Indole-3-acetic Acid Synthesis Research Articles

The response of Petunia × atkinsiana 'Pegasus Special Burgundy Bicolor’ to mechanical stress encompassing morphological changes as well as physiological and molecular factors

In 1973, Jaffe identified and characterized the phenomenon of thigmomorphogenesis, also referred to as mechanical stress (MS) or mechanical stimulation in plants. Previous studies on petunia plants demonstrated that MS significantly affects growth dynamics. As a response to MS, petunias exhibit increased levels of indole-3-acetic acid (IAA) oxidase and peroxidase, although the active transport of endogenous IAA remains unaffected. Furthermore, earlier research has shown that MS inhibits the synthesis of IAA and gibberellin (GA3), with noticeable effects on the 14th day of mechanical stimulation. The current experiment made on Petunia × atkinsiana 'Pegasus Special Burgundy Bicolor’ focused on evaluating the morphological and physiological responses to MS, along with the expression of specific touch-responsive genes such as GH3.1, which is involved in auxin metabolism, and calmodulins (CaMs), playing an important role in stress responses. GH3.1 expression was found to be negatively correlated with IAA synthesis while positively correlated with GAs synthesis and IAA oxidase activity. Variable expression patterns were observed in the calmodulins: CAM53 and CAM81 expression positively correlated with IAA synthesis and plant height, whereas CAM72 expression was positively associated with GAs levels and IAA oxidase activity in plants touched 80× per day, but all of them were negatively related to IAA content and shoot increment, while positively related to GAs synthesis and IAA oxidase activity.

Exploring IAA biosynthesis and plant growth promotion mechanism for tomato root endophytes with incomplete IAA synthesis pathways

Exploring indoleacetic acid (IAA) biosynthesis pathways of plant growth promoting bacteria and their ability to synthesize IAA is crucial for understanding the promotion mechanism and for developing more efficient microbial fertilizer. In this study, 118 bacterial endophytic strains were isolated from tomato root and 68 isolates were identified as members of Bacillus and Pseudomonas genus. After screening abilities to synthesize IAA in vitro and promote plant growth for these identified Bacillus and Pseudomonas strains, 7 endophytic strains Bacillus sp. Y_21, B. paramycoides Y_29, B. albus Y_96, B. cereus Y_121, P. plecoglossicida Y_157, Bacillus sp. Y_165 and B. aryabhattai Y_170 strains showed a significant promotion role on wheat root or leaf, including 4 endophytic strains with the potential ability to utilize intermediate metabolites, such as tryptamine and indole acetamide, to produce IAA. Genomic sequencing analysis for selected representative plant growth promoting endophytes showed that IAA-producing bacteria B. cereus mr31 and P. putida Y_166 separately harbored a complete indoleacetamide (IAM) and complete tryptamine (TAM) pathway; whereas, Bacillus sp. Y_165 and B. aryabhattai Y_170, two strains producing IAA not using tryptophan but with indole-3-acetamide, had an incomplete IAM pathway. Fermentation experiments of three genome-sequenced strains using wheat or tomato root extracts as substrate, and combining with UHPLC–MS/MS analysis for wheat root extracts, demonstrated that Bacillus sp. Y_165 strain might produce IAA by using the plant-derived indole-3-acetamide. Our study first demonstrated a novel potential mechanism for the plant growth promoting endophytes to biosynthesize IAA using plant-derived intermediates. This additional mechanism has deepened our understanding of how bacterial endophytes promote plant health and resilience, offering valuable insights about how plants regulate IAA homeostasis within their internal tissues in association with bacterial endophytes.Graphical

Synthesis and Degradation of the Phytohormone Indole-3-Acetic Acid by the Versatile Bacterium Paraburkholderia xenovorans LB400 and Its Growth Promotion of Nicotiana tabacum Plant.

