Petunia

Genetical control and linkage relationships of isozyme markers in sugar beet (B. vulgaris L.) : 1. Isocitrate dehydrogenase, adenylate kinase, phosphoglucomutase, glucose phosphate isomerase and cathodal peroxidase

Five isozyme systems were genetically investigated. The different separation techniques, the developmental expression and the use as marker system in sugar beet genetics and breeding is discussed. Isocitrate dehydrogenase was controlled by two genes. The gene products form inter- as well as intralocus dimers, even with the gene products of the Icd gene in B. procumbens and B. patellaris. Adenylate kinase was controlled by one gene. Three different allelic forms were detected, which were active as monomeric proteins. Glucose phosphate isomerase showed two zones of activity. One zone was polymorphic. Three allelic variants, active as dimers, were found. Phosphoglucomutase also showed two major zones of activity. One zone was polymorphic and coded for monomeric enzymes. Two allelic forms were found in the accessions studied. The cathodal peroxidase system was controlled by two independent genes, of which only one was polymorphic. The gene products are active as monomers. Linkage was found between red hypocotyl color (R) and Icd 2. Pgm 1, Gpi 2, Ak 1 and the Icd 2-R linkage group segregated independently.

Cellular location of peroxidase isoenzymes in leaf tissue of Petunia and their affinity for Concanavalin A-Sepharose

The cellular location of three peroxidase isoenzymes (PRX) in mature leaf tissue of Petunia and their affinity for Concanavalin A-Sepharose were investigated. The isoenzymes PRXa, PRXb and PRXc were identified by their positions in starch-gel zymograms. The fast-moving anodic and cathodic peroxidase bands, the isoenzymes PRXa and PRXc respectively, were the most active peroxidases in extracellular extracts. The molecular forms of PRXa showed a tissue-specific distribution between midrib and remaining leaf tissue. An intermediate-moving anodic peroxidase band, the isoenzyme PRXb, was the most active peroxidase released after extraction of isolated mesophyll protoplasts. Small amounts of the peroxidase isoenzymes were present in cell-wall-bound fractions. Incubation of a crude protein fraction with Concanavalin A-Sepharose showed that the isoenzyme PRXb bound more firmly to Concanavalin A-Sepharose than the isoenzymes PRXa and PRXc, of which only one molecular form bound partly. The results are discussed with respect to a possible function of one of the peroxidase isoenzymes, and a possible role of oligosaccharide chains in determining the cellular location of plant peroxidases is suggested.

Genetics of the peroxidase isoenzymes in Petunia : 8. Flower and root peroxidases

In root and flower corolla tissue of Petunia several anodic moving peroxidase isoenzymes are present, which cannot be detected in other organs. Alleles of the gene prxF control the presence or absence of several peroxidases that are only present in flower corolla tissue. Alleles of the gene prxG code for two peroxidases that can only be detected in root tissue. In addition to mutations of prxG that cause a change in the electrophoretic mobility of the PRXg enzymes, a mutation was also found that causes the absence of expression in enzyme activity. Crossing experiments indicated that this mutation is located in the gene prxG. Peroxidases encoded by the gene prxH were only found in root tissue. Two alleles of prxH were identified by electrophoretic variation; one allele is responsible for a single band, whereas the other allele could be recognized by a double-banded phenotype. The double-banded PRXh phenotype is suggested to be caused by tandem duplication, followed by mutation in one of the genes. A third prxH allele could be identified by the absence of PRXh activity. The genes prxF, prxG, and prxH were shown to be located on chromosome VII, with the following gene order: prxG-An4-lapB-gpiB-prxH-prxF.