Publications by authors named "Chuan-Chao Dai"

72 Publications

Activation of Naringenin and Kaempferol through Pathway Refactoring in the Endophyte .

ACS Synth Biol 2021 Jul 12. Epub 2021 Jul 12.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing 210023, Jiangsu Province China.

Abundant gene clusters of natural products are observed in the endophytic fungus ; however, most of them are silent. Herein, a plug-and-play DNA assembly tool has been applied for flavonoid synthesis in A shuttle plasmid was constructed based on , , and with screening markers , , and , respectively. Each fragment or cassette was successively assembled by overlap extension PCR with at least 40-50 bp homologous arms in for generating a new vector. Seven native promoters were screened by the DNA assembly based on the fluorescence intensity of the mCherry reporter gene in , and two of them were new promoters. The key enzyme chalcone synthase was the limiting step of the pathway. The naringenin and kaempferol pathways were refactored and activated with the titers of naringenin and kaempferol of 121.53 mg/L and 75.38 mg/L in using fed-batch fermentation, respectively. This study will be efficient and helpful for the biosynthesis of secondary metabolites.
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http://dx.doi.org/10.1021/acssynbio.1c00205DOI Listing
July 2021

Jasmonate signaling restricts root soluble sugar accumulation and drives root-fungus symbiosis loss at flowering by antagonizing gibberellin biosynthesis.

Plant Sci 2021 Aug 19;309:110940. Epub 2021 May 19.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, China. Electronic address:

Jasmonate restricts accumulation of constitutive and fungus-induced root soluble sugars at flowering stage, and thus reduces root beneficial fungal colonization, but little is known about how these are achieved. To determine whether jasmonate-mediated depletion of soluble sugars is the result of direct phytohormonal cross-talk or indirect induced defensive secondary metabolism, we first profiled soluble sugar and tryptophan (Trp)-derived defensive secondary metabolites in the roots of wild-type and jasmonate signaling-impaired Arabidopsis thaliana at flowering upon a beneficial fungus Phomopsis liquidambaris inoculation. Next, jasmonate and gibberellin signaling were manipulated to determine the relationship between jasmonate and gibberellin, and to quantify the effects of these phytohormones on fungal colonization degree, soluble sugar accumulation, Trp-derived secondary metabolites production, and sugar source-sink transport and metabolism. Gibberellin complementation increased Ph. liquidambaris colonization and rescued jasmonate-dependent root soluble sugar depletion and phloem sugar transport and root invertase activity without influencing jasmonate-induced Trp-derived secondary metabolites production at flowering. Furthermore, jasmonate signaling antagonized gibberellin biosynthesis in Ph. liquidambaris-inoculated roots. Our results suggest a phytohormonal antagonism model that jasmonate signaling restricts root soluble sugar accumulation through antagonizing gibberellin biosynthesis rather than through promoting Trp-derived secondary metabolites production and thus drives beneficial fungal colonization decline at flowering.
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http://dx.doi.org/10.1016/j.plantsci.2021.110940DOI Listing
August 2021

Root endophyte-enhanced peanut-rhizobia interaction is associated with regulation of root exudates.

Microbiol Res 2021 Sep 14;250:126765. Epub 2021 May 14.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, Jiangsu Province, 210023, China. Electronic address:

Root exudates play a crucial role in the symbiosis between leguminous plants and rhizobia. Our previous studies have shown that a fungal endophyte Phomopsis liquidambaris promotes peanut-rhizobia nodulation and nitrogen fixation, but the underlying mechanism are largely unknown. Here, we explore the role of peanut root exudates in Ph. liquidambaris-mediated nodulation enhancement. We first collected root exudates from Ph. liquidambaris-inoculated and un-inoculated peanuts and determined their effects on rhizobial growth, biofilm formation, chemotaxis, nodC gene expression, and peanut nodulation. Our results found a positive effect of Ph. liquidambaris-inoculated root exudates on these characteristics of rhizobia. Next, we compared the root exudates profile of Ph. liquidambaris-inoculated and un-inoculated plants and found that Ph. liquidambaris altered the concentrations of phenolic acids, flavonoids, organic acids and amino acids in root exudates. Furthermore, the rhizobial chemotaxis, growth and biofilm formation in response to the changed compounds at different concentrations showed that all of the test compounds induced rhizobial chemotactic behavior, and organic acids (citric acid and oxalic acid) and amino acid (glutamate, glycine and glutamine) at higher concentrations increased rhizobial growth and biofilm formation. Collectively, our results suggest that root exudates alterations contribute to Ph. liquidambaris-mediated peanut-rhizobia nodulation enhancement.
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http://dx.doi.org/10.1016/j.micres.2021.126765DOI Listing
September 2021

Destruction of the soil microbial ecological environment caused by the over-utilization of the rice-crayfish co-cropping pattern.

Sci Total Environ 2021 Sep 15;788:147794. Epub 2021 May 15.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Centre for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China. Electronic address:

The rice-crayfish co-cropping pattern is a traditional method for the intensive utilization of rice fields. In recent years, this pattern has been over-developed in many countries and regions, especially in China, because of its simple agronomic technology and high economic benefits. However, little is known about the potential ecological problems regarding soil microorganisms caused by the over-utilization of this pattern. The results show that rice-crayfish co-cropping, when over-utilized for a long time, reduced soil microbial richness and diversity compared with rice monocropping. A decrease in bacterial abundance in the nitrogen cycle and an increase in bacterial abundance in the carbon cycle led to a decrease in the nitrogen cycle function and an increase in the carbon cycle function. In an analysis of bacteria that are sensitive to cropping patterns, it was found that in the rice-crayfish co-cropping, the relative abundances of sensitive OTUs from Firmicutes (Bacillus and Clostridium) and Chloroflexi (Anaerolineaceae) were significantly higher during the entire growth period than those observed in the rice monocropping pattern, while the relative abundances of sensitive OTUs from Nitrospirae (Nitrospira), Gemmatimonadetes (Gemmatimonas), and Actinobacteria (Nocardioides) were significantly lower than those observed in the rice monocropping pattern. A network analysis shows that growth-period-sensitive OTUs drive the co-occurrence network modules, although the OTUs also have positive and negative correlations among modules but a positive synergistic effect on the regulation of soil nutrients. In addition, OTUs that were sensitive at the booting stage and filling stage were the key microbial groups in the rice-crayfish co-cropping and rice monocropping networks, respectively. Understanding the classifications and functions of sensitive microbes present during the rice growth period is the basis for formulating a microbial flora management strategy for the rice-crayfish co-cropping pattern, which is of great significance for adjusting agricultural management measures and controlling current soil microbial ecological problems.
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http://dx.doi.org/10.1016/j.scitotenv.2021.147794DOI Listing
September 2021

