Changes in total protein profiles of barley cultivars in response to toxicboron concentration

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. T otal protein patterns were obtained by analysis of total protein extract fr om root and leaf tissues of control and B-treated plants using two-dimensio nal gel electrophoresis followed by silver staining. The protein profile of B-treated seedlings of each cultivar was compared to the profile of contro l (no stress treatment) plants of the same cultivar. Silver-stained gels sh owed 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 syn thesized protein with relative molecular weight (Mr) of 35.0 kDa was detect ed 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 q uantitatively increased in B-treated root profile of both cultivars. Follow ing B treatment, three proteins were increased in root profile of the toler ant cultivar, but were not changed in the sensitive one. In leaf tissues, h owever, there were remarkable changes in total protein profiles after B tre atment, relative to the control. Following B treatment, in leaf tissues, at least seven proteins were increased in amount in tolerant cultivar but wer e unchanged in the susceptible one. In tolerant and sensitive cultivars, am ounts of two proteins were increased in B-treated plants, relative to contr ol seedlings. In addition, four proteins (M:29, 58, 58, and 22 kDa) were un changed in control and B-treated seedlings of the tolerant cultivar. In the susceptible cultivar however, among these four proteins, the first one (Mr :29) was very much reduced and the others (Mr:58, 58, and 22 kDa) were comp letely lost in B-treated seedlings. Moreover, following B treatment, a set of high-molecular-weight proteins was quantitatively decreased in the susce ptible cultivar but was unchanged in the tolerant cultivar. These results i ndicate 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. The refore, it is suggested that these changes, especially at shoot level may f orm the basis of the tolerance mechanism to B toxicity.