<i>Erwinia amylovora pyrC</i>
 mutant causes fire blight despite pyrimidine auxotrophy

Ramos, Laura S.; Sinn, Judith P.; Lehman, Brian L.; Pfeufer, Emily E.; Peter, Kari A.; McNellis, Timothy W.

doi:10.1111/lam.12417

Cited by 10 publications

(9 citation statements)

References 23 publications

(44 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This implies that these metabolites are not sufficiently available to E. amylovora from the host to render their biosynthesis by the bacterium unnecessary for full virulence. The reduced virulence of argD, guaB, and pyrC mutants is consistent with previous studies (22,23,28) and verified the effectiveness of the fruitlet disease screen.…”

Section: Resultssupporting

confidence: 90%

“…Although the screening was comprehensive, it has not yet reached saturation, since 24 of the genes had only a single mutant allele. Three of the genes found in the screen (argD, guaB, and pyrC) are known to produce auxotrophic phenotypes in E. amylovora when mutated (22,23,28), demonstrating the consistency of the current results with prior studies.…”

Section: Resultssupporting

confidence: 78%

See 1 more Smart Citation

Erwinia amylovora Auxotrophic Mutant Exometabolomics and Virulence on Apples

Klee

Sinn

Finley

et al. 2019

Appl Environ Microbiol

View full text Add to dashboard Cite

The Gram-negative bacterium Erwinia amylovora causes fire blight disease of apples and pears. While the virulence systems of E. amylovora have been studied extensively, relatively little is known about its parasitic behavior. The aim of this study was to identify primary metabolites that must be synthesized by this pathogen for full virulence. A series of auxotrophic E. amylovora mutants, representing 21 metabolic pathways, were isolated and characterized for metabolic defects and virulence in apple immature fruits and shoots. On detached apple fruitlets, mutants defective in arginine, guanine, hexosamine, isoleucine/valine, leucine, lysine, proline, purine, pyrimidine, sorbitol, threonine, tryptophan, and glucose metabolism had reduced virulence compared to the wild type, while mutants defective in asparagine, cysteine, glutamic acid, histidine, and serine biosynthesis were as virulent as the wild type. Auxotrophic mutant growth in apple fruitlet medium had a modest positive correlation with virulence in apple fruitlet tissues. Apple tree shoot inoculations with a representative subset of auxotrophs confirmed the apple fruitlet results. Compared to the wild type, auxotrophs defective in virulence caused an attenuated hypersensitive immune response in tobacco, with the exception of an arginine auxotroph. Metabolomic footprint analyses revealed that auxotrophic mutants which grew poorly in fruitlet medium nevertheless depleted environmental resources. Pretreatment of apple flowers with an arginine auxotroph inhibited the growth of the wild-type E. amylovora, while heat-killed auxotroph cells did not exhibit this effect, suggesting nutritional competition with the virulent strain on flowers. The results of our study suggest that certain nonpathogenic E. amylovora auxotrophs could have utility as fire blight biocontrol agents. IMPORTANCE This study has revealed the availability of a range of host metabolites to E. amylovora cells growing in apple tissues and has examined whether these metabolites are available in sufficient quantities to render bacterial de novo synthesis of these metabolites partially or even completely dispensable for disease development. The metabolomics analysis revealed that auxotrophic E. amylovora mutants have substantial impact on their environment in culture, including those that fail to grow appreciably. The reduced growth of virulent E. amylovora on flowers treated with an arginine auxotroph is consistent with the mutant competing for limiting resources in the flower environment. This information could be useful for novel fire blight management tool development, including the application of nonpathogenic E. amylovora auxotrophs to host flowers as an environmentally friendly biocontrol method. Fire blight management options are currently limited mainly to antibiotic sprays onto open blossoms and pruning of infected branches, so novel management options would be attractive to growers.

show abstract

Section: Resultssupporting

confidence: 90%

Section: Resultssupporting

confidence: 78%

Erwinia amylovora Auxotrophic Mutant Exometabolomics and Virulence on Apples

Klee

Sinn

Finley

et al. 2019

Appl Environ Microbiol

View full text Add to dashboard Cite

show abstract

“…To our knowledge the concentrations of pyrimidines in the tomato hosts have not been reported. It has been reported that Erwinia amylovora can obtain sufficient pyrimidines from host tissue to support growth and cause disease [54]. The situation we observe with P. syringae is more similar to the findings reported for some human bacterial pathogens, where de novo pyrimidine synthesis is required for growth in host-derived material [55].…”

