Isoenzymes and polyploidy. I. qualitative and quantitative isoenzyme studies in the Triticinae

Abstract

Enzymes of alcohol (ADH), malate (MDH), glutamate (GDH) and isocitrate (IDH) dehydrogenases, and a fast migrating esterase (EST-l) were separated by disk electrophoresis from dry seed extracts of diploid, tetraploid, hexaploid and octaploid species or amphiploids belonging to the subtribe Triticinae. Only ADH and EST-l isoenzymes showed inter-species variation; the other dehydrogenases, which show stringent substrate specificities ('critical' enzymes), revealed the same pattern in all diploid and polyploid species. The qualitative zymogram studies showed that (1) the number of variant enzyme bands increased with the level of ploidy, (2) the amphiploid isoenzyme pattern was additive of the parental species, (3) enhancement in the number of bands was due to the presence of not only parental bands, but also hybrid bands formed by association between heteromonomers. Quantitative data were obtained by densitometry of the enzyme bands as well as spectrophotometric measurements of enzyme activity in crude extracts. Increase in the level of enzyme activity was observed with ploidy level. In spite of the evidence that all duplicate/triplicate genes are expressed, increased enzyme activity observed in the polyploid species was not proportional to the level of ploidy or expected gene dosage. On the basis of ADH and EST-l zymograms obtained in 2 × and 4 × wheat, probable zymograms for these enzymes in the B-genome donor to 4 × wheat were extrapolated. Neither Ae. speltoides nor Ae. bicornis showed the extrapolated ADH pattern. Amphiploids involving Ae. speltoides and Triticum monococcum or T. aegilopoides fully reproduced the EST-l zymogram of 4 × wheat, but not the ADH. Ae. bicornis × T. aegilopoides amphiploid showed an ADH zymogram similar to that of 4 × wheat, but the EST-l bands were different.