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877200.9700The role of drought response genes and plant growth promoting bacteria on plant growth promotion under sustainable agriculture: A review. Drought is a major stressor that poses significant challenges for agricultural practices. It becomes difficult to meet the global demand for food crops and fodder. Plant physiology, physico-chemistry and morphology changes in plants like decreased photosynthesis and transpiration rate, overproduction of reactive oxygen species, repressed shoot and root shoot growth and modified stress signalling pathways by drought, lead to detrimental impacts on plant development and output. Coping with drought stress requires a variety of adaptations and mitigation techniques. Crop yields could be effectively increased by employing plant growth-promoting rhizobacteria (PGPR), which operate through many mechanisms. These vital microbes colonise the rhizosphere of crops and promote drought resistance by producing exopolysaccharides (EPS), 1-aminocyclopropane-1-carboxylate (ACC) deaminase and phytohormones including volatile compounds. The upregulation or downregulation of stress-responsive genes causes changes in root architecture due to acquiring drought resistance. Further, PGPR induces osmolyte and antioxidant accumulation. Another key feature of microbial communities associated with crops includes induced systemic tolerance and the production of free radical-scavenging enzymes. This review is focused on detailing the role of PGPR in assisting plants to adapt to drought stress.202439002396
876510.9699Pseudomonas chlororaphis IRHB3 assemblies beneficial microbes and activates JA-mediated resistance to promote nutrient utilization and inhibit pathogen attack. INTRODUCTION: The rhizosphere microbiome is critical to plant health and resistance. PGPR are well known as plant-beneficial bacteria and generally regulate nutrient utilization as well as plant responses to environmental stimuli. In our previous work, one typical PGPR strain, Pseudomonas chlororaphis IRHB3, isolated from the soybean rhizosphere, had positive impacts on soil-borne disease suppression and growth promotion in the greenhouse, but its biocontrol mechanism and application in the field are not unclear. METHODS: In the current study, IRHB3 was introduced into field soil, and its effects on the local rhizosphere microbiome, disease resistance, and soybean growth were comprehensively analyzed through high-throughput sequencing and physiological and molecular methods. RESULTS AND DISCUSSION: We found that IRHB3 significantly increased the richness of the bacterial community but not the structure of the soybean rhizosphere. Functional bacteria related to phosphorus solubilization and nitrogen fixation, such as Geobacter, Geomonas, Candidatus Solibacter, Occallatibacter, and Candidatus Koribacter, were recruited in rich abundance by IRHB3 to the soybean rhizosphere as compared to those without IRHB3. In addition, the IRHB3 supplement obviously maintained the homeostasis of the rhizosphere microbiome that was disturbed by F. oxysporum, resulting in a lower disease index of root rot when compared with F. oxysporum. Furthermore, JA-mediated induced resistance was rapidly activated by IRHB3 following PDF1.2 and LOX2 expression, and meanwhile, a set of nodulation genes, GmENOD40b, GmNIN-2b, and GmRIC1, were also considerably induced by IRHB3 to improve nitrogen fixation ability and promote soybean yield, even when plants were infected by F. oxysporum. Thus, IRHB3 tends to synergistically interact with local rhizosphere microbes to promote host growth and induce host resistance in the field.202438380096
847120.9699Effects of Klebsiella michiganensis LDS17 on Codonopsis pilosula growth, rhizosphere soil enzyme activities, and microflora, and genome-wide analysis of plant growth-promoting genes. Codonopsis pilosula is a perennial herbaceous liana with medicinal value. It is critical to promote Codonopsis pilosula growth through effective and sustainable methods, and the use of plant growth-promoting bacteria (PGPB) is a promising candidate. In this study, we isolated a PGPB, Klebsiella michiganensis LDS17, that produced a highly active 1-aminocyclopropane-1-carboxylate deaminase from the Codonopsis pilosula rhizosphere. The strain exhibited multiple plant growth-promoting properties. The antagonistic activity of strain LDS17 against eight phytopathogenic fungi was investigated, and the results showed that strain LDS17 had obvious antagonistic effects on Rhizoctonia solani, Colletotrichum camelliae, Cytospora chrysosperma, and Phomopsis macrospore with growth inhibition rates of 54.22%, 49.41%, 48.89%, and 41.11%, respectively. Inoculation of strain LDS17 not only significantly increased the growth of Codonopsis pilosula seedlings but also increased the invertase and urease activities, the number of culturable bacteria, actinomycetes, and fungi, as well as the functional diversity of microbial communities in the rhizosphere soil of the seedlings. Heavy metal (HM) resistance tests showed that LDS17 is resistant to copper, zinc, and nickel. Whole-genome analysis of strain LDS17 revealed the genes involved in IAA