Changes in the lipid composition of <i>Peltigera canina</i> at an elevated temperature

Abstract

Extremophile organisms can survive under extreme conditions through tolerance mechanisms. Such organisms include lichens, which are symbiotic associations of fungi and algae and/or cyanobacteria. Among other factors, the high stress tolerance of lichens can be attributed to their ability to synthesize a wide range of metabolites, including chemically diverse lipid compounds. Despite their obvious relevance, the biochemical mechanisms of stress tolerance in lichens that are mediated by changes in the lipid profile remain understudied. Peltigerous lichens constitute a separate division of lichens characterized by high growth rates and metabolic activity indices. Taking into account the temperate climate in which these lichens grow, it can be assumed that they may be highly sensitive to temperature fluctuations. These factors led to the choice of Peltigera canina, epigeic lichen, as the subject matter of this study. The present work examined stress-induced changes in the redox status of P. canina, as well as changes in its lipid composition at an elevated temperature (40 °С). The exposure of hydrated lichen thalli to an unfavorable temperature led to an increase in the level of hydrogen peroxide, phenoloxidase activity, and lipid peroxidation, which constitutes an important part of stress response in lichen. The stress-induced changes in the redox status of lichen thalli stimulated an increase in lipophilic antioxidant agents: a dramatic increase in the level of α-tocopherol and an increase in carotenoids, specifically β-carotene. Thus, the accumulation of lipophilic antioxidants constitutes an important part of the lipid-mediated stress response of P. canina to temperature elevation.