Increase In Indole-3-acetic Acid Research Articles

The growth-promoting and disease-suppressing mechanisms of Trichoderma inoculation on peanut seedlings.

Trichoderma spp. is known for its ability to enhance plant growth and suppress disease, but the mechanisms for its interaction with host plants and pathogens remain unclear. This study investigated the transcriptomics and metabolomics of peanut plants (Arachis hypogaea L.) inoculated with Trichoderma harzianum QT20045, in the absence and presence of the stem rot pathogen Sclerotium rolfsii JN3011. Under the condition without pathogen stress, the peanut seedlings inoculated with QT20045 showed improved root length and plant weight, increased indole acetic acid (IAA) production, and reduced ethylene level, with more active 1-aminocyclopropane-1-carboxylate acid (ACC) synthase (ACS) and ACC oxidase (ACO), compared with the non-inoculated control. Under the pathogen stress, the biocontrol efficacy of QT20045 against S. rolfsii was 78.51%, with a similar effect on plant growth, and IAA and ethylene metabolisms to the condition with no biotic stress. Transcriptomic analysis of peanut root revealed that Trichoderma inoculation upregulated the expression of certain genes in the IAA family but downregulated the genes in the ACO family (AhACO1 and AhACO) and ACS family (AhACS3 and AhACS1) consistently in the absence and presence of pathogens. During pathogen stress, QT20045 inoculation leads to the downregulation of the genes in the pectinesterase family to keep the host plant's cell wall stable, along with upregulation of the AhSUMM2 gene to activate plant defense responses. In vitro antagonistic test confirmed that QT20045 suppressed S. rolfsii growth through mechanisms of mycelial entanglement, papillary protrusions, and decomposition. Our findings highlight that Trichoderma inoculation is a promising tool for sustainable agriculture, offering multiple benefits from pathogen control to enhanced plant growth and soil health.

Dietary tryptophan alleviates intestinal inflammation caused by long photoperiod via gut microbiota derived tryptophan metabolites-NLRP3 pathway in broiler chickens

Light pollution is a potential risk factor for intestinal health. Tryptophan plays an important role in the inhibition of intestinal inflammation. However, the mechanism of tryptophan in alleviating intestinal inflammation caused by long photoperiod is still unclear. This study investigated the anti-inflammatory effect of dietary tryptophan on intestinal inflammatory damage induced by long photoperiod and its potential mechanism in broiler chickens. We found that dietary tryptophan mitigated long photoperiod-induced intestinal tissue inflammatory damage and inhibited the activation of Nucleotide-Binding Oligomerization Domain, Leucine-Rich Repeat and Pyrin Domain-Containing 3 inflammasome. Moreover, dietary tryptophan significantly increased the relative abundance of Faecalibacterium, Enterococcus, and Lachnospiraceae_NC2004_group were significantly decreased the relative abundance of Ruminococcus_torques_group and norank_f_UCG-010 under the condition of long photoperiod (P < 0.05). The results of tryptophan targeted metabolomics show that tryptophan significantly increased indole-3-acetic acid (IAA) and indole-3 lactic acid (ILA), and significantly decreased xanthurenic acid (XA) under long photoperiod (P < 0.05). In conclusion, the results indicated that dietary tryptophan alleviates intestinal inflammatory damage caused by long photoperiod via the inhibition of Nucleotide-Binding Oligomerization Domain, Leucine-Rich Repeat and Pyrin Domain-Containing 3 inflammasome activation, which was mediated by tryptophan metabolites. Therefore, tryptophan supplementation could be a promising way to protect the intestine health under the condition of long photoperiod.

Gibberellin acid 4 and 7 increase indole-3-acetic acid production and induce cell division via PbCRF4-mediated activation of PbYUCCA6 expression in ‘Dangshansu’ pear