Plant growth-promoting bacteria (PGPB) play a role in stimulating plant growth through mechanisms such as the synthesis of the phytohormone indole-3-acetic acid (IAA). The aims of this study were the characterization of IAA synthesis and degradation by the model aromatic-degrading bacterium Paraburkholderia xenovorans LB400, and its growth promotion of the Nicotiana tabacum plant. Strain LB400 was able to synthesize IAA (measured by HPLC) during growth in the presence of tryptophan and at least one additional carbon source; synthesis of anthranilic acid was also observed. RT-PCR analysis indicates that under these conditions, strain LB400 expressed the ipdC gene, which encodes indole-3-pyruvate decarboxylase, suggesting that IAA biosynthesis proceeds through the indole-3-pyruvate pathway. In addition, strain LB400 degraded IAA and grew on IAA as a sole carbon and energy source. Strain LB400 expressed the iacC and catA genes, which encode the α subunit of the aromatic-ring-hydroxylating dioxygenase in the IAA catabolic pathway and the catechol 1,2-dioxygenase, respectively, which may suggest a peripheral IAA pathway leading to the central catechol pathway. Notably, P. xenovorans LB400 promoted the growth of tobacco seedlings, increasing the number and the length of the roots. In conclusion, this study indicates that the versatile bacterium P. xenovorans LB400 is a PGPB.

Extract from endophytic Fusarium isolates stimulates seed germination of the host and protocorm development of non-host orchids

ABSTRACT We isolated endophytic Fusarium strains from the healthy roots, stems, and leaves of Dendrobium moschatum to investigate their plant growth-promoting activities in vitro. Subsequently, Indole acetic acid (IAA) was quantified and the IaaM gene (responsible for IAA synthesis in fungi) was amplified and sequenced. Finally, a germination assay was performed with seeds of D. moschatum and a plant growth assay with protocorms of Dendrobium longicornu to test their plant growth-promoting activities. Five Fusarium isolates (CDS11, PDL1, PDL3, PDR6, PDR7) were identified in this study. The highest amount (60µgml−1) of indole acetic acid was recorded in the PDR7 extract, whereas it was not detected in PDR6 and CDS11. The fungal extracts of isolates PDR6 and PDR7 were highly effective for seed germination by approximately 80% and 90% (respectively) of the host plant. The fungal extract of PDR7 showed a high IAA content and promoted in vitro seed germination of the host (D. moschatum) and protocorm development of the non-host (D. longicornu). In contrast, IAA content in the fungal extract of PDR6 remained undetected but was effective in both seed germination and protocorm development. Our results demonstrated the potential beneficial application of endophytic Fusarium in orchid mass propagation.

Prevalent Plant Growth Hormone Indole-3-acetic Acid Produced by Streptomyces sp. VSMKU1027 and its Potential Antifungal Activity against Phytofungal Pathogens

Microorganisms and plants can produce indole-3-acetic acid (IAA) by mechanisms that either involve tryptophan or do not involve tryptophan. The control of Zone of inhibition (ZOI) ranged from 1.2 cm to 1.0 cm. A promising antagonistic isolate, Streptomyces sp. VSMKU1027, exhibited robust antagonistic activity against two significant soil-borne phytopathogenic fungi, namely Rhizoctonia solani and Fusarium oxysporum, outperforming the control. The morphology of both R. solani and F. oxysporum, including their sclerotium and spores, became condensed and indistinct, and mycelial disintegration was observed due to the action of VSMKU1027, in contrast to the control. The isolate significantly produced antimicrobial traits and hydrolytic enzymes except hydrogen cyanide and cellulase. Furthermore, the promising isolate VSMKU1027 was identified as Streptomyces sp. based on its morphological, physiological, and biochemical characteristics. In comparison to the control, the isolate VSMKU1027 demonstrated increased synthesis of IAA and the hydrolytic enzyme protease with the corresponding substrates. The production of IAA was optimized on the sixth day, at 35°C and pH 6.5. The highest generation of IAA was recorded, with an ISP2 and 0.4% concentration of L-tryptophan.

