scholarly journals Swimming Motility, a Virulence Trait of Ralstonia solanacearum, Is Regulated by FlhDC and the Plant Host Environment

2004 ◽  
Vol 17 (6) ◽  
pp. 686-695 ◽  
Author(s):  
Julie Tans-Kersten ◽  
Darby Brown ◽  
Caitilyn Allen
Keyword(s):  
Ralstonia Solanacearum ◽  
Expression Patterns ◽  
Bacterial Motility ◽  
Wild Type ◽  
In Planta ◽  
Plant Host ◽  
Host Environment ◽  
Swimming Motility ◽  
Flic Gene ◽  
Plant Pathogenesis

Swimming motility allows the bacterial wilt pathogen Ralstonia solanacearum to efficiently invade and colonize host plants. However, the bacteria are essentially nonmotile once inside plant xylem vessels. To determine how and when motility genes are expressed, we cloned and mutated flhDC, which encodes a major regulator of flagellar biosynthesis and bacterial motility. An flhDC mutant was non-motile and less virulent than its wild-type parent on both tomato and Arabidopsis; on Arabidopsis, the flhDC mutant also was less virulent than a nonmotile fliC flagellin mutant. Genes in the R. solanacearum motility regulon had strikingly different expression patterns in culture and in the plant. In culture, as expected, flhDC expression depended on PehSR, a regulator of early virulence factors; and, in turn, FlhDC was required for fliC (flagellin) expression. However, when bacteria grew in tomato plants, flhDC was expressed in both wild-type and pehR mutant backgrounds, although PehSR is necessary for motility both in culture and in planta. Both flhDC and pehSR were significantly induced in planta relative to expression levels in culture. Unexpectedly, the fliC gene was expressed in planta at cell densities where motile bacteria were not observed, as well as in a nonmotile flhDC mutant. Thus, expression of flhDC and flagellin itself are uncoupled from bacterial motility in the host environment, indicating that additional signals and regulatory circuits repress motility during plant pathogenesis.

scholarly journals Ralstonia solanacearum Needs Flp Pili for Virulence on Potato

2012 ◽  
Vol 25 (4) ◽  
pp. 546-556 ◽  
Author(s):  
Charles K. Wairuri ◽  
Jacquie E. van der Waals ◽  
Antoinette van Schalkwyk ◽  
Jacques Theron
Keyword(s):  
Ralstonia Solanacearum ◽  
Type Iv Pili ◽  
Periodontal Pathogen ◽  
Wild Type ◽  
In Planta ◽  
Phytopathogenic Bacterium ◽  
Type Iv ◽  
Plant Pathogenesis

Type IV pili are virulence factors in various bacteria. Several subclasses of type IV pili have been described according to the characteristics of the structural prepilin subunit. Although type IVa pili have been implicated in the virulence of Ralstonia solanacearum, type IVb pili have not previously been described in this plant pathogen. Here, we report the characterization of two distinct tad loci in the R. solanacearum genome. The tad genes encode functions necessary for biogenesis of the Flp subfamily of type IVb pili initially described for the periodontal pathogen Aggregatibacter actinomycetemcomitans. To determine the role of the tad loci in R. solanacearum virulence, we mutated the tadA2 gene located in the megaplasmid that encodes a predicted NTPase previously reported to function as the energizer for Flp pilus biogenesis. Characterization of the tadA2 mutant revealed that it was not growth impaired in vitro or in planta, produced wild-type levels of exopolysaccharide galactosamine, and exhibited swimming and twitching motility comparable with the wild-type strain. However, the tadA2 mutant was impaired in its ability to cause wilting of potato plants. This is the first report where type IVb pili in a phytopathogenic bacterium contribute significantly to plant pathogenesis.

scholarly journals Interactions with Hosts at Cool Temperatures, Not Cold Tolerance, Explain the Unique Epidemiology of Ralstonia solanacearum Race 3 Biovar 2

