The Role of Betaine Lipids in Adaptation of Lichen Peltigera Aphthosa to Long-Term Dehydration

Abstract

Diacylglyceryl-N,N,N-trimethylhomoserine (DGTS) is a common lipid component of a number of green algae and cryptogamic plants (Sato, 1992; Kato et al., 1996) as well as some fungi (Künzler, Eichenberger, 1997). The cellular localization and site of biosynthesis of DGTS are associated with non-plastidial structures (Künzler et al., 1997; Moore et al., 2001). As regards the biosynthesis of DGTS, S-adenosyl-L-Met has been demonstrated to be a precursor for both the homo-Ser moiety of the headgroup and the methyl units (Moore et al., 2001). In spite of the progress in our knowledge about DGTS distribution and biosynthesis, there is an obvious lack of understanding of its physiological role. According to our previous results obtained on the lichen material the amount of DGTS remains unchangeable in stress conditions whereas the concentration of phospholipids decreases (Bychek-Guschina et al., 1999). This phenomenon may be simply explained by the greater resistance of DGTS molecules because the ether bond in the sn-3 position of glycerol moiety of DGTS is much more stable to hydrolysis than ester bond of phospholipids. However, since in some stresses the DGTS amount increases (Kotlova, 2000), it has been suggested that not only specificity of structure but also biosynthesis are responsible for the relative constancy of DGTS concentration, which seems to provide lichens with survival in different stress conditions. The present work describes experiments designed to test this proposal.