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Dawn R D Bignell - One of the best experts on this subject based on the ideXlab platform.
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coronafacoyl Phytotoxin biosynthesis and evolution in the common scab pathogen streptomyces scabiei
Applied and Environmental Microbiology, 2017Co-Authors: Luke Bown, Fabrice Berrue, Joost T P Verhoeven, Suzanne C Dufour, Dawn R D BignellAbstract:Coronafacoyl Phytotoxins are an important family of plant toxins that are produced by several different phytopathogenic bacteria, including the gammaproteobacterium Pseudomonas syringae and the actinobacterium Streptomyces scabiei (formerly Streptomyces scabies). The Phytotoxins consist of coronafacic acid (CFA) linked via an amide bond to different amino acids or amino acid derivatives. Previous work suggested that S. scabiei and P. syringae use distinct biosynthetic pathways for producing CFA, which is subsequently linked to its amino acid partner to form the complete Phytotoxin. Here, we provide further evidence that the S. scabiei CFA biosynthetic pathway is novel by characterizing the role of CYP107AK1, a predicted cytochrome P450 that has no homologue in P. syringae Deletion of the CYP107AK1 gene abolished production of coronafacoyl-isoleucine (CFA-Ile), the primary coronafacoyl Phytotoxin produced by S. scabiei Structural elucidation of accumulated biosynthetic intermediates in the ΔCYP107AK1 mutant indicated that CYP107AK1 is required for introducing the oxygen atom that ultimately forms the carbonyl group in the CFA backbone. The CYP107AK1 gene along with two additional genes involved in CFA-Ile biosynthesis in S. scabiei were found to be associated with putative CFA biosynthetic genes in other actinobacteria but not in other organisms. Analysis of the overall genetic content and organization of known and putative CFA biosynthetic gene clusters, together with phylogenetic analysis of the core biosynthetic genes, indicates that horizontal gene transfer has played an important role in the dissemination of the gene cluster and that rearrangement, insertion, and/or deletion events have likely contributed to the divergent biosynthetic evolution of coronafacoyl Phytotoxins in bacteria.IMPORTANCE The ability of plants to defend themselves against invading pathogens relies on complex signaling pathways that are controlled by key phytohormones such as jasmonic acid (JA). Some phytopathogenic bacteria have evolved the ability to manipulate JA signaling in order to overcome host defenses by producing coronatine (COR), which functions as a potent JA mimic. COR and COR-like molecules, collectively referred to as coronafacoyl Phytotoxins, are produced by several different plant-pathogenic bacteria, and this study provides supporting evidence that different biosynthetic pathways are utilized by different bacteria for production of these Phytotoxins. In addition, our study provides a greater understanding of how coronafacoyl Phytotoxin biosynthesis may have evolved in phylogenetically distinct bacteria, and we demonstrate that production of these compounds may be more widespread than previously recognized and that their role for the producing organism may not be limited to host-pathogen interactions.
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isolation and characterization of plant pathogenic streptomyces species associated with common scab infected potato tubers in newfoundland
Phytopathology, 2016Co-Authors: Joanna K Fyans, Luke Bown, Dawn R D BignellAbstract:Potato common scab (CS) is an economically important crop disease that is caused by several members of the genus Streptomyces. In this study, we characterized the plant-pathogenic Streptomyces spp. associated with CS-infected potato tubers harvested in Newfoundland, Canada. A total of 17 pathogenic Streptomyces isolates were recovered from potato scab lesions, of which eight were determined to be most similar to the known CS pathogen S. europaeiscabiei. All eight S. europaeiscabiei isolates were found to produce the thaxtomin A Phytotoxin and to harbor the nec1 virulence gene, and most also carry the putative virulence gene tomA. The remaining isolates appear to be novel pathogenic species that do not produce thaxtomin A, and only two of these isolates were determined to harbor the nec1 or tomA genes. Of the non-thaxtomin-producing isolates, strain 11-1-2 was shown to exhibit a severe pathogenic phenotype against different plant hosts and to produce a novel, secreted phytotoxic substance. This is the first report documenting the plant-pathogenic Streptomyces spp. associated with CS disease in Newfoundland. Furthermore, our findings provide further evidence that Phytotoxins other than thaxtomin A may also contribute to the development of CS by Streptomyces spp.
