Dissociation-recombination of intergenic sunflower alcohol dehydrogenase isozymes and relative isozyme activities

Abstract

Two unlinked genes, Adh1 and Adh2, control of the production of alcohol dehydrogenase (ADH) in seeds of the animal sunflower (Helianthus annuus). Each gene is polymorphic, having F and S alleles. Starch gel electrophoretic zymograms of the four possible double homozygotes have three bands, representing two homodimers and an intermediately migrating intergenic isozyme. Zymograms of double heterozygotes consist of nine bands produced by ten isozymes: six intragenics and four intergenics, two of which are coincident. Results of dissociation-recombination (D-R) experiments are reported which demonstrate the subunit composition of the intergenic isozymes, thus supporting the relationships suggested by genetic studies. Densitometric tracings of the zymogram of a cleared gel and measurements of activities of homodimer isozymes eluted from gels follwoing D-R of an intergenic isozyme showed that the Adh2 isozymes were more that twice as active as those of Adh1. Measurements of activities of crude extracts from the four possible double homozygous genotypes indicated that the seeds of the genotype Adh1F/Adh2F, Adh2S/Adh2S produced more activity than the other three. This genotype is the most common one found in wild and cultivated stocks. Isozymes eluted following electrophoresis of the same extracts had averages of 19%, 70%, and 11% of total activity contributed by the Adh1, Adh2, and intergeneic isozymes, respectively. A simple but efficient method of isozyme elution from starch gels is described which resulted in nearly full expected recovery (approximately 46%) of the ADH activity in the applied sample.