Induction of Cytokinin-Independent Tobacco Tissues by Substituted Fluorenes

Bednar, Thomas W.; Linsmaier-Bednar, Elfriede M.

doi:10.1073/pnas.68.6.1178

Cited by 27 publications

(6 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Under certain conditions (Bednar and Linsmaier-Bednar, 1971;Syono and Fujita, 1994) or after prolonged periods of time in culture, some callus acquires the capability to grow in the absence of auxin and/or eytokinin. They become habituated (Gautheret, 1942;Meins, 1989).…”

Section: Introductionmentioning

confidence: 99%

DNA methylation as a key process in regulation of organogenic totipotency and plant neoplastic progression?

Lambé¹,

Mutambel²,

Fouché³

et al. 1997

In Vitro Cell.Dev.Biol.-Plant

View full text Add to dashboard Cite

Progressive loss of organogenic totipotency appears to be a common event in long-term plant tissue eultme. This loss of totipotency, which has been proposed to be a typical trait of plant neoplastic progression, is compared to some mechanisms thai occur during the establishment of animal differentiation-resistant cancer lines in ~itro. Evidence is presented that alteration in DNA methylation patterns and expression of genes occur during long-term callus culture. An effect of the auxin, 2,4-dichlorophenoxyacetic acid, in the progressive methylation, is moreover suggested. Methylation of genes relevant to cell differentiation and progressive elimination of ceils capable of differentiation is proposed as being responsible for this progressive loss of organogenic potential. Finally, the epigenetie alteration (DNA methylation) that occurs during prolonged periods of culture may induce other irreversible genetic alterations that uhimately make the loss of totipotency irreversible.

show abstract

Section: Introductionmentioning

confidence: 99%

DNA methylation as a key process in regulation of organogenic totipotency and plant neoplastic progression?

Lambé¹,

Mutambel²,

Fouché³

et al. 1997

In Vitro Cell.Dev.Biol.-Plant

View full text Add to dashboard Cite

show abstract

“…Using the Oncotest [2] for the screening of carcinogenic compounds, we have shown that carcinogens strongly stimulate in vitro cancer DNA synthesis, but only slightly stim ulate normal DNA synthesis. Low concentra tions of carcinogens can also stimulate the multiplication of cancer cells in animals [1,3] and plants [5,20]. On the other hand, it has been reported that actinomycin D [21] and tumor-promoting agents such as phorbol derivatives induce terminal differentiation in promyclocytic leukemia cells [18,21] when used at very low concentrations.…”

Section: Introductionmentioning

confidence: 99%

“…In order to account for enhanced in vitro cancer DNA synthesis [2] and accelerated multiplication of vegetable [5,20] and mam malian [1. 3, 21] cancer cells in the presence of carcinogens, anticancer drugs or various other compounds such as DMSO, croton oil and steroids, we attempted to establish possi ble correlations between in vitro cancer DNA synthesis, in vivo cancer cell multiplication and in vitro DNA strand separation cata lyzed by the above compounds.…”

Section: Introductionmentioning

confidence: 99%

Correlation between in vitro DNA Synthesis, DNA Strand Separation and in vivo Multiplication of Cancer Cells

Beljanski¹,

Bourgarel²,

Beljanski³

1981

Pathobiology

View full text Add to dashboard Cite

The chemicals 9,10-dimethylbenzanthracene (DMBA), ethionine, daunorubicin, actinomycin D, l-(2-chloroethyl-1)-nitrosourea (CCNU), steroids, croton oil and dimethylsulfoxide (DMSO) were used in order to correlate their effect on the in vitro synthesis of normal and cancer DNA, on DNA strand separation and on accelerated in vivo multiplication of cancer cells. All of the compounds tested strongly stimulate the synthesis of cancer DNA in vitro catalyzed by DNA-dependent DNA polymerase I and measured as an acid-precipitable labeled product. Under the same conditions, the synthesis of DNA originating from healthy tissues is only slightly enhanced, except in the case of croton oil and DMSO. These substances are almost equally active on cancer and normal DNA. Although both cancer and normal DNA contain a large amount of double-stranded regions, the extent of DNA strand separation measured by the increase in UV absorbance (hyperchromicity) in the presence of each compound tested is much higher for all cancer DNA than for corresponding normal DNA. In contrast, DMSO and croton oil do not appear to distinguish cancer DNA from normal DNA. Additive and differential effects of various compounds on cancer DNA strand separation can be observed. Small doses of DMBA and CCNU stimulate the multiplication of Ehrlich ascites tumor cells in vivo in mice. There is thus a possible correlation between DNA strand separation, DNA synthesis, multiplication and differentiation of cancer cells in the presence of the above compunds, which is different from the response of normal cells to these compounds.