production, siderophore synthesis, nitrogen fixation, P solubilization, and HM resistance. We further identified a gene (koyR) encoding a plant-responsive LuxR solo in the LDS17 genome. Klebsiella michiganensis LDS17 may therefore be useful in microbial fertilizers for Codonopsis pilosula. The identification of genes related to plant growth and HM resistance provides an important foundation for future analyses of the molecular mechanisms underlying the plant growth promotion and HM resistance of LDS17. IMPORTANCE: We comprehensively evaluated the plant growth-promoting characteristics and heavy metal (HM) resistance ability of the LDS17 strain, as well as the effects of strain LDS17 inoculation on the Codonopsis pilosula seedling growth and the soil qualities in the Codonopsis pilosula rhizosphere. We conducted whole-genome analysis and identified lots of genes and gene clusters contributing to plant-beneficial functions and HM resistance, which is critical for further elucidating the plant growth-promoting mechanism of strain LDS17 and expanding its application in the development of plant growth-promoting agents used in the environment under HM stress.202438563743
1830.9690Antivirulence effects of cell-free culture supernatant of endophytic bacteria against grapevine crown gall agent, Agrobacterium tumefaciens, and induction of defense responses in plantlets via intact bacterial cells. BACKGROUND: Crown gall disease caused by Agrobacterium tumefaciens is a very destructive affliction that affects grapevines. Endophytic bacteria have been discovered to control plant diseases via the use of several mechanisms. This research examined the potential for controlling crown gall by three endophytic bacteria that were previously isolated from healthy cultivated and wild grapevines including Pseudomonas kilonensis Ba35, Pseudomonas chlororaphis Ba47, and Serratia liquefaciens Ou55. RESULT: At various degrees, three endophytic bacteria suppressed the populations of A. tumefaciens Gh1 and greatly decreased the symptoms of crown gall. Furthermore, biofilm production and motility behaviors of A. tumefaciens Gh1were greatly inhibited by the Cell-free Culture Supernatant (CFCS) of endophytic bacteria. According to our findings, CFCS may reduce the adhesion of A. tumefaciens Gh1 cells to grapevine cv. Rashe root tissues as well as their chemotaxis motility toward the extract of the roots. When compared to the untreated control, statistical analysis showed that CFCS significantly reduced the swimming, twitching, and swarming motility of A. tumefaciens Gh1. The findings demonstrated that the endophytic bacteria effectively stimulated the production of plant defensive enzymes including superoxide dismutase (SOD), polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia lyase (PAL), and total soluble phenols at different time intervals in grapevine inoculated with A. tumefaciens Gh1. The Ba47 strain markedly increased the expression levels of defense genes associated with plant resistance. The up-regulation of PR1, PR2, VvACO1, and GAD1 genes in grapevine leaves indicates the activation of SA and JA pathways, which play a role in enhancing resistance to pathogen invasion. The results showed that treating grapevine with Ba47 increased antioxidant defense activities and defense-related gene expression, which reduced oxidative damage caused by A. tumefaciens and decreased the incidence of crown gall disease. CONCLUSION: This is the first study on how A. tumefaciens, the grapevine crown gall agent, is affected by CFCS generated by endophytic bacteria in terms of growth and virulence features. To create safer plant disease management techniques, knowledge of the biocontrol processes mediated by CFCS during microbial interactions is crucial.202438336608
877140.9686Plant Transcriptome Reprograming and Bacterial Extracellular Metabolites Underlying Tomato Drought Resistance Triggered by a Beneficial Soil Bacteria. Water deficit is one of the major constraints to crop production and food security worldwide. Some plant growth-promoting rhizobacteria (PGPR) strains are capable of increasing plant drought resistance. Knowledge about the mechanisms underlying bacteria-induced plant drought resistance is important for PGPR applications in agriculture. In this study, we show the drought stress-mitigating effects on tomato plants by the Bacillus megaterium strain TG1-E1, followed by the profiling of plant transcriptomic responses to TG1-E1 and the profiling of bacterial extracellular metabolites. Comparison between the transcriptomes of drought-stressed plants with and without TG1-E1 inoculation revealed bacteria-induced transcriptome reprograming, with highlights on differentially expressed genes belonging to the functional categories including transcription factors, signal transduction, and cell wall biogenesis and organization. Mass spectrometry-based analysis identified over 40 bacterial extracellular metabolites, including several important regulators or osmoprotectant precursors for increasing plant drought resistance. These results demonstrate the importance of plant transcriptional regulation and bacterial metabolites in PGPR-induced plant drought resistance.202134207663
