Indole-3-acetic Acid Synthesis Research Articles

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.

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.

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.

NIT24 and NIT29-mediated IAA synthesis of Xanthomonas oryzae pv. oryzicola suppresses immunity and boosts growth in rice.

Auxin plays a pivotal role in the co-evolution of plants and microorganisms. Xanthomonas oryzae pv. oryzicola (Xoc) stands as a significant factor that affects rice yield and quality. However, the current understanding of Xoc's capability for indole 3-acetic acid (IAA) synthesis and its mechanistic implications remains elusive. In this study, we performed a comprehensive genomic analysis of Xoc strain RS105, leading to the identification of two nitrilase enzyme family (NIT) genes, designated as AKO15524.1 and AKO15829.1, subsequently named NIT24 and NIT29, respectively. Our investigation unveiled that the deletion of NIT24 and NIT29 resulted in a notable reduction in IAA synthesis capacity within RS105, thereby impacting extracellular polysaccharide production. This deficiency was partially ameliorated through exogenous IAA supplementation. The study further substantiated that NIT24 and NIT29 have nitrilase activity and the ability to catalyse IAA production invitro. The lesion length and bacterial population statistics experiments confirmed that NIT24 and NIT29 positively regulated the pathogenicity of RS105, suggesting that NIT24 and NIT29 may regulate Xoc invasion by affecting IAA synthesis. Furthermore, our analysis corroborated mutant strains, RS105_ΔNIT24 and RS105_ΔNIT29, which elicited the outbreak of reactive oxygen species, the deposition of callose and the upregulation of defence-related gene expression in rice. IAA exerted a significant dampening effect on the immune responses incited by these mutant strains in rice. In addition, the absence of NIT24 and NIT29 affected the growth-promoting effect of Xoc on rice. This implies that Xoc may promote rice growth by secreting IAA, thus providing a more suitable microenvironment for its own colonization. In summary, our study provides compelling evidence for the existence of a nitrilase-dependent IAA biosynthesis pathway in Xoc. IAA synthesis-related genes promote Xoc colonization by inhibiting rice immune defence response and affecting rice growth by increasing IAA content in Xoc.

Characterization of Pseudomonas sp. En3, an Endophytic Bacterium from Poplar Leaf Endosphere with Plant Growth-Promoting Properties

Growth-promoting endophytic bacteria possess substantial potential for sustainable agriculture. Here, we isolated an endophytic bacterium, Pseudomonas sp. En3, from the leaf endosphere of Populus tomentosa and demonstrated its significant growth-promoting effects on both poplar and tomato seedlings. The phosphorus solubilization and nitrogen fixation abilities of strain En3 were confirmed via growth experiments on NBRIP and Ashby media, respectively. Salkowski staining and HPLC-MS/MS confirmed that En3 generated indole-3-acetic acid (IAA). The infiltration of En3 into leaf tissues of multiple plants did not induce discernible disease symptoms, and a successful replication of En3 was observed in both poplar and tobacco leaves. Combining Illumina and Nanopore sequencing data, we elucidated that En3 possesses a circular chromosome of 5.35 Mb, exhibiting an average G + C content of 60.45%. The multi-locus sequence analysis (MLSA) and genome average nucleotide identity (ANI) supported that En3 is a novel species of Pseudomonas and constitutes a distinct phylogenetic branch with P. rhizosphaerae and P. coleopterorum. En3 genome annotation analysis revealed the presence of genes associated with nitrogen fixation, phosphate solubilization, sulfur metabolism, siderophore biosynthesis, synthesis of IAA, and ethylene and salicylic acid modulation. The findings suggest that Pseudomonas sp. En3 exhibits significant potential as a biofertilizer for crop and tree cultivation.

Exogenous IAA enhances low potassium tolerance of sweetpotato by regulating root response strategy

ABSTRACT Plant roots are sensitive to potassium (K+) deficiency signals. Therefore, regulating root growth by exogenous methods is a vital strategy to improve low K+ tolerance of sweetpotato. We studied the effects of exogenous indole-3-acetic acid (IAA) on growth, K+ absorption, and root characteristics in sweetpotato exposed to low K+ treatment (LK). LK significantly inhibited dry mass, K+ concentration and accumulation, as well as the root elongation (length) and branching (forks and crossings) in sweetpotato seedlings. However, exogenous IAA increased the length, ratio, and density of lateral roots and promoted absorption and accumulation of K+, which effectively alleviated the inhibitory effect of low K+. Exogenous IAA also increased the expression levels of auxin synthesis (IbYUC6 and IbTAR2) and transport (IbPIN1, IbPIN3, and IbPIN8) genes in leaves and roots, which promoted the increase of endogenous IAA content. Furthermore, exogenous IAA was more effective on low-K-tolerant variety (XS32) than low-K-sensitive variety (NZ1) under LK stress, depending on their different IAA synthesis and transport strategies. These results indicated that exogenous IAA enhanced root responsiveness of sweetpotato to low K+ stress by modulating auxin biosynthesis and transport, thereby improving the tolerance of sweetpotato to low K+ stress.

