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Strawberry is economically important and widely grown but susceptible to a large variety of phytopathogenic organisms. Among them, Xanthomonas fragariae is a quarantine bacterial pathogen threatening strawberry productions by causing angular leaf spots. Using whole transcriptome sequencing, gene expression of both plant and bacteria in planta was analyzed at two time points, 12- and 29-days post inoculation, in order to compare pathogen and host response between the stages of early visible and of well-developed symptoms. Among 28’588 known genes in strawberry and 4’046 known genes in X. fragariae expressed at both time points, a total of 361 plant and 144 bacterial genes were significantly differentially expressed, respectively. The identified higher expressed genes in the plants were pathogen-associated molecular pattern receptors and pathogenesis related thaumatin encoding genes, whereas the more expressed early genes were related to chloroplast metabolism as well as photosynthesis related coding genes. Most of X. fragariae genes involved in host interactions, recognitions and pathogenesis, were lower expressed at late-phase infection. This study gives a first insight on the interaction of X. fragariae with its host. The strawberry plant changed its metabolism consistently with the progression of infection.

Xanthomonas fragariae is a quarantine bacterial pathogen that causes angular leaf spot on strawberry. The aim of our study was to analyse the mechanism of interaction of this bacterium with its host plant at the transcriptome level. For this purpose, mRNAs of X. fragariae growing in Wilbrink's medium and from infected strawberry cv. Elsanta plants were isolated and sequenced using the Illumina MiSeq platform. The expression profiles of the bacteria in Wilbrink's medium and in planta were very diverse. Of the 3939 CDSs recorded, 1995 had significantly different expression in planta (966 and 1029 genes were down- and upregulated, respectively). Among the genes showing increased expression in planta, those with eggNOG/COG (evolutionary genealogy of genes: Non-supervised Orthologous Groups/Cluster of Orthologous Groups) categories associated with bacterial cell motility, signal transduction, transport and metabolism of inorganic ions and carbohydrates and transcription were overrepresented. Among the genes with the most increased expression in planta, genes primarily associated with flagella synthesis and chemotaxis were found. It is also interesting to note that out of the 31 genes localized on a plasmid, 16 were expressed differently in planta, which may indicate their potential role in plant-pathogen interactions. Many genes with differentiated expression that were localized on chromosome and plasmid encode proteins of unknown function.

The quarantine bacterium Xanthomonas fragariae causes angular leaf spots on strawberry. Its population structure was recently found to be divided into four (sub)groups resulting from two distinct main groups. Xanthomonas arboricola pv. fragariae causes bacterial leaf blight, but the bacterium has an unclear virulence status on strawberry. In this study, we use comparative genomics to provide an overview of the genomic variations of a set of 58 X. fragariae and five X. arboricola pv. fragariae genomes with a focus on virulence-related proteins. Structural differences within X. fragariae such as differential plasmid presence and large-scale genomic rearrangements were observed. On the other hand, the virulence-related protein repertoire was found to vary greatly at the interspecies level. In three out of five sequenced X. arboricola pv. fragariae strains, the major part of the Hrp type III secretion system was lacking. An inoculation test with strains from all four X. fragariae (sub)groups and X. arboricola pv. fragariae resulted in an interspecies difference in symptom induction since no symptoms were observed on the plants inoculated with X. arboricola pv. fragariae. Our analysis suggests that all X. fragariae (sub)groups are pathogenic on strawberry plants. On the other hand, the first genomic investigations of X. arboricola pv. fragariae revealed a potential lack of certain key virulence-related factors which may be related to the difficulties to reproduce symptoms on strawberry and could question the plant-host interaction of the pathovar.

Strawberry is economically important and widely grown, but susceptible to a large variety of phytopathogenic organisms. Among them, Xanthomonas fragariae is a quarantine bacterial pathogen threatening strawberry productions by causing angular leaf spots. Using whole transcriptome sequencing, the gene expression of both plant and bacteria in planta was analyzed at two time points, 12 and 29 days post inoculation, in order to compare the pathogen and host response between the stages of early visible and of well-developed symptoms. Among 28,588 known genes in strawberry and 4046 known genes in X. fragariae expressed at both time points, a total of 361 plant and 144 bacterial genes were significantly differentially expressed, respectively. The identified higher expressed genes in the plants were pathogen-associated molecular pattern receptors and pathogenesis-related thaumatin encoding genes, whereas the more expressed early genes were related to chloroplast metabolism as well as photosynthesis related coding genes. Most X. fragariae genes involved in host interaction, recognition, and pathogenesis were lower expressed at late-phase infection. This study gives a first insight into the interaction of X. fragariae with its host. The strawberry plant changed gene expression in order to consistently adapt its metabolism with the progression of infection.

