Endogenous levels of abscisic acid and indole-3-acetic acid during in vitro rooting of Wild Cherry explants produced by micropropagation

Levels of endogenous ABA and IAA were quantified during the first week of in vitro rooting of Wild Cherry (Prunus avium L.) using IBA in the culture medium. Hormones were measured in the apical, median and basal parts of the explants using an avidin-biotin based enzyme linked immunosorbent assay (ELISA), after a purification of the methanolic extracts by high-performance liquid chromatography (HPLC).Root primordia started to differentiate from day 5 at the basal part of the explants. ABA and IAA showed considerable changes and high levels were detected during the first week of culture. ABA levels increased transiently mainly in the apical part during root formation. Exogenous IBA was possibly transformed into IAA mainly in the basal part of the explants.     

Comparison of movement and metabolism of indole-3-acetic acid and indole-3-butyric acid in mung bean cuttings

Indole-3-butyric acid (IBA) was much more effective than indole-3-acetic acid (IAA) in inducing adventitious root formation in mung bean ( Vigna radiata L.) cuttings. Prolonging the duration of treatment with both auxins from 24 to 96 h significantly increased the number of roots formed. Labelled IAA and IBA applied to the basal cut surface of the cuttings were transported acropetally. With both auxins, most radioactivity was detected in the hypocotyl, where roots were formed, but relatively more IBA was found in the upper sections of the cuttings. The rate of metabolism of IAA and IBA in these cuttings was similar. Both auxins were metabolized very rapidly and 24 h after application only a small fraction of the radioactivity corresponded to the free auxins. Hydrolysis with 7 M NaOH indicates that conjugation is the major pathway of IAA and IBA metabolism in mung bean tissues. The major conjugate of IAA was identified tentatively as indole-3-acetylaspartic acid, whereas IBA formed at least two major conjugates. The data indicate that the higher root-promoting activity of IBA was not due to a different transport pattern and/or a different rate of conjugation. It is suggested that the IBA conjugates may be a better source of free auxin than those of IAA and this may explain the higher activity of IBA.     

Quantitative relationship between indole-3-acetic acid and abscisic acid during leaf growth in Coleus blumei

Quantitative determinations by gas chromatography-mass spectrometry ofindole-3-acetic acid (IAA) and abscisic acid (ABA) in growing leaves ofColeusblumei plants show parallel declines in leaf concentrations of bothhormones,except in leaf number 3 (about three-fourths of full size) where IAA level wasthe lowest of those measured. Expansion of the most recently unfurled leaf tofull size serves, in effect, to dilute both IAA and ABA about 1.7 to 1.Althoughabsolute levels of leaf IAA varied as much as an order of magnitude from onebatch of plants to another, ABA levels were proportional to the IAA level withan overall correlation coefficient of 0.91. Evidence, both correlative andcausal, for the determination of ABA status by IAA—and of IAA status byABA—in leaves and other developing organs is summarized.     

Interaction of ethylene with indole-3-acetic acid in regulation of rooting in pea cuttings

Cuttings of pea (Pisum sativum L. cv Marma) were treated with 1-aminocyclopropane-l-carboxylic acid (ACC). This treatment caused increased ethylene production and reduction of root formation. The effect of 0.1 mM ACC on the level of endogenous indole-3-acetic acid (IAA) in the rooting zone and in the shoot apex was analyzed by gas chromatography-single ion monitoring mass spectrometry or by high pressure liquid chromatography with fluorimetric detection (HPLC). Concentrations of indole-3-acetylaspartic acid (IAAsp) in the stem bases were also determined using HPLC. The ACC treatment had little effect on the IAA level in the base measured after 24 h, but caused a considerable decrease during the 3 following days. IAAsp increased in the base on days 1, 2 and 3 and then declined. The build up of IAAsp in the base was not affected by ACC during the first two days of the treatment, but later this conjugate decreased more rapidly than in controls. No effect of the ACC treatment was found on the level of IAA in the apex. IAA (1 µM) applied to the cuttings during 24 h reduced the number of roots formed. The possibility that IAA-induced ethylene is involved in this response was investigated.Our results support earlier evidence that the inhibitory effect of ethylene on rooting in pea cuttings is due to decreased IAA levels in the rooting zone. The inhibitory effect of applied IAA is obtained if the internal IAA level is maintained high during the first 24 h, whereas stimulation of rooting occurs if the internal IAA level remains high during an extended period of time. Our results do not support the suggestion that ethylene mediates the inhibitory effect of applied IAA.     

