Light and Fusicoccin as Tools for Discriminating Among Responses of Cotyledons to Cytokinins

Longo, Claudio P.; Longo, Giovanna P.; Lampugnani, Maria Grazia; Rossi, G.; Servettaz, Orietta

doi:10.1007/978-3-642-68035-9_24

Cited by 9 publications

(5 citation statements)

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“…The activity of hydroxypyruvate reductase prepared from purified cotyledonous microbodies and analyzed by native gel electrophoresis is proportionally enhanced by sequentially higher concentrations (10' to 101 molar) of benzyladenine. (9,11,12), water uptake (14), increase in fresh weight, and the development of cell organelles (7,12). This wide range of responses is accompanied by an increment ofDNA synthesis (8), induction ofproteins, or enzymes synthesis (9,12).…”

Section: Introductionmentioning

confidence: 99%

“…(9,11,12), water uptake (14), increase in fresh weight, and the development of cell organelles (7,12). This wide range of responses is accompanied by an increment ofDNA synthesis (8), induction ofproteins, or enzymes synthesis (9,12). One of the enzyme activities significantly stimulated by the hormone is HPR2 (12).…”

Section: Introductionmentioning

confidence: 99%

“…This wide range of responses is accompanied by an increment ofDNA synthesis (8), induction ofproteins, or enzymes synthesis (9,12). One of the enzyme activities significantly stimulated by the hormone is HPR2 (12). This enzyme catalyzes the conversion ofhydroxypyruvate to glycerate in microbodies, and is involved in the glycolate pathway (16).…”

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confidence: 99%

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Cytokinin-Modulated Gene Expression in Excised Pumpkin Cotyledons

Chen

Leisner²

1985

Plant Physiol.

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Comparison of two-dimensional polyacrylamide gel electrophoretic maps of proteins isolated from benzyladenine-treated and untreated pumpkin (Cucurbita pepo L. cv Halloween) cotyledons showed that the expression of certain proteins is enhanced, induced, or suppressed by the cytokinin treatment. The amount of poly(A)' mRNA isolated from cotyledons incubated with 10' molar benzyladenine for five days was about four-fold over the water-incubated control. The activity of hydroxypyruvate reductase prepared from purified cotyledonous microbodies and analyzed by native gel electrophoresis is proportionally enhanced by sequentially higher concentrations (10' to 101 molar) of benzyladenine. (9,11,12), water uptake (14), increase in fresh weight, and the development of cell organelles (7,12). This wide range of responses is accompanied by an increment ofDNA synthesis (8), induction ofproteins, or enzymes synthesis (9,12). One of the enzyme activities significantly stimulated by the hormone is HPR2 (12). This enzyme catalyzes the conversion ofhydroxypyruvate to glycerate in microbodies, and is involved in the glycolate pathway (16).Despite an abundance of knowledge about the physiological responses of cotyledons to cytokinin treatment, there is no concrete information on the questions of (a) whether the effects of cytokinin on gene expression are exerted by induction, stimulation, and/or suppression of specific protein syntheses, and (b) if the influence of cytokinin on protein or enzyme synthesis is primarily at the pretranslational or posttranslational level.In the present study, we have utilized two-dimensional PAGE to determine if cytokinin modifies the spectrum of polypeptides synthesized during cytokinin-induced cell expansion ofpumpkin cotyledons. We Cotyledon Preparation. Pumpkin seeds of approximately the same size were imbibed for 16 h with running tap water, and surface sterilized for 10 min with 0.5% NaOCl. The seeds were thoroughly rinsed with sterile distilled H20 and were sown on distilled H20-moistened Whatman No. 1 filter papers contained in Petri dishes under aseptic conditions. These Petri dishes were placed in darkness at room temperature (25°C) for 7 d. Cotyledons were then excised and cultured under aseptic conditions for various times in the dark on filter papers in Petri dishes. The dishes contained 10 ml distilled H20, 0.2 mg/ml penicillin G, with or without BA.Preparation of Microbody HPR. The preparation of pumpkin cotyledon microbodies was adapted from a method for spinach microbody preparation described by Huang et al. (10) and modified by Chang and Huang (3) with the exception that the homogenate was filtered through three layers of cheesecloth instead of Nitex cloth. The microbodies were purified by a 30 to 60% (w/v) linear sucrose gradient. Sucrose gradient-purified microbodies were dialyzed against 10 mm Tris-HCI (pH 7.5) overnight to release proteins from microbodies. The dialysate was centrifuged at 100,000g for 1 h, and the supernatant protein solution containing HPR was reduce...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Cytokinin-Modulated Gene Expression in Excised Pumpkin Cotyledons

