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Yang ZY, Dai YC, Mo YQ, Wang JL, Ma L, Zhao PJ, Huang Y, Wang RB, Li W, Al-Rejaie SS, Liu JJ, Cao Y, Mo MH. Exploring the nematicidal mechanisms and control efficiencies of oxalic acid producing Aspergillus tubingensis WF01 against root-knot nematodes. Front Microbiol 2024; 15:1424758. [PMID: 39040900 PMCID: PMC11260745 DOI: 10.3389/fmicb.2024.1424758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2024] [Accepted: 06/20/2024] [Indexed: 07/24/2024] Open
Abstract
Background and aims Root-knot nematodes (RKN; Meloidogyne spp.) are among the highly prevalent and significantly detrimental pathogens that cause severe economic and yield losses in crops. Currently, control of RKN primarily relies on the application of chemical nematicides but it has environmental and public health concerns, which open new doors for alternative methods in the form of biological control. Methods In this study, we investigated the nematicidal and attractive activities of an endophytic strain WF01 against Meloidogyne incognita in concentration-dependent experiments. The active nematicidal metabolite was extracted in the WF01 crude extract through the Sephadex column, and its structure was identified by nuclear magnetic resonance and mass spectrometry data. Results The strain WF01 was identified as Aspergillus tubingensis based on morphological and molecular characteristics. The nematicidal and attractive metabolite of A. tubingensis WF01 was identified as oxalic acid (OA), which showed solid nematicidal activity against M. incognita, having LC50 of 27.48 μg ml-1. The Nsy-1 of AWC and Odr-7 of AWA were the primary neuron genes for Caenorhabditis elegans to detect OA. Under greenhouse, WF01 broth and 200 μg ml-1 OA could effectively suppress the disease caused by M. incognita on tomatoes respectively with control efficiency (CE) of 62.5% and 70.83%, and promote plant growth. In the field, WF01-WP and 8% OA-WP formulations showed moderate CEs of 51.25%-61.47% against RKN in tomato and tobacco. The combined application of WF01 and OA resulted in excellent CEs of 66.83% and 69.34% toward RKN in tomato and tobacco, respectively. Furthermore, the application of WF01 broth or OA significantly suppressed the infection of J2s in tomatoes by upregulating the expression levels of the genes (PAL, C4H, HCT, and F5H) related to lignin synthesis, and strengthened root lignification. Conclusion Altogether, our results demonstrated that A. tubingensis WF01 exhibited multiple weapons to control RKN mediated by producing OA to lure and kill RKN in a concentration-dependent manner and strengthen root lignification. This fungus could serve as an environmental bio-nematicide for managing the diseases caused by RKN.
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Affiliation(s)
- Zhong-Yan Yang
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming, China
| | - Yuan-Chen Dai
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming, China
| | - Yuan-Qi Mo
- Institute of Crop Variety Resources, Guizhou Academy of Agricultural Sciences, Guiyang, China
| | - Jia-Lun Wang
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming, China
| | - Li Ma
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming, China
| | - Pei-Ji Zhao
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming, China
| | - Ying Huang
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming, China
| | - Rui-Bin Wang
- Shandong Dianlu Biotechnology Co., Ltd., Feixian, China
| | - Wei Li
- Yunnan Boshiao Biotechnology Co., Ltd., Kunming, China
| | - Salim S. Al-Rejaie
- Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Jian-Jin Liu
- Pu’er Corporation of Yunnan Tobacco Corporation, Pu’er, China
| | - Yi Cao
- Guizhou Academy of Tobacco Agricultural Sciences, Guiyang, China
| | - Ming-He Mo
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming, China
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Patuwatha Withanage DBM, Luong LT. CHEMOTAXIS RESPONSE OF PHASMARHABDITIS CALIFORNICA (FAMILY: RHABDITIDAE) AND PRISTIONCHUS ENTOMOPHAGUS (FAMILY: NEODIPLOGASTERIDAE) TO THE MUCUS OF FOUR SLUG SPECIES. J Parasitol 2024; 110:59-65. [PMID: 38381123 DOI: 10.1645/23-61] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2024] Open
Abstract
