Phytotoxins produced by plant pathogenic <i>Streptomyces</i>
 species

Bignell, Dawn R. D.; Fyans, Joanna K; Cheng, Zhongjun

doi:10.1111/jam.12369

Cited by 62 publications

(46 citation statements)

References 82 publications

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“…One of the best studied plant-pathogenic species is Streptomyces scabies (syn. S. scabiei), which causes common scab disease of potato (Bignell et al, 2014;Loria et al, 2006). The main symptom associated with this disease is the formation of superficial, raised or deep-pitted lesions on the tuber surface, and these lesions reduce the market value of affected potatoes, leading to economic losses for potato growers (Dees and Wanner, 2012).…”

Section: Introductionmentioning

confidence: 99%

TxtH is a key component of the thaxtomin biosynthetic machinery in the potato common scab pathogen Streptomyces scabies

Jing-yu

Adekunle

et al. 2019

Molecular Plant Pathology

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Summary 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.

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Section: Introductionmentioning

confidence: 99%

TxtH is a key component of the thaxtomin biosynthetic machinery in the potato common scab pathogen Streptomyces scabies

Jing-yu

Adekunle

et al. 2019

Molecular Plant Pathology

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“…ThxA is a nitrated diketopiperazine. Its biosynthesis requires two non-ribosomal peptide synthetases encoded by txtA and txtB, a P450 monooxygenase (TxtC), a nitric oxide synthase (TxtD) and a novel cytochrome P450 (TxtE) (Bignell et al, 2014b). TxtD generates nitric oxide (NO) from L-arginine (Kers et al, 2004) and TxtE catalyses direct regiospecific nitration, producing 4-NO 2 -Ltryptophan (Barry et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Genetic background affects pathogenicity island function and pathogen emergence in Streptomyces

Zhang

Jiang

Ding

et al. 2018

Molecular Plant Pathology

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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.

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“…88,89 A biosynthetic pathway resembling that of CFA (12) in P. syringae has been previously identied in the common scab potato pathogen Streptomyces scabies. 90,91 The genus Streptomyces includes many different species that are well known for their ability to produce a wide array of secondary metabolites. Only a small number of Streptomyces spp.…”

Section: Microbial Phytohormonesmentioning

confidence: 99%

Microbial small molecules – weapons of plant subversion

et al. 2018

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Covering: up to 2018 Plants live in close association with a myriad of microbes that are generally harmless. However, the minority of microbes that are pathogens can severely impact crop quality and yield, thereby endangering food security. By contrast, beneficial microbes provide plants with important services, such as enhanced nutrient uptake and protection against pests and diseases. Like pathogens, beneficial microbes can modulate host immunity to efficiently colonize the nutrient-rich niches within and around the roots and aerial tissues of a plant, a phenomenon mirroring the establishment of commensal microbes in the human gut. Numerous ingenious mechanisms have been described by which pathogenic and beneficial microbes in the plant microbiome communicate with their host, including the delivery of immune-suppressive effector proteins and the production of phytohormones, toxins and other bioactive molecules. Plants signal to their associated microbes via exudation of photosynthetically fixed carbon sources, quorum-sensing mimicry molecules and selective secondary metabolites such as strigolactones and flavonoids. Molecular communication thus forms an integral part of the establishment of both beneficial and pathogenic plant-microbe relations. Here, we review the current knowledge on microbe-derived small molecules that can act as signalling compounds to stimulate plant growth and health by beneficial microbes on the one hand, but also as weapons for plant invasion by pathogens on the other. As an exemplary case, we used comparative genomics to assess the small molecule biosynthetic capabilities of the Pseudomonas genus; a genus rich in both plant pathogenic and beneficial microbes. We highlight the biosynthetic potential of individual microbial genomes and the population at large, providing evidence for the hypothesis that the distinction between detrimental and beneficial microbes is increasingly fading. Knowledge on the biosynthesis and molecular activity of microbial small molecules will aid in the development of successful biological agents boosting crop resiliency in a sustainable manner and could also provide scientific routes to pathogen inhibition or eradication.

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Phytotoxins produced by plant pathogenic Streptomyces species

Cited by 62 publications

References 82 publications

TxtH is a key component of the thaxtomin biosynthetic machinery in the potato common scab pathogen Streptomyces scabies

TxtH is a key component of the thaxtomin biosynthetic machinery in the potato common scab pathogen Streptomyces scabies

Genetic background affects pathogenicity island function and pathogen emergence in Streptomyces

Microbial small molecules – weapons of plant subversion

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