Chen

Leisner²

1985

Plant Physiol.

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“…It was first reported by Ikuma and Thimann (1963) that the action of cytokinins in causing expansion of lettuce cotyledon during germination. The similar effects have been found on excised cotyledons of other plants, including mustard (Lovell and Moor 1970), watermelon (Longo et al 1981) and cucumber (Narain and Laloraya 1974). The role of cytokinin-induced cotyledon expansion has been studied by a number of groups.…”

Section: Introductionmentioning

confidence: 62%

Effects of benzylaminopurine and irradiance on cytokinin contents, α-tubulin gene expression and cucumber cotyledon expansion

Li¹,

H.²

2007

Biologia plant.

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The fluctuation of endogenous cytokinins was determined in the excised cucumber (Cucumis sativa L.) cotyledons incubated with benzylaminopurine (BA) under irradiance or in darkness. The data indicated that light stimulated the cotyledon expansion compared with dark and BA further enhanced the expansion of cotyledons. However, only BA treatment markedly increased the contents of endogenous cytokinins and induced α-tubulin gene expression. Actinomycin D, a well-known inhibitor of gene transcription, strongly inhibited both light-and BA-induced cotyledon expansions and increase of endogenous cytokinin contents and α-tubulin gene expression. Colchicine, an antimicrotubular reagent, partially inhibited the cotyledon expansion without affecting the cytokinin contents.

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“…Cytokinins regulate the levels of various enzymes (Chen et al 1993), and one of the enzymes significantly enhanced by the hormone is hydroxypyruvate reductase (HPR) (Longo et al 1981;Chen and Leisner 1985) which catalyzes the conversion of hydroxypyruvate to glycerate with the oxidation of NADH. Transcripts for HPR are present in cotyledons and leaves but have not been detected in roots (Greenler et al 1990).…”

Section: Introductionmentioning

confidence: 99%

Transcriptional regulation of hydroxypyruvate reductase gene expression by cytokinin in etiolated pumpkin cotyledons

Andersen

Jin

Chen

et al. 1996

Planta

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To understand the mechanisms by which the expression of a specific gene is modulated by cytokinin, the regulation of hydroxypyruvate reductase (HPR) transcript levels by N6-benzyladenine (BA) in etiolated pumpkin (Cucurbita pepo L. cv. Halloween) cotyledons was investigated. A pumpkin HPR cDNA was generated by reverse transcriptase-polymerase chain reaction and its nucleotide sequence was determined. An antisense HPR RNA was prepared for RNase protection analysis of HPR-mRNA expression patterns in the cotyledons of dark-grown pumpkin seedlings. Treatment of the cotyledons with BA was shown to modulate HPR mRNA levels in a dose- and time-dependent manner. Similarly, nuclear run-on studies showed that the rate of transcription was also enhanced by BA treatment of the cotyledons. These results suggest that the enhancement of HPR mRNA by cytokinin is, at least in part, at the level of transcription.

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Light and Fusicoccin as Tools for Discriminating Among Responses of Cotyledons to Cytokinins

Cited by 9 publications

References 10 publications

Cytokinin-Modulated Gene Expression in Excised Pumpkin Cotyledons

Cytokinin-Modulated Gene Expression in Excised Pumpkin Cotyledons

Effects of benzylaminopurine and irradiance on cytokinin contents, α-tubulin gene expression and cucumber cotyledon expansion

Transcriptional regulation of hydroxypyruvate reductase gene expression by cytokinin in etiolated pumpkin cotyledons

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