Accumulation of two cytoplasmic polypeptides in roots of Al-sensitive and Al-resistant barley cultivars during Al, pH and metal stress

The accumulation of two cytoplasmic polypeptides (27.5 and 28.0 kDa) in roo ts of Al-sensitive (Alfor) and Al-resistant (Bavaria) barley cultivars were analysed during stress conditions induced by different Al3+ concentrations , pH values of root medium, and some heavy metals (Cu2+, Cd2+, Co2+) treatm ent. In both cultivars aluminium (Al3+) in concentrations ranging from 5 up to 150 mu M induced an increased accumulation of 27.5 and 28 kDa cytoplasm ic polypeptides. In Al-resistant barley this accumulation appeared very ear ly after the application of AlCl3 into the root medium, while in Al-sensiti ve cultivar 24 h delay was observed. Increased concentrations of Al in root solution from 10 up to 150 mu M did riot cause quantitative differences in polypeptide pattern of root cytoplasmic proteins between the two barley cu ltivars. Changes in pH values of root medium (pH 3.5-6.5) did not show any effect on the accumulation of 27.5 and 28 kDa polypeptides in Al-sensitive or in Al-tolerant barley cultivar. However, differences were found between the two barley cultivars during heavy metal treatment. Application of 10 mu M concentration of heavy metals (Cu, Cd, and Co) in the root medium on Al- sensitive cultivar Alfor resulted in similar accumulation of 27.5 and 28.0 kDa polypeptides as it was found after Al treatment. On the other hand, the metal stress did not induce accumulation of these two polypeptides in root s of Al-resistant cultivar Bavaria. Our data suggest that 27.5 and 28.0 kDa polypeptides are not specifically involved in Al resistance. These polypep tides probably belong to the group of non specific stress polypeptides whic h accumulate in roots of Al-sensitive barley during Al and heavy metal trea tment, while in Al-resistant cultivar only during Al treatment.