1350.9683Streptomyces sp. JCK-6131 Protects Plants Against Bacterial and Fungal Diseases via Two Mechanisms. Plant bacterial and fungal diseases cause significant agricultural losses and need to be controlled. Beneficial bacteria are promising candidates for controlling these diseases. In this study, Streptomyces sp. JCK-6131 exhibited broad-spectrum antagonistic activity against various phytopathogenic bacteria and fungi. In vitro assays showed that the fermentation filtrate of JCK-6131 inhibited the growth of bacteria and fungi with minimum concentration inhibitory (MIC) values of 0.31-10% and 0.31-1.25%, respectively. In the in vivo experiments, treatment with JCK-6131 effectively suppressed the development of apple fire blight, tomato bacterial wilt, and cucumber Fusarium wilt in a dose-dependent manner. RP-HPLC and ESI-MS/MS analyses indicated that JCK-6131 can produce several antimicrobial compounds, three of which were identified as streptothricin E acid, streptothricin D, and 12-carbamoyl streptothricin D. In addition, the disease control efficacy of the foliar application of JCK-6131 against tomato bacterial wilt was similar to that of the soil drench application, indicating that JCK-6131 could enhance defense resistance in plants. Molecular studies on tomato plants showed that JCK-6131 treatment induced the expression of the pathogenesis-related (PR) genes PR1, PR3, PR5, and PR12, suggesting the simultaneous activation of the salicylate (SA) and jasmonate (JA) signaling pathways. The transcription levels of PR genes increased earlier and were higher in treated plants than in untreated plants following Ralstonia solanacearum infection. These results indicate that Streptomyces sp. JCK-6131 can effectively control various plant bacterial and fungal diseases via two distinct mechanisms of antibiosis and induced resistance.202134603354
883060.9680Additive Effect of the Composition of Endophytic Bacteria Bacillus subtilis on Systemic Resistance of Wheat against Greenbug Aphid Schizaphis graminum Due to Lipopeptides. The use of biocontrol agents based on endophytic bacteria against phloem-feeding insects is limited by a lack of knowledge and understanding of the mechanism of action of the endophyte community that makes up the plant microbiome. In this work, the mechanisms of the additive action of endophytic strains B. subtilis 26D and B. subtilis 11VM on the resistance of bread spring wheat against greenbug aphid Schizaphis graminum, was studied. It was shown that B. subtilis 26D secreted lipopeptide surfactin and phytohormones cytokinins, and B. subtilis 11VM produced iturin and auxins into the cultivation medium. Both strains and their lipopeptide-rich fractions showed direct aphicidal activity against greenbug aphid. For the first time, it was shown that B. subtilis 26D and B. subtilis 11VM in the same manner, as well as their lipopeptide-rich fractions, activated the expression of salicylate- and ethylene-dependent PR genes, and influenced plant redox metabolism, which led to an increase in plant endurance against aphids. The composition of endophytic strains B. subtilis 26D + B. subtilis 11VM had an additive effect on plant resistance to aphids due to an increase in the number of endophytic bacterial cells, and, as well as due to the synergistic effect of their mixture of lipopeptides - surfactin + iturin, both on the aphid mortality and on the expression of PR1 and PR3 genes. All these factors can be the reason for the observed increase in the growth of plants affected by aphids under the influence of B. subtilis 26D and B. subtilis 11VM, individually and in composition. The study demonstrates the possibility of creating in the future an artificial composition to enhance plant microbiome with endophytic bacteria, which combines growth-promoting and plant immunity stimulating properties against phloem-feeding insects. This direction is one of the most promising approaches to green pesticide discovery in the future.202336676163
872570.9678CuO nanoparticles facilitate soybean suppression of Fusarium root rot by regulating antioxidant enzymes, isoflavone genes, and rhizosphere microbiome. BACKGROUND: Fusarium root rot is a widespread soil-borne disease severely impacting soybean yield and quality. Compared to traditional fertilizers' biological and environmental toxicity, CuO nanoparticles (NPs) hold promise for disease control in a low dose and high efficiency manner. METHODS: We conducted both greenhouse and field experiments, employing enzymatic assays, elemental analysis, qRT-PCR, and microbial sequencing (16S rRNA, ITS) to explore the potential of CuO NPs for sustainable controlling Fusarium-induced soybean disease. RESULTS: Greenhouse experiments showed that foliar spraying of CuO NPs (10, 100, and 500 mg L(-1)) promoted soybean growth more effectively than EDTA-CuNa(2) at the same dose, though 500 CuO NPs caused mild phytotoxicity. CuO NPs effectively controlled root rot, while EDTA-CuNa(2) worsened the disease severity by 0.85-34.04 %. CuO NPs exhibited more substantial antimicrobial effects, inhibiting F. oxysporum mycelial growth and spore germination by 5.04-17.55 % and 10.24-14.41 %, respectively. 