Non-Coordinate Genetic Alterations in the Expression of Catalase and other Glyoxysomal Enzymes during Maize Development

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Abstract
In the scutellum of maize during post-germinative development, the primary form of catalase expressed is the product of the Cat2 structural gene, CAT-2. The developmental time-course of CAT-2 protein follows a rapid increase with a peak at approximately 4–5 d alter germination and a subsequent decline. An inbred strain of maize, A337, has been found to exhibit a similar generalized profile with the significant exception that the level of CAT-2 protein present in the scutellum is far above that in the ‘typical’ maize lines exemplified by W64A. Our data suggest that the higher levels of CAT-2 exhibited in A337 are due to increased synthesis and accumulation of more CAT-2 protein, and not merely to enzyme activation. A comparison of A337 and W64A showed that the two lines are similar with respect to number of glyoxysomes and with the exception of catalase, other microbody associated enzymes exhibit similar activity levels and developmental profiles. Thus, the results presented suggest that the catalasc developmental programme characteristic of line A337 is not due to a concurrent increase and subsequent decline in the number of glyoxysomes formed in the scutellum during this developmental period but is instead due to a greater level of CAT-2 protein. The data further support our earlier findings that the genes coding for glyoxysomal enzymes in maize are non-coordinately regulated.