QUANTITATIVE CHANGES IN CYTOPLASMIC AND MICROSOMAL PROTEINS ASSOCIATED WITH ALUMINUM TOXICITY IN 2 CULTIVARS OF WINTER-WHEAT

Seedlings of two sister lines of hard red winter wheat, Tx78 (Al-sensitive) and Tx84 (Al-tolerant), were given a 24-h pulse of Al sufficient to irreversibly inhibit growth in the sensitive but not the tolerant cultivar. Proteins were then extracted from root tips of both cultivars, separated by 2D-PAGE, and quantified using computer analysis of gels. The objective of the work was to determine if the major changes in protein expression associated with Al stress were cultivar-specific, if the changes correlated with Al tolerance, and if they occurred in a specific fraction of cell proteins. Of the approximately 600 proteins examined, 14 cytoplasmic proteins and eight microsomal proteins were induced or enhanced by Al treatment in one or both cultivars, while nine cytoplasmic and 12 microsomal proteins were diminished or repressed. Among the 43 proteins significantly altered by Al treatment, three cytoplasmic proteins, and no microsomal proteins, were induced or enhanced solely in the Al-tolerant cultivar. Al affected the programme of formation of both cytoplasmic and microsomal proteins, but appeared to cause the greater change in proteins associated with the cytoplasm. The results indicate that most of the changes in protein expression associated with Al stress probably result from effects of Al on cell metabolism, and that only a few proteins may be induced or enhanced as part of a cultivar-specific mechanism of Al tolerance.