Strawberry is economically important and widely grown, but susceptible to a large variety of phytopathogenic organisms. Among them, Xanthomonas fragariae is a quarantine bacterial pathogen threatening strawberry productions by causing angular leaf spots. Using whole transcriptome sequencing, the gene expression of both plant and bacteria in planta was analyzed at two time points, 12 and 29 days post inoculation, in order to compare the pathogen and host response between the stages of early visible and of well-developed symptoms. Among 28,588 known genes in strawberry and 4046 known genes in X. fragariae expressed at both time points, a total of 361 plant and 144 bacterial genes were significantly differentially expressed, respectively. The identified higher expressed genes in the plants were pathogen-associated molecular pattern receptors and pathogenesis-related thaumatin encoding genes, whereas the more expressed early genes were related to chloroplast metabolism as well as photosynthesis related coding genes. Most X. fragariae genes involved in host interaction, recognition, and pathogenesis were lower expressed at late-phase infection. This study gives a first insight into the interaction of X. fragariae with its host. The strawberry plant changed gene expression in order to consistently adapt its metabolism with the progression of infection.

The quarantine bacterium Xanthomonas fragariae causes angular leaf spots on strawberry. Its population structure was recently found to be divided into four (sub)groups resulting from two distinct main groups. Xanthomonas arboricola pv. fragariae causes bacterial leaf blight, but the bacterium has an unclear virulence status on strawberry. In this study, we use comparative genomics to provide an overview of the genomic variations of a set of 58 X. fragariae and five X. arboricola pv. fragariae genomes with a focus on virulence-related proteins. Structural differences within X. fragariae such as differential plasmid presence and large-scale genomic rearrangements were observed. On the other hand, the virulence-related protein repertoire was found to vary greatly at the interspecies level. In three out of five sequenced X. arboricola pv. fragariae strains, the major part of the Hrp type III secretion system was lacking. An inoculation test with strains from all four X. fragariae (sub)groups and X. arboricola pv. fragariae resulted in an interspecies difference in symptom induction since no symptoms were observed on the plants inoculated with X. arboricola pv. fragariae. Our analysis suggests that all X. fragariae (sub)groups are pathogenic on strawberry plants. On the other hand, the first genomic investigations of X. arboricola pv. fragariae revealed a potential lack of certain key virulence-related factors which may be related to the difficulties to reproduce symptoms on strawberry and could question the plant-host interaction of the pathovar.

Xanthomonas fragariae is a quarantine bacterial pathogen that causes angular leaf spot on strawberry. The aim of our study was to analyse the mechanism of interaction of this bacterium with its host plant at the transcriptome level. For this purpose, mRNAs of X. fragariae growing in Wilbrink's medium and from infected strawberry cv. Elsanta plants were isolated and sequenced using the Illumina MiSeq platform. The expression profiles of the bacteria in Wilbrink's medium and in planta were very diverse. Of the 3939 CDSs recorded, 1995 had significantly different expression in planta (966 and 1029 genes were down- and upregulated, respectively). Among the genes showing increased expression in planta, those with eggNOG/COG (evolutionary genealogy of genes: Non-supervised Orthologous Groups/Cluster of Orthologous Groups) categories associated with bacterial cell motility, signal transduction, transport and metabolism of inorganic ions and carbohydrates and transcription were overrepresented. Among the genes with the most increased expression in planta, genes primarily associated with flagella synthesis and chemotaxis were found. It is also interesting to note that out of the 31 genes localized on a plasmid, 16 were expressed differently in planta, which may indicate their potential role in plant-pathogen interactions. Many genes with differentiated expression that were localized on chromosome and plasmid encode proteins of unknown function.

