Indole-3-acetic Acid Treatment Research Articles

SlPP2C2 interacts with FZY/SAUR and regulates tomato development via signaling crosstalk of ABA and auxin.

Abscisic acid (ABA) signaling interacts frequently with auxin signaling when it regulates plant development, affecting multiple physiological processes; however, to the best of our knowledge, their interaction during tomato development has not yet been reported. Here, we found that type 2C protein phosphatase (SlPP2C2) interacts with both flavin monooxygenase FZY, an indole-3-acetic acid (IAA) biosynthetic enzyme, and small auxin upregulated RNA (SAUR) of an IAA signaling protein and regulates their activity, thereby affecting the expression of IAA-responsive genes. The expression level of SlPP2C2 was increased by exogenous ABA, IAA, NaCl, or dehydration treatment of fruits, leaves, and seeds, and it decreased in imbibed seeds. Manipulating SlPP2C2 with overexpression, RNA interference, and CRISPR/Cas9-mediated genome editing resulted in pleiotropic changes, such as morphological changes in leaves, stem trichomes, floral organs and fruits, accompanied by alterations in IAA and ABA levels. Furthermore, the RNA-seq analysis indicated that SlPP2C2 regulates the expression of auxin-/IAA-responsive genes in different tissues of tomato. The results demonstrate that SlPP2C2-mediated ABA signaling regulates the development of both vegetative and reproductive organs via interaction with FZY/SAUR, which integrates the cross-talk of ABA and auxin signals during development and affects the expressions of development-related genes in tomato.

A novel dual inhibitor of the angiotensin and endothelin systems for the treatment of hypertension

Hypertension, affecting nearly half of the US adult population, is a primary cause of morbidity and mortality worldwide. Despite the availability of several classes of antihypertensive medications, only 25% of patients have their blood pressure under control, highlighting the need for novel antihypertensive therapeutics with better effcacy. Among hypertensive cases, salt-sensitive and drug-resistant hypertension are particularly concerning, as they are unresponsive to a combined regimen of three or more classes of medications, including angiotensin II (Ang II) receptor blockers (ARBs), angiotensin-converting enzyme inhibitors (ACEis), and diuretics. Salt-sensitive, observed in 50% of the general and 73% of black hypertensive patients, disproportionately affects the latter, leading to significantly higher mortality. Salt-sensitive hypertension in humans, as well as in various experimental models of hypertension (e.g., Ang II-induced, Dahl-salt sensitive [DSS] rats, deoxycorticosterone acetate [DOCA]-salt hypertensive rats), is characterized by significantly elevated levels of plasma endothelin-1 (ET-1), oxidative stress, and kidney dysfunction. ET-1 is often considered a final common pathway in orchestrating cardiovascular dysfunction through a range of proinflammatory mediators such as Ang II, cytokines, hypoxia, thrombin, reactive oxygen species (ROS), oxidized LDL, and vasopressin, all of which stimulate ET-1 production. In this capacity, we report the discovery of a gut microbiota-derived metabolite, indole-3-acetic acid (IAA), that simultaneously blocks ET-1 receptors (ETAR and ETBR) and the ET-biosynthetic enzyme ECE-1. Our data demonstrate that IAA inhibits ET-1-induced constriction of resistance mesenteric arteries, ROS production in human aortic smooth muscle cells, activation of cultured endothelial cells, adhesion molecule expression, and leukocyte adhesion. IAA inhibited purified human ECE-1 and suppressed Ang-II-induced and hypoxia-elicited ET-1 production from endothelial cells in vitro. Administration of a once-daily, extended-release formulation of IAA inhibits blood pressure elevation and kidney dysfunction in both DSS and Ang II-induced hypertension. IAA treatment preserved endothelial nitric oxide (NO) production and maintained smooth muscle sensitivity to a NO donor, sodium nitroprusside. Furthermore, IAA inhibited the expression of ROS-associated proteins such as Nox2 and Nox4, reduced oxidative damages, and decreased the production of ET-1 in vivo. Overall, IAA is the first compound that, through novel dual targeting of both the angiotensin and endothelin systems, demonstrates profound antihypertensive action in both salt-sensitive and angiotensin II-induced hypertension. Thus, IAA has the potential to effectively treat hypertension that does not respond to conventional therapies. American Heart Association. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Indole-3-acetic acid ameliorates dextran sulfate sodium-induced colitis via the ERK signaling pathway.

