Gene expression and development : the third of five volumes constituting the proceedings of the 4th International Congress on Isozymes, held in Austin, Texas, June 14-19, 1982 / editors, Mario C. Rattazzi, John G. Scandalios, Gregory S. Whitt.
- International Congress on Isozymes
- Date:
- [cl983]
Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)
Credit: Gene expression and development : the third of five volumes constituting the proceedings of the 4th International Congress on Isozymes, held in Austin, Texas, June 14-19, 1982 / editors, Mario C. Rattazzi, John G. Scandalios, Gregory S. Whitt. Source: Wellcome Collection.
41/256 page 21
![Gene Regulation During Development / 21 protein which apparently anchors mouse ß-glucuronidase to microsomal membranes [Lusis and Paigen, 1977]. These findings are not only interesting in and of themselves, but may lead to the uncovering of a class of unique DNA sequences (topogenes) which specify the topology of structural gene products within eukaryotic cells. IV. TEMPORAL REGULATION OF GENE EXPRESSION Proteins and other macromolecules provide a sensitive index for moni¬ toring the pattern of developmental expression of the encoding genes and in elucidating the underlying regulatory mechanisms responsible for differential gene expression in eukaryotes. A prerequisite for such studies is the under¬ standing of the developmental program of a given enzyme. Such a program can be defined experimentally by measuring the enzyme's activity in each tissue as development progresses, and describing this activity as a function of space and time. Once the program for a given enzyme has been defined, it becomes possible to 1) screen for mutants in which the program is altered, 2) to use such mutants to analyze the mechanisms that effect differentiation, and 3) to determine whether the structure of the enzyme and its developmental program are specified by the same or separate DNA sequences. A. Genetic Regulation of the Catalase Developmental Program The catalase gene-enzyme system of maize has proven to be an interesting one for studying gene expression in a higher eukaryote since the isozymes appear to be regulated by a number of mechanisms during early sporophytic development including the differential turnover of the Catl and Cat2 gene products [Quail and Scandalios, 1971] and regulation by an endogenous inhibitor [Tsaftaris et al, 1980]. Catalase activity in the maize scutellum surges to a peak at approximately four days after soaking the kernels in distilled water for 24 hours and germinating them on moistened germination paper. The time course of activity (Fig. 14) reflects the differential expression of the CAT-1 and CAT-2 isozymes, both of which are found in the scutellum at this stage of development. CAT-1 activity gradually disappears, while CAT-2 activity increases rapidly during the days following seed imbibition. These changes in activity are largely, if not entirely, due to changes in the levels of catalase protein caused by varying rates of synthesis and degradation [Quail and Scandalios, 1971]. Following a screening program, we have uncovered a number of lines that express altered developmental programs for catalase in the scutellum. In line R6-67, catalase activity in the scutellum increases rapidly following germination and maintains a level at least twice that observed in the standard inbred W64A [Fig. 15]. Using rocket Immunoelectrophoresis to quantitate](https://iiif.wellcomecollection.org/image/b18019742_0042.JP2/full/800%2C/0/default.jpg)