2009 ◽  
Vol 99 (10) ◽  
pp. 1127-1134 ◽  
Author(s):  
Annett Milling ◽  
Fanhong Meng ◽  
Timothy P. Denny ◽  
Caitilyn Allen
Keyword(s):  
North American ◽  
Ralstonia Solanacearum ◽  
Potato Tubers ◽  
In Planta ◽  
Plant Host ◽  
Tomato Plants ◽  
North American Strain ◽  
Tropical Highlands ◽  
American Strain ◽  
Warm Temperate

Most strains of the bacterial wilt pathogen Ralstonia solanacearum are tropical, but race 3 biovar 2 (R3bv2) strains can attack plants in temperate zones and tropical highlands. The basis of this distinctive ecological trait is not understood. We compared the survival of tropical, R3bv2, and warm-temperate North American strains of R. solanacearum under different conditions. In water at 4°C, North American strains remained culturable the longest (up to 90 days), whereas tropical strains remained culturable for the shortest time (≈40 days). However, live/dead staining indicated that cells of representative strains remained viable for >160 days. In contrast, inside potato tubers, R3bv2 strain UW551 survived >4 months at 4°C, whereas North American strain K60 and tropical strain GMI1000 were undetectable after <70 days in tubers. GMI1000 and UW551 grew similarly in minimal medium at 20 and 28°C and, although both strains wilted tomato plants rapidly at 28°C, UW551 was much more virulent at 20°C, killing all inoculated plants under conditions where GMI100 killed just over half. Thus, differences among the strains in the absence of a plant host were not predictive of their behavior in planta at cooler temperatures. These data indicate that interaction with plants is required for expression of the temperate epidemiological trait of R3bv2.

scholarly journals Role of Extracellular Polysaccharide and Endoglucanase in Root Invasion and Colonization of Tomato Plants by Ralstonia solanacearum

1997 ◽  
Vol 87 (12) ◽  
pp. 1264-1271 ◽  
Author(s):  
Elke Saile ◽  
Jeff A. McGarvey ◽  
Mark A. Schell ◽  
Timothy P. Denny
Keyword(s):  
Ralstonia Solanacearum ◽  
Extracellular Polysaccharide ◽  
Wild Type ◽  
In Planta ◽  
Tomato Plants ◽  
Potted Plants ◽  
Stem Infection ◽  
Soil Infestation ◽  
Plant Stem

Ralstonia solanacearum is a soilborne plant pathogen that normally invades hosts through their roots and then systemically colonizes aerial tissues. Previous research using wounded stem infection found that the major factor in causing wilt symptoms was the high-molecular-mass acidic extracellular polysaccharide (EPS I), but the β-1,4-endoglucanase (EG) also contributes to virulence. We investigated the importance of EPS I and EG for invasion and colonization of tomato by infesting soil of 4-week-old potted plants with either a wild-type derivative or genetically well-defined mutants lacking EPS I, EG, or EPS I and EG. Bacteria of all strains were recovered from surface-disinfested roots and hypocotyls as soon as 4 h after inoculation; that bacteria were present internally was confirmed using immunofluorescence microscopy. However, the EPS-minus mutants did not colonize stems as rapidly as the wild type and the EG-minus mutant. Inoculations of wounded petioles also showed that, even though the mutants multiplied as well as the wild type in planta, EPS-minus strains did not spread as well throughout the plant stem. We conclude that poor colonization of stems by EPS-minus strains after petiole inoculation or soil infestation is due to reduced bacterial movement within plant stem tissues.

scholarly journals Dual Affymetrix GeneChip analysis of the perennial ryegrass-endophyte symbiosis

2007 ◽  
Vol 13 ◽  
pp. 509-513
Author(s):  
L.J. Johnson ◽  
C.R. Voisey ◽  
R.D. Johnson ◽  
A.K. Khan ◽  
Z.A. Park ◽  
...  
Keyword(s):  
Gene Expression ◽  
Perennial Ryegrass ◽  
Biological Interactions ◽  
Wild Type ◽  
In Planta ◽  
Comprehensive Understanding ◽  
Plant Host ◽  
Symbiotic Interactions ◽  
Genechip Analysis

