scholarly journals A genome-wide screen identifies genes in rhizosphere-associatedPseudomonasrequired to evade plant defenses

2018 ◽  
Author(s):  
Zhexian Liu ◽  
Polina Beskrovnaya ◽  
Ryan A. Melnyk ◽  
Sarzana S. Hossain ◽  
Sophie Khorasani ◽  
...  
Keyword(s):  
Plant Growth ◽  
Biofilm Formation ◽  
Plant Defenses ◽  
Plant Root ◽  
Plant Health ◽  
Wild Type ◽  
Host Immune Responses ◽  
A Genome ◽  
Dependent Inhibition ◽  
Bacterial Genes

AbstractPseudomonas fluorescensand related plant root- (“rhizosphere”) associated species contribute to plant health by modulating defenses and facilitating nutrient uptake. To identify bacterial fitness determinants in the rhizosphere of the model plantArabidopsis thaliana, we performed a Tn-Seq screen using the biocontrol and growth-promoting strainPseudomonassp. WCS365. The screen, which was performed in parallel on wild-type and an immunocompromisedArabidopsis, identified 231 genes that positively affect fitness in the rhizosphere of wild-type plants. A subset of these genes negatively affect fitness in the rhizosphere of immunocompromised plants. We postulated that these genes might be involved in avoiding plant defenses and verified 7Pseudomonassp. WCS365 candidate genes by generating clean deletions. We found that two of these deletion strains, ΔmorA(encodes a putative diguanylate cyclase/phosphodiesterase) and ΔspuC(encodes a putrescine aminotransferase) formed enhanced biofilms and inhibited plant growth. Inhibition of plant growth by ΔspuCand ΔmorAwas the result of pattern triggered immunity (PTI) as measured by induction of anArabidopsisPTI reporter andFLS2/BAK1-dependent inhibition of plant growth. We found that MorA acts as a phosphodiesterase to inhibit biofilm formation suggesting a possible role in biofilm dispersal. We found that both putrescine and its precursor arginine promote biofilm formation that is enhanced in the ΔspuCmutant, which cannot break down putrescine suggesting that putrescine might serve as a signaling molecule in the rhizosphere. Collectively, this work identified novel bacterial factors required to evade plant defenses in the rhizosphere.ImportanceWhile rhizosphere bacteria hold the potential to improve plant health and fitness, little is known about the bacterial genes required to evade host immunity. Using a model system consisting ofArabidopsisand a beneficialPseudomonassp. isolate, we identified bacterial genes required for both rhizosphere fitness and for evading host immune responses. This work advances our understanding of how evasion of host defenses contributes to survival in the rhizosphere.

scholarly journals A Genome-Wide Screen Identifies Genes in Rhizosphere-AssociatedPseudomonasRequired to Evade Plant Defenses

mBio ◽  
2018 ◽  
Vol 9 (6) ◽  
Author(s):  
Zhexian Liu ◽  
Polina Beskrovnaya ◽  
Ryan A. Melnyk ◽  
Sarzana S. Hossain ◽  
Sophie Khorasani ◽  
...  
Keyword(s):  
Plant Growth ◽  
Biofilm Formation ◽  
Plant Defenses ◽  
Plant Root ◽  
Plant Health ◽  
Wild Type ◽  
Content Type ◽  
Host Immune Responses ◽  
A Genome ◽  
Bacterial Genes

