Auxin-induced Ethylene Research Articles

Ethylene Promotes Elongation Growth and Auxin Promotes Radial Growth in Ranunculus sceleratus Petioles

Submergence induces elongation in the petioles of Ranunculus sceleratus L., after a rise in endogenous ethylene levels in the tissue. Petioles of isolated leaves also elongate 100% in 24 hours when treated with ethylene gas, without a change in the radius. Application of silver thiosulfate, aminoethoxyvinylglycine (AVG), abscisic acid (ABA), or methyl jasmonate inhibits this elongation response. Gibberellic acid treatment promotes ethylene-induced elongation, without an effect on the radius. Indoelastic acid (IAA) induces radial growth in the petioles, irrespective of the presence or absence of added ethylene. High concentrations of IAA will also induce elongation growth, but this is largely due to auxin-induced ethylene synthesis; treatment with silver thiosulfate, AVG, ABA, or methyl jasmonate inhibit this auxin-promoted elongation growth. However, the radial growth induced by IAA is not affected by gibberellic acid, and not specifically inhibited by ABA, methyl jasmonate, silver thiosulfate, or AVG. These results support the idea that petiole cell elongation during "accommodation growth" can be separated from radial expansion. The radial expansion may well be regulated by IAA. However, effects of high levels of IAA are probably anomalous, since they do not mimic normal developmental patterns.

Polyamines and somatic embryogenesis in carrot. I. The effects of difluoromethylornithine and difluoromethylarginine

2,4-Dichlorophenoxyacetic acid (2,4-D) is the most commonly used and a very effective inhibitor of somatic embryogenesis in carrot. This growth regulator not only suppresses differentiation of cultured cells but it can also cause a reversion of the developing embryos to undifferentiated callus. Data presented here show that the addition of 1–10 mM DFMO (difluoromethylornithine) to the medium allowed the normal development of somatic embryos to continue even in the presence of inhibitory concentrations of 2,4-D. DFMO caused a significant increase in ADC activity, an increased accumulation of polyamines in the cells, and inhibited the accumulation of ethylene in cell cultures both in the presence or the absence of 2,4-D. Difluoromethylarginine (DFMA) at 0.1–1.0 mM concentration completely inhibited embryogenesis even in the absence of 2,4-D. DFMA also inhibited ADC activity and caused a reduction in the cellular polyamine levels. ODC activity was detected only when fully mature somatic embryos appeared in the cultures. It is suggested that auxin-induced ethylene biosynthesis plays an important role in the development of somatic embryos in carrot. The promotion of polyamine biosynthesis (by DFMO in the present case) may cause a reduction in the cellular pools of S-adenosylmethionine, which in turn may cause a reduction in ethylene biosynthesis, thus allowing embryogenesis to occur in the presence of an auxin.

Effect of Surfactants on Foliar Penetration of NAA and NAA-induced Ethylene Evolution in Cowpea

Abstract Effects of the surfactants Pace, Regulaid and Tween 20 were determined on foliar penetration of NAA and on NAA-induced ethylene production by cowpea [Vigna unguiculata (L.) Walp. subsp. unguiculata cv. Dixielee]. All three surfactants decreased surface tension of NAA solutions, causing a marked increase in wetting and in droplet : leaf interface area. The greatest increase in NAA penetration was obtained with Regulaid followed by Pace and Tween 20. The surfactant effect was most pronounced during the droplet drying phase, but penetration continued to take place from the deposit after drying. The mode of action of surfactants in enhancing NAA penetration is complex. Regulaid-enhanced penetration closely paralleled the increase in interface area, but similar relationships were not found for Pace or Tween 20, particularly at concentrations above the critical micelle concentration. Surfactant-enhanced NAA penetration caused an increase in NAA-induced ethylene production. There was a strong correlation (r = 0.82) between NAA penetration and ethylene production for doses of 0.5 to 2.5 μg/disk. Above 2.5 μg/disk, ethylene production increased at a decreasing rate. The potential for using auxin-induced ethylene production as an index for quantifying auxin penetration is discussed. Chemical names used: l-naphthaleneacetic acid (NAA), polyoxyethylene polypropoxypropanol dihydroxypropane (Regulaid), polyoxyethylene (20) sorbitan monolaurate (Tween 20), surfactant blend in paraffin base petroleum oil (Pace).

