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Yuting Li Jingyu Liu Damilola Adekunle Luke Bown Kapil Tahlan Dawn R.D. Bignell 《Molecular Plant Pathology》2019,20(10):1379-1393
Streptomyces scabies causes potato common scab disease, which reduces the quality and market value of affected tubers. The predominant pathogenicity determinant produced by S. scabies is the thaxtomin A phytotoxin, which is essential for common scab disease development. Production of thaxtomin A involves the nonribosomal peptide synthetases (NRPSs) TxtA and TxtB, both of which contain an adenylation (A-) domain for selecting and activating the appropriate amino acid during thaxtomin biosynthesis. The genome of S. scabies 87.22 contains three small MbtH-like protein (MLP)-coding genes, one of which (txtH) is present in the thaxtomin biosynthesis gene cluster. MLP family members are typically required for the proper folding of NRPS A-domains and/or stimulating their activities. This study investigated the importance of TxtH during thaxtomin biosynthesis in S. scabies. Biochemical studies showed that TxtH is required for promoting the soluble expression of both the TxtA and TxtB A-domains in Escherichia coli, and amino acid residues essential for this activity were identified. Deletion of txtH in S. scabies significantly reduced thaxtomin A production, and deletion of one of the two additional MLP homologues in S. scabies completely abolished production. Engineered expression of all three S. scabies MLPs could restore thaxtomin A production in a triple MLP-deficient strain, while engineered expression of MLPs from other Streptomyces spp. could not. Furthermore, the constructed MLP mutants were reduced in virulence compared to wild-type S. scabies. The results of our study confirm that TxtH plays a key role in thaxtomin A biosynthesis and plant pathogenicity in S. scabies. 相似文献
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Selection and Characterization of Microorganisms Utilizing Thaxtomin A, a Phytotoxin Produced by Streptomyces scabies 总被引:1,自引:0,他引:1 下载免费PDF全文
Thaxtomin A is the main phytotoxin produced by Streptomyces scabies, a causal agent of potato scab. Thaxtomin A is a yellow compound composed of 4-nitroindol-3-yl-containing 2,5-dioxopiperazine. A collection of nonpathogenic streptomycetes isolated from potato tubers and microorganisms recovered from a thaxtomin A solution were examined for the ability to grow in the presence of thaxtomin A as a sole carbon or nitrogen source. Three bacterial isolates and two fungal isolates grew in thaxtomin A-containing media. Growth of these organisms resulted in decreases in the optical densities at 400 nm of culture supernatants and in 10% reductions in the thaxtomin A concentration. The fungal isolates were identified as a Penicillium sp. isolate and a Trichoderma sp. isolate. One bacterial isolate was associated with the species Ralstonia pickettii, and the two other bacterial isolates were identified as Streptomyces sp. strains. The sequences of the 16S rRNA genes were determined in order to compare thaxtomin A-utilizing actinomycetes to the pathogenic organism S. scabies and other Streptomyces species. The nucleotide sequences of the γ variable regions of the 16S ribosomal DNA of both thaxtomin A-utilizing actinomycetes were identical to the sequence of Streptomyces mirabilis ATCC 27447. When inoculated onto potato tubers, the three thaxtomin A-utilizing bacteria protected growing plants against common scab, but the fungal isolates did not have any protective effect. 相似文献
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Genetic background affects pathogenicity island function and pathogen emergence in Streptomyces 下载免费PDF全文
With few exceptions, thaxtomin A (ThxA), a nitrated diketopiperazine, is the pathogenicity determinant for plant‐pathogenic Streptomyces species. In Streptomyces scabiei (syn. S. scabies), the ThxA biosynthetic cluster is located within a 177‐kb mobile pathogenicity island (PAI), called the toxicogenic region (TR). In S. turgidiscabies, the ThxA biosynthetic cluster is located within a 674‐kb pathogenicity island (PAIst). The emergence of new plant pathogens occurs in this genus, but not frequently. This raises the question of whether the mobilization of these pathogenicity regions, through mating, is widespread and whether TR and PAIst can confer plant pathogenicity. We showed that ThxA biosynthetic clusters