Plant Auxin Research Articles

LYCHOS is a human hybrid of a plant-like PIN transporter and a GPCR

Lysosomes have crucial roles in regulating eukaryotic metabolism and cell growth by acting as signalling platforms to sense and respond to changes in nutrient and energy availability1. LYCHOS (GPR155) is a lysosomal transmembrane protein that functions as a cholesterol sensor, facilitating the cholesterol-dependent activation of the master protein kinase mechanistic target of rapamycin complex 1 (mTORC1)2. However, the structural basis of LYCHOS assembly and activity remains unclear. Here we determine several high-resolution cryo-electron microscopy structures of human LYCHOS, revealing a homodimeric transmembrane assembly of a transporter-like domain fused to a G-protein-coupled receptor (GPCR) domain. The class B2-like GPCR domain is captured in the apo state and packs against the surface of the transporter-like domain, providing an unusual example of a GPCR as a domain in a larger transmembrane assembly. Cholesterol sensing is mediated by a conserved cholesterol-binding motif, positioned between the GPCR and transporter domains. We reveal that the LYCHOS transporter-like domain is an orthologue of the plant PIN-FORMED (PIN) auxin transporter family, and has greater structural similarity to plant auxin transporters than to known human transporters. Activity assays support a model in which the LYCHOS transporter and GPCR domains coordinate to sense cholesterol and regulate mTORC1 activation.

Genome-wide analysis and expression characteristics of Small Auxin-up RNAs genes in flax (Linum usitatissimum L.)

Plant auxin is crucial in regulating many aspects of plant growth and development. Small Auxin-up RNAs (SAURs) genes act as the main early auxin response genes and are involved in regulating plant growth and development. Flax is a well-known fiber and oil crop; thus, our study provided a systematic bioinformatics analysis of the SAUR family in flax, including basic parameters, gene structure, chromosomal location, phylogenetic analysis, and cis-acting element analysis. Based on genomic information, 86 LusSAUR genes were identified and separated into eight groups. The gene structure analysis revealed that only two LusSAUR genes have introns. The cis-acting elements related to hormones and stress were abundant in the promoter region of LusSAUR members. Based on the gene expression oligo microarray, LusSAUR genes had tissue-specific expression characteristics in eight different tissues. Quantitative real-time PCR analysis indicated that 10 selected LusSAUR genes could be quickly upregulated following treatment with IAA. The 10 genes displayed distinctive expression levels under hormone treatment (MeJA, ABA, SA) and abiotic stress (PEG, NaCl, CdCl2). This study provides a foundation for further investigations for functional analysis of LusSAURs in flax. Furthermore, it will provide useful insights for further research into the molecular mechanism of regulating hormones and environmental signals in flax growth and development.

Plant growth promoting signatory volatiles emitted by a drought-tolerant bacterium Bacillus altitudinis FD48 and its role in moisture stress alleviation in rice (Oryza sativa L.)

Increasing evidence implies that bacterial volatile organic compounds (bVOCs) play a significant role in plant-microbe interaction. Plant associated bacteria produces plant growth modulating volatiles elicits induced systemic tolerance (IST) in plants against a multitude of abiotic stress. Induction of IST and plant growth promotion by signatory bVOCs of Bacillus altitudinis FD48 against drought are reported in this study. The rice seedlings exposed to bVOCs blends of FD48 showed a one-fold increase in whole plant biomass and auxin content (3 µmol g-1 FW) under induced moisture stress. The effect of bVOCs highly depends on the inoculum load. Higher inoculum quantity (100 µL) is detrimental to plant growth. bVOCs produced by FD48 profiled at different growth intervals in GC–MS-ATD revealed a total of 40 bioactive compounds both under stress (PEG 6000) and non-stressed conditions. Interestingly, potential plant growth-promoting compounds such as 1-Hexanol, 2,3-butanediol, dimethyl disulfide, benzene, butanoic acid, pentadecane, and acetic acid are more pronounced. Few compounds produced under non-stress were found to increase during stress (example, 2,3-Butanediol, and acetic acid). This study unraveled the significant biosynthetic pathways induced by FD48 bVOC blends, such as pyruvate metabolism, tryptophan metabolism, sulfur metabolism, fatty acid biosynthesis, and ethanol degradation that anchors in abating moisture stress. Hence, it can be concluded that PGPB B. altitudinis FD48 produced bVOCs could be potential orchestrators of induced systemic tolerance in plants against moisture stress.