ABSTRACTPseudomonas fluorescensand related plant root (“rhizosphere”)-associated species contribute to plant health by modulating defenses and facilitating nutrient uptake. To identify bacterial fitness determinants in the rhizosphere of the model plantArabidopsis thaliana, we performed a high-throughput transposon sequencing (Tn-Seq) screen using the biocontrol and growth-promoting strainPseudomonassp. WCS365. The screen, which was performed in parallel on wild-type and immunocompromisedArabidopsisplants, identified 231 genes that increased fitness in the rhizosphere of wild-type plants. A subset of these genes decreased fitness in the rhizosphere of immunocompromised plants. We hypothesized that these genes might be involved in avoiding plant defenses and verified 7Pseudomonassp. WCS365 candidate genes by generating clean deletions. We found that two of these deletion mutants, ΔmorA(encoding a putative diguanylate cyclase/phosphodiesterase) and ΔspuC(encoding a putrescine aminotransferase), formed enhanced biofilms and inhibited plant growth. We found that mutantsΔspuCandΔmorAinduced pattern-triggered immunity (PTI) as measured by induction of anArabidopsisPTI reporter andFLS2/BAK1-dependent inhibition of plant growth. We show that MorA acts as a phosphodiesterase to inhibit biofilm formation, suggesting a possible role in biofilm dispersal. We found that both putrescine and its precursor arginine promote biofilm formation that is enhanced in theΔspuCmutant, which cannot break down putrescine, suggesting that putrescine might serve as a signaling molecule in the rhizosphere. Collectively, this work identified novel bacterial factors required to evade plant defenses in the rhizosphere.IMPORTANCEWhile rhizosphere bacteria hold the potential to improve plant health and fitness, little is known about the bacterial genes required to evade host immunity. Using a model system consisting ofArabidopsisand a beneficialPseudomonassp. isolate, we identified bacterial genes required for both rhizosphere fitness and for evading host immune responses. This work advances our understanding of how evasion of host defenses contributes to survival in the rhizosphere.

scholarly journals Inactivation of Genes Encoding MutL and MutS Proteins Influences Adhesion and Biofilm Formation by Neisseria gonorrhoeae

2019 ◽  
Vol 7 (12) ◽  
pp. 647 ◽  
Author(s):  
Jagoda Płaczkiewicz ◽  
Monika Adamczyk-Popławska ◽  
Robert Lasek ◽  
Pawel Bącal ◽  
Agnieszka Kwiatek
Keyword(s):  
Epithelial Cells ◽  
Neisseria Gonorrhoeae ◽  
Biofilm Formation ◽  
Dna Microarrays ◽  
Wild Type ◽  
Human Genes ◽  
Genes Encoding ◽  
Differential Gene ◽  
Bacterial Genes ◽  
Muts Gene

Neisseria gonorrhoeae is an etiological agent of gonorrhea, which remains a global health problem. This bacterium possesses MutL and MutS DNA repair proteins encoded by mutL and mutS genes, whose inactivation causes a mutator phenotype. We have demonstrated the differential gene expression in N. gonorrhoeae mutL and mutS mutants using DNA microarrays. A subset of differentially expressed genes encodes proteins that can influence adhesion and biofilm formation. Compared to the wild-type strain, N. gonorrhoeae mutL and mutS mutants formed denser biofilms with increased biofilm-associated biomass on the abiotic surface. The N. gonorrhoeae mutS::km, but not the mutL mutant, was also more adherent and invasive to human epithelial cells. Further, during infection of epithelial cells with N. gonorrhoeae mutS::km, the expression of some bacterial genes encoding proteins that can influence gonococcal adhesion was changed compared with their expression in cells infected with the wild-type gonococcus, as well as of human genes’ encoding receptors utilized by N. gonorrhoeae (CD46, CEACAM 1, HSPG 2). Thus, deficiency in the mutS gene resulting in increased mutation frequency in singular organisms can be beneficial in populations because these mutants can be a source of features linked to microbial fitness.

scholarly journals Role of Pseudomonas putida Indoleacetic Acid in Development of the Host Plant Root System

2002 ◽  
Vol 68 (8) ◽  
pp. 3795-3801 ◽  
Author(s):  
Cheryl L. Patten ◽  
Bernard R. Glick
Keyword(s):  
Plant Growth ◽  
Pseudomonas Putida ◽  
Host Plant ◽  
Root System ◽  
Indoleacetic Acid ◽  
Plant Root ◽  
Deficient Mutant ◽  
Wild Type ◽  
Acid Pathway ◽  
Plant Root System

