Endogenous Indole-3-acetic Acid Research Articles

Effect of indole-3-acetic acid on aluminum-induced efflux of malic acid from wheat (Triticum aestivum L.)

Indole-3-acetic acid (IAA) has been found to be involved in plant resistance to various types of environmental stress. Aluminum (Al) toxicity, as one of the most important environmental stress in acid soils, is coped by most plants through the efflux of organic acids via anion channel. This study aims to evaluate the effect of IAA on efflux of malic acid from wheat (Triticum aestivum L.) under Al stress. Hydroponic experiments were performed by wheat ET8 (Al-tolerant). The efflux of malic acid was investigated under different treatments. Results showed that Al treatments increased the accumulation of endogenous IAA, but decreased the activity of IAA oxidase in a dose-dependent manner. A good correlation between all the data of malic acid efflux rate and endogenous IAA content was obtained (R2 = 0.9859**). IAA treatment alone had no effect on the efflux of malic acid. But compared to Al (50 μM) treatment, the efflux of malic acid increased significantly under the co-treatment of IAA (50 μM) and Al (50 μM). In split-root experiments, the root with half of it being treated with Al (CK/Al), the other part (CK) showed significantly higher malic acid efflux rate and endogenous IAA content in root apexes, compared with the root without such treatment (CK/CK). The Al-induced malic acid efflux decreased under the treatments of IAA transport inhibitor N-1-napthyl-phtalamic acid (NPA) (or 2,3,5-triiodobenzoic acid, TIBA). These above results suggested the possible involvement of IAA in the stimulation of malic acid efflux under Al stress. In addition, anion channel inhibitor treatment experiment showed that IAA (50 μM) relieved the inhibiting effect of 5 μM anthracene-9-carboxylic acid (A9C) (or niflumic acid, NIF) on malic acid efflux induced by Al (50 μM), compared to the co-treatment of Al (50 μM) and 5 μM anion channel inhibitor A9C (or NIF) it is thus speculated that the anion channel might have been activated when IAA was involved in malic acid efflux. This study showed that IAA was involved in aluminum-induced efflux of malic acid from wheat.

Nitric oxide accumulation and actin distribution during auxin-induced adventitious root development in sunflower

Auxin-mediated adventitious root (AR) formation from the basal ends of hypocotyl segments in sunflower ( Helianthus annuus L., cv. Morden) is associated with gradual subcellular and anatomical changes. Pre-mitotic events (induction phase) are evident within 1 d (24 h) in the interfascicular parenchyma. Evidence for nitric oxide (NO) accumulation in the interfascicular cells 2 d after indole-3-acetic acid (IAA) treatment, highlights the involvement of NO specifically during root initiation, following AR induction phase. Thus, adventitious root induction and initiation can be distinguished as NO-independent and NO-dependent phases. Treatment of hypocotyl explants with 10 μM 1-napthylphthlamic acid (NPA), an inhibitor of polar auxin transport in plant cells, leads to complete abolition of NO-associated fluorescence, detected upon incubation of hypocotyl sections with 4,5-diaminofluorescein diacetate (DAF-2DA). This indicates a signaling link between auxin transport and NO accumulation in the target cells. Latrunculin B (Lat B), an actin depolymerizing agent, leads to substantial inhibition of IAA-induced AR response and NO accumulation in the responding cells. Aminoguanidine [an inhibitor of inducible form of nitric oxide synthase (iNOS)] brings about a reduction in the tissue NO content, indicating a significant activity of putative NOS leading to endogenous NO accumulation. Confocal laser scanning microscope (CLSM) imaging has revealed bundling of actin with NPA and Lat B treatments. A probable interaction is thus evident between actin and NO during auxin-mediated AR formation in the initiation and extension phase. Present work, thus, provides novel observations on an interaction among endogenous NO, IAA and actin at specific stages of AR formation.

