scholarly journals Ralstonia solanacearum Requires PopS, an Ancient AvrE-Family Effector, for Virulence and To Overcome Salicylic Acid-Mediated Defenses during Tomato Pathogenesis

mBio ◽  
2013 ◽  
Vol 4 (6) ◽  
Author(s):  
Jonathan M. Jacobs ◽  
Annett Milling ◽  
Raka M. Mitra ◽  
Clifford S. Hogan ◽  
Florent Ailloud ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Bacterial Wilt ◽  
Ralstonia Solanacearum ◽  
Species Complex ◽  
Plant Defenses ◽  
Natural Infection ◽  
Wild Type ◽  
Tomato Plants ◽  
Content Type ◽  
Type Iii

ABSTRACTDuring bacterial wilt of tomato, the plant pathogen Ralstonia solanacearum upregulates expression ofpopS, which encodes a type III-secreted effector in the AvrE family. PopS is a core effector present in all sequenced strains in theR. solanacearumspecies complex. The phylogeny ofpopSmirrors that of the species complex as a whole, suggesting that this is an ancient, vertically inherited effector needed for association with plants. ApopSmutant ofR. solanacearumUW551 had reduced virulence on agriculturally importantSolanumspp., including potato and tomato plants. However, thepopSmutant had wild-type virulence on a weed host,Solanum dulcamara, suggesting that some species can avoid the effects of PopS. ThepopSmutant was also significantly delayed in colonization of tomato stems compared to the wild type. Some AvrE-type effectors from gammaproteobacteria suppress salicylic acid (SA)-mediated plant defenses, suggesting that PopS, a betaproteobacterial ortholog, has a similar function. Indeed, thepopSmutant induced significantly higher expression of tomato SA-triggered pathogenesis-related (PR) genes than the wild type. Further, pretreatment of roots with SA exacerbated thepopSmutant virulence defect. Finally, thepopSmutant had no colonization defect on SA-deficient NahG transgenic tomato plants. Together, these results indicate that this conserved effector suppresses SA-mediated defenses in tomato roots and stems, which areR. solanacearum’s natural infection sites. Interestingly, PopS did not trigger necrosis when heterologously expressed inNicotianaleaf tissue, unlike the AvrE homolog DspEPccfrom the necrotrophPectobacterium carotovorumsubsp.carotovorum. This is consistent with the differing pathogenesis modes of necrosis-causing gammaproteobacteria and biotrophicR. solanacearum.IMPORTANCEThe type III-secreted AvrE effector family is widely distributed in high-impact plant-pathogenic bacteria and is known to suppress plant defenses for virulence. We characterized the biology of PopS, the only AvrE homolog made by the bacterial wilt pathogenRalstonia solanacearum. To our knowledge, this is the first study ofR. solanacearumeffector function in roots and stems, the natural infection sites of this pathogen. Unlike the functionally redundantR. solanacearumeffectors studied to date, PopS is required for full virulence and wild-type colonization of two natural crop hosts.R. solanacearumis a biotrophic pathogen that causes a nonnecrotic wilt. Consistent with this, PopS suppressed plant defenses but did not elicit cell death, unlike AvrE homologs from necrosis-causing plant pathogens. We propose that AvrE family effectors have functionally diverged to adapt to the necrotic or nonnecrotic lifestyle of their respective pathogens.

scholarly journals Effects of Combined Application of Potassium Silicate and Salicylic Acid on the Defense Response of Hydroponically Grown Tomato Plants to Ralstonia solanacearum Infection

2021 ◽  
Vol 13 (7) ◽  
pp. 3750
Author(s):  
Ni-Hao Jiang ◽  
Shi-Han Zhang
Keyword(s):  
Salicylic Acid ◽  
Combination Treatment ◽  
Bacterial Wilt ◽  
Ralstonia Solanacearum ◽  
Combined Effects ◽  
Combined Treatments ◽  
Tomato Plants ◽  
Combined Application ◽  
Infected Tomato ◽  
Tomato Bacterial Wilt

