Changes in total protein profiles of barley cultivars in response to toxic boron concentration

Abstract

In this study, ten‐day‐old seedlings of barley {Hordeum vulgare L. cultivar Anadolu [boron (B)‐tolerant] and Hamidiye (B‐sensitive)} were used. Boron‐treated plants were grown on H₃BO₃ solution (final concentration of 10 mM) for five days. Control plants received no B treatment during this period. Total protein patterns were obtained by analysis of total protein extract from root and leaf tissues of control and B‐treated plants using two‐dimensional gel electrophoresis followed by silver staining. The protein profile of B‐treated seedlings of each cultivar was compared to the profile of control (no stress treatment) plants of the same cultivar. Silver‐stained gels showed that B stress caused increases or decreases in a number of proteins in root and leaf tissues. Moreover, as a result of B treatment, one newly synthesized protein with relative molecular weight (M_r) of 35.0 kDa was detected in root profile of the tolerant cultivar. This protein failed to show up in root profile of the B‐treated sensitive cultivar. Three proteins were quantitatively increased in B‐treated root profile of both cultivars. Following B treatment, three proteins were increased in root profile of the tolerant cultivar, but were not changed in the sensitive one. In leaf tissues, however, there were remarkable changes in total protein profiles after B treatment, relative to the control. Following B treatment, in leaf tissues, at least seven proteins were increased in amount in tolerant cultivar but were unchanged in the susceptible one. In tolerant and sensitive cultivars, amounts of two proteins were increased in B‐treated plants, relative to control seedlings. In addition, four proteins (M_r:29, 58, 58, and 22 kDa) were unchanged in control and B‐treated seedlings of the tolerant cultivar. In the susceptible cultivar however, among these four proteins, the first one (M_r:29) was very much reduced and the others (M_r: 58, 58, and 22 kDa) were completely lost in B‐treated seedlings. Moreover, following B treatment, a set of high‐molecular‐weight proteins was quantitatively decreased in the susceptible cultivar but was unchanged in the tolerant cultivar. These results indicate that in barley, certain proteins may be involved in tolerance to B toxicity. In this study, changes in polypeptide composition as a result of B toxic concentration in leaf tissues were more abundant than in roots. Therefore, it is suggested that these changes, especially at shoot level may form the basis of the tolerance mechanism to B toxicity.