100 mg L(-1) CuO NPs was the optimal concentration for balancing soybean growth and disease resistance. Additionally, CuO NPs boosted antioxidant enzyme activity (CAT, POD, and SOD) in leaves and roots, aiding in ROS clearance during pathogen invasion. Compared to the pathogen control, 100 mg L(-1) CuO NPs upregulated the relative expression of seven isoflavone-related genes (Gm4CL, GmCHS8, GmCHR, GmCHI1a, GmIFS1, GmUGT1, and GmMYB176) by 1.18-4.51 fold, thereby enhancing soybean disease resistance in place of progesterone-receptor (PR) genes. Field trials revealed that CuO NPs' high leaf-to-root translocation modulated soybean rhizosphere microecology. Compared to the pathogen control, 100 mg L(-1) CuO NPs increased nitrogen-fixing bacteria (Rhizobium, Azospirillum, Azotobacter) and restored disease-resistant bacteria (Pseudomonas, Burkholderia) and fungi (Trichoderma, Penicillium) to healthy levels. Furthermore, 100 mg L(-1) CuO NPs increased beneficial bacteria (Pedosphaeraceae, Xanthobacteraceae, SCI84, etc.) and fungi (Trichoderma, Curvularia, Hypocreales, etc.), which negatively correlated with F. oxysporum, while recruiting functional microbes to enhance soybean yield. CONCLUSION: 100 mg L(-1) CuO NPs effectively promoting soybean growth and providing strong resistance against root rot disease by improving antioxidant enzyme activity, regulating the relative expression of isoflavone-related genes, increasing beneficial bacteria and fungi and restoring disease-resistant. Our findings suggest that CuO NPs offer an environmentally sustainable strategy for managing soybean disease, with great potential for green production.202540096759
883180.9677Search for biocontrol agents among endophytic lipopeptide-synthesizing bacteria Bacillus spp. to protect wheat plants against Greenbug aphid (Schizaphis graminum). Beneficial endophytic bacteria can suppress the development of insect pests through direct antagonism, with the help of metabolites, or indirectly by the induction of systemic resistance through the regulation of hormonal signaling pathways. Lipopeptides are bacterial metabolites that exhibit direct antagonistic activity against many organisms, including insects. Also, lipopeptides are able to trigger induced systemic resistance (ISR) in plants against harmful organisms, but the physiological mechanisms of their action are just beginning to be studied. In this work, we studied ten strains of bacteria isolated from the tissues of wheat and potatoes. Sequencing of the 16S rRNA gene showed that all isolates belong to the genus Bacillus and to two species, B. subtilis and B. velezensis. The genes for lipopeptide synthetase - surfactin synthetase (Bs_srf ), iturin synthetase (Bs_ituA, Bs_ituB) and fengycin synthetase (Bs_fenD) - were identified in all bacterial isolates using PCR. All strains had high aphicidal activity against the Greenbug aphid (Schizaphis graminum Rond.) due to the synthesis of lipopeptides, which was proven using lipopeptide-rich fractions (LRFs) isolated from the strains. Endophytic lipopeptide-synthesizing strains of Bacillus spp. indirectly affected the viability of aphids, the endurance of plants against aphids and triggered ISR in plants, which manifested itself in the regulation of oxidative metabolism and the accumulation of transcripts of the Pr1, Pr2, Pr3, Pr6 and Pr9 genes due to the synthesis of lipopeptides, which was proven using LRF isolated from three strains: B. subtilis 26D, B. subtilis 11VM, and B. thuringiensis B-6066. We have for the first time demonstrated the aphicidal effect of fengycin and the ability of the fengycin-synthesizing strains and isolates, B. subtilis Ttl2, Bacillus sp. Stl7 and B. thuringiensis B-6066, to regulate components of the pro-/antioxidant system of aphid-infested plants. In addition, this work is the first to demonstrate an elicitor role of fengycin in triggering a systemic resistance to S. graminum in wheat plants. We have discovered new promising strains and isolates of endophytes of the genus Bacillus, which may be included in the composition of new biocontrol agents against aphids. One of the criteria for searching for new bacteria active against phloem-feeding insects can be the presence of lipopeptide synthetase genes in the bacterial genome.202438952706
1290.9675A Diketopiperazine, Cyclo-(L-Pro-L-Ile), Derived From Bacillus thuringiensis JCK-1233 Controls Pine Wilt Disease by Elicitation of Moderate Hypersensitive Reaction. Pine wilt disease (PWD) caused by the pine wood nematode (PWN) Bursaphelenchus xylophilus is one of the devastating diseases affecting pine forests worldwide. Although effective control measurements are still missing, induction of resistance could represent a possible eco-friendly alternative. In this study, induced resistance-based in vitro and in vivo screening tests were carried out for selection of bacteria with the ability to suppress PWD. Out of 504 isolated bacteria, Bacillus thuringiensis JCK-1233 was selected for its ability to boost pathogenesis-related 1 (PR1) gene expression, a marker of systemic acquired resistance. Moreover, treatment of pine seedlings with B. thuringiensis JCK-1233 resulted in increased expression of other defense-related genes, and significantly