Grass associations with Epichloë/Neotyphodium endophytes display enhanced fitness as well as prolonged field persistence over their endophyte free equivalents. To gain a comprehensive understanding of the complex biological interactions that occur between a plant host and fungal symbiont, a transcriptomics approach using custom designed Affymetrix GeneChip®s was employed. We are currently comparing and analysing symbiotic interactions of perennial ryegrass (Lolium perenne) with endophytes N. lolii and E. festucae as well as comparing it against endophyte-free perennial ryegrass. Both N. lolii and E. festucae have been grown in culture in order to compare in planta versus in vitro gene expression. Additionally, targeted gene replacements in E. festucae have been performed and a comparative analysis of the knock-outs with wild-type E. festucae infected plants is in progress. These comparative analyses have revealed changes in gene expression which may lead to the identification of gene pathways/networks and the roles of these genes in symbiosis. Keywords: Neotyphodium, Epichloë, transcriptomics, symbiosis

scholarly journals Using the Ralstonia solanacearum Tat Secretome To Identify Bacterial Wilt Virulence Factors

2007 ◽  
Vol 73 (12) ◽  
pp. 3779-3786 ◽  
Author(s):  
Enid T. Gonz�lez ◽  
Darby G. Brown ◽  
Jill K. Swanson ◽  
Caitilyn Allen
Keyword(s):  
Virulence Factors ◽  
Bacterial Wilt ◽  
Ralstonia Solanacearum ◽  
Acid Tolerance ◽  
Bioinformatic Analysis ◽  
Wild Type ◽  
In Planta ◽  
Tomato Plants ◽  
Tat System

ABSTRACT To identify secreted virulence factors involved in bacterial wilt disease caused by the phytopathogen Ralstonia solanacearum, we mutated tatC, a key component of the twin-arginine translocation (Tat) secretion system. The R. solanacearum tatC mutation was pleiotropic; its phenotypes included defects in cell division, nitrate utilization, polygalacturonase activity, membrane stability, and growth in plant tissue. Bioinformatic analysis of the R. solanacearum strain GMI1000 genome predicted that this pathogen secretes 70 proteins via the Tat system. The R. solanacearum tatC strain was severely attenuated in its ability to cause disease, killing just over 50% of tomato plants in a naturalistic soil soak assay where the wild-type parent killed 100% of the plants. This result suggested that elements of the Tat secretome may be novel bacterial wilt virulence factors. To identify contributors to R. solanacearum virulence, we cloned and mutated three genes whose products are predicted to be secreted by the Tat system: RSp1521, encoding a predicted AcvB-like protein, and two genes, RSc1651 and RSp1575, that were identified as upregulated in planta by an in vivo expression technology screen. The RSc1651 mutant had wild-type virulence on tomato plants. However, mutants lacking either RSp1521, which appears to be involved in acid tolerance, or RSp1575, which encodes a possible amino acid binding protein, were significantly reduced in virulence on tomato plants. Additional bacterial wilt virulence factors may be found in the Tat secretome.

scholarly journals An Amino Acid Substitution at Position 740 in σ70 of Ralstonia solanacearum Strain OE1-1 Affects Its In Planta Growth

2008 ◽  
Vol 74 (18) ◽  
pp. 5841-5844 ◽  
Author(s):  
Ayami Kanda ◽  
Kazuhiro Tsuneishi ◽  
Ai Mori ◽  
Kouhei Ohnishi ◽  
Akinori Kiba ◽  
...  
Keyword(s):  
Amino Acid ◽  
Amino Acid Substitution ◽  
Ralstonia Solanacearum ◽  
Wild Type ◽  
In Planta ◽  
Solanacearum Strain ◽  
Type Protein ◽  
Wild Type Protein ◽  
Negative Dominance

ABSTRACT Growth of Ralstonia solanacearum strain OE1-1 in roots after invasion is required for virulence. An Arg740Cys substitution in σ70 of OE1-1 resulted in loss of in planta growth and virulence. The negative dominance of mutant σ70 over the wild-type protein suggested that the amino acid substitution may affect the in planta growth of OE1-1, leading to a lack of virulence.