Time-Course Analysis of Levels of Indole-3-Acetic Acid and Expression of Auxin-Responsive GH3 Genes in Betula platyphylla

Indole-3-acetic acid (IAA) is a natural hormone that plays an important role in the essential physiological processes of plant growth, development, and environmental response. To maintain IAA homeostasis in plants, some members of the GH3 gene family may mediate the conjugation of amino acids to indole-3-acetic acid. In this study, nine birch BpGH3 genes were cloned, including three BpGH3.5 genes, three BpGH3.6 genes, two BpGH3.9 genes, and a single BpGH3.3 gene, that were likely to be auxin-responsive genes. Time-course expression analysis of these nine BpGH3 genes using real-time reverse transcriptase–polymerase chain reaction (RT-PCR) was conducted using birch plant tissues collected during a 1-year growth cycle. Further, we determined the endogenous free IAA content in birch during this period by using liquid chromatography tandem mass spectrometry. The results indicated that the IAA levels changed remarkably throughout the study period; the level remained relatively stable during the developmental stage from June 1 to July 1, and IAA was present in the birch leaves throughout the study period. The correlation between the expression of BpGH3 genes and IAA levels was analyzed using Pearson correlation analysis. The results revealed a significant negative correlation between the expressions of four BpGH3 genes, namely, BpGH3.3 (p < 0.05), BpGH3.5a (p < 0.01), BpGH3.5b (p < 0.01), and BpGH3.9a (p < 0.01) and the free IAA level, thereby suggesting that these genes might play roles in IAA regulation.

Endogenous indole-3-acetic acid and trans-zeatin ribosides in relation to axillary bud formation in standard chrysanthemum

The lateral buds of non-branching chrysanthemum cultivars are affected by temperature and exogenous plant growth regulator (PGR) treatment. The number of axillary buds, endogenous indole-3-acetic acid (IAA) and t-zeatin riboside (t-ZR) concentrations by planting date and PGR treatments were investigated in three genotypes. Two non-branching genotypes, ‘Iwanohakusen’ and ‘01B1-8’ and branching type ‘Jinba’ were planted on May 2 and June 29. ‘Jinba’ always bore axillary buds and ‘01B1-8’ showed stronger non-branching traits than ‘Iwanohakusen’. Only 22.9% viable buds developed in the axils of ‘01B1-8’ whereas 68.7% developed in ‘Iwanohakusen’ on the May 2 planting date group. When planting was delayed from May 2 to June 29, the number of axillary buds decreased in both non-branching genotypes. Endogenous IAA concentrations remained unchanged and t-ZR concentrations decreased in all the three genotypes when the planting date was delayed. This reduced t-ZR level corresponds to the increased ratio of IAA/t-ZR. The number of viable axillary buds increased from 21.7% to 50.1% upon ethephon treatment and to 30.3% by synthetic cytokinin 6-benzylaminopurine (BAP) treatment in ‘01B1-8’. Viable axillary buds of ‘01B1-22’ increased from 17.1% to 25.1% and 29.1% respectively. Ethephon and BAP application decreased endogenous IAA contents and increased t-ZR contents. Elevated concentrations of t-ZR rather than IAA probably account for axillary bud formation in non-branching chrysanthemum. Just as the non-branching genotypes, the branching type cultivar ‘Jinba’ showed similar changes in IAA and t-ZR contents according to planting date and exogenous PGR treatments. These results showed that genotypic difference of branching patterns is not a result of concentration-dependent reaction.

Non-invasive quantification of endogenous root auxin transport using an integrated flux microsensor technique

Indole-3-acetic acid (IAA) is a primary phytohormone that regulates multiple aspects of plant development. Because polar transport of IAA is an essential determinant of organogenesis and dynamic tropic growth, methods to monitor IAA movement in vivo are in demand. A self-referencing electrochemical microsensor was optimized to non-invasively measure endogenous IAA flux near the surface of Zea mays roots without the addition of exogenous IAA. Enhanced sensor surface modification, decoupling of acquired signals, and integrated flux analyses were combined to provide direct, real time quantification of endogenous IAA movement in B73 maize inbred and brachytic2 (br2) auxin transport mutant roots. BR2 is localized in epidermal and hypodermal tissues at the root apex. br2 roots exhibit reduced shootward IAA transport at the root apex in radiotracer experiments and reduced gravitropic growth. IAA flux data indicates that maximal transport occurs in the distal elongation zone of maize roots, and net transport in/out of br2 roots was decreased compared to B73. Integration of short term real time flux data in this zone revealed oscillatory patterns, with B73 exhibiting shorter oscillatory periods and greater amplitude than br2. IAA efflux and influx were inhibited using 1-N-naphthylphthalamic acid (NPA), and 2-naphthoxyacetic acid (NOA), respectively. A simple harmonic oscillation model of these data produced a correlation between modeled and measured values of 0.70 for B73 and 0.69 for br2. These results indicate that this technique is useful for real-time IAA transport monitoring in surface tissues and that this approach can be performed simultaneously with current live imaging techniques.