Soil legacy of arbuscular mycorrhizal fungus Gigaspora margarita: The potassium-sequestering glomalin improves peanut (Arachis hypogaea) drought resistance and pod yield.

Microbiol Res 2021 Aug 29;249:126774. Epub 2021 Apr 29.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, China. Electronic address:

In agroecosystems, drought stress severely threatens crops development. Although potassium (K) is required in amounts by crops under drought stress, the mobilization and availablity of K are limited by the soil water status. Arbuscular mycorrhizal (AM) fungi can form mutualistic associations with most crops and play direct or indirect roles in the host drought resistance. Considering that the glomalin generated by living AM fungal hyphae can sequester multiple minerals, however, the function of mineral-sequestering glomalin in the crop drought resistance remains unclear. In this study, peanuts cultivated in the sterilized soil with a history of AM fungi inoculation showed significantly enhanced leaf K accumulation, drought resistance and pod yield under drought stress. Through the collection of different types of mineral-sequestering glomalin from living AM fungal hyphae, the peanut drought resistance was improved only when K-sequestering glomalin was added. Moreover, we found that peanut root exudates could prime the dissociation of glomalin-bound K and further satisfy the K requirement of crops. Our study is the first report that K-sequestering glomalin could improve drought performance and peanut pod yield, and it helps us to understand the ecological importance of improving AM symbiosis to face agricultural challenges.
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http://dx.doi.org/10.1016/j.micres.2021.126774DOI Listing
August 2021

Effects of multi-phase inoculation on the fungal community related with the improvement of medicinal herbal residues composting.

Environ Sci Pollut Res Int 2021 Jun 1;28(22):27998-28013. Epub 2021 Feb 1.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Centre for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, 210023, China.

Composting has become the most important way to recycle medicinal herbal residues (MHRs). The traditional composting method, adding a microbial agent at one time, has been greatly limited due to its low composting efficiency, mutual influence of microbial agents, and unstable compost products. This study was conducted to assess the effect of multi-phase inoculation on the lignocellulose degradation, enzyme activities, and fungal community during MHRs composting. The results showed that multi-phase inoculation treatment had the highest thermophilic temperature (68.2 °C) and germination index (102.68%), significantly improved available phosphorus content, humic acid, and humic substances concentration, accelerated the degradation of cellulose and lignin, and increased the activities of cellulase in the mature phase, xylanase, manganese peroxidase, and utilization of phenolic compounds. Furthermore, the non-metric multi-dimensional scaling showed that the composting process and inoculation significantly influenced fungal community composition. In multi-phase inoculation treatment, Thermomyces in mesophilic, thermophilic, and mature phase, unclassified_Sordariales, and Coprinopsis in mature phase were the dominant genus that might be the main functional groups to degrade lignocellulose and improve the MHRs composting process.
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http://dx.doi.org/10.1007/s11356-021-12569-7DOI Listing
June 2021

Endophytic fungus Phomopsis liquidambaris B3 induces rice resistance to RSRD caused by Fusarium proliferatum and promotes plant growth.

J Sci Food Agric 2021 Aug 12;101(10):4059-4075. Epub 2021 Jan 12.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, China.

Background: Rice spikelet rot disease (RSRD) is an emerging disease that significantly reduces rice yield and quality. In this study, we evaluated the potential use of the broad-spectrum endophytic fungus Phomopsis liquidambaris B3 as a biocontrol agent against RSRD. We also compared the control effects of different treatments, including chemical fungicides and treatment with multiple strains and single strains in combination or individually, against RSRD. The objective of this study was to find an effective and environmentally friendly control strategy to reduce the occurrence of RSRD and improve the rice yield.

Results: In pot experiments, the effect of B3 alone was better than that of fungicide or combined measures. The results showed that root colonization by B3 significantly reduced the incidence and disease index of RSRD by 41.0% and 53.8%, respectively. This was related to enhanced superoxide dismutase (SOD), peroxidase (POD), and polyphenol oxidase (PPO) activity, and to significantly upregulated expression levels of OsAOX, OsLOX, OsPAL, and OsPR10 in rice. Moreover, B3 improved the diversity of the bacterial community rather than the fungal community in the rice rhizosphere. It also led to a decrease in Fusarium proliferatum colonization and fumonisin content in the grain. Finally, root development was markedly promoted after B3 inoculation, and the yield improved by 48.60%. The result of field experiments showed that the incidence of RSRD and the fumonisin content were observably reduced in rice receiving B3, by 24.41% and 37.87%, respectively.

Conclusion: The endophytic fungus Phomopsis liquidambaris B3 may become an effective tool to relieve rice spikelet rot disease. © 2020 Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.11042DOI Listing
August 2021

A smartphone-combined ratiometric fluorescence probe for specifically and visibly detecting cephalexin.

Spectrochim Acta A Mol Biomol Spectrosc 2021 Mar 7;249:119310. Epub 2020 Dec 7.