Microbiota-derived catabolism of nutrients is closely related to ulcerative colitis (UC). The level of indole-3-acetic acid (IAA), a microbiota-dependent metabolite of tryptophan, was decreased significantly in the feces of UC patients. Thus supplementation with IAA could be a potential therapeutic method for ameliorating colitis. In this work, the protective effect of supplementation with IAA on dextran sulfate sodium (DSS)-induced colitis was evaluated, and the underlying mechanism was elucidated. The results indicated that the administration of IAA significantly relieved DSS-induced weight loss, reduced the disease activity index (DAI), restored colon length, alleviated intestinal injury, and improved the intestinal tight junction barrier. Furthermore, IAA inhibited intestinal inflammation by reducing the expression of proinflammatory cytokines and promoting the production of IL-10 and TGF-β1. In addition, the ERK signaling pathway is an important mediator of various physiological processes including inflammatory responses and is closely associated with the expression of IL-10. Notably, IAA treatment induced the activation of extracellular signal-regulated kinase (ERK), which is involved in the progression of colitis, while the ERK inhibitor U0126 attenuated the beneficial effects of IAA. In summary, IAA could attenuate the clinical symptoms of colitis, and the ERK signaling pathway was involved in the underlying mechanism. Supplementation with IAA could be a potential option for preventing or ameliorating UC.

Effect of Natural IAA Produced by Streptomyces Strain ACM37 on Seed Germination and Seedling Growth


 
 
 Biofertilizers play an important role in sustainable agriculture by improving soil fertility, crop tolerance and crop productivity. In this context, exploitation of plant growth promoting rhizobacteria with various beneficial properties is challenging. This study aimed to investigate the plant growth promoting activity of indole-3-acetic acid (IAA)-producing actinomycetes strain, Streptomyces ACM37 on the seed germination and seedling growth at early stage. The ACM37 was grown in starch-casein broth for 7 days at 28° C, 80 rpm and supplemented with 50 mg/l L- tryptophan to induce IAA production. After 7 days, IAA concentration in cell-free culture broth was quantified by following the Salkowski's method and it was 50 mg/l. Seed germination and seedling growth of cowpea (Vigna unguiculata) and rice (Oryza sativa L.) at different concentrations of IAA were estimated as % seed germination, number of roots, primary root length and length of hypocotyl. Initially, seeds were surface sterilized with 10% (v/v) NaOCl and soaked in 10, 20, 30, 40 and 50 mg/l crude IAA preparations for 1 h at 30° C. As controls, seeds were soaked in sterilized distilled water (SDW) and 50 mg/l synthetic IAA. Ten seeds per each treatment with three replicates were placed on 0.8% (w/v) water-agar in Petri plates and incubated in dark at 30° C. The % seed germination of ACM37-IAA-treated cowpea and rice seeds was enhanced at all concentrations compared to SDW and synthetic IAA treatments after 3 days. The highest 100% germination of cowpea was given at 10 mg/l IAA while it was 96.67±3.33% in>30 mg/l IAA in rice. Similarly, there was a significant (P<0.05) increase in primary root length and number of lateral roots in cowpea at 10 mg/l of ACM37-IAA. Overall, ACM37 showed significant plant growth promotion in cowpea at low concentration (10 mg/l) of IAA whereas there was a significant (P<0.05) reduction at high concentrations (>10 mg/l). On the other hand, there was no apparent increase in all growth parameters except seed germination in rice at all concentrations. It appears that high concentrations of ACM37-IAA may be required to promote plant growth in rice. Overall results highlight that plant growth promotion activity of ACM37 varies at different IAA concentrations and different plant species, probably between monocot and dicot species. Therefore, ACM37 has potential application as a plant growth promoting agent in biofertilizers and plant growth inhibiting agent in bioherbicides at certain IAA concentrations.
 Keywords: Actinomycetes, Biofertilizer, Bioherbicide, IAA
 
 

The Growth Response of Rendeu (<i>Staurogyne elongata</i> (Neese) Kuntze) to Shoot Pruning and Its Propagation by Shoot Cutting