Physiological and transcriptomic responses of microalgal-bacterial co-culture reveal nutrient removal and lipid production during biogas slurry treatment

Microalgal-bacterial consortia can treat biogas slurry and produce high-value products. This study found that co-cultures of Desmodesmus sp. and Bacillus megaterium improved nutrient removal, biomass production, and lipid accumulation in Desmodesmus sp. Dual transcriptomic analyses revealed that B. megaterium upregulated genes associated with glycolysis, the Calvin cycle, tricarboxylic acid cycle, indole acetic acid synthesis, and fatty acid biosynthesis in Desmodesmus sp. Under a high C/N ratio, key genes involved in fatty acid degradation were downregulated, promoting lipid accumulation in co-cultured Desmodesmus sp. Effective NH4+-N removal in the co-culture under a high C/N ratio was attributed to microbial interactions. Desmodesmus sp. downregulated the URE gene in bacteria, inhibiting urea hydrolysis, while B. megaterium upregulated the URE and gdhA genes in microalgae, promoting urea utilization and NH4+-N assimilation. This study provides new insights into the transcriptional regulation in nutrient assimilation and lipid metabolism in microalgal-bacterial consortia.

IAA Synthesis Pathway of Fitibacillus barbaricus WL35 and Its Regulatory Gene Expression Levels in Potato (Solanum tuberosum L.).

Indole-3-acetic acid (IAA), as an important regulator of potato growth, seriously affects the growth and yield of potato. Although many studies have reported that IAA-producing Bacillus can promote plant growth, little research has been conducted on its synthesis pathway and molecular mechanisms. In this study, an IAA-producing strain WL35 was identified as Fitibacillus barbaricus, and its yield was 48.79 mg·L-1. The results of the pot experiments showed that WL35 significantly increased plant height, stem thickness, chlorophyll content, and number of leaves of potato plants by 31.68%, 30.03%, 32.93%, and 36.59%, respectively. In addition, in the field experiments, WL35-treated plants increased commercial potato yield by 16.45%, vitamin C content by 16.35%, protein content by 75%, starch content by 6.60%, and the nitrogen, phosphorus, and potassium accumulation by 9.98%, 12.70%, and 26.76%, respectively. Meanwhile, the synthetic pathway of WL35 was found to be dominated by the tryptophan-dependent pathway, the IAM, TAM, and IPA pathways worked together, and the pathways that played a role at different times were different. Furthermore, RNA-seq analysis showed that there were a total of 2875 DEGs regulated in the samples treated with WL35 seed dressing compared with the CK, of which 1458 genes were up-regulated and 1417 genes were down-regulated. Potato roots express differential genes enriched in processes such as carbohydrate metabolism processes and cellular polysaccharide metabolism, which regulate potato plant growth and development. The above results provide a theoretical basis for the further exploration of the synthesis pathway of IAA and its growth-promoting mechanism in potato.

The involvement of phytohormones in plant–pathogen interaction

Plant–pathogen interactions involve intricate signaling networks that coordinate the plant immune response. Recognition of pathogens through pattern recognition receptors (PRRs) triggers activation of mitogen-activated protein kinase (MAPK) pathways, initiating a cascade of defense mechanisms. Central to these responses is the synthesis of phytohormones such as salicylic acid (SA), auxins–indole-3-acetic acid (IAA), and gibberellins–gibberellic acid (GA), pivotal for immune activation. This review explores the multifaceted roles of these phytohormones in plant immunity, drawing on recent findings from Arabidopsis thaliana and Gossypium hirsutum studies. The review discusses MAPK-mediated activation of TGA1/4 (TGACG sequence-specific binding protein 1/4) transcription factors enhancing SA biosynthesis via isochorismate synthase (ICS). Increased SA levels activate NPR1, promoting gene expression in immune-related pathways including systemic acquired resistance (SAR). Concurrently, pathogen-induced IAA synthesis activates auxin-responsive genes crucial for immune responses. Elevated biosynthesis of IAA from L-tryptophan activates these genes by degrading repressor molecules. IAA acts antagonistically to SA, conserving energy during pathogen infection. Additionally, GA is vital for plant growth and development, operating DELLA (Asp–Glu–Leu–Leu–Ala) protein degradation with the formation of a complex with gibberellin insensitive dwarf 1 (GID1). Once DELLA prevents releasing GA-related response reactions, it is extremelly crucial for GA actions. In general, the review explores the intricate interplay between SA, IAA, and GA, highlighting SA's antagonistic regulation of GA signaling and the synergistic effects of auxin and GA. Understanding these hormone–mediated pathways is crucial for elucidating precise mechanisms underlying plant immunity. Insights gained could inform strategies to enhance plant resistance against pathogens, contributing to sustainable agriculture and global food security efforts.

