Indole-3-acetic Acid Content Research Articles

Effects of earthworm (Eisenia fetida) and arbuscular mycorrhizal fungi improving plant hormones and antioxidant enzymes under simulated acid rain stress

Acid rain is considered one of the three most serious environmental disasters worldwide, disrupting the normal physiological metabolism of plants and inhibiting their growth. Earthworms alleviate plant stress by regulating soil physical, chemical and biological characteristics, and mycorrhizal fungi can promote plant nutrient absorption and improve plant resistance via symbiosis with plants. We used Illumina high-throughput sequencing to conduct a relevant redundancy analysis (RDA) of soil microbial community structure and plant growth factors, and we constructed a structural equation model (SEM) for maize biomass and a biological index to study the mechanisms by which earthworms and mycorrhizal fungi affect maize stress resistance under simulated acid rain stress. The results showed that earthworms promoted the decomposition of soil organic matter; promoted the growth of the root system; and increased the hormone levels of gibberellin A3 (GA3), abscisic acid (ABA) and indole-3-acetic acid (IAA), ultimately improving the stress resistance of maize. Mycorrhizal fungi increased the relative abundance of plant growth-promoting rhizosphere bacteria, increased the levels of plant hormones and antioxidant enzymes, and improved the stress resistance of maize. Earthworms promoted infection by mycorrhizal fungi, and the interaction between earthworms and mycorrhizal fungi increased the root IAA content and the Shannon index of rhizosphere bacteria and alleviated the simulated acid rain stress of the aboveground part of the maize. This funding is crucial to understanding above- and belowground feedback in plant–soil systems under abiotic stress.

Liquid chromatography–tandem mass spectrometry method for the bioanalysis of N,N-dimethyltryptamine (DMT) and its metabolites DMT-N-oxide and indole-3-acetic acid in human plasma

The indole alkaloid N,N-dimethyltryptamine (DMT) induces psychedelic effects in humans. In addition to ceremonial and recreational use, DMT is subject to clinical investigations. Sensitive bioanalytical methods are required to assess the pharmacokinetics of DMT and its metabolites in human plasma. Here, a high performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the quantification of DMT and its major metabolites indole-3-acetic acid (IAA) and DMT-N-oxide (DMT-NO) was developed and validated. As IAA is an endogenous component of human plasma, 13C6-IAA was used to determine IAA concentrations. After simple protein precipitation with methanol, analytes were separated on a pentafluorophenyl column. A gradient consisting of 0.1% (v/v) formic acid in a methanol–water mixture was applied for analyte separation. The analytes were detected by positive electrospray ionization followed by multiple reaction monitoring. The calibration range of the assay was 0.25–250 ng/mL for DMT, 0.1–100 ng/mL for DMT-NO, and 25–25,000 ng/mL for 13C6-IAA. The intra- and inter-assay accuracy was 93–113% for all analytes at all quality control levels, with coefficient of variation ≤ 11%. All analytes were stable under storage conditions relevant for the analysis of large batches of study samples. The validated method was capable of assessing pharmacokinetic (PK) parameters of DMT and its metabolites in study participants intravenously perfused with 1 mg/min DMT for 90 min. Overall, the developed method is easy-to-use, has a short run time, and qualifies for PK and metabolism studies of DMT in clinical settings.

Ameliorative Effects of Indole Acetic Acid and Naphthalene Acetic Acid on Some Biochemical Parameters of Soybean Exposed to Lead Toxicity

Lead (Pb) is a potential pollutant that readily accumulates in soils. IAA and NAA belongs to plant hormone auxin that promote plants growth. This work aim at examining possible ameliorative effects of Indole acetic acid (IAA) and Naphthalene acetic acid (NAA) on some biochemical parameters of soybean exposed to Pb toxicity. Seeds of soybean (TGX 1835-10E) genotype were sown in 5kg bags of soil containing 1000mg/L of Lead nitrate (PbNO3). 40mg/L, 80 mg/L and 120mg/L each of IAA and NAA were prepared and applied by foliar method after 5 weeks of planting. Photosynthetic pigments, mineral elements and antioxidant enzymes were determined on the root, stem and leaf after 7 weeks of planting. Data were analysed using anova at 5% level of significance. The results showed that the level of chlorophyll a, b and carotenoid, mineral elements and antioxidant enzymes significantly increased in the root, stem and leaf of soybean treated with different concentration of Indole acetic acid (IAA) and Naphthalene acetic acid (NAA) as compared with the control (C+ve). All bioregulators (IAA and NAA) concentrations significantly decreased in the level of Pb2+ (except 40mg/L IAA in the root and leaf while all concentration have significant effects in the stem) and also all concentration of (IAA and NAA) significantly increased in the level of biochemical parameters to different extent as compared to control(C+ve). These results show that Indole acetic acid (IAA) and Naphthalene acetic acid (NAA) could ameliorate the Pb toxicity and therefore will be of relevance to agricultural producers.

