Pathogen recognition in compatible plant-microbe interactions

Microbial infections in plant leaves remain a major challenge in agriculture. Hence an understanding of disease mechanisms at the molecular level is of paramount importance for identifying possible intervention points for their control. Whole-transcriptome changes during early disease stages in susceptible plant species are less well-documented than those of resistant ones. This study focuses on the differential transcriptional changes at 24 hours post inoculation (hpi) in tomato leaflets affected by three pathogens: (1) Phytophthora infestans, (2) Botrytis cinerea, and (3) Oidium neolycopersici. Grey mould (B. cinerea) was the disease that had progressed the most by 24 hpi, both in terms of visible symptoms as well as differential gene expression. By means of RNA-seq, we identified  50 differentially expressed tomato genes induced by B. cinerea infection and 18 by P. infestans infection at 24 hpi. Additionally, a set of 63 genes were differentially expressed during all three diseases when compared by a Bayesian approach to their respective mock infections. And Gene expression patterns were found to also depend on the inoculation technique. These findings suggest a specific and distinct transcriptional response in plant leaf tissue in reaction to B. cinerea and P. infestans invasion at 24 hpi, indicating that plants may recognize the attacking pathogen

Upregulation of gray mold-induced plant genes in uninfected rachis tissue

Molecular detection of infections is normally performed by searching for the DNA of the pathogen in infected tissues. We consider the possibility of detecting an ongoing infection by analyzing the systemic response. The genes coding for FAD-binding domain-containing protein and two Cytochrome P450s were upregulated in visually healthy tissue of pathogeninoculated leaves at 24 and 48 hours post infection, both during tip and side leaflet inoculations. The upregulation of these genes was statistically not different between rachis and inoculation spot. The results suggest the possibility to sense B. cinerea single leaflet infections by measuring plant gene expression in rachis-derived samples

Erwinia amylovora in the genomics era : from genomes to pathogen virulence, regulation, and disease control strategies

The publication of the first Erwinia amylovora genome has greatly accelerated and advanced our understanding of the fire blight organism. With the availability of multiple genomes, it quickly became clear that chromosomal diversity is relatively small, and that most of the pan-genome variance is attributable to plasmids. In addition to gaining a more detailed view of the known virulence factors, genomics has enabled new breakthrough studies of virulence regulation mechanisms. Furthermore, several niche adaptation and ecological fitness factors, though not directly influencing virulence, have been studied in greater detail, providing novel insights into the physiology and ecology of the bacterium. Additionally, application of genome data has yielded improved diagnostics and enabled population studies at different geographic scales

Phenotypic comparison of clinical and plant-beneficial strains of Pantoea agglomerans

Certain strains of Pantoea are used as biocontrol agents for the suppression of plant diseases. However, their commercial registration is hampered in some countries because of biosafety concerns. This study compares clinical and plant-beneficial strains of P. agglomerans and related species using a phenotypic analysis approach in which plant-beneficial effects, adverse effects in nematode models, and toxicity were evaluated. Plant-beneficial effects were determined as the inhibition of apple fruit infection by Penicillium expansum and apple flower infection by Erwinia amylovora. Clinical strains had no general inhibitory activity against infection by the fungal or bacterial plant pathogens, as only one clinical strain inhibited P. expansum and three inhibited E. amylovora. By contrast, all biocontrol strains showed activity against at least one of the phytopathogens, and three strains were active against both. The adverse effects in animals were evaluated in the plant-parasitic nematode Meloidogyne javanica and the bacterial-feeding nematode Caenorhabditis elegans. Both models indicated adverse effects of the two clinical strains but not of any of the plant-beneficial strains. Toxicity was evaluated by means of hemolytic activity in blood, and genotoxicity with the Ames test. None of the strains, whether clinical or plant-beneficial, showed any evidence of toxicity. [Int Microbiol 2014; 17(2):81-90]Keywords: Pantoea agglomerans · Erwinia amylovora · Meloidogyne javanica · Penicillium expansum · Caenorhabditis elegans · biocontrol · biosafety · toxicity · hemolytic activity · Ames tes

Erwinia species identification using matrix-assisted laser desorption ionization-time of flight mass spectrometry

Rapid and reliable identification of plant pathogenic bacteria is critical for effective implementation of phytosanitary measures. The genus Erwinia includes a number of economically important plant pathogens such as fire blight agent Erwinia amylovora or Asian pear pathogen Erwinia pyrifoliae, together with closely related plant epiphytes of unknown pathogenicity or even with a potential use for biological control like Erwinia tasmaniensis or Erwinia billingiae, respectively. Current laboratory methods to achieve satisfactory identification and discrimination between species within the Erwinia genus are based on the isolation on semi-selective media, serology, specific PCR and gene locus sequencing: these approaches are complicated and time-consuming, often requiring a priori assumptions over the identity of the isolates. Here we present a streamlined approach based on whole-cell Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry (MALDI-TOF MS) based on the AXIMA mass spectrometer of Shimadzu-Biotech Corp that demonstrates the potential of this technology for quick species identification in plant diagnostics within the genus Erwinia