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regulation of coronafacoyl Phytotoxin production by the pas luxr family regulator cfar in the common scab pathogen streptomyces scabies
PLOS ONE, 2015Co-Authors: Zhenlong Cheng, Luke Bown, Kapil Tahlan, Dawn R D BignellAbstract:Potato common scab is an economically important crop disease that is characterized by the formation of superficial, raised or pitted lesions on the potato tuber surface. The most widely distributed causative agent of the disease is Streptomyces scabies, which produces the phytotoxic secondary metabolite thaxtomin A that serves as a key virulence factor for the organism. Recently, it was demonstrated that S. scabies can also produce the phytotoxic secondary metabolite coronafacoyl-L-isoleucine (CFA-L-Ile) as well as other related metabolites in minor amounts. The expression of the biosynthetic genes for CFA-L-Ile production is dependent on a PAS-LuxR family transcriptional regulator, CfaR, which is encoded within the Phytotoxin biosynthetic gene cluster in S. scabies. In this study, we show that CfaR activates coronafacoyl Phytotoxin production by binding to a single site located immediately upstream of the putative -35 hexanucleotide box within the promoter region for the biosynthetic genes. The binding activity of CfaR was shown to require both the LuxR and PAS domains, the latter of which is involved in protein homodimer formation. We also show that CFA-L-Ile production is greatly enhanced in S. scabies by overexpression of both cfaR and a downstream co-transcribed gene, orf1. Our results provide important insight into the regulation of coronafacoyl Phytotoxin production, which is thought to contribute to the virulence phenotype of S. scabies. Furthermore, we provide evidence that CfaR is a novel member of the PAS-LuxR family of regulators, members of which are widely distributed among actinomycete bacteria.
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characterization of the coronatine like Phytotoxins produced by the common scab pathogen streptomyces scabies
Molecular Plant-microbe Interactions, 2015Co-Authors: Joanna K Fyans, Mead S Altowairish, Dawn R D BignellAbstract:Streptomyces scabies is an important causative agent of common scab disease of potato tubers and other root crops. The primary virulence factor produced by this pathogen is a phytotoxic secondary metabolite called thaxtomin A, which is essential for disease development. In addition, the genome of S. scabies harbors a virulence-associated biosynthetic gene cluster called the coronafacic acid (CFA)-like gene cluster, which was previously predicted to produce metabolites that resemble the Pseudomonas syringae coronatine (COR) Phytotoxin. COR consists of CFA linked to an ethylcyclopropyl amino acid called coronamic acid, which is derived from L-allo-isoleucine. Using a combination of genetic and chemical analyses, we show that the S. scabies CFA-like gene cluster is responsible for producing CFA-L-isoleucine as the major product as well as other minor COR-like metabolites. Production of the metabolites was shown to require the cfl gene, which is located within the CFA-like gene cluster and encodes an enzyme i...
Luke Bown - One of the best experts on this subject based on the ideXlab platform.
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coronafacoyl Phytotoxin biosynthesis and evolution in the common scab pathogen streptomyces scabiei
Applied and Environmental Microbiology, 2017Co-Authors: Luke Bown, Fabrice Berrue, Joost T P Verhoeven, Suzanne C Dufour, Dawn R D BignellAbstract:Coronafacoyl Phytotoxins are an important family of plant toxins that are produced by several different phytopathogenic bacteria, including the gammaproteobacterium Pseudomonas syringae and the actinobacterium Streptomyces scabiei (formerly Streptomyces scabies). The Phytotoxins consist of coronafacic acid (CFA) linked via an amide bond to different amino acids or amino acid derivatives. Previous work suggested that S. scabiei and P. syringae use distinct biosynthetic pathways for producing CFA, which is subsequently linked to its amino acid partner to form the complete Phytotoxin. Here, we provide further evidence that the S. scabiei CFA biosynthetic pathway is novel by characterizing the role of CYP107AK1, a predicted cytochrome P450 that has no homologue in P. syringae Deletion of the CYP107AK1 gene abolished production of coronafacoyl-isoleucine (CFA-Ile), the primary coronafacoyl Phytotoxin produced by S. scabiei Structural elucidation of accumulated biosynthetic intermediates in the ΔCYP107AK1 mutant indicated that CYP107AK1 is required for introducing the oxygen atom that ultimately forms the carbonyl group in the CFA backbone. The CYP107AK1 gene along with two additional genes involved in CFA-Ile biosynthesis in S. scabiei were found to be associated with putative CFA biosynthetic genes in other actinobacteria but not in other