Rendeu (Staurogyne elongata (Neese) Kuntze) is a native Indonesian plant used as food and traditional medicine in the daily life of the people residing around Gunung Halimun-Salak National Park. Due to the potential source of herbal-based medicines and traditional food in the long-run purposes, the proper method of its propagation is required, so that Rendeu can be conserved and utilised sustainably. This study employed two research designs. First, a completely randomized design with pruning and IAA (indole-3 acetic acid) treatment was used for seedling growths. Second, plant propagation applied a factorial randomized block design: planting media types and plant growth regulator (PGR) (rootone F) treatment. Observation included the number of buds, number of leaves, number of flowers, plant biomass, root length, and relative chlorophyll content using the SPAD tool. The data were analysed using ANOVA (SPSS ver. 17.0), followed by Pearson correlation analysis. The results showed that applying IAA and leaf pruning could increase the number of buds, the number of leaves and the fresh weight of S. elongata plants compared to the control plant. The addition of rootone increased the growth of Rendeu shoot cuttings, shown in all growth parameters and chlorophyll content. Humus was the best media for Rendeu’s growth among all planting medium. Planting media affected the increase in the number of leaves and the number of buds of S. elongata significantly. The interaction of planting media and PGR somewhat influenced root length and total leaf chlorophyll. The growth and production of S. elongata increased with the time of planting.

Foliar spraying of indoleacetic acid (IAA) enhances the phytostabilization of Pb in naturally tolerant ryegrass by limiting the root-to-shoot transfer of Pb and improving plant growth.

Exogenous addition of IAA has the potential to improve the metal tolerance and phytostabilization of plants, but these effects have not been systematically investigated in naturally tolerant plants. Ryegrass (Lolium perenne L.) is a typical indigenous plant in the Lanping Pb/Zn mining area with high adaptability. This study investigated the phytostabilization ability and Pb tolerance mechanism of ryegrass in response to Pb, with or without foliar spraying of 0.1 mmol L-1 IAA. The results indicated that appropriate IAA treatment could be used to enhance the phytostabilization efficiency of naturally tolerant plants. Foliar spraying of IAA increased the aboveground and belowground biomass of ryegrass and improved root Pb phytostabilization. Compared to Pb-treated plants without exogenous IAA addition, Pb concentration in the shoots of ryegrass significantly decreased, then increased in the roots after the foliar spraying of IAA. In the 1,000 mg kg-1 Pb-treated plants, Pb concentration in the shoots decreased by 69.9% and increased by 79.1% in the roots after IAA treatment. IAA improved plant growth, especially in soils with higher Pb concentration. Foliar spraying of IAA increased shoot biomass by 35.9% and root biomass by 109.4% in 1,000 mg kg-1 Pb-treated plants, and increased shoot biomass by 196.5% and root biomass by 71.5% in 2,000 mg kg-1 Pb-treated plants. In addition, Pb stress significantly decreased the content of photosynthetic pigments and anti-oxidase activities in ryegrass, while foliar spraying of IAA remedied these negative impacts. In summary, foliar spraying of IAA could increase the biomass and improve the Pb tolerance of ryegrass.

Colon-Targeted Delivery of Indole Acetic Acid Helps Regulate Gut Motility by Activating the AHR Signaling Pathway.

Intestinal peristalsis is vital for gastrointestinal physiology and host homeostasis and is frequently dysregulated in intestinal disorders. Gut microbiota can regulate gut motility, especially through the tryptophan metabolism pathway. However, the role of indoles as microbial tryptophan metabolites in colonic function requires further exploration. Here, we show that the delivery of indole acetic acid (IAA) targeting the colon can improve gut motility by activating the aryl hydrocarbon receptor (AHR). To achieve colon-targeted delivery, Eudragit S-100 (ES) and chitosan (CS) were used as drug carriers. After optimisation, IAA-loaded ES-coated CS nanoparticles exhibited an encapsulation efficiency of 83% and a drug-loading capacity of 16%. These nanoparticles exhibited pH-dependent characteristics and remained stable in acidic conditions and the upper intestine. In simulated intestinal fluid (pH 7.4) and colonic lumen, considerable amounts of IAA were released after approximately 4 h. Compared with free IAA, the nanoparticles exerted enhanced therapeutic effects on gut movement disorders induced by loperamide. The efficacy of IAA treatment was attributable to the activation of the AHR signalling pathway and increased levels of AHR agonists. Furthermore, the oral administration of IAA-loaded nanoparticles promoted serotonin secretion and maintained the intestinal barrier function. The experimental outcomes demonstrate the efficiency of the proposed colon-specific delivery system and highlight the role of IAA, produced by gut microbiota metabolism, in regulating gut peristalsis through AHR activation.

