Convergent evolution of phytopathogenic pseudomonads onto hazelnut

Wang, Pauline W.; Morgan, Robyn L.; Scortichini, M.; Guttman, David S.

doi:10.1099/mic.0.2006/001545-0

Cited by 22 publications

(33 citation statements)

References 18 publications

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“…Very recently similar conclusions were reached by analyzing the single gene rpoD [82] or by a microarray approach [83]. However, when MLST was performed on a wide collection of P. syringae strains, belonging to the pathovars tomato , maculicola , apii , antirrhini , and avellanae , recombination was also found to strongly contribute to bacterial diversity [84]–[85]. Actually, this could be an expected result when examining closely related strains, which have more opportunities to recombine than distantly related bacteria, because of their DNA homology, overlapping host ranges, and ecological distribution.…”

Section: Discussionmentioning

confidence: 80%

High-Resolution Melting Analysis as a Powerful Tool to Discriminate and Genotype Pseudomonas savastanoi Pathovars and Strains

2012

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Pseudomonas savastanoi is a serious pathogen of Olive, Oleander, Ash, and several other Oleaceae. Its epiphytic or endophytic presence in asymptomatic plants is crucial for the spread of Olive and Oleander knot disease, as already ascertained for P. savastanoi pv. savastanoi (Psv) on Olive and for pv. nerii (Psn) on Oleander, while no information is available for pv. fraxini (Psf) on Ash. Nothing is known yet about the distribution on the different host plants and the real host range of these pathovars in nature, although cross-infections were observed following artificial inoculations. A multiplex Real-Time PCR assay was recently developed to simultaneously and quantitatively discriminate in vitro and in planta these P. savastanoi pathovars, for routine culture confirmation and for epidemiological and diagnostical studies. Here an innovative High-Resolution Melting Analysis (HRMA)-based assay was set up to unequivocally discriminate Psv, Psn and Psf, according to several single nucleotide polymorphisms found in their Type Three Secretion System clusters. The genetic distances among 56 P. savastanoi strains belonging to these pathovars were also evaluated, confirming and refining data previously obtained by fAFLP. To our knowledge, this is the first time that HRMA is applied to a bacterial plant pathogen, and one of the few multiplex HRMA-based assays developed so far. This protocol provides a rapid, sensitive, specific tool to differentiate and detect Psv, Psn and Psf strains, also in vivo and against other related bacteria, with lower costs than conventional multiplex Real-Time PCR. Its application is particularly suitable for sanitary certification programs for P. savastanoi, aimed at avoiding the spreading of this phytopathogen through asymptomatic plants.

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Section: Discussionmentioning

confidence: 80%

High-Resolution Melting Analysis as a Powerful Tool to Discriminate and Genotype Pseudomonas savastanoi Pathovars and Strains

2012

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“…This hypothesis cannot be ruled out also because in many areas of walnut cultivation in Southern Europe, Minor Asia and Central Asia the production is still largely based on the cultivation of J. regia ecotypes, which are well adapted to a typical environment [36], and Xaj could adapt accordingly. A geographic structure for phytopathogenic bacteria has been demonstrated for Pseudomonas avellanae [37,38] and Ralstonia solanacearum [12].…”

Section: Discussionmentioning

confidence: 99%

Multilocus Sequence Typing Reveals Relevant Genetic Variation and Different Evolutionary Dynamics among Strains of Xanthomonas arboricola pv. juglandis

Marcelletti¹,

Ferrante²,

Scortichini³

2010

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Forty-five Xanthomonas arboricola pv. juglandis (Xaj) strains originating from Juglans regia cultivation in different countries were molecularly typed by means of MultiLocus Sequence Typing (MLST), using acnB, gapA, gyrB and rpoD gene fragments. A total of 2.5 kilobases was used to infer the phylogenetic relationship among the strains and possible recombination events. Haplotype diversity, linkage disequilibrium analysis, selection tests, gene flow estimates and codon adaptation index were also assessed. The dendrograms built by maximum likelihood with concatenated nucleotide and amino acid sequences revealed two major and two minor phylotypes. The same haplotype was found in strains originating from different continents, and different haplotypes were found in strains isolated in the same year from the same location. A recombination breakpoint was detected within the rpoD gene fragment. At the pathovar level, the Xaj populations studied here are clonal and under neutral selection. However, four Xaj strains isolated from walnut fruits with apical necrosis are under diversifying selection, suggesting a possible new adaptation. Gene flow estimates do not support the hypothesis of geographic isolation of the strains, even though the genetic diversity between the strains increases as the geographic distance between them increases. A triplet deletion, causing the absence of valine, was found in the rpoD fragment of all 45 Xaj strains when compared with X. axonopodis pv. citri strain 306. The codon adaptation index was high in all four genes studied, indicating a relevant metabolic activity