organisms. Analysis of the overall genetic content and organization of known and putative CFA biosynthetic gene clusters, together with phylogenetic analysis of the core biosynthetic genes, indicates that horizontal gene transfer has played an important role in the dissemination of the gene cluster and that rearrangement, insertion, and/or deletion events have likely contributed to the divergent biosynthetic evolution of coronafacoyl Phytotoxins in bacteria.IMPORTANCE The ability of plants to defend themselves against invading pathogens relies on complex signaling pathways that are controlled by key phytohormones such as jasmonic acid (JA). Some phytopathogenic bacteria have evolved the ability to manipulate JA signaling in order to overcome host defenses by producing coronatine (COR), which functions as a potent JA mimic. COR and COR-like molecules, collectively referred to as coronafacoyl Phytotoxins, are produced by several different plant-pathogenic bacteria, and this study provides supporting evidence that different biosynthetic pathways are utilized by different bacteria for production of these Phytotoxins. In addition, our study provides a greater understanding of how coronafacoyl Phytotoxin biosynthesis may have evolved in phylogenetically distinct bacteria, and we demonstrate that production of these compounds may be more widespread than previously recognized and that their role for the producing organism may not be limited to host-pathogen interactions.
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isolation and characterization of plant pathogenic streptomyces species associated with common scab infected potato tubers in newfoundland
Phytopathology, 2016Co-Authors: Joanna K Fyans, Luke Bown, Dawn R D BignellAbstract:Potato common scab (CS) is an economically important crop disease that is caused by several members of the genus Streptomyces. In this study, we characterized the plant-pathogenic Streptomyces spp. associated with CS-infected potato tubers harvested in Newfoundland, Canada. A total of 17 pathogenic Streptomyces isolates were recovered from potato scab lesions, of which eight were determined to be most similar to the known CS pathogen S. europaeiscabiei. All eight S. europaeiscabiei isolates were found to produce the thaxtomin A Phytotoxin and to harbor the nec1 virulence gene, and most also carry the putative virulence gene tomA. The remaining isolates appear to be novel pathogenic species that do not produce thaxtomin A, and only two of these isolates were determined to harbor the nec1 or tomA genes. Of the non-thaxtomin-producing isolates, strain 11-1-2 was shown to exhibit a severe pathogenic phenotype against different plant hosts and to produce a novel, secreted phytotoxic substance. This is the first report documenting the plant-pathogenic Streptomyces spp. associated with CS disease in Newfoundland. Furthermore, our findings provide further evidence that Phytotoxins other than thaxtomin A may also contribute to the development of CS by Streptomyces spp.
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regulation of coronafacoyl Phytotoxin production by the pas luxr family regulator cfar in the common scab pathogen streptomyces scabies
PLOS ONE, 2015Co-Authors: Zhenlong Cheng, Luke Bown, Kapil Tahlan, Dawn R D BignellAbstract:Potato common scab is an economically important crop disease that is characterized by the formation of superficial, raised or pitted lesions on the potato tuber surface. The most widely distributed causative agent of the disease is Streptomyces scabies, which produces the phytotoxic secondary metabolite thaxtomin A that serves as a key virulence factor for the organism. Recently, it was demonstrated that S. scabies can also produce the phytotoxic secondary metabolite coronafacoyl-L-isoleucine (CFA-L-Ile) as well as other related metabolites in minor amounts. The expression of the biosynthetic genes for CFA-L-Ile production is dependent on a PAS-LuxR family transcriptional regulator, CfaR, which is encoded within the Phytotoxin biosynthetic gene cluster in S. scabies. In this study, we show that CfaR activates coronafacoyl Phytotoxin production by binding to a single site located immediately upstream of the putative -35 hexanucleotide box within the promoter region for the biosynthetic genes. The binding activity of CfaR was shown to require both the LuxR and PAS domains, the latter of which is involved in protein homodimer formation. We also show that CFA-L-Ile production is greatly enhanced in S. scabies by overexpression of both cfaR and a downstream co-transcribed gene, orf1. Our results provide important insight into the regulation of coronafacoyl Phytotoxin production, which is thought to contribute to the virulence phenotype of S. scabies. Furthermore, we provide evidence that CfaR is a novel member of the PAS-LuxR family of regulators, members of which are widely distributed among actinomycete bacteria.
