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Evolution of immune response under chronic thermal stress.

Graduate Student Seminar Series | Biswajit Shit | November 23, 2023

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Climate warming is a critical concern for global health and disease management. The cost that organisms are paying for climate warming is two-fold. Studies have shown that temperature variability can disrupt host immunity by affecting its various aspects such as melanization, phagocytic activity, antimicrobial peptides in insects, or antibody production in mammals. Warming can also trigger an overreactive immune response, leading to host cytotoxicity.  On the other hand, high temperature causes more DNA damage and disrupts organisms’ DNA repair ability leading to higher mutation transmission. Can organisms mitigate those costs by adapting to chronic thermal stress? Also, can organisms adapted to chronic heat stress also evolve against the selection pressures imposed by pathogens? Addressing this, we have taken an experimental evolution approach where initially, we subjected a baseline population of Drosophila melanogaster to high-temperature conditions (29°C). Subsequently, we will select our control (AL) and high-temperature selected (HSL) regimes for improved resistance against bacterial infection. We found that the population evolved under high-temperature conditions exhibits enhanced fertility and starvation resistance in warm environments. However, selection doesn’t have any effect on the accelerated development time in warm conditions. This discrepancy in performance under warm conditions may be due to the accelerated metabolic rate and associated energy depletion, which could be mitigated by evolutionary changes to maintain metabolic homeostasis. We plan to explore this mechanistically through metabolomics. Moreover, our results reveal reduced post-infection survival against Providencia rettgeri and Pseudomonas entomophila at higher temperatures. Also, HSL pays a cost of adapting to thermal stress by reduced post-infection survival against P. entomophila. Future investigations will focus on evaluating the response of selection lines when exposed to bacterial selection pressure in each generation. We will check whether adaptation to thermal stress helps organisms to mitigate the cost of higher mutation transmission or the effect will be exacerbated. This research will shed light on the adaptability of host immune systems in the face of climate warming and infectious diseases.

About the Speaker:

Biswajit Shit is a Ph.D. candidate in the Evolutionary Immunology lab under Dr. Imroze Khan at the Department of Biology, Ashoka University. Prior to joining his Ph.D., he did his BS-MS dual degree in Biology from IISER Mohali. His research interests include evolutionary biology, population genetics, and understanding the evolutionary implications of host-pathogen interactions.  

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