Elimination of ineffective inorganic salt component in medium for indole‐3‐acetic acid synthesis by Serratia plymuthica UBCF_13 and its effect on the growth of chili seedlings

Indole‐3‐acetic acid (IAA) is an essential phytohormone that controls a variety of plant growth mechanisms. Bacteria can produce IAA to stimulate plant growth, with its production influenced by the culture conditions. Serratia plymuthica UBCF_13 is recognized as an IAA‐producing bacterium, exhibiting maximum IAA production in a yeast medium comprising yeast extract, sucrose, K2HPO4, MgSO4, NaCl, and CaCO3. However, prior studies optimizing individual inorganic salt components indicated minimal impact on IAA synthesis within this medium. This study aimed to eliminate the unnecessary inorganic salt components and the medium was then applied to investigate the IAA biosynthesis pathway and the plant growth‐promoting assay. The elimination assay consisted of yeast sucrose medium devoid of K2HPO4, MgSO4, NaCl, or CaCO3, and yeast sucrose medium containing only MgSO4 and CaCO3. Various indole compounds were then added to the revised medium composition to investigate the IAA biosynthesis pathway of UBCF_13 using high‐performance liquid chromatography (HPLC). Furthermore, the effect of UBCF_13 culture supernatant, cultivated in the new medium, on chili plant growth was evaluated. The highest IAA production (138.8 µg/mL) was observed in the yeast sucrose with CaCO3 and MgSO4 (elimination of K2HPO4 and NaCl). The presence of indole‐3‐acetamide (IAM) compound from the medium extracts, supplemented with multiple indole compounds, revealed that UBCF_13 may use the IAM pathway. The application of UBCF_13 supernatant enhanced the shoot, root length, fresh weight, and germination time of chili seeds by 37.7%, 49.3%, 204.3%, and 38.6%, respectively. This study demonstrated that eliminating K2HPO4 and NaCl provided a new culture medium composition conducive to IAA production by UBCF_13. Moreover, the UBCF_13 extract has the potential to promote plant growth.

Characterization of endophytic bacteria isolated from wild rice plants in the Mekong Delta, Vietnam

Abstract. Thi QVC, Minh NLK, Thuy NP, Tat TQ, Tran T. 2024. Characterization of endophytic bacteria isolated from wild rice plants in the Mekong Delta, Vietnam. Biodiversitas 25: 2576-2585. Endophytic bacteria bring many benefits to plants, such as stimulating plant growth and inhibiting many microbial pathogens that cause plant diseases. Hence, this investigation aimed to evaluate the association of endophytic bacteria with wild rice (Oryza rufipogon) that can fix nitrogen, solubilize phosphorus and produce indole-3-acetic acid (IAA). Twelve-five bacterial strains were recovered from wild rice stems and roots collected from Vinh Long and Tien Giang provinces of the Mekong Delta. Among these strains, six had phosphorus solubilizing and seven had nitrogen-fixing activity. Strain BR3.5 fixed the highest nitrogen, i.e. ammonia (NH4+) content of 0.109 ± 0.002 mg/L after eight-day incubation. However, the highest phosphorus solubilization was recorded in two isolates, RR3.7 and RR1.1, with clear zone diameters of 0.800 ± 0.020 mm and 0.800 ± 0.030 mm, respectively. In addition, bacterial strains could synthesize IAA, and BR2.5 produced the highest, i.e., 0.067 ± 0.002 ?g/mL, IAA after eight-day incubation. Notably, strain BR3.5 exhibited multiple activities like nitrogen fixation (0.109 ± 0.002 mg/L), phosphorus solubilization (1.02 ± 0.002 mm), and IAA synthesis (0.056 ± 0.00 ?g/mL). Strain BR3.5 was identified as Pantoea sp. based on 16S rRNA gene sequencing (92.69% similarity) together with morpho-physiological and biochemical characteristics. The findings indicate that strain BR3.5 may be used for the production of biofertilizers for rice farming.