College of Life Science, Nanjing Normal University, Nanjing 210023, PR China. Electronic address:

A smartphone-combined dual-emission ratiometric fluorescence probe for specifically and visibly detecting cephalexin was first designed. In the probe, blue-emitting fluorescent carbon dots (CDs) was synthesized and covered with a layer of silica spacer. Red-emitting fluorescent CdTe QDs (r-QDs) was grafted onto the silica nanospheres as an analytical probe. Then, the cephalexin antibody was covalent grafted to the ratio sensor to increase the selectivity. The ratio of fluorescence intensity (FL) of r-QDs and CDs was quenched with the increasing concentration of cephalexin. The detection method has good linear response in the range of 1-500 μM and the detection limit was 0.7 μM. Then portable device based on smartphone detection was constructed according to the color change under UV lamp. The detection image was obtained through the smartphone camera, and the color picker APP installed in the smartphone captured the RGB value of the image. In addition, this method was also used to determine the amount of cephalexin in milk samples with recovery of 94.1%-102.2%. These results showed that it was a portable, simple and visible method to detect cephalexin in food analysis and environmental monitoring.
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http://dx.doi.org/10.1016/j.saa.2020.119310DOI Listing
March 2021

The disruption of the MAPKK gene triggering the synthesis of flavonoids in endophytic fungus Phomopsis liquidambaris.

Biotechnol Lett 2021 Jan 31;43(1):119-132. Epub 2020 Oct 31.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, 210023, Jiangsu, China.

Flavonoids, which are mainly extracted from plants, are important antioxidants and play an important role in human diseases. However, the growing market demand is limited by low productivity and complex production processes. Herein, the flavonoids biosynthesis pathway of the endophytic fungus Phomopsis liquidambaris was revealed. The mitogen-activated protein kinase kinase (MAPKK) of the strain was disrupted using a newly constructed CRISPR-Cas9 system mediated by two gRNAs which was conducive to cause plasmid loss. The disruption of the MAPKK gene triggered the biosynthesis of flavonoids against stress and resulted in the precipitation of flavonoids from fermentation broth. Naringenin, kaempferol and quercetin were detected in fed-batch fermentation with yields of 5.65 mg/L, 1.96 mg/L and 2.37 mg/L from P. liquidambaris for dry cell weigh using the mixture of glucose and xylose and corn steep powder as carbon source and nitrogen source for 72 h, respectively. The biosynthesis of flavonoids was triggered by disruption of MAPKK gene in P. liquidambaris and the mutant could utilize xylose.
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http://dx.doi.org/10.1007/s10529-020-03042-5DOI Listing
January 2021

Endophytic bacteria promote the quality of Lyophyllum decastes by improving non-volatile taste components of mycelia.

Food Chem 2021 Jan 28;336:127672. Epub 2020 Jul 28.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China. Electronic address:

Endophytic bacteria are always related to the host different traits, including the secondary metabolites production. However, the effect and mechanism of endophytic bacteria in the mushrooms fruit body on mycelia are still not clear. In this study, we investigated the effect of endophytic bacterial metabolites on the quality of Lyophyllum decastes mycelia. Soluble sugars, starch, protein, free amino acids, 5'-Nucleotides, EUC, and organic acids contents of mycelia were analyzed. We found that endophytic bacterial metabolites significantly increased the contents of soluble sugars, starch, protein, free amino acids, organic acids, and EUC. The present study thus suggests that endophytic bacteria could promote the quality of Lyophyllum decastes by improving non-volatile taste components of mycelia.
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http://dx.doi.org/10.1016/j.foodchem.2020.127672DOI Listing
January 2021

Endophytic Fungus Alleviates Soil Sickness in Peanut Crops by Improving the Carbon Metabolism and Rhizosphere Bacterial Diversity.

Microb Ecol 2021 Jul 12;82(1):49-61. Epub 2020 Jul 12.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, 210023, China.

Endophytic fungi can profoundly affect host productivity, but the underlying mechanisms of these effects are only partly understood. As the most important regulators of plant-soil feedback, root exudates can easily cause soil sickness in continuous monoculture systems by reducing certain microbes in the rhizosphere. In this study, exudates from roots colonized by the endophytic fungus Phomopsis liquidambaris significantly increased rhizosphere bacterial abundance, soil respiration, microbial biomass and enzyme activities in a long-term continuously cropped peanut soil. Further analysis revealed that P. liquidambaris-colonized root exudates clearly altered the carbon metabolism and rhizosphere bacterial diversity, which were closely correlated with changes in soil chemical properties caused by the exudates from the colonized roots. Finally, a synthetic root exudate experiment further confirmed that the root exudates derived from P. liquidambaris colonization can indeed play an important role in promoting peanut growth. Therefore, these results show that this endophytic fungus could improve the carbon metabolism and rhizosphere bacterial community in long-term monoculture soils via exudates from colonized roots, which contribute to the alleviation of soil sickness.
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http://dx.doi.org/10.1007/s00248-020-01555-0DOI Listing
July 2021

Nitrogen fertilizer-regulated plant-fungi interaction is related to root invertase-induced hexose generation.

FEMS Microbiol Ecol 2020 08;96(8)

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Jiangsu Province, China.

The mechanisms underlying nitrogen (N)-regulated plant-fungi interactions are not well understood. N application modulates plant carbohydrate (C) sinks and is involved in the overall plant-fungal association. We hypothesized that N regulates plant-fungi interactions by influencing the carbohydrate metabolism. The mutualistic fungus Phomopsis liquidambaris was found to prioritize host hexose resources through in vitro culture assays and in planta inoculation. Rice-Ph. liquidambaris systems were exposed to N gradients ranging from N-deficient to N-abundant conditions to study whether and how the sugar composition was involved in the dynamics of N-mediated fungal colonization. We found that root soluble acid invertases were activated, resulting in increased hexose fluxes in inoculated roots. These fluxes positively influenced fungal colonization, especially under N-deficient conditions. Further experiments manipulating the carbohydrate composition and root invertase activity through sugar feeding, chemical treatments and the use of different soil types revealed that the external disturbance of root invertase could reduce endophytic colonization and eliminate endophyte-induced host benefits under N-deficient conditions. Collectively, these results suggest that the activation of root invertase is related to N deficiency-enhanced endophytic colonization via increased hexose generation. Certain combinations of farmland ecosystems with suitable N inputs could be implemented to maximize the benefits of plant-fungi associations.
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http://dx.doi.org/10.1093/femsec/fiaa139DOI Listing
August 2020

Mycelial network-mediated rhizobial dispersal enhances legume nodulation.