ABSTRACT Many plant-associated bacteria synthesize the phytohormone indoleacetic acid (IAA). While IAA produced by phytopathogenic bacteria, mainly by the indoleacetamide pathway, has been implicated in the induction of plant tumors, it is not clear whether IAA synthesized by beneficial bacteria, usually via the indolepyruvic acid pathway, is involved in plant growth promotion. To determine whether bacterial IAA enhances root development in host plants, the ipdc gene that encodes indolepyruvate decarboxylase, a key enzyme in the indolepyruvic acid pathway, was isolated from the plant growth-promoting bacterium Pseudomonas putida GR12-2 and an IAA-deficient mutant constructed by insertional mutagenesis. The canola seedling primary roots from seeds treated with wild-type P. putida GR12-2 were on average 35 to 50% longer than the roots from seeds treated with the IAA-deficient mutant and the roots from uninoculated seeds. In addition, exposing mung bean cuttings to high levels of IAA by soaking them in a suspension of the wild-type strain stimulated the formation of many, very small, adventitious roots. Formation of fewer roots was stimulated by treatment with the IAA-deficient mutant. These results suggest that bacterial IAA plays a major role in the development of the host plant root system.

Plant Growth Promoting Bacteria (PGPB) - A Versatile Tool for Plant Health Management

2019 ◽  
Vol 1 (1) ◽  
pp. 1
Author(s):  
Salah Eddin Khabbaz ◽  
D. Ladhalakshmi ◽  
Merin Babu ◽  
A. Kandan ◽  
V. Ramamoorthy ◽  
...  
Keyword(s):  
Plant Growth ◽  
Health Management ◽  
Plant Health ◽  
Plant Growth Promoting Bacteria ◽  
Versatile Tool ◽  
Plant Growth Promoting ◽  
Growth Promoting

scholarly journals C4 Bacterial Volatiles Improve Plant Health

Pathogens ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 682
Author(s):  
Bruno Henrique Silva Dias ◽  
Sung-Hee Jung ◽  
Juliana Velasco de Castro Oliveira ◽  
Choong-Min Ryu
Keyword(s):  
Plant Growth ◽  
Volatile Compounds ◽  
Large Scale ◽  
Growth Promotion ◽  
Plant Growth Promoting Rhizobacteria ◽  
Plant Health ◽  
Systemic Resistance ◽  
Potential Applications ◽  
Plant Growth Promoting ◽  
Bacterial Volatiles

Plant growth-promoting rhizobacteria (PGPR) associated with plant roots can trigger plant growth promotion and induced systemic resistance. Several bacterial determinants including cell-wall components and secreted compounds have been identified to date. Here, we review a group of low-molecular-weight volatile compounds released by PGPR, which improve plant health, mostly by protecting plants against pathogen attack under greenhouse and field conditions. We particularly focus on C4 bacterial volatile compounds (BVCs), such as 2,3-butanediol and acetoin, which have been shown to activate the plant immune response and to promote plant growth at the molecular level as well as in large-scale field applications. We also disc/ uss the potential applications, metabolic engineering, and large-scale fermentation of C4 BVCs. The C4 bacterial volatiles act as airborne signals and therefore represent a new type of biocontrol agent. Further advances in the encapsulation procedure, together with the development of standards and guidelines, will promote the application of C4 volatiles in the field.

scholarly journals Modified Monosaccharides Content of Xanthan Gum Impairs Citrus Canker Disease by Affecting the Epiphytic Lifestyle of Xanthomonas citri subsp. citri

2021 ◽  
Vol 9 (6) ◽  
pp. 1176
Author(s):  
Simone Cristina Picchi ◽  
Laís Moreira Granato ◽  
Maria Júlia Festa Franzini ◽  
Maxuel Oliveira Andrade ◽  
Marco Aurélio Takita ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Xanthan Gum ◽  
Wild Type Strain ◽  
Natural Infection ◽  
Citrus Canker ◽  
Wild Type ◽  
Xanthomonas Citri ◽  
Canker Disease ◽  
Key Enzyme ◽  
Citrus Canker Disease

