QUANTIFICATION OF SILVER-STAINED PROTEINS RESOLVED BY 2-DIMENSIONAL ELECTROPHORESIS - GENETIC-VARIABILITY AS RELATED TO ABUNDANCE AND SOLUBILITY IN 2 MAIZE LINES

Relative abundance and solubility of proteins from etiolated coleoptil es of maize were investigated using two-dimensional electrophoresis (2 -D PAGE). Automatic quantification of silver-stained polypeptides on r eplicate 2-D gels made it possible to test the linearity of the relati onship between spot integrated optical density and protein amount in t he range from 15 mu g to 135 mu g per gel, in two inbred lines. A line ar response was found for more than 60% of the spots in each genotype. When a linear response was found in both lines for a given spot, the slope values were similar in 94% of the cases, indicating the reliabil ity of silver staining for polypeptide quantification. The parameters of the curves allowed the definition of protein classes of different a bundances that could be compared for genetic variability between the t wo lines. From a comparison between standard 2-D patterns (trichloroac etic acid-acetone extracted proteins) and patterns obtained from Tris buffer extracted proteins, it appeared that 92% of the proteins visual ized in the standard gels were soluble. No difference in genetic varia bility, either qualitative or quantitative, was evidenced between the various classes of abundance, or between soluble and insoluble protein s.