ISME J 2020 04 23;14(4):1015-1029. Epub 2020 Jan 23.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, Jiangsu, China.

The access of rhizobia to legume host is a prerequisite for nodulation. Rhizobia are poorly motile in soil, while filamentous fungi are known to grow extensively across soil pores. Since root exudates-driven bacterial chemotaxis cannot explain rhizobial long-distance dispersal, mycelia could constitute ideal dispersal networks to help rhizobial enrichment in the legume rhizosphere from bulk soil. Thus, we hypothesized that mycelia networks act as vectors that enable contact between rhizobia and legume and influence subsequent nodulation. By developing a soil microcosm system, we found that a facultatively biotrophic fungus, Phomopsis liquidambaris, helps rhizobial migration from bulk soil to the peanut (Arachis hypogaea) rhizosphere and, hence, triggers peanut-rhizobium nodulation but not seen in the absence of mycelia. Assays of dispersal modes suggested that cell proliferation and motility mediated rhizobial dispersal along mycelia, and fungal exudates might contribute to this process. Furthermore, transcriptomic analysis indicated that genes associated with the cell division, chemosensory system, flagellum biosynthesis, and motility were regulated by Ph. liquidambaris, thus accounting for the detected rhizobial dispersal along hyphae. Our results indicate that rhizobia use mycelia as dispersal networks that migrate to legume rhizosphere and trigger nodulation. This work highlights the importance of mycelial network-based bacterial dispersal in legume-rhizobium symbiosis.
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http://dx.doi.org/10.1038/s41396-020-0587-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7082348PMC
April 2020

The construction of CRISPR-Cas9 system for endophytic Phomopsis liquidambaris and its PmkkA-deficient mutant revealing the effect on rice.

Fungal Genet Biol 2020 03 22;136:103301. Epub 2019 Nov 22.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, No. 1 Wenyuan Road, Nanjing, Jiangsu 210023, China. Electronic address:

The endophytic fungus Phomopsis liquidambaris efficiently promotes the nitrogen metabolism and growth of host plants such as rice and peanut. However, a lack of genetic tools limits further research regarding the mechanisms of interaction between P. liquidambaris and its host plants. Herein, a CRISPR/Cas9 system for targeted gene disruption in this strain was first constructed and optimized. The knock-out efficiency increased to over 60% when the ku70 or ku80 gene (involved in nonhomologous end-joining, NHEJ) was disrupted. Furthermore, the CRISPR/Cas9 system was applied to disrupt the PmkkA gene, encoding a mitogen-activated protein kinase kinase (MAPKK) in the cell-wall integrity (CWI) MAPK pathway of the strain. The ΔPmkkA mutant strain induced higher reactive oxygen species (ROS) production, chitinase activity and glucanase activity in rice seedlings than wild-type P. liquidambaris (WT), resulting in growth inhibition and strong resistance on rice. These results suggested that the PmkkA gene is crucial during the interaction with rice and may play a role in inhibiting the immune system of host plants. The CRISPR-Cas9 system will be of great use for the study of the interaction between P. liquidambaris and its host plants.
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http://dx.doi.org/10.1016/j.fgb.2019.103301DOI Listing
March 2020

Remediation mechanism of endophytic fungus Phomopsis liquidambaris on phenanthrene in vivo.

Chemosphere 2020 Mar 5;243:125305. Epub 2019 Nov 5.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, 210023, China. Electronic address:

Phenanthrene can easily be absorbed into the plant from the soil and cannot be effectively degraded in it. Thus, it is greatly hazardous for food safety and human health. In our study, the biodegradability and remediation mechanism of endophytic fungus Phomopsis liquidambaris on phenanthrene in vivo of rice (Oryza sativa L.) was detected. The results showed that the fungus could successfully establish a symbiotic relationship with rice, thus had the potential to degrade phenanthrene absorbed into the plant. Changes of phenanthrene-degrading genes of fungus in the combined system were consistent with the trends of their corresponding enzymatic activities, and the phenanthrene-degrading enzyme activities and gene expression levels in roots of rice were higher than those in the shoot. Moreover, the combined system can enhance bioremediation by increasing root viability, chlorophyll content, and energy supply. The combined system had also significantly increased the PPO activity and SOD activity in shoot compared with the control treatment, while decreased the content of MDA when remediation in vivo. The study on the degradation mechanism of the combined system will help us to increase the practical application potential of endophyte to effectively repair contamination absorbed into plant seedlings.
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http://dx.doi.org/10.1016/j.chemosphere.2019.125305DOI Listing
March 2020

Endophyte-assisted phytoremediation: mechanisms and current application strategies for soil mixed pollutants.

Crit Rev Biotechnol 2020 Feb 27;40(1):31-45. Epub 2019 Oct 27.

College of Life Sciences, Nanjing Normal University, Nanjing, China.

Phytoremediation uses plants and associated microbes to remove pollutants from the environment and is considered a promising bioremediation method. Compared with well-described single contaminant treatments, the number of studies reporting phytoremediation of soil mixed pollutants has increased recently. Endophytes, including bacteria and fungi, exhibit beneficial traits for the promotion of plant growth, stress alleviation, and biodegradation. Moreover, endophytes either directly or indirectly assist host plants to survive high concentrations of organic and inorganic pollutants in the soil. Endophytic microorganisms can also regulate the plant metabolism in different ways, exhibiting a variety of physiological characteristics. This review summarizes the taxa and physiological properties of endophytic microorganisms that may participate in the detoxification of contaminant mixtures. Furthermore, potential biomolecules that may enhance endophyte mediated phytoremediation are discussed. The practical applications of pollutant-degrading endophytes and current strategies for applying this valuable bio-resource to soil phytoremediation are summarized.
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http://dx.doi.org/10.1080/07388551.2019.1675582DOI Listing
February 2020

Flowering-mediated root-fungus symbiosis loss is related to jasmonate-dependent root soluble sugar deprivation.