Advances in Plant Auxin Biology: Synthesis, Metabolism, Signaling, Interaction with Other Hormones, and Roles under Abiotic Stress.

Auxin is a key hormone that regulates plant growth and development, including plant shape and sensitivity to environmental changes. Auxin is biosynthesized and metabolized via many parallel pathways, and it is sensed and transduced by both normal and atypical pathways. The production, catabolism, and signal transduction pathways of auxin primarily govern its role in plant growth and development, and in the response to stress. Recent research has discovered that auxin not only responds to intrinsic developmental signals, but also mediates various environmental signals (e.g., drought, heavy metals, and temperature stresses) and interacts with hormones such as cytokinin, abscisic acid, gibberellin, and ethylene, all of which are involved in the regulation of plant growth and development, as well as the maintenance of homeostatic equilibrium in plant cells. In this review, we discuss the latest research on auxin types, biosynthesis and metabolism, polar transport, signaling pathways, and interactions with other hormones. We also summarize the important role of auxin in plants under abiotic stresses. These discussions provide new perspectives to understand the molecular mechanisms of auxin's functions in plant development.

Genetically Encoded, Noise-Tolerant, Auxin Biosensors in Yeast.

Auxins are crucial signaling molecules that regulate the growth, metabolism, and behavior of various organisms, most notably plants but also bacteria, fungi, and animals. Many microbes synthesize and perceive auxins, primarily indole-3-acetic acid (IAA, referred to as auxin herein), the most prevalent natural auxin, which influences their ability to colonize plants and animals. Understanding auxin biosynthesis and signaling in fungi may allow us to better control interkingdom relationships and microbiomes from agricultural soils to the human gut. Despite this importance, a biological tool for measuring auxin with high spatial and temporal resolution has not been engineered in fungi. In this study, we present a suite of genetically encoded, ratiometric, protein-based auxin biosensors designed for the model yeast Saccharomyces cerevisiae. Inspired by auxin signaling in plants, the ratiometric nature of these biosensors enhances the precision of auxin concentration measurements by minimizing clonal and growth phase variation. We used these biosensors to measure auxin production across diverse growth conditions and phases in yeast cultures and calibrated their responses to physiologically relevant levels of auxin. Future work will aim to improve the fold change and reversibility of these biosensors. These genetically encoded auxin biosensors are valuable tools for investigating auxin biosynthesis and signaling in S. cerevisiae and potentially other yeast and fungi and will also advance quantitative functional studies of the plant auxin perception machinery, from which they are built.

Advances in studies on adventitious root formation determined by juvenility and auxin in plants

Advances in studies on adventitious root formation determined by juvenility and auxin in plants

Different viral effectors hijack TCP17, a key transcription factor for host Auxin synthesis, to promote viral infection.

Auxin is an important class of plant hormones that play an important role in plant growth development, biotic stress response, and viruses often suppress host plant auxin levels to promote infection. However, previous research on auxin-mediated disease resistance has focused mainly on signaling pathway, and the molecular mechanisms of how pathogenic proteins manipulate the biosynthetic pathway of auxin remain poorly understood. TCP is a class of plant-specific transcription factors, of which TCP17 is a member that binds to the promoter of YUCCAs, a key rate-limiting enzyme for auxin synthesis, and promotes the expression of YUCCAs, which is involved in auxin synthesis in plants. In this study, we reported that Tomato spotted wilt virus (TSWV) infection suppressed the expression of YUCCAs through its interaction with TCP17. Further studies revealed that the NSs protein encoded by TSWV disrupts the dimerization of TCP17, thereby inhibit its transcriptional activation ability and reducing the auxin content in plants. Consequently, this interference inhibits the auxin response signal and promotes the TSWV infection. Transgenic plants overexpressing TCP17 exhibit resistance against TSWV infection, whereas plants knocking out TCP17 were more susceptible to TSWV infection. Additionally, proteins encoded by other RNA viruses (BSMV, RSV and TBSV) can also interact with TCP17 and interfere with its dimerization. Notably, overexpression of TCP17 enhanced resistance against BSMV. This suggests that TCP17 plays a crucial role in plant defense against different types of plant viruses that use viral proteins to target this key component of auxin synthesis and promote infection.

Plant Hormone Pathway Is Involved in Regulating the Embryo Development Mechanism of the Hydrangea macrophylla Hybrid.