The role of gibberellins in inducing cell division is now widely recognized; however, the underlying mechanisms remain to be clarified. Here, we demonstrate that gibberellin acid 4 and 7 (GA4+7) can induce active cell division leading to ovary expansion as CPPU (N-(2‑chloro-4-pyridyl)-N’-phenylurea) at the early fruit setting stage in ‘Dangshansu’ pear (Pyrus bretshneideri Rehd.). Transcriptomic analysis showed PbCYTOKININ RESPONSE FACTOR4 (PbCRF4) was activated in response to GA4+7 and CPPU, suggesting a candidate gene correlated to gibberellin-induced cell division during early fruit development. Overexpression and RNA interference of PbCRF4 in pear calli demonstrated a role of PbCRF4 in regulating fruit cell proliferation and increased indole-3-acetic acid (IAA) biosynthesis. Ectopic overexpression of PbCRF4 in tomato produced flat fruits with no pointed tips, decreased the fruit index, and increased the pericarp thickness and IAA content. Silencing of SlCRF4 in tomato led to pointed-tip fruits with a relatively low IAA content and reduced pericarp thickness. Furthermore, PbCRF4 transcriptionally activated indole-3-pyruvate monooxygenase 6 (YUCCA6) to increase IAA content in pear. Taken together, this study reveals that GA4+7 induces cell division and an increase in IAA content via regulating PbCRF4 to activate the expression of PbYUCCA6, thereby contributing to the control of fruit shape.

Natural variants of molybdate transporters contribute to yield traits of soybean by affecting auxin synthesis

Soybean (Glycine max) is a crop with high demand for molybdenum (Mo) and typically requires Mo fertilization to achieve maximum yield potential. However, the genetic basis underlying the natural variation of Mo concentration in soybean and its impact on soybean agronomic performance is still poorly understood. Here, we performed a genome-wide association study (GWAS) to identify GmMOT1.1 and GmMOT1.2 that drive the natural variation of soybean Mo concentration and confer agronomic traits by affecting auxin synthesis. The soybean population exhibits five haplotypes of the two genes, with the haplotype 5 demonstrating the highest expression of GmMOT1.1 and GmMOT1.2, as well as the highest transport activities of their proteins. Further studies showed that GmMOT1.1 and GmMOT1.2 improve soybean yield, especially when cultivated in acidic or slightly acidic soil. Surprisingly, these two genes contribute to soybean growth by enhancing the activity of indole-3-acetaldehyde (IAAld) aldehyde oxidase (AO), leading to increased indole-3-acetic acid (IAA) synthesis, rather than being involved in symbiotic nitrogen fixation or nitrogen assimilation. Furthermore, the geographical distribution of five haplotypes in China and their correlation with soil pH suggest the potential significance of GmMOT1.1 and GmMOT1.2 in soybean breeding strategies.

A Plant Biostimulant from Ascophyllum nodosum Potentiates Plant Growth Promotion and Stress Protection Activity of Pseudomonas protegens CHA0

Abiotic stresses, including salinity stress, affect numerous crops, causing yield reduction, and, as a result, important economic losses. Extracts from the brown alga Ascophyllum nodosum (ANE), and compounds secreted by the Pseudomonas protegens strain, CHA0, can mitigate these effects by inducing tolerance against salt stress. However, the influence of ANE on P. protegens CHA0 secretion, and the combined effects of these two biostimulants on plant growth, are not known. Fucoidan, alginate, and mannitol are abundant components of brown algae and of ANE. Reported here are the effects of a commercial formulation of ANE, fucoidan, alginate, and mannitol, on pea (Pisum sativum), and on the plant growth-promoting activity of P. protegens CHA0. In most situations, ANE and fucoidan increased indole-3-acetic acid (IAA) and siderophore production, phosphate solubilization, and hydrogen cyanide (HCN) production by P. protegens CHA0. Colonization of pea roots by P. protegens CHA0 was found to be increased mostly by ANE and fucoidan in normal conditions and under salt stress. Applications of P. protegens CHA0 combined with ANE, or with fucoidan, alginate, and mannitol, generally augmented root and shoot growth in normal and salinity stress conditions. Real-time quantitative PCR analyses of P. protegens revealed that, in many instances, ANE and fucoidan enhanced the expression of several genes involved in chemotaxis (cheW and WspR), pyoverdine production (pvdS), and HCN production (hcnA), but gene expression patterns overlapped only occasionally those of growth-promoting parameters. Overall, the increased colonization and the enhanced activities of P. protegens CHA0 in the presence of ANE and its components mitigated salinity stress in pea. Among treatments, ANE and fucoidan were found responsible for most of the increased activities of P. protegens CHA0 and the improved plant growth.

