Remarkable Durability: The Metabolic Adaptations Enabling the Longevity of Zika-Carrying Mosquito Eggs

Remarkable Durability: The Metabolic Adaptations Enabling the Longevity of Zika-Carrying Mosquito Eggs

Captured in a research laboratory, a male and a female Aedes aegypti mosquito were examined. These mosquitoes are vectors for the Zika virus, and a recent study has discovered that their eggs possess the ability to withstand extended periods of dryness due to shifts in their metabolic activity. Credit: Anjana Prasad

The eggs of mosquitoes responsible for transmitting the Zika virus have shown a capacity for long-term survival through metabolic modifications, presenting possible avenues for vector control.

A new study, released on October 24th in the open-access journal PLOS Biology, reveals that eggs of the Aedes aegypti mosquito can survive sustained desiccation by undergoing metabolic alterations. Conducted by Anjana Prasad, Sunil Laxman, and associates at the Institute for Stem Cell Science and Regenerative Medicine in Bengaluru, India, as well as the Indian Institute of Technology in Mandi, India, this research suggests potential strategies for limiting the spread of this disease-carrying mosquito.

Sustaining Life Through Dry Conditions

The majority of cellular structures in living organisms are water-based, making desiccation a potentially lethal occurrence as many proteins and cellular molecules require adequate hydration to maintain their structure. While numerous microbes have evolved methods to withstand desiccation, only a handful of animals possess this capability. Included in this select group is the Aedes aegypti mosquito, a vector for several viral illnesses such as Zika, dengue, yellow fever, and Chikungunya. Originally native to North Africa, Ae. aegypti has now spread globally and poses risks in warm, humid regions worldwide.

Metabolic Resilience and Preservation

The eggs of Aedes mosquitoes need between 48 to 72 hours to develop into larvae. The researchers first established that eggs must be a minimum of 15 hours old to endure desiccation; any younger and they fail to hatch upon rehydration. Comparative analysis of the proteomes of desiccated and non-desiccated viable eggs showed considerable alterations in metabolic pathways. Specifically, there was an elevation in the enzymes of the tricarboxylic acid (Krebs) cycle promoting lipid metabolism, and a decline in enzymes connected to glycolysis and ATP-generating sections of the TCA cycle. This effectively diverted cellular metabolism towards fatty acid production and utilization. Concurrently, metabolism was generally reduced while the amino acids arginine and glutamine saw an increase in levels. Enzymes that mitigate the harmful impact of oxidative stress, a known byproduct of dehydration, also increased.

The Significance of Polyamines

Polyamines, formed by linking arginine molecules, are recognized for their protective qualities against cellular damage. In this study, the researchers demonstrated that the eggs accumulate polyamines, indicating their crucial role in desiccation resistance. Tests involving egg-laying female mosquitoes fed with a polyamine synthesis inhibitor showed that their eggs had a reduced ability to withstand desiccation compared to the control group. A second inhibitor, targeting fatty acid metabolism, also led to decreased egg viability post-desiccation. This inhibitor was found to reduce polyamine synthesis, suggesting that the breakdown of fatty acids serves to provide the energy needed to produce these protective polyamines.

Conclusions and Prospects for Future Research

Highlighting the global public health threat posed by Ae. aegypti mosquitoes, Laxman noted, “Given the rapid geographical expansion and their role as primary vectors for multiple viral diseases affecting nearly half of the global population, these findings lay the groundwork for strategies to reduce Aedes egg viability and their worldwide distribution.” He added that certain inhibitors which reduce the eggs’ resistance to desiccation, along with new agents affecting other parts of the desiccation tolerance pathway, could prove beneficial as vector-control substances.

Laxman further stated, “The eggs of Aedes mosquitoes have the ability to survive indefinitely in a completely desiccated state, eventually hatching into functional larvae. This is achieved by a metabolic rewiring that takes place during desiccation, allowing the embryos to protect themselves and revive when rehydration occurs.”

Reference: “Aedes aegypti Mosquito Eggs Endure Desiccation Through Metabolic Rewiring of Polyamine and Lipid Pathways” by Anjana Prasad, Sreesa Sreedharan, Baskar Bakthavachalu, and Sunil Laxman, 24 October 2023, PLOS Biology.
DOI: 10.1371/journal.pbio.3002342

Funding: No explicit funding was acquired for this study. Individual fellowships were supported by DST-INSPIRE (IF190149 to SS) and DBT/Wellcome Trust India Alliance (IA/I/19/1/504286 to BB). These funding agencies had no involvement in study design, data collection, data analysis, experimental backing, publication decisions, or manuscript preparation. In-house support was provided by the Tata Institute for Genetics and Society (to BB) and DBT-inStem (to SL).

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More about Desiccation Tolerance

• PLOS Biology: “Eggs of the mosquito Aedes aegypti survive desiccation by rewiring their polyamine and lipid metabolism”
• Institute for Stem Cell Science and Regenerative Medicine
• Indian Institute of Technology Mandi
• DST-INSPIRE
• DBT/Wellcome Trust India Alliance
• Tata Institute for Genetics and Society
• DBT-inStem