The effect of auxin status driven by bacterivorous nematodes on root growth of Arabidopsis thaliana

Bacterivorous nematodes are one of the dominant microbial organisms and play an important role in shaping the bacterial community and hormone dynamics in rhizosphere soils. It has been found that the presence of bacterivorous nematodes potentially regulate indole-3-acetic acid (IAA) content in soils by interacting with the status of IAA-producing bacteria, and eventually act on the growth of plant roots. However, the mechanism behind this interaction in broad soil ecosystems remains unknown. This study reveals the interaction between bacterivorous nematodes and the soil bacterial community, especially IAA-producing bacteria, based on denaturing gradient gel electrophoresis (DGGE) analysis. The results of DGGE showed that the bacterial diversity in soil was increased by inoculation of nematodes during certain periods of plant culture, and was also affected by the genotype of the Arabidopsis thaliana (Johannes Thal, 1577) plants. The variation in soil bacterial communities among the treatments with different genotypes of A. thaliana and nematodes indicated that the soil bacterial community structure was affected by both genotype and nematode grazing. Furthermore, we measured the root architectures of four genotypes of A. thaliana, including wild type (Col-0), two IAA-insensitive mutants (Axr5 and Axr3–1), and DR5::GUS transgenic type (IAA sensitive) under different conditions of bacterivorous nematode inoculation. We found that the root architecture of the IAA-sensitive A. thaliana developed more tips and slender roots under inoculation with activated bacterivorous nematodes, while the root architectures of auxin-insensitive A. thaliana mutants showed no significant differences between alive and inactivated bacterivorous nematodes, even though the IAA content increased in the soil under inoculation with alive nematodes. This study confirms that the presence of bacterivorous nematodes in soils increases the soil IAA content significantly by regulating the bacterial community structure, which leads to an accumulation of auxin in the root tips of A. thaliana, and eventually enhances the plant root growth.

Exogenous Sucrose Supply Regulates the Physiological Index Levels Before the Flower Blooming and Fruit Abscission Stages in the Biodiesel Tree Sapindus mukorossi Gaertn.

Nutrient deficiency leads to a high fruit abscission rate and low yields of Sapindus mukorossi Gaertn. (Soapberry), which is one of the most widely cultivated biodiesel feedstock forests in China. Exogenous sucrose can provide a solution to nutrient deficiency and fruit abscission leading to low yields; therefore, it was applied to whole trees at two stages, 20 days before blooming (DBB stage) and before fruit abscission [days before fruit abscission (DBFA) stage]. Six sucrose concentrations, 0%, 1%, 1.5%, 3%, 5%, and 7%, were sprayed three times using a completely randomized block design with five replications and six treatments. 13CO2 labeling experiments were performed after the three sprayings. The results indicated that the 3% treatment had the highest yield, reaching 15.9 kg/tree. During the DBB stage, the 3% treatment significantly increased the inflorescence fructose and glucose contents 1- to 1.2-times and resulted in the highest fruit gibberellic acid, leaf indole acetic acid (IAA), fruit IAA, and fruit zeatin contents; however, it decreased the inflorescence abscisic acid (ABA) from 16 μg/g to 4 μg/g. The 1.5% and 3% treatments significantly increased the carbohydrate content and decreased the fruit ABA content to 30% to 50% of the control level during the DBFA stage. High-concentration sugar treatment (>3%) increased the nitrogen, phosphorus, and potassium contents, which decreased the calcium and magnesium contents. The 13C-dispatching ability of the inflorescence was three-times greater than that of leaves under the high-concentration sugar treatment during the DBB stage. Supplying 1.5% sucrose nearly doubled the allocation capacity during the DBFA stage. The source-sink nutrient migration pathway showed that leaf and fruit sugars were directly correlated with phosphorus. Fruit fructose and glucose contents affected the leaf mineral element contents.