The chemotaxis responses of soil nematodes have been well studied in bacteriophagic nematodes, plant-parasitic nematodes, entomopathogenic nematodes, and to a lesser extent malacopathogenic nematodes. Free-living stages of parasitic nematodes often use chemotaxis to locate hosts. In this study, we compared the chemotaxis profile of 2 slug-associated nematodes with overlapping host ranges. Phasmarhabditis californica is a facultative parasite that has been shown to express strain-dependent variation in chemoattraction profile. We tested 4 slug species to determine the attraction index of a Canadian strain of Ph. californica and a sympatric necromenic nematode, Pristionchus entomophagus. When tested against a control (distilled water), Ph. californica showed a clear (positive) attraction towards the mucus of slugs Ambigolimax valentianus, Arion rufus, and Arion fasciatus, but not Deroceras reticulatum. However, when given a choice between the mucus of D. reticulatum and Ar. fasciatus in a pairwise test, Ph. californica was strongly attracted to the former. Other pairwise comparisons did not reveal a clear preference for either slug species in the following pairs: D. reticulatum-Ar. rufus, Am. valentianus-Ar. rufus, D. reticulatum-Am. valentianus. The chemotaxis assay for Pr. entomophagus showed an attraction toward D. reticulatum and Ar. fasciatus (tested against controls); the attraction index for Am. valentianus was positive, but this was not statistically significant. In contrast, the attraction index for Ar. rufus was negative, suggesting possible repulsion to the mucus of this slug species. Given that Pr. entomophagus and Ph. californica occupy overlapping habitats, utilize similar hosts, and exhibit similar chemotaxis profiles, there is a potential for direct interaction between these 2 nematodes. Like other members of the genus Pristionchus, Pr. entomophagus may be able to prey upon the co-occurring Ph. californica, such antagonistic interactions could have important implications for the coexistence of these 2 species and Ph. californica in particular as a biocontrol agent against pestiferous slugs.
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Affiliation(s)
| | - Lien T Luong
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada
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Chen L, Wang Y, Zhu L, Min Y, Tian Y, Gong Y, Liu X. 3-(Methylthio)Propionic Acid from Bacillus thuringiensis Berliner Exhibits High Nematicidal Activity against the Root Knot Nematode Meloidogyne incognita (Kofoid and White) Chitwood. Int J Mol Sci 2024; 25:1708. [PMID: 38338986 PMCID: PMC10855422 DOI: 10.3390/ijms25031708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 01/22/2024] [Accepted: 01/28/2024] [Indexed: 02/12/2024] Open
Abstract
Root knot nematodes cause serious damage to global agricultural production annually. Given that traditional chemical fumigant nematicides are harmful to non-target organisms and the environment, the development of biocontrol strategies has attracted significant attention in recent years. In this study, it was found that the Bacillus thuringiensis Berliner strain NBIN-863 exhibits strong fumigant nematicidal activity and has a high attraction effect on Meloidogyne incognita (Kofoid and White) Chitwood. Four volatile organic compounds (VOCs) produced by NBIN-863 were identified using solid-phase microextraction and gas chromatography-mass spectrometry. The nematicidal activity of four VOCs, namely, N-methylformamide, propenamide, 3-(methylthio)propionic acid, and phenylmalonic acid, was detected. Among these compounds, 3-(methylthio)propionic acid exhibited the highest direct contact nematicidal activity against M. incognita, with an LC50 value of 6.27 μg/mL at 24 h. In the fumigant bioassay, the mortality rate of M. incognita treated with 1 mg/mL of 3-(methylthio)propionic acid for 24 h increased to 69.93%. Furthermore, 3-(methylthio)propionic acid also exhibited an inhibitory effect on the egg-hatching of M. incognita. Using chemotaxis assays, it was determined that 3-(methylthio)propionic acid was highly attractive to M. incognita. In pot experiments, the application of 3-(methylthio)propionic acid resulted in a reduction in gall numbers, decreasing the number of galls per gram of tomato root from 97.58 to 6.97. Additionally, the root length and plant height of the treated plants showed significant increases in comparison with the control group. The current study suggests that 3-(methylthio)propionic acid is a novel nematicidal virulence factor of B. thuringiensis. Our research provides evidence for the potential use of NBIN-863 or its VOCs in biocontrol against root knot nematodes.
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Affiliation(s)
| | | | | | | | | | | | - Xiaoyan Liu
- National Biopesticide Engineering Technology Research Centre, Hubei Biopesticide Engineering Research Centre, Hubei Academy of Agricultural Sciences, Wuhan 430064, China; (L.C.); (Y.W.); (L.Z.); (Y.M.); (Y.T.); (Y.G.)
