Comparison of the Growth Promoting Activities and Toxicities of Various Auxin Analogs on Cells Derived from Wild Type and a Nonrooting Mutant of Tobacco

Caboche, Michel; Müller, Jean-François; Chanut, Françoise; Aranda, G.; Cirakoglu, S.

doi:10.1104/pp.83.4.795

Cited by 30 publications

(17 citation statements)

References 20 publications

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“…Transmembrane potential measurements performed on the two genotype protoplasts showed a decreased ability of mutant protoplasts to respond to exogenously supplied auxin. This cellular characteristic of mutants is expected to be also expressed in tissues since mutant plantlets are more tolerant than wild-type plantlets to high auxin concentration (7). Thus, the mutation could disturb the biosynthesis of a possibly membrane-bound auxin receptor or could inactivate it.…”

Section: Iaa Levelsmentioning

confidence: 99%

Hormonal Characterization of a Nonrooting Naphthalene-Acetic Acid Tolerant Tobacco Mutant by an Immunoenzymic Method

Pelese¹,

Megnegneau²,

Sotta³

et al. 1989

Plant Physiol.

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The comparative analysis of plant hormones was undertaken on a 1-naphthaleneacetic acid tolerant mutant and normal tobacco (Nicotiana tabacum cv Xanthi) plantlets. The mutant plantlet was scrubby and impaired in its root morphogenesis. Degeneration of the root meristem was studied on tissue sections; it appeared very fast (as early as the 3rd or 4th day after sowing), after which the root was further transformed into a callus. Indoleacetic acid (IAA), abscisic acid (ABA), and the isopentenyladenine (iP)-and trans-zeatin(Z)-type cytokinin levels were measured in terminal buds and root tips 13 days after sowing, by enzyme linked immunosorbent assay of high performance liquid chromatography fractions. Some differences appeared between the apical buds of the two genotypes, but the mutant tobacco differed from the wild type mainly by the presence of higher levels of IAA, ABA, and iP + isopentenyladenosine (iPA) in its small root. Thus, the IAA, ABA, and iP + iPA contents were increased by a factor of 15, 7, and 24 times, respectively, in mutant root compared to wild-type tobacco roots. Previous work has shown that the mutation impairs membrane polarization effects induced by auxin at the cell level. The present results would favor the hypothesis that the mutation has also affected the control of growth regulator accumulation in tissues.Mutant plants, whatever their origin, can be used to obtain a better knowledge about plant physiology. During the last years, different monogenic mutants deficient in (or resistant to) plant growth substances were obtained: to ABA (14), to IAA (3), to gibberellins (15), and to cytokinins (2). Thus, the NAA' resistant tobacco mutant obtained by Muller et al. (23), which was characterized by its inability to root, provided a new tool to study the process of rhizogenesis.The aim of this work was to gain knowledge about the hormonal characteristics of the mutant as well as to describe the root degeneration. Therefore, using an immunoenzymic method (16,20, 25), we have quantified, in different tissues, the amounts of ABA, IAA, and cytokinins in tobacco seedlings, comparing the wild type with the 'rootless' mutant. We tested the hypothesis that the root degeneration, due to the ' Abbreviations: NAA, 1-naphthaleneacetic acid; ELISA, enzyme linkedimmunosorbent assay;iP, isopentenyladenine; iPA, isopentenyladenosine; Z, trans-zeatin; ZR, trans-zeatin riboside. mutation, was the result of a hormone deficit or an alteration in plant hormone metabolism. MATERIALS AND METHODS Plant MaterialWild-type tobacco (clone D8) and mutant tobacco (clone 36) seeds (Nicotiana tabacum cv Xanthi) were obtained from plants grown in greenhouses (INRA, Versailles, France). The NAA resistant dominant mutant tobacco was selected in vitro from mutagenized population of haploid mesophyll protoplasts (5, 23).The seeds were soaked for 20 min in 5% calcium hypochloride aqueous solution and then sown aseptically in glass pots (13 x 10 cm) containing a twice diluted, hormone-free, Murashige and Skoog agar medium (6 ...

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Section: Iaa Levelsmentioning

confidence: 99%

Hormonal Characterization of a Nonrooting Naphthalene-Acetic Acid Tolerant Tobacco Mutant by an Immunoenzymic Method

Pelese¹,

Megnegneau²,

Sotta³

et al. 1989

Plant Physiol.