NAA-induced Leaf Epinasty in Chrysanthemum

Abstract Leaves of ‘Mountain Snow’ chrysanthemums (Chrysanthemum morifolium Ramat.), sprayed with 10 mm NAA or 10 mm NAAEE, exhibited severe epinasty after 24 hr, while leaves sprayed with 5 mm ethephon did not. Treatment with 100 μm AOA 24 hr before application reduced ethylene production rate of leaves, but not epinasty. Localized application of NAA to adaxial, abaxial, or both leaf surfaces resulted in similar amounts of leaf epinasty. Epinastic leaves had enlarged adaxial epidermal cells. Size of abaxial epidermal cells was unchanged. This study provides evidence that leaf epinasty of chrysanthemum following NAA application is not the result of auxin-induced ethylene production. Chemical names used: (aminooxy)acetic acid (AOA); 1-naphthaleneacetic acid (NAA); 1-naphthaleneacetic acid ethyl ester (NAAEE); and (2-chloroethyl)phosphonic acid (ethephon).

Insensitivity of the Diageotropica Tomato Mutant to Auxin

The sensitivity of excised hypocotyl segments to indoleacetic acid (IAA) in two assays, ethylene production and elongation, was determined in the ethylene-requiring tomato (Lycopersicon esculentum Mill.) mutant, diageotropica (dgt), and its isogenic parent, cv VFN8. Endogenous (uninduced) ethylene synthesis rates were slightly lower in dgt hypocotyls than in VFN8 hypocotyls. Ethylene production was essentially unaffected by IAA in dgt, but was stimulated up to 10-fold by 10 micromolar IAA in VFN8. Elongation of dgt hypocotyls was also insensitive to concentrations of IAA as high as 100 micromolar, as compared to significant elongation of VFN8 hypocotyls in response to 0.1 micromolar IAA. A range of IAA analogs active in VFN8 was also ineffective in stimulating elongation of dgt hypocotyls, suggesting that the differences were not due to rapid metabolism of IAA by dgt tissues. Auxin-induced elongation of VFN8 hypocotyls was unaffected by 2,3,5-triiodobenzoic acid and naphthylphthalamic acid, indicating that polar auxin transport was not a factor in these experiments. Exogenous and auxin-induced ethylene had no effect on the elongation respone of either genotype, nor did exogenous ethylene restore the sensitivity of dgt hypocotyls to IAA. Despite their apparent insensitivity to auxin, dgt hypocotyls elongated dramatically and synthesized ethylene rapidly in response to 1.2 micromolar fusicoccin. These results suggest that the primary effect of the dgt mutation is to reduce the sensitivity of the tissue to auxin. As altered regulation of ethylene synthesis is only one symptom of this fundamental deficiency, dgt should more properly be considered to be the auxin-insensitive tomato mutant.

High Temperature Sensitivity of Auxin-induced Ethylene Production in Mung Bean Hypocotyl Sections

High Temperature Sensitivity of Auxin-induced Ethylene Production in Mung Bean Hypocotyl Sections

Epidermal Cells Do Not Contribute to Auxin-Induced Ethylene Production in Mung Bean Stem Sections

Epidermal Cells Do Not Contribute to Auxin-Induced Ethylene Production in Mung Bean Stem Sections

Effect of silver ions and ethylene on auxin metabolism and auxininduced ethylene production in tobacco leaf discs

The antagonistic effects of ethylene and Ag+ on the metabolism of [1‐14C]indole‐3‐acetic acid (IAA) and on the rates of ethylene production were studied in tobacco leaf discs (Nicotiana rustica var. Brasilia). During the first 10 h of incubation, Ag+‐pretreated leaf discs contained more free [14C]IAA than untreated ones due to decreased oxidative decarboxylation, and the discs also produced more ethylene. Exogenously supplied ethylene nullified these effects of Ag+. However, the most pronounced effect of Ag+ in increasing ethylene production, as well as the strongest antagonistic effect of exogenous ethylene, were found between 24 and 48 h of incubation. During this time span no effect on the level of free IAA and on its decarboxylation could be observed. It is suggested that ethylene exerted its autoinhibitory effect by a feedback control on the IAA‐induced ethylene biosynthesis. Possible mechanisms for the autoinhibitory effect of ethylene are discussed.