Enhancement of antibacterial and growth-promoting effects of Paenibacillus polymyxa by optimizing its fermentation process.

We aimed to enhance the antibacterial and growth-promoting effects of Paenibacillus polymyxa by improving the yield of spores, lipopeptides and indole-3-acetic acid (IAA) in the fermentation process. Through medium optimization by the response surface method and feeding fermentation, the number of spores reached 2.37 × 109 cfuml-1 with an increase of 38%, the content of lipopeptides reached 60.8mg L-1 with an increase of 89%, and the content of IAA reached 24.3mg L-1 with an increase of 176%, respectively, comparing with the original (un-optimized) culture conditions. The fermentation culture of P. polymyxa from the optimized medium and feeding fermentation resulted in higher colonization of P. polymyxa in soils than that from the original culture during the 49 days for testing. Comparing with the supernatant of the original culture, the supernatant of the P. polymyxa culture from the optimized medium and feeding fermentation showed enhanced antibacterial effects and plant growth-promoting effects. The enhanced antibacterial effect was shown as the increase of the inhibition zone by 59%, 45% and 26% against Ralstonia solanacearum, Erwinia carotovora and Xanthomonas campestris. The enhanced growth-promoting effects on tomato and strawberry plants were the increase of plant height by 47% and 5%, root length by 23% and 15% and root weight by 65% and 110%. The combination of medium optimization and feeding fermentation effectively improved the yield of spores, lipopeptides and IAA. Lipopeptides and IAA lead to enhanced antibacterial and plant growth-promoting effects of the P. polymyxa product. The optimized fermentation method significantly improved the yield of spores, lipopeptides and IAA, thus providing theoretical and technical support for enhancing the antibacterial and growth-promoting effects of P. polymyxa products in agriculture.

First experimental evidence suggests use of glucobrassicin as source of auxin in drought-stressed Arabidopsis thaliana.

The synthesis of indole-3-acetonitrile (IAN) from the indolic glucosinolate (iGSL) glucobrassicin (GB) is a unique trait of members of the Brassicales. To assess the contribution of this pathway to indole-3-acetic acid (IAA) synthesis under stress conditions, drought stress (DS) experiments with Arabidopsis thaliana were performed in vitro. Analysis of GSLs in DS plants revealed higher contents of GB in shoots and roots compared to control plants. Deuterium incorporation experiments showed the highest turnover of GB compared to all other GSLs during drought conditions. Evidence suggests the involvement of the thioglucosidase BGLU18 in the degradation of GB. The nitrile specifier proteins NSP1 and NSP5 are known to direct the GSL hydrolysis towards formation of IAN. Nitrilases like NIT2 are able to subsequently synthesize IAA from IAN. Expression of BGLU18, NSP1, NSP5 and NIT2 and contents of GB, IAN and IAA were significantly elevated in DS plants compared to control plants suggesting the increased use of GB as IAA source. Significantly higher contents of reactive oxygen species in DS bglu18 and epithionitrile specifier protein (esp) mutants compared to Col-0 indicate higher stress levels in these mutants highlighting the need for both proteins in DS plants. Furthermore, GB accumulation in leaves was higher in both mutants during DS when compared to Col-0 indicating enhanced synthesis of GB due to a lack of breakdown products. This work provides the first evidence for the breakdown of iGSLs to IAN which seems to be used for synthesis of IAA in DS A. thaliana plants.

Effects of Different Hormonal Concentrations on In vitro Regeneration and Multiplication of Pearl Millet (Pennisetum glaucum L.)