Plant Cell Environ 2019 12 16;42(12):3208-3226. Epub 2019 Aug 16.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, China.

The role of flowering in root-fungal symbiosis is not well understood. Because flowering and fungal symbionts are supported by carbohydrates, we hypothesized that flowering modulates root-beneficial fungal associations through alterations in carbohydrate metabolism and transport. We monitored fungal colonization and soluble sugars in the roots of Arabidopsis thaliana following inoculation with a mutualistic fungus Phomopsis liquidambari across different plant developmental stages. Jasmonate signalling of wild-type plants, sugar transport, and root invertase of wild-type and jasmonate-insensitive plants were exploited to assess whether and how jasmonate-dependent sugar dynamics are involved in flowering-mediated fungal colonization alterations. We found that flowering restricts root-fungal colonization and activates root jasmonate signalling upon fungal inoculation. Jasmonates reduce the constitutive and fungus-induced accumulation of root glucose and fructose at the flowering stage. Further experiments with sugar transport and metabolism mutant lines revealed that root glucose and fructose positively influence fungal colonization. Diurnal, jasmonate-dependent inhibitions of sugar transport and soluble invertase activity were identified as likely mechanisms for flowering-mediated root sugar depletion upon fungal inoculation. Collectively, our results reveal that flowering drives root-fungus cooperation loss, which is related to jasmonate-dependent root soluble sugar depletion. Limiting the spread of root-fungal colonization may direct more resources to flower development.
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http://dx.doi.org/10.1111/pce.13636DOI Listing
December 2019

Endophytic Fungus Drives Nodulation and N Fixation Attributable to Specific Root Exudates.

mBio 2019 07 16;10(4). Epub 2019 Jul 16.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, China

Endophytic fungi play important roles in the modification of ecosystem productivity; however, the underlying mechanisms are only partly understood. A 2-year field plot experiment verified that the endophytic fungus increased peanut ( L.) yields and significantly increased nodulation and N fixation regardless of whether N fertilizers were added. Root exudates collected from -colonized plants significantly improved nodulation and N fixation. Rhizosphere stimulation experiments further showed that colonized root exudates had significantly decreased soil nitrate (NO ) concentrations, with decreased abundance and diversity of ammonia oxidizing archaea (AOA). In contrast, the abundance and diversity of diazotrophs significantly increased, and most diazotrophs identified were peanut nodulation-related strains ( sp.). symbiosis increased the expression of phenolic and flavonoid synthesis-related genes, and the derived phenolics and flavonoids could effectively increase the chemotaxis, biofilm formation, and gene expression (nodulation-related biological processes) of the strain. Metabolic pattern analysis showed that phenolics and flavonoids are more likely to accumulate to higher levels in the rhizosphere soil of peanuts colonized with Finally, a synthetic root exudate experiment further confirmed the underlying mechanisms for the -induced improvement in nodulation and N fixation, i.e., that the specific root exudates derived from colonization decrease nitrate concentration and increase the population and biological activities of peanut nodulation-related species, which beneficially enhance peanut- interactions. Therefore, this study is the first to provide new insight into a positive relationship between an exotic endophytic fungus, crop nodulation, and N fixation increase. Endophytic fungi play an important role in balancing the ecosystem and boosting host growth; however, the underpinning mechanisms remain poorly understood. Here, we found that endophytic fungal colonization with significantly increased the productivity, nodulation, and N fixation of peanuts through the secretion of specific root exudates. We provide a reasonable mechanism explaining how promotes peanut nodulation and N fixation, whereby the specific root exudates produced by colonization decrease rhizosphere soil nitrate (NO3) and increase the population and biological activities of peanut-nodulating-related strains, which is beneficial to enhancing the peanut- symbiotic interaction. Our study provides reliable empirical evidence to show the mechanism of how an exotic endophytic fungus drives an increase in nodulation and N fixation, which will be helpful in erecting a resource-efficient and sustainable agricultural system.
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http://dx.doi.org/10.1128/mBio.00728-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6635524PMC
July 2019

Targeted Acquisition of f. sp. Toxin-Deficient Mutant and Its Effects on Watermelon Wilt.

J Agric Food Chem 2019 Aug 26;67(31):8536-8547. Epub 2019 Jul 26.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences , Nanjing Normal University , Nanjing , Jiangsu Province 210023 , China.

Watermelon wilt is a common soil-borne disease that has significantly affected its yield. In this study, fusaric acid-deficient mutant designated as ΔFUBT (mutated from f. sp. , FON) was obtained. The ΔFUBT mutant showed significant decrease in fusaric acid production but maintained wild-type characteristics, such as in vitro colony morphology, size, and conidiation. A field pot experiment demonstrated that ΔFUBT could successfully colonize the rhizosphere and the roots of watermelon, leading to significant reduction in FON colonization in the watermelon plant. In addition, ΔFUBT inoculation significantly improved the rhizosphere microenvironment and effectively increased the resistance in watermelon. This study demonstrated that a nonpathogenic mutant (ΔFUBT) could be developed as an effective microbial control agent to alleviate wilt disease in watermelon and increase its yield.
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http://dx.doi.org/10.1021/acs.jafc.9b02172DOI Listing
August 2019

Strategies for gene disruption and expression in filamentous fungi.

Appl Microbiol Biotechnol 2019 Aug 21;103(15):6041-6059. Epub 2019 Jun 21.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, 210023, Jiangsu Province, China.