Bacterial wilt, caused by soilborne pathogenic bacterium Ralstonia solanacearum, is a serious and widespread disease that affects global tomato production. Both silicon (Si) and salicylic acid (SA) play important roles in enhancing tomato resistance against bacterial wilt, however, their combined effects on the defense responses of infected tomato plants remain unknown. Hence, the combined effects of Si and SA on physiological and biochemical parameters of R. solanacearum-infected tomato plants were investigated. The combination treatment of Si and SA significantly decreased disease incidences, lipoxygenase (LOX) activity and ethylene (ET) production. The combined treatments were more prominent in improving the morphological traits of root systems, such as root length, root surface area, average root diameter and root volume. The activities of polyphenol oxidase (PPO) and peroxidase (POD) and the concentrations of total soluble phenolics (TSPs) and lignin-thioglycolic acid (LTGA) derivatives were significantly increased in the plants with combined treatments. Si in combination with SA could significantly enhance neutral invertase (NI) and acid invertases (AI) activities in the leaves of tomato plants at 3 days post-infection (dpi) compared with application of Si alone. Three defense-related genes, PAL, POD and pathogenesis-related protein 1 (PR1), were significantly induced in Si+SA treatment at 7 dpi when compared with individual application of Si or SA. The expression level of salicylic acid-binding protein 2 (SABP2) was significantly higher for combination treatment when compared with treatment of Si or SA alone. The possible mechanisms involved in the synergistic effects of Si and SA on the control of tomato bacterial wilt were proposed. This study indicates that under hypertonic conditions, the combined application of 2.0 mM potassium silicate (K2SiO3) and 0.5 mM SA had a synergistic effect on the control of tomato bacterial wilt.

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 Ralstonia solanacearum Uses Inorganic Nitrogen Metabolism for Virulence, ATP Production, and Detoxification in the Oxygen-Limited Host Xylem Environment

mBio ◽  
2015 ◽  
Vol 6 (2) ◽  
Author(s):  
Beth L. Dalsing ◽  
Alicia N. Truchon ◽  
Enid T. Gonzalez-Orta ◽  
Annett S. Milling ◽  
Caitilyn Allen
Keyword(s):  
Nitric Oxide ◽  
Bacterial Wilt ◽  
Ralstonia Solanacearum ◽  
Inorganic Nitrogen ◽  
Anaerobic Growth ◽  
Nitrate Respiration ◽  
Nitrogen Species ◽  
Wild Type ◽  
Content Type ◽  
Xylem Fluid

ABSTRACTGenomic data predict that, in addition to oxygen, the bacterial plant pathogenRalstonia solanacearumcan use nitrate (NO3−), nitrite (NO2−), nitric oxide (NO), and nitrous oxide (N2O) as terminal electron acceptors (TEAs). Genes encoding inorganic nitrogen reduction were highly expressed during tomato bacterial wilt disease, when the pathogen grows in xylem vessels. Direct measurements found that tomato xylem fluid was low in oxygen, especially in plants infected by R. solanacearum. Xylem fluid contained ~25 mM NO3−, corresponding to R. solanacearum's optimal NO3−concentration for anaerobic growthin vitro. We tested the hypothesis that R. solanacearum uses inorganic nitrogen species to respire and grow during pathogenesis by making deletion mutants that each lacked a step in nitrate respiration (ΔnarG), denitrification (ΔaniA, ΔnorB, and ΔnosZ), or NO detoxification (ΔhmpX). TheΔnarG,ΔaniA, andΔnorBmutants grew poorly on NO3−compared to the wild type, and they had reduced adenylate energy charge levels under anaerobiosis. While NarG-dependent NO3−respiration directly enhanced growth, AniA-dependent NO2−reduction did not. NO2−and NO inhibited growth in culture, and their removal depended on denitrification and NO detoxification. Thus, NO3−acts as a TEA, but the resulting NO2−and NO likely do not. None of the mutants grew as well as the wild typein planta, and strains lacking AniA (NO2−reductase) or HmpX (NO detoxification) had reduced virulence on tomato. Thus, R. solanacearum exploits host NO3−to respire, grow, and cause disease. Degradation of NO2−and NO is also important for successful infection and depends on denitrification and NO detoxification systems.IMPORTANCEThe plant-pathogenic bacteriumRalstonia solanacearumcauses bacterial wilt, one of the world's most destructive crop diseases. This pathogen's explosive growth in plant vascular xylem is poorly understood. We used biochemical and genetic approaches to show that R. solanacearum rapidly depletes oxygen in host xylem but can then respire using host nitrate as a terminal electron acceptor. The microbe uses its denitrification pathway to detoxify the reactive nitrogen species nitrite (a product of nitrate respiration) and nitric oxide (a plant defense signal). Detoxification may play synergistic roles in bacterial wilt virulence by converting the host's chemical weapon into an energy source. Mutant bacterial strains lacking elements of the denitrification pathway could not grow as well as the wild type in tomato plants, and some mutants were also reduced in virulence. Our results show how a pathogen's metabolic activity can alter the host environment in ways that increase pathogen success.

