Enzyme Induction in Higher Plants

Filner, Philip; Varner, Joseph E.; Wray, John L.

doi:10.1126/science.165.3891.358

Cited by 178 publications

(12 citation statements)

References 140 publications

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“…The concentration of each isozyme is, therefore, determined by both the rate of synthesis and the rate of degradation. This fits the general pattern observed for higher organisms (11,12). Protein turnover in higher organisms appears to be a general and continuous process and enzyme concentrations may be controlled by independent alterations in either the rate constants of degradation or of synthesis.…”

Section: Discussionsupporting

confidence: 56%

Turnover of Genetically Defined Catalase Isozymes in Maize

Quail

Scandalios

1971

Proc. Natl. Acad. Sci. U.S.A.

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The turnover of two homotetramers of catalase, V4 and Z4, specified by genes at two separate loci, has been studied during germination of maize seed by the techniques of density labeling and starch-gel electrophoresis. Both isozymes were shown to be turning over during this time. However, Z4 accumulates because the rate of synthesis exceeds the rate of degradation, whereas V4 slowly disappears because the rate of degradation exceeds the rate of synthesis. Evidence is also presented that the rate of synthesis of Z4 exceeds that of V4, which suggests that this may be a major factor in the differential expression of the two catalase genes.Maize catalase (H202:H202 oxidoreductase, EC 1.11.1.6) is a tetramer (1). The products of catalase genes at two distinct loci, Ct1 and Ct2, have been detected and shown to be inherited independently of each other (Scandalios, manuscript in preparation). When present together at the same stage of development, the two gene products (subunits) interact to form active tetramers. However, from the time of pollination to just prior to seed maturation, only the product of the Ct1 locus is present in the developing caryopsis of inbred lines homozygous at this locus. Thus, only one isozyme (the homotetramer) is active during this time. The product of the Ct2 locus is first detected in the dry seed and increases dramatically during the first 3 days of germination. The Ct1 gene product, on the other hand, slowly decreases in activity during germination and ultimately disappears. During the time that both classes of subunits are available, five species of active tetramers are detected-two homotetramers and three heterotetramers. Mich. 48823 V4. The polypeptide product of the Ct2 locus is tentatively designated subunit Z; the homotetramer is Z4. In this inbred line, the Z4 isozyme has a greater electrophoretic mobility than the V4 isozyme. MATERIALS AND METHODS Growth and extraction of seedlingsSeeds of maize, inbred line W64A, were germinated between moistened filter papers in Petri dishes in the dark at 240C.The papers were moistened either with 10 mM K'4NO3 in H20 (14N-H20) or with 10 mM (99 atom %) K15N03 in 70% D20 ('5N-D20). In the chase experiments, seeds were germinated for 36 hr in 15N-D20, rinsed for 20 min with several changes of water, and then placed in '4N-H20 for the chase period. Twenty scutella from each treatment were homogenized with sand in a mortar and pestle in 1 ml of 25 mM glycylglycine buffer (pH 7.4) and centrifuged at 20,000 X g for 10 min. The crude supernatant was used directly for electrophoresis. ElectrophoresisStarch-gel electrophoresis and staining for catalase were performed as described (2). For preparative purposes the entire extract from twenty scutella was applied to a single starch gel. After electrophoresis, a thin slice of the gel was stained to facilitate location of the V4 and Z4 isozymes. Strips corresponding to these two isozymes were cut from the remainder of the gel and centrifuged at 30,000 rpm for 30 min in an International B60 ultra...

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Section: Discussionsupporting

confidence: 56%

Turnover of Genetically Defined Catalase Isozymes in Maize

Quail

Scandalios

1971

Proc. Natl. Acad. Sci. U.S.A.