The research is aimed to elucidate the role of plant hormones in regulating the development of hybrid embryos in Hydrangea macrophylla. Fruits from the intraspecific cross of H. macrophylla 'Otaksa' × 'Coerulea' were selected at the globular, heart, and torpedo stages of embryo development. Transcriptome sequencing and differential gene expression analysis were conducted. The results showed that fruit growth followed a single "S-shaped growth curve, with globular, heart, and torpedo embryos appearing at 30, 40, and 50 d post-pollination, respectively, and the embryo maintaining the torpedo shape from 60 to 90 d. A total of 12,933 genes was quantified across the three developmental stages, with 3359, 3803, and 3106 DEGs in the S1_vs_S2, S1_vs_S3, and S2_vs_S3 comparisons, respectively. Among these, 133 genes related to plant hormone biosynthesis and metabolism were differentially expressed, regulating the synthesis and metabolism of eight types of plant hormones, including cytokinin, auxin, gibberellin, abscisic acid, and jasmonic acid. The pathways with the most differentially expressed genes were cytokinin, auxin, and gibberellin, suggesting these hormones may play crucial roles in embryo development. In the cytokinin pathway, CKX (Hma1.2p1_0579F.1_g182670.gene, Hma1.2p1_1194F.1_g265700.gene, and NewGene_12164) genes were highly expressed during the globular embryo stage, promoting rapid cell division in the embryo. In the auxin pathway, YUC (Hma1.2p1_0271F.1_g109005.gene and Hma1.2p1_0271F.1_g109020.gene) genes were progressively up-regulated during embryo growth; the early response factor AUX/IAA (Hma1.2p1_0760F.1_g214260.gene) was down-regulated, while the later transcriptional activator ARF (NewGene_21460, NewGene_21461, and Hma1.2p1_0209F.1_g089090.gene) was up-regulated, sustaining auxin synthesis and possibly preventing the embryo from transitioning to maturity. In the gibberellin pathway, GA3ox (Hma1.2p1_0129F.1_g060100.gene) expression peaked during the heart embryo stage and then declined, while the negative regulator GA2ox (Hma1.2p1_0020F.1_g013915.gene) showed the opposite trend; and the gibberellin signaling repressor DELLA (Hma1.2p1_1054F.1_g252590.gene) increased over time, potentially inhibiting embryo development and maintaining the torpedo shape until fruit maturity. These findings preliminarily uncover the factors affecting the development of hybrid H. macrophylla embryos, laying a foundation for further research into the regulatory mechanisms of H. macrophylla hybrid embryo development.

OsMYB14, an R2R3-MYB transcription factor, regulates plant height through the control of hormone metabolism in rice

Plant growth must be regulated throughout the plant life cycle. The myeloblastosis (MYB) transcription factor (TF) family is one of the largest TF families and is involved in metabolism, lignin biosynthesis, and developmental processes. Here, we showed that OsMYB14, a rice R2R3-MYB TF, was expressed in leaves and roots, especially in rice culm and panicles, and that it localized to the nucleus. Overexpression of OsMYB14 (OsMYB14-ox) in rice resulted in a 30% reduction in plant height compared to that of the wild type (WT), while the height of the osmyb14-knockout (osmyb14-ko) mutant generated using the CRISPR/Cas9 system was not significantly different. Microscopic observations of the first internode revealed that the cell size did not differ significantly among the lines. RNA sequencing analysis revealed that genes associated with plant development, regulation, lipid metabolism, carbohydrate metabolism, and gibberellin (GA) and auxin metabolic processes were downregulated in the OsMYB14-ox line. Hormone quantitation revealed that inactive GA19 accumulated in OsMYB14-ox but not in the WT or knockout plants, suggesting that GA20 generation was repressed. Indole-3-acetic acid (IAA) and IAA-aspartate accumulated in OsMYB14-ox and osmyb14-ko, respectively. Indeed, real-time PCR analysis revealed that the expression of OsGA20ox1, encoding GA20 oxidase 1, and OsGH3-2, encoding IAA-amido synthetase, was downregulated in OsMYB14-ox and upregulated in osmyb14-ko. A protein-binding microarray revealed the presence of a consensus DNA-binding sequence, the ACCTACC-like motif, in the promoters of the OsGA20ox1 and GA20ox2 genes. These results suggest that OsMYB14 may act as a negative regulator of biological processes affecting plant height in rice by regulating GA biosynthesis and auxin metabolism.