Physiological and transcriptomic analysis of IAA-induced antioxidant defense and cell wall metabolism in postharvest mango fruit

Mango fruit tend to oxidize and senescence rapidly after harvesting, significantly reducing their commercial value. This study investigated the effect of exogenous auxin indole-3-acetic acid (IAA) on fruit quality, antioxidant system, and cell wall metabolism of mango fruit during storage. The results showed that the 1.0 mM IAA treatment delayed weight loss and maintained the firmness, pH and contents of total soluble solids (TSS) and titratable acidity (TA) of the mango fruit. The 1.0 mM IAA treatment increased the peroxidase (POD) and phenylalanine ammonia-lyase (PAL) activities and the ascorbic acid (AsA) and total phenols (TP) contents but decreased the polyphenol oxidase (PPO) activity in postharvest mango fruit. Moreover, beta-galactosidase (β-Gal) and polygalacturonase (PG) activities were increased, but the pectinesterase (PME) activity was decreased in the IAA-treated fruit. Transcriptome analysis showed that the differentially expressed genes (DEGs) in the IAA vs. control groups were mainly associated with oxidative stress responses, cell wall metabolism, and transcription factors (TFs). The IAA treatment upregulated the antioxidant-related genes (SOD, CAT1, PODs, GSTs, Prxs, and Trxs) and MYB TFs, and downregulated cell wall metabolism-related genes (PG, PME31 and two PME63) and 11 ethylene-responsive transcription factors (ERFs). These results suggested that exogenous IAA could improve the antioxidant system and maintain the storage quality of mango fruit by regulating gene expression and metabolic pathways. The results provide insights into the mechanisms involved in IAA-mediated delayed ripening and senescence of mango fruit.

Abstract P318: INDOLE-3 ACETIC ACID: A NOVEL DUAL-ACTION INHIBITOR OF THE ENDOTHELIN SYSTEM FOR TREATING HYPERTENSION

Elevated levels of endothelin-1 (ET-1) stimulate potent vasoconstriction, free radical production, oxidative stress, and vascular inflammation, which are often present in salt-sensitive hypertension, pulmonary hypertension, drug-resistant hypertension, and hypertension among African Americans. There is currently no known drug that simultaneously targets both ET-1 receptors (ETRs) and the ET-1 synthesizing enzyme ECE-1, even though dual targeting of the ET system could lead to a new generation of drug molecules with improved therapeutic outcome. Using an integrated in vitro, in vivo and in silico approaches, here we report the discovery of indole-3 acetic acid (IAA) as an inhibitor of both ET-1 receptors and ECE-1. IAA is produced in the human body via tryptophan metabolism by gut microbiota. Our data demonstrates that IAA concentration-dependently inhibits ET-1-evoked vasoconstriction in rat resistance mesenteric arteries and ET-1-stimulated reactive oxygen species (ROS) production in smooth muscle cells (SMCs). Furthermore, IAA suppresses ET-1-induced endothelial cell (EC) activation, adhesion molecule overexpression, and leukocyte adhesion. IAA inhibits ET-1-stimulated, ET A R- and ET B R-mediated increases in [Ca 2+ ] i . Intriguingly, IAA produces a concentration-dependent inhibition of purified human ECE-1. Treatment of Dahl salt-sensitive (DSS) hypertensive rats, a model of augmented ET-1 signaling, with an oral extended-release formulation of IAA significantly inhibits blood pressure elevation in high-salt diet-fed (HSD) DSS rats. IAA-treated DSS arteries show intact acetylcholine- and sodium nitroprusside-induced vasodilation, suggesting that IAA preserves endothelial and smooth muscle function, respectively. IAA treatment also prevents arterial remodeling, oxidative stress, and kidney dysfunction in HSD DSS rats. Overall, our study identifies IAA as the first-in-class dual-action inhibitor of ETRs and ECE-1, which produces profound antihypertensive effect in vivo. IAA could also be therapeutically useful for other cardiovascular diseases in which ET-1 signaling is implicated.