Joanna K Fyans - One of the best experts on this subject based on the ideXlab platform.
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isolation and characterization of plant pathogenic streptomyces species associated with common scab infected potato tubers in newfoundland
Phytopathology, 2016Co-Authors: Joanna K Fyans, Luke Bown, Dawn R D BignellAbstract:Potato common scab (CS) is an economically important crop disease that is caused by several members of the genus Streptomyces. In this study, we characterized the plant-pathogenic Streptomyces spp. associated with CS-infected potato tubers harvested in Newfoundland, Canada. A total of 17 pathogenic Streptomyces isolates were recovered from potato scab lesions, of which eight were determined to be most similar to the known CS pathogen S. europaeiscabiei. All eight S. europaeiscabiei isolates were found to produce the thaxtomin A Phytotoxin and to harbor the nec1 virulence gene, and most also carry the putative virulence gene tomA. The remaining isolates appear to be novel pathogenic species that do not produce thaxtomin A, and only two of these isolates were determined to harbor the nec1 or tomA genes. Of the non-thaxtomin-producing isolates, strain 11-1-2 was shown to exhibit a severe pathogenic phenotype against different plant hosts and to produce a novel, secreted phytotoxic substance. This is the first report documenting the plant-pathogenic Streptomyces spp. associated with CS disease in Newfoundland. Furthermore, our findings provide further evidence that Phytotoxins other than thaxtomin A may also contribute to the development of CS by Streptomyces spp.
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characterization of the coronatine like Phytotoxins produced by the common scab pathogen streptomyces scabies
Molecular Plant-microbe Interactions, 2015Co-Authors: Joanna K Fyans, Mead S Altowairish, Dawn R D BignellAbstract:Streptomyces scabies is an important causative agent of common scab disease of potato tubers and other root crops. The primary virulence factor produced by this pathogen is a phytotoxic secondary metabolite called thaxtomin A, which is essential for disease development. In addition, the genome of S. scabies harbors a virulence-associated biosynthetic gene cluster called the coronafacic acid (CFA)-like gene cluster, which was previously predicted to produce metabolites that resemble the Pseudomonas syringae coronatine (COR) Phytotoxin. COR consists of CFA linked to an ethylcyclopropyl amino acid called coronamic acid, which is derived from L-allo-isoleucine. Using a combination of genetic and chemical analyses, we show that the S. scabies CFA-like gene cluster is responsible for producing CFA-L-isoleucine as the major product as well as other minor COR-like metabolites. Production of the metabolites was shown to require the cfl gene, which is located within the CFA-like gene cluster and encodes an enzyme i...
Antonio Evidente - One of the best experts on this subject based on the ideXlab platform.
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further secondary metabolites produced by the fungus pyricularia grisea isolated from buffelgrass cenchrus ciliaris
Chirality, 2020Co-Authors: Marco Masi, Susan E Meyer, Suzette Clement, Ernesto Santoro, Patrizia Scafato, Stefano Superchi, Antonio EvidenteAbstract:The fungal pathogen Pyricularia grisea has been studied to evaluate its production of Phytotoxins for the biocontrol of the buffelgrass (Cenchrus ciliaris L.) weed. A first investigation allowed to isolate several new and known phytotoxic metabolites. However, the further investigation on the organic extract obtained from the fungus liquid culture showed the presence of other metabolites possibly contributing to its phytotoxicity. Thus, four known metabolites were isolated and identified by spectroscopic (nuclear magnetic resonance [NMR] and high-resolution electrospray ionization mass spectrometry [HRESIMS]) methods as dihydropyriculol (1), epi-dihydropyriculol (2), 3-methoxy-6,8-dihydroxy-3-methyl-3,4-dihydroisocoumarin (3), and (R)-mevalonolactone (4). The absolute configuration of 1-3 was determined for the first time by a computational analysis of their electronic circular dichroism (ECD) spectra. When the isolated compounds were bioassayed at a concentration of 5 × 10-3 M in a buffelgrass coleoptile and radicle elongation test no toxicity was detected. On the contrary, compounds 1 and 3 showed a significant stimulating effect of radical elongation. Furthermore, the difference in growth stimulation between 1 and its epimer 2 highlights the tight relationship between absolute configuration and biological activity of these fungal metabolites.