STUDY OF THE ABILITY OF RHIZOSPHERE MICROORGANISMS TO PRODUCE IAA AND THEIR INFLUENCE ON PLANT GROWTH

A primary screening was conducted to assess the ability of rhizosphere microorganisms from cultivated and wild plants of arid ecosystems in the Astrakhan region to produce indoleacetic acid (IAA) and exhibit phytotoxic properties. The amount of synthesised IAA was determined using a photometric method, and the phytotoxicity of microbial culture liquid was evaluated on seeds of red round radish Raphanus sativus L. convar. radicula. It was found that all isolates had the ability for tryptophan-induced IAA synthesis. Out of the 50 examined isolates, 19 synthesised IAA at levels comparable to industrial producers 80 µg/ml and higher. The evaluation of the influence of microbial culture liquid on the growth and development of radish seeds revealed complete inhibition of the root system and seedling effect for all isolates. Among the examined isolates, 16 completely suppressed the growth of test plant seeds. Seed germination using the suspension of other isolates ranged from 7.1% to 63.3%. The experiment established that phytotoxic effects also increased with an increase in the amount of IAA synthesised by isolates. The influence of exogenous auxin on plant development can have positive and negative effects. The optimal concentration range of IAA for a specific plant can be extremely narrow, and any deviation from this concentration can lead to inhibitory effects. Therefore, further research is needed to explore the biotechnological potential of isolated strains with increased IAA production as industrial producers of this substance or as the basis for a biological preparation for plant growth stimulation.

Draft genome sequence of a halotolerant plant growth-promoting bacterium Pseudarthrobacter oxydans NCCP-2145 isolated from rhizospheric soil of mangrove plant Avicennia marina

BackgroundLimited knowledge exists regarding the diversity of mangrove plant-associated Pseudarthrobacter species. This study presents the first draft genome and phylogenetic analysis of a Pseudarthrobacter oxydans NCCP-2145, isolated from the rhizospheric soil of Aviciana marina, a native mangrove plant found in Miani Hor, Lasbela-Baluchistan, Pakistan. ResultsThe genome of P. oxydans NCCP-2145 comprises 4,495,869 base pairs, with a G+C content of 65.9% and 4,207 coding sequences. Genome annotation revealed the presence of multiple biosynthesis pathways. The analysis also identified genes responsible for plant growth-promoting traits, such as the synthesis of indole acetic acid, nitrogen fixation, and phosphorus solubilization. Experimental evaluations confirmed strain NCCP-2145 positive reactions for phosphorus solubilization, indole-3-acetic acid production, and ammonia production. Furthermore, strain NCCP-2145 exhibited tolerance to heavy metals (nickel, copper, and cadmium) and salinity levels up to 10% NaCl. Antibiotic susceptibility testing indicated resistance only to ceftazidime and the combination of amoxicillin/clavulanic acid. For phylogenomic analysis, strain NCCP-2145 was analyzed and compared to the closely related validly published type species P. oxydans DSM 20119T, revealing a similarity score of 98.64% based on 16S rRNA gene sequences and 89.1% based on DNA-DNA hybridization, confirming its classification as a member of species, P. oxydans. ConclusionsThis study significantly contributes to our understanding of the genomic characteristics, functional capabilities, and potential plant growth-promoting attributes of P. oxydans NCCP-2145. Future research should focus on unraveling the precise mechanisms underlying its plant growth-promoting abilities and exploring practical applications in sustainable agriculture and environmental restoration.How to cite: Bushra R, Uzair B, Ali A, et al. Draft genome sequence of a halotolerant plant growth-promoting bacterium Pseudarthrobacter oxydans NCCP-2145 isolated from rhizospheric soil of mangrove plant Avicennia marina. Electron J Biotechnol 2023;66. https://doi.org/10.1016/j.ejbt.2023.08.003.

Transcriptomic and Hormone Analyses Provide Insight into the Regulation of Axillary Bud Outgrowth of Eucommia ulmoides Oliver.