Respuesta agronómica y metabolómica de plántulas de melón (Cucumis melo L.) bajo la aplicación de altas concentraciones de ácido indol-3-acético

Indole-3-acetic acid (IAA) is the main auxin in plants and controls various physiological and biochemical processes such as cell elongation and division, tissue differentiation, responses to light and gravity, and response to biotic stress and abiotic. Therefore, the objective of the work was to evaluate the effect of foliar application of high concentrations of IAA (0.5, 1, 2, and 3 mM) plus a control (distilled water) on agronomic and metabolomic variables in melon seedlings. The results indicate that for agronomic variables, IAA at a concentration of 0.5 mM improved height by 20.98 %, compared to the control, and after 1 mM it began to decrease as IAA concentration increased. For the total fresh and dry biomass, it can be seen that the control and the 0.5 mM concentration were statistically equal, however, from 1 mM the biomass began to decrease as the IAA concentration increased. Regarding the biomolecules, an increase in chlorophylls (a, b and total), flavonoids, antioxidant capacity and proteins is observed as the IAA concentration rises. The 0.5, 1, and 2 mM IAA treatments increased the concentration of carotenoids by 11.76, 11.76 and 8.82 %, respectively, compared to the control, however, with the 3 mM concentration they began to decrease, but still exceeded the control. It is concluded that from the concentration of 1 mM of IAA the agronomic characteristics of the seedlings began to decrease, therefore, it is recommended that concentrations below 0.5 mM of IAA are used to be able to elucidate how lower concentrations work. Regarding the metabolomic variables, they increased as the IAA concentration.

The Effect of IAA Phytohormone (Indole-3-Acetic Acid) on the Growth, Lipid, Protein, Carbohydrate, and Pigment Content in Euglena sp.

Nowadays, energy consumption is massively increasing in the world. The production of biofuels from microalgae has received considerable attention recently and has the potential to supplant fossil fuels. Recent research focuses on developing the potential of microalgae as an alternative fuel. This research will focus on evaluating the effect of indole-3-acetic acid (IAA) on the growth and metabolite production of Euglena sp. The methods used in this study started with a medium preparation and cultivation using IAA treatment, where the treatment used controlled IAA 5 g/L, IAA 10 g/L, and IAA 15 g/L with three biological repetitions. Optical density (OD) was measured using a spectrophotometer (OD680), biomass was measured using the gravimetry method, lipid was calculated using Bligh and Dyer (1995), the protein was measured using Bradford solution, carbohydrates were measured using phenol sulfuric acid, and pigments were extracted using methanol and measured using a spectrophotometer. According to the findings of this study, IAA 5 g/L can enhance the growth rate. For biomass, the best result was at 10 g/L of IAA (2.216 g/L ± 0.284). Meanwhile, carbohydrates, proteins, and lipids were higher in IAA 15 g/L. Chlorophyll a, b, and total carotenoid were higher in 5 g/L of IAA. The results obtained in this study showed that the IAA hormone increased the growth and metabolite content of Euglena sp.

IAA regulated levels of endogenous phytohormones in relation to chilling tolerance in cold-stored peaches after harvest

The effects of indoleacetic acid (IAA) treatment on chilling injury and endogenous phytohormones in peach fruit were studied. The results showed that IAA treatment decreased chilling injury index of cold-stored peaches, effectively maintaining fruit firmness and reducing the electrical conductivity level. IAA treatment upregulated the expression of IAA biosynthetic gene PpMES and signaling pathway gene PpSAUR, but reduced the transcript abundance of IAA degradative genes PpDAO, PpGH3, and PpIAMT, leading to endogenous IAA accumulation in treated peaches. Meanwhile, after IAA treatment, contents of melatonin and γ-aminobutyric acid (GABA) were also increased which was associated with the upregulation of their anabolic genes and downregulation in GABA catabolic genes. In addition, the levels of abscisic acid (ABA) and gibberellin (GA) were reduced in treated peaches due to its modification in the transcript levels of ABA and GA metabolic genes. Collectively, IAA could alleviate the symptoms of chilling injury in peach fruit via regulating contents of endogenous phytohomones such as IAA, melatonin, GABA and GA.