Levels of endogenous indole-3-acetic acid and indole-3-acetylaspartic acid during adventitious root formation in pea cuttings

Levels of endogenous indole-3-acetic acid (IAA) and indole-3-acetylaspartic acid (IAAsp) were monitored in various parts of leafy cuttings of pea ( Pisum sativum L. cv. Marma) during the course of adventitious root formation. IAA and IAAsp were identified by combined gas chromatography—mass spectrometry, and the quantitations were performed by means of high performance liquid chromatography with spectrofluorometric detection. IAA levels in the root forming tissue of the stem base, the upper part of the stem base (where no roots were formed), and the shoot apex remained constant during the period studied and were similar to levels occurring in the intact seedling. A reduction of the IAA level in the root regenerating zone, achieved by removing the shoot apex, resulted in almost complete inhibition of root formation. The IAAsp level in the shoot apex also remained constant, whereas in the stem base it increased 6-fold during the first 3 days. These results show that root initiation may occur without increased IAA levels in the root regenerating zone. It is concluded that the steady-state concentration is maintained by basipetal IAA transport from the shoot apex and by conjugation of excessive IAA with aspartic acid, thereby preventing accumulation of IAA in the tissue.     

热胁迫对不同发育阶段大豆生长素和脱落酸含量的影响(英文)

大豆等植物体内细胞受热或受其它理化因素（如：重金属离子、乙醇、氨基酸类似物）、以及缺氧、DNA损伤、病毒感染等病理因素刺激后,促发应激反应,启动某些基因表达,能产生各种生理活性物质以及各种酶类,共同调控代谢过程和某些激素的活动,如：吲哚乙酸（IAA）、脱落酸（ABA）等。这些内源IAA和ABA共同作用,调节着大豆的抗逆性,从而影响着大豆的农艺性状。本试验对华北生态型的六个大豆栽培种,进行热激处理;取其第三片展开叶,测其内源IAA和ABA含量。这些品种分别是：早熟17,诱处4号,诱变31,耐阴黑豆、科丰6号和科丰34（Tan．1）。初花期,第一天热激（43～45℃,4h）后,它们的IAA和ABA水平均显著高于对照（30～33℃）（Fig．1）。然而,在连续一天热激后（43～45℃,4h／d）,大多数品种的IAA和ABA比第一天减少（Fig．2）。盛花期连续热激处理二天（43～45℃,4h／d）,IAA水平一般低于对照（3～33℃）,半数品种ABA水平也低于对照（Fig．3）。结荚期连续两天热激后（45℃,4h／d）,IAA和ABA含量均显著高于对照（30～33℃）（Fig．4）。     

Transport and metabolism of indole-3-butyric acid in cuttings of Leucadendron discolor

Indole-3-butyric acid (IBA) greatly enhanced the rooting of an early-flowering variety of protea, Leucadendron discolor, but had very little effect on a late-flowering variety. IBA transport and metabolism were studied in both varieties after incubating the cuttings in ³H-IBA. More of the radio-label was transported to the leaves of the easy-to-root variety than the difficult-to-root (35–45% and 10%, respectively). IBA was metabolized rapidly by the cuttings of both varieties and after 24 h most of the label was in the new metabolite. However, free IBA (about 10%) was present in the cuttings during the whole period up to the time of root emergence (4 weeks). More free IBA was accumulated in the base of easy-to-root cuttings, while in the difficult-to-root variety most of the IBA was found in the leaves. The metabolite was identified tentatively as an ester conjugate with a glucose. It is possible that IBA-glucose serves as a source for free IBA, and the difference between the varieties is a consequence of the free IBA which is released, transported and accumulated in the site of a root formation.     

Effects of water stress on cellular ultrastructure and on concentrations of endogenous abscisic acid and indole-3-acetic acid in Fatsia japonica leaves

Ultrastructural alterations in mesophyll cells as well as variations in bulk leaf endogenous ABA and IAA concentrations were studied in water-stressed field-grown plants of Fatsia japonica. Under water deficit cellular membranes were modified and an increase in vesicles was observed. The main damage to the chloroplasts included thylakoid swelling and disruption of the chloroplast envelope. Concomitant variations in abscisic acid and indole-3-acetic acid were observed. Despite the expected increased in endogenous ABA concentration in relation to water stress, after the highest concentration of ABA, observed at predawn in severely stressed plants (29-1), there was a sharp decline from 2768 pmol g fw^–1 to 145 pmol g fw^–1; thus in severely stressed plants ABA levels were not related to changes in bulk leaf ABA contents. Water stress did not influence the concentrations of indole-3-acetic acid, although the increase in the endogenous abscisic acid concentration could be related with the ultrastructural changes.Abbreviations ABA abscisic acid - IAA indole-3-acetic acid - leaf water potential     

Definitive identification of indole-3-acetic acid and abscisic acid in shoots of Coleus blumei by gas chromatography-mass spectrometry

Mass spectra provide definitive identification of indole-3-acetic acid and abscisic acid in shoots of Coleus blumei, a species used for studying the hormone control of plant development since the early 1930s.     

