Distinct Virulence Mechanisms of in Onion Foliar and Bulb Scale Tissues.

Slippery skin of onion caused by pv. (Bga) is a common bacterial disease reported from onion growing regions around the world. Despite the increasing attention in recent years, our understanding of the virulence mechanisms of this pathogen remains limited.

Exploring the open (host) range.

The report from Grenz et al. in the latest issue of Cell Host & Microbe demonstrates how incorporation of phenotypic, genetic, genomic, and evolutionary information into experimental design provides a more complete picture than focusing on single host-pathogen relationships.

Complete genome sequences of strains GM1 and GM2, isolated from the leaves of garlic mustard.

We report the complete genomes of two strains, GM1 and GM2, isolated from garlic mustard plants. strain GM1 was found to carry a HiVir pantaphos biosynthetic gene cluster, which causes onion necrosis.

Altering cold-regulated gene expression decouples the salicylic acid-growth trade-off in Arabidopsis.

In Arabidopsis (Arabidopsis thaliana), overproduction of salicylic acid (SA) increases disease resistance and abiotic stress tolerance but penalizes growth. This growth-defense trade-off has hindered the adoption of SA-based disease management strategies in agriculture. However, investigation of how SA inhibits plant growth has been challenging because many SA-hyperaccumulating Arabidopsis mutants have developmental defects due to the pleiotropic effects of the underlying genes.

Thiosulfinate Tolerance Gene Clusters Are Common Features of Onion Pathogens.

pv. , , and are common bacterial pathogens of onion. Onions produce organosulfur thiosulfinate defensive compounds after cellular decompartmentalization.

Genomic delineation and description of species and within-species lineages in the genus .

As the name of the genus ("of all sorts and sources") suggests, this genus includes bacteria with a wide range of provenances, including plants, animals, soils, components of the water cycle, and humans. Some members of the genus are pathogenic to plants, and some are suspected to be opportunistic human pathogens; while others are used as microbial pesticides or show promise in biotechnological applications. During its taxonomic history, the genus and its species have seen many revisions.

Pantailocins: phage-derived bacteriocins from and subsp. .

Phage-derived bacteriocins (tailocins) are ribosomally synthesized structures produced by bacteria in order to provide advantages against competing strains under natural conditions. Tailocins are highly specific in their target range and have proven to be effective for the prevention and/or treatment of bacterial diseases under clinical and agricultural settings. We describe the discovery and characterization of a new tailocin locus encoded within genomes of and subsp.

Draft genome sequences for ATCC 35400 and subspecies ICMP 10132.

Here, we describe draft genome sequences for two bacterial isolates from the genus . ATCC 35400 was originally isolated from honeydew melon and was obtained from the American Type Culture Collection. subspecies ICMP 10132 was originally isolated from sugarcane and classified as , but average nucleotide identity and discriminatory PCR support species reclassification.

Discovery of the Hrp Type III Secretion System in Phytopathogenic Bacteria: How Investigation of Hypersensitive Cell Death in Plants Led to a Novel Protein Injector System and a World of Inter-Organismal Molecular Interactions Within Plant Cells.

In the early 1960s, and other host-specific phytopathogenic proteobacteria were discovered to elicit a rapid, resistance-associated death when infiltrated at high inoculum levels into nonhost tobacco leaves. This hypersensitive reaction (or response; HR) was a useful indicator of basic pathogenic ability. Research over the next 20 years failed to identify an elicitor of the HR but revealed that its elicitation required contact between metabolically active bacterial and plant cells.

Genome-wide association and dissociation studies in reveal potential virulence factors affecting and × hybrid.

is a member of a species complex that causes center rot of bulb onions () and also infects other crops like leeks (), chives (), bunching onion or Welsh onion (), and garlic (). This pathogen relies on a chromosomal phosphonate biosynthetic gene cluster (HiVir) and a plasmid-borne thiosulfinate tolerance cluster () for onion pathogenicity and virulence, respectively. However, pathogenicity and virulence factors associated with other species remain unknown.

Evaluating Options to Increase the Efficacy of Biocontrol Agents for the Management of spp. Under Field Conditions.

Center rot of onion is caused by a complex of plant pathogenic species, which can lead to significant yield losses in the field and during storage. Conventional growers use foliar protectants such as a mixture of copper bactericides and an ethylene-bis-dithiocarbamate (EBDC) fungicide to manage the disease; however, organic growers have limited management options besides copper-protectants. Biocontrol agents (BCAs) provide an alternative; however, their efficacy could be compromised due in part to their inability to colonize the foliage.

RpoS contributes in a host-dependent manner to colonization of the leaf apoplast during plant disease.

Contaminated fresh produce has been routinely linked to outbreaks of Salmonellosis. Multiple studies have identified factors associated with successful colonization of diverse plant niches and tissues. It has also been well documented that can benefit from the conditions generated during plant disease by host-compatible plant pathogens.