Zinc-Enhanced Regulation of the Ginkgo biloba L. Response and Secondary Metabolites

Ginkgo biloba L. leaves are rich in secondary metabolites with important medicinal values; to increase their contents, foliar spraying of micronutrients is a potential strategy. Zinc, a multifunctional element, has a significant impact on the content of secondary metabolites in other plants, but relevant research into ginkgo is still lacking. In our study, different spraying time and concentration strategies were used to investigate the effects of zinc sulfate (ZnSO4) on physiological indicators and secondary metabolites of 2-year-old ginkgo. The results demonstrated that ZnSO4 could increase the contents of hydrogen peroxide, abscisic acid, and free amino acids in ginkgo leaves. It also enhances the antioxidant enzyme activity of ginkgo leaves, decreases the content of plant auxin, and ultimately facilitates the accumulation of ginkgo terpene lactones (TTL). Spraying ZnSO4 in June resulted in a more significant increase in the contents of TTL and flavonoids compared to spraying in August. After spraying 12 mmol/L ZnSO4 in June, the contents of TTL and flavonoids in ginkgo leaves were significantly elevated by 35.95% and 24.30%, respectively, compared to those in the CK (p < 0.05). The contents of ginkgolide A, B, and C were notably increased by 45.93%, 46.56%, and 74.29%, respectively, compared to those in the CK (p < 0.05). Therefore, our study suggests that the optimal timing for spraying ZnSO4 on ginkgo is in June, with a recommended concentration of 12 mmol/L. Our study provides a theoretical basis for the accumulation of secondary metabolites in ginkgo and guides the production of its leaf-utilization plantations.

Effect of Leaf Pruning and Additional Fertilizer on Growth and Young Pods Yield of Winged Beans

Winged bean (Psophocarpus tetragonolobus L.) exhibits luxuriant foliage, making leaf pruning essential to enhance sunlight interception. Additionally, supplementing with additional fertilizer helps offset the impact of gradual harvesting. Therefore, this research aimed to determine the effect of leaf pruning and additional fertilizer on the growth and yield parameter of winged beans in the Institut Pertanian Bogor (IPB) experimental station at Leuwikopo, IPB University, Bogor, Indonesia. A randomized complete block design was used with two factors and three replications, namely leaf pruning intensities (0, 15, and 30% leaf pruning) and rates of additional fertilizer (0, 6.25, 12.5, and 18.5 g NPK 16-16-16/plant). The observed variables were plant height, leaf number, root length, leaf nutrient, auxin content, nutrient uptake, and young pods yield. The findings revealed that the interaction of pruning intensities and additional fertilizer rates significantly influenced leaf number and root length. Specifically, plants receiving a treatment combination without pruning and 6.25 g of additional fertilizer/plant exhibited the highest leaf number. In contrast, those subjected to 15% leaf pruning showed the greatest root length. Leaf nutrient levels, auxin content, and nutrient uptake exhibited noticeable improved with the addition of fertilizer. Meanwhile, a higher phosphorus and organic carbon content was observed in the 15% pruning treatment, and the young pods yield were not affected because the Fairuz variety reached its potential yield. Based on the results, the most recommended treatment is a combination without leaf pruning, supplemented with 6.25 g of additional fertilizer/plant.

Effectiveness of Nanoformulated Plant Growth Regulators in the Production and Propagation of High-value Crops and Ornamentals

Among the major classes of plant hormones, auxins, gibberellins, and cytokinins are widely used for plant propagation. These hormones influence the physiological and developmental processes of plants such as root initiation, apical dominance, seed germination, leaf expansion, and development of buds, flowers, and fruits. Its exogenous application was found to significantly improve the growth of several important plants. This study aimed to determine the effectiveness of plant growth regulators (PGRs) derived from naturally occurring plant growth-promoting bacteria (PGPBs) in the production and propagation of selected crops. In this study, indole- 3-acetic acid (IAA) and gibberellic acid (GA) were extracted from naturally occurring PGPB Bacillus sp. The extracted hormone was nanoformulated for controlled release and increased uptake in plants. The nanoformulated hormones were applied in the propagation of coffee and the production of eggplant and ornamentals. Results showed that the application of nanoformulated IAA (Nano-IAA) significantly increased the survival rate of coffee compared to the commercially available auxin. Nano-IAA increased the germination rate of eggplant in acidic soil and root emergence of Bougainvillea over the negative control (water) but was comparable to that of the commercially available auxin. The nanoformulated GAs and commercially available

Dissecting the Roles of the Cytokinin Signaling Network: The Case of De Novo Shoot Apical Meristem Formation.