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Diploquinones A and B, Two New Phytotoxic Tetrasubstituted 1,4-Naphthoquinones from Diplodia mutila, a Causal Agent of Grapevine Trunk Disease
2018Co-Authors: Pierluigi Reveglia, Marco Masi, Alessio Cimmino, Sandra Savocchia, Regina Billones-baaijens, Antonio EvidenteAbstract:Two new phytotoxic tetrasubstituted 1,4-naphthoquinones, named diploquinones A and B, were isolated together with vanillic acid from Diplodia mutila (DAR78993), a grapevine pathogen involved in Botryosphaeria dieback in Australia. Diploquinones A and B were characterized as 6,7-dihydroxy-2-methoxy-5-methylnaphthalene-1,4-dione and 3,5,7-trihydroxy-2-methoxynaphthalene-1,4-dione using spectroscopic methods (essentially 1D and 2D 1H and 13C NMR and HR ESIMS). The already known vanillic acid was isolated for the first time as fungal Phytotoxin and as metabolite of D. mutila. The three compounds were assayed on detached grapevine leaves (Vitis vinifera cv. Shiraz) at concentrations of 10–3 M and 2.5 × 10–3 M. Vanillic acid showed the highest phytotoxic effect on grapevine leaves irrespective of the tested concentration, while diploquinones A and B showed varying degrees of toxicity
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cochliotoxin a dihydropyranopyran 4 5 dione and its analogues produced by cochliobolus australiensis display phytotoxic activity against buffelgrass cenchrus ciliaris
Journal of Natural Products, 2017Co-Authors: Marco Masi, Susan E Meyer, Suzette Clement, Alessio Cimmino, Massimo Cristofaro, Antonio EvidenteAbstract:Buffelgrass (Pennisetum ciliare or Cenchrus ciliaris) is a perennial grass that has become highly invasive in the Sonoran Desert of southern Arizona. In the search for novel control strategies against this weed, strains of the foliar fungal pathogen Cochliobolus australiensis from buffelgrass have been screened for their ability to produce phytotoxic metabolites that could potentially be used as natural herbicides in an integrated pest management strategy. A new Phytotoxin, named cochliotoxin, was isolated from liquid culture of this fungus together with radicinin, radicinol, and their 3-epimers. Cochliotoxin was characterized, essentially by spectroscopic methods, as 3-hydroxy-2-methyl-7-(3-methyloxiranyl)-2,3-dihydropyrano[4,3-b]pyran-4,5-dione. Its relative stereochemistry was assigned by 1H NMR techniques, while the absolute configuration (2S,3S) was determined applying the advanced Mosher’s method by esterification of its hydroxy group at C-3. When bioassayed in a buffelgrass coleoptile elongation te...
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Drazepinone, a trisubstituted tetrahydronaphthofuroazepinone with herbicidal activity produced by Drechslera siccans
Phytochemistry, 2005Co-Authors: Antonio Evidente, Anna Andolfi, Maurizio Vurro, Maria Chiara Zonno, Mariano Fracchiolla, Andrea MottaAbstract:Abstract When grown in a minimal-defined medium, a strain of Drechslera siccans , a pathogenic fungus isolated from seeds of Lolium perenne , produced phytotoxic metabolites. This strain is one of the best toxin producers among several grass pathogenic fungal strains collected and tested to find Phytotoxins to be used as natural herbicides of monocot weeds. From the culture filtrates of D. siccans , we isolated a new phytotoxic trisubstituted naphthofuroazepinone, named drazepinone, and characterised it as a 3,5,12a-trimethyl-2,5,5a,12a-tetrahydro-1 H -naphtho[2′,3′:4,5]furo[2,3- b ]azepin-2-one. Assayed at 2 μg μl −1 solution the novel metabolite proved to have broad-spectrum herbicidal properties, without antibacterial and antifungal activities, and low zootoxic activity. Its original chemical structure and the interesting biological properties make drazepinone a potential natural herbicide.