Ethylene Biosynthesis and its Regulation in Higher Plants

PATHWAY OF ETHYLENE BIOSyNTHESIS 156 Methionine as an Intermediate ....... 157 S-Adenosylmethionine as an Intermediate 158 I-Aminocyclopropanecarboxylic Acid as an Intermediate . ......... 158 Methionine Cycle ........ 161 Conversion of l-Aminocyclopropanecarboxylic Acid to Ethylene 164 REGULATION OF ETHYLENE BIOSYNTHESIS 167 Regulation in Ripening Fruits and Senescing Flowers ...... 167 Auxin-Induced Ethylene Production 169 Regulation of Ethylene Biosynthesis by Ethylene 169 Stress-Induced Ethylene Production . . . . . . . . 171 Regulation by Light and Carbon Dioxide 173 Inhibitors of Ethylene Biosynthesis : 174 Conjugation of l-Aminocyclopropanecarboxylic Acid to l-(Malonylamino) cyclopropanecarboxylic Acid 178 CONCLUDING REMARKS 180

Inhibition of Auxin-Induced Ethylene Production by Lycoricidinol

Etude du mecanisme par lequel le lycoricidinol isole des bulbes de lycoris radiata supprime l'induction de la production d'ethylene par l'auxine chez Vigna radiata

Auxin-Induced Ethylene Production as Related to Auxin Metabolism in Leaf Discs of Tobacco and Sugar Beet

Exogenously supplied indole-3-acetic acid (IAA) stimulated ethylene production in tobacco (Nicotiana glauca) leaf discs but not in those of sugar beet (Beta vulgaris L.). The stimulatory effect of IAA in tobacco was relatively small during the first 24 hours of incubation but became greater during the next 24 hours. It was found that leaf discs of these two species metabolized [1-(14)C]IAA quite differently. The rate of decarboxylation in sugar beet discs was much higher than in tobacco. The latter contained much less free IAA but a markedly higher level of IAA conjugates. The major conjugate in the sugar beet extracts was indole-3-acetylaspartic acid, whereas tobacco extracts contained mainly three polar IAA conjugates which were not found in the sugar beet extracts. The accumulation of the unidentified conjugates corresponded with the rise of ethylene production in the tobacco leaf discs. Reapplication of all the extracted IAA conjugates resulted in a great stimulation of ethylene production by tobacco leaf discs which was accompanied by decarboxylation of the IAA conjugates. The results suggest that in tobacco IAA-treated leaf discs the IAA conjugates could stimulate ethylene production by a slow release of free IAA. The inability of the exogenously supplied IAA to stimulate ethylene production in the sugar beet leaf discs was not due to a deficiency of free IAA within the tissue but rather to the lack of responsiveness of this tissue to IAA, probably because of an autoinhibitory mechanism existing in the sugar beet leaf discs.

Mechanism of peroxidase isoenzyme induction in pollinated Nicotiana alata styles

A comparative study on the induction of peroxidase isoenzymes, specifically number 10 (P-10) in Nicotiana alata styles revealed significant differences between the various plants of an inbred progeny. In some plants the ageing-induced increase in P-10 activity was very low, whereas in some others, it was relatively high. Pollination accelerated this increase, independent of the pollen genotype. Fertilization was followed by a considerable increase in the activity of several peroxidase isoenzymes, including P-10 in all the plants.Two plants that differed greatly with regard to P-10 induction were used in additional experiments in order to ascertain the mechanism involved in the induction of P-10. The increase in P-10 activity due to pollination or fertilization can partly be explained on the basis of auxin and auxin-induced ethylene activity. The differences in P-10 induction between various plants of the inbred progeny were probably due to differences in their sensitivity to ethylene.

Stimulation of in vitro RNA Synthesis by Pretreating Plants with Auxins is Due to Auxin-Induced Ethylene Production

Summary Nucleoli isolated from mung bean ( Phaseolus aureus ROXB.) hypocotyls were much more active in carrying out in vitro RNA synthesis when prepared from seedlings previously sprayed with solutions of IAA or 2,4-D. No difference was found between the molecular weight of the RNA synthesised by nucleoli from control plants and those sprayed with auxins. The response to auxins developed a few hours after spraying and in vitro nucleolar activity continued to increase for at least 18 h. A large increase in ethylene evolution by auxin-sprayed plants was detected before the stimulation of nucleolar RNA synthesis. A similar stimulation of nucleolar RNA synthesis was found after plants were sprayed with a solution of the ethylene-generating compound ethephon and increased RNA synthesis was observed after exposing plants to ethylene alone. It is suggested that the increase in nucleolar RNA synthesis brought about by spraying plants with auxin is caused by auxin-induced ethylene production. It is further suggested that the enhanced activity is due to an increase in the number of RNA polymerase I molecules bound to the rRNA genes in the nucleoli.