Numerous biotechnological applications require a fast and efficient clonal propagation of whole plants under controlled laboratory conditions. For most plant species, the de novo regeneration of shoots from the cuttings of various plant organs can be obtained on nutrient media supplemented with plant hormones, auxin and cytokinin. While auxin is needed during the early stages of the process that include the establishment of pluripotent primordia and the subsequent acquisition of organogenic competence, cytokinin-supplemented media are required to induce these primordia to differentiate into developing shoots. The perception of cytokinin through the receptor ARABIDOPSIS HISTIDINE KINASE4 (AHK4) is crucial for the activation of the two main regulators of the establishment and maintenance of shoot apical meristems (SAMs): SHOOTMERISTEMLESS (STM) and the WUSCHEL-CLAVATA3 (WUS-CLV3) regulatory circuit. In this review, we summarize the current knowledge of the roles of the cytokinin signaling cascade in the perception and transduction of signals that are crucial for the de novo establishment of SAMs and lead to the desired biotechnological output-adventitious shoot multiplication. We highlight the functional differences between individual members of the multigene families involved in cytokinin signal transduction, and demonstrate how complex genetic regulation can be achieved through functional specialization of individual gene family members.

Transcription factor WRKY75 maintains auxin homeostasis to promote tomato defense against Pseudomonas syringae.

The hemibiotrophic bacterial pathogen Pseudomonas syringae infects a range of plant species and causes enormous economic losses. Auxin and WRKY transcription factors play crucial roles in plant responses to P. syringae, but their functional relationship in plant immunity remains unclear. Here, we characterized tomato (Solanum lycopersicum) SlWRKY75, which promotes defenses against P. syringae pv. tomato (Pst) DC3000 by regulating plant auxin homeostasis. Overexpressing SlWRKY75 resulted in low free indole-3-acetic acid (IAA) levels, leading to attenuated auxin signaling, decreased expansin transcript levels, upregulated expression of PATHOGENESIS-RELATED GENES (PRs) and NONEXPRESSOR OF PATHOGENESIS-RELATED GENE 1 (NPR1), and enhanced tomato defenses against Pst DC3000. RNA interference-mediated repression of SlWRKY75 increased tomato susceptibility to Pst DC3000. Yeast one-hybrid, electrophoretic mobility shift assays, and luciferase activity assays suggested that SlWRKY75 directly activates the expression of GRETCHEN HAGEN 3.3 (SlGH3.3), which encodes an IAA-amido synthetase. SlGH3.3 enhanced tomato defense against Pst DC3000 by converting free IAA to the aspartic acid (Asp)-conjugated form IAA-Asp. In addition, SlWRKY75 interacted with a tomato valine-glutamine (VQ) motif-containing protein 16 (SlVQ16) in vivo and in vitro. SlVQ16 enhanced SlWRKY75-mediated transcriptional activation of SlGH3.3 and promoted tomato defense responses to Pst DC3000. Our findings illuminate a mechanism in which the SlVQ16-SlWRKY75 complex participates in tomato pathogen defense by positively regulating SlGH3.3-mediated auxin homeostasis.

Synthetic auxin’s effect on root hair growth and peroxisomes in Arabidopsis thaliana

Root hairs are long tubular outgrowths of plant’s root cells that increase water and solute uptake to nurture plants. Root hairs of Arabidopsis thaliana play an important role in studying how auxin affects plants. We investigated the effect of synthetic auxin, naphthalene acetic acid (NAA), on root hair length and peroxisome organelle movement in root hairs. We expected that increasing the concentrations of synthetic auxin in wild-type plants and mutants in class XI myosin, xik and xib would cause an increase in root hair length and linear movement of peroxisomes in the plants. Adding 0.1 µM of NAA to the plant’s growth medium resulted in significantly longer root hairs in wild-type and mutant plants compared to other concentrations tested (0 µM, 0.01 µM, and 1µM). Adding 1 µM of NAA to the plants did not produce significantly longer root hairs compared to 0 µM and 0.1 µM. These data suggest that an increase in auxin can help compensate for the observed impacts caused by the mutants, but that there might be a maximum capacity of auxin intake for a plant to receive optimal growth of root hairs. We found no significant trend for peroxisome movement with an increase of NAA in wild-type and mutant types for linear and wiggling velocity.