scholarly journals Trehalose Synthesis Contributes to Osmotic Stress Tolerance and Virulence of the Bacterial Wilt Pathogen Ralstonia solanacearum

2020 ◽  
Vol 33 (3) ◽  
pp. 462-473 ◽  
Author(s):  
April M. MacIntyre ◽  
John X. Barth ◽  
Molly C. Pellitteri Hahn ◽  
Cameron O. Scarlett ◽  
Stéphane Genin ◽  
...  
Keyword(s):  
Osmotic Stress ◽  
Bacterial Wilt ◽  
Ralstonia Solanacearum ◽  
Type Strain ◽  
Wild Type Strain ◽  
Xylem Sap ◽  
Wilt Disease ◽  
Wild Type ◽  
Tomato Plants ◽  
Trehalose Synthesis

The xylem-dwelling plant pathogen Ralstonia solanacearum changes the chemical composition of host xylem sap during bacterial wilt disease. The disaccharide trehalose, implicated in stress tolerance across all kingdoms of life, is enriched in sap from R. solanacearum–infected tomato plants. Trehalose in xylem sap could be synthesized by the bacterium, the plant, or both. To investigate the source and role of trehalose metabolism during wilt disease, we evaluated the effects of deleting the three trehalose synthesis pathways in the pathogen: TreYZ, TreS, and OtsAB, as well as its sole trehalase, TreA. A quadruple treY/treS/otsA/treA mutant produced 30-fold less intracellular trehalose than the wild-type strain missing the trehalase enzyme. This trehalose-nonproducing mutant had reduced tolerance to osmotic stress, which the bacterium likely experiences in plant xylem vessels. Following naturalistic soil-soak inoculation of tomato plants, this triple mutant did not cause disease as well as wild-type R. solanacearum. Further, the wild-type strain out-competed the trehalose-nonproducing mutant by over 600-fold when tomato plants were coinoculated with both strains, showing that trehalose biosynthesis helps R. solanacearum overcome environmental stresses during infection. An otsA (trehalose-6-phosphate synthase) single mutant behaved similarly to ΔtreY/treS/otsA in all experimental settings, suggesting that the OtsAB pathway is the dominant trehalose synthesis pathway in R. solanacearum.

scholarly journals The eggplant AG91-25 recognizes the Type III-secreted effector RipAX2 to trigger resistance to bacterial wilt (Ralstonia solanacearum species complex)

2018 ◽  
Vol 19 (11) ◽  
pp. 2459-2472 ◽  
Author(s):  
Arry Morel ◽  
Jérémy Guinard ◽  
Fabien Lonjon ◽  
Lakshmi Sujeeun ◽  
Patrick Barberis ◽  
...  
Keyword(s):  
Bacterial Wilt ◽  
Ralstonia Solanacearum ◽  
Species Complex ◽  
Type Iii

scholarly journals Ralstonia solanacearum Needs Motility for Invasive Virulence on Tomato

2001 ◽  
Vol 183 (12) ◽  
pp. 3597-3605 ◽  
Author(s):  
Julie Tans-Kersten ◽  
Huayu Huang ◽  
Caitilyn Allen
Keyword(s):  
Bacterial Wilt ◽  
Ralstonia Solanacearum ◽  
Soft Agar ◽  
Cell Protein ◽  
In Planta ◽  
Tomato Plants ◽  
Bacterial Wilt Disease ◽  
Virulence Assay ◽  
Flagellar Filament