An efficient in-vitro regeneration and multiplication protocol was developed to check the effects of different hormonal concentrations through somatic embryogenesis of Pearl millet (Pennisetum glaucum L.). The explants (seeds) of P. glaucum were surface sterilized with different concentrations (30, 50 and 70%) of Sodium hypochlorite to ensure the removal of surface contamination. For the regeneration the explants were inoculated on MS media supplemented with varying concentrations of indole acetic acid (IAA 2 mg/L, 0.75 mg/L, 0.1 mg/L, 0.2 mg/L and 0.3 mg/L) and kinetin (KIN 1.5 mg/L, 0.5 mg/L, 0.5 mg/L, 1 mg/L and 1.5mg/L) respectively. The maximum germination (87.5 %) of explants was obtained by using 70 % Chlorox and minimum germination (62.5 %) of explants was obtained by using 30% Chlorox. The maximum stem length (15.5 cm), roots number (12), roots length (3.96 cm) and leaves length (6.76 cm) was observed on MS medium containing (IAA 2 mg/L and KIN 1.5 mg/L). The maximum leaves number (7) was observed on MS medium containing (IAA 0.75 mg/L and KIN 0.5 mg/L). The minimum stem length (3 cm), roots number (1), roots length (1 cm), leaves number (1) and leaves length (3 cm) was observed on MS medium supplemented with (IAA 0.2 mg/L and KIN 1 mg/L). The maximum Stem length (15.5cm), Roots number (12), Roots length (3.96 cm) and Leaves length (6.76 cm) was observed on MS medium supplemented with (IAA 2 mg/L and KIN 1.5 mg/L) although maximum leaves number was observed on MS medium supplemented with (IAA 0.75 mg/L and KIN 0.5 mg/L). The study revealed an easy and reproducible in-vitro regeneration protocol of pearl millet that can provide an efficient plant regeneration which can be further exploited for transgenic applications

Molecular mechanisms of plant growth promotion for methylotrophic Bacillus aryabhattai LAD

Plant growth-promoting rhizobacteria (PGPR) can produce hormone-like substances, promote plant nutrient uptake, enhance plant resistance, inhibit the growth of pathogenic bacteria, and induce plant resistance to biotic and abiotic stresses. Bacillus is one of the most studied genera that promote plant root development. Since its discovery in 2009, B. aryabhattai has shown promising properties such as promoting plant growth and improving crop yield. However, the mechanisms of B. aryabhattai promoting plant growth remain to be investigated. In this study, the chromosome of B. aryabhattai strain LAD and five plasmids within the cell were sequenced and annotated. The genome, with a length of 5,194,589 bp and 38.12% GC content, contains 5,288 putative protein-coding genes, 39 rRNA, and 112 tRNA. The length of the five plasmids ranged from 116,519 to 212,484 bp, and a total of 810 putative protein-coding genes, 4 rRNA, and 32 tRNA were predicted in the plasmids. Functional annotation of the predicted genes revealed numerous genes associated with indole-3 acetic acid (IAA) and exopolysaccharides (EPSs) biosynthesis, membrane transport, nitrogen cycle metabolism, signal transduction, cell mobility, stress response, and antibiotic resistance on the genome which benefits the plants. Genes of carbohydrate-active enzymes were detected in both the genome and plasmids suggesting that LAD has the capacity of synthesizing saccharides and utilizing organic materials like root exudates. LAD can utilize different carbon sources of varied carbon chain length, i.e., methanol, acetate, glycerol, glucose, sucrose, and starch for growth and temperature adaptation suggesting a high versatility of LAD for thriving in fluctuating environments. LAD produced the most EPSs with sucrose as sole carbon source, and high concentration of IAA was produced when the maize plant was cultivated with LAD, which may enhance plant growth. LAD significantly stimulated the development of the maize root. The genome-based information and experimental evidence demonstrated that LAD with diverse metabolic capabilities and positive interactions with plants has tremendous potential for adaptation to the dynamic soil environments and promoting plant growth.

Wireless electrochemical sensor for the detection of phytoregulator indole-3-acetic acid using gold nanoparticles and three-dimensional reduced graphene oxide modified screen printed carbon electrode

Plant hormones are important regulatory substances in crop growth and production. In this work, a wireless electrochemical sensor has been successfully established by using gold nanoparticles and three-dimensional reduced graphene oxide (AuNPs-3DGR) modified screen printed carbon electrode (SPCE) to detect plant regulator indole-3-acetic acid (IAA) in plants. AuNPs-3DGR nanocomposite was prepared by reduction of ultrasonic assisted liquid phase dispersed graphene oxide (GO) and Au3+ mixture using hydrothermal method. The composite was modified on SPCE by drop coating, and the wireless portable electrochemical workstation that controlled by smartphone was used to detect IAA with a wider linear ranges (0.25–120.0 μmol/L and 135.0–500.0 μmol/L) and a lower limit of detection (0.15 μmol/L, 3σ/S). After that, this sensor was applied to detect the IAA content in different tissues of mung bean sprouts with satisfactory results. The combination of modified SPCE with small bluetooth workstations and smartphone is very useful to construct portable, low-cost, simple and fast electrochemical sensing platform.