Sequestration of auxin by the indole-3-acetic acid-amido synthetase GH3-1 in grape berry (Vitis vinifera L.) and the proposed role of auxin conjugation during ripening

In fleshy fruit, levels of indole-3-acetic acid (IAA), the most abundant auxin, decline towards the onset of ripening. The application of auxins to immature fruit can delay the ripening processes. However, the mechanisms by which the decrease in endogenous IAA concentrations and the maintenance of low auxin levels in maturing fruit are achieved remain elusive. The transcript of a GH3 gene (GH3-1), encoding for an IAA-amido synthetase which conjugates IAA to amino acids, was detected in grape berries (Vitis vinifera L.). GH3-1 expression increased at the onset of ripening (veraison), suggesting that it might be involved in the establishment and maintenance of low IAA concentrations in ripening berries. Furthermore, this grapevine GH3 gene, responded positively to the combined application of abscisic acid and sucrose and to ethylene, linking it to the control of ripening processes. Levels of IAA-aspartic acid (IAA-Asp), an in vitro product of recombinant GH3-1, rose after veraison and remained high during the following weeks of the ripening phase when levels of free IAA were low. A similar pattern of changes in free IAA and IAA-Asp levels was detected in developing tomatoes (Solanum lycopersicum Mill.), where low concentrations of IAA and an increase in IAA-Asp concentrations coincided with the onset of ripening in this climacteric fruit. Since IAA-Asp might be involved in IAA degradation, the GH3 catalysed formation of this conjugate at, and after, the onset of ripening could represent a common IAA inactivation mechanism in climacteric and non-climacteric fruit which enables ripening.

Effects of in vitro subculture on the physiological characteristics of adventitious root formation in microshoots of Castanea mollissima cv. ‘yanshanhong’

Microshoots of Castanea mollissima cv. ‘yanshanhong’ in vitro acquired an enhanced rooting capability with increasing numbers of subculture. In this study, we investigated the effect of successive subculture on adventitious root formation in vitro by the determination of the endogenous hormone level and the enzyme activity. The levels of indoleacetic acid (IAA), abscisic acid (ABA), cytokinins (CTK) and gibberellic acid (GA3) were determined by high performance liquid chromatography (HPLC), and the activities of indoleacetic acid oxidase (IAAO), peroxidase oxidase (POD), and polyphenol oxidase (PPO) were measured by ultraviolet-spectrophotometer assay after the induction of rooting at 2nd, 4th, 6th and 8th subculture. The relationships between physiological characteristics and subculture numbers or rooting rate were as follows: The levels of endogenous IAA in microshoots gradually increased, and endogenous levels of ABA, CTK and GA3 in microshoots decreased slightly after serial subcultures. The level of IAA was highly correlated with subculture numbers and rooting rates. The ratios of IAA/ABA and IAA/CTK both acutely raised with increasing rooting rate during successive subcultures and had high correlations with rooting rate. The activity of IAAO and POD are significantly negatively related with subculture numbers, and the activity of PPO increased after subcultures.

SRD1 is involved in the auxin-mediated initial thickening growth of storage root by enhancing proliferation of metaxylem and cambium cells in sweetpotato (Ipomoea batatas)