Xanthomonas citri subsp. citri (X. citri) is a plant pathogenic bacterium causing citrus canker disease. The xanA gene encodes a phosphoglucomutase/phosphomannomutase protein that is a key enzyme required for the synthesis of lipopolysaccharides and exopolysaccharides in Xanthomonads. In this work, firstly we isolated a xanA transposon mutant (xanA::Tn5) and analyzed its phenotypes as biofilm formation, xanthan gum production, and pathogenesis on the sweet orange host. Moreover, to confirm the xanA role in the impaired phenotypes we further produced a non-polar deletion mutant (ΔxanA) and performed the complementation of both xanA mutants. In addition, we analyzed the percentages of the xanthan gum monosaccharides produced by X. citri wild-type and xanA mutant. The mutant strain had higher ratios of mannose, galactose, and xylose and lower ratios of rhamnose, glucuronic acid, and glucose than the wild-type strain. Such changes in the saccharide composition led to the reduction of xanthan yield in the xanA deficient strain, affecting also other important features in X. citri, such as biofilm formation and sliding motility. Moreover, we showed that xanA::Tn5 caused no symptoms on host leaves after spraying, a method that mimetics the natural infection condition. These results suggest that xanA plays an important role in the epiphytical stage on the leaves that is essential for the successful interaction with the host, including adaptive advantage for bacterial X. citri survival and host invasion, which culminates in pathogenicity.

scholarly journals Genomic characterization and computational phenotyping of nitrogen-fixing bacteria isolated from Colombian sugarcane fields

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Luz K. Medina-Cordoba ◽  
Aroon T. Chande ◽  
Lavanya Rishishwar ◽  
Leonard W. Mayer ◽  
Lina C. Valderrama-Aguirre ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Nitrogen Fixation ◽  
Plant Growth ◽  
Phosphate Solubilization ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
Promising Tool ◽  
A Genome ◽  
Plant Growth Promoting ◽  
Growth Promoting

AbstractPrevious studies have shown the sugarcane microbiome harbors diverse plant growth promoting microorganisms, including nitrogen-fixing bacteria (diazotrophs), which can serve as biofertilizers. The genomes of 22 diazotrophs from Colombian sugarcane fields were sequenced to investigate potential biofertilizers. A genome-enabled computational phenotyping approach was developed to prioritize sugarcane associated diazotrophs according to their potential as biofertilizers. This method selects isolates that have potential for nitrogen fixation and other plant growth promoting (PGP) phenotypes while showing low risk for virulence and antibiotic resistance. Intact nitrogenase (nif) genes and operons were found in 18 of the isolates. Isolates also encode phosphate solubilization and siderophore production operons, and other PGP genes. The majority of sugarcane isolates showed uniformly low predicted virulence and antibiotic resistance compared to clinical isolates. Six strains with the highest overall genotype scores were experimentally evaluated for nitrogen fixation, phosphate solubilization, and the production of siderophores, gibberellic acid, and indole acetic acid. Results from the biochemical assays were consistent and validated computational phenotype predictions. A genotypic and phenotypic threshold was observed that separated strains by their potential for PGP versus predicted pathogenicity. Our results indicate that computational phenotyping is a promising tool for the assessment of bacteria detected in agricultural ecosystems.

scholarly journals Deletion of Rap‐Phr systems in Bacillus subtilis influences in vitro biofilm formation and plant root colonization

2021 ◽  
Vol 10 (3) ◽  
Author(s):  
Mathilde Nordgaard ◽  
Rasmus Møller Rosenbek Mortensen ◽  
Nikolaj Kaae Kirk ◽  
Ramses Gallegos‐Monterrosa ◽  
Ákos T. Kovács
Keyword(s):  
Bacillus Subtilis ◽  
Biofilm Formation ◽  
Root Colonization ◽  
Plant Root
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