Xanthomonas fragariae is a quarantine bacterial pathogen that causes angular leaf spot on strawberry. The aim of our study was to analyse the mechanism of interaction of this bacterium with its host plant at the transcriptome level. For this purpose, mRNAs of X. fragariae growing in Wilbrink’s medium and from infected strawberry cv. Elsanta plants were isolated and sequenced using the Illumina MiSeq platform. The expression profiles of the bacteria in Wilbrink’s medium and in planta were very diverse. Of the 3939 CDSs recorded, 1995 had significantly different expression in planta (966 and 1029 genes were down- and upregulated, respectively). Among the genes showing increased expression in planta, those with eggNOG/COG (evolutionary genealogy of genes: Non-supervised Orthologous Groups/Cluster of Orthologous Groups) categories associated with bacterial cell motility, signal transduction, transport and metabolism of inorganic ions and carbohydrates and transcription were overrepresented. Among the genes with the most increased expression in planta, genes primarily associated with flagella synthesis and chemotaxis were found. It is also interesting to note that out of the 31 genes localized on a plasmid, 16 were expressed differently in planta, which may indicate their potential role in plant–pathogen interactions. Many genes with differentiated expression that were localized on chromosome and plasmid encode proteins of unknown function.

Xanthomonas fragariae is a quarantine organism in Europe, causing angular leaf spots on strawberry plants. It is spreading worldwide in strawberry-producing regions due to import of plant material through trade and human activities. In order to resolve the population structure at the strain level, we have employed high-resolution molecular typing tools on a comprehensive strain collection representing global and temporal distribution of the pathogen. Clustered regularly interspaced short palindromic repeat regions (CRISPRs) and variable number of tandem repeats (VNTRs) were identified within the reference genome of X. fragariae LMG 25863 as a potential source of variation. Strains from our collection were whole-genome sequenced and used in order to identify variable spacers and repeats for discriminative purpose. CRISPR spacer analysis and multiple-locus VNTR analysis (MLVA) displayed a congruent population structure, in which two major groups and a total of four subgroups were revealed. The two main groups were genetically separated before the first X. fragariae isolate was described and are potentially responsible for the worldwide expansion of the bacterial disease. Three primer sets were designed for discriminating CRISPR-associated markers in order to streamline group determination of novel isolates. Overall, this study describes typing methods to discriminate strains and monitor the pathogen population structure, more especially in the view of a new outbreak of the pathogen.

Xanthomonas arboricola pv. fragariae was described in 2001 as the causal agent of strawberry bacterial leaf blight. We report here the first draft whole-genome sequences of fiveX. arboricolapv. fragariae isolates from Italy and France.

Xanthomonas fragariae is a quarantine organism in Europe, causing angular leaf spots on strawberry plants. It is spreading worldwide in strawberry-producing regions due to import of plant material through trade and human activities. In order to resolve the population structure at the strain level, we have employed high-resolution molecular typing tools on a comprehensive strain collection representing global and temporal distribution of the pathogen. Clustered regularly interspaced short palindromic repeat regions (CRISPRs) and variable number of tandem repeats (VNTRs) were identified within the reference genome of X. fragariae LMG 25863 as a potential source of variation. Strains from our collection were whole-genome sequenced and used in order to identify variable spacers and repeats for discriminative purpose. CRISPR spacer analysis and multiple-locus VNTR analysis (MLVA) displayed a congruent population structure, in which two major groups and a total of four subgroups were revealed. The two main groups were genetically separated before the first X. fragariae isolate was described and are potentially responsible for the worldwide expansion of the bacterial disease. Three primer sets were designed for discriminating CRISPR-associated markers in order to streamline group determination of novel isolates. Overall, this study describes typing methods to discriminate strains and monitor the pathogen population structure, more especially in the view of a new outbreak of the pathogen.

Xanthomonas arboricola pv. fragariae was described in 2001 as the causal agent of strawberry bacterial leaf blight. We report here the first draft whole-genome sequences of fiveX. arboricolapv. fragariae isolates from Italy and France.