A sweetpotato (Ipomoea batatas cv. ‘Jinhongmi’) MADS-box protein cDNA (SRD1) has been isolated from an early stage storage root cDNA library. The role of the SRD1 gene in the formation of the storage root in sweetpotato was investigated by an expression pattern analysis and characterization of SRD1-overexpressing (ox) transgenic sweetpotato plants. Transcripts of SRD1 were detected only in root tissues, with the fibrous root having low levels of the transcript and the young storage root showing relatively higher transcript levels. SRD1 mRNA was mainly found in the actively dividing cells, including the vascular and cambium cells of the young storage root. The transcript level of SRD1 in the fibrous roots increased in response to 1000 μM indole-3-acetic acid (IAA) applied exogenously. During the early stage of storage root development, the endogenous IAA content and SRD1 transcript level increased concomitantly, suggesting an involvement of SRD1 during the early stage of the auxin-dependent development of the storage root. SRD1-ox sweetpotato plants cultured in vitro produced thicker and shorter fibrous roots than wild-type plants. The metaxylem and cambium cells of the fibrous roots of SRD1-ox plants showed markedly enhanced proliferation, resulting in the fibrous roots of these plants showing an earlier thickening growth than those of wild-type plants. Taken together, these results demonstrate that SRD1 plays a role in the formation of storage roots by activating the proliferation of cambium and metaxylem cells to induce the initial thickening growth of storage roots in an auxin-dependent manner.

Rhizobacterial potential to alter auxin content and growth of Vigna radiata (L.)

Potential of non-symbiotic plant growth promoting rhizobacteria (PGPR) to influence the endogenous indole-3-acetic acid (IAA) content and growth of Vigna radiata (L.) was evaluated. The bacterial strains used belonged to Pseudomonas, Escherichia, Micrococcus and Staphylococcus genera. All strains were able to produce IAA (1.16–8.22 μg ml−1) in the presence of 1,000 μg ml−1 of l-tryptophan as revealed by gas chromatography and mass spectrometric (GC–MS) analysis. However, strains exhibited variable results for other growth promoting traits such as phosphate solubilization and siderophore or hydrogen cyanide production. Bacterial IAA production showed significant positive correlation with endogenous IAA content of roots (r = 0.969; P = 0.01) and leaves (r = 0.905; P = 0.01) under axenic conditions. Bacterization of V. radiata seeds significantly enhanced shoot length (up to 48.10%) and shoot fresh biomass (up to 43.80%) under fully axenic conditions. Bacterial strains applied under wire-house conditions also improved shoot length, number of pods, and grain weight up to 58, 65, and 17.15% respectively, over control. Hence, free living (non-symbiotic) PGPR have the ability to influence endogenous IAA content and growth of leguminous plants.

Growth promotion and protection against salt stress by Pseudomonas putida Rs-198 on cotton

The strain Rs-198 isolated from alkaline soil was investigated and identified as Pseudomonas putida on the basis of its physiological and biochemical properties as well as its 16S rDNA sequence analysis. The effects of the strain Rs-198 on cotton seedling growth under salt stress were studied. The results indicated that Rs-198 could protect against salt stress and promote cotton seedling growth. After treatment with Rs-198, the germination rate and healthy stand of cotton were increased by 23.8% and 30.7%, respectively. Individual plant height, fresh weight and dry weight of cotton seedling were increased by 12.8%, 30.7% and 10.0%, respectively as compared to the control (CK). In the fields, Rs-198 also exhibited the ability to increase the cotton's germination rate and healthy stand, which were 16.0% and 22.4% higher than that of CK. Further analysis showed that Rs-198 could increase the absorption of the Mg 2+, K + and Ca 2+ and decrease the uptake of the Na + from the soil and also improve the production of endogenous indole acetic acid (IAA) content and reduce the abscisic acid (ABA) content of cotton seedling under salt stress.

Interactive effects of α-NAA and UV-B radiation on the endogenous hormone contents and growth of Trichosanthes kirilowii Maxim seedlings

The impact of UV-B radiation on endogenous hormones in plants has recently drawn attention from researchers. The mechanism for reduced stem elongation by UV-B might be due to changes in the phytohormone levels, especially IAA, which plays a role in stem elongation. In this study, effects of UV-B radiation on Trichosanthes kirilowii Maxim ( T. kirilowii) seedlings in greenhouse-grown plants were investigated. The results indicated that: (1) In comparison to controls, exposure to 0.029 Jm −2 s −1. UV-B radiation led to accumulation of endogenous abscisic acid (ABA) and zeatinriboside (ZR) in the plant contents, and decreased contents of endogenous indole-3-acetic acid (IAA) and gibberellic acid (GA 1/3). Exposure to UV-B radiation reduced the height and leaf area of plants. As a result, total biomass (plant dry weight) was lower. (2) In comparison to controls, addition of 2 mg l −1 α-naphthaleneacetic acid (α-NAA) slightly increased the contents of IAA, GA 1/3 and ZR, and decreased the content of ABA in leaves. This addition of α-NAA significantly increased plant height and leaf area, but only slightly increased total biomass. (3) Addition of α-NAA to UV-B-exposed plants: increased the content of endogenous IAA, GA 1/3 and ZR; decreased accumulation of endogenous ABA; and increased plant height and leaf area in comparison to plants that only were exposed to UV-B. Moreover, total biomass increased slightly. This suggests that addition of α-NAA may compensate to a certain extent for the lack of IAA resulting from UV-B radiation; it also increases the content of GA 1/3 and ZR, decreases the accumulation of ABA, and promotes the growth of plants.