inhibited PWD development under greenhouse conditions. However, B. thuringiensis JCK-1233 showed no direct nematicidal activity against B. xylophilus. To identify the effective compound responsible for the induction of resistance in B. thuringiensis JCK-1233, several diketopiperazines (DPKs) including cyclo-(D-Pro-L-Val), cyclo-(L-Pro-L-Ile), cyclo-(L-Pro-L-Phe), and cyclo-(L-Leu-L-Val) were isolated and tested. Foliar treatment of pine seedlings with Cyclo-(L-Pro-L-Ile) resulted in suppression of PWD severity and increased the expression of defense-related genes similarly to B. thuringiensis JCK-1233 treatment. Interestingly, treatment with B. thuringiensis JCK-1233 or cyclo-(L-Pro-L-Ile) showed moderately enhanced expression of PR-1, PR-2, PR-3, PR-4, PR-5, and PR-9 genes following inoculation with PWN compared to that in the untreated control, indicating that they mitigated the burst of hypersensitive reaction in susceptible pine seedlings. In contrast, they significantly increased the expression levels of PR-6 and PR-10 before PWN inoculation. In conclusion, foliar spraying with either B. thuringiensis JCK-1233 culture suspension or DPKs could induce resistance in pine seedlings, thereby alleviating the serious damage by PWD. Taken together, this study supports aerial spraying with eco-friendly biotic or abiotic agents as a valuable strategy that may mark an epoch for the control of PWD in pine forests.202032849672
37100.9673N-3-Oxo-Octanoyl Homoserine Lactone Primes Plant Resistance Against Necrotrophic Pathogen Pectobacterium carotovorum by Coordinating Jasmonic Acid and Auxin-Signaling Pathways. Many Gram-negative bacteria use small signal molecules, such as N-acyl-homoserine lactones (AHLs), to communicate with each other and coordinate their collective behaviors. Recently, increasing evidence has demonstrated that long-chained quorum-sensing signals play roles in priming defense responses in plants. Our previous work indicated that a short-chained signal, N-3-oxo-octanoyl homoserine lactone (3OC8-HSL), enhanced Arabidopsis resistance to the hemi-biotrophic bacteria Pseudomonas syringae pv. tomato DC3000 through priming the salicylic acid (SA) pathway. Here, we found that 3OC8-HSL could also prime resistance to the necrotrophic bacterium Pectobacterium carotovorum ssp. carotovorum (Pcc) through the jasmonic acid (JA) pathway, and is dependent on auxin responses, in both Chinese cabbage and Arabidopsis. The subsequent Pcc invasion triggered JA accumulation and increased the down-stream genes' expressions of JA synthesis genes (LOX, AOS, and AOC) and JA response genes (PDF1.2 and VSP2). The primed state was not observed in the Arabidopsis coi1-1 and jar1-1 mutants, which indicated that the primed resistance to Pcc was dependent on the JA pathway. The 3OC8-HSL was not transmitted from roots to leaves and it induced indoleacetic acid (IAA) accumulation and the DR5 and SAUR auxin-responsive genes' expressions in seedlings. When Arabidopsis and Chinese cabbage roots were pretreated with exogenous IAA (10 μM), the plants had activated the JA pathway and enhanced resistance to Pcc, which implied that the JA pathway was involved in AHL priming by coordinating with the auxin pathway. Our findings provide a new strategy for the prevention and control of soft rot in Chinese cabbage and provide theoretical support for the use of the quorum-sensing AHL signal molecule as a new elicitor.202235774826
20110.9673Paraburkholderia phytofirmans PsJN triggers local and systemic transcriptional reprogramming in Arabidopsis thaliana and increases resistance against Botrytis cinerea. Fungal pathogens are one of the main causes of yield losses in many crops, severely affecting agricultural production worldwide. Among the various approaches to alleviate this problem, beneficial microorganisms emerge as an environmentally friendly and sustainable alternative. In addition to direct biocontrol action against pathogens, certain plant growth-promoting bacteria (PGPB) enhance the plant immune defense to control diseases through induced systemic resistance (ISR). Paraburkholderia phytofirmans PsJN has been shown as an efficient biocontrol agent against diseases. However, the specific mechanisms underlying these beneficial effects at both local and systemic level remain largely unknown. In this study, we investigated the transcriptional response of Arabidopsis thaliana at above- and below-ground levels upon interaction with P. phytofirmans PsJN, and after Botrytis cinerea infection. Our data clearly support the protective effect of P. phytofirmans PsJN through ISR against B. cinerea in plants grown in both soil and hydroponic conditions. The comparative transcriptome analysis of the mRNA and miRNA sequences revealed that PsJN modulates the expression of genes involved in abiotic stress responses, microbe-plant interactions and ISR, with ethylene signaling pathway genes standing out. In roots, PsJN predominantly downregulated the expression of genes related to microbe perception, signaling and immune response, indicating that PsJN locally provoked attenuation of defense responses to facilitate and support colonization and the maintenance of mutualistic relationship. In leaves, the increased expression of defense-related genes prior to infection in combination with the protective effect of PsJN observed in later stages of infection suggests that bacterial inoculation primes plants for enhanced systemic immune response after subsequent pathogen attack.202540530279