Regulation of Auxin-induced Ethylene Biosynthesis. Repression of Inductive Formation of 1-Aminocyclopropane-1-carboxylate Synthase by Ethylene

Regulation of Auxin-induced Ethylene Biosynthesis. Repression of Inductive Formation of 1-Aminocyclopropane-1-carboxylate Synthase by Ethylene

Promotion of growth and shift in the auxin dose/response relationship in maize roots treated with the ethylene biosynthesis inhibitors aminoethoxyvinylglycine and cobalt

Indole-3-acetic acid (IAA) in concentrations from 10 −12 M to 10 −9 M does not stimulate elongation when applied to intact roots of maize ( Zea mays L Bear Hybrid WF 9 × 38). Higher concentrations are inhibitory. In roots pretreated with the ethylene biosynthesis inhibitors, cobalt and aminoethoxyvinylglycine (AVG), IAA from 10 −10 M to 10 −8 M promotes growth. High concentrations of IAA (eg. 10 −6 M) strongly inhibit growth in either pretreated or non-pretreated roots. The data indicate that low concentrations of auxin are capable of stimulating the growth of intact roots in which ethylene biosynthesis is suppressed. This suggests that auxin-induced ethylene biosynthesis may account, at least in part, for auxin inhibition of root growth at high concentrations and for the failure of auxin to stimulate intact root growth at low concentrations.

The Effect of IAA, IBA, NAA, and 2,4-D on Root Promotion and Ethylene Evolution in Vigna radiata Cuttings1

Abstract Ethylene liberated from control and auxin-treated cuttings of Vigna radiata (L.) R. Wilcz cv. Berken was monitored for 14 hours. For root initiation, naphthaleneacetic acid (NAA) and indolebutyric acid (IBA) were the most effective with indoleacetic acid (IAA) intermediate and 2,4-dichlorophenoxyacetic (2,4-D) the least effective. No correlation was observed between the quantity of auxin-induced ethylene evolved and the number of roots formed. Decreasing the NAA solution pH from 7.0 to 3.0 reduced the evolution of ethylene but did not alter the rooting response of the cuttings. It was concluded that stimulation of adventitious root initiation by auxin is not mediated by ethylene.

Lateral Bud Growth inPhaseolus vulgarisL. and the Levels of Ethylene in the Bud and Adjacent Tissue

Ethephon and the ethylene inhibitors Ag+ and aminoethoxyvinyl glycine (AVG) inhibited outgrowth of the axillary bud of the first trifoliate leaf in decapitated plants of Phaseolus vulgaris. Endogenous ethylene levels decreased in the stem upon decapitation although it is not conclusive that a causal relationship exists between this decrease and the release of axillary buds from inhibition. The proposition that auxin-induced ethylene is responsible for the suppression of axillary bud growth in the decapitated plant when the apical shoot is replaced by auxin is not borne out in this study. Application of IAA directly to the axillary bud of intact plants gave rise to a transient increase in bud growth. This growth increment was annulled when AVG was supplied with IAA to the bud despite the fact that the dosage of AVG used did not affect the normal slow growth rate of the bud of the intact plant or bud outgrowth resulting from shoot decapitation.

Polyamines Inhibit Biosynthesis of Ethylene in Higher Plant Tissue and Fruit Protoplasts

Ethylene production in apple fruit and protoplasts and in leaf tissue was inhibited by spermidine or spermine. These polyamines, as well as putrescine, inhibited auxin-induced ethylene production and the conversion of methionine and 1-aminocyclopropane-1-carboxylic acid to ethylene. Polyamines were more effective as inhibitors of ethylene synthesis at the early, rather than at the late, stages of fruit ripening. Ca(2+) in the incubation medium reduced the inhibitory effect caused by the amines. A possible mode of action by which polyamines inhibit ethylene production is discussed.

Biosynthesis of Auxin-Induced Ethylene. Effects of Indole-3-Acetic Acid, Benzyladenine and Abscisic Acid on Endogenous Levels of 1-Aminocyclopropane-l-Carboxylic Acid (ACC) and ACC Synthase

Biosynthesis of Auxin-Induced Ethylene. Effects of Indole-3-Acetic Acid, Benzyladenine and Abscisic Acid on Endogenous Levels of 1-Aminocyclopropane-l-Carboxylic Acid (ACC) and ACC Synthase

Effect of polyamines on ethylene production

The polyamines putrescine, cadaverine, spermidine and spermine reduced the amount of ethylene produced by senescing petals of Tradescantia but they did not prevent anthocyanin leakage from these same petals. These polyamines also inhibited auxin-mediated ethylene production by etiolated soybean hypocotyls to less than 7 % of the control. The basic amino acids lysine and histidine reduced the amount of auxin-induced ethylene produced by soybean hypocotyls by ca 50 %. In the hypocotyls, methionine was unable to overcome the inhibition caused by the polyamines. The polyamines spermidine and spermine inhibited ethylene production induced by the application of 1-aminocyclopropane-1-carboxylic acid and they also reduced the endogenous content of this amino acid in the treated tissues.