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Sphaeropsidone and episphaeropsidone, phytotoxic dimedone methyl ethers produced by Sphaeropsis sapinea f. sp. cupressi grown in liquid culture
'Elsevier BV', 1998Co-Authors: Antonio Evidente, Lorenzo Sparapano, Olga Fierro, Giovanni Bruno, Federico Giordano, Andrea MottaAbstract:Two phytotoxic dimedone methyl ethers, named sphaeropsidone and episphaeropsidone, were isolated from Sphaeropsis sapinea f sp. cupressi, a phytopathogenic fungus causing a canker disease of Italian cypress (Cupressus sempervirens L.). The same fungus produced the sphaeropsidins A, B and C, which are three Phytotoxins recently chemically characterized as pimarane diterpenes. Sphaeropsidone and episphaeropsidone were characterized, using essentially spectroscopic methods, as two new phytotoxic disubstituted 7-oxabicyclo[4.1.0]hept-3-en-2-ones, which are epimers at C-5. Assayed on severed twigs of cypress, sphaeropsidone caused browning and necrosis on Cupressus macrocarpa, no symptoms on C. sempervirens and chlorosis on C. arizonica. Episphaeropsidone caused necrosis on C. macrocarpa, browning and necrosis on C. sempervirens and necrosis on C. arizonica. On the non-host plant tomato, both Phytotoxins caused wilting. In a microbial assay, both compounds showed an inhibitory effect on the growth of five fungal species tested. The growth of Vertcillium dahliae was enhanced by both dimedone methyl ethers. (C) 1998 Elsevier Science Ltd. All rights reserved
Aziz Aziz - One of the best experts on this subject based on the ideXlab platform.
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Image_1_Bacillus subtilis PTA-271 Counteracts Botryosphaeria Dieback in Grapevine, Triggering Immune Responses and Detoxification of Fungal Phytotoxins.JPEG
2019Co-Authors: Patricia Trotel-aziz, Eliane Abou-mansour, Barbara Courteaux, Fanja Rabenoelina, Christophe Clément, Florence Fontaine, Aziz AzizAbstract:Plant pathogens have evolved various strategies to enter hosts and cause diseases. Particularly Neofusicoccum parvum, a member of Botryosphaeria dieback consortium, can secrete the Phytotoxins (-)-terremutin and (R)-mellein during grapevine colonization. The contribution of Phytotoxins to Botryosphaeria dieback symptoms still remains unknown. Moreover, there are currently no efficient control strategies of this disease, and agro-environmental concerns have raised increasing interest in biocontrol strategies to limit disease spread in vineyards, especially by using some promising beneficial bacteria. Here, we first examined in planta the biocontrol capacity of Bacillus subtilis PTA-271 against N. parvum Np-Bt67 strain producing both (-)-terremutin and (R)-mellein. We then focused on the direct effects of PTA-271 on pathogen growth and the fate of pure Phytotoxins, and explored the capacity of PTA-271 to induce or prime grapevine immunity upon pathogen infection or Phytotoxin exposure. Results provided evidence that PTA-271 significantly protects grapevine cuttings against N. parvum and significantly primes the expression of PR2 (encoding a β-1,3-glucanase) and NCED2 (9-cis-epoxycarotenoid dioxygenase involved in abscisic acid biosynthesis) genes upon pathogen challenge. Using in vitro plantlets, we also showed that PTA-271 triggers the expression of salicylic acid- and jasmonic acid-responsive genes, including GST1 (encoding a glutathione-S-transferase) involved in detoxification process. However, in PTA-271-pretreated plantlets, exogenous (-)-terremutin strongly lowered the expression of most of upregulated genes, except GST1. Data also indicated that PTA-271 can detoxify both (-)-terremutin and (R)-mellein and antagonize N. parvum under in vitro conditions. Our findings highlight (-)-terremutin and (R)-mellein as key aggressive molecules produced by N. parvum that may weaken grapevine immunity to promote Botryosphaeria dieback symptoms. However, PTA-271 can efficiently attenuate Botryosphaeria dieback by enhancing some host immune responses and detoxifying both Phytotoxins produced by N. parvum.