8475120.9673Antibacterial Activity of Endophytic Bacteria Against Sugar Beet Root Rot Agent by Volatile Organic Compound Production and Induction of Systemic Resistance. The volatile organic compounds (VOCs) produced by endophytic bacteria have a significant role in the control of phytopathogens. In this research, the VOCs produced by the endophytic bacteria Streptomyces sp. B86, Pantoea sp. Dez632, Pseudomonas sp. Bt851, and Stenotrophomonas sp. Sh622 isolated from healthy sugar beet (Beta vulgaris) and sea beet (Beta maritima) were evaluated for their effects on the virulence traits of Bacillus pumilus Isf19, the causal agent of harvested sugar beet root rot disease. The gas chromatographymass spectrometry (GC-MS) analysis revealed that B86, Dez632, Bt851, and Sh622 produced 15, 28, 30, and 20 VOCs, respectively, with high quality. All antagonistic endophytic bacteria produced VOCs that significantly reduced soft root symptoms and inhibited the growth of B. pumilus Isf19 at different levels. The VOCs produced by endophytic bacteria significantly reduced swarming, swimming, and twitching motility by B. pumilus Isf19, which are important to pathogenicity. Our results revealed that VOCs produced by Sh622 and Bt851 significantly reduced attachment of B. pumilus Isf19 cells to sugar beetroots, and also all endophytic bacteria tested significantly reduced chemotaxis motility of the pathogen toward root extract. The VOCs produced by Dez632 and Bt851 significantly upregulated the expression levels of defense genes related to soft rot resistance. Induction of PR1 and NBS-LRR2 genes in sugar beetroot slices suggests the involvement of SA and JA pathways, respectively, in the induction of resistance against pathogen attack. Based on our results, the antibacterial VOCs produced by endophytic bacteria investigated in this study can reduce soft rot incidence.202235722285
8767130.9672Poly-γ-glutamic acid enhanced the drought resistance of maize by improving photosynthesis and affecting the rhizosphere microbial community. BACKGROUND: Compared with other abiotic stresses, drought stress causes serious crop yield reductions. Poly-γ-glutamic acid (γ-PGA), as an environmentally friendly biomacromolecule, plays an important role in plant growth and regulation. RESULTS: In this project, the effect of exogenous application of γ-PGA on drought tolerance of maize (Zea mays. L) and its mechanism were studied. Drought dramatically inhibited the growth and development of maize, but the exogenous application of γ-PGA significantly increased the dry weight of maize, the contents of ABA, soluble sugar, proline, and chlorophyll, and the photosynthetic rate under severe drought stress. RNA-seq data showed that γ-PGA may enhance drought resistance in maize by affecting the expression of ABA biosynthesis, signal transduction, and photosynthesis-related genes and other stress-responsive genes, which was also confirmed by RT-PCR and promoter motif analysis. In addition, diversity and structure analysis of the rhizosphere soil bacterial community demonstrated that γ-PGA enriched plant growth promoting bacteria such as Actinobacteria, Chloroflexi, Firmicutes, Alphaproteobacteria and Deltaproteobacteria. Moreover, γ-PGA significantly improved root development, urease activity and the ABA contents of maize rhizospheric soil under drought stress. This study emphasized the possibility of using γ-PGA to improve crop drought resistance and the soil environment under drought conditions and revealed its preliminary mechanism. CONCLUSIONS: Exogenous application of poly-γ-glutamic acid could significantly enhance the drought resistance of maize by improving photosynthesis, and root development and affecting the rhizosphere microbial community.202234979944
8770140.9670Phyllosphere symbiont promotes plant growth through ACC deaminase production. Plant growth promoting bacteria can confer resistance to various types of stress and increase agricultural yields. The mechanisms they employ are diverse. One of the most important genes associated with the increase in plant biomass and stress resistance is acdS, which encodes a 1-aminocyclopropane-1-carboxylate- or ACC-deaminase. The non-proteinogenic amino acid ACC is the precursor and means of long-distance transport of ethylene, a plant hormone associated with growth arrest. Expression of acdS reduces stress induced ethylene levels and the enzyme is abundant in rhizosphere colonizers. Whether ACC hydrolysis plays a role in the phyllosphere, both as assembly cue and in growth promotion, remains unclear. Here we show that Paraburkholderia dioscoreae Msb3, a yam phyllosphere symbiont, colonizes the tomato phyllosphere and promotes plant growth by action of its ACC deaminase. We found that acdS is required for improved plant growth but not for efficient leaf colonization. Strain Msb3 readily proliferates on the leaf surface of tomato, only occasionally spreading to the leaf endosphere through stomata. The strain can also colonize the soil or medium around the roots but only spreads into the root if the plant is wounded. Our results indicate that the degradation of ACC is not just an important trait of plant growth promoting rhizobacteria but also one of leaf dwelling phyllosphere bacteria. Manipulation of the leaf microbiota by means of spray inoculation may be more easily achieved than that of the soil. Therefore, the application of ACC deaminase containing bacteria to the phyllosphere may be a promising strategy to increasing plant stress resistance, pathogen control, and harvest yields.202337264153
