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1.
PLoS Biol ; 17(11): e3000534, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31721759

RESUMO

Phosphate starvation response (PSR) in nonmycorrhizal plants comprises transcriptional reprogramming resulting in severe physiological changes to the roots and shoots and repression of plant immunity. Thus, plant-colonizing microorganisms-the plant microbiota-are exposed to direct influence by the soil's phosphorus (P) content itself as well as to the indirect effects of soil P on the microbial niches shaped by the plant. The individual contribution of these factors to plant microbiota assembly remains unknown. To disentangle these direct and indirect effects, we planted PSR-deficient Arabidopsis mutants in a long-term managed soil P gradient and compared the composition of their shoot and root microbiota to wild-type plants across different P concentrations. PSR-deficiency had a larger effect on the composition of both bacterial and fungal plant-associated microbiota than soil P concentrations in both roots and shoots. To dissect plant-microbe interactions under variable P conditions, we conducted a microbiota reconstitution experiment. Using a 185-member bacterial synthetic community (SynCom) across a wide P concentration gradient in an agar matrix, we demonstrated a shift in the effect of bacteria on the plant from a neutral or positive interaction to a negative one, as measured by rosette size. This phenotypic shift was accompanied by changes in microbiota composition: the genus Burkholderia was specifically enriched in plant tissue under P starvation. Through a community drop-out experiment, we demonstrated that in the absence of Burkholderia from the SynCom, plant shoots accumulated higher ortophosphate (Pi) levels than shoots colonized with the full SynCom but only under Pi starvation conditions. Therefore, Pi-stressed plants are susceptible to colonization by latent opportunistic competitors found within their microbiome, thus exacerbating the plant's Pi starvation.


Assuntos
Arabidopsis/microbiologia , Fósforo/análise , Solo/química , Arabidopsis/metabolismo , Burkholderia/fisiologia , Microbiota , Fósforo/metabolismo , Raízes de Plantas/metabolismo , Raízes de Plantas/microbiologia , Brotos de Planta/metabolismo , Brotos de Planta/microbiologia , Estresse Fisiológico
2.
Proc Natl Acad Sci U S A ; 116(6): 2364-2373, 2019 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-30674663

RESUMO

In nature, plants must respond to multiple stresses simultaneously, which likely demands cross-talk between stress-response pathways to minimize fitness costs. Here we provide genetic evidence that biotic and abiotic stress responses are differentially prioritized in Arabidopsis thaliana leaves of different ages to maintain growth and reproduction under combined biotic and abiotic stresses. Abiotic stresses, such as high salinity and drought, blunted immune responses in older rosette leaves through the phytohormone abscisic acid signaling, whereas this antagonistic effect was blocked in younger rosette leaves by PBS3, a signaling component of the defense phytohormone salicylic acid. Plants lacking PBS3 exhibited enhanced abiotic stress tolerance at the cost of decreased fitness under combined biotic and abiotic stresses. Together with this role, PBS3 is also indispensable for the establishment of salt stress- and leaf age-dependent phyllosphere bacterial communities. Collectively, our work reveals a mechanism that balances trade-offs upon conflicting stresses at the organism level and identifies a genetic intersection among plant immunity, leaf microbiota, and abiotic stress tolerance.


Assuntos
Reguladores de Crescimento de Plantas/metabolismo , Folhas de Planta/metabolismo , Plantas/metabolismo , Transdução de Sinais , Estresse Fisiológico , Arabidopsis/genética , Arabidopsis/imunologia , Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas , Desenvolvimento Vegetal/genética , Desenvolvimento Vegetal/imunologia , Imunidade Vegetal , Plantas/genética , Plantas/imunologia , Reprodução , Fatores de Transcrição/metabolismo
3.
Plant Cell Physiol ; 62(2): 248-261, 2021 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-33475132

RESUMO

The Casparian strip (CS) constitutes a physical diffusion barrier to water and nutrients in plant roots, which is formed by the polar deposition of lignin polymer in the endodermis tissue. The precise pattern of lignin deposition is determined by the scaffolding activity of membrane-bound Casparian Strip domain proteins (CASPs), but little is known of the mechanism(s) directing this process. Here, we demonstrate that Endodermis-specific Receptor-like Kinase 1 (ERK1) and, to a lesser extent, ROP Binding Kinase1 (RBK1) are also involved in regulating CS formation, with the former playing an essential role in lignin deposition as well as in the localization of CASP1. We show that ERK1 is localized to the cytoplasm and nucleus of the endodermis and that together with the circadian clock regulator, Time for Coffee (TIC), forms part of a novel signaling pathway necessary for correct CS organization and suberization of the endodermis, with their single or combined loss of function resulting in altered root microbiome composition. In addition, we found that other mutants displaying defects in suberin deposition at the CS also display altered root exudates and microbiome composition. Thus, our work reveals a complex network of signaling factors operating within the root endodermis that establish both the CS diffusion barrier and influence the microbial composition of the rhizosphere.


