Formation and stability of polysomes and polysomal populations in roots of germinating seeds of soybean (Glycine max L.) under cold, osmotic and combined cold and osmotic stress conditions

Abstract

Abiotic stress factors such as extreme temperatures or osmotic stress are among the major causes of inferior crop yields. In response to a stress, plants have evolved various defense mechanisms. In our study, we have demonstrated how cold stress, osmotic stress and a combination of both stresses retard the growth of roots and inhibit the process of ribosomes binding into polysomes. The tested stresses also limited the ability of root tissues to synthesize proteins. At the same time, most of the analyzed samples were found to contain elevated shares of the fractions of cytoskeleton-bound polysomes (CBP, CMBP) in the total population of polysomes. Using a polysome-based degradation system, it was shown that polysomes formed under stress conditions were much more resistant to the effect of exogenous ribonuclease than the control ones. The highest tolerance to digestion was demonstrated by the cytoskeleton-bound (CBP) and cytoskeleton-membrane bound polysomes (CMBP). The increasing share of CBP and their stability in roots of seeds germinating under stress conditions can be a target for physiological regulation. It seems that modifications in the stability and percentages of particular polysomal populations play an important role in the adaptation of plants to stress conditions, which may indicate that these forms of polysomes, i.e., cytoskeleton-bound ones, are involved (via selective translation) in the synthesis of stress proteins in soybean roots.