Apparent Differences in the Posttranslational Modification of Peroxidase between Flax Genotrophs and Genotypes and between Normal and Stress- Induced Isozymes

Abstract

Estimates of relative net charge and apparent molecular weight were obtained, using Ferguson plots, for each of the peroxidase isozymes in four completely inbred flax (Linum usitatissimum) plant types. The six anionic and the three cationic isozymes that are normally seen in various seedling tissues were examined. Four anionic isozymes that are seen in stressed seedlings were also included in the study. Charge and molecular weight comparisons detected plant-type differences that apparently resulted from two different forms of posttranslational modification. Plant-type differences in molecular weight for the normal anionic and cationic isozymes were attributable to differences in the degree of glycosylation. However, all of the normal anionic isozymes of one plant type had lower net negative charges than the corresponding isozymes of the other plant types. Therefore, both glycosylation and a second form of common modification, which affects charge but not molecular weight, determine the final structure of these isozymes The stress-induced isozymes did not display the plant-type differences seen in the normal isozymes and, based on charge and weight, none of the induced isozymes appeared to relate to any of the normal isozymes Some stress-induced isozymes seemed to be present in some plant types but not in others. Isozyme interactions that can cause this appearance are described and discussed.