Potassium ion regulates hormone, Ca2+ and H2O2 signal transduction and antioxidant activities to improve salt stress resistance in tobacco

Although improvement of plant salt tolerance by potassium ions (K+) has been widely studied, whether the tolerance is mediated via hormone signaling or antioxidant systems remains to be explored. This study combined plant physiology with transcriptomic techniques to study how K+ interacts with hormones and antioxidant enzymes to improve plant salt tolerance. Tobacco was used as the test material to study the effects of exogenous potassium application on photosynthetic function, hormone signal transduction, and reactive oxygen species (ROS) production under NaCl stress. The study also evaluated the function of the Ca2+ signaling pathway in salt stress tolerance. Transcriptome data showed that 4413 up-regulated genes and 3743 down-regulated genes were found in tobacco leaves treated with NaCl compared with the control. Compared with NaCl, the down-regulated genes in tobacco leaves were significantly reduced under NaCl + KCL treatment. The results showed that NaCl stress caused oxidative damage to tobacco leaves due to increased superoxide anion (O2−) content, superoxide dismutase (SOD) dismutates superoxide anion to produce hydrogen peroxide and the accumulation of H2O2 caused by reduced ascorbate peroxidase (APX) and peroxidase (POD) activities. NaCl stress also increased abscisic acid (ABA) content in tobacco leaves, resulting in stomatal closure and reduced photosynthetic capacity. Transcriptome data showed that 5 SOD, 1 POD, 1 CAT, 5 APX, and 3 GPX genes were significantly down-regulated by the NaCl treatment. Contrarily, NaCl + KCl treatment reduced the accumulation of O2−and SOD activity but increased POD activity, thereby reducing the accumulation of H2O2 and alleviating oxidative damage. The expression of 2 SOD and 3 APX and 2 GPX genes was significantly higher in NaCl + KCl treatment than that in NaCl treatment. Sufficient K+ also increased indole acetic acid (IAA) levels in tobacco leaves under NaCl stress but reduced ABA content, promoting stomatal opening and improving the photosynthetic capacity. In conclusion, K+ can improve plant salt tolerance by alleviating oxidative damage and regulating hormone signal transduction.

Ethylene and abscisic acid play a key role in modulating apple ripening after harvest and after cold-storage

An autocatalytic burst in ethylene production generally accompanies ripening of detached apple fruit. However, if apples are left to ripen attached to the tree, some cultivars, will not experience this autocatalytic ethylene production and the fruit will never acquire the organoleptic properties of detached ripened fruit. Accordingly, the present study aimed to understand how the hormonal crosstalk regulates ripening in ‘Golden Reinders’ apples, ripened on-tree, detached from the tree or after a period of cold storage, following the commercial harvest date. Our results showed that during on-tree ripening, ethylene production remained low, and no significant changes were observed in fruit colour or firmness. In fruit ripened detached from the tree, ethylene production was preceded by an increase of indole 3-acetic acid (IAA) and gibberellic acid (GA3) levels, whereas a cold-induced accumulation of jasmonic acid (JA) seemed to induce an earlier initiation of the climacteric burst in fruit ripened after cold storage. In both postharvest conditions, the accumulation of abscisic acid (ABA) may be either needed or facilitating the action of ethylene on triggering some ripening-related changes, pointing out the importance of both hormones in mediating apple ripening. In contrast, changes in sugars and ROS/antioxidants did not vary among the different ripening scenarios suggesting that none of the measured compounds may act as signalling molecules during apple ripening. Collectively, our results highlight that ethylene together with ABA played a crucial role in triggering ripening-related changes during postharvest ripening of ‘Golden Reinders’ apples.