Endogenous indole-3-acetic acid and abscisic acid in apple microcuttings in relation to adventitious root formation

The effects of applying indole-3-butyric acid (IBA) for periods up to 48 h were examined in difficult-to-root microcuttings (from newly-established cultures) and in easy-to-root microcuttings (from long-term subcultures) of Jonathan apple (Malus X domestica Borkh). In easy-to-root material, 20% of the microcuttings produced roots in the absence of IBA, while 6 h exposure to 10 M IBA gave 100% rooting of microcuttings. In contrast, root formation in difficult-to-root material was IBA-dependent. Maximum rooting of these microcuttings (50%) required 24 h exposure to 10 M IBA.Variation in the endogenous levels of free indole-3-acetic acid (IAA) during the course of root induction was similar in microcuttings of both types but there were marked differences in endogenous abscisic acid (ABA) levels. In easy-to-root microcuttings ABA remained at a constant low level, but in difficult-to-root material ABA exhibited marked fluctuations and was present at higher concentrations than in easy-to-root microcuttings.     

Transport and accumulation of indole-3-acetic acid in pea cuttings under two levels of irradiance

The transport and accumulation of 2-[¹⁴C]-IAA applied to the apex of cuttings of Pisum sativum L. cv. Alaska was greater in cuttings from stock plants grown under 38 W m⁻² than 16 W m⁻². Accumulation of ^14C in the base of the cuttings from the highest level of irradiance was correspondingly more significant. The level of irradiance to the stock plants greatly affected the rate of accumulation, while the light conditions during IAA transport had a minor effect. The amount of IAA reaching the base of the cuttings increased with increasing concentration of IAA in the treatment solution, but the percentage of applied IAA reaching the base decreased.
The relative chromatographic partition of ethanol-extractable ¹⁴C showed that, after 12 h of IAA-transport, the amount of 2-[¹⁴C]-IAA was higher in the base of cuttings from 38 W m⁻² than in those from 16 W m⁻². After a further 12 h of transport the relative amounts of 2-[¹⁴C]-IAA in the two types of cuttings were reduced to the same lower level.
A possible role of an irradiance-mediated difference in the topographic distribution of IAA in the base of pea cuttings on the subsequent adventitious root formation is discussed.     

Immunocytochemical localization of indole-3-acetic acid in primary roots of Zea mays

Colloidal gold-labelled antibody was used to localize indole-3-acetic acid in caps of primary roots of Z. mays cv. Kys. Gold particles accumulated on the nucleus, vacuoles, mitochondria, and some dictyosomes and dictyosome-derived vesicles. This is the first localization of indole-3-acetic acid in dictyosomes and dictyosome-derived vesicles and indicates that dictyosomes and vesicles constitute a pathway for indole-3-acetic acid movement in and secretion from root cap cells. Our findings provide cytochemical evidence to support the hypothesis that indole-3-acetic acid plays an important role in root gravitropism.     

The effect of etiolation and shading of stock plants on rhizogenesis in stem cuttings of <Emphasis Type="Italic">Cotinus coggygria</Emphasis>

In order to improve vegetative propagation of a difficult to root Cotinus coggygria the stock plants were subjected to: etiolation, shading and spraying with IBA, combined with the application of two commercially available rooting powders. The IBA treatment was more suitable for rooting of C. coggygria cuttings than the NAA application and it enhanced rhizogenesis regardless of the form of auxin application (foliar application to a stock plant or a rooting powder used directly on cuttings) and the amount of light provided to stock plants. Etiolation did not improve rhizogenesis in stem cuttings, however, reduction of light intensity by 50% and 96% of the ambient prior to harvest of cuttings affected rooting positively. Positive effects of shading can be ascribed to changes in shoot anatomy, i.e. a weaker sclerenchyma development. Synergistic effect of shading and foliar auxin application can result from the increase in leaf blade area and/or thinner lower epiderm. Enhanced rooting in cuttings from shoots grown out under reduced light intensity was accompanied by decrease in the contents of total soluble sugars, soluble proteins and free ABA and by increase in total chlorophyll, free amino acids, polyphenolic acids and free IAA contents.     