A Small Auxin-Up RNA Gene, IbSAUR36, Regulates Adventitious Root Development in Transgenic Sweet Potato.

Small auxin-upregulated RNAs (SAURs), as the largest family of early auxin-responsive genes, play important roles in plant growth and development processes, such as auxin signaling and transport, hypocotyl development, and tolerance to environmental stresses. However, the functions of few SAUR genes are known in the root development of sweet potatoes. In this study, an IbSAUR36 gene was cloned and functionally analyzed. The IbSAUR36 protein was localized to the nucleus and plasma membrane. The transcriptional level of this gene was significantly higher in the pencil root and leaf.This gene was strongly induced by indole-3-acetic acid (IAA), but it was downregulated under methyl-jasmonate(MeJA) treatment. The promoter of IbSAUR36 contained the core cis-elements for phytohormone responsiveness. Promoter β-glucuronidase (GUS) analysis in Arabidopsis showed that IbSAUR36 is highly expressed in the young tissues of plants, such as young leaves, roots, and buds. IbSAUR36-overexpressing sweet potato roots were obtained by an efficient Agrobacterium rhizogenes-mediated root transgenic system. We demonstrated that overexpression of IbSAUR36 promoted the accumulation of IAA, upregulated the genes encoding IAA synthesis and its signaling pathways, and downregulated the genes encoding lignin synthesis and JA signaling pathways. Taken together, these results show that IbSAUR36 plays an important role in adventitious root (AR) development by regulating IAA signaling, lignin synthesis, and JA signaling pathways in transgenic sweet potatoes.

Screening and Optimization of IAA Production by PGPR isolated from Rhizosphere of a Pterocarpus marsupium Roxb. and their Effect on Plant Growth

Indole Acetic Acid (IAA) production is important attribute of PGPR that promote plant growth and development. The rhizosphere is hotspot in the soil that harbors PGPR. The present study was aimed with isolation and screening of IAA producing bacteria from the rhizosphere of Pterocarpus marsupium Roxb. Optimum culture conditions (pH, temperature, incubation period and L-tryptophan concentration for IAA production were studied for selected isolates and their effect on wheat growth and root development was evaluated. Among twenty four IAA producing isolates five isolates (Et1, Rp1, Rp5, Rp6, and Rp9) produced maximum IAA in range of 50-70 μg/mL and was used in optimization studies. Maximum IAA was produced in 96 hours of incubation, at pH 7 and with 0.1mg/mL of L-tryptophan by all five isolates. 30oC is the most suitable temperature for Et1, Rp1, Rp5, Rp9; whereas Rp6 produced nearly same amount of IAA at wide range of temperature 30-35oC (77-84.12 μg/mL) and at pH 7-8 ( 73-74μg/mL). Out of the five isolates, Rp6 exhibits the highest potential, having a maximum IAA of 84.12 μg/mL at 35°C and pH 7. Although tryptophan influences IAA synthesis but at higher concentration of tryptophan inhibits IAA synthesis. To validate the production of IAA, crude extracts were analyzed using thin layer chromatography (TLC). A spot of standard IAA with the same Rf value (0.91) was found to match a specific spot from the crude IAA.