scholarly journals The hrpB and hrpG Regulatory Genes of Ralstonia solanacearum Are Required for Different Stages of the Tomato Root Infection Process

2000 ◽  
Vol 13 (3) ◽  
pp. 259-267 ◽  
Author(s):  
Jacques Vasse ◽  
Stéphane Genin ◽  
Pascal Frey ◽  
Christian Boucher ◽  
Belen Brito
Keyword(s):  
Ralstonia Solanacearum ◽  
Infection Process ◽  
Regulatory Genes ◽  
Wild Type ◽  
Root Infection ◽  
In Planta ◽  
Tomato Root ◽  
Phytopathogenic Bacterium ◽  
Tomato Plants ◽  
Hrp Genes

hrp genes, encoding type III secretion machinery, have been shown to be key determinants for pathogenicity in the vascular phytopathogenic bacterium Ralstonia solanacearum GMI1000. Here, we show phenotypes of R. solanacearum mutant strains disrupted in the prhJ, hrpG, or hrpB regulatory genes with respect to root infection and vascular colonization in tomato plants. Tests of bacterial colonization and enumeration in tomato plants, together with microscopic observations of tomato root sections, revealed that these strains display different phenotypes in planta. The phenotype of a prhJ mutant resembles that of the wild-type strain. An hrpB mutant shows reduced infection, colonization, and multiplication ability in planta, and induces a defense reaction similar to a vascular hypersensitive response at one protoxylem pole of invaded plants. In contrast, the hrpG mutant exhibited a wild-type level of infection at secondary root axils, but the ability of the infecting bacteria to penetrate into the vascular cylinder was significantly impaired. This indicates that bacterial multiplication at root infection sites and transit through the endodermis constitute critical stages in the infection process, in which hrpB and hrpG genes are involved. Moreover, our results suggest that the hrpG gene might control, in addition to hrp genes, other functions required for vascular colonization.

scholarly journals Ralstonia solanacearum depends on catabolism of myo-inositol, sucrose, and trehalose for virulence in an infection stage-dependent manner

2021 ◽  
Author(s):  
Corri D. Hamilton ◽  
Olivia R. Steidl ◽  
April M MacIntyre ◽  
Connor G. Hendrich ◽  
Caitilyn Allen
Keyword(s):  
Cell Density ◽  
Ralstonia Solanacearum ◽  
Xylem Sap ◽  
Carbon Sources ◽  
Dependent Manner ◽  
Wild Type ◽  
In Planta ◽  
Tomato Root ◽  
Catabolic Pathways ◽  
Infection Stage

The soilborne pathogen Ralstonia solanacearum (Rs) causes a lethal bacterial wilt disease of tomato and many other crops by infecting host roots, then colonizing the water-transporting xylem vessels. Tomato xylem sap is nutritionally limiting but it does contain some carbon sources including sucrose, trehalose, and myo-inositol. Transcriptomic analyses revealed that Rs expresses distinct catabolic pathways at low cell density (LCD) and high cell density (HCD). To investigate the links between bacterial catabolism, infection stage, and virulence, we measured in planta fitness of bacterial mutants lacking specific carbon catabolic pathways expressed at either LCD or HCD. We hypothesized that early in disease, during root infection, the bacterium depends on carbon sources catabolized at LCD, while HCD carbon sources are only required later in disease during stem colonization. An Rs ΔiolG mutant unable to use the LCD-catabolized nutrient myo-inositol was defective in tomato root colonization, but after it reached the stem this strain colonized and caused symptoms as well as wild type. In contrast, Rs mutants unable to use the HCD-catabolized nutrients sucrose (ΔscrA), trehalose (ΔtreA), or both (∆scrA/treA) infected roots as well as wild type Rs but were defective in colonization and competitive fitness in mid-stems and had reduced virulence. Further, xylem sap from tomato plants colonized by ΔscrA, ΔtreA, or ΔscrA/treA Rs mutants contained twice as much sucrose as sap from plants colonized by wild-type Rs. Together, these findings suggest that quorum sensing specifically adapts Rs metabolism for success in the different nutritional environments of plant roots and xylem sap.