11150.9663Diffusible signal factor primes plant immunity against Xanthomonas campestris pv. campestris (Xcc) via JA signaling in Arabidopsis and Brassica oleracea. BACKGROUND: Many Gram-negative bacteria use quorum sensing (QS) signal molecules to monitor their local population density and to coordinate their collective behaviors. The diffusible signal factor (DSF) family represents an intriguing type of QS signal to mediate intraspecies and interspecies communication. Recently, accumulating evidence demonstrates the role of DSF in mediating inter-kingdom communication between DSF-producing bacteria and plants. However, the regulatory mechanism of DSF during the Xanthomonas-plant interactions remain unclear. METHODS: Plants were pretreated with different concentration of DSF and subsequent inoculated with pathogen Xanthomonas campestris pv. campestris (Xcc). Pathogenicity, phynotypic analysis, transcriptome combined with metabolome analysis, genetic analysis and gene expression analysis were used to evaluate the priming effects of DSF on plant disease resistance. RESULTS: We found that the low concentration of DSF could prime plant immunity against Xcc in both Brassica oleracea and Arabidopsis thaliana. Pretreatment with DSF and subsequent pathogen invasion triggered an augmented burst of ROS by DCFH-DA and DAB staining. CAT application could attenuate the level of ROS induced by DSF. The expression of RBOHD and RBOHF were up-regulated and the activities of antioxidases POD increased after DSF treatment followed by Xcc inoculation. Transcriptome combined with metabolome analysis showed that plant hormone jasmonic acid (JA) signaling involved in DSF-primed resistance to Xcc in Arabidopsis. The expression of JA synthesis genes (AOC2, AOS, LOX2, OPR3 and JAR1), transportor gene (JAT1), regulator genes (JAZ1 and MYC2) and responsive genes (VSP2, PDF1.2 and Thi2.1) were up-regulated significantly by DSF upon Xcc challenge. The primed effects were not observed in JA relevant mutant coi1-1 and jar1-1. CONCLUSION: These results indicated that DSF-primed resistance against Xcc was dependent on the JA pathway. Our findings advanced the understanding of QS signal-mediated communication and provide a new strategy for the control of black rot in Brassica oleracea.202337404719
8697160.9662Deciphering the Root Endosphere Microbiome of the Desert Plant Alhagi sparsifolia for Drought Resistance-Promoting Bacteria. Drought is among the most destructive abiotic stresses limiting crop growth and yield worldwide. Although most research has focused on the contribution of plant-associated microbial communities to plant growth and disease suppression, far less is known about the microbes involved in drought resistance among desert plants. In the present study, we applied 16S rRNA gene amplicon sequencing to determine the structure of rhizosphere and root endosphere microbiomes of Alhagi sparsifolia Compared to those of the rhizosphere, endosphere microbiomes had lower diversity but contained several taxa with higher relative abundance; many of these taxa were also present in the roots of other desert plants. We isolated a Pseudomonas strain (LTGT-11-2Z) that was prevalent in root endosphere microbiomes of A. sparsifolia and promoted drought resistance during incubation with wheat. Complete genome sequencing of LTGT-11-2Z revealed 1-aminocyclopropane-1-carboxylate deaminases, siderophore, spermidine, and colanic acid biosynthetic genes, as well as type VI secretion system (T6SS) genes, which are likely involved in biofilm formation and plant-microbe interactions. Together, these results indicate that drought-enduring plants harbor bacterial endophytes favorable to plant drought resistance, and they suggest that novel endophytic bacterial taxa and gene resources may be discovered among these desert plants.IMPORTANCE Understanding microbe-mediated plant resistance to drought is important for sustainable agriculture. We performed 16S rRNA gene amplicon sequencing and culture-dependent functional analyses of Alhagi sparsifolia rhizosphere and root endosphere microbiomes and identified key endophytic bacterial taxa and their genes facilitating drought resistance in wheat. This study improves our understanding of plant drought resistance and provides new avenues for drought resistance improvement in crop plants under field conditions.202032220847
