Expression of heat shock proteins (HSPs) in Aedes aegypti (L) and Aedes albopictus (Skuse) (Diptera: Culicidae) larvae in response to thermal stress

- Quantitative real-time polymerase chain reaction was performed to assess expression levels of HSPs in response to thermal stress in the Andaman population of Ae. aegypti and Ae. albopictus under laboratory and in actual field conditions.
- Enhanced up-regulation of HSPs was evident in third instar larvae of Ae. aegypti with rise in water temperatures (31 °C, 33 °C, 34 °C) in the containers in the nature and thermally stressed (37 °C and 39 °C) in laboratory conditions.
- In Ae. albopictus up-regulation of HSPs was observed in field conditions at 34 °C only and when thermally treated at 37 °C, while down regulation was evident in larvae subjected to thermal stress in laboratory at 39 °C.
- The difference in expression levels of AeaHsp26, AeaHsc70 and AeaHsp83 genes in Ae. albopictus larvae was statistically significant between different exposure temperatures. All of these genes were significantly up-regulated at 37 °C.
- AeaHsp26, AeaHsc70 and AeaHsp83 are important markers of stress and perhaps function as proteins conferring protection and enhance survival in both the Aedes species.

Climatic changes are responsible, to a certain extent for the occurrence and spread of arboviral pathogens world over. Temperature is one of the important abiotic factors influencing the physiological processes of mosquitoes. Several genes of heat shock protein (HSP) families are known to be expressed in mosquitoes, which aid in overcoming stress induced by elevated temperature. In order to understand expression of HSP family genes in the Andaman population of Aedes aegypti and Aedes albopictus, we used quantitative real-time polymerase chain reaction (qPCR) to examine expression levels of HSPs in response to thermal stress under laboratory and in actual field conditions. HSP genes AeaHsp26, AeaHsp83 and AeaHsc70 were examined by comparing relative transcript expression levels at 31 °C, 33 °C, 34 °C, 37 °C and 39 °C respectively. Enhanced up-regulation of HSPs was evident in third instar larvae of Ae. aegypti with rise in water temperatures (31 °C, 33 °C, 34 °C) in the containers in the nature and thermally stressed (37 °C and 39 °C) in laboratory conditions. In Ae. albopictus up-regulation of HSPs was observed in field conditions at 34 °C only and when thermally treated at 37 °C, while down regulation was evident in larvae subjected to thermal stress in laboratory at 39 °C. Data on expression levels revealed that larvae of Ae. aegypti was tolerant to thermal stress, while Ae. albopictus larvae was sensitive to heat shock treatment. Statistical analysis indicated that AeaHsp83 genes were significantly up-regulated in Ae. aegypti larvae after 360 min exposure to high temperature (39 °C). The difference in expression levels of AeaHsp26, AeaHsc70 and AeaHsp83 genes in Ae. albopictus larvae was statistically significant between different exposure temperatures. All of these genes were significantly up-regulated at 37 °C. These results indicate that AeaHsp26, AeaHsc70 and AeaHsp83 are important markers of stress and perhaps function as proteins conferring protection and enhance survival of the Andaman population of both the Aedine species. Biological implications of these findings could impact the vector competencies.

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