Effects of Environmental Stresses on Synthesis of 2-Phenylethanol and IAA by Enterobacter sp. CGMCC 5087.

2-Phenylethanol (2-PE) and indole-3-acetic acid (IAA) are important secondary metabolites produced by microorganisms, and their production are closely linked to the growth state of microorganisms and environmental factors. Enterobacter CGMCC 5087 can produce both 2-PE and IAA depending on α-ketoacid decarboxylase KDC4427. This study aimed to investigate the effects of different environment factors including osmotic pressure, temperature, and pH on the synthesis of 2-PE and IAA in Enterobacter sp. CGMCC 5087. The bacteria exhibited an enhanced capacity for 2-PE synthesis while not affecting IAA synthesis under 5% NaCl and pH 4.5 stress conditions. In an environment with pH 9.5, the synthesis capacity of 2-PE remained unchanged while the synthesis capacity of IAA decreased. The synthesis ability of 2-PE was enhanced with an increase in temperature within the range of 25 °C to 37 °C, while the synthesis capacity of IAA was not affected significantly. Additionally, the expression of KDC4427 varied under stress conditions. Under 5% NaCl stress and decreased temperature, expression of the KDC4427 gene was increased. However, altering pH did not result in significant differences in gene expression levels, while elevated temperature caused a decrease in gene expression. Furthermore, molecular docking and molecular dynamics simulations suggested that these conditions may induce fluctuation in the geometry shape of binding cavity, binding energy, and especially the dαC-C- value, which played key roles in affecting the enzyme activity. These results provide insights and strategies for the synthesis of metabolic products 2-PE and IAA in bacterial fermentation, even under unfavorable conditions.

Transcriptome Sequencing Reveals the Mechanism of Auxin Regulation during Root Expansion in Carrot.

Carrot is an important vegetable with roots as the edible organ. A complex regulatory network controls root growth, in which auxin is one of the key players. To clarify the molecular mechanism on auxin regulating carrot root expansion, the growth process and the indole-3-acetic acid (IAA) content in the roots were measured in this experiment. It was found that the rapid expansion period of the root was from 34 to 41 days after sowing and the IAA content was the highest during this period. The root growth then slowed down and the IAA levels decreased. Using the transcriptome sequencing database, we analyzed the expression of IAA-metabolism-related genes and found that the expression of most of the IAA synthesis genes, catabolism genes, and genes related to signal transduction was consistent with the changes in IAA content during root expansion. Among them, a total of 31 differentially expressed genes (DEGs) were identified, including 10 IAA synthesis genes, 8 degradation genes, and 13 genes related to signal transduction. Analysis of the correlations between the DEGs and IAA levels showed that the following genes were closely related to root development: three synthesis genes, YUCCA10 (DCAR_012429), TAR2 (DCAR_026162), and AMI1 (DCAR_003244); two degradation genes, LPD1 (DCAR_023341) and AACT1 (DCAR_010070); and five genes related to signal transduction, IAA22 (DCAR_012516), IAA13 (DCAR_012591), IAA27 (DCAR_023070), IAA14 (DCAR_027269), and IAA7 (DCAR_030713). These results provide a reference for future studies on the mechanism of root expansion in carrots.

Physiology and transcriptome of Sapindus mukorossi seeds at different germination stages

Sapindus mukorossi has a wide distribution range, high application value, and broad developmental potential. Previous studies have mostly focused on the medicinal and economic value of soapberry; however, few studies have been conducted on its seed germination. This study measured the physiological indicators and hormone content of soapberry seeds at different germination stages and preliminarily determined that abscisic acid (ABA) and indole-3-acetic acid (IAA) are the key hormones that affect the germination of soapberry seeds. Both Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG enrichment) analyses detected hormone transduction pathways, further confirming the key role of plant hormones in the germination process of soapberry seeds. Through transcriptome analysis, we speculated that CYP707A and IPA are key genes in the ABA and IAA synthesis pathways, respectively. This study revealed the close relationship between plant hormones and soapberry seed germination and provided new ideas for further exploration of the germination mechanism of soapberry seeds.