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Zhao Y, Zhong C, Li Y, Zhou W, Huang X. Novel Genes and Key Signaling Molecules Involved in the Repulsive Response of Meloidogyne incognita against Biocontrol Bacteria. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2023; 71:19445-19456. [PMID: 38033160 DOI: 10.1021/acs.jafc.3c06074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2023]
Abstract
The ability of the model organism, Caenorhabditis elegans, to distinguish and escape from pathogenic bacteria has been extensively studied; however, studies on the repulsive response of Meloidogyne incognita are still in their infancy. We have recently demonstrated that biocontrol bacteria induce a repulsive response in M. incognita via two classical signaling pathways. The present study aimed to identify the novel genes and signaling molecules of M. incognita that potentially contribute to its defense reaction. Analysis of the transcriptome data of M. incognita with and without a repulsive response against Bacillus nematocida B16 obtained 15 candidate genes, of which the novel genes Minc3s01748g26034 and Minc3s02548g30585 were found to regulate the aversive behavior of M. incognita, and their functions were further validated. To further confirm the neuronal localization of the two novel genes in M. incognita, in situ hybridization was conducted using the digoxin-labeled probes of ten tag genes, and preferentially profiled the localization of amphid sensory neurons of M. incognita. Analysis of the overviewed neuronal map suggested that Minc3s01748g26034 and Minc3s02548g30585 functioned in ASK/ASI and CEPD/V neurons, respectively. During their interactions, the volatile compounds 3-methyl-butyric acid and 2-methyl-butyric acid produced by the biocontrol bacteria were predicted as the primary signaling molecules that promoted the repulsive behavior of M. incognita against biocontrol bacteria. The findings provided novel insights into the mechanisms underlying the repulsive response of M. incognita that are different from the canonical molecular pathways previously found in C. elegans and can aid in developing novel strategies for controlling root-knot nematodes.
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Affiliation(s)
- Yanli Zhao
- School of Medicine, and State Key Laboratory for Conservation and Utilization of Bio-Resources, Yunnan University, Kunming 650091, China
- Medicinal Plants Research Institute, Yunnan Academy of Agricultural Sciences, Kunming 650200, China
| | - Chidi Zhong
- School of Medicine, and State Key Laboratory for Conservation and Utilization of Bio-Resources, Yunnan University, Kunming 650091, China
| | - Yixin Li
- School of Medicine, and State Key Laboratory for Conservation and Utilization of Bio-Resources, Yunnan University, Kunming 650091, China
| | - Wenhui Zhou
- School of Medicine, and State Key Laboratory for Conservation and Utilization of Bio-Resources, Yunnan University, Kunming 650091, China
| | - Xiaowei Huang
- School of Medicine, and State Key Laboratory for Conservation and Utilization of Bio-Resources, Yunnan University, Kunming 650091, China
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Li B, Wang P, Yang L, Rang X, Zhou W, Liu Y. Chemotaxis of Meloidogyne incognita Response to Rhizosphere Bacteria. Microorganisms 2023; 11:2271. [PMID: 37764115 PMCID: PMC10536184 DOI: 10.3390/microorganisms11092271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 08/28/2023] [Accepted: 09/07/2023] [Indexed: 09/29/2023] Open
Abstract
Rhizosphere microorganisms and the volatile organic compounds (VOCs) produced by them take part in the regulation of the chemotaxis of nematodes. A total of 150 strains of rhizosphere bacteria were screened via a chemotaxis experiment with Meloidogyne incognita. Some isolates affected the behavior of the nematodes, including attraction, randomness, and repulsion. Volatile metabolites produced via the selected bacteria were associated with the chemotaxis of nematodes. M. incognita was highly attracted to decanal. In addition, dimethyl disulfide, 2,5-dimethylpyrazine, pentadecanoic acid, and palmitic acid were found to attract weakly M. incognita. Furthermore, the chemotaxis of M. incognita was tested in a pot experiment. The bacteria Bacillus sp. 1-50, Brevibacillus brevis 2-35, B. cereus 5-14, Chryseobacterium indologens 6-4, and VOC decanal could regulate the movement of M. incognita in the pot with or without plants. The results provide insights into rhizosphere microorganisms and their VOCs and how they regulate the chemotaxis of the nematodes.