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“…4), which results in some uncertainty over the number of times that the mbo operon has been acquired by the strains of genomospecies 1. This type of discrepancy is commonly found in phylogenetic analyses of P. syringae when using different housekeeping genes or even different genes from an operon from the hrp cluster, particularly for very closely related taxa, and has been interpreted to be a consequence of genetic exchange and recombination (21,59,(61)(62)(63). Examination of the mbo operon insertion site offers further significant clues about its evolutionary history, in that the insertion site was the same for all the strains and in all cases was associated with the loss of a continuous 67-bp fragment that is ancestral to P. syringae.…”

Section: Figmentioning

confidence: 99%

The Mangotoxin Biosynthetic Operon ( mbo ) Is Specifically Distributed within Pseudomonas syringae Genomospecies 1 and Was Acquired Only Once during Evolution

Carrión

Gutiérrez‐Barranquero

Arrebola

et al. 2013

Appl Environ Microbiol

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c Mangotoxin production was first described in Pseudomonas syringae pv. syringae strains. A phenotypic characterization of 94 P. syringae strains was carried out to determine the genetic evolution of the mangotoxin biosynthetic operon (mbo). We designed a PCR primer pair specific for the mbo operon to examine its distribution within the P. syringae complex. These primers amplified a 692-bp DNA fragment from 52 mangotoxin-producing strains and from 7 non-mangotoxin-producing strains that harbor the mbo operon, whereas 35 non-mangotoxin-producing strains did not yield any amplification. This, together with the analysis of draft genomes, allowed the identification of the mbo operon in five pathovars (pathovars aptata, avellanae, japonica, pisi, and syringae), all of which belong to genomospecies 1, suggesting a limited distribution of the mbo genes in the P. syringae complex. Phylogenetic analyses using partial sequences from housekeeping genes differentiated three groups within genomospecies 1. All of the strains containing the mbo operon clustered in groups I and II, whereas those lacking the operon clustered in group III; however, the relative branching order of these three groups is dependent on the genes used to construct the phylogeny. The mbo operon maintains synteny and is inserted in the same genomic location, with high sequence conservation around the insertion point, for all the strains in groups I and II. These data support the idea that the mbo operon was acquired horizontally and only once by the ancestor of groups I and II from genomospecies 1 within the P. syringae complex.T he bacterial plant pathogen Pseudomonas syringae is ubiquitous in nature and often causes economically important plant diseases. This bacterial species establishes an epiphytic population in association with a plant host's surfaces prior to infection. There are at least 50 pathovars, many of which cause a wide range of plant diseases that exhibit diverse symptoms, such as leaf or fruit lesions, cankers, blasts, and galls (1-7).P. syringae produces several type III effectors and virulence factors, but the role of its toxins is particularly significant during symptom development (1,(8)(9)(10). The current study is focused on mangotoxin, which inhibits the enzyme ornithine N-acetyltransferase (11, 12). Mangotoxin was initially detected in strains from P. syringae pv. syringae (11); however, its production was recently observed in strains of pathovar avellanae (13). Recent studies have reported the involvement of the mgo (8,12,14) and mbo (15) operons in mangotoxin production and P. syringae pv. syringae virulence. The mbo operon is composed of six genes, and all of them are directly involved in mangotoxin production.The development of specific methods for pathogen detection in planta is very important. In this sense, different PCR methods have been developed and improved to detect different P. syringae pathovars. For example, one PCR method used primers that were based on the 16S-23S ribosomal genes to identify strains of P. syring...

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Convergent evolution of phytopathogenic pseudomonads onto hazelnut

Cited by 22 publications

References 18 publications

High-Resolution Melting Analysis as a Powerful Tool to Discriminate and Genotype Pseudomonas savastanoi Pathovars and Strains

High-Resolution Melting Analysis as a Powerful Tool to Discriminate and Genotype Pseudomonas savastanoi Pathovars and Strains

Multilocus Sequence Typing Reveals Relevant Genetic Variation and Different Evolutionary Dynamics among Strains of Xanthomonas arboricola pv. juglandis

The Mangotoxin Biosynthetic Operon ( mbo ) Is Specifically Distributed within Pseudomonas syringae Genomospecies 1 and Was Acquired Only Once during Evolution

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