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.