Role of nanosilicab to boost the activities of metabolites in Triticum aestivum facing drought stress

This study was designed to assess the effect of nanosilicab fertilizer on Triticum aestivum under drought stress. The plants were grown in pots having the soil incubated with SiO2 NPs, biofertilizer and nanosilicab. The experimental design was completely randomized design and drought stress was applied at stem elongation stage. Plants were maintained in the pots till the collection of yield. Nanosilicab enhanced the germination percentage, germination index, and germination vigor index by 23.07%, 14.49%, and 93.10% under control and 14.42%, 10.52%, and 46.15% under drought stress. In the pot experiment, the soil was treated with 150 mg/kg silicon dioxide nanoparticles (SiO2), 1% biofertilizer and, 1% nanosilicab before sowing. Nanosilicab increased shoot length and root length by 34.77%, and 16.88% under control and 30.58%, and 21.56% under stress conditions, respectively. It also increased photosynthetic pigments, osmolytes content, relative water content, membrane stability index, phenol, and flavonoid content. The increase in antioxidant activity was significant by the application of nanosilicab i.e. the augmentation in catalase, peroxidase, and superoxide dismutase was 68.65%, 83.69%, and 85.99%, respectively. It also increased indole acetic acid and cytokinin by 22.28% and 14.79% in comparison to control. The improvement in hundred-grain weight and grains per spike by the use of nanosilicab was 36.25%, and 38.76% under control, and 27.47%, and 22.59% under stress conditions. The positive effect of nanosilicab on the roots of the plants improved the growth of plants significantly and this fertilizer showed potential for application on crops.

Reduction of Early Fruit Abscission by Main-branch-girdling in Macadamia Is Related to the Favorable Status of Carbohydrates and Endogenous Hormones

Fruit abscission occurring severely in the early fruit development affects macadamia yield. Developing effective methods to improve fruit retention is a priority for macadamia cultivation and production. Girdling is an important horticultural practice that has been widely used to increase fruit yield. Previous studies have shown that girdling fails to increase macadamia yield despite enhancing the early fruit set, but few have examined the effect of girdling on its related physiological mechanism. The objective of this study was to investigate the effects of main-branch girdling (MBG) on early fruit retention and also on the levels of carbohydrates and endogenous hormones in the leaves, bearing shoots and fruit of macadamia. Herein, MBG was performed at fruit set using a single-blade knife on 9-year-old macadamia trees (Macadamia integrifolia). Results showed that MBG significantly reduced young fruit drop, concurrent with significant increases in the contents of starch in both the leaves and the bearing shoots and in glucose, fructose, and sucrose levels in the husk and seed. It was suggested that the availability of carbohydrate for fruit retention was improved by MBG. Additionally, MBG increased indole-3-acetic acid (IAA), gibberellin (GA3), and zeatin-riboside (ZR, a type of cytokinin) concentrations and decreased abscisic acid (ABA) contents in the husk and the seed, indicating that MBG reduced the early fruit drop by modifying the balance of endogenous hormones. Therefore, a positive interplay between carbohydrates and endogenous hormones induced by MBG was involved in the reduction of early fruit abscission in macadamia.

Effect of dark septate endophytes on plant performance of Artemisia ordosica and associated soil microbial functional group abundance under salt stress

Fungal endophytes can improve plant tolerance to abiotic stress, however, the role of these plant–fungal interactions in desert species ecology and their management implications remain unclear. This study aimed to assess the effects of dark septate endophytes (DSE) on the performance of Artemisia ordosica and associated soil factors and microbial functional group abundance under salt stress. We investigated the effects of three DSE (Alternaria chlamydosporigena [AC], Paraphoma chrysanthemicola [PC] and Bipolaris sorokiniana [BS]) isolated from desert habitats on plant morphology, physiology and rhizosphere soil microhabitat of A. ordosica seedlings under different NaCl concentrations (0, 1, 2, 3 g NaCl/kg soil) in a growth chamber. The three DSE strains could colonize the roots of A. ordosica, and the symbiotic response with host plants depended on DSE species and NaCl concentration. The greatest benefits associated with DSE occurred under 1 g NaCl/kg soil. Specifically, AC promoted the accumulation of total biomass and enhanced superoxide dismutase (SOD) activity; PC promoted the accumulation of root biomass and increased indoleacetic acid (IAA) contents; and BS enhanced SOD activity and glutathione (GSH) and IAA contents. DSE reduced the root Na+ content. Interestingly, BS promoted gram-positive (G +) under 1 g NaCl/kg soil and the abundance of arbuscular mycorrhizal (AM) fungi under 3 g NaCl/kg soil. PC positively affected fungi, AM fungi, gram-negative (G −) bacteria and actinomycetes under 2 g NaCl/kg soil, and increased AM fungi and G – bacteria under 3 g NaCl/kg soil, while AC increased the abundance of all examined microbes under 3 g NaCl/kg soil. Structural equation modeling (SEM) demonstrated that DSE inoculation significantly influenced the relationship between the growth of A. ordosica, soil factors and rhizospheric microbial functional groups under NaCl stress treatments. DSE enhanced the root development of host plants and altered the soil nutrient content and microbiota under different NaCl concentrations, possibly contributing to plant growth and ecological adaptability under saline environment. These results contribute to the understanding of ecological function of DSE inoculation in improving the adaptability of plants to salt stress and may be used to promote vegetation restoration in salinized desert areas.

