MODELED MICROGRAVITY IMPACT ON THE CYTOSKELETON ORGANIZATION IN ARABIDOPSIS THALIANA ROOT CELLS

Planning manned space missions requires long-term cultivation of various types of plants, and this necessitates the detection of microgravity’s impact on root cells since the nutrition and orientation of plants depend upon the state of the root system. Analysis of how cytoskeleton proteins function in simulated microgravity is essential for understanding the mechanisms of rapid cell response to external stimuli, which is inherent in plants. The organization of the tubulin component of the cytoskeleton and the mechanisms of its regulation by associated proteins were studied under the conditions of horizontal clinorotation, which changes cell polarity, eliminates directional influence, and minimizes the gravity effect. Experiments have shown that slow clinorotation causes mechanical stress associated with a significant decrease in the gravitational load on the side cell walls. This affects the organization of the tubulin cytoskeleton — a complex system of polymeric proteins whose functions are to ensure the shape of the cell, cell signaling and growth. Namely, a partial deviation of cortical microtubules from the transverse orientation in the cell of the A.thaliana root elongation zone was revealed. The above may be the result of a decrease in the expression of the TUA6 gene, which encodes the structural subunit of microtubule polymers, and the CLASP gene, whose protein regulates the organization of the microtubule network. A decrease in gene expression leads to the alteration of both the polymerization of microtubules and their connection with the cytoplasmic membrane, which is visually manifested in partial disorientation of individual microtubules in epidermal and cortical cells. Thus, the reduction of the gravitational load from clinorotation on the cell eliminates the need for a rigid network of the cortical cytoskeleton and affects its partial disorganization, which, in turn, leads to the discoordination of plant root growth. Investigation of the cytoskeleton influence on the growth characteristics of plants in microgravity essentially contributes to the development of plant growth technologies for long-term space flights.