ELUCIDATION OF CELLULAR MECHANISMS OF AUTOPHAGY INVOLVEMENT IN PLANT ADAPTATION TO MICROGRAVITY CONDITIONS

Abstract

It was shown that clinostating conditions induce autophagy without increasing of programmed cell death (PCD) index in the epidermal cells of the root apex of A. thaliana seedlings. After the phase of activation of autophagy, its regulatory weakening occurs, which probably indicates adaptive changes to the conditions of clinostating. The induction of autophagy correlates with an increase in the expression levels of atg8 genes, some of which (atg8e and atg8i) may be involved in the implementation of autophagy under the simulated microgravity conditions. The transcriptional activity of cytoskeleton genes involved in the implementation of stress-induced autophagy, in particular α- and β-tubulin genes, was analyzed. Joint expression of α- and β-tubulin genes and atg8 under the simulated microgravity conditions was revealed. These results illustrate the role of the cytoskeleton in the development of microgravity-induced autophagy and make it possible to identify genes specific to this type of stress. The induction of autophagy and PСD was studied under the action of gamma irradiation as a concomitant factor of space flights, as well as under the combined action of acute irradiation and clinostating. Gamma irradiation in doses equivalent to those in the spacecraft cabin (1 - 6 Gy) induced dose-dependent changes in the topology and cytogenetic state of the root apical meristem, as well as slightly inhibited of the early plant development. In the meristem, heterogeneity increased, PCD indexes, mainly proliferative death and autophagy, increased. With the combined action of gamma irradiation (2 Gy) and clinostating, the density of autophagosomes in the epidermal cell root apices of 6-day-old seedlings increased (24 hours after irradiation), and after 4 days it decreased, compared to the non-irradiated control.