The role of AcPGIP in the kiwifruit (Actinidia chinensis) response to Botrytis cinerea.

Kiwifruit (Actinidia chinensis) is rich in nutritional and medicinal value. However, the organism responsible for grey mould, Botrytis cinerea, causes great economic losses and food safety problems to the kiwifruit industry. Understanding the molecular mechanism underlying postharvest kiwifruit responses to B. cinerea is important for preventing grey mould decay and enhancing resistance breeding. Kiwifruit cv. 'Hongyang' was used as experimental material. The AcPGIP gene was cloned and virus-induced gene silencing (VIGS) was used to explore the function of the polygalacturonase inhibiting protein (PGIP) gene in kiwifruit resistance to B. cinerea. Virus-induced silencing of AcPGIP resulted in enhanced susceptibility of kiwifruit to B. cinerea. Antioxidant enzymes, secondary metabolites and endogenous hormones were analysed to investigate kiwifruit responses to B. cinerea infection. Kiwifruit effectively activated antioxidant enzymes and secondary metabolite production in response to B. cinerea, which significantly increased Indole-3-acetic acid (IAA), gibberellin 3 (GA3) and abscisic acid (ABA) content relative to those in uninfected fruit. Silencing of AcPGIP enabled kiwifruit to quickly activate hormone-signaling pathways through an alternative mechanism to trigger defence responses against B. cinerea infection. These results expand our understanding of the regulatory mechanism for disease resistance in kiwifruit; further, they provide gene-resource reserves for molecular breeding of kiwifruit for disease resistance.

Saccharomyces boulardii CNCM I-745 modulates the microbiota-gut-brain axis in a humanized mouse model of Irritable Bowel Syndrome.

Gnotobiotic mice colonized with microbiota from patients with irritable bowel syndrome (IBS) and comorbid anxiety (IBS+A) display gut dysfunction and anxiety-like behavior compared to mice colonized with microbiota from healthy volunteers. Using this model, we tested the therapeutic potential of the probiotic yeast Saccharomyces boulardii strain CNCM I-745 (S.bou) and investigated underlying mechanisms. Germ-free Swiss Webster mice were colonized with fecal microbiota from an IBS+A patient or a healthy control (HC). Three weeks later, mice were gavaged daily with S.boulardii or placebo for two weeks. Anxiety-like behavior (light preference and step-down tests), gastrointestinal transit, and permeability were assessed. After sacrifice, samples were taken for gene expression by NanoString and qRT-PCR, microbiota 16S rRNA profiling, and indole quantification. Mice colonized with IBS+A microbiota developed faster gastrointestinal transit and anxiety-like behavior (longer step-down latency) compared to mice with HC microbiota. S.bou administration normalized gastrointestinal transit and anxiety-like behavior in mice with IBS+A microbiota. Step-down latency correlated with colonic Trpv1 expression and was associated with altered microbiota profile and increased Indole-3-acetic acid (IAA) levels. Treatment with S. bou improves gastrointestinal motility and anxiety-like behavior in mice with IBS+A microbiota. Putative mechanisms include effects on pain pathways, direct modulation of the microbiota, and indole production by commensal bacteria.

