Differential gene expression patterns in the autogamous plant Hordeum euclaston (Poaceae).

Sib-seedlings of 95 strains of the strictly autogamous grass Hordeum euclaston were analyzed by horizontal polyacrylamide gel electrophoresis for four isoenzyme systems at a specific ontogenetic stage. We found differences in the activity of some genes among individuals of this species. Hence, an ontogenetic analysis was carried out to investigate 12 strains at five ontogenetic stages, to determine the patterns of expression of these genes during development. The differences in the presence versus absence of certain isoenzyme bands may be due to differential regulatory activation in response to environmental differences, as all plants showed the same structural genes, although these genes were active in different tissues and/or times of development. These results indicate the importance of differential gene activation in the metabolic phenotype variability of this strictly autogamous, highly homozygous species. The same structural alleles for isoenzymes showed the active form of the enzymes (phenotypic expression) to be present in different tissues and/or stages of development. Differential isoenzyme gene activation was shown to be directly responsible for the enzymatic variability (metabolic phenotype) presented by the plants, which seem to possess almost no heterozygosis.

Structural and regulatory differences in amylase isoenzymes ingerminating Brazilian barley cultivars

The amylase electrophoretic patterns of 10 Brazilian brewing-barley varieties with different malting grades and diastatic power were analyzed during the 7-day germination which occurs during the malting process. Intra and inter-variety genetic variability was observed at both the structural and regulatory level. In the first few days after germination all varieties showed a few active loci, all of them with low activity. In subsequent days, new loci became active and those already detected since early germination showed increased activity. All varieties showed a continuous increase in amylase synthesis until the 3rd and/or 4th day after germination. Some varieties maintained high amylase activity until the last day of germination, while others showed a decrease in activity on the 5th or 6th day. No specific band increased or decreased its intensity independently of the others. A total of 14 loci were detected, out of which only one locus was polymorphic, indicating very low structural genetic variability, with only 2.8 per cent polymorphic loci, an average of 1.04 alleles per loci, and an average expected heterozygosity of only 0.7 per cent. The mean intra-variety Jaccard similarity coefficient complement (1 - Sj) was 0.009. The mean intra-variety difference based on regulatory differences was higher (1 - Sj = 0.17) than that obtained based on structural differences, suggesting differential gene activation. Inter-variety differentiation also showed low structural variability, with 1 - Sj = 0.026 and a Nei genetic distance (D) value of 0.0076, and a remarkable increase in divergence caused by differential gene activation (1 - Sj = 0.34). These results indicate that regulatory polymorphism is the principal agent responsible for amylase variability in the barley varieties analyzed