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Affiliation(s)
| | | | | | | | | | - Yajun Liu
- State Laboratory for Conservation and Utilization of Bio-Resources, Yunnan University, Kunming 650091, China; (B.L.); (P.W.); (L.Y.); (X.R.); (W.Z.)
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Qu L, Dai K, Wang J, Cao L, Rao Z, Han R. Microbial landscapes of the rhizosphere soils and roots of Luffa cylindrica plant associated with Meloidogyne incognita. Front Microbiol 2023; 14:1168179. [PMID: 37303801 PMCID: PMC10247985 DOI: 10.3389/fmicb.2023.1168179] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 05/02/2023] [Indexed: 06/13/2023] Open
Abstract
Introduction The root-knot nematodes (RKN), especially Meloidogyne spp., are globally emerging harmful animals for many agricultural crops. Methods To explore microbial agents for biological control of these nematodes, the microbial communities of the rhizosphere soils and roots of sponge gourd (Luffa cylindrica) infected and non-infected by M. incognita nematodes, were investigated using culture-dependent and -independent methods. Results Thirty-two culturable bacterial and eight fungal species, along with 10,561 bacterial and 2,427 fungal operational taxonomic units (OTUs), were identified. Nine culturable bacterial species, 955 bacterial and 701 fungal OTUs were shared in both four groups. More culturable bacterial and fungal isolates were detected from the uninfected soils and roots than from the infected soils and roots (except no fungi detected from the uninfected roots), and among all samples, nine bacterial species (Arthrobacter sp., Bacillus sp., Burkholderia ambifaria, Enterobacteriaceae sp., Fictibacillus barbaricus, Microbacterium sp., Micrococcaceae sp., Rhizobiaceae sp., and Serratia sp.) were shared, with Arthrobacter sp. and Bacillus sp. being dominant. Pseudomonas nitroreducens was exclusively present in the infested soils, while Mammaliicoccus sciuri, Microbacterium azadirachtae, and Priestia sp., together with Mucor irregularis, Penicillium sp., P. commune, and Sordariomycetes sp. were found only in the uninfected soils. Cupriavidus metallidurans, Gordonia sp., Streptomyces viridobrunneus, and Terribacillus sp. were only in the uninfected roots while Aspergillus sp. only in infected roots. After M. incognita infestation, 319 bacterial OTUs (such as Chryseobacterium) and 171 fungal OTUs (such as Spizellomyces) were increased in rhizosphere soils, while 181 bacterial OTUs (such as Pasteuria) and 166 fungal OTUs (such as Exophiala) rose their abundance in plant roots. Meanwhile, much more decreased bacterial or fungal OTUs were identified from rhizosphere soils rather than from plant roots, exhibiting the protective effects of host plant on endophytes. Among the detected bacterial isolates, Streptomyces sp. TR27 was discovered to exhibit nematocidal activity, and B. amyloliquefaciens, Bacillus sp. P35, and M. azadirachtae to show repellent potentials for the second stage M. incognita juveniles, which can be used to develop RKN bio-control agents. Discussion These findings provided insights into the interactions among root-knot nematodes, host plants, and microorganisms, which will inspire explorations of novel nematicides.
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Oota M, Toyoda S, Kotake T, Wada N, Hashiguchi M, Akashi R, Ishikawa H, Favery B, Tsai AYL, Sawa S. Rhamnogalacturonan-I as a nematode chemoattractant from Lotus corniculatus L. super-growing root culture. FRONTIERS IN PLANT SCIENCE 2023; 13:1008725. [PMID: 36777533 PMCID: PMC9908596 DOI: 10.3389/fpls.2022.1008725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 12/29/2022] [Indexed: 06/18/2023]
Abstract
INTRODUCTION The soil houses a tremendous amount of micro-organisms, many of which are plant parasites and pathogens by feeding off plant roots for sustenance. Such root pathogens and parasites often rely on plant-secreted signaling molecules in the rhizosphere as host guidance cues. Here we describe the isolation and characterization of a chemoattractant of plant-parasitic root-knot nematodes (Meloidogyne incognita, RKN). METHODS The Super-growing Root (SR) culture, consisting of excised roots from the legume species Lotus corniculatus L., was found to strongly attract infective RKN juveniles and actively secrete chemoattractants into the liquid culture media. The chemo-attractant in the culture media supernatant was purified using hydrophobicity and anion exchange chromatography, and found to be enriched in carbohydrates. RESULTS Monosaccharide analyses suggest the chemo-attractant contains a wide array of sugars, but is enriched in arabinose, galactose and galacturonic acid. This purified chemoattractant was shown to contain pectin, specifically anti-rhamnogalacturonan-I and anti-arabinogalactan protein epitopes but not anti-homogalacturonan epitopes. More importantly, the arabinose and galactose sidechain groups were found to be essential for RKN-attracting activities. This chemo-attractant appears to be specific to M. incognita, as it wasn't effective in attracting other Meloidogyne species nor Caenorhabditis elegans. DISCUSSION This is the first report to identify the nematode attractant purified from root exudate of L corniculatus L. Our findings re-enforce pectic carbohydrates as important chemicals mediating micro-organism chemotaxis in the soil, and also highlight the unexpected utilities of the SR culture system in root pathogen research.
