Distinguishing allozymes and isozymes of phosphoglucoisomerases by electrophoretic comparisons of pollen and somatic tissues

The different electrophoretic patterns of dimeric phosphoglucoisomerases extracted from haploid pollen and diploid somatic tissues of plants may be used to distinguish allozymes and isozymes. The analysis depends on the presence of two alleles at each locus in somatic tissues but only one or the other allele in pollen grains. Consequently, in heterozygotes, heterodimeric allozymes can be identified because they are formed in stems and leaves but not in pollen. The procedure is described in enzymes extracted from the diploid annual plant Clarkia dudleyana, which possesses three gene loci for PGI subunits. Comparison of the electrophoretic patterns of stem and pollen extracts makes it possible in many cases to identify allelic state without breeding tests. The technique also is likely to be useful in the interpretation of zymograms of other multimeric enzymes coded by more than one gene locus.