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“…Recently, Korber et al (17) have demonstrated that the gene 5 product converts tryptophan into indole-3-lactate, which is an auxin antagonist. These authors suggested that the gene 5 product plays a role in fine tuning the auxin/cytokinin ratios in crown gall tissue. It is thus not inconceivable to propose that gene 5 expression would respond directly to auxins and cytokinins.…”

Section: Discussionmentioning

confidence: 99%

“…These authors suggested that the gene 5 product plays a role in fine tuning the auxin/cytokinin ratios in crown gall tissue. It is thus not inconceivable to propose that gene 5 expression would respond directly to auxins and cytokinins. However, we cannot exclude that some other natural compounds, which have no structural homologies with the classical auxins and cytokinins, also have activity in our bioassay.…”

Section: Discussionmentioning

confidence: 99%

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A New Bioassay for Auxins and Cytokinins

Boerjan¹,

Genetello²,

Montagu³

et al. 1992

Plant Physiol.

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The authors have developed a sensitive bioassay that can be used to detect auxins as well as cytokinins. The bioassay is based on the expression in transformed tobacco (Nicotiana tabacum) mesophyll protoplasts of a chimeric gene, consisting of the upstream sequences of the Agrobacterium tumefaciens gene 5, coupled to the coding sequence of the i6-glucuronidase. The expression of this gene is induced by the presence of both auxin and cytokinin in the culture medium. Using this assay, indole-3-acetic acid was detected at 5 x 10-' molar, whereas trans-zeatin could be detected at 5 x 101 molar. The assay can be performed in microtiter plates, allowing numerous samples to be analyzed simultaneously. Only 2.5 x 105 protoplasts are required for one individual assay in 250 microliters of culture medium and for qualitative results, the reaction is readily visualized by ultraviolet light.Auxins and cytokinins are phytohormones that play a major role in plant growth and development (6). The primary detection of a novel auxin or cytokinin in plant extracts depends on a suitable bioassay. Bioassays are also used to monitor the purification process and to evaluate the activity of purified or synthetic hormones. The most sensitive bioassay for cytokinins is based on the greening of cucumber cotyledons. The

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“…Our overall hypothesis is that adventitious rooting competence in cuttings has a molecular basis at the leve1 of auxinregulated gene expression in phloem parenchyma or inner cortical parenchyma cells during adventitious root initiation. In an attempt to identify genes that are specifically regulated during auxin-induced adventitious root initiation, we compared gene expression in cuttings from shoots of adventitious rooting-competent wild-type tobacco (Nicotiana tabacum cv Xanthii) with the rooting-incompetent rac mutant (Muller et al, 1985;Caboche et al, 1987;Pelese et al, 1989;Barbier-Brygoo et al, 1991).…”

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Differential Gene Expression in Response to Auxin Treatment in the Wild Type and rac, an Adventitious Rooting-Incompetent Mutant of Tobacco

Lund

Smith²,

Hackett

1997

Plant Physiology

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Histological analyses of auxin-treated cuttings from the wild type and the rac mutant of tobacco (Nicotiana tabacum cv Xanthii) previously revealed that some rac phloem parenchyma or inner cortical parenchyma cells form callus in response to exogenous auxin treatment but these cells never undergo the organized divisions associated with adventitious root initiation in the wild type. Here we report the effect of the rac mutation on the temporal and spatial expression patterns of three genes previously shown to be associated with adventitious root meristems, HRGPnt3, iaa4/5, and gh3. Using histochemical staining analyses of HRGPnt3-GUS transformant cuttings, we determined that the rac mutation blocks auxin activation of the HRGPnt3 promoter. Thus, activation of the HRGPnt3 promoter occurs specifically during adventitious root initiation in tobacco cuttings. Histochemical staining analyses of iaa4/5-GUS and gh3-GUS transformant cuttings revealed that the rac mutation does not repress the auxin activation of the iaa4/5 and gh3 promoters. Based on our histochemical staining analyses, we conclude that differential gene expression occurs in response to auxin treatment during adventitious root initiation in the wild type compared with callus formation in rac cuttings. We also determined that HRGPnt3 mRNA accumulation occurs in response to components of our root-induction protocol other than auxin, indicating that HRGPnt3 expression is regulated both developmentally and environmentally.

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Comparison of the Growth Promoting Activities and Toxicities of Various Auxin Analogs on Cells Derived from Wild Type and a Nonrooting Mutant of Tobacco

Cited by 30 publications

References 20 publications

Hormonal Characterization of a Nonrooting Naphthalene-Acetic Acid Tolerant Tobacco Mutant by an Immunoenzymic Method

Hormonal Characterization of a Nonrooting Naphthalene-Acetic Acid Tolerant Tobacco Mutant by an Immunoenzymic Method

A New Bioassay for Auxins and Cytokinins

Differential Gene Expression in Response to Auxin Treatment in the Wild Type and rac, an Adventitious Rooting-Incompetent Mutant of Tobacco

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