Coronatine‐induced lateral‐root formation in cotton (Gossypium hirsutum) seedlings under potassium‐sufficient and ‐deficient conditions in relation to auxin

AbstractA large root system plays a decisive role in potassium (K)‐acquisition efficiency of cotton. Coronatine (COR), a non‐host‐specific phytotoxin, may affect the auxin level in plants and might therefore be useful in regulating lateral‐root (LR) development. Our objectives were (1) to examine the effects of COR on root development, especially the LR formation in hydroponically grown cotton seedlings, and (2) to explore possible mechanisms involved. The results showed that K deficiency (0.05 mM) significantly reduced LR formation in cotton seedlings, possibly due to the decrease of endogenous indole acetic acid (IAA) in roots by more than half. Following the application of 10 nM COR, the LRs significantly increased by 26% in K‐sufficient (0.5 mM) solution and by 95% in K‐deficient solution. Although COR did not increase the free IAA level in the primary root, the polar auxin‐transport inhibitor N‐1‐naphthylphthalamic acid (NPA) decreased its stimulating effects on LR formation by 25%–30%, suggesting that the COR‐induced LR formation was independent of increased auxin level but likely associated with auxin transport. Treatment of plants with 1‐naphthalene acetic acid (NAA) increased LR formation at NAA concentrations of 100 nM, but had no effect at 10 nM. In the presence of 1 nM COR, however, NAA increased LR formation at 10 nM concentrations. This indicates that LR formation due to COR possibly involves changes in auxin sensitivity. In addition, the shorter LRs of COR‐treated seedlings were clearly restored when COR was removed from solutions for 12 d, and the total root length, total root surface area as well as K uptake increased significantly, suggesting that COR may be potentially useful for enhancing the K‐acquisition efficiency of cotton seedlings.

Effects of Potassium Deficiency on Root Growth of Cotton Seedlings and Its Physiological Mechanisms

For the purpose of dissecting the mechanism of root growth in response to potassium (K) deficiency in cotton ( Gossypium hirsutum L.), young seedlings of NuCOTN99B grown in half-strength modified Hoagland's solution with low K nutrient (0.05 mmol L −1) were investigated for the root configuration, content of endogenous free indole acetic acid (IAA), and amount of ethylene released from the roots 4 d after treatment. Compared with the treatment with moderate K nutrient (0.50 mmol L −1, control), the K deficient treatment significantly inhibited root length and the formation of lateral roots. The reduced lateral roots mainly resulted from the shortened branched root zone, and there was no change in the lateral root density. Under K deficient condition, the greatest reductions for root length, total root surface area, and root volume occurred in fine roots (0.05 mm ≤ diameter < 0.20 mm), followed by the coarse roots (diameter [.tau] 0.45 mm) and the middle roots (0.25 mm ≤ diameter < 0.45 mm). The fine roots were more important in nutrient uptake than the middle and the coarse roots. Thus, the K starving damage was greater in cotton seedlings than the growth inhibition of roots. When the cotton seedlings exposed to K deficient media for 4 d and 10 d, the total root length and the total root surface area were 35.7–38.0% and 47.7–50.6% of the values of the control plants; whereas the K accumulation was approximately 25% and 16% to the control values, respectively. As expected, the endogenous free IAA content in the roots grown in K deficient media reduced by 50%, whereas the amount of ethylene released from roots increased by nearly 6-fold, which partially explained the inhibition of lateral root formation and root elongation by K deficiency.

