EFFECT OF DNA METHYLATION ON GRAVISENSITIVITY OF MOSSES

Abstract

Gravity is a constant environmental factor in plant growth and development. Real or simulated microgravity causes stress responses in plants, in which DNA methylation is involved. We investigated the effect of the DNA methylation inhibitor 5-azacytidine (5-aza) on the perception and transduction of the gravity signal into gravitropism and on the peroxidase isoenzyme spectra in Physcomitrium patens (Hedw.) Mitt. protonemata under conditions of altered gravity, as well as on Polytrichum arcticum Sw. ex. Brid. phenotype branching and variability of gravitropic angles of lateral branches. The influence of DNA methylation on the perception and realization of the gravity signal was determined. DNA demethylation in the 5-aza presence decreased the gravisensitivity of stolons — less at the stage of perception and more during gravity signal transduction. An analysis of gravitropism under the inhibiton of DNA methylation showed the signal preservation in cell memory regardless of the stage of gravistimulation. However, cell memory about a signal was shorter at the perception stage and longer at the transduction stage, that affects a rate of the gravitropic growth recovery. The different effect of DNA methylation on gravi-induction is considered as an epigenetically regulated process that modifies morphological differences in mosses’ tropismunder under real microgravity in space flight and simulated microgravity on earth. Resistance to microgravity depends on intensity of cell wall metabolism. Peroxidase activity plays an important role in the biogenesis and mechanical stability of the cell wall. It was shown that the changes in the expression of peroxidase genes and enzyme isoforms in the P. patens protonemata may be a result of DNA demethylation. Epigenetic polymorphism of peroxidase under microgravity is regarded as a probable factor of individual resistance of plant organisms.