Abstract
<p>Autoradiographic studies of <sup>3</sup>H-uridine incorporation (20-min incubation) and dynamics of radioactive particle translocation from nucleolus into cytoplasm (following 80-min postincubation in non-radioactive medium) in root meristematic cells of soybean have been carried out. The experiment was performed with plants subjected to 4-day acclimation in chilling or subjected to 2-hour cold stress and control plants. Three cultivars of soybean: Mazowia, Polan and Progres (cultivated in Poland) were used in the experiment.</p><p>It has been shown that in control conditions the greatest number of RNA precursor is incorporated into nucleoli after 20-min incubation. Following 80-min postincubation cytoplasm is the most radioactive area of the cell - this mainly testifies to dynamic translocation of radioactive ribosome subunits from nucleolus into cytoplasm.</p><p>In chilling conditions the reduction of <sup>3</sup>H-uridine incorporation into cells occurs, as compared to control conditions. Plants subjected to a 4-day acclimation incorporate the radioactive precursor more intensively than plants subjected to cold stress.</p><p>Following 80-min postincubation - in the case of acclimated plants - the nucleolus is the most radioactive area of the cell, which testifies to accumulation of pre-rRNA in it. After the cold stress cytoplasm is more radioactive than the nucleolus. In all three cultivars the processes of synthesis and transport of pre-rRNA particles are similar, only their intensity is different.</p><p>Morphometric measurements of nucleoli in all cultivars subjected to 4-day chilling have shown that root cell nucleoli are larger than those in control. This phenomenon can be connected with stronger inhibition of rRNA transport than its synthesis.</p>
Highlights
Low temperature stress is one of the major problems in agricultural production
Plants subjected to a 4-day acclimation incorporate the radioactive precursor more intensively than plants subjected to cold stress
Following 80-min postincubation in the case of acclimated plants the nucleolus is the most radioactive area of the cell, which testifies to accumulation of pre-rRNA in it
Summary
Low temperature stress is one of the major problems in agricultural production. It mainly refers to chill-sensitive plants, including soybean plants, which poorly tolerate exposure to temperatures between 15-0°C (Chen 1994).Chilling stress causes a number of changes at cytophysiological level leading to weakening and/or impairment of some cellular processes, it leads to reduction of plant development and growth (Mc Kersie and Leshem 1994).Disturbances of cell physiology can occur at different stages of cellular processes including the stage of machinery production for protein synthesis, which takes place in the nucleolus.Nucleolus, though it is a plurifunctional cellular structure (Pederson 1998), is primarily the site of pre-rRNA synthesis and of maturation of pre-ribosomal subunits (Olson et al 2000; Visintin and Amon 2000; Ospina and Matera2002). Low temperature stress is one of the major problems in agricultural production. Disturbances of cell physiology can occur at different stages of cellular processes including the stage of machinery production for protein synthesis, which takes place in the nucleolus. Nucleolus, though it is a plurifunctional cellular structure (Pederson 1998), is primarily the site of pre-rRNA synthesis and of maturation of pre-ribosomal subunits It is the structure responsive to abiotic stress factors including low temperature (Gabara 1980; Stêpiñski and Kwiatkowska 2003) and heavy metals (Gabara et al 1995; Jiang et al 2000). In the majority of cases, on the number of active rRNA genes
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