Auxin regulation in the interaction between Rice stripe virus and rice

AbstractThe expression of the YUCAA1 gene and the amount of endogenous indole acetic acid (IAA) in rice (Oryza sativa subsp. japonica) plants and rice suspension cells infected by Rice stripe virus (RSV) were investigated by real-time reverse transcriptase–polymerase chain reaction (RT-PCR) and high-performance liquid chromatography, respectively. The results showed that the expression of the YUCAA1 gene and the amount of endogenous IAA increased at various times (16, 32, 48 and 64 h) after infection of rice suspension cells by RSV. In rice plants infected with RSV, the expression of the YUCAA1 gene and the amount of endogenous IAA increased, in comparison with healthy rice plants, at 4–8 days after infection, and decreased at 12 and 16 days. These results indicated that RSV infection could regulate auxin biosynthesis in rice. Additionally, the expression of the RSV gene CP increased 2.9 times in rice plants after they were treated with a KPSC buffer to deplete the endogenous auxins, and decreased 45% after treatment with 30 μmol/l IAA. All of these results suggest that auxin may play a role in RSV replication in rice plants.

Auxin production by plant associated bacteria: impact on endogenous IAA content and growth ofTriticum aestivumL.

The aim of this study was to investigate the potential of bacterial strains of Bacillus, Pseudomonas, Escherichia, Micrococcus and Staphylococcus genera associated with wild herbaceous flora to enhance endogenous indole-3-acetic acid (IAA) content and growth of Triticum aestivum var. Inqalab-91. Gas chromatography and mass spectrometric (GC-MS) analysis revealed that bacterial strains produced 0.6-8.22 microg IAA ml(-1) in the presence of L-tryptophan. Plant microbe experiments showed a significant positive correlation between auxin production by bacterial strains and endogenous IAA content of T. aestivum for GC-MS (r = 0.618; P = 0.05) and colorimetric analysis (r = 0.693; P = 0.01). Similarly, highly significant positive correlation for shoot length (r = 0.627; P = 0.01) and shoot fresh weight (r = 0.626; P = 0.01) was observed with auxin production under axenic conditions. Bacterial inoculations also enhanced shoot length (up to 29.16%), number of tillers (up to 97.35%), spike length (up to 25.20%) and seed weight (up to 13.70%) at final harvest. Bacterial strains have the ability to increase the endogenous IAA content and growth of T. aestivum var. Inqalab-91. Microbial strains of wild herbaceous flora can be effectively used to enhance the growth and yield of agronomically important crops.

Changes in endogenous hormone levels and redox status during enhanced adventitious rooting by rare earth element neodymium of Dendrobium densiflorum shoot cuttings

The effects of neodymium nitrate (Nd 3+) on the adventitious rooting of Dendrobium densiflorum shoot cuttings were studied. The addition of Nd 3+ (5 μmol/L) to culture medium significantly increased rooting frequency. Histological investigation showed that Nd 3+ did not change the process of root initiation. Nd 3+ did not influence total endogenous cytokinin levels, but significantly increased the level of endogenous indole-3-acetic acid (IAA) in the base of shoot cuttings. Compared to the control, the ratio of IAA/cytokinins was very high in the Nd 3+ treatment. These results suggested that the enhanced rooting frequency may be related to the increase in endogenous IAA level in Nd 3+ treatment. Analysis of enzyme activities showed that the enhanced accumulation of the endogenous IAA by Nd 3+ should not be attributed to inhibition of IAA decomposition by IAA oxidase or promotion of cytokinin decomposition by cytokinin oxidase. Besides, Nd 3+ increased the ratio of reduced glutathione (GSH) and oxidized glutathione (GSSG) in the process of adventitious rooting while the ratio of ascorbate (ASC) to dehydroascorbate (DHA) was not affected.

Exogenously applied melatonin stimulates root growth and raises endogenous indoleacetic acid in roots of etiolated seedlings of Brassica juncea

Exogenous melatonin was applied to etiolated seedlings of wild leaf mustard (Brassica juncea) and the effect on root growth and endogenous indole-3-acetic acid (IAA) levels determined. The results show that 0.1microM melatonin has a stimulatory effect on root growth, while 100microM is inhibitory. Furthermore, the stimulatory effect was only detectable in young seedlings (2-d old). Older seedlings (4-d old) appear to be less susceptible to both the stimulatory and the inhibitory effect of melatonin. Exogenous application of 0.1microM melatonin also raised the endogenous levels of free IAA in roots, while higher concentrations had no significant effect. The specific mechanism that causes exogenous melatonin to increase the amount of free IAA in roots, paired with a stimulation of root growth, remains to be uncovered.

