Evaluation of a catalase inhibitor in the developmental regulation of maize catalase

Abstract

A protein which has been shown to inhibit catalase in vitro appears to vary inversely with catalase activity in the maize scutellum during early sporophytic development when assayed using a catalase inhibition assay. This result suggested that the inhibitor protein may play a direct role in regulating catalase activity during this time period. Four experimental approaches were used to evaluate this putative regulatory role, including immunological quantitation of individual catalase isozymes during germination using rocket immunoelectrophoresis, perturbation of normal catalase expression with hydrogen peroxide or allylisopropylacetamide (AIA), examination of a mutant line with an altered catalase developmental program, and direct radioimmunoassay of the inhibitor protein during germination. The results of these experiments indicate that the quantitative changes in catalase activity during development are not mainly due to changes in the expression of the catalase inhibitor. Other possible roles of this protein in catalase regulation are discussed.

Expression of genetically distinct superoxide dismutases in the maize seedling during development

“…The cytosolic and mitochondrial superoxide dismutases exhibit slightly different developmental time courses in the scutellum during the period following seed imbibition ( Fig.2), neither of which resembles the developmental time courses of catalase and peroxidase activity in this tissue. Catalase activity rapidly increases following seed imbibition and is highest at approximately day-4 postimbibition after which it declines [10,24]. Although barely detectable in 24-hour soaked seeds, peroxidase activity in the scutellum increases rapidly following seed imbibition and maintains a high level of activity during early sporophytic development [l].…”

Developmental Genetics of Maize

“…The galactose associated with this protein is necessary for the inhibitory activity (115). The fact that the glycoprotein is associated with glyoxysomal membranes has led to the hypothesis that the inhibitor may also serve as a binding protein to facilitate catalase compartmentation within glyoxysomes (116). In addition, genetic analysis of catalase-inhibitor variants suggests that the inhibitor protein is encoded in a distinct structural gene, independent of the catalase structural genes (unpublished data, this laboratory).…”

Spatial pattern of catalase (Cat2) gene activation in scutella during postgerminative development in maize.

“…The developmental time course for catalase shows a relatively low level of activity in the scutellum during seed imbibition, followed by a significant increase after germination. A peak in activity occurs at 4-5 days of postgerminative development and is followed by a decline (6,7). Zymogram analysis during the same developmental period indicates that there are definite pattern shifts in catalase isozymes.…”

“…The increase in catalase activity 2 days after germination is due to the increased rate of synthesis and accumulation of the CAT-2 isozyme while the CAT-1 isozyme is rapidly eliminated (8). The relative changes in level of crossreactive material (using CAT-1-and CAT-2-specific antibodies) at each developmental stage parallel the changes in total catalase activity (7). An inbred line, A16, exhibiting a null phenotype for CAT-2 protein has also been described (9).…”