on TR and PAIst were transferred into strains from five non‐pathogenic Streptomyces species through mating with S. scabiei and S. turgidiscabies. However, not all of the transconjugants produced ThxA and exhibited the virulence phenotype, indicating that the genetic background of the recipient strains affects the functionality of the ThxA biosynthetic cluster and therefore would be expected to affect the emergence of novel pathogenic Streptomyces species. Thxs have been patented as natural herbicides, but have yet to be commercialized. Our results also demonstrated the potential of the heterologous production of ThxA as a natural and biodegradable herbicide in non‐pathogenic Streptomyces species. 相似文献
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Dawn R. D. Bignell José C. Huguet-Tapia Madhumita V. Joshi Gregg S. Pettis Rosemary Loria 《Antonie van Leeuwenhoek》2010,98(2):179-194
Plant pathogenicity is rare in the genus Streptomyces, with only a dozen or so species possessing this trait out of the more than 900 species described. Nevertheless, such species
have had a significant impact on agricultural economies throughout the world due to their ability to cause important crop
diseases such as potato common scab, which is characterized by lesions that form on the potato tuber surface. All pathogenic
species that cause common scab produce a family of phytotoxins called the thaxtomins, which function as cellulose synthesis
inhibitors. In addition, the nec1 and tomA genes are conserved in several pathogenic streptomycetes, the former of which is predicted to function in the suppression
of plant defense responses. Streptomyces scabies is the oldest plant pathogen described and has a world-wide distribution, whereas species such as S. turgidiscabies and S. acidiscabies are believed to be newly emergent pathogens found in more limited geographical locations. The genome sequence of S. scabies 87-22 was recently completed, and comparative genomic analyses with other sequenced microbial pathogens have revealed the
presence of additional genes that may play a role in plant pathogenicity, an idea that is supported by functional analysis
of one such putative virulence locus. In addition, the availability of multiple genome sequences for both pathogenic and nonpathogenic
streptomycetes has provided an opportunity for comparative genomic analyses to identify the Streptomyces pathogenome. Such genomic analyses will contribute to the fundamental understanding of the mechanisms and evolution of plant
pathogenicity and plant-microbe biology within this genus. 相似文献
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Contribution of the β‐glucosidase BglC to the onset of the pathogenic lifestyle of Streptomyces scabies 下载免费PDF全文
Samuel Jourdan Isolde M. Francis Benoit Deflandre Elodie Tenconi Jennifer Riley Sören Planckaert Pierre Tocquin Loïc Martinet Bart Devreese Sébastien Rigali 《Molecular Plant Pathology》2018,19(6):1480-1490
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Several Streptomyces species cause plant diseases, including S. scabies, S. acidiscabies and S. turgidiscabies, which produce common scab of potato and similar diseases of root crops. These species produce thaxtomins, dipeptide phytotoxins
that are responsible for disease symptoms. Thaxtomins are produced in vivo on diseased potato tissue and in vitro in oat-based
culture media, but the regulation of thaxtomin biosynthesis is not understood. S. acidiscabies was grown in a variety of media to assess the impact of medium components on thaxtomin A (ThxA) production. ThxA biosynthesis
was not correlated with bacterial biomass, nor was it stimulated by α-solanine or α-chaconine, the two most prevalent potato
glycoalkaloids. ThxA production was stimulated by oat bran broth, even after exhaustive extraction, suggesting that specific
carbohydrates may influence ThxA biosynthesis. Oat bran contains high levels of xylans and glucans, and both of these carbohydrates,
as well as xylans from wheat and tamarind, stimulated ThxA production, but not to the same extent as oat bran. Starches and
simple sugars did not induce ThxA production. The data indicate that complex carbohydrates may act as environmental signals
to plant pathogenic Streptomyces, allowing production of thaxtomin and enabling bacteria to colonize its host. 相似文献
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el-Sayed ES 《Folia microbiologica》2000,45(5):415-422
