The Expression Levels of Heat Shock Protein 90 (HSP90) in Galleria mellonella Following Infection with the Entomopathogenic Nematode Steinernema carpocapsae and Its Symbiotic Bacteria Xenorhabdus nematophila.

Simple Summary: This study investigates how heat shock protein HSP90 helps Galleria mellonella larvae respond to stress from the nematode Steinernema carpocapsae and its symbiotic bacterium Xenorhabdus nematophila. Live nematodes slightly increased HSP90 expression, while dead nematodes had no effect, suggesting nematode secretions or bacteria do not directly impact HSP90. However, nematodes with altered surface properties significantly boosted HSP90 expression. X. nematophila also raised HSP90 levels, but this effect disappeared when weakly bound surface proteins were removed. Under heat stress, live nematodes reduced heat-induced HSP90 expression, whereas surface-treated nematodes increased it. These findings suggest that HSP90 plays a role in the immune system's ability to detect and respond to biological threats. This interaction could be key for improving biological pest control methods, especially as climate change affects environmental conditions. Further research is needed to understand the pathways regulating HSP90 and how entomopathogens evade immune defenses, particularly under changing temperatures, to enhance the effectiveness of bioinsecticides. Heat shock proteins (HSPs), particularly HSP90, play a vital role in insect responses to environmental and biotic stresses by maintaining protein stability and supporting immune defenses. This study explores HSP90 regulation in Galleria mellonella larvae following exposure to the nematode Steinernema carpocapsae and its symbiotic bacterium Xenorhabdus nematophila. Exposure to live nematodes caused slight changes in HSP90 expression, while non-viable nematodes had no effect, suggesting that nematode secretions or symbiotic bacteria do not directly influence HSP90 levels. However, nematodes with altered surface properties significantly increased HSP90 expression. X. nematophila also moderately elevated HSP90 levels but this effect disappeared when weakly bound surface proteins were removed. Interestingly, under thermal stress, live nematodes reduced heat-induced HSP90 expression, whereas surface-treated nematodes enhanced it. These findings suggest that HSP90 modulation is influenced by biological control agents, highlighting a potential link between HSP90 and immune detection of invaders. This interaction may be crucial in adapting biological control strategies in response to climate change. Further research is needed to clarify HSP activation pathways, host immune interactions, and mechanisms of entomopathogen immune evasion, particularly under varying environmental temperatures, to enhance bioinsecticide efficacy. [ABSTRACT FROM AUTHOR]

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