show abstract

“…The induction of nitrate reductase was blocked by cycloheximide, puromycin, and actinomycin D in the presence of any one of the inducing agents (Table 1). DISCUSSION Autonomous growth has been shown in tissues transformed by bacteria (22)(23)(24)(25)(26), viruses (27,28), chemicals (29)(30)(31), and genetic factors (32)(33)(34). The present investigation established that y-irradiation can also induce autonomous growth in Haworthia callus.…”

Section: Resultsmentioning

confidence: 99%

Gamma-irradiation activates biochemical systems: induction of nitrate reductase activity in plant callus.

Pandey¹,

Sabharwal²

1982

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

View full text Add to dashboard Cite

y-irradiation induced high levels of nitrate reductase activity (NADH:nitrate oxidoreductase, EC 1.6.6.1) in callus of Haworthia mirabilis Haworth. Subcultures of y-irradiated tissues showed autonomous growth on minimal medium. We were able to mimic the effects of v-irradiation by inducing nitrate reductase activity in unirradiated callus with exogenous auxin and Idnetin. These results revealed that induction of nitrate reductase activity by y-irradiation is mediated through in vitro activation of hormone synthesis in callus cells.Nitrate reductase (NADH: nitrate oxidoreductase, EC 1. 6.6. 1), a key enzyme in the nitrogen assimilatory.pathway, can be induced by substrate in higher plants (1-6) and in microorganisms (7). The activation of nitrate reductase has also been effected by kinetin in Agrostemma githago embryos (8-10) and tobacco leaves (11). Our previous investigation established that y-irradiation can activate synthesis of certain cell division factors in Haworthia mirabilis callus (12). Because nitrate reductase can be stimulated by kinetin (8-11) and because we have observed the presence of cell division factors in irradiated tissues, it was pertinent to investigate the induction of such enzyme in these callus tissues.Few other studies have been conducted on the effect of yirradiation on nitrate reductase activity in plants. In the fungus Ustilago maydis, the activity of nitrate reductase was increased after dosages of 100,000-400,000 rad (1 rad = 0.01 gray) (13). However, in blue-green algae 100,000 rad inhibited the activity ofnitrate reductase (14). Enzyme molecules are affected by both direct and indirect action radiation. Direct inactivation of enzymes requires high dosages, on the order of several megarad, whereas indirect inactivation generally requires only a few hundred thousand rad (15). Because Haworthia callus exposed to y-irradiation showed high levels of hormone production and induced nitrate reductase, it was postulated that the enzyme induction must be triggered by y-irradiation via the activation of hormone biosynthesis. .To support this postulate, experiments were carried out to study the induction of nitrate reductase in unirradiated tissues .by .exogenous supply of hormones in vitro. This report gives some insight on the mechanism of nitrate reductase induction in Haworthia mirabilis callus by yirradiation.MATERIALS AND METHODS Origin and Subculture of Callus Tissues. Young inflorescence explants were used to obtain the callus. The inflorescence axis was excised at its base, cut into segments, surface sterilized with 50% (vol/vol) Clorox for 5 min, and thoroughly washed with autoclaved double-distilled water. These segments 'were inoculated onto modified (16) Murashige and Skoog medium (17) supplemented with a-naphthaleneacetic acid (NAA) at 0.2 upg/liter and kinetin (N6-furfurylaminopurine) at 0.2 mg/liter.The callus that developed was maintained on a similar medium containing NAA. at 1.5 mg/liter and kinetin at 1.5 mg/liter; these concentrations of growth regulators were...

show abstract

Induction of Cytokinin-Independent Tobacco Tissues by Substituted Fluorenes

Cited by 27 publications

References 16 publications

DNA methylation as a key process in regulation of organogenic totipotency and plant neoplastic progression?

DNA methylation as a key process in regulation of organogenic totipotency and plant neoplastic progression?

Correlation between in vitro DNA Synthesis, DNA Strand Separation and in vivo Multiplication of Cancer Cells

Gamma-irradiation activates biochemical systems: induction of nitrate reductase activity in plant callus.

Contact Info

Product

Resources

About