An essential indicator of Eucommia ulmoides Oliver (E. ulmoides) is the axillary bud; the growth and developmental capacity of axillary buds could be used to efficiently determine the structural integrity of branches and plant regeneration. We obtained axillary buds in different positions on the stem, including upper buds (CK), tip buds (T1), and bottom buds (T2), which provided optimal materials for the study of complicated regulatory networks that control bud germination. This study used transcriptomes to analyze the levels of gene expression in three different types of buds, and the results showed that 12,131 differentially expressed genes (DEGs) were discovered via the pairwise comparison of transcriptome data gathered from CK to T2, while the majority of DEGs (44.38%) were mainly found between CK and T1. These DEGs were closely related to plant hormone signal transduction and the amino acid biosynthesis pathway. We also determined changes in endogenous hormone contents during the process of bud germination. Interestingly, except for indole-3-acetic acid (IAA) content, which showed a significant upward trend (p < 0.05) in tip buds on day 4 compared with day 0, the other hormones showed no significant change during the process of germination. Then, the expression patterns of genes involved in IAA biosynthesis and signaling were examined through transcriptome analysis. Furthermore, the expression levels of genes related to IAA biosynthesis and signal transduction were upregulated in tip buds. Particularly, the expression of the IAA degradation gene Gretchen Hagen 3 (GH3.1) was downregulated on day 4, which may support the concept that endogenous IAA promotes bud germination. Based on these data, we propose that IAA synthesis and signal transduction lead to morphological changes in tip buds during the germination process. On this basis, suggestions to improve the efficiency of the production and application of E. ulmoides are put forward to provide guidance for future research.

Enhance of tomato production and induction of changes on the organic profile mediated by Rhizobium biofortification.

The extensive use of chemical fertilizers has served as a response to the increasing need for crop production in recent decades. While it addresses the demand for food, it has resulted in a decline in crop productivity and a heightened negative environmental impact. In contrast, plant probiotic bacteria (PPB) offer a promising alternative to mitigate the negative consequences of chemical fertilizers. PPB can enhance nutrient availability, promote plant growth, and improve nutrient uptake efficiency, thereby reducing the reliance on chemical fertilizers. This study aimed to evaluate the impact of native Rhizobium strains, specifically Rhizobium calliandrae LBP2-1, Rhizobium mayense NSJP1-1, and Rhizobium jaguaris SJP1- 2, on the growth, quality, and rhizobacterial community of tomato crops. Various mechanisms promoting plant growth were investigated, including phosphate solubilization, siderophore production, indole acetic acid synthesis, and cellulose and cellulase production. Additionally, the study involved the assessment of biofilm formation and root colonization by GFP-tagged strains, conducted a microcosm experiment, and analyzed the microbial community using metagenomics of rhizospheric soil. The results showed that the rhizobial strains LBP2-1, NSJP1-1 and SJP1-2 had the ability to solubilize dicalcium phosphate, produce siderophores, synthesize indole acetic acid, cellulose production, biofilm production, and root colonization. Inoculation of tomato plants with native Rhizobium strains influenced growth, fruit quality, and plant microbiome composition. Metagenomic analysis showed increased Proteobacteria abundance and altered alpha diversity indices, indicating changes in rhizospheric bacterial community. Our findings demonstrate the potential that native Rhizobium strains have to be used as a plant probiotic in agricultural crops for the generation of safe food and high nutritional value.

Field-grown cotton shows genotypic variation in agronomic and physiological responses to waterlogging