Filamentous fungi can produce many valuable secondary metabolites; among these fungi, endophytic fungi play an ecological role in mutualistic symbiosis with plants, including promoting plant growth, disease resistance, and stress resistance. However, the biosynthesis of most secondary metabolites remains unclear, and knowledge of the interaction mechanisms between endophytes and plants is still limited, especially for some novel fungi, due to the lack of genetic manipulation tools for novel species. Herein, we review the newly discovered strategies of gene disruption, such as the CRISPR-Cas9 system, the site-specific recombination Cre/loxP system, and the I-SceI endonuclease-mediated system in filamentous fungi. Gene expression systems contain using integration of target genes into the genome, host-dependent expression cassette construction depending on the host, a host-independent, universal expression system independent of the host, and reporter-guided gene expression for filamentous fungi. Furthermore, the Newly CRISPRi, CRISPRa, and the selection markers were also discussed for gene disruption and gene expression were also discussed. These studies lay the foundation for the biosynthesis of secondary metabolites in these organisms and aid in understanding the ecological function of filamentous fungi.
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http://dx.doi.org/10.1007/s00253-019-09953-2DOI Listing
August 2019

Fungal endophyte Phomopsis liquidambari biodegrades soil resveratrol: a potential allelochemical in peanut monocropping systems.

J Sci Food Agric 2019 Oct 12;99(13):5899-5909. Epub 2019 Jul 12.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, China.

Background: Most allelochemicals are secondary products released from root excretions or plant residues that accumulate in continuous cropping systems and cause severe decline in peanut yield. Resveratrol is a plant-derived stilbene that is released from peanut residues and accumulates in the soil; however, its allelopathic effects on peanut production are overlooked. Effective management solutions need to be developed to relieve allelopathy caused by soil resveratrol. Here, the biodegradation of resveratrol by the fungal endophyte Phomopsis liquidambari was investigated in a mineral salt medium and a soil trial. Resveratrol and its metabolites (produced by degradation by P. liquidambari) were detected by high-performance liquid chromatography-mass spectrometry (HPLC-MS).

Results: Resveratrol released from peanut residues reached a maximum concentration of 0.18 μg g soil in litterbag experiments. Exogenous resveratrol inhibited peanut growth, nodule formation, and soil dehydrogenase activity, and reduced the soil microbial biomass carbon content and bacterial abundance, indicating an allelopathic role in peanut growth. More than 97% of the resveratrol was degraded within 72 and 168 h by P. liquidambari in pure culture and soil conditions, respectively. Resveratrol was first cleaved to 3,5-dihydroxybenzaldehyde and 4-hydroxybenzaldehyde, which were subsequently oxidized into 3,5-dihydroxybenzoic acid and 4-hydroxybenzoic acid, respectively. Fungal resveratrol cleavage oxygenase and the related gene expression were enhanced when P. liquidambari was induced by the resveratrol during the incubation.

Conclusion: Our results indicate that the practical application of the fungal endophyte P. liquidambari has strong potential for biodegrading soil resveratrol, which can cause allelopathy in peanut continuous cropping systems. © 2019 Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.9865DOI Listing
October 2019

Comparative Transcriptomics and Proteomics of in Response to Endophytic Fungus sp. AL12 Reveals Regulation in Plant Metabolism.

Front Microbiol 2019 28;10:1208. Epub 2019 May 28.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, China.

The fungal endophyte sp. AL12 can establish a beneficial association with the medicinal herb , and improve plant growth and sesquiterpenoids accumulation, which is termed "double promotion." Our previous studies have uncovered the underling primary mechanism based on some physiological evidences. However, a global understanding of gene or protein expression regulation in primary and secondary metabolism and related regulatory processes is still lacking. In this study, we employed transcriptomics and proteomics of sp. AL12-inoculated and sp. AL12-free plants to study the impact of endophyte inoculation at the transcriptional and translational levels. The results showed that plant genes involved in plant immunity and signaling were suppressed, similar to the plant response caused by some endophytic fungi and biotroph pathogen. The downregulated plant immunity may contribute to plant-endophyte beneficial interaction. Additionally, genes and proteins related to primary metabolism (carbon fixation, carbohydrate metabolism, and energy metabolism) tended to be upregulated after sp. AL12 inoculation, which was consistent with our previous physiological evidences. And, sp. AL12 upregulated genes involved in terpene skeleton biosynthesis, and upregulated genes annotated as β-farnesene synthase and β-caryophyllene synthase. Based on the above results, we proposed that endophyte-plant associations may improve production (biomass and sesquiterpenoids accumulation) by increasing the source (photosynthesis), expanding the sink (glycolysis and tricarboxylic acid cycle), and enhancing the metabolic flux (sesquiterpenoids biosynthesis pathway) in . And, this study will help to further clarify plant-endophyte interactions.
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http://dx.doi.org/10.3389/fmicb.2019.01208DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6546907PMC
May 2019

Enhanced nitrogen and phosphorus activation with an optimized bacterial community by endophytic fungus Phomopsis liquidambari in paddy soil.

Microbiol Res 2019 Apr 11;221:50-59. Epub 2019 Feb 11.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, Jiangsu Province, 210023, China. Electronic address:

The endophytic fungus Phomopsis liquidambari play a key role in habitat adaptation of rice (Oryza sativa L.) with potential multiple beneficial. However, our previous published work on this subject remains incomplete. Here, we performed a soil nutrient (nitrogen and phosphorus) transformation with related functional genes and elucidated how rhizosphere microbiota vary their response to P. liquidambari interaction throughout the plant's life cycle under field conditions by Illumina Miseq sequencing platforms in a nutrient-limited paddy soil. Our results showed that P. liquidambari symbiosis decreased the nitrogen and phosphorus loss by 24.59% and 17.46% per pot, respectively. Additionally, we suggest that the application of P. liquidambari altered the activation of soil nitrogen and phosphorus functional genes to accelerate nutrient turnover in the rice rhizosphere. High-throughput sequencing with co-occurrence network and species-related network analysis further revealed that P. liquidambari colonization influenced the patterns of microbiota shift in the rhizosphere, especially during the heading stages. This led to an optimized microbial community through the promotion and inhibition of indigenous soil microbes with a higher level of available nutrient supplies. Our study strongly proposes rice-P. liquidambari symbiosis as a useful candidate for improving N and P acquisition and utilization.
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http://dx.doi.org/10.1016/j.micres.2019.02.005DOI Listing
April 2019

Phomopsis liquidambari colonization promotes continuous cropping peanut growth by improving the rhizosphere microenvironment, nutrient uptake and disease incidence.