Exogenous IAA improves the seedling growth of Syringa villosa via regulating the endogenous hormones and enhancing the photosynthesis

Auxin is a core regulator of plant growth and an effective promoter of cell division and cell expansion. Effects of auxin on improving plant growth of Syringa plants remain poorly elucidated. The present study was carried out to investigate the effects of exogenous indole-3-acetic acid (IAA) on morphogenesis, endogenous hormone content, photosynthesis capacity and find the basis of IAA-induced physiological effects of Syringa villosa by transcriptome sequencing technology. The results indicated that exogenous IAA significantly contributed to the plant height, stem diameter, leaf area and leaf number, which improved the accumulation of whole plant quality. Contents of endogenous IAA and gibberellic acid (GA3) were markedly higher than control after IAA treatment, while abscisic acid (ABA) content was significantly declined. For photosynthetic parameters, photosynthesis capacity was promoted by the application of IAA, as evidenced by a significant increase in net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) and a lower intercellular CO2 concentration (Ci). In addition, the transcriptome of S. villosa was first sequenced which revealed that genes related to the synthesis and signal transduction of growth-promoting hormones such as IAA, GA3, cytokinin (CTK), and brassinolide (BR) were significantly up-regulated within 2 h of IAA treatment. The expression levels of genes related to photosynthesis, antenna proteins, and carbon fixation of photosynthetic organisms were also enhanced by exogenous IAA. Additionally, the application of exogenous IAA had a positive effect on growth and development by rapidly inducing genes related to cell division and cell expansion. By profiling the transcriptome of IAA response, potential target genes were identified based on the hormone levels and photosynthesis. These results provide insights for further functional genomic studies on the regulatory mechanisms of IAA underlying Syringa plants architecture.

Bacillus thuringiensis CHGP12 uses a multifaceted approach for the suppression of Fusarium oxysporum f. sp. ciceris and to enhance the biomass of chickpea plants.

Bacillus species synthesize antifungal lipopeptides (LPs) making them a sustainable and eco-friendly management option to combat Fusarium wilt of chickpea. In this study, 18 endophytic Bacillus strains were assessed for their antifungal activity against Fusarium oxysporum f. sp. ciceris (FOC) associated with Fusarium wilt of chickpea. Among them, 13 strains produced significant inhibition zones in a direct antifungal assay while five strains failed to produce the inhibition of FOC. Bacillus thuringiensis CHGP12 exhibited the highest inhibition 3.45 cm of FOC. The LPs extracted from CHGP12 showed significant inhibition of the pathogen. Liquid chromatography-mass spectrometry (LC-MS) analysis confirmed that CHGP12 possessed the ability to produce fengycin, surfactin, iturin, bacillaene, bacillibactin, plantazolicin, and bacilysin. In an in vitro qualitative assay CHGP12 exhibited the ability to produce lipase, amylase, cellulase, protease, siderophores, and indole 3-acetic acid (IAA). IAA and gibberellic acid (GA) were quantified using ultra-performance liquid chromatography (UPLC) with 370 and 770 ng mL-1 concentrations of IAA and GA respectively. Furthermore, the disease severity showed a 40% decrease over control in CHGP12 treated plants compared to the control in a glasshouse experiment. Moreover, CHGP12 also exhibited a significant increase in total biomass of the plants namely, root and shoot growth parameters, stomatal conductance, and photosynthesis rate. In conclusion, our findings suggest that B. thuringiensis CHGP12 is a promising strain with high antagonistic and growth-promoting potential against Fusarium wilt of chickpea. © 2022 Society of Chemical Industry.

A high trans-zeatin nucleoside concentration in corms may promote the multileaf growth of Amorphophallus muelleri.