A total of nine isolates of streptomycetes were isolated from scab lesions on potato tubers. Five of nine isolates were pathogenic
on potato minitubers. Four of the pathogenic isolates produced thaxtomin A (ThxA) in infected tuber tissues. The lesion surface
areas inducing ThxA were highest in treatment of the minitubers with an extract of OMB inoculated with S-66 and S-67, intermediate
with that inoculated with S-64 and lowest with S-63. The pathogenic isolates were identified by gray aerial mycelia, melanin
pigment productivity, the type of spore chain morphology and carbon utilization asS. scabies strains S-63, S-64 and S-68, andS. acidiscabies strains S-66 and S-67. Strains S-63 and S-64 produced 0.65 and 1.60 mg ThxA per L of OMB, respectively, strains S-66 and
S-67 producing similar amounts,viz. 2.36 and 2.10 mg/L, respectively. The optimal temperature for production (by both species) was 28 °C. Production of ThxA
byS. scabies strain S-64 andS. acidiscabies strain S-66 was suppressed at least 50-fold at 0.5 and 0.3 % of glucose, respectively. Fructose enhanced the production by
both species. 相似文献
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Binu Mani Tripathi Rajeev Kaushik Priyanka Kumari Anil Kumar Saxena Dilip Kumar Arora 《World journal of microbiology & biotechnology》2011,27(7):1603-1613
Irrigation of farm field with water mixed with pulp and paper mill effluent from Century pulp and paper mill in Uttrakhand
state of India for over last 25 years in succession increased streptomycetes population (120 × 105) compared to the fresh water irrigated fields (48 × 103 in WIF). Denaturing gradient gel electrophoresis, amplified ribosomal DNA restriction analysis, 16S rRNA gene sequencing,
BIOLOG™ substrate usage, production of extracellular enzymes (xylanase and cellulase) and plant growth promoting attributes
were applied to monitor changes in genetic and metabolic diversity of streptomycetes. Significant variation was observed for
production of extracellular enzymes, Indolic compounds, siderophore and P-solubilisation among isolates. Metabolic substrate
usage of Streptomyces isolates was evaluated using the BIOLOG™ GP2 plates and unique carbon substrate usage profiles were observed. Based on 16S
rRNA gene sequencing, the isolates were identified as Streptomyces variabilis, Streptomyces spp. S. glaucescens, S. viridochromogenes,
S. cinnabarinus, S. aburaviensis, S. viridis,
S. xylophagus, S. macrosporeus, S. thermocarboxydus, and S. albogriseolus. The diversity index parameters like Shannon index, reciprocal of Simpson’s index (1/D), and Pielou index of evenness based on ARDRA revealed that streptomycetes community in effluent irrigated field (EIF) was
more diverse. DGGE profiles of Streptomyces specific 16S rRNA gene fragments (16S-DGGE) amplified directly from soil samples were highly similar in both soils. 相似文献
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马铃薯疮痂病(potato scab)是世界范围内广泛存在的土传细菌性病害,难以防治。植物毒素thaxtomins由疮痂病链霉菌(Streptomyces scabies)次级代谢产生,是马铃薯疮痂病的主要致病原因,对马铃薯等作物产业造成严重危害。鉴于疮痂病链霉菌在农业上的重要作用,其中thaxtomins生物合成过程和分子调控得到越来越多的关注,并取得了较好的进展。本文综述了thaxtomins的结构特征、生物合成与异源表达,并重点介绍了疮痂病链霉菌中thaxtomins生物合成的分子调控机制等方面的研究进展,有利于深入认知疮痂病链霉菌次级代谢调控网络,为未来开发新型马铃薯疮痂病的防治策略提供理论指导。 相似文献
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Qing Wang Margherita Sacco Ezio Ricca Carmine T. Lago Maurilio DeFelice Joseph M. Calvo 《Molecular microbiology》1993,7(6):883-891
Lrp, a major regulatory protein in Escherichia coli, controls the expression of numerous operons, including ilvlH. Lrp binds to six sites upstream of ilvlH, and Lrp binding is required for ilvlH expression. We show here that an Lrp-like protein is also present in Salmonella typhimurium. This protein can bind both E. coli and S. typhimurium ilvlH DNA, as can E. coli Lrp. Methidiumpropyl-EDTA footprinting studies were performed with purified E. coli Lrp and S. typhimurium ilvlH DNA. Six binding sites were defined, three of them being similar to corresponding sites in E. coli, and three being organized differently. A consensus derived from six S. typhimurium sites is compatible with that derived from a similar analysis of E. coli sequences. 相似文献
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Sylvain Lerat Amadou H. Babana Mohamed El Oirdi Abdelbassed El Hadrami Fouad Daayf Nathalie Beaudoin Kamal Bouarab Carole Beaulieu 《Plant cell reports》2009,28(12):1895-1903
