Environmental Stress, Adaptation, and Evolution

(Bijlsma, B., and Loeschcke, V. (eds.) Birkhauser, Basel-Boston-Berlin, 1997)

Dramatic and stress-inducing changes in the environment can apparently influence the survival of an organism even if the changes are transient. This is why stress can be considered as one of the important factors of evolution.

The reviewed book attempts to organize into a single volume various aspects of stress considering possible adaptational and evolutional consequences. The reader can find some facts about biochemistry and molecular biology of stress and behavior of individuals, populations, and ecosystems in response to sudden environmental changes. The book is predominantly based on the oral presentations during the 5th International Congress of Evolutional Biology and Systematics (Budapest, August 1996) but also includes chapters written by specifically invited leading biologists.

The book is opened by an introductory chapter written by the editors. The introductory chapter includes the following sections: extreme conditions and adaptation; acclimatization in response to temperature stress; stress, selection, and extinction; evolution and stress. The book includes contributions from L. A. Zhivotovsky, P. Kalow, P. A. Parsons, A. A. Hofman, P. R. Sheldon, and others.

According to Bijlsma and Loeschcke, the problem stated in the title of the book was first suggested 1940 by N. V. Timofeev-Resovsky. Since then, the idea has been developed not only in theoretical studies of evolutionary biologists but also in experimental biological works.

The chapters by M. E. Fider and R. A. Krebs are of particular interest to biochemists as well as the chapter of V. Loeschcke et al. on the role of the 70-kD heat shock protein (Hsp70) in acclimatization of drosophila.

In the first chapter, increase in the temperature of the environment was shown to induce additional copies of the gene encoding Hsp70, thus increasing the content of this protein in the cytoplasm of drosophila cells. In the flies, Hsp70 apparently plays a chaperoning role in the renaturing of denatured proteins (as in other organisms). It is not surprising that increase in Hsp70 level enhances the temperature resistance of drosophila. However, this beneficial effect has certain negative influences, including slow growth and increased mortality during transformation of larvae into imagoes at normal temperature. Unfortunately, the authors did not analyze the effect of Hsp70 on the life span of imagoes. This parameter is of interest because shortened life-span increases the frequency of alternation of generations, and this can be beneficial for evolution of the biological species because the more frequently the generations are alternated, the higher is the probability of appearance and fixation in the offspring of new features required for adaptation to the more aggressive environment. The data of M. E. Fider and R. A. Krebs can be compared to the recent work of E. Moore who demonstrated that increase in mitochondrial level of Hsp70 in tobacco induces dramatic acceleration of the growth and increase in the size of the plants (for discussion, see Biochemistry (Moscow), 1998, 63, 1335-1343).

Recent data on the effect of stress on mutation frequency in bacteria are summarized in the very interesting chapter by F. Taddei et al. It was shown that stress induces repression of synthesis of certain proteins which repair DNA damage and also induces synthesis of the components of the SOS system that was shown not only to defend the bacteria from damage caused by the aggressive environment but also to increase genetic variability of the population by stimulating mutagenesis and other changes in bacterial DNA. This response to stress can be considered as an example of a specialized biochemical mechanism of evolution. Using this mechanism, the cell can regulate mutation frequency, optimizing it to changes in the environment.

Academician V. P. Skulachev

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