Amorphophallus muelleri has a multileaf growth pattern different from that of other konjacs; however, the hormonal mechanism underlying this phenomenon is not clear. In this study, the levels of hormones closely related to the sprouting of the axillary bud, including five types of cytokinins, indole-3-acetic acid (IAA) and abscisic acid (ABA) were measured. In the second leaf sprouting stage, the content of trans-zeatin riboside (tZR) in corms increased more than 5000-fold over that in the dormancy period. Surprisingly, although the expression of CYP735A1 and CYP735A2, which synthesize the precursors for tZR was elevated at the second leaf sprouting stage, the expression of IPTs, which have key roles in cytokinin biosynthesis, did not change significantly. In addition, most cytokinin contents in leaves during the same period were significantly lower than those in corms. We speculate that the high cytokinin contents in the corms may not biosynthesized de novo in corms. In addition, the IAA content in the corms also considerably increased during the second leaf sprouting stage. Indole-3-acetaldehyde oxidase (AO1) and auxin efflux carrier PIN1A, presented relatively high expression levels in the same period. In contrast, ABA content, and the expression of NCED1, a rate-limiting enzyme in ABA biosynthesis, were suppressed at the second leaf sprouting stage. It is worth mentioning that N6-(Δ2-isopentenyl) adenosine (iP)-type cytokinins have a high content in corms in the dormant period that significantly decreases after the first leaf sprouting stage, which is completely different from the trend of tZR. By treating dormant corms with iP, the percentage of multibud plants increased, and the growth performance in terms of bud and root length was significantly higher than those of the control. This implies that iP-type cytokinins tend to play a role in promoting first seedling sprouting. Furthermore, there was a remarkable increase of the IAA content in both corms and roots under iP treatment but an inhibitory effect in buds. We speculate that the increase in the IAA content induced by iP is tissue specific. These results will assist in the understanding of the role of hormones, especially cytokinins, in the multileaf growth type of konjac.

Bacillus amyloliquefaciens GB03 augmented tall fescue growth by regulating phytohormone and nutrient homeostasis under nitrogen deficiency.

Nitrogen is an important nutrient for plant growth and development. Soil microorganisms have been used to curb the imbalance between the limited content of natural environmental nitrogen and the pollution caused by increasing nitrogen fertilizer use in ecologically fragile areas. Bacillus amyloliquefaciens GB03 has been shown to confer growth promotion and abiotic stress tolerance in Arabidopsis thaliana. This study provided a new insight into the role of the plant growth-promoting rhizobacterium B. amyloliquefaciens GB03 as an initiator of defense against nitrogen deficiency in non-leguminous grass tall fescue (Festuca arundinacea). Two-week-old seedlings of tall fescue were grown with or without GB03 for 4 weeks under total nitrogen (3.75 mM NO3 -) or low nitrogen (0.25 mM NO3 -) treatment. Growth parameters, chlorophyll content, endogenous total nitrogen, total phosphorus content, and phytohormone content, including those of auxin indole-3-acetic acid, cytokinin, gibberellic acid, and abscisic acid, were determined at the time of harvest. Tall fescue grown in GB03-inoculated soil was more robust than the non-inoculated controls with respect to plant height, root length, plant biomass, chlorophyll concentration, and nutrient (total nitrogen and total phosphorus) contents under total nitrogen treatment. GB03 increased indole acetic acid content by 24.7%, whereas decreased cytokinin and abscisic acid contents by 28.4% and 26.9%, respectively, under a total nitrogen level. Remarkably, GB03 increased indole acetic acid content by more than 80% and inhibited abscisic acid production by nearly 70% under a low nitrogen level. These results showed, for the first time, that GB03 played a crucial role in mediating NO3 –dependent regulation of tall fescue growth and development, especially revealing the mechanism of soil bacteria improve resistance to nitrogen deficiency stress in non-nitrogen-fixing species.

Isolation and Functional Characterization of Culture-Dependent Endophytes Associated with Vicia villosa Roth

