Fire Blight: Applied Genomic Insights of the Pathogen and Host

Abstract

The enterobacterial phytopathogen Erwinia amylovora causes fire blight, an invasive disease that threatens a wide range of commercial and ornamental Rosaceae host plants. The response elicited by E. amylovora in its host during disease development is similar to the hypersensitive reaction that typically leads to resistance in an incompatible host-pathogen interaction, yet no gene-for-gene resistance has been described for this host-pathogen system. Comparative genomic analysis has found an unprecedented degree of genetic uniformity among strains of E. amylovora, suggesting that the pathogen has undergone a recent genetic bottleneck. The genome of apple, an important host of E. amylovora, has been sequenced, creating new opportunities for the study of interactions between host and pathogen during fire blight development and for the identification of resistance genes. This review includes recent advances in the genomics of both host and pathogen.

Global Small RNA Chaperone Hfq and Regulatory Small RNAs Are Important Virulence Regulators in Erwinia amylovora

“…Thus, Hfq and the sRNAs that it regulates likely play a central role in the fine-tuning of virulence gene expression in E. amylovora. During fire blight pathogenesis, E. amylovora cells colonize and grow on the relatively nutrientrich stigma surface, on the high-osmotic flower nectarthode, within the leaf apoplast, and in the potentially low-nutrient vascular system (1). Transitions between these various host environments may occur over relatively short time scales, thus necessitating the ability to rapidly alter the production of virulence factors via posttranscriptional regulation.…”

“…During infection, E. amylovora enters host plants through natural openings in flowers or shoot tips and is able to rapidly move within plant hosts in the vascular tissue and establish systemic infections. To date, many virulence factors of E. amylovora have been characterized, with the major determinants including the type III secretion system (T3SS), amylovoran exopolysaccharide production, biofilm formation, and motility (1). E. amylovora pathogenesis on apple trees is manifested through several distinct stages and interactions with living and nonliving host cells.…”

“…In order to successfully establish infections, E. amylovora utilizes a complicated regulatory network involving two-component signal transduction systems, alternate sigma factors, quorum sensing, and the second messenger cyclic di-GMP to collectively control the expression of virulence genes at different stages of infection (1,4,10,(15)(16)(17)(18). In addition, the requirement at different times of infection for the T3SS and biofilm formation and the importance of cellular motility suggest that E. amylovora cells must be able to rapidly alter the production of distinct virulence factors in response to specific host cues.…”

Characterization of a cfr -Carrying Plasmid from Porcine Escherichia coli That Closely Resembles Plasmid pEA3 from the Plant Pathogen Erwinia amylovora

“…It displayed 98.2% nucleotide sequence identity to the corresponding region in plasmid pEA3. Plasmid pEA3 has a size of 29,585 bp and was originally identified in the plant pathogen Erwinia amylovora CFBP 2585 (GenBank accession number HF560646.1), which causes fire blight, a devastating disease that threatens a wide range of plants, including apple, pear, cotoneaster, and hawthorn shrubs and trees (17,18). Region B also harbored the genes of a type IV secretion system (T4SS) gene cluster (Fig.…”

Expression of the Bacterial Type III Effector DspA/E in Saccharomyces cerevisiae Down-regulates the Sphingolipid Biosynthetic Pathway Leading to Growth Arrest

“…The bacterium Erwinia amylovora is the causal agent of fire blight disease of pear and apple trees (15). The ability of E. amylovora to promote disease depends on a type III secretion system and on a single injected T3E named DspA/E (16,17).…”