thermotolerance

Thermotolerance is the ability of an organism or its cells to survive elevated temperatures that would normally be detrimental. It can be innate (basal) or acquired after exposure to heat or similar stress. Acquired thermotolerance typically arises after a mild sublethal heat exposure that triggers a protective program, enabling survival of a subsequent more severe heat challenge. The concept is observed across bacteria, yeasts, plants, and animals, including humans, and is relevant to ecology, agriculture, and medicine.

At the center of acquired thermotolerance is the heat shock response. Heat shock factors (HSFs) activate transcription of heat shock proteins (HSPs) and other chaperones that assist in protein folding, prevent aggregation, and facilitate degradation of damaged proteins. Additional protective changes include antioxidant defenses, membrane remodeling, and alterations in metabolism. In plants, heat acclimation involves signals such as reactive oxygen species, calcium, and hormones (e.g., abscisic acid) that coordinate HSP expression and other protective pathways. In microbes, thermotolerance can involve alterations in membrane composition, compatible solutes, and stress response regulons.

Ecological and practical significance of thermotolerance includes shaping species ranges under warming climates, improving crop resilience, optimizing industrial fermentation, and informing cancer therapy strategies that target heat response pathways. While some organisms exhibit constitutive thermotolerance, others reveal plastic acclimation that enhances survival after heat exposure.