ABSTRACT Ralstonia solanacearum, a widely distributed and economically important plant pathogen, invades the roots of diverse plant hosts from the soil and aggressively colonizes the xylem vessels, causing a lethal wilting known as bacterial wilt disease. By examining bacteria from the xylem vessels of infected plants, we found thatR. solanacearum is essentially nonmotile in planta, although it can be highly motile in culture. To determine the role of pathogen motility in this disease, we cloned, characterized, and mutated two genes in the R. solanacearum flagellar biosynthetic pathway. The genes for flagellin, the subunit of the flagellar filament (fliC), and for the flagellar motor switch protein (fliM) were isolated based on their resemblance to these proteins in other bacteria. As is typical for flagellins, the predicted FliC protein had well-conserved N- and C-terminal regions, separated by a divergent central domain. The predicted R. solanacearum FliM closely resembled motor switch proteins from other proteobacteria. Chromosomal mutants lackingfliC or fliM were created by replacing the genes with marked interrupted constructs. Since fliM is embedded in the fliLMNOPQR operon, the aphAcassette was used to make a nonpolar fliM mutation. Both mutants were completely nonmotile on soft agar plates, in minimal broth, and in tomato plants. The fliC mutant lacked flagella altogether; moreover, sheared-cell protein preparations from the fliC mutant lacked a 30-kDa band corresponding to flagellin. The fliM mutant was usually aflagellate, but about 10% of cells had abnormal truncated flagella. In a biologically representative soil-soak inoculation virulence assay, both nonmotile mutants were significantly reduced in the ability to cause disease on tomato plants. However, the fliC mutant had wild-type virulence when it was inoculated directly onto cut tomato petioles, an inoculation method that did not require bacteria to enter the intact host from the soil. These results suggest that swimming motility makes its most important contribution to bacterial wilt virulence in the early stages of host plant invasion and colonization.

scholarly journals Method-Dependent Epidemiological Cutoff Values for Detection of Triazole Resistance in Candida and Aspergillus Species for the Sensititre YeastOne Colorimetric Broth and Etest Agar Diffusion Methods

2018 ◽  
Vol 63 (1) ◽  
Author(s):  
A. Espinel-Ingroff ◽  
J. Turnidge ◽  
A. Alastruey-Izquierdo ◽  
F. Botterel ◽  
E. Canton ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Species Complex ◽  
Susceptibility Testing ◽  
Yeast Species ◽  
Sensu Stricto ◽  
Wild Type ◽  
Pichia Kudriavzevii ◽  
Cutoff Value ◽  
Content Type ◽  
Clavispora Lusitaniae

ABSTRACT Although the Sensititre Yeast-One (SYO) and Etest methods are widely utilized, interpretive criteria are not available for triazole susceptibility testing of Candida or Aspergillus species. We collected fluconazole, itraconazole, posaconazole, and voriconazole SYO and Etest MICs from 39 laboratories representing all continents for (method/agent-dependent) 11,171 Candida albicans, 215 C. dubliniensis, 4,418 C. glabrata species complex, 157 C. guilliermondii (Meyerozyma guilliermondii), 676 C. krusei (Pichia kudriavzevii), 298 C. lusitaniae (Clavispora lusitaniae), 911 C. parapsilosis sensu stricto, 3,691 C. parapsilosis species complex, 36 C. metapsilosis, 110 C. orthopsilosis, 1,854 C. tropicalis, 244 Saccharomyces cerevisiae, 1,409 Aspergillus fumigatus, 389 A. flavus, 130 A. nidulans, 233 A. niger, and 302 A. terreus complex isolates. SYO/Etest MICs for 282 confirmed non-wild-type (non-WT) isolates were included: ERG11 (C. albicans), ERG11 and MRR1 (C. parapsilosis), cyp51A (A. fumigatus), and CDR2 and CDR1 overexpression (C. albicans and C. glabrata, respectively). Interlaboratory modal agreement was superior by SYO for yeast species and by the Etest for Aspergillus spp. Distributions fulfilling CLSI criteria for epidemiological cutoff value (ECV) definition were pooled, and we proposed SYO ECVs for S. cerevisiae and 9 yeast and 3 Aspergillus species and Etest ECVs for 5 yeast and 4 Aspergillus species. The posaconazole SYO ECV of 0.06 µg/ml for C. albicans and the Etest itraconazole ECV of 2 µg/ml for A. fumigatus were the best predictors of non-WT isolates. These findings support the need for method-dependent ECVs, as, overall, the SYO appears to perform better for susceptibility testing of yeast species and the Etest appears to perform better for susceptibility testing of Aspergillus spp. Further evaluations should be conducted with more Candida mutants.