In planta transcriptomics reveals conflicts between pattern-triggered immunity and the AlgU sigma factor regulon.

In previous work, we determined the transcriptomic impacts of flg22 pre-induced Pattern Triggered Immunity (PTI) in Arabidopsis thaliana on the pathogen Pseudomonas syringae pv. tomato DC3000 (Pto). During PTI exposure we observed expression patterns in Pto reminiscent of those previously observed in a Pto algU mutant.

Genome Context Influences Evolutionary Flexibility of Nearly Identical Type III Effectors in Two Phytopathogenic Pseudomonads.

Integrative Conjugative Elements (ICEs) are replicons that can insert and excise from chromosomal locations in a site-specific manner, can conjugate across strains, and which often carry a variety of genes useful for bacterial growth and survival under specific conditions. Although ICEs have been identified and vetted within certain clades of the agricultural pathogen , the impact of ICE carriage and transfer across the entire species complex remains underexplored. Here we identify and vet an ICE (PmaICE-DQ) from pv.

Validation of Species-Specific PCR Assays for the Detection of , , , and .

Species of represent a group of plant pathogenic bacteria that infect a variety of agro-economically important plant species. Among these, a complex of , , , and subsp. cause center rot in onion, resulting in significant economic losses.

Pan-Genome-Wide Analysis of Identified Genes Linked to Pathogenicity in Onion.

Pantoea ananatis, a gram negative and facultative anaerobic bacterium is a member of a spp. complex that causes center rot of onion, which significantly affects onion yield and quality. This pathogen does not have typical virulence factors like type II or type III secretion systems but appears to require a biosynthetic gene-cluster, HiVir/PASVIL (located chromosomally comprised of 14 genes), for a phosphonate secondary metabolite, and the '' gene cluster (located in plasmid and comprised of 11 genes) that aids in bacterial colonization in onion bulbs by imparting tolerance to thiosulfinates.

Patterns of Seed-to-Seedling Transmission of pv. , the Causal Agent of Cotton Bacterial Blight.

Cotton bacterial blight (CBB), caused by pv. , was a major disease of cotton in the United States in the early part of the twentieth century. The reemergence of CBB revealed many gaps in our understanding of this important disease.

The Distribution of Onion Virulence Gene Clusters Among spp.

is a gram-negative bacterium and the primary causal agent of center rot of onions in Georgia. Previous genomic studies identified two virulence gene clusters, HiVir and , associated with center rot. The HiVir gene cluster is required to induce necrosis on onion tissues via synthesis of pantaphos, (2-hydroxy[phosphono-methyl)maleate), a phosphonate phytotoxin.

AlgU, a Conserved Sigma Factor Regulating Abiotic Stress Tolerance and Promoting Virulence in .

can rapidly deploy specialized functions to deal with abiotic and biotic stresses. Host niches pose specific sets of environmental challenges driven, in part, by immune defenses. Bacteria use a "just-in-time" strategy of gene regulation, meaning that they only produce the functions necessary for survival as needed.

Widely Conserved Attenuation of Plant MAMP-Induced Calcium Influx by Bacteria Depends on Multiple Virulence Factors and May Involve Desensitization of Host Pattern Recognition Receptors.

Successful pathogens must efficiently defeat or delay host immune responses, including those triggered by release or exposure of microbe-associated molecular patterns (MAMPs). Knowledge of the molecular details leading to this phenomenon in genuine plant-pathogen interactions is still scarce. We took advantage of the well-established - pv.

Transcriptome landscape of a bacterial pathogen under plant immunity.

Plant pathogens can cause serious diseases that impact global agriculture. The plant innate immunity, when fully activated, can halt pathogen growth in plants. Despite extensive studies into the molecular and genetic bases of plant immunity against pathogens, the influence of plant immunity in global pathogen metabolism to restrict pathogen growth is poorly understood.

Genetic Diversity Analysis Reveals Limited Genomic Diversity as Well as Accessory Genes Correlated with Onion Pathogenicity.

is a member of the family Enterobacteriaceae and an enigmatic plant pathogen with a broad host range. Although strains can be aggressive on onion causing foliar necrosis and onion center rot, previous genomic analysis has shown that lacks the primary virulence secretion systems associated with other plant pathogens. We assessed a collection of fifty strains collected from Georgia over three decades to determine genetic factors that correlated with onion pathogenic potential.

Pattern-Triggered Immunity Alters the Transcriptional Regulation of Virulence-Associated Genes and Induces the Sulfur Starvation Response in Pseudomonas syringae pv. tomato DC3000.

Pattern-triggered immunity (PTI) can confer broad defense against diverse microbes and pathogens with disparate lifestyles through the detection of microbial extracellular signatures by surface-exposed pattern recognition receptors. However, unlike recognition of pathogen effectors by cytosolic resistance proteins, PTI is typically not associated with a host-cell programmed cell death response. Although host PTI signaling has been extensively studied, the mechanisms by which it restricts microbial colonization are poorly understood.