Expression of the developmentally regulated catalase (cat) genes in maize

Abstract

The catalase (H2O2:H2O2 oxidoreductase; E.C.1.11.1.6; CAT) gene‐enzyme system in Zea mays L (maize) represents an ideal model for studying the molecular basis of developmental gene regulation in higher eukaryotes. This system comprises a family of structural genes that are highly regulated, both temporally and spatially, during maize development. In maize, there are four distinct forms (isozymes) of catalase that are readily discernible by convetional separation procedures. Three of the catalases have been studied in detail from a genetic and biochemical viewpoint. The catalases CAT‐1, CAT‐2, and CAT‐3 are encoded by the distinct, unlinked genes Cat1, Cat2, and Cat3, respectively. Each of the structural genes is highly regulated both spatially and temporally in its expression. Cat1 is expressed primarily in the endosperm, aleurone, pericarp, and scutellum of developing kernels, and in the root, shoot, and scutellum of very young seedlings. Cat2 is expressed primarily in the scutellum and leaf during postgerminative sporophytic development. Cat3 is expressed, for the most part, in the shoot and pericarp of young seedlings. A number of regulatory variants have been recovered that affect the developmental program of expression of the catalases. Analysis of one variant allowed for the identification of a temporal regulatory gene (Car1) that specifically alters the developmental program of the Cat2 structural gene by acting to regulate the rate of CAT‐2 protein synthesis. Cat1 has been mapped on chromosome 1S, 37 map units (m.u.) from the Cat2 structural gene. Another variant line has been isolated which lacks expression of the Cat2 gene in its tissues at all stages of development. Isolated polysomes from this line (A16) were translated in vitro, and the products were immunoprecipitated with CAT‐2‐specific antibodies. No CAT‐2 was detectable in the A16 labeled immunoprecipitates, whereas CAT‐2 was readily detected in the normal line, W64A, under similar conditions. The temporal and spatial expression of the Cat structural genes is not only influenced by genetic factors (as above), but is also responsive to exogenously applied environmental signals: light, hormones, and temperature. The mechanisms by which such signals specifically affect CAT‐2 expression will be discussed.

Enhanced-Peroxidatic Activity in Specific Catalase Isozymes of Tobacco, Barley, and Maize

“…However, the enzymes from microorganisms can utilize o-dianisidine in the peroxidatic reaction (10) whereas EP-CAT from tobacco cannot (our unpublished data). In maize, EP-CAT is the product of the Cat3 gene (14,15). In other plant species such as tobacco (4,5) and barley the evidence for separate genetic control is indirect.…”

“…It has been well documented in maize that CAT-2 and CAT-3 are cell specific, i.e. CAT-2 (T-CAT) is located in the bundle sheath cells and CAT-3 (EP-CAT) in the mesophyll cells (15,19). Mesophyll cells contain few peroxisomes and an association of catalase with isolated mitochondria and submitochondrial particles led to the suggestion that catalase was located in the mitochondria (14).…”

The in Vivo and in Vitro Inhibition of Catalase from Leaves of Nicotiana sylvestris by 3-Amino-1,2,4-Triazole

“…533 been reported by Chandlee et al (1) for the three partially purified maize catalases that are coded for by separate genes (23). One form of catalase, CAT-3, was less sensitive to aminotriazole than the others.…”

Biochemical and Developmental Characterization of Multiple Forms of Catalase in Tobacco Leaves

“…Maize represents the only plant system in which three genetically distinct catalase proteins have been purified to homogeneity and characterized biochemically (23). Two forms displaying cell-type specificity in the leaf (27) were shown to be antigenically distinct, and exhibited differences in thermal stability and sensitivity to various inhibitors (4).…”