ContextWaterlogging frequently occurs and causes serious damage to cotton. While genotypic variation in waterlogging tolerance has been reported in cotton, there is limited research on the difference in waterlogging tolerance among Chinese commercial cotton varieties, and whether waterlogging tolerance is related to their geographical origin remains unclear. MethodsTo this end, we conducted a comparative study to evaluate the waterlogging tolerance of commercial cotton varieties from three major cotton-growing regions in China. Field-grown cotton was subjected to seven days of waterlogging stress at early flowering. The effects of waterlogging on growth, seedcotton yield, yield reduction, and various physiological responses were assessed. ResultsThe losses of seedcotton yield and biological yield of cotton varieties from the Yangtze River valley were the lowest (7.6% and 4.7%), followed by those from the Yellow River valley (14.4% and 7.7%), while the losses of cotton varieties from the Northwest Inland were the greatest (21.8% and 15.5%). This indicated that cotton ecotypes from the Yangtze River valley and Yellow River valley, characterized by higher precipitation, exhibit greater tolerance to waterlogging than those from the Northwest Inland. The increases in H2O2, malondialdehyde (MDA), and abscisic acid (ABA) contents in the cotton variety from the Yangtze River valley (YZ1) were the lowest (10.8%, 18.6%, and 20.8%, respectively), followed by those from the Yellow River valley (YL1) (32.6%, 33.2%, and 79.9%, respectively), while the increases in cotton varieties from the Northwest Inland (NW1) were the greatest (37.9%, 42.8%, and 84.4%, respectively). The decreases in indole-3-acetic acid (IAA), nitric oxide (NO), and nitrogen (N) contents of YZ1 were the lowest (10.3%, 32.5%, and 25.6%, respectively), followed by those from YL1 (12.7%, 39.8%, and 30.2%, respectively), while the decreases of NW1 were the greatest (24.9%, 48.3%, and 45.1%, respectively). Quantitative real-time PCR analysis showed the highest expression of the NO (GhNIR) and IAA (GhYUC8) synthesis genes, but the lowest expression of the genes involved in H2O2 production (GhRBOHC), and ABA synthesis (GhNCED2) in YZ1, followed by those in YL1 and NW1, indicating that gene expression patterns aligned with the changes of NO, IAA, H2O2 and ABA contents. Ten days after waterlogging relief, waterlogged YZ1 exhibited the greatest increases in biomass, leaf area, and canopy photosynthesis (44.1%, 40.0%, and 46.4%, respectively), followed by YL1 (39.0%, 36.9% and 40.5%, respectively), while NW1 showed the lowest increases (36.3%, 32.6% and 35.4%, respectively), indicating stronger compensatory growth in the Yangtze River valley cotton variety. ConclusionsThe results suggest that cotton varieties from the Yangtze River valley were more tolerant to waterlogging as evidenced by the lower level of damage and stronger compensatory growth than those from other geographical origins. We propose that quiescence adaptation and compensatory growth are the two main strategies employed by cotton to cope with waterlogging stress. This study enhances our understanding of the damage caused by waterlogging and sheds light on the adaptive mechanisms of cotton. Furthermore, it provides valuable insights for the breeding waterlogging-tolerant cotton varieties and improving cultivation practices.

DNA-Binding One Finger Transcription Factor PhDof28 Regulates Petal Size in Petunia.

Petal size is a key indicator of the ornamental value of plants, such as Petunia hybrida L., which is a popular ornamental species worldwide. Our previous study identified a flower-specific expression pattern of a DNA-binding one finger (Dof)-type transcription factor (TF) PhDof28, in the semi-flowering and full-flowering stages of petunia. In this study, subcellular localization and activation assays showed that PhDof28 was localized in the cell nucleus and could undergo in vitro self-activation. The expression levels of PhDof28 tended to be significantly up-regulated at the top parts of petals during petunia flower opening. Transgenic petunia 'W115' and tobacco plants overexpressing PhDof28 showed similar larger petal phenotypes. The cell sizes at the middle and top parts of transgenic petunia petals were significantly increased, along with higher levels of endogenous indole-3-acetic acid (IAA) hormone. Interestingly, the expression levels of two TFs, PhNAC100 and PhBPEp, which were reported as negative regulators for flower development, were dramatically increased, while the accumulation of jasmonic acid (JA), which induces PhBPEp expression, was also significantly enhanced in the transgenic petals. These results indicated that PhDof28 overexpression could increase petal size by enhancing the synthesis of endogenous IAA in petunias. Moreover, a JA-related feedback regulation mechanism was potentially activated to prevent overgrowth of petals in transgenic plants. This study will not only enhance our knowledge of the Dof TF family, but also provide crucial genetic resources for future improvements of plant ornamental traits.

Regulation of indole-3-acetic acid biosynthesis and consequences of auxin production deficiency in Serratia plymuthica.

Indole-3-acetic acid (IAA) is emerging as a key intra- and inter-kingdom signal molecule that modulates a wide range of processes of importance during plant-microorganism interaction. However, the mechanisms by which IAA carries out its functions in bacteria as well as the regulatory processes by which bacteria modulate auxin production are largely unknown. Here, we found that IAA synthesis deficiency results in important global transcriptional changes in the broad-range antibiotic-producing rhizobacterium Serratia plymuthica A153. Most pronounced transcriptional changes were observed in various gene clusters for aromatic acid metabolism, including auxin catabolism. To delve into the corresponding molecular mechanisms, different regulatory proteins were biochemically characterized. Among them, a TyrR orthologue was essential for IAA production through the activation of the ipdc gene encoding a key enzyme for IAA biosynthesis. We showed that TyrR specifically recognizes different aromatic amino acids which, in turn, alters the interactions of TyrR with the ipdc promoter. Screening of mutants defective in various transcriptional and post-transcriptional regulators allowed the identification of additional regulators of IAA production, including PigP and quorum sensing-related genes. Advancing our knowledge on the mechanisms that control the IAA biosynthesis in beneficial phytobacteria is of biotechnological interest for improving agricultural productivity and sustainable agricultural development.

