility through breeding experiments. They mated Ae. aegypti, a prominent vector for global arboviral illnesses, with its closely related species, Ae. mascarensis, which is found in the Indian Ocean. When the offspring are bred back with one of the parent species, nearly 10 percent exhibit intersex traits that prevent reproduction.
Virginia Tech researchers have developed a groundbreaking approach to identify genetic targets that can be used to control mosquito populations, presenting a potential alternative to insecticides.
Their recent publication in Communications Biology highlights the genetic reasons for species incompatibility. The researchers conducted hybrid crosses between Ae. aegypti, a key vector for various diseases, and its sister species, Ae. mascarensis. It was observed that about 10 percent of the resulting hybrid offspring became intersex and could not reproduce.
In their investigation, the scientists uncovered irregularities within the sex determination pathways of these intersex mosquitoes. These mosquitoes possess a genetic male makeup but show a combination of male and female gene expressions, leading to a mix of physical characteristics.
With a deeper understanding of these genetic elements, the researchers aim to devise methods to produce all-male mosquito populations, which could effectively decrease populations by removing females. This study may also help in pinpointing genes that influence female mosquito behavior, aiding in the development of future pest control strategies.
The implications of this research are crucial for managing diseases like Zika and dengue, as improved mosquito control could mitigate the transmission of these pathogens.
Although insecticides have historically been effective in managing mosquito counts, their efficiency is now declining, and they pose ecological risks.
“We’ve explored the hybridization between two mosquito species, found disturbances in the sex determination pathways of intersex individuals, and identified gene expressions specific to each sex,” stated Igor Sharakhov, one of the project researchers and an entomology professor affiliated with the Fralin Life Sciences Institute. “This study can uncover new genes related to sex determination pathways that are applicable in mosquito control initiatives.”
The research team examined three main aspects:
- The structural and anatomical levels of intersex mosquitoes, focusing on both external and reproductive organs
- The genes related to the sex determination process, specifically monitoring one key regulator and two genes generating male-specific and female-specific splicing variants
- The overall gene expression in these mosquitoes to distinguish between normal and abnormal gene activity associated with sexual development
“Our findings indicate that the morphological issues begin during the pupal stage, and in adults, the most extreme cases present both testes and ovaries in a single individual, which is quite rare among these species,” Sharakhov explained. “Our next objective is to uncover the underlying causes of these abnormalities.”
The researchers observed that intersex mosquitoes express both male and female variants of sex determination genes, resulting in diverse physical traits. While genes typically associated with females are expressed appropriately in intersex mosquitoes, the male-associated genes show reduced expression in some male reproductive tissues, although the genes linked to testes remain stable.
This study can facilitate mosquito management by revealing new genes involved in sex determination, enabling the creation of all-male populations that could significantly reduce female numbers and, consequently, vector populations. Furthermore, identifying sex-specific genes could lead to advancements in genetic methods to adjust traits in wild mosquito populations.
“Given that intersex mosquitoes have a genetic male background but exhibit female gene expressions, they offer an opportunity to identify genes that impact female behaviors, useful for future vector control approaches,” noted Jiangtao Liang, a postdoctoral researcher in entomology. “Intersex individuals can act as important models for discovering genetic factors linked to sex determination, sexual differentiation, mating, host-seeking, and blood-feeding behaviors among mosquitoes. Identifying new genes and their disruptions related to sex determination will contribute to effectively controlling disease vectors through genetic modifications targeting sex separation.”
By advancing our understanding of mosquito genetics, particularly for diseases like Zika and dengue, we can develop more effective control methods, ultimately reducing disease transmission globally.