Analysis of the regulatory mechanism of exogenous IAA-mediated tryptophan accumulation and synthesis of endogenous IAA in Chlorococcum humicola

The activated sludge method is widely used for the treatment of phenol-containing wastewater, which gives rise to the problem of toxic residual sludge accumulation. Indole-3-acetic acid (IAA), a typical phytohormone, facilitates the microalgal resistance to toxic inhibition while promoting biomass accumulation. In this study, Chlorococcum humicola (C. humicola) was cultured in toxic sludge extract and different concentrations of IAA were used to regulate its physiological properties and enrichment of high value-added products. Ultimately, proteomics analysis was used to reveal the response mechanism of C. humicola to exogenous IAA. The results showed that the IAA concentration of 5 × 10−6 mol/L (M) was most beneficial for C. humicola to cope with the toxic stress in the sludge extract medium, to promote the activity of rubisco enzyme, to enhance the efficiency of photosynthesis, and, finally, to accumulate protein as a percentage of specific dry weight 1.57 times more than that of the control group. Exogenous IAA altered the relative abundance of various amino acids in C. humicola cells, and proteomic analyses showed that exogenous IAA stimulated the algal cells to produce more indole-3-glycerol phosphate (IGP), indole, and serine by up-regulating the enzymes. These precursors are converted to tryptophan under the regulation of tryptophan synthase (A0A383V983), and tryptophan can be metabolized to endogenous IAA to promote the growth of C. humicola. These findings have important implications for the treatment of toxic residual sludge while enriching for high-value amino acids.

The Complete Genome Sequence of Bacillus toyonensis Cbmb3 with Polyvinyl Chloride-Degrading Properties.

The accumulation of high amounts of plastic waste in the environment has raised ecological and health concerns, particularly in croplands, and biological degradation presents a promising approach for the sustainable treatment of this issue. In this study, a polyvinyl chloride (PVC)-degrading bacterium was isolated from farmland soil samples attached to waste plastic, utilizing PVC as the sole carbon source. The circular chromosome of the strain Cbmb3, with a length of 5,768,926 bp, was subsequently sequenced. The average GC content was determined to be 35.45%, and a total of 5835 open reading frames were identified. The strain Cbmb3 was designated as Bacillus toyonensis based on phylogenomic analyses and genomic characteristics. The bioinformatic analysis of the Cbmb3 genome revealed putative genes encoding essential enzymes involved in PVC degradation. Additionally, the potential genomic characteristics associated with phytoprobiotic effects, such as the synthesis of indole acetic acid and secondary metabolite synthesis, were also revealed. Overall, the present study provides the first complete genome of Bacillus toyonensis with PVC-degrading properties, suggesting that Cbmb3 is a potential strain for PVC bioremediation and application.

Thriving against the odds: Exploring halotolerant rhizobacteria in the saline rhizosphere of Tuzla lagoon's halophytes

Soil salinization poses a significant threat to global crop production, affecting around 20% of agricultural fields with the challenges of osmotic and ionic stress. The reclamation of salinity-affected agricultural lands is a pressing concern. To bridge existing gaps in our understanding of halotolerant plant growth-promoting rhizobacteria (PGPR), this research strategically focuses on isolating and characterizing these beneficial bacteria from the rhizosphere of halophytes in the Tuzla lagoon area. The objective is to contribute essential insights, fostering a deeper understanding of halotolerant PGPR for application in sustainable agricultural practices, particularly in alleviating salinity-induced stress in plants.All nine isolates demonstrated remarkable abilities, including the synthesis of siderophores, with isolates B15, C20, E2, and H9 showcasing phosphate solubilization. Additionally, isolates E2 and H9 displayed phytase production, and five isolates exhibited indole acetic acid synthesis. Although 1-aminocyclopropane-1-carboxylate deaminase production was absent, hydrogen cyanide synthesis was evident in all isolates except H9. Isolate E2 did not demonstrate cellulase synthesis, but biofilm formation was observed in all isolates except C23.To assess the salinity stress mitigation potential of the isolates, a randomized complete block design bioassay was conducted with ten treatments (nine bacterial isolates and a control) across four salt concentrations (0 mM, 100 mM, 200 mM, and 300 mM). While the isolates successfully demonstrated multiple plant growth-promoting traits, their capacity to significantly alleviate the effects of salinity stress on wheat plants suggests the need for further exploration. Comprehensive greenhouse/field trials under diverse physiological and environmental conditions are recommended to unlock the full potential of these isolates in effectively mitigating salinity stress in crops.

