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Ultrastructure of ER-bodies in statocytes and cells of the distal elongation zone of Arabidopsis thaliana (L.) heynh. root apices under X-radiation

Among plants used in spaceflight experiments, species of family Brassicaceaeare considered as the most resistant to radiation exposure. It is supposed that ER-bodies, which are derivative of granular endoplasmic reticulum and selectively accumulate an enzyme β-glucosidase, may be responsible for this resistance. The aim of the study was to investigate the ultrastructure and topography of ER-bodies in statocytes and cells of the distal elongation zone in root apices of A. thaliana seedlings in the control and under X-radiation. Methods. Seedlings grown on agar nutrient medium were treated with X-rays of doses 0.5 Gy, 1 Gy, 2 Gy, 4 Gy, 6 Gy, 8 Gy, 10 Gy, and 12 Gy on the unit RUM-17 (dose rate 0.43 cGr/s). The root apices were fixed with a mixture of epoxide resins. Ultra-thin longitudinal sections were investigated with a transmission electron microscope JEM-1230 EX. Results. It was shown the similarity in the root apex cell ultrastructure in control and under X-radiation. At the same time there were some differences in the ultrustructure of statocytes and cells of the distal elongation zone under X-radiation. An increase in the number of profiles
of granular endoplasmic reticulum and the total area of ER-bodies per cell in two hours and ten days after X-radiation more than twice in comparison to control was established. It was revealed the variability of ER-bodies in shape and size depending on the dose of X-rays. The nature of such alterations in the cell may indicate certain changes in metabolism, carried out within the range of cell physiological responses.
Conclusions. For the first time, the influence of X-radiation on dynamics of the formation of ER-bodies, which are derivative of granular endoplasmic reticulum, in statocytes and cells of the distal elongation zone in root apices of A. thaliana seedlings has been studied. The increased area of ER-bodies, which contain β-glucosidase (PYK 10), is considered as an adaptive cell response to ionizing radiation.