6014170.9661Whole genome sequencing and analysis of plant growth promoting bacteria isolated from the rhizosphere of plantation crops coconut, cocoa and arecanut. Coconut, cocoa and arecanut are commercial plantation crops that play a vital role in the Indian economy while sustaining the livelihood of more than 10 million Indians. According to 2012 Food and Agricultural organization's report, India is the third largest producer of coconut and it dominates the production of arecanut worldwide. In this study, three Plant Growth Promoting Rhizobacteria (PGPR) from coconut (CPCRI-1), cocoa (CPCRI-2) and arecanut (CPCRI-3) characterized for the PGP activities have been sequenced. The draft genome sizes were 4.7 Mb (56% GC), 5.9 Mb (63.6% GC) and 5.1 Mb (54.8% GB) for CPCRI-1, CPCRI-2, CPCRI-3, respectively. These genomes encoded 4056 (CPCRI-1), 4637 (CPCRI-2) and 4286 (CPCRI-3) protein-coding genes. Phylogenetic analysis revealed that both CPCRI-1 and CPCRI-3 belonged to Enterobacteriaceae family, while, CPCRI-2 was a Pseudomonadaceae family member. Functional annotation of the genes predicted that all three bacteria encoded genes needed for mineral phosphate solubilization, siderophores, acetoin, butanediol, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, chitinase, phenazine, 4-hydroxybenzoate, trehalose and quorum sensing molecules supportive of the plant growth promoting traits observed in the course of their isolation and characterization. Additionally, in all the three CPCRI PGPRs, we identified genes involved in synthesis of hydrogen sulfide (H2S), which recently has been proposed to aid plant growth. The PGPRs also carried genes for central carbohydrate metabolism indicating that the bacteria can efficiently utilize the root exudates and other organic materials as energy source. Genes for production of peroxidases, catalases and superoxide dismutases that confer resistance to oxidative stresses in plants were identified. Besides these, genes for heat shock tolerance, cold shock tolerance and glycine-betaine production that enable bacteria to survive abiotic stress were also identified.201425162593
8151180.9658Azospirillum: benefits that go far beyond biological nitrogen fixation. The genus Azospirillum comprises plant-growth-promoting bacteria (PGPB), which have been broadly studied. The benefits to plants by inoculation with Azospirillum have been primarily attributed to its capacity to fix atmospheric nitrogen, but also to its capacity to synthesize phytohormones, in particular indole-3-acetic acid. Recently, an increasing number of studies has attributed an important role of Azospirillum in conferring to plants tolerance of abiotic and biotic stresses, which may be mediated by phytohormones acting as signaling molecules. Tolerance of biotic stresses is controlled by mechanisms of induced systemic resistance, mediated by increased levels of phytohormones in the jasmonic acid/ethylene pathway, independent of salicylic acid (SA), whereas in the systemic acquired resistance-a mechanism previously studied with phytopathogens-it is controlled by intermediate levels of SA. Both mechanisms are related to the NPR1 protein, acting as a co-activator in the induction of defense genes. Azospirillum can also promote plant growth by mechanisms of tolerance of abiotic stresses, named as induced systemic tolerance, mediated by antioxidants, osmotic adjustment, production of phytohormones, and defense strategies such as the expression of pathogenesis-related genes. The study of the mechanisms triggered by Azospirillum in plants can help in the search for more-sustainable agricultural practices and possibly reveal the use of PGPB as a major strategy to mitigate the effects of biotic and abiotic stresses on agricultural productivity.201829728787
17190.9658Biocontrol Potential of Endophytic Plant-Growth-Promoting Bacteria against Phytopathogenic Viruses: Molecular Interaction with the Host Plant and Comparison with Chitosan. Endophytic plant-growth-promoting bacteria (ePGPB) are interesting tools for pest management strategies. However, the molecular interactions underlying specific biocontrol effects, particularly against phytopathogenic viruses, remain unexplored. Herein, we investigated the antiviral effects and triggers of induced systemic resistance mediated by four ePGPB (Paraburkholderia fungorum strain R8, Paenibacillus pasadenensis strain R16, Pantoea agglomerans strain 255-7, and Pseudomonas syringae strain 260-02) against four viruses (Cymbidium Ring Spot Virus-CymRSV; Cucumber Mosaic Virus-CMV; Potato Virus X-PVX; and Potato Virus Y-PVY) on Nicotiana benthamiana plants under controlled conditions and compared them with a chitosan-based resistance inducer product. Our studies indicated that ePGPB- and chitosan-treated plants presented well-defined biocontrol efficacy against CymRSV and CMV, unlike PVX and PVY. They exhibited significant reductions in symptom severity while promoting plant height compared to nontreated, virus-infected controls. However, these phenotypic traits showed no association with relative virus quantification. Moreover, the tested defense-related genes (Enhanced Disease Susceptibility-1 (EDS1), Non-expressor of Pathogenesis-related genes-1 (NPR1), and Pathogenesis-related protein-2B (PR2B)) implied the involvement of a salicylic-acid-related defense pathway triggered by EDS1 gene upregulation.202235805989