Effects of indole-3-acetic acid on arsenic uptake and antioxidative enzymes in Pteris cretica var. nervosa and Pteris ensiformis

A hydroponic experiment was conducted to investigate the effects of indole-3-acetic acid (IAA) on arsenic (As) uptake and antioxidative enzymes in fronds of Pteris cretica var. nervosa (As hyperaccumulator) and Pteris ensiformis (non-hyperaccumulator). Plants were exposed to 2 mg L^?1 As(III), As(V) or dimethylarsinic acid (DMA) and IAA concentrations for 14 d. The biomass and total As in the plants significantly increased at 30 mg L^?1 IAA. Superoxide dismutase (SOD) activities significantly increased with IAA addition. Catalase (CAT) activities showed a significant increase in P. ensiformis exposed to three As species at 30 or 50 mg L^?1 IAA but varied in P. cretica var. nervosa. Peroxidase (POD) activities were unchanged in P. ensiformis except for a significant decrease at 50 mg L^?1 IAA under As(III) treatment. However, a significant increase was observed in P. cretica var. nervosa at 10 mg L^?1 IAA under As(III) or DMA treatment and at 50 mg L^?1 IAA under As(V) treatment. Under DMA stress, malondialdehyde contents in fronds of P. cretica var. nervosa showed a significant decrease at 10 mg L^?1 IAA but remained unchanged in P. ensiformis. Therefore, IAA enhanced As uptake and frond POD activity in P. cretica var. nervosa under As stress.     

Endogenous indoles and the biosynthesis and metabolism of indole-3-acetic acid in cultures of Rhizobium phaseoli

Gas chromatography-mass spectrometric analyses of purified extracts from cultures of Rhizobium phaseoli wild-type strain 8002, grown in a non-tryptophan-supplemented liquid medium, demonstrated the presence of indole-3-acetic acid (IAA), indole-3-ethanol (IEt), indole-3-aldehyde and indole-3-methanol (IM). In metabolism studies with ³H-, ¹⁴C- and ²H-labelled substrates the bacterium was shown to convert tryptophan to IEt, IAA and IM; IEt to IAA and IM; and IAA to IM. Indole-3-acetamide (IAAm) could not be detected as either an endogenous constituent or a metabolite of [³H]tryptophan nor did cultures convert [¹⁴C]IAAm to IAA. Biosynthesis of IAA in R. phaseoli, thus, involves a different pathway from that operating in Pseudomonas savastanio and Agrobacterium tumefaciens-induced crown-gall tumours.Abbreviations IAA indole-3-acetic acid - IAld indole-3-aldehyde - IAAm indole-3-acetamide - IEt indole-3-ethanol - IM indole-3-methanol - HPLC-RC high-performance liquid chromatography-radio counting - GC-MS gas chromatography-mass spectrometry     

Immunohistochemical observation of indole-3-acetic acid at the IAA synthetic maize coleoptile tips

To investigate the distribution of IAA (indole-3-acetic acid) and the IAA synthetic cells in maize coleoptiles, we established immunohistochemistry of IAA using an anti-IAA-C-monoclonal antibody. We first confirmed the specificity of the antibody by comparing the amounts of endogenous free and conjugated IAA to the IAA signal obtained from the IAA antibody. Depletion of endogenous IAA showed a corresponding decrease in immuno-signal intensity and negligible cross-reactivity against IAA-related compounds, including tryptophan, indole-3-acetamide, and conjugated-IAA was observed. Immunolocalization showed that the IAA signal was intense in the approximately 1 mm region and the outer epidermis at the approximately 0.5 mm region from the top of coleoptiles treated with 1-N-naphthylphthalamic acid. By contrast, the IAA immuno-signal in the outer epidermis almost disappeared after 5-methyl-tryptophan treatment. Immunogold labeling of IAA with an anti-IAA-N-polyclonal antibody in the outer-epidermal cells showed cytoplasmic localization of free-IAA, but none in cell walls or vacuoles. These findings indicated that IAA is synthesized in the 0–2.0 mm region of maize coleoptile tips from Trp, in which the outer-epidermal cells of the 0.5 mm tip are the most active IAA synthetic cells.     