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Affiliation(s)
- Morihiro Oota
- Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, Japan
| | - Syuuto Toyoda
- Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, Japan
| | - Toshihisa Kotake
- Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Naoki Wada
- Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, Japan
| | | | - Ryo Akashi
- Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan
| | - Hayato Ishikawa
- Graduate School of Pharmaceutical Sciences, Chiba University, Chiba, Japan
| | - Bruno Favery
- Institut national de recherche pour l'agriculture, l'alimentation et l’environnement (INRAE), Université Côte d’Azur, CNRS, UMR 1355-7254 Institut Sophia Agrobiotech, Sophia Antipolis, France
- International Research Organization for Advanced Science and Technology, Kumamoto University, Kumamoto, Japan
| | - Allen Yi-Lun Tsai
- Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, Japan
- International Research Center for Agricultural and Environmental Biology, Kumamoto University, Kumamoto, Japan
| | - Shinichiro Sawa
- Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, Japan
- International Research Center for Agricultural and Environmental Biology, Kumamoto University, Kumamoto, Japan
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Liu R, Bao ZX, Li GH, Li CQ, Wang SL, Pan XR, Zhang KQ, Zhao PJ. Identification of Nematicidal Metabolites from Purpureocillium lavendulum. Microorganisms 2022; 10:microorganisms10071343. [PMID: 35889062 PMCID: PMC9325011 DOI: 10.3390/microorganisms10071343] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 06/30/2022] [Indexed: 02/01/2023] Open
Abstract
Purpureocillium lavendulum is a fungus with promising biocontrol applications. Here, transcriptome data acquired during the infection of Caenorhabditis elegans by Purpureocillium lavendulum showed that the transcription of metabolite synthesis genes was significantly up-regulated after 24 and 48 h of the fungus-nematode interaction. Then, the up-regulated transcription level of lipoxygenase was confirmed by RT-qPCR. The ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) analysis of differential metabolites revealed that this interaction resulted in the emergence of new metabolites or enhanced the production of metabolites. The results of the UPLC-MS analysis and the nematicidal assay were used to establish optimal culturing conditions under which 12 metabolites, including 3 hydroxylated C18 fatty acids and 9 steroids, were isolated and identified. Among them, hydroxylated fatty acids showed pronounced nematicidal activity against Meloidogyne incognita, and two degradative sterols showed chemotaxis activity to M. incognita. This study lays a foundation for the function of lipoxygenase and its products during the infection of Purpureocillium lavendulum.