scholarly journals Chemotaxis Is Required for Virulence and Competitive Fitness of the Bacterial Wilt Pathogen Ralstonia solanacearum

2006 ◽  
Vol 188 (10) ◽  
pp. 3697-3708 ◽  
Author(s):  
Jian Yao ◽  
Caitilyn Allen
Keyword(s):  
Host Plant ◽  
Plant Pathogen ◽  
Ralstonia Solanacearum ◽  
Type Strain ◽  
Wild Type Strain ◽  
Random Motion ◽  
Wild Type ◽  
Tomato Plants ◽  
Swimming Motility ◽  
Directed Motility

ABSTRACT Ralstonia solanacearum, a soilborne plant pathogen of considerable economic importance, invades host plant roots from the soil. Qualitative and quantitative chemotaxis assays revealed that this bacterium is specifically attracted to diverse amino acids and organic acids, and especially to root exudates from the host plant tomato. Exudates from rice, a nonhost plant, were less attractive. Eight different strains from this heterogeneous species complex varied significantly in their attraction to a panel of carbohydrate stimuli, raising the possibility that chemotactic responses may be differentially selected traits that confer adaptation to various hosts or ecological conditions. Previous studies found that an aflagellate mutant lacking swimming motility is significantly reduced in virulence, but the role of directed motility mediated by the chemotaxis system was not known. Two site-directed R. solanacearum mutants lacking either CheA or CheW, which are core chemotaxis signal transduction proteins, were completely nonchemotactic but retained normal swimming motility. In biologically realistic soil soak virulence assays on tomato plants, both nonchemotactic mutants had significantly reduced virulence indistinguishable from that of a nonmotile mutant, demonstrating that directed motility, not simply random motion, is required for full virulence. In contrast, nontactic strains were as virulent as the wild-type strain was when bacteria were introduced directly into the plant stem through a cut petiole, indicating that taxis makes its contribution to virulence in the early stages of host invasion and colonization. When inoculated individually by soaking the soil, both nontactic mutants reached the same population sizes as the wild type did in the stems of tomato plants just beginning to wilt. However, when tomato plants were coinoculated with a 1:1 mixture of a nontactic mutant and its wild-type parent, the wild-type strain outcompeted both nontactic mutants by 100-fold. Together, these results indicate that chemotaxis is an important trait for virulence and pathogenic fitness in this plant pathogen.

Ralstonia solanacearum effectors localize to diverse organelles in Solanum hosts

2021 ◽  
Author(s):  
Nina L. Denne ◽  
Rachel R. Hiles ◽  
Oleksandr Kyrysyuk ◽  
Anjali S. Iyer-Pascuzzi ◽  
Raka M. Mitra
Keyword(s):  
Subcellular Localization ◽  
Ralstonia Solanacearum ◽  
Solanum Species ◽  
Effector Function ◽  
Cell Periphery ◽  
In Planta ◽  
Plant Host ◽  
Phytopathogenic Bacteria ◽  
Ralstonia Pseudosolanacearum ◽  
Cellular Organelles

Phytopathogenic bacteria secrete Type III effector (T3E) proteins directly into host plant cells. T3Es can interact with plant proteins and frequently manipulate plant host physiological or developmental processes. The proper subcellular localization of T3Es is critical for their ability to interact with plant targets, and knowledge of T3E localization can be informative for studies of effector function. Here we investigated the subcellular localization of 19 T3Es from the phytopathogenic bacteria Ralstonia pseudosolanacearum and Ralstonia solanacearum. Approximately 45% of effectors in our library localize to both the plant cell periphery and the nucleus, 15% exclusively to the cell periphery, 15% exclusively to the nucleus, and 25% to other organelles including the tonoplast and peroxisomes. Using tomato hairy roots, we show that T3E localization is similar in both leaves and roots, and is not impacted by Solanum species. We find that in silico prediction programs are frequently inaccurate, highlighting the value of in planta localization experiments. Our data suggest that Ralstonia targets a wide diversity of cellular organelles and provide a foundation for developing testable hypotheses about Ralstonia effector function.

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