Exogenous IAA application affects the specific characteristics of fluoranthene distribution in Arabidopsis

Indole-3-acetic acid (IAA) is a crucial growth regulator involved in the accumulation of polycyclic aromatic hydrocarbons (PAHs). However, the precise physiological and molecular mechanisms underlying IAA-mediated plant growth and PAH accumulation are not yet fully understood. In this study, two distinct IAA-sensitive genotypes of Arabidopsis thaliana (wild type and Axr5 mutant) were chosen to investigate the mechanisms of fluoranthene (Flu) uptake and accumulation in plant tissues (roots and leaves) through physiological and molecular analyses. The results revealed that the Flu concentration in Axr5 leaves was significantly higher than that in wild-type (WT) leaves. In roots, the Flu content decreased significantly with increasing IAA treatment, while no significant changes were observed with lower IAA treatment. Principal component analysis demonstrated that Flu accumulation in Arabidopsis roots was associated with IAA concentrations, whereas Flu accumulation in leaves was dependent on the genotype. Moreover, Flu accumulation showed a positive correlation with the activity of glutathione S-transferase (GST) and root length and a positive correlation with catalase (CAT) and peroxidase (POD) activity in the leaves. Transcriptome analysis confirmed that the expression of the ethylene-related gene ATERF6 and GST-related genes ATGSTF14 and ATGSTU27 in roots, as well as the POD-related genes AtPRX9 and AtPRX25 and CAT-related gene AtCAT3 in leaves, played a role in Flu accumulation. Furthermore, WRKY transcription factors (TFs) in roots and NAC TFs in leaves were identified as important regulators of Flu accumulation. Understanding the mechanisms of Flu uptake and accumulation in A. thaliana provides valuable insights for regulating PAH accumulation in plants.

The Effect of IAA and BAP on Root Induction of Cattleya Orchids

Orchid is an ornamental plant commodity that has an important meaning in international trade. Until now, orchids are still the center of attention of farmers and lovers of ornamental plants, because of their bright potential as cut flowers and potted plants. The popular and widespread type of orchid is Cattleya sp. The Cattleya orchid is also called the queen of orchids because of its colorful flowers. Cattleya sp. orchids take a long time to propagate by seed, about 4 to 7 years, so other methods are needed to deal with them. Tissue culture is a method for isolating plant parts such as cells, tissues or organs, and cultivating them in an aseptic environment. The purpose of this study was to determine the optimal interaction of growth regulators indole acetic acid (IAA), benzyl amino purine (BAP), and their interactions with the root induction of Cattleya sp. Cytokinins interact with auxin in determining the direction of cell differentiation. In this research method, differences in concentrations of indole acetic acid (IAA: 0, 2, 4, 6 ppm) and concentrations of benzyl amino purine (BAP: 0, 0, 5, 1 ppm) were carried out. Parameters observed were the number of roots and root length. Data were analyzed descriptively and inferentially using ANOVA. The highest number of roots was obtained in the treatment medium containing 0.5 ppm BAP and 6 ppm IAA, which was 6.33. The highest root length was found in the B0I4 treatment (BAP 0 + IAA 4 ppm). The results of the analysis of the interaction variance between the IAA treatment and the BAP treatment were 0.005, meaning that there was a significant effect of the combination of IAA and BAP on the leaf length of Cattleya sp.

Plant-Derived Smoke Mitigates the Inhibitory Effects of the Auxin Inhibitor 2,3,5-Triiodo Benzoic Acid (TIBA) by Enhancing Root Architecture and Biochemical Parameters in Maize.

The present study was designed to investigate and compare the effects of plant-derived smoke (PDS) and auxin (IAA and IBA) on maize growth under the application of 2,3,5-triiodo benzoic acid (TIBA). For this purpose, indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA), each at a concentration of 10 ppm, along with PDS at a ratio of 1:500 (v/v) were used alone and in combination with 10 ppm of TIBA. The results indicate that the germination percentage (%) of maize seeds was enhanced under IAA, IBA and PDS treatment. However, IAA and IBA resulted in reduced germination when applied in combination with TIBA. Importantly, the germination percentage (%) was improved by PDS under TIBA treatment. The analysis of seedling height, length of leaves, and number of primary, seminal and secondary/lateral roots showed improvement under individual treatments of IAA and IBA, PDS and PDS + TIBA treatment, while these values were reduced under IAA + TIBA and IBA + TIBA application. Chlorophyll content, total soluble sugars and antioxidative enzymatic activity including POD and SOD increased in seedlings treated with PDS alone or both PDS and TIBA, while in seedlings treated with IAA and TIBA or IBA and TIBA, their levels were decreased. APX and CAT responded in the opposite way-under IAA, IBA and PDS treatment, their levels were found to be lower than the control (simple water treatment), while TIBA treatment with either IAA, IBA or PDS enhanced their levels as compared to the control. These results reveal that PDS has the potential to alleviate the inhibitory effects of TIBA. This study highlights the role of PDS in preventing TIBA from blocking the auxin entry sites.