J Sci Food Agric 2019 Mar 31;99(4):1898-1907. Epub 2018 Oct 31.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, China.

Background: The continuous cropping of peanuts is a primary cause of yield and quality loss. Solutions to this problem should be therefore developed to ensure the sustainability of peanut production.

Results: In this study, colonization by the endophytic fungus Phomopsis liquidambari was detected, which led to significantly improved rhizosphere soil microenvironment, enhanced N, P and K assimilation and suppressed incidence of peanut disease. Statistical analysis demonstrated that the yield enhancement was significantly correlated with improvement of the rhizosphere soil microenvironment and the peanut's physiological status by P. liquidambari colonization. In addition, P. liquidambari colonization also significantly improved peanut quality.

Conclusion: Our results indicate that the practical application of the endophytic fungus P. liquidambari has a strong potential to alleviate the obstacles associated with continuous peanut cropping under field conditions. © 2018 Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.9385DOI Listing
March 2019

Endophytic Pseudomonas induces metabolic flux changes that enhance medicinal sesquiterpenoid accumulation in Atractylodes lancea.

Plant Physiol Biochem 2018 Sep 27;130:473-481. Epub 2018 Jul 27.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, 210023, Jiangsu, China. Electronic address:

The bacterial endophyte Pseudomonas fluorescens ALEB7B significantly enhances photosynthate accumulations in Atractylodes lancea. These carbohydrates are preferentially used by the host plant to synthesize secondary metabolites, rather than to increase plant biomass accumulation. Mechanisms underlying the allocation of endophyte-increased carbohydrate in different plant metabolic processes are largely unknown. We have studied how P. fluorescens ALEB7B enhances photosynthate accumulation and how bacterial elicitors regulate metabolic flux and increase medicinal sesquiterpenoid formation in A. lancea using the sterile tissue culture plantlets. P. fluorescens ALEB7B enhances plant photosynthate accumulation by synthesizing and secreting indole-3-acetic acid, which has been demonstrated using high-performance liquid chromatography analysis. The increased endogenous indole-3-acetic acid promotes plant root development and then assimilation. Increased carbohydrates provide the material basis for the formations of terpenoid hydrocarbon scaffolds, which has been proved using gas chromatography analysis. Further, protein and polysaccharide elicitors secreted by P. fluorescens ALEB7B have been separated and purified from the bacterial fermentation broth, which have been applied to A. lancea plantlets. Both elicitors can stimulate the conversions of terpenoid hydrocarbon scaffolds to oxygenous sesquiterpenoids, the active medicinal ingredients in A. lancea, by triggering the oxidative burst in planta. Moreover, this study separates an ABC transporter substrate-binding protein from protein elicitors secreted by P. fluorescens ALEB7B with an ÄKTA Prime Plus Purifier System and firstly shows that this protein is essential to induce oxygenous sesquiterpenoid accumulation in A. lancea. This study provides new perspectives for mechanisms of medicinal oxygenous terpenoid synthesis, which has important reference values to the cultivation of medicinal plants that have terpenoids as their active ingredients, such as Artemisia annua and Taxus chinensis.
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http://dx.doi.org/10.1016/j.plaphy.2018.07.016DOI Listing
September 2018

Mutualistic fungus Phomopsis liquidambari increases root aerenchyma formation through auxin-mediated ethylene accumulation in rice (Oryza sativa L.).

Plant Physiol Biochem 2018 Sep 18;130:367-376. Epub 2018 Jul 18.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, Jiangsu Province, 210023, China. Electronic address:

The fungal endophyte Phomopsis liquidambari can improve nitrification rates and alter the abundance and composition of ammonia-oxidizers in the soil rhizosphere of rice. Aerenchyma is related to oxygen transport efficiency and contributes to the enhanced rhizospheric nitrification under flooding conditions. However, whether and how P. liquidambari affects aerenchyma formation is largely unknown. We therefore conducted pot and hydroponic experiments to investigate the changes of aerenchyma area, ethylene and indole-3-acetic acid (IAA) levels in rice with or without P. liquidambari infection. Our results showed that the larger aerenchyma area in rice roots with P. liquidambari inoculation was associated with markedly up-regulated expression of genes related to aerenchyma formation. Meanwhile, P. liquidambari inoculation substantially elevated root porosity (POR) and radial oxygen loss (ROL), leading to the enhancement of oxidation-reduction potential (ORP) under pot condition. Besides, P. liquidambari significantly increased IAA and ethylene levels in rice by stimulating the expression of genes involved in auxin and ethylene biosyntheses. Furthermore, auxin that partly acting upstream of ethylene signalling played an essential role in P. liquidambari-promoted aerenchyma formation. These results verified the direct contribution of P. liquidambari in promoting aerenchyma formation via the accumulation of IAA and ethylene in rice roots, which provides a constructive suggestion for improving hypoxia tolerance through plant-endophyte interactions.
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http://dx.doi.org/10.1016/j.plaphy.2018.07.018DOI Listing
September 2018

Evidence for the Involvement of Auxin, Ethylene and ROS Signaling During Primary Root Inhibition of Arabidopsis by the Allelochemical Benzoic Acid.

Plant Cell Physiol 2018 Sep;59(9):1889-1904

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Jiangsu Province, China.