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Bacillus subtilis PTA-271 counteracts Botryosphaeria dieback in grapevine, triggering immune responses and detoxification of fungal Phytotoxins
2019Co-Authors: Trotel-aziz Patricia, Abou-mansour Eliane, Courteaux Barbara, Rabenoelina Fanja, Clément Christophe, Fontaine Florence, Aziz AzizAbstract:Plant pathogens have evolved various strategies to enter hosts and cause diseases. Particularly Neofusicoccum parvum, a member of Botryosphaeria dieback consortium, can secrete the Phytotoxins (-)-terremutin and (R)-mellein during grapevine colonization. The contribution of Phytotoxins to Botryosphaeria dieback symptoms still remains unknown. Moreover, there are currently no efficient control strategies of this disease, and agro-environmental concerns have raised increasing interest in biocontrol strategies to limit disease spread in vineyards, especially by using some promising beneficial bacteria. Here, we first examined in planta the biocontrol capacity of Bacillus subtilis PTA-271 against N. parvum Np-Bt67 strain producing both (-)- terremutin and (R)-mellein. We then focused on the direct effects of PTA-271 on pathogen growth and the fate of pure Phytotoxins, and explored the capacity of PTA- 271 to induce or prime grapevine immunity upon pathogen infection or Phytotoxin exposure. Results provided evidence that PTA-271 significantly protects grapevine cuttings against N. parvum and significantly primes the expression of PR2 (encoding a β-1,3-glucanase) and NCED2 (9-cis-epoxycarotenoid dioxygenase involved in abscisic acid biosynthesis) genes upon pathogen challenge. Using in vitro plantlets, we also showed that PTA-271 triggers the expression of salicylic acid- and jasmonic acid-responsive genes, including GST1 (encoding a glutathione-S-transferase) involved in detoxification process. However, in PTA-271-pretreated plantlets, exogenous (-)-terremutin strongly lowered the expression of most of upregulated genes, except GST1. Data also indicated that PTA-271 can detoxify both (-)- terremutin and (R)-mellein and antagonize N. parvum under in vitro conditions. Our findings highlight (-)-terremutin and (R)-mellein as key aggressive molecules produced by N. parvum that may weaken grapevine immunity to promote Botryosphaeria dieback symptoms. However, PTA-271 can efficiently attenuate Botryosphaeria dieback by enhancing some host immune responses and detoxifying both Phytotoxins produced by N. parvum
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Table_1_Bacillus subtilis PTA-271 Counteracts Botryosphaeria Dieback in Grapevine, Triggering Immune Responses and Detoxification of Fungal Phytotoxins.docx
2019Co-Authors: Patricia Trotel-aziz, Eliane Abou-mansour, Barbara Courteaux, Fanja Rabenoelina, Christophe Clément, Florence Fontaine, Aziz AzizAbstract:Plant pathogens have evolved various strategies to enter hosts and cause diseases. Particularly Neofusicoccum parvum, a member of Botryosphaeria dieback consortium, can secrete the Phytotoxins (-)-terremutin and (R)-mellein during grapevine colonization. The contribution of Phytotoxins to Botryosphaeria dieback symptoms still remains unknown. Moreover, there are currently no efficient control strategies of this disease, and agro-environmental concerns have raised increasing interest in biocontrol strategies to limit disease spread in vineyards, especially by using some promising beneficial bacteria. Here, we first examined in planta the biocontrol capacity of Bacillus subtilis PTA-271 against N. parvum Np-Bt67 strain producing both (-)-terremutin and (R)-mellein. We then focused on the direct effects of PTA-271 on pathogen growth and the fate of pure Phytotoxins, and explored the capacity of PTA-271 to induce or prime grapevine immunity upon pathogen infection or Phytotoxin exposure. Results provided evidence that PTA-271 significantly protects grapevine cuttings against N. parvum and significantly primes the expression of PR2 (encoding a β-1,3-glucanase) and NCED2 (9-cis-epoxycarotenoid dioxygenase involved in abscisic acid biosynthesis) genes upon pathogen challenge. Using in vitro plantlets, we also showed that PTA-271 triggers the expression of salicylic acid- and jasmonic acid-responsive genes, including GST1 (encoding a glutathione-S-transferase) involved in detoxification process. However, in PTA-271-pretreated plantlets, exogenous (-)-terremutin strongly lowered the expression of most of upregulated genes, except GST1. Data also indicated that PTA-271 can detoxify both (-)-terremutin and (R)-mellein and antagonize N. parvum under in vitro conditions. Our findings highlight (-)-terremutin and (R)-mellein as key aggressive molecules produced by N. parvum that may weaken grapevine immunity to promote Botryosphaeria dieback symptoms. However, PTA-271 can efficiently attenuate Botryosphaeria dieback by enhancing some host immune responses and detoxifying both Phytotoxins produced by N. parvum.