Bacterial indole-3-acetic acid: A key regulator for plant growth, plant-microbe interactions, and agricultural adaptive resilience

Indole-3-acetic acid (IAA), a fundamental phytohormone categorized under auxins, not only influences plant growth and development but also plays a critical role in plant-microbe interactions. This study reviews the role of IAA in bacteria-plant communication, with a focus on its biosynthesis, regulation, and the subsequent effects on host plants. Bacteria synthesize IAA through multiple pathways, which include the indole-3-acetamide (IAM), indole-3-pyruvic acid (IPyA), and several other routes, whose full mechanisms remain to be fully elucidated. The production of bacterial IAA affects root architecture, nutrient uptake, and resistance to various abiotic stresses such as drought, salinity, and heavy metal toxicity, enhancing plant resilience and thus offering promising routes to sustainable agriculture. Bacterial IAA synthesis is regulated through complex gene networks responsive to environmental cues, impacting plant hormonal balances and symbiotic relationships. Pathogenic bacteria have adapted mechanisms to manipulate the host’s IAA dynamics, influencing disease outcomes. On the other hand, beneficial bacteria utilize IAA to promote plant growth and mitigate abiotic stresses, thereby enhancing nutrient use efficiency and reducing dependency on chemical fertilizers. Advancements in analytical methods, such as liquid chromatography–tandem mass spectrometry, have improved the quantification of bacterial IAA, enabling accurate measurement and analysis. Future research focusing on molecular interactions between IAA-producing bacteria and host plants could facilitate the development of biotechnological applications that integrate beneficial bacteria to improve crop performance, which is essential for addressing the challenges posed by climate change and ensuring global food security. This integration of bacterial IAA producers into agricultural practice promises to revolutionize crop management strategies by enhancing growth, fostering resilience, and reducing environmental impact.

Investigating the biosynthesis and roles of the auxin phenylacetic acid during Pseudomonas syringae-Arabidopsis thaliana pathogenesis.

Several plant-associated microbes synthesize the auxinic plant growth regulator phenylacetic acid (PAA) in culture; however, the role of PAA in plant-pathogen interactions is not well understood. In this study, we investigated the role of PAA during interactions between the phytopathogenic bacterium Pseudomonas syringae strain PtoDC3000 (PtoDC3000) and the model plant host, Arabidopsis thaliana. Previous work demonstrated that indole-3-acetaldehyde dehydrogenase A (AldA) of PtoDC3000 converts indole-3-acetaldehyde (IAAld) to the auxin indole-3-acetic acid (IAA). Here, we further demonstrated the biochemical versatility of AldA by conducting substrate screening and steady-state kinetic analyses, and showed that AldA can use both IAAld and phenylacetaldehyde as substrates to produce IAA and PAA, respectively. Quantification of auxin in infected plant tissue showed that AldA-dependent synthesis of either IAA or PAA by PtoDC3000 does not contribute significantly to the increase in auxin levels in infected A. thaliana leaves. Using available arogenate dehydratase (adt) mutant lines of A. thaliana compromised for PAA synthesis, we observed that a reduction in PAA-Asp and PAA-Glu is correlated with elevated levels of IAA and increased susceptibility. These results provide evidence that PAA/IAA homeostasis in A. thaliana influences the outcome of plant-microbial interactions.