Phenotypic comparison of clinical and plant-beneficial strains of Pantoea agglomerans

Certain strains of Pantoea are used as biocontrol agents for the suppression of plant diseases. However, their commercial registration is hampered in some countries because of biosafety concerns. This study compares clinical and plant-beneficial strains of P. agglomerans and related species using a phenotypic analysis approach in which plant-beneficial effects, adverse effects in nematode models, and toxicity were evaluated. Plant-beneficial effects were determined as the inhibition of apple fruit infection by Penicillium expansum and apple flower infection by Erwinia amylovora. Clinical strains had no general inhibitory activity against infection by the fungal or bacterial plant pathogens, as only one clinical strain inhibited P. expansum and three inhibited E. amylovora. By contrast, all biocontrol strains showed activity against at least one of the phytopathogens, and three strains were active against both. The adverse effects in animals were evaluated in the plant-parasitic nematode Meloidogyne javanica and the bacterial-feeding nematode Caenorhabditis elegans. Both models indicated adverse effects of the two clinical strains but not of any of the plant-beneficial strains. Toxicity was evaluated by means of hemolytic activity in blood, and genotoxicity with the Ames test. None of the strains, whether clinical or plant-beneficial, showed any evidence of toxicity

Opening the black box: How staff training and development may affect the innovation of enterprises

We describe a research on the interplay that appears to exist in companies between Human Resource Management and innovation. This complex, multicomponent, non-linear and dynamic interplay is often viewed as a "black box". To help open the black box, we outline both a theoretical framework and preliminary empirical data. We view innovation as an organization-level property, favored by the organization's self-perception as a knowledge engine. Therefore, we devised a protocol to study the companies' strategies for training and development and their innovation profile. The protocol consisted in a questionnaire with 100 closed questions, suitable for companies which rely mostly on an inner training and development service. The questionnaire was administered to a sample of Italian firms from the Food & beverages and Fashion markets. The results show that certain facets of training and development are indeed correlated to innovation. Finally, we discuss the results

Role of the type VI secretion systems during disease interactions of Erwinia amylovora with its plant host

Background: Type VI secretion systems (T6SS) are widespread among Gram-negative bacteria and have a potential role as essential virulence factors or to maintain symbiotic interactions. Three T6SS gene clusters were identified in the genome of E. amylovora CFBP 1430, of which T6SS-1 and T6SS-3 represent complete T6SS machineries, while T6SS-2 is reduced in its gene content. Results: To assess the contribution of T6SSs to virulence and potential transcriptomic changes of E. amylovora CFBP 1430, single and double mutants in two structural genes were generated for T6SS-1 and T6SS-3. Plant assays showed that mutants in T6SS-3 were slightly more virulent in apple shoots while inducing less disease symptoms on apple flowers, indicating that T6SSs have only a minor effect on virulence of E. amylovora CFBP 1430. The mutations led under in vitro conditions to the differential expression of type III secretion systems, iron acquisition, chemotaxis, flagellar, and fimbrial genes. Comparison of the in planta and in vitro transcriptome data sets revealed a common differential expression of three processes and a set of chemotaxis and motility genes. Additional experiments proved that T6SS mutants are impaired in their motility. Conclusion: These results suggest that the deletion of T6SSs alters metabolic and motility processes. Nevertheless, the difference in lesion development in apple shoots and flower necrosis of T6SS mutants was indicative that T6SSs influences the disease progression and the establishment of the pathogen on host plants

High-quality draft genome sequence of pseudomonas wadenswilerensis CCOS 864T

Pseudomonas wadenswilerensis CCOS 864T was isolated in 2014 from forest soil. The organism belongs taxonomically to the Pseudomonas putida group, members of which have been well studied for their potential in biotechnological applications. We present here the draft genome sequence of P. wadenswilerensis CCOS 864T

Genomics and current genetic understanding of Erwinia amylovora and the fire blight antagonist Pantoea vagans

Abstract The bacterial plant pathogen Erwinia amylovora causes fire blight, a major disease threat to pome fruit production worldwide with further impact on a wide-range of Rosaceae species. Important factors contributing to the development of the disease were discovered in the last decades. Comparative genomics of the genera Erwinia and Pantoea is coming into focus with the recent availability of complete genome sequences. Insights from comparative genomics now position us to answer fundamental questions regarding the evolution of E. amylovora as a successful pathogen and the critical elements for biocontrol activity of Pantoea spp. This trove of new data promises to reveal novel determinants and to understand interactive pathways for virulence, host range and ecological fitness. The ultimate aim is now to apply genomics and identify the pathogen Achilles heels and antagonist mechanisms of action as targets for designing innovative control strategies for fire blight