scholarly journals Selection and Inheritance of Tomato Resistance against Ralstonia solanacearum

2019 ◽  
Vol 23 (1) ◽  
pp. 61
Author(s):  
Isna Maulida ◽  
Rudi Hari Murti ◽  
Triwidodo Arwiyanto
Keyword(s):  
Bacterial Wilt ◽  
Ralstonia Solanacearum ◽  
Dominant Gene ◽  
Tomato Plants ◽  
Breeding Lines ◽  
Back Cross ◽  
Inheritance Patterns ◽  
Randomized Design ◽  
Resistant Varieties ◽  
Resistant Lines

Ralstonia solanacearum is a plant pathogen causes wilting which is a major obstacle in the cultivation of tomato plants. In plant breeding, knowledge of the source of resistance genes and inheritance patterns is important in the development of bacterial wilt resistant varieties. This study aimed to obtain bacterial wilt resistant lines and to find out the inheritance pattern of tomato resistance to bacterial wilt. Selection of resistant plant involved the selected breeding lines from irradiation and crossing collections of the Genetic Laboratory, Faculty of Agriculture, Universitas Gadjah Mada. Introduced lines of H-7996 and F1 Permata and Timoti were used as a control. H-7996 as resistant parents and GM2 as susceptible parents, and their offspring include F1 GM2 x H-7996, F1 reciprocal, F2, Back Cross 1 (F1 x GM2), and Back Cross 2 (F1 x H-7996) used in testing inheritance patterns. Inoculation was carried out 1 week after planting by pouring 100 ml of water suspension of R. solanacarum (108  cfu/ml) on the roots. Completely Randomized Design (CRD) was used in this experiment. The scoring observation was carried out every week for one month. This study showed that Permata as a control was the most resistant, while Timoti and H-7996 were medium resistant. The CLN, G6, G8, and G7 lines were susceptible medium, yet only G8 and G7 with the smallest percentage of disease intensity and not significantly different than Timoti. The resistance gene to bacterial wilt on H-7996 was controlled by genes in the cell nucleus with additive-dominant gene action. Resistance to bacteria has a moderate level of heritability.

scholarly journals Resistance and Susceptibility of Arabidopsis thaliana to Bacterial Wilt Caused by Ralstonia solanacearum

1998 ◽  
Vol 88 (4) ◽  
pp. 330-334 ◽  
Author(s):  
Chang-Hsien Yang ◽  
Gan-Der Ho
Keyword(s):  
Arabidopsis Thaliana ◽  
Bacterial Wilt ◽  
Ralstonia Solanacearum ◽  
Bacterial Colonization ◽  
Plant Diseases ◽  
Infection Site ◽  
Bacterial Isolation ◽  
Tomato Plants ◽  
Different Strains ◽  
Growth Of Bacteria

Tomato bacterial wilt caused by Ralstonia solanacearum is a model system for studying plant-bacterial interactions, because it is genetically one of the best characterized plant diseases. We demonstrate here that four different strains of R. solanacearum, two from radishes (Rd4 and Rd15) and two from tomato (Ps21 and Ps95), can infect 27 different ecotypes of Arabidopsis thaliana, causing different responses. All ecotypes tested were highly susceptible to strain Rd15, which caused symptoms similar to those observed in tomato plants. For example, leaf drooping and discoloration developed just 3 days after inoculation, and plants completely wilted within 1 week. Strains Rd4 and Ps95 were less infectious than Rd15. With these two strains, a variety of disease responses were observed among different ecotypes at 2 weeks after inoculation; both susceptible and resistant ecotypes of A. thaliana were identified. Ps21 was the least infectious of the four strains and caused almost no symptoms in any of the ecotypes of Arabidopsis tested. Direct bacterial isolation and plant skeleton hybridization analysis from infected plants indicated that bacterial colonization was correlated with the severity of symptoms. Growth of bacteria was limited to the infection site in resistant plants, whereas the bacteria spread throughout susceptible plants by 1 week after inoculation.

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