Xanthomonas fragariae is a quarantine organism in Europe, causing angular leaf spots on strawberry plants. It is spreading worldwide in strawberry-producing regions due to import of plant material through trade and human activities. In order to resolve the population structure at the strain level, we have employed high-resolution molecular typing tools on a comprehensive strain collection representing global and temporal distribution of the pathogen. Clustered regularly interspaced short palindromic repeat regions (CRISPRs) and variable number of tandem repeats (VNTRs) were identified within the reference genome of X. fragariae LMG 25863 as a potential source of variation. Strains from our collection were whole-genome sequenced and used in order to identify variable spacers and repeats for discriminative purpose. CRISPR spacer analysis and multiple-locus VNTR analysis (MLVA) displayed a congruent population structure, in which two major groups and a total of four subgroups were revealed. The two main groups were genetically separated before the first X. fragariae isolate was described and are potentially responsible for the worldwide expansion of the bacterial disease. Three primer sets were designed for discriminating CRISPR-associated markers in order to streamline group determination of novel isolates. Overall, this study describes typing methods to discriminate strains and monitor the pathogen population structure, more especially in the view of a new outbreak of the pathogen.

Xanthomonas fragariae is a worldwide spread plant bacterial disease causing angular leaf spots, and thus reducing the yield of production for strawberry fruits. Three isolates with variable geographic and time origins were sequenced with long-read technology (PacBio) to generate finished genomes of virulent strains and observe their variability in content.

Molecular diagnostics of plant pathogens are crucial to prevent disease spread and to enhance food quality and security. A comparative genomics approach using genomes of different Xanthomonas species and pathovars was applied to identify highly specific targets in the genome of Xanthomonas fragariae, the causal agent of angular leaf spot of strawberry, listed under quarantine regulations in Europe. A reliable and sensitive loop-mediated isothermal amplification (LAMP) assay was designed using a unique marker providing a highly specific and rapid detection, making this technique convenient for on-site detection. Specificity of the designed assay was tested on 37 culture collection strains of X. fragariae, 82 strains of other Xanthomonas species and pathovars and 11 strains of other bacterial genera isolated from strawberry leaves. A detection limit of 10^2 fg was achieved, approximating 20 genome copies per reaction. When performing analyses with crude plant material, a consistent lower detection efficiency of 10^2 CFU ml−1 was achieved. The LAMP assay designed in this study was adapted to work on crude plant material without any prior extensive extraction steps or incubation period. Moreover, it does not require advanced analytical knowledge or a fully equipped laboratory. Results were produced within 7 to 20 min depending on the pathogen concentration, thus providing a high throughput and user-friendly method for detection and screening of plant material in support of quarantine regulations.

Xanthomonas fragariae is a worldwide spread plant bacterial disease causing angular leaf spots, and thus reducing the yield of production for strawberry fruits. Three isolates with variable geographic and time origins were sequenced with long-read technology (PacBio) to generate finished genomes of virulent strains and observe their variability in content.

Molecular diagnostics of plant pathogens are crucial to prevent disease spread and to enhance food quality and security. A comparative genomics approach using genomes of different Xanthomonas species and pathovars was applied to identify highly specific targets in the genome of Xanthomonas fragariae, the causal agent of angular leaf spot of strawberry, listed under quarantine regulations in Europe. A reliable and sensitive loop-mediated isothermal amplification (LAMP) assay was designed using a unique marker providing a highly specific and rapid detection, making this technique convenient for on-site detection. Specificity of the designed assay was tested on 37 culture collection strains of X. fragariae, 82 strains of other Xanthomonas species and pathovars and 11 strains of other bacterial genera isolated from strawberry leaves. A detection limit of 10^2 fg was achieved, approximating 20 genome copies per reaction. When performing analyses with crude plant material, a consistent lower detection efficiency of 10^2 CFU ml−1 was achieved. The LAMP assay designed in this study was adapted to work on crude plant material without any prior extensive extraction steps or incubation period. Moreover, it does not require advanced analytical knowledge or a fully equipped laboratory. Results were produced within 7 to 20 min depending on the pathogen concentration, thus providing a high throughput and user-friendly method for detection and screening of plant material in support of quarantine regulations.

Xanthomonas fragariae is a worldwide-spread plant bacterial disease causing angular leaf spots, thus reducing the yield of production for strawberry fruits. Three isolates with various geographic and time origins were sequenced with long-read technology (PacBio) to generate finished genome sequences of virulent strains and observe the variability in their contents.