In a natural ecosystem, endophytic fungi in the internal tissues of plants help to improve the growth of the host plants and to decrease the negative effects of biotic and abiotic stresses without having adverse effects. In Japan, Vicia villosa (hairy vetch), a legume plant with a high capacity to fix nitrogen, is usually used as a cover crop before soybeans to enhance the fertility and structure of the soil. This study aimed to isolate endophytic fungi associated with different tissues of hairy vetch and to evaluate their potential for growth-promoting and biocontrol effects in plants. Thirty-three fungal endophytes belonging to Ascomycota and Basidiomycota were isolated from the leaf, stem, and root tissues of hairy vetch grown under both greenhouse and field conditions. The highest colonization frequency in both the greenhouse and field-grown hairy vetch plants was obtained from the root tissues. All isolates were checked for indole-3-acetic acid (IAA) and siderophore production. The maximum IAA content in the culture filtrate (4.21 μg mL−1) was produced by the isolate hvef7 (Cladosporium cladosporioides), followed by hvef18 (Penicillium simplicissimum) (3.02 μg mL−1) and hvef1 (Cladosporium pseudocladosporioides) (2.32 μg mL−1). Nineteen isolates among a total of thirty-three isolates produced siderophores. Moreover, some of the isolated strains could solubilize phosphate and potassium. Most of the isolates showed antagonistic potential against Calonectria ilicicola. The results of this study show that endophytic fungi isolated from hairy vetch have the potential for application as plant growth promotion fungi (PGPF) to promote plant growth and control disease in sustainable agriculture.

In vitro effect of phytosynthesised AgNPs to enhance plantlets and biomass production in Nyctanthes arbor-tristis L.

This work was aimed to establish an effective approach for direct regeneration of Nyctanthes arbor-tristis L. using nodal segment. Amongst the different combinations of plant growth regulators (PGR's), the maximum number of shoots/explant (32.94 ± 0.86) with 3.14 ± 0.08 cm shoot length was attained on Murashige and Skoog (MS) medium fortified with 3.5 mg /L 6-benzyladenine (BA) and 0.3 mg/L concentration of 1-phenyl-3-(1, 2, 3- thiadiazol-5-yl)- urea (TDZ). Besides, nodal segments of Nyctanthes grown on MS medium were used to analyze the effect of biogenic AgNPs (0,2,4,6,8 and 10 mg/L) on plant growth & multiplication in solid & suspension culture medium. After 35 days of in vitro shoot proliferation, the shoot number, shoot length, chlorophyll content, fresh & dry matter, guaiacol peroxidase (GPOX) and catalases enzyme (CAT) activities of plants were quantified. The administration of AgNPs (6 mg/L) along with the lower concentration of BA (1 mg/L) could enhance shoot multiplication from (1.29 ± 0.14) to (25.17 ± 0.45), chlorophyll content as well as the GPOX, and CAT enzyme activities in suspension culture medium. Optimized rooting response (12.15 ± 0.63) was noted on the half-strength MS medium supplemented with 0.5 mg/L concentration of Indole acetic acid (IAA), The maximum in vitro raised plantlets was hardened & acclimatized in a ratio of 6:2:2:1(garden soil: cocopeat: vermiculite: pearlite) potting mixture. The regenerated plantlets showed 80% survival rate under greenhouse conditions. Out of twenty PCR-based RAPD (Random Amplified Polymorphic DNA) molecular markers, 8 primers produced a total of 350 scorable bands which showed 90–99% similarity with mother plant.

OsARF4 regulates leaf inclination via auxin and brassinosteroid pathways in rice.

Leaf inclination is a vital agronomic trait and is important for plant architecture that affects photosynthetic efficiency and grain yield. To understand the molecular mechanisms underlying regulation of leaf inclination, we constructed an auxin response factor (arf) rice mutant—osarf4—showing increased leaf inclination using CRISPR/Cas9 gene editing technology. OsARF4 encodes a nuclear protein that is expressed in the lamina joint (LJ) at different developmental stages in rice. Histological analysis indicated that an increase in cell differentiation on the adaxial side resulted in increased leaf inclination in the osarf4 mutants; however, OsARF4-overexpressing lines showed a decrease in leaf inclination, resulting in erect leaves. Additionally, a decrease in the content and distribution of indole-3-acetic acid (IAA) in osarf4 mutant led to a greater leaf inclination, whereas the OsARF4-overexpressing lines showed the opposite phenotype with increased IAA content. RNA-sequencing analysis revealed that the expression of genes related to brassinosteroid (BR) biosynthesis and response was different in the mutants and overexpressing lines, suggesting that OsARF4 participates in the BR signaling pathway. Moreover, BR sensitivity assay revealed that OsARF4-overexpressing lines were more sensitive to exogenous BR treatment than the mutants. In conclusion, OsARF4, a transcription factor in auxin signaling, participates in leaf inclination regulation and links auxin and BR signaling pathways. Our results provide a novel insight into l leaf inclination regulation, and have significant implications for improving rice architecture and grain yield.