AMF inoculation and phosphorus supplementation alleviates drought induced growth and photosynthetic decline in Nicotiana tabacum by up-regulating antioxidant metabolism and osmolyte accumulation

Arbuscular mycorrhizal fungi (AMF) improves phosphorus (P) uptake in plants and regulates growth under environmental stresses. Present trials were undertaken to study the effect of phosphorus (P, 40 mg kg−1 soil) supplementation and AMF (Glomus versiforme) inoculation on the growth performance of tobacco (Nicotiana tabacum L. variety Yunyan 87) under drought stress. Supplementation of P and inoculation of AMF significantly enhanced growth, biomass accumulation and root activity of tobacco plants under normal conditions and mitigated the drought induced decline. Chlorophyll and carotenoid contents, photosynthesis and PSII efficiency increased due to AMF and P treatment attaining maximal values due to their combined treatment. Drought resulted in generation of reactive oxygen species (ROS) like superoxide (O2−) and hydrogen peroxide (H2O2) resulting in increased lipid peroxidation hence reducing membrane stability. Plants inoculated with AMF and/or supplemented with P exhibited reduced accumulation of ROS and lipid peroxidation. Content of osmolytes including proline, sugars and free amino acids were enhanced due to P and AMF treatment under normal as well as drought conditions that influenced the leaf relative water content. Reduction in oxidative damage in AMF and P treated plants was apparently linked with the stimulation of antioxidant system in them. Activities of SOD, CAT, APX, POD and GR, and the content of AsA and GSH improved significantly due to P and AMF treatment both under normal and drought conditions thereby ameliorating the oxidative effects. Further, accumulation of phenols increased more obviously due to P and/or AMF inoculation than in drought. Increased osmolyte and phenol content due to P and/or AMF helped tobacco plants to counteract the drought mediated damage by strengthening the non-enzymatic antioxidant system. P and/or AMF ameliorated the decline in contents of nitrogen, potassium and phosphorous, and activity of nitrate reductase more due to their combined treatments. Drought induced decline in nicotine content was mitigated because of P and/or AMF treatment. Additionally, mycorrhizal inoculation along with P supplementation increased indole-3-acetic acid (IAA) and abscisic acid (ABA) concentrations both in roots and leaves under drought stress. Hence P supplementation along with AMF inoculation mitigates the photosynthetic alteration and growth in tobacco plants by up-regulating antioxidant system and osmolyte accumulation.

Pruning length of lateral branches affects tomato growth and yields in relation to auxin-cytokinin crosstalt

Lateral branches (LBs) pruning is performed frequently to keep the tomato plants in optimal growth conditions. However, the suitable pruning length of LBs, as well as the physiological and molecular mechanisms of pruning length on plant growth regulation remains elusive in tomato. The effects of pruning length of LBs from 0 to 20 cm on vegetative growth, reproductive growth, labor costs, hormone metabolism and genes transcripts were evaluated in an indeterminate type tomato cultivar. By comprehensive analysis, we provided evidence that pruning length of LBs at about 6–7 cm was suitable for plant growth, high yield, and low labor costs in tomato production. For mechanisms, appropriate extension of pruning length of LBs increased indole acetic acid (IAA) concentrations in root, which promoted the biosynthesis and upward transport of inactive cytokinins (CKs), as well as root development. Meanwhile, existence of LBs inhibited the auxin outflow of the lower flower stalks by regulating transcripts of AUX1 and PIN. Then, the enhanced concentrations of IAA and CKs in ovary could promote fruit swelling. Additionally, pruning length of LBs also influenced the leaf senescence to control photosynthesis. Taken together, we highlight that pruning length of LBs influence auxin and cytokinins homeostasis in relation to growth and yield in tomato plants.

The plant-growth promoting bacteria promote cadmium uptake by inducing a hormonal crosstalk and lateral root formation in a hyperaccumulator plant Sedum alfredii

Plant growth-promoting bacteria (PGPB) that inhabit hyperaccumulating plants assist cadmium (Cd) absorption, but the underlying mechanism has not been comprehensively studied. For this reason, we combined the fluorescence imaging, and transcriptomic and metabolomic methods in a Cd hyperaccumulator, Sedum alfredii, inoculated or not with PGPB Pseudomonas fluorescens. The results showed that the newly emerged lateral roots, that were heavily colonized by P. fluorescens, are the main entry for Cd influx in S. alfredii. Inoculation with P. fluorescens promoted a lateral root formation of its host plant, leading to a higher Cd phytoremediation efficiency. Furthermore, the plant transcriptome revealed that 146 plant hormone related genes were significantly up-regulated by the bacterial inoculation, with 119 of them showing a complex interaction, which suggests that a hormonal crosstalk participated root development. The targeted metabolomics analysis showed that P. fluorescens inoculation significantly increased indole acetic acid concentration and significantly decreased concentrations of abscisic acid, brassinolide, trans-zeatin, ethylene and jasmonic acid in S. alfredii roots, thereby inducing lateral root emergence. Altogether, our results highlight the importance of PGPB-induced lateral root formation for the increased Cd uptake in a hyperaccumulating plant.