Study on the extraction, purification and quantification of jasmonic acid, abscisic acid and indole‐3‐acetic acid in plants

Jasmonic acid (JA), abscisic acid (ABA) and indole-3-acetic acid (IAA) are important plant hormones. Plant hormones are difficult to analyse because they occur in small concentrations and other substances in the plant interfere with their detection. To develop a new, inexpensive procedure for the rapid extraction and purification of IAA, ABA and JA from various plant species. Samples were prepared by extraction of plant tissues with methanol and ethyl acetate. Then the extracts were further purified and enriched with C(18) cartridges. The final extracts were derivatised with diazomethane and then measured by GC-MS. The results of the new methodology were compared with those of the Creelman and Mullet procedure. Sequential elution of the assimilates from the C(18 )cartridges revealed that IAA and ABA eluted in 40% methanol, while JA subsequently eluted in 60% methanol. The new plant hormone extraction and purification procedure produced results that were comparable to those obtained with the Creelman and Mullet's procedure. This new procedure requires only 0.5 g leaf samples to quantify these compounds with high reliability and can simultaneously determine the concentrations of the three plant hormones. A simple, inexpensive method was developed for determining endogenous IAA, ABA and JA concentrations in plant tissue.

Maturation of somatic embryos in two embryogenic cultures of Picea morrisonicola Hayata as affected by alternation of endogenous IAA content

Embryogenic culture lines T4 and T2 were initiated from two mature zygotic embryos of Picea morrisonicola Hay. Mature somatic embryos (SEs) were produced in culture line T2 but not in line T4 after 8-week abscisic acid (ABA) treatment. High performance liquid chromatography (HPLC) analysis of the endogenous indole-3-acetic acid (IAA) content has shown 7.5 times higher IAA production in T4 line than in T2 line during the proliferation phase. However, after ABA incubation the line T4 produced much less IAA than line T2. The application of an anti-auxin, 2,3,5-triiodobenzoic acid (TIBA) or 2-(4-chlorophenoxy)-2-methylpropionic acid (PCIB) induced culture line T4 to produce mature SEs. Both 1 μM TIBA and 5 μM PCIB increased the production of stage 2 SEs in T4 culture line when cultures were treated during the proliferation stage for 8 weeks. Occasionally cotyledonary (stage 3) SEs were even produced from treated T4 culture line. Both chemicals have also been demonstrated to significantly decrease the amount of IAA in the treated T4 and T2 embryogenic lines. However the decrease of the IAA level was not beneficial for SE production in the T2 embryogenic line. These results indicated the importance of endogenous IAA level in manipulating the process of SE maturation in spruce embryogenic cultures.

Cross‐talk between gibberellin and auxin in development of Populus wood: gibberellin stimulates polar auxin transport and has a common transcriptome with auxin

Both indole acetic acid (IAA) and gibberellins (GAs) stimulate cell and organ growth. We have examined GA/IAA cross-talk in cambial growth of hybrid aspen (Populus tremulaxtremuloides). Decapitated trees were fed with IAA and GA, alone and in combination. Endogenous hormone levels after feeding were measured, by mass spectrometry, in the stem tissues below the point of application. These stem tissues with defined hormone balances were also used for global transcriptome analysis, and the abundance of selected transcripts was measured by real-time reverse-transcription polymerase chain reaction. By feeding isotope-labeled IAA, we demonstrated that GA increases auxin levels in the stem by stimulating polar auxin transport. This finding adds a new dimension to the concept that the endogenous GA/IAA balance in plants is determined by cross-talk between the two hormones. We also show that GA has a common transcriptome with auxin, including many transcripts related to cell growth. This finding provides molecular support to physiological experiments demonstrating that either hormone can induce growth if the other hormone is absent/deficient because of mutations or experimental treatments. It also highlights the potential for extensive cross-talk between GA- and auxin-induced responses in vegetative growth of the intact plant. The role of endogenous IAA and GA in wood development is discussed.