Section: Discussionsupporting

confidence: 87%

Disruption of the carA gene in Pseudomonas syringae results in reduced fitness and alters motility

et al. 2016

View full text Add to dashboard Cite

BackgroundPseudomonas syringae infects diverse plant species and is widely used in the study of effector function and the molecular basis of disease. Although the relationship between bacterial metabolism, nutrient acquisition and virulence has attracted increasing attention in bacterial pathology, there is limited knowledge regarding these studies in Pseudomonas syringae. The aim of this study was to investigate the function of the carA gene and the small RNA P32, and characterize the regulation of these transcripts.ResultsDisruption of the carA gene (ΔcarA) which encodes the predicted small chain of carbamoylphosphate synthetase, resulted in arginine and pyrimidine auxotrophy in Pseudomonas syringae pv. tomato DC3000. Complementation with the wild type carA gene was able to restore growth to wild-type levels in minimal medium. Deletion of the small RNA P32, which resides immediately upstream of carA, did not result in arginine or pyrimidine auxotrophy. The expression of carA was influenced by the concentrations of both arginine and uracil in the medium. When tested for pathogenicity, ΔcarA showed reduced fitness in tomato as well as Arabidopsis when compared to the wild-type strain. In contrast, mutation of the region encoding P32 had minimal effect in planta. ΔcarA also exhibited reduced motility and increased biofilm formation, whereas disruption of P32 had no impact on motility or biofilm formation.ConclusionsOur data show that carA plays an important role in providing arginine and uracil for growth of the bacteria and also influences other factors that are potentially important for growth and survival during infection. Although we find that the small RNA P32 and carA are co-transcribed, P32 does not play a role in the phenotypes that carA is required for, such as motility, cell attachment, and virulence. Additionally, our data suggests that pyrimidines may be limited in the apoplastic space of the plant host tomato.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0819-z) contains supplementary material, which is available to authorized users.

show abstract

“…Knockout of genes of the pathogenicity island of different E . amylovora strains and other E a mutations, which have led to the discovery of more virulence factors (Ramos et al., 2013, 2015; Klee et al., 2018), will improve our understanding of the pathogenic process.…”

Section: Discussionmentioning

confidence: 99%

Malus Hosts–Erwinia amylovora Interactions: Strain Pathogenicity and Resistance Mechanisms

et al. 2019

View full text Add to dashboard Cite

The bacterium, Erwinia amylovora , deposits effector proteins such as AvrRpt2 EA into hosts through the type III secretion pathogenicity island to cause fire blight in susceptible Malus genotypes. A single nucleotide polymorphism in the AvrRpt2 EA effector plays a key role in pathogen virulence on Malus hosts by exchanging one cysteine to serine in the effector protein sequence. Fire blight resistance quantitative trait loci (QTLs) were detected in a few apple cultivars and wild Malus genotypes with the resistance of wild apples generally found to be stronger than their domestic relatives. The only candidate and functionally analyzed fire blight resistance genes proposed are from wild apple genotypes. Nevertheless, the aforementioned AvrRpt2 EA SNP and a couple of effector mutants of E . amylovora are responsible for the breakdown of resistance from a few Malus donors including detected QTLs and underlying R -genes. This review summarizes a key finding related to the molecular basis underpinning an aspect of virulence of E . amylovora on Malus genotypes, as well as mechanisms of host recognition and specificity, and their implications on the results of genetic mapping and phenotypic studies within the last 5–6 years. Although the knowledge gained has improved our understanding of the Malus – E. amylovora system, more research is required to fully grasp the resistance mechanisms in this genus especially as they pertain to direct interactions with pathogen effectors.

show abstract

Erwinia amylovora pyrC mutant causes fire blight despite pyrimidine auxotrophy

Cited by 10 publications

References 23 publications

Erwinia amylovora Auxotrophic Mutant Exometabolomics and Virulence on Apples

Erwinia amylovora Auxotrophic Mutant Exometabolomics and Virulence on Apples

Disruption of the carA gene in Pseudomonas syringae results in reduced fitness and alters motility

Malus Hosts–Erwinia amylovora Interactions: Strain Pathogenicity and Resistance Mechanisms

Contact Info

Product

Resources

About