Double agent indole-3-acetic acid: mechanistic analysis of indole-3-acetaldehyde dehydrogenase AldA that synthesizes IAA,an auxin that aids bacterial virulence

The large diversity of organisms inhabiting various environmental niches on our planet are engaged in a lively exchange of biomolecules, including nutrients, hormones, and vitamins. In a quest to survive, organisms that we define as pathogens employ innovative methods to extract valuable resources from their host leading to an infection. One such instance is where plant-associated bacterial pathogens synthesize and deploy hormones or their molecular mimics to manipulate the physiology of the host plant. This commentary describes one such specific example—the mechanism of the enzyme AldA, an aldehyde dehydrogenase (ALDH) from the bacterial plant pathogen Pseudomonas syringae which produces the plant auxin hormone indole-3-acetic acid (IAA) by oxidizing the substrate indole-3-acetaldehyde (IAAld) using the cofactor nicotinamide adenine dinucleotide (NAD⁺) (Bioscience Reports (2020) 40(12), https://doi.org/10.1042/BSR20202959). Using mutagenesis, enzyme kinetics, and structural analysis, Zhang et al. established that the progress of the reaction hinges on the formation of two distinct conformations of NAD(H) during the reaction course. Additionally, a key mutation in the AldA active site ‘aromatic box’ changes the enzyme’s preference for an aromatic substrate to an aliphatic one. Our commentary concludes that such molecular level investigations help to establish the nature of the dynamics of NAD(H) in ALDH-catalyzed reactions, and further show that the key active site residues control substrate specificity. We also contemplate that insights from the present study can be used to engineer novel ALDH enzymes for environmental, health, and industrial applications.     

Tracheid production in response to indole-3-acetic acid varies with internode age in Pinus sylvestris stems

Summary Different concentrations of indole-3-acetic acid (IAA) in lanolin were applied to the cambial region of approximately 10- and 34-year-old internodes in the main stem of Pinus sylvestris (L.) trees during the tracheid production period. After 5 weeks of treatment, the radial width of xylem produced in both ages of internode was positively related to exogenous IAA concentration measured at 0, 1 and 3 cm directly below the application site. Tracheid production in response to exogenous IAA in the 34-year-old internode was approximately one-half of that in the 10-year-old internode. The endogenous IAA level in the 7-, 17- and approximately 34-year-old internodes of similar trees was measured by radioimmunoassay, using gas chromatography-selected ion monitoring-mass spectrometry for validation. No consistent relationship was found between xylem radial width and IAA concentration. The data indicate that the cambium's ability to respond to exogenous IAA is qualitatively the same in 1-year-old shoots and older internodes. However, as the internode ages, there is a decrease in the extent of the response and in the optimal IAA level for inducing tracheid production.     

Polyamines,indole-3-acetic acid and abscisic acid in rice phloem sap

Putrescine, spermidine, spermine and cadaverine have been identified and quantified in rice phloem sap and shoot extracts by HPLC. It is suggested that diamines, putrescine and cadaverine, easily migrate into the phloem, while movement of a triamine, spermidine, and a tetramine, spermine, tend to be restricted. Spermine especially seems to be the most immobile among polyamines. Thus it is indicated that movement of polyamines into phloem is decreased with increasing number of amino groups. Indole-3-acetic acid and abscisic acid in rice phloem sap were also analyzed by HPLC and it is suggested that indole-3-acetic acid is transported freely into phloem, while abscisic acid is much more actively exuded into phloem.     

Abscisic acid, indole-3-acetic acid and cytokinin changes in buds of Pseudotsuga menziesii during bud quiescence release

Bud quiescence release, considered as the ultimate dormancy breaking phase, was achieved in Pseudotsuga menziesii (Mirb.) Franco by a 9-week cold (5°C) treatment, under short daylength (9 h) followed by a transfer to mild temperature (22°C) under long daylength (16 h). Indole-3-acetic acid (IAA), abscisic acid (ABA), zeatin-type (Z) and isopentenyladenine-type (iPA) cytokinin (CK) levels were measured by means of an ELISA technique performed on HPLC-fractionated extracts of terminal and axillary buds. During the cold period, all hormones except IP-type CK levels decreased, whereas the opposite observation was made after transfer to mild temperature and long daylength, when buds started to grow. Some other immunoreactive compounds were also detected and quantified. The ABA-glucosyl ester (ABA-GE) level pattern was similar to that of ABA, but no accumulation occurred at mild temperatures. A putative IAA conjugate, more polar than IAA, was also detected. Its level increased transiently like IAA in terminal buds and, to a lesser extent, in axillary buds during the 10th week of the experiment. In terminal buds, isopentenyladenosine ([9R]-iP) was released by alkaline hydrolysis of a polar immunoreactive compound detected with anti-[9R]iP antibodies. This compound accumulated during the cold period and quickly dropped at 22°C. Relationships between environmental conditions and endogenous hormones are discussed.