ABA pretreatment can alter the distribution of polysomes in salt-stressed barley sprouts

The study analyzed caryopses of barley (Hordeum vulgare) cv. Stratus. Caryopses were germinated in darkness at 20°C in three experimental setups: (a) in distilled water for 24 hours, followed by 100 mM NaCl for another 24 hours (salinity stress, SS), (b) in 100 μM of abscisic acid for the first 24 hours, followed by rinsing with distilled water to remove residual ABA, and in 100 mM NaCl for another 24 hours (ABA pretreatment + salinity stress, ABAS), (c) in distilled water only (control, C). Changes in the content of free polysomes (FP), membrane-bound polysomes (MBP), cytoskeleton-bound polysomes (CBP) and cytomatrix-bound polysomes (CMBP) were examined in barley sprouts germinated in SS and ABAS treatments for 48 hours. In salt-stressed barley sprouts, the concentrations of membrane-bound and cytoskeleton-bound polysomes (MBP, CBP and CMBP) decreased significantly, whereas an increase was noted only in the free polysome (FP) fraction. ABA pretreatment altered the distribution of polysomes in stressed plants. The content of cytoskeletonbound polysomes (CBP and CMBP) increased, FP levels decreased, whereas no changes in MBP content were observed in response to ABA treatment. Our results suggest that plants respond to salt stress by increasing the concentrations of free polysomes that are probably released from damaged cell structures, mainly membranes. Our present and previous findings indicate that ABA could inhibit the release of FP in stressed plants by enhancing polysome binding to the cytoskeleton.