Allelopathy is mediated by plant-derived secondary metabolites (allelochemicals) which are released by donor plants and affect the growth and development of receptor plants. The plant root is the first organ which senses soil allelochemicals this results in the production of a shorter primary root. However, the mechanisms underlying this process remain elusive. Here, we report that a model allelochemical benzoic acid (BA) inhibited primary root elongation of Arabidopsis seedlings by reducing the sizes of both the meristem and elongation zones, and that auxin signaling affected this process. An increase in auxin level in the root tips was associated with increased expression of auxin biosynthesis genes and auxin polar transporter AUX1 and PIN2 genes under BA stress. Mutant analyses demonstrated that AUX1 and PIN2 rather than PIN1 were required for the inhibition of primary root elongation during BA exposure. Furthermore, BA stimulated ethylene evolution, whereas blocking BA-induced ethylene signaling with an ethylene biosynthesis inhibitor (Co2+), an ethylene perception antagonist (1-methylcyclopropene) or ethylene signaling mutant lines etr1-3 and ein3eil1 compromised BA-mediated inhibition of root elongation and up-regulation of auxin biosynthesis-related genes together with AUX1 and PIN2, indicating that ethylene signal was involved in auxin-mediated inhibition of primary root elongation during BA stress. Further analysis revealed that the BA-induced reactive oxygen species (ROS) burst contributed to BA-mediated root growth inhibition without affecting auxin and ethylene signals. Taken together, our results reveal that the allelochemical BA inhibits root elongation by increasing auxin accumulation via stimulation of auxin biosynthesis and AUX1/PIN2-mediated auxin transport via stimulation of ethylene production and an auxin/ethylene-independent ROS burst.
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http://dx.doi.org/10.1093/pcp/pcy107DOI Listing
September 2018

Bacterial Bioreporter-Based Mercury and Phenanthrene Assessment in Yangtze River Delta Soils of China.

J Environ Qual 2018 May;47(3):562-570

Genetically engineered bacterial whole-cell bioreporters were deployed to investigate bioavailable mercury (b-Hg) and phenanthrene (b-PHE). Characterized by high sensitivity and specificity in aqueous solutions, the bioreporter system could detect in amended soils the concentrations of b-Hg and b-PHE in the ranges of 19.6 to 111.6 and 21.5 to 110.9 μg kg, respectively. The sensitivity of the system allowed for the combined analysis of b-Hg and b-PHE from real environmental samples. Therefore, soil samples from three large refinery facilities were tested, and the results from the instrumental analysis strongly correlated with the ones obtained with the bioreporter method. Large-scale and fast screening of soil contamination across the Yangtze River Delta in Eastern China was conducted. More than 36% of the samples contained b-Hg, whereas the fractions of b-PHE were below the detection limit for all the samples. These results indicated a higher toxicity and more hazardous condition for Hg contamination than for PHE. Population densities and airborne 10-μm particulate matter (PM10) concentrations were used as parameters for comparison with the spatial distribution of the b-Hg and b-PHE fractions. The results revealed that the bioreporters could offer a rapid and cost-efficient method to test soil samples from contaminated areas and provide a screening tool for environmental risk assessment.
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http://dx.doi.org/10.2134/jeq2017.07.0286DOI Listing
May 2018

Auxin signalling of Arachis hypogaea activated by colonization of mutualistic fungus Phomopsis liquidambari enhances nodulation and N -fixation.

Plant Cell Environ 2018 09 15;41(9):2093-2108. Epub 2018 Apr 15.

Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Jiangsu Province, China.

Beneficial fungal and rhizobial symbioses share commonalities in phytohormones responses, especially in auxin signalling. Mutualistic fungus Phomopsis liquidambari effectively increases symbiotic efficiency of legume peanut (Arachis hypogaea L.) with another microsymbiont, bradyrhizobium, but the underlying mechanisms are not well understood. We quantified and manipulated the IAA accumulation in ternary P. liquidambari-peanut-bradyrhizobial interactions to uncover its role between distinct symbioses. We found that auxin signalling is both locally and systemically induced by the colonization of P. liquidambari with peanut and further confirmed by Arabidopsis harbouring auxin-responsive reporter, DR5:GUS, and that auxin action, including auxin transport, is required to maintain fungal symbiotic behaviours and beneficial traits of plant during the symbiosis. Complementation and action inhibition experiments reveal that auxin signalling is involved in P. liquidambari-mediated nodule development and N -fixation enhancement and symbiotic gene activation. Further analyses showed that blocking of auxin action compromised the P. liquidambari-induced nodule phenotype and physiology changes, including vascular bundle development, symbiosome and bacteroids density, and malate concentrations, while induced the accumulation of starch granules in P. liquidambari-inoculated nodules. Collectively, our study demonstrated that auxin signalling activated by P. liquidambari symbiosis is recruited by peanut for bradyrhizobial symbiosis via symbiotic signalling pathway activation and nodule carbon metabolism enhancement.
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http://dx.doi.org/10.1111/pce.13170DOI Listing
September 2018

Endophytism or saprophytism: Decoding the lifestyle transition of the generalist fungus Phomopsis liquidambari.

Microbiol Res 2018 Jan 16;206:99-112. Epub 2017 Oct 16.

Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, Jiangsu Key Laboratory for Microbes and Functional Genomics, College of Life Sciences, Nanjing Normal University, Nanjing, 210023, China. Electronic address:

Filamentous ascomycete Phomopsis sp. are common inhabitants of natural ecosystems and, as saprophytes, are largely responsible for the destructive decay of litterfall, promoting the carbon and nitrogen cycles. Phomopsis liquidambari B3 can establish mutualistic symbiosis with a broad spectrum of crop plants. Colonizing dynamics observations and a growth promotion assay of rice and Arabidopsis thaliana revealed that the B3 colonization strategy is host-adapted and resulted in different growth promotions influenced by N availability. However, the biochemical mechanisms and underlying genetics of the saprophyte transition to an endophyte are poorly understood. Here, the transcriptome features of generalist P. liquidambari and highlighted gene sets involved in the lifestyle transition from saprophytism to endophytism were reported. Most notable were genes for translation, ribosome biogenesis and MAPK signaling, several of which were only up-regulated in endophytic B3. Coordinated up-regulation of genes encoding enzymes involved in phenylalanine, tyrosine and tryptophan biosynthesis were preceded by secondary metabolite induction, which was encountered with host defense. Quantitative PCR validates the reliability of RNA-seq. Dissection at the molecular level facilitated a deeper understanding of P. liquidambari adaptation to hosts and the complex natural environment to play a role in sustainable agriculture and carbon and nitrogen cycles.
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http://dx.doi.org/10.1016/j.micres.2017.10.005DOI Listing
January 2018
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