Assessing the growth-promoting traits of actinobacteria spp. isolated from Cleome africana: Implications on growth and root enhancement of Medicago sativa

ObjectiveEndophytes actinobacteria isolated from the Cleome africana shoot and root tissues were compared for their growth promotion (PGP) traits and their beneficial effects on shoot and root enhancement evaluated using Medicago sativa as test crop. MethodsHealthy plants of C. africana evolved for long periods on heavy metal mining sites were sampled and the resident endophytes actinobacteria communities in root and leaves tissues isolated and characterized based on their 16 s rRNA regions and a culture dependent approach. The growth-promoting traits in terms of phosphate solubilization activity, siderophore production, indole acetic acid synthesis and ACC deaminase activity, resistance to drought and salt stresses were studied for the selected endophytes. The beneficial effect of the two selected actinobacteria and their consortium in promoting growth of M. sativa plants from an inoculation assay that comprised four treatments: [a control (Con), inoculation with Streptomyces sp. (A3), inoculation with Amycolatopsis sp. (A4), and a consortium of A3+A4]. Sixty days after sowing, plants were harvested, and the biomass production was measured. ResultsThe six isolated actinobacteria strains were identified as members of the Streptomyces, Amycolatopsis and Nocardia genus. Isolates of A2 and A4 presented increased identity to A. endophytica (99.10%) and A. nivea (99.44%) respectively, isolates A1 were in the Nocardia genus, with high affinity to the N.m exicana (98.7% 16S rRNA similarity). Isolates A3 was a non-cultured and not yet identified, while the isolates A5 and A6 all from the Streptomyces genus. Isolates A6 showed high affinity S. xishensis, strain YIM M 10378, and the isolates A5 were closely related to S. nogalater (100%). Cultures of isolates A3 and A4 and their consortium was used to inoculate M. sativa and the shoot, root dry weight and total biomass (shoot+root) was higher in the inoculated plants than uninoculated ones. ConclusionThe significant increase in plant growth implies that these actinobacteria can be used as inoculants to improve crop plant growth in semi-arid regions.

Effects of Different Growth Hormones on Rooting and Endogenous Hormone Content of Two Morus alba L. Cuttings

This study aimed to explore the effects of different concentrations of indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), and indene-naphthaleneacetic acid (ABT-1) on the rooting and dynamic changes of the endogenous hormone content of Australian Mulberry (vegetable Mulberry) and Kirin mulberry (Fruit Mulberry) hardwood cuttings. As exhibited by the results, the rooting process of both vegetable mulberry and fruit mulberry could be divided into three stages, namely the initiation stage (1–18 days), the callus formation stage (18–28 days), and the adventitious root formation and elongation stage (28–48 days). The two treatments with 1000 mg·L−1 ABT-1 and 500 mg·L−1 ABT-1 achieved the highest rooting efficiencies of vegetable mulberry and fruit mulberry, significantly higher than those of other treatments (p &lt; 0.01), with average rooting rates of 63.3% and 68.7%, and rooting efficiency indices of 25.3 and 34.3, respectively. During the rooting process, the contents of endogenous IAA and zeatin riboside (ZR) and the ratios of IAA/ABA and IAA/ZR presented a trend of decreasing before increasing, while the abscisic acid (ABA) and jasmonic acid (JA) contents exhibited a trend of increasing before decreasing, and the gibberellin (GA3), strigolactone (SL), and IBA contents showed a continuous decreasing trend. Hence, ABT-1 was effective in inducing the synthesis of IAA, IBA, JA, and SL, reducing the contents of ABA, ZR, and GA3, and promoting the rooting of vegetable mulberry and fruit mulberry cuttings. For fruit mulberry and vegetable mulberry cuttings, the optimal concentrations of ABT-1 were 500 mg·L−1 and 1000 mg·L−1, respectively, demonstrating applicability for the efficient propagation of Morus alba L. cuttings.