In vitro and in silico study for plant growth promotion potential of indigenous Ochrobactrum ciceri and Bacillus australimaris

Abstract Insights into plant and bacterial associations, along with their genome mining, have paved the way for the improvement of the agriculture sector. Initially, 69 morphologically different bacterial strains were isolated from 6 different extreme environment samples. For in vitro screening of plant growth-promoting bacteria, auxin, hydrogen cyanide, and antibiotic production along with phosphate solubilization potential was estimated. Only 15 strains exhibited noteworthy production of plant growth-promoting compounds. Ochrobactrum ciceri CS-10 fostered Triticum aestivum and Zea mays seedling root growth remarkably (104.12 and 159%, respectively), while Bacillus australimaris TP-10 significantly increased the number of leaves in T. aestivum (166.66%) and Z. mays (133.33%) seedlings. These strains also boosted seedling biochemical traits, like indole acetic acid, peroxidase, and soluble protein content. Particularly, O. ciceri elevated peroxidase content greatly in T. aestivum (249.7%) and Z. mays (260.5%). Scanning electron micrographs of inoculated roots revealed the aggregation of cells at the roots of Z. mays, whereas single cells/micro-colonies were observed on T. aestivum roots. For in silico analysis, AntiSMASH was used for genome mining of the environmental Ochrobactrum sp. and B. australimaris reference genome. This genome mining unveiled diverse gene clusters encoding; terpenes, beta-lactones, acyl-amino-acids, aryl polyenes, lanthipeptide, and siderophores, etc. Two common biosynthetic gene clusters (terpenes and beta-lactones) were identified in these strains, which can act as plant growth promoters. This symbiotic plant–bacteria relationship has promising ecological and economic implications, offering avenues for beneficial applications.

Development of a bacterial gene transcription activating strategy based on transcriptional activator positive feedback

IntroductionTranscription of biological nitrogen fixation (nif) genes is activated by the NifA protein which recognizes specific activating sequences upstream of σ54-dependent nif promoters. The large quantities of nitrogenase which can make up 20% of the total proteins in the cell indicates high transcription activating efficiency of NifA and high transcription level of nifHDK nitrogenase genes. ObjectivesDevelopment of an efficient gene transcription activating strategy in bacteria based on positive transcription regulatory proteins and their regulating DNA sequences. MethodsWe designed a highly efficient gene transcription activating strategy in which the nifA gene was placed directly downstream of its regulating sequences. The NifA protein binds its regulating sequences and stimulates transcription of itself and downstream genes. Overexpressed NifA causes transcription activation by positive reinforcement. ResultsWhen this gene transcription activating strategy was used to overexpress NifA in Pseudomonas stutzeri DSM4166 containing the nif gene cluster, the nitrogenase activity was increased by 368 folds which was 16 times higher than that obtained by nifA driven by the strongest endogenous constitutive promoter. When this strategy was used to activate transcription of exogenous biosynthetic genes for the plant auxin indole-3-acetic acid and the antitumor alkaloid pigment prodigiosin in DSM4166, both of them resulted in better performance than the strongest endogenous constitutive promoter and the highest reported productions in heterologous hosts to date. Finally, we demonstrated the universality of this strategy using the positive transcriptional regulator of the psp operon, PspF, in E. coli and the pathway-specific positive transcription regulator of the polyene antibiotic salinomycin biosynthesis, SlnR, in Streptomyces albus. ConclusionMany positive transcription regulatory proteins and their regulating DNA sequences have been identified in bacteria. The gene transcription activating strategy developed in this study will have broad applications in molecular biology and biotechnology.

Effectiveness of Bacillus pseudomycoides strain for Biocontrol of Early Blight on tomato plants

