Indole-3-acetic Acid Treatment Research Articles

Indole-3-acetic acid treatment promotes postharvest kiwifruit softening by regulating starch and cell wall metabolism

The softening process of postharvest kiwifruit is a critical aspect of fruit quality that has been extensively studied. However, the impact of indole-3-acetic acid (IAA) treatment on this process remains largely unexplored. In this study, we examined the effect of IAA treatment on the softening of postharvest kiwifruit. The results depicted that kiwifruit treated with IAA exhibited decreased firmness and increased ethylene production. Treatment with IAA upregulated the expression of starch decomposition genes, including AcSEX and AcBAM, resulting in a reduction in starch content. Additionally, IAA treatment induced cell wall breakdown, attributed to the enhanced transcript levels of cell wall-related degradation genes such as AcPE, AcPG, AcPL, and AcCX compared to the control. Consequently, IAA-treated kiwifruit displayed lower levels of cellulose and protopectin but higher levels of water-soluble pectin. In summary, our findings indicate that exogenous IAA promoted postharvest starch and cell wall biodegradation in kiwifruit, which reduced fruit firmness and accelerated fruit softening.

The transcription factor TaFDL2-1A functions in auxin metabolism mediated by abscisic acid to regulate shoot growth in wheat.

Genetic strategies can be effective in improving wheat (Triticum aestivum L.) drought stress tolerance, but accumulating evidence suggests that overexpressing drought-resistance genes, especially genes related to the abscisic acid (ABA) signaling pathway, can retard plant growth. We previously characterized the positive roles of the wheat bZIP transcription factor TaFD-Like2-1A (TaFDL2-1A) in drought stress tolerance and ABA biosynthesis and response, whereas a dwarfing shoot exhibited under normal conditions. This study determined the underlying mechanisms that allow TaFDL2-1A to affect shoot growth. Overexpressing TaFDL2-1A decreased cell length, cell width, leaf size, shoot length, and biomass in wheat. The results of RNA-seq showed that multiple differently expressed transcripts are enriched in the auxin signaling pathway. Further analysis indicated higher expression levels of Gretchen Hagen3 (GH3) genes and lower indole-3-acetic acid (IAA) concentrations in the TaFDL2-1A overexpression lines. Exogenous IAA treatment restored the phenotypes of the TaFDL2-1A overexpression lines to wild-type levels. Transcriptional regulation analysis suggested that TaFDL2-1A enhances the expression of auxin metabolism genes, such as TaGH3.2-3A, TaGH3.2-3B, TaGH3.8-2A, and TaGH3.8-2D, by directly binding to ACGT core cis-elements. Furthermore, tafdl2 knock-out plants had lower expression levels of these GH3 genes and higher IAA levels than Fielder wheat. These GH3 gene expression and IAA levels were induced and reduced in Fielder wheat and tafdl2 knock-out plants treated with exogenous ABA. Our findings elucidate mechanisms underlying the functional redundancy of TaFDL2-1A in the crosstalk between ABA and IAA to affect shoot growth and provide insights into the balance between drought resistance and yield in wheat.

The MYB transcriptional factor BrMYB108 regulates Auxin-mediated delayed leaf senescence in postharvest Pak Choi

Auxin is the earliest discovered class of endogenous plant hormones, widely distributed in higher plants, and plays a key role in regulating plant growth and development. However, the molecular mechanism by which auxin affects postharvest leaf senescence in pak choi (Brassica rapa subsp. chinensis) remains unclear. In this study, we found that exogenous application of 2 mg L−1 of the auxin analog indoleacetic acid (IAA) could delay postharvest leaf senescence in pak choi. Importantly, we isolated an R2R3-MYB transcription factor (TF), BrMYB108, which was highly expressed in senescent leaves and whoes expression was suppressed by IAA treatment. Molecular evidence confirmed that BrMYB108 can bind to the promoter region of the chlorophyll metabolism gene BrSGR2 to activate its expression. Heterologous expression of BrMYB108 in Arabidopsis accelerated leaf senescence, while silencing BrMYB108 in pak choi using virus induced gene silencing (VIGS) delayed leaf senescence. In addition, we found that BrMYB108 is a direct target gene of the auxin response factor 17 (ARF17) homolog gene, BrARF17, in Arabidopsis. Our study reveals a model in which BrARF17 regulates postharvest leaf senescence in pak choi by targeting the expression of BrMYB108. These molecular insights into the auxin-mediated regulation of postharvest leaf senescence in pak choi have positive implications for manipulating BrMYB108 to improve the postharvest shelf life of vegetables.

Metabolomic Analyses Reveal That IAA from Serratia marcescens Lkbn100 Promotes Plant Defense during Infection of Fusarium graminearum in Sorghum.

Global sorghum production has been significantly reduced due to the occurrence of sorghum root rot caused by the fungus Fusarium graminearum. The utilization of biocontrol microorganisms has emerged as an effective strategy. However, the underlying mechanisms remain unclear. Therefore, the aim of this study was to investigate the effectiveness of biocontrol bacteria in inducing sorghum resistance against sorghum root rot and explore the potential induced resistance mechanisms through metabolomics analysis. The results revealed that the biocontrol bacteria Lnkb100, identified as Serratia marcescens (GenBank: PP152264), significantly enhanced the resistance of sorghum against sorghum root rot and promoted its growth, leading to increased seed weight. Targeted metabolomics analysis demonstrated that the highest concentration of the hormone IAA (indole-3-acetic acid) was detected in the metabolites of Lnkb100. Treatment with IAA enhanced the activity of disease-related enzymes such as SOD, CAT, POD and PPO in sorghum, thereby improving its resistance against sorghum root rot. Further untargeted metabolomic analysis revealed that IAA treatment resulted in higher concentrations of metabolites involved in the resistance against F. graminearum, such as geniposidic acid, 5-L-Glutamyl-taurine, formononetin 7-O-glucoside-6″-O-malonate, as well as higher concentrations of the defense-related molecules volicitin and JA. Additionally, "secondary bile acid biosynthesis" and "glycerophospholipid metabolism" pathways were found to play significant roles in the defense response of sorghum against fungal infection. These findings provide a reliable theoretical basis for utilizing biocontrol microorganisms to control sorghum root rot.

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.

Morphological and Physiological Characteristics of Stevia rebaudiana Bertoni Stem Cuttings Under 3-Indoleacetic Acid (IAA) Treatment

Abstract Stevia rebaudiana is a high-value crop because of its metabolites, such as steviol glycosides. However, it only produces a few seeds, resulting in low productivity. Therefore, an appropriate propagation method is required to enhance its productivity. This study aimed to assess stevia’s morphological and physiological characteristics upon treatment with three doses of Indole-3-acetic acid (IAA) [mg/L] through stem-cutting propagation. The cuttings were treated with IAA at 0, 20, 40 and 60 mg/L by dipping them in the IAA solution for 1 minute, then planting in growth media (garden soil, organic compost and coco peat with a ratio of 2:1:1) and keeping them in the greenhouse. The survival percentage, root length and number, plant height, leaf number, total chlorophylls, and stomata length and number were assessed in the 3rd week. The application of 40 mg/L IAA resulted in a significant improvement in all parameters. However, IAA treatment also causes stomata abnormalities. This result suggested that stem cutting and IAA treatment significantly contribute to stevia propagation.

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.