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“…7). The kinetics of recovery are suggestive of those for induction of enzyme synthesis or activation (Filner et al, 1969), and are very similar to those for light induced increase in specific activity of the DNA photoreactivating enzyme in dark grown, non-dividing cells of Euglena (Diamond et a/., 1975). In this system blue and near UV lights are effective in inducing enzyme activity (Diamond et al, 1975).…”

Section: Discussionsupporting

confidence: 55%

PHOTOREACTIVATION OF DNA‐CONTAINING CAULIFLOWER MOSAIC VIRUS AND TOBACCO MOSAIC VIRUS RNA ON DATURA

Towill¹,

Huang²,

Gordon³

1977

Photochem & Photobiology

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Abstract— Datura stramonium L. is a local lesion host for TMV‐RNA and DNA‐containing cauliflower mosaic virus (CAMV). Datura can photorepair UV‐damaged TMV‐RNA and CAMV, giving photoreac‐tivation sectors of 0.40 and 0.33, respectively. Dose response curves for photoreactivation of TMV‐RNA and CAMV show that 4540 min of cool white light (15 W.m‐2) is required for maximum photoreactivation. Blue light and near UV are equally effective in photoreactivating UV‐irradiated TMV‐RNA, whereas near UV is initially more effective than blue light for the photorepair of UV‐inactivated CAMV. Higher doses of near UV apparently inactivate the CAMV photorepair system. In the case of CAMV, photoreactivating light must be applied immediately after inoculation with the virus. Two to three hours of incubation in the dark after inoculation results in complete loss of response to photoreactivating irradiation. In contrast, limited photoreactivation of TMV‐RNA occurs even after 4 h of dark incubation after inoculation, although photoreactivating irradiation is most effective when applied immediately after inoculation. Light is required for the maintenance of photoreactivation for both TMV‐RNA and CAMV. Daturas placed in the dark for six days lose their ability to photoreacti‐vate. Recovery of the TMV‐RNA photorepair system is rapid; complete recovery attained with 90 or more min of white light (15 W m‐'). Recovery of CAMV photorepair system is slow; 90% recovery attained after only 20 h of light. However, full recovery can be induced by as little as 6h of light when CAMV is inoculated 24 h after the onset of illumination. These results suggest two photorepair systems are present in Datura.

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“…In the latter case changes in activity may arise through the influence of specific small molecules on a regulatory enzyme in the pathway or by protein synthesis, which would produce changes in the amount of enzyme present. Enzyme induction in higher plants has been reviewed by Filner et al (1969).…”

Section: -mentioning

confidence: 99%

Development of the activities of enzymes of the isoprenoid pathway during early stages of pea-seed germination

Green

Baisted

1972

Biochemical Journal

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The activities of individual enzymes of the isoprenoid pathway from mevalonate kinase to squalene synthetase in homogenates of seeds germinated up to 32h were assayed. Changes in the activity of each enzyme were observed and compared with the activity at the 2h germination stage. Activities of alkaline phosphatase and fructose 1,6-diphosphate aldolase were similarly measured to provide a reference for changes in the general metabolic activity of seeds during imbibition of water. Water uptake reached a plateau after 12h. The reference enzymes almost doubled in activity between 2 and 8h and thereafter their activities steadily declined. All of the enzymes of the isoprenoid pathway increased in activity between 2 and 6h and, thereafter, with the exception of the prenyltransferase, their activities remained relatively constant. With the prenyltransferase activity the initial increase was followed by a short plateau between 6 and 9h and then a second increase to a maximum between 14 and 16h. After 16h the activity declined. The relative activities of the isoprenoid enzymes at 16h of germination were mevalonate kinase>phosphomevalonate kinase>pyrophosphomevalonate decarboxylase approximately isopentenyl pyrophosphate isomerase>squalene synthetase>isopentenyl pyrophosphate/dimethylallyl pyrophosphate prenyltransferase. The finding that the prenyltransferase may be the rate-limiting enzyme in squalene synthesis from mevalonate is discussed in relation to regulation of isoprenoid synthesis during pea-seed germination.

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Enzyme Induction in Higher Plants

Cited by 178 publications

References 140 publications

Turnover of Genetically Defined Catalase Isozymes in Maize

Turnover of Genetically Defined Catalase Isozymes in Maize

PHOTOREACTIVATION OF DNA‐CONTAINING CAULIFLOWER MOSAIC VIRUS AND TOBACCO MOSAIC VIRUS RNA ON DATURA

Development of the activities of enzymes of the isoprenoid pathway during early stages of pea-seed germination

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