Alternaria early blight is an air-borne and soil-borne pathogen that cause losses and damages that can reach up to 80% in tomato production. In our work, the immediate antagonistic effect of Bacillus pseudomycoides was inspected against Alternaria early blight of tomato. Bacillus pseudomycoides (Bp1) (OQ629426) gave inhibition efficacy against A. solani growth, being, 74.22 %. Invitro, Bp1 had the capability to produce the endogenous plant auxin (IAA) it was 18.9 (µg/100 mL), the quantity of GA 9.4 (µg/100 mL), 95.8 μ Deferroxamine mesylate. Tomato plants treated with B. pseudomycoides registered the least disease severity, being 50 and 40 % in Mancozeb + ALS and Bp1+ ALS treatments with high efficiency to control the severity between 75 and 100 % respectively. Tomato plants treated with B. pseudomycoides showed improved growth characteristics as compared with the untreated control. Plants with bacterial treatment conferred 45.6 cm shoot length, 2.9 (g∕plant) fresh weight and 0.7 (g∕plant) Dry weight. The highest increase in the activity of polyphenol oxidase (PPO) and peroxidase (POD) was observed in the infected leaves of tomato plants treated with B. pseudomycoides Bp1 (T4) (4.6, 6.9 m/g f. w.) respectively, followed by treatment of plants with Mancozeb (T3) (3.9, 5.4 m/g f. w.) respectively, compared to other treatments. This study suggested that B. pseudomycoides is a promising biocontrol agent against Alternaria early blight. This bacterium may represent an important source of potential antimicrobial bio-agent against Alternaria early blight disease, also it may play a role in the development of integrated control programs in future studies.

Phytotoxicity alleviation of imazethapyr to non-target plant wheat: active regulation between auxin and DIMBOA.

Effectively controlling target organisms while reducing the adverse effects of pesticides on non-target organisms is a crucial scientific inquiry and challenge in pesticide ecotoxicology research. Here, we studied the alleviation of herbicide (R)-imazethapyr [(R)-IM] to non-target plant wheat by active regulation between auxin and secondary metabolite 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazine-3(4H)-one (DIMBOA). We found (R)-IM reduced 32.4% auxin content in wheat leaves and induced 40.7% DIMBOA accumulation compared to the control group, which effortlessly disrupted the balance between wheat growth and defense. Transcriptomic results indicated that restoration of the auxin level in plants promoted the up-regulation of growth-related genes and the accumulation of DIMBOA up-regulated the expression of defense-related genes. Auxin and DIMBOA alleviated herbicide stress primarily through effects in the two directions of wheat growth and defense, respectively. Additionally, as a common precursor of auxin and DIMBOA, indole adopted a combined growth and defense strategy in response to (R)-IM toxicity, i.e., restoring growth development and enhancing the defense system. Future regulation of auxin and DIMBOA levels in plants may be possible through appropriate methods, thus regulating the plant growth-defense balance under herbicide stress. Our insight into the interference mechanism of herbicides to the plant growth-defense system will facilitate the design of improved strategies for herbicide detoxification.

Pseudomonas hormoni sp. nov., a plant hormone producing bacterium isolated from Arctic grass, Ellesmere Island, Canada.

Bacterial strain G20-18T was previously isolated from the rhizosphere of an Arctic grass on Ellesmere Island, Canada and was characterized and described as Pseudomonas fluorescens. However, new polyphasic analyses coupled with phenotypic, phylogenetic and genomic analyses reported here demonstrate that the affiliation to the species P. fluorescens was incorrect. The strain is Gram-stain-negative, rod-shaped, aerobic and displays growth at 5-25 °C (optimum, 20-25 °C), at pH 5-9 (optimum, pH 6-7) and with 0-4 % NaCl (optimum, 2 % NaCl). The major fatty acids are C16 : 0 (35.6 %), C17 : 0 cyclo ω7c (26.3 %) and summed feature C18 : 1/C18 : 1 ω7c (13.6 %). The respiratory quinones were determined to be Q9 (93.5 %) and Q8 (6.5 %) and the major polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. Strain G20-18T was shown to synthesize cytokinin and auxin plant hormones and to produce 1-aminocyclopropane-1-carboxylate deaminase. The DNA G+C content was determined to be 59.1 mol%. Phylogenetic analysis based on the 16S rRNA gene and multilocus sequence analysis (concatenated 16S rRNA, gyrB, rpoB and rpoD sequences) showed that G20-18T was affiliated with the Pseudomonas mandelii subgroup within the genus Pseudomonas. Comparisons of the G20-18T genome sequence and related Pseudomonas type strain sequences showed an average nucleotide identity value of ≤93.6 % and a digital DNA-DNA hybridization value of less than 54.4 % relatedness. The phenotypic, phylogenetic and genomic data support the hypothesis that strain G20-18T represents a novel species of the genus Pseudomonas. As strain G20-18T produces or modifies hormones, the name Pseudomonas hormoni sp. nov. is proposed. The type strain is G20-18T (=LMG 33086T=NCIMB 15469T).