Effects of exogenous indole-3-acetic acid on the density of trichomes, expression of artemisinin biosynthetic genes, and artemisinin biosynthesis in Artemisia annua.

Artemisinin is the most practical medication for the treatment of malaria, but is only very minimally synthesized in Artemisia annua, significantly less than the market needs. In this study, indole-3-acetic acid (IAA) was used to investigate its effects on trichomes, artemisinin accumulation, and biosynthetic gene expression in A. anuua. The results showed that exogenous IAA could contribute to the growth and development of A. annua and increase the density of trichomes. Analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS) indicated that artemisinin and dihydroartemisinic acid (DHAA) contents were increased by 1.9-fold (1.1mg/g) and 2.1-fold (0.51mg/g) after IAA treatment in comparison with control lines (CK), respectively. Furthermore, quantitative real-time PCR results showed that AaADS, AaCYP71AV1, AaALDH1, and AaDBR2, four critical enzyme genes for the biosynthesis of artemisinin, had relatively high transcription levels in leaves of A. annua treated with IAA. In summary, this study indicated that exogenous IAA treatment was a feasible strategy to enhance artemisinin production, which paves the way for further metabolic engineering of artemisinin biosynthesis.

Evidence That PbrSAUR72 Contributes to Iron Deficiency Tolerance in Pears by Facilitating Iron Absorption.

Iron is an essential trace element for plants; however, low bioactive Fe in soil continuously places plants in an Fe-deficient environment, triggering oxidative damage. To cope with this, plants make a series of alterations to increase Fe acquisition; however, this regulatory network needs further investigation. In this study, we found notably decreased indoleacetic acid (IAA) content in chlorotic pear (Pyrus bretschneideri Rehd.) leaves caused by Fe deficiency. Furthermore, IAA treatment slightly induced regreening by increasing chlorophyll synthesis and Fe2+ accumulation. At that point, we identified PbrSAUR72 as a key negative effector output of auxin signaling and established its close relationship to Fe deficiency. Furthermore, the transient PbrSAUR72 overexpression could form regreening spots with increased IAA and Fe2+ content in chlorotic pear leaves, whereas its transient silencing does the opposite in normal pear leaves. In addition, cytoplasm-localized PbrSAUR72 exhibits root expression preferences and displays high homology to AtSAUR40/72. This promotes salt tolerance in plants, indicating a putative role for PbrSAUR72 in abiotic stress responses. Indeed, transgenic plants of Solanum lycopersicum and Arabidopsis thaliana overexpressing PbrSAUR72 displayed less sensitivity to Fe deficiency, accompanied by substantially elevated expression of Fe-induced genes, such as FER/FIT, HA, and bHLH39/100. These result in higher ferric chelate reductase and root pH acidification activities, thereby hastening Fe absorption in transgenic plants under an Fe-deficient condition. Moreover, the ectopic overexpression of PbrSAUR72 inhibited reactive oxygen species production in response to Fe deficiency. These findings contribute to a new understanding of PbrSAURs and its involvement in Fe deficiency, providing new insights for the further study of the regulatory mechanisms underlying the Fe deficiency response.

Indole-3-acetic Acid (IAA) Assisted Phyto-extraction Potential of Ipomoea aquatica Exposed to Lead (Pb) Stress