Co-existence of Leclercia adecarboxylata (LSE-1) and Bradyrhizobium sp. (LSBR-3) in nodule niche for multifaceted effects and profitability in soybean production.

The present study was designed with the objective of improving growth and nodulation of soybean [Glycine max (L.) Merill] with co-inoculation of native Bradyrhizobium sp. (LSBR-3) (KF906140) and non-rhizobial nodule endophytic diazotroph Leclercia adecarboxylata (LSE-1) (KX925974) with multifunctional plant growth promoting (PGP) traits in cereal based cropping system (Rice-Wheat). A total of 40 endophytic bacteria from cultivated and wild sp. of soybean were screened for multifarious PGP traits and pathogenicity test. Based on PGP traits, antagonistic activities and bio-safety test; L. adecarboxylata (LSE-1) was identified with 16 S rRNA gene sequencing along with the presence of nifH (nitrogen fixation) and ipdc (IAA production) genes. Dual inoculant LSE-1 and LSBR-3 increased indole acetic acid (IAA), P & Zn-solubilization, 1-aminocyclopropane-1-carboxylate deaminase (ACCD) activity, siderophore, biofilm formation and exo-polysaccharides in contrast to single inoculation treatment. Further, assessment of dual inoculant LSBR-3 + LSE-1 improved growth parameters, nodulation, soil enzymes activities, nutrient accumulation and yield as compared to single as well as un-inoculated control treatment under field conditions. Single inoculant LSBR-3 improved yield by 8.84% over control. Further, enhancement of 4.15% grain yield was noticed with LSBR-3 + LSE-1 over LSBR-3 alone treatment. Application of LSBR-3 + LSE-1 gave superior B:C ratio (1.29) and additional income approximately 116USDha-1 in contrast to control treatment. The present results thus, is the first report of novel endophytic diazotroph L. adecarboxylata (LSE-1) as PGPR from Indian conditions particularly in Punjab region for exploiting as potential PGPR along with Bradyrhizobium sp. (LSBR-3) in soybean.

The influence of nitrogen availability on anatomical and physiological responses of Populus alba \xd7 P. glandulosa to drought stress

BackgroundDrought and nitrogen (N) deficiency are two major limiting factors for forest productivity in many ecosystems. Elucidating the mechanisms underlying the influence of soil N availability on drought responses of tree species is crucial to improve tree growth under drought.ResultsThe root proliferation under drought was enhanced by adequate N application. Vessel frequency in xylem increased upon drought, with more significant increase under adequate N conditions compared with that under low N conditions, possibly leading to increased hydraulic safety. Nitrogen application under drought increased indole acetic acid (IAA), which contributed to the adaptive changes of xylem. Nitrogen application increased leaf abscisic acid (ABA) concentration, therefore regulated stomata adjustment, and promoted intrinsic water use efficiency (WUEi). Moreover, N application promoted antioxidant defense in leaves by showing increased level of free proline and carotenoid, which improved drought tolerance and growth performance of poplars.ConclusionsAnatomical and physiological responses of Populus to drought were suppressed by N deficiency. Adequate N application promoted adaptive changes of root and xylem under drought and increased hydraulic safety. Nitrogen addition under drought also increased leaf ABA level which may regulate stomata adjustment and promote WUEi. Moreover, nitrogen application improved antioxidant defense in leaves with increased levels of antioxidants. These positive regulations improved drought tolerance and growth performance of poplars.