Streptomyces scabiei is the predominant causal agent of common scab of potato in North America. The virulence of common scab-causing streptomycetes
relies on their capacity to synthesize thaxtomins. In this study, the effects of S. scabiei infection and of thaxtomin A, the main toxin produced by S. scabiei, were tested for the elicitation of plant defense molecules in the model plants tobacco (Nicotiana tabacum) and Arabidopsis thaliana. Tobacco leaves infected with spores of S. scabiei strain EF-35 or infiltrated with purified thaxtomin A produced a blue fluorescent compound that was not detected in leaves
infiltrated with spores of a S. scabiei mutant deficient in thaxtomin A biosynthesis. Thin layer chromatography and high performance liquid chromatography identified
this fluorescent compound as scopoletin, a plant defense phytoalexin. Arabidopsis seedlings grown in liquid medium also excreted
scopoletin as a reaction to S. scabiei and thaxtomin A. The effects of the presence of scopoletin on S. scabiei were also investigated. The phytoalexin scopoletin caused a slight reduction of bacterial growth and a severe decrease of
thaxtomin A production. Scopoletin was shown to inhibit thaxtomin A production by repression of a gene involved in the toxin
biosynthesis. 相似文献
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Ebru Ince Yilmaz Murat Yavuz Murat Kizil 《World journal of microbiology & biotechnology》2008,24(8):1461-1470
As part of a research program whose aim is to determine the diversity of streptomycetes in order to discover new bioactive
secondary metabolites, rhizosphere soils of three indigenous plants were analyzed. A total of 55 actinomycetes were isolated
using three different medium from the samples. The rhizospheric soil of the plant Aethionema dumanii gave the highest number of actinomycetes, i.e., 42% versus 27% and 31% for the soils from Salvia aytachii and Achillea ketenoglui, respectively. The AIA is the most favorable medium for the isolation of the actinomycetes from different rhizospheric soils.
16S rDNA sequence analysis revealed that while some isolates belong to different cluster groups such as Streptomyces lydicus, S. rochei, S. microflavus, S. griseoflavus, S. albidoflavus and S. violaceusniger, the majority of the sequences did not considerable clustered with the member of different Streptomyces groups. The in vitro antimicrobial activities of the crude organic and aqueous extracts of isolates were screened using a
disc diffusion assay against a panel of bacteria and C. albicans. A total of 22 isolates showed antimicrobial activity. The antibacterial action of the extracts is more pronounced on Gram-positive
than on Gram-negative bacteria in most cases. About 18% of the actinomycetes showed also antifungal activity. Study of the
influence of two different culture media on production of bioactive molecules showed that the higher antimicrobial activity
was obtained in M2 when compared to TSB. The results from this study provide evidence that the streptomycetes in the rhizosphere
soils could be promising sources for antimicrobial bioactive agents. 相似文献
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Designing a crop rotation strategy to manage Streptomyces scabies causing potato scab in north India
Common scab of potato caused by various species in the genus Streptomyces has assumed serious proportions in certain potato-growing regions of North India. Although it does not have significant effect on tuber yield, it downgrades quality and reduces marketability. Being soil-borne, this disease is often difficult to manage. Therefore, the present studies were conducted to evaluate different potato-based crop rotations prevalent in north India as a part of a strategy to manage Streptomyces scabies population in scab sick fields. Our results showed that S. scabies population in soil can be effectively reduced either by keeping the field fallow after potato or by including mungbean or sunhemp as green manure, in a single year cropping sequence over a period of four years. Three crop rotations, viz. fallow–rice–potato, mungbean–rice–potato and sunhemp–rice–potato, showed maximum decrease in the population of S. scabies in soil resulting in reduced scab severity. The mungbean- and sunhemp-based crop rotations also enhanced rhizospheric soil microflora especially fluorescent pseudomonads and Trichoderma spp. 相似文献
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