Changes in the Content of Carotenoids in Moss Shoots Hylocomium splendens Hedw. under Conditions of Temperature Stress

The ability of plants to adapt to unfavorable living conditions is a necessary condition for the survival of plants, the preservation of the genotype, and the maintenance of flora diversity. A promising approach to solving the problem of increasing plant resistance is to study the mechanisms of stress resistance of “extremophiles”, including mosses, higher nonvascular plants. The relative simplicity of their anatomical structure and ability to survive in unfavorable environmental conditions make these evolutionarily ancient plants ideal models for studying adaptation mechanisms. It is known that the functional activity of the photosynthetic apparatus can change dynamically under the influence of stress factors. In this work, we conducted a study of stress-induced changes in the content of carotenoids in the forest moss Hylocomium splendens Hedw. under temperature stress conditions. We have identified the main carotenoids of H. splendens moss. It has been established that the relative content of lutein, β-carotene, and zeaxanthin increased under the influence of negative and elevated temperatures, while the total content of carotenoids decreased under temperature stress. It was shown that 1 h of exposure to unfavorable temperatures led to a significant decrease in nonphotochemical quenching of chlorophyll fluorescence a, with stronger changes observed when exposed to negative temperatures. Transcript level analysis of HsLUT1, one of the key genes for lutein biosynthesis, showed a significant increase of four to five times under temperature stress. Thus, our data revealed that changes in the expression of the carotenoid biosynthesis gene are accompanied by changes in their content under temperature stress. The data obtained expand our knowledge of resistance mechanisms in bryophytes and will contribute to the understanding of evolutionary changes in stress resistance in higher plants.