The effects of mepiquat chloride on the lateral root initiation of cotton seedlings are associated with auxin and auxin-conjugate homeostasis

BackgroundMepiquat chloride (MC) is a plant growth regulator widely used in cotton (Gossypium hirsutum L.) production to suppress excessive vegetative growth, increase root growth and avoid yield losses. To increase root growth, cotton seeds were treated with MC to increase the number of lateral root (LRs) and improve drought resistance. An increased indole-3-acetic acid (IAA) pool appeared to correlate with LR growth, and the principal source of IAA in germinating seeds is IAA conjugates. Here, the role of IAA homeostasis and signaling was investigated in cotton seedlings treated with MC.ResultsIn the present research, MC significantly increased endogenous IAA levels in the roots, which promoted lateral root initiation (LRI) by upregulating GhARF7/19 and GhLBD18s and subsequently increasing LR quantity and elongation. The levels of IAA-amide conjugates significantly decreased in MC-treated seedlings compared with untreated control seedlings. Sixteen members of the cotton IAA amidohydrolase (IAH) gene family were identified, of which GhIAR3a, GhIAR3b, GhILR1, GhILL3 and GhILL6 were expressed during cotton seed germination. Compared with those in untreated control seedlings, the expression levels of GhIAR3a, GhIAR3b, GhILR1 and GhILL6 in the MC-treated seedlings were markedly elevated. The GhIAR3a/b and GhILR1 genes were cloned and expressed in Escherichia coli; these recombinant proteins exhibited hydrolytic activity that could cleave IAA-phenyalanine (Phe), IAA-methionine (Met), IAA-glycine (Gly) and IAA-leucine (Leu) in vitro, while only GhIAR3a hydrolyzed IAA-alanine (Ala) efficiently. The content of GhIAR3a, as detected via an established sandwich enzyme-linked immunosorbent assay (ELISA), increased in the MC-treated seedlings compared with the untreated control seedlings. In addition, the Arabidopsis iar3 mutant was less responsive to MC-induced LR growth than was wild type.ConclusionsThese findings suggested that MC application could mediate IAA homeostasis via increased IAA levels from IAA-amide conjugate hydrolysis by accelerating IAH gene expression, which might promote LRI and increase the LR quantity and elongation.

Metabolic and biochemical responses of Potamogeton anguillanus Koidz. (Potamogetonaceae) to low oxygen conditions

Oxygen availability in water is considered one of the most important factors for growth and productivity in aquatic submerged macrophytes. In the present study, the growth, stress responses, and metabolic changes in Potamogeton anguillanus Koidz. (Potamogetonaceae) were assessed after a 21-day exposure to low (hypoxia; dissolved oxygen, DO < 1 mg/L) or null (anoxia) oxygen concentrations in water. High growth rates and an increased indole acetic acid (IAA) content in P. anguillanus were observed under the hypoxic conditions (4-fold to control) compared to the anoxic conditions. In addition, the activation of glycolysis and fermentation processes was further recorded, given the increase in alcohol dehydrogenase activity and pyruvate concentration on the studied plants that were exposed to low oxygen concentrations. Moreover, the positive correlations of antioxidative enzyme activities, catalase (CAT) and guaiacol peroxidase (POD) with hydrogen peroxide (H2O2) confirmed the species ability to scavenge excess H2O2 under low oxygen stress. The capillary electrophoresis–mass spectrometry (CE-MS) analysis of the metabolome identified metabolite accumulations (e.g., glutamate, glutamine, aspartate, asparagine, valine, malate, lactate, citrate, isocitrate, proline and γ-amino butyric acid) in response to the anoxia.

Reduction of Tomato-Plant Chilling Tolerance by CRISPR-Cas9-Mediated SlCBF1 Mutagenesis.

Chilling stress is the main constraint in tomato ( Solanum lycopersicum) production, as this is a chilling-sensitive horticultural crop. The highly conserved C-repeat binding factors (CBFs) are cold-response-system components found in many species. In this study, we generated slcbf1 mutants using the CRISPR-Cas9 system and investigated the role of SlCBF1 in tomato-plant chilling tolerances. The slcbf1 mutants exhibited more severe chilling-injury symptoms with higher electrolyte leakage and malondialdehyde levels than wild-type (WT) plants. Additionally, slcbf1 mutants showed lower proline and protein contents and higher hydrogen peroxide contents and activities of antioxidant enzymes than WT plants. Knockout of SlCBF1 significantly increased indole acetic acid contents but decreased methyl jasmonate, abscisic acid, and zeatin riboside contents. The reduced chilling tolerance of the slcbf1 mutants was further reflected by the down-regulation of CBF-related genes. These results contribute to a better understanding of the molecular basis underlying SlCBF1 mediation of tomato chilling sensitivity.