Agricultural lands are gradually being contaminated by heavy metals (HMs) obtained from urbanization and human activities. Lead (Pb) is one of the major heavy metals easily enters into food cycle and causes different health abnormalities. So elimination of this dangerous heavy metal from surface water is crucial and in this regard phyto-extraction based phytoremediation is an environmentally safe procedure. Again, this removal process can be amplified through the use of plant growth regulators exogenously. With this aim, an experiment was conducted to know the efficiency of the use of indole-3-acetic acid (IAA) on phyto-extraction of Pb by an aquatic hyper-accumulator plant Ipomoea aquatica. The plants were grown hydroponically with 200ppm Pb treated with 200ppm IAA exogenous spray or mixed with Hoagland solution (HS) or both. The control treatment was HS supplemented with Pb. From the experiment, it was observed that control treatment causes a great reduction in growth parameters as the plants suffered from Pb stress. Treatment with Control + IAA (spray+dissolve), produced tallest plants, longest roots and maximum dry weight. On the other hand, these parameters were got declined in case of Pb treated plants (control). Maximum Pb were accumulated on root, stem followed by leaf for Control + IAA (spray+dissolve). Control treatment caused less Pb accumulation on plant parts. So, maximum bioaccumulation factor (BCF) in root, shoot and leaf were 35.87, 15.33 and 9.15 respectively for Control + IAA (spray+dissolve) treatment. In case of root to shoot translocation, the maximum translocation factor (TF) value (0.5118) was found for Control + IAA (spray) than other treatments. Again for shoot to leaf, the maximum TF value (0.6051) was for HS + HM treatment (Control) and minimum TF value (0.4469) was observed for Control + IAA (spray). From the study, it is confirmed that, exogenous indole-3-acetic acid (IAA) successfully assist Pb phyto-extraction from aquatic bodies and Ipomoea aquatica is a potential heavy metal hyper-accumulating plant.

Changes in Java grass (Cymbopogon winterianus) physiology, essential oil production, and active constituents as influenced by catechol and some plant growth regulators applied through steaming technique.

A study was done to find out how steam-applied chemical and plant growth regulators affected plant growth and determine the most effective PGRs and chemical for maximizing java grass oil yield and quality attributes. A chemical viz. catechol and PGRs, viz. indole acetic acid (IAA), kinetin (Kn), 6-benzyl amino purine (BAP), salicylic acid (SA), and triacontanol (TRIA), ethrel, were applied to the plants at a concentration of 5 × 10−6 M at 90 days after transplantation (DAT) through an innovative technique of steaming using an electric steamer five times after a week interval. To prevent the plants from being harmed, we operated the steam jet at a certain distance from them. All the parameters were evaluated at 150 DAT. The results showed that among all these PGRs, IAA proved the best for growth, yield, and other parameters. In comparison to the control, the EO production more than doubled. Our study indicated that IAA enhanced the fresh and dry weight by 30.7% and 42.9%, total chlorophyll and carotenoids contents by 44.1% and 47.1%, nitrate reductase and carbonic anhydrase activity by 18.0% and 28.1%, respectively, over the control. Compared with control, IAA treatment increased the content and yield of essential oil by 96.8% and 155.7%, and the active constituents of EO, i.e., citronellol, citronellal, and geranial content, by 47.4%, 90.9%, and 43.9%, respectively. As a result, IAA used in this technique was very effective in increasing EO production while causing no harm to the plant.

Cytokinin-inducible response regulator SlRR6 controls plant height through gibberellin and auxin pathways in tomato.

Plant height is a key agronomic trait regulated by several phytohormones such as gibberellins (GAs) and auxin. However, little is known about how cytokinin (CK) participates in this process. Here, we report that SlRR6, a type-A response regulator in the CK signaling pathway, positively regulates plant height in tomato. SlRR6 was induced by exogenous kinetin and GA3, but inhibited by indole-3-acetic acid (IAA). Knock out of SlRR6 reduced tomato plant height through shortening internode length, while overexpression of SlRR6 caused taller plants due to increased internode number. Cytological observation of longitudinal stems showed that both knock out and overexpression of SlRR6 generated larger cells, but significantly reduced cell numbers in each internode. Further studies demonstrated that overexpression of SlRR6 enhanced GA accumulation and lowered IAA content, along with expression changes in GA- and IAA-related genes. Exogenous paclobutrazol and IAA treatments restored the increased plant height phenotype in SlRR6-overexpressing lines. Yeast two-hybrid, bimolecular fluorescence complementation, and co-immunoprecipitation assays showed that SlRR6 interacts with a small auxin up RNA protein, SlSAUR58. Moreover, SlSAUR58-overexpressing plants were dwarf with decreased internode length. Overall, our findings establish SlRR6 as a vital component in the CK signaling, GA, and IAA regulatory network that controls plant height.