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Pacheco PVM, Campos VP, Terra WC, Pedroso MP, de Paula LL, da Silva MSG, Monteiro TSA, de Freitas LG. Attraction and toxicity: Ways volatile organic compounds released by Pochonia chlamydosporia affect Meloidogyne incognita. Microbiol Res 2021; 255:126925. [PMID: 34823077 DOI: 10.1016/j.micres.2021.126925] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 11/18/2021] [Accepted: 11/19/2021] [Indexed: 10/19/2022]
Abstract
The production of volatile organic compounds (VOCs) acting against plant-parasitic nematodes has been characterized in different fungi; however, the role of VOCs emitted by Pochonia chlamydosporia in its trophic interaction with Meloidogyne incognita is still unknown. The aim of this study was to determine the effects of VOCs emitted by P. chlamydosporia strain Pc-10 on different stages (eggs, juveniles and female) of the M. incognita life cycle. Exposure of M. incognita eggs to VOCs released by Pc-10 resulted in a reduction up to 88 % in the nematode egg hatching, when compared to the control treatments. The VOCs emitted by Pc-10 also attracted M. incognita second-stage juveniles (J2). Through gas chromatography-mass spectrometry (GC-MS), three molecules were identified from the volatiles of the strain Pc-10, with 1,4-dimethoxybenzene being the major compound. In tests performed in vitro, 1,4-dimethoxybenzene at a concentration of 1050 μg mL-1 inhibited M. incognita egg hatching by up to 78.7 % compared to the control (0 μg mL-1) and attracted M. incognita J2 in all concentrations evaluated (1, 10, 100, 1000, and 10000 μg mL-1). The 1,4-dimethoxybenzene also showed fumigant and non-fumigant nematicidal activity against M. incognita. This compound presented lethal concentration for 50 % (LC50) of M. incognita J2 ranged from 132 to 136 μg mL-1. Fumigation with 1,4-dimethoxybenzene (100 mg) reduced egg hatching by up to 89 % and killed up to 86 % of M. incognita J2 compared to the control (0 μg mL-1). In vivo, the VOCs produced by Pc-10, 1,4-dimethoxybenzene, and the combination of both (Pc-10 + 1,4-dimethoxybenzene) attracted the M. incognita J2, compared to the respective controls. To the best of our knowledge, this is the first report on the attraction of M. incognita J2 and the toxicity to eggs and J2 by VOCs from P. chlamydosporia in which 1,4-dimethoxybenzene is the main toxin and attractant.
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Affiliation(s)
| | - Vicente Paulo Campos
- Federal University of Lavras (UFLA), Department of Plant Pathology, 37200-900, Lavras, MG, Brazil.
| | - Willian César Terra
- Federal University of Lavras (UFLA), Department of Plant Pathology, 37200-900, Lavras, MG, Brazil.
| | - Marcio Pozzobon Pedroso
- Federal University of Lavras (UFLA), Department of Chemistry, 37200-900, Lavras, MG, Brazil.
| | - Letícia Lopes de Paula
- Federal University of Lavras (UFLA), Department of Plant Pathology, 37200-900, Lavras, MG, Brazil.
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Bacterial Community Structure Dynamics in Meloidogyne incognita-Infected Roots and Its Role in Worm-Microbiome Interactions. mSphere 2020; 5:5/4/e00306-20. [PMID: 32669465 PMCID: PMC7364209 DOI: 10.1128/msphere.00306-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Plant parasitic nematodes such as Meloidogyne incognita have a complex life cycle, occurring sequentially in various niches of the root and rhizosphere. They are known to form a range of interactions with bacteria and other microorganisms that can affect their densities and virulence. High-throughput sequencing can reveal these interactions in high temporal and geographic resolutions, although thus far we have only scratched the surface. In this study, we have carried out a longitudinal sampling scheme, repeatedly collecting rhizosphere soil, roots, galls, and second-stage juveniles from 20 plants to provide a high-resolution view of bacterial succession in these niches, using 16S rRNA metabarcoding. Our findings indicate that a structured community develops in the root, in which gall communities diverge from root segments lacking a gall, and that this structure is maintained throughout the crop season. We describe the successional process leading toward this structure, which is driven by interactions with the nematode and later by an increase in bacteria often found in hypoxic and anaerobic environments. We present evidence that this structure may play a role in the nematode's chemotaxis toward uninfected root segments. Finally, we describe the J2 epibiotic microenvironment as ecologically deterministic, in part, due to the active bacterial attraction of second-stage juveniles.IMPORTANCE The study of high-resolution successional processes within tightly linked microniches is rare. Using the power and relatively low cost of metabarcoding, we describe the bacterial succession and community structure in roots infected with root-knot nematodes and in the nematodes themselves. We reveal separate successional processes in galls and adjacent non-gall root sections, which are driven by the nematode's life cycle and the progression of the crop season. With their relatively low genetic diversity, large geographic range, spatially complex life cycle, and the simplified agricultural ecosystems they occupy, root-knot nematodes can serve as a model organism for terrestrial holobiont ecology. This perspective can improve our understanding of the temporal and spatial aspects of biological control efficacy.
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