Effect of Plant Growth Regulators on Osmotic Regulatory Substances and Antioxidant Enzyme Activity of Nitraria tangutorum.

Plant growth regulators (PGRs) are natural hormones and synthetic hormone analogues. At low concentrations, PGRs have the ability to influence cell division, cell expansion, and cell structure and function, in addition to mediating environmental stress. In this study, experiments were conducted to determine how exogenous PGRs indole acetic acid (IAA), abscisic acid (ABA), and gibberellic acid (GA) influenced osmotic regulatory substances and activity of antioxidant enzymes in Nitraria tangutorum. Using a completely randomized design, IAA, ABA, and GA3 were applied as foliar spray at concentrations of 50 mg/L, 100 mg/L, 150 mg/L, and 200 mg/L to N. tangutorum shrubs. Some selected shrubs did not receive any treatment and served as the control (Ck). The results showed that the foliar spray of IAA, ABA, and GA3 significantly increased the content of osmotic regulatory substances (soluble sugar, soluble protein, and proline) and antioxidant enzymes (SOD and POD) at most concentrations. In addition, the malondialdehyde (MDA) content significantly reduced after treatment, but after regrowth of coppiced shrubs, lipid peroxidation increased and was still lower than Ck. Our study provides evidence that 100 mg/L 150 mg/L, and 200 mg/L concentrations of IAA, ABA, and GA3 treatments are effective for enhancing osmotic regulatory substances and the activity of antioxidant enzymes in N. tangutorum, which offers an effective strategy not only for increasing tolerance to abiotic and biotic stresses, but also improving the adaptability of N. tangutorum shrubs to the environment.

Widely targeted metabolomics analysis reveals the effect of exogenous auxin on postharvest resistance to Botrytis cinerea in kiwifruit (Actinidia chinensis L.)

Kiwifruit has high economic value but is susceptible to fungal infection after harvest. Botrytis cinerea (B. cinerea) is one of these fungal pathogens that cause huge economic losses and potential food safety problems. Auxin is a vital plant growth regulator that has been reported to play a role in plant defense. In this study, postharvest kiwifruit was treated with different concentrations of indole-3-acetic acid (IAA), after which the average incidence rate and lesion area were analyzed to determine the appropriate concentration of IAA for disease resistance. Defense enzymes, such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were detected. Ultra-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS)-based widely targeted metabolomic analysis was used to investigate the mechanism of kiwifruit active compounds during IAA treatment and B. cinerea infection. Exogenous IAA treatment (especially at 50 μg/ mL) enhanced the resistance of kiwifruit to B. cinerea, resulting in reduced disease incidence and lesion area, and showed higher pathogen resistance-related defense enzyme activity in response to B. cinerea infection. Further metabolomic analysis revealed 776 metabolites in kiwifruit after IAA treatment, among which 51 metabolites in IAA_24h (24 h after IAA treatment) vs. CK (sterilized ddH2O treatment) fruit, 55 metabolites in IAA_72h (72 h after IAA treatment) vs. CK, and 67 metabolites in IAA_24h vs. IAA_72h were found to be significantly different. KEGG analysis showed that the resistance induced in kiwifruit by IAA treatment was closely related to the activation of phenylpropanoids, including flavonoids and phenols, terpenoids, carbohydrate metabolism, and hormone signaling pathways. These results might reveal the mechanism of IAA-induced resistance in kiwifruit and provide a new theoretical basis for the safe and efficient control of postharvest diseases in kiwifruit.

Portable Electrochemical Sensing of Indole‐3‐acetic Acid Based on Self‐assembled MXene and Multi‐walled Carbon Nanotubes Composite Modified Screen‐printed Electrode

AbstractAs a typical plant hormone, indole‐3‐acetic acid (IAA) can regulate the biological activities including division, growth and differentiation of plant cells. In this paper, a MXene and multi‐walled carbon nanotubes composite was prepared by self‐assembly procedure, which was modified on screen‐printed electrode (SPE) to construct a wireless portable electrochemical sensor. Electrochemical investigations of IAA were studied by cyclic voltammetry and an irreversible oxidation process could be observed. The excellent electroanalytical method of IAA was realized on the modified SPE with the detection range as 0.05–125.0 μmol/L and the detection limit as 16.7 nmol/L. The sensor was used for IAA content analysis in different part of pea seedlings with satisfactory results.