Assuntos
Arabidopsis/metabolismo , Microbiota , Raízes de Plantas/metabolismo , Rizosfera , Transdução de Sinais , Proteínas de Arabidopsis/metabolismo , Proteínas Nucleares/metabolismo , Raízes de Plantas/microbiologia , Transdução de Sinais/fisiologia
4.
Artigo em Inglês | MEDLINE | ID: mdl-33351739

RESUMO

A phylogenomic analysis based on 107 single-copy core genes revealed that three strains from sugar-rich environments, i.e. LMG 1728T, LMG 1731 and LMG 22058, represented a single, novel Gluconacetobacter lineage with Gluconacetobacter liquefaciens as nearest validly named neighbour. OrthoANIu and digital DNA-DNA hybridization analyses among these strains and Gluconacetobacter type strains confirmed that the three strains represented a novel Gluconacetobacter species. Biochemical characteristics and MALDI-TOF mass spectra allowed differentiation of this novel species from the type strains of G. liquefaciens and other closely related Gluconacetobacter species. We therefore propose to classify strains LMG 1728T, LMG 1731 and LMG 22058 in the novel species Gluconacetobacter dulcium sp. nov., with LMG 1728T (=CECT 30142T) as the type strain.


Assuntos
Ananas/microbiologia , Gluconacetobacter/classificação , Filogenia , Técnicas de Tipagem Bacteriana , Composição de Bases , DNA Bacteriano/genética , Ácidos Graxos/química , Tamanho do Genoma , Gluconacetobacter/isolamento & purificação , Hibridização de Ácido Nucleico , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Açúcares
5.
Nature ; 528(7582): 364-9, 2015 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-26633631

RESUMO

Roots and leaves of healthy plants host taxonomically structured bacterial assemblies, and members of these communities contribute to plant growth and health. We established Arabidopsis leaf- and root-derived microbiota culture collections representing the majority of bacterial species that are reproducibly detectable by culture-independent community sequencing. We found an extensive taxonomic overlap between the leaf and root microbiota. Genome drafts of 400 isolates revealed a large overlap of genome-encoded functional capabilities between leaf- and root-derived bacteria with few significant differences at the level of individual functional categories. Using defined bacterial communities and a gnotobiotic Arabidopsis plant system we show that the isolates form assemblies resembling natural microbiota on their cognate host organs, but are also capable of ectopic leaf or root colonization. While this raises the possibility of reciprocal relocation between root and leaf microbiota members, genome information and recolonization experiments also provide evidence for microbiota specialization to their respective niche.


Assuntos
Arabidopsis/microbiologia , Microbiota/fisiologia , Folhas de Planta/microbiologia , Raízes de Plantas/microbiologia , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Genoma Bacteriano/genética , Vida Livre de Germes , Microbiota/genética , Análise de Sequência de DNA , Microbiologia do Solo
6.
Proc Natl Acad Sci U S A ; 115(39): E9145-E9152, 2018 09 25.
Artigo em Inglês | MEDLINE | ID: mdl-30201727

RESUMO

Plants differ from animals in their capability to easily regenerate fertile adult individuals from terminally differentiated cells. This unique developmental plasticity is commonly observed in nature, where many species can reproduce asexually through the ectopic initiation of organogenic or embryogenic developmental programs. While organ-specific epigenetic marks are not passed on during sexual reproduction, the fate of epigenetic marks during asexual reproduction and the implications for clonal progeny remain unclear. Here we report that organ-specific epigenetic imprints in Arabidopsis thaliana can be partially maintained during asexual propagation from somatic cells in which a zygotic program is artificially induced. The altered marks are inherited even over multiple rounds of sexual reproduction, becoming fixed in hybrids and resulting in heritable molecular and physiological phenotypes that depend on the identity of the founder tissue. Consequently, clonal plants display distinct interactions with beneficial and pathogenic microorganisms. Our results demonstrate how novel phenotypic variation in plants can be unlocked through altered inheritance of epigenetic marks upon asexual propagation.


Assuntos
Arabidopsis/metabolismo , Epigênese Genética/fisiologia , Técnicas de Embriogênese Somática de Plantas , Reprodução Assexuada/fisiologia , Arabidopsis/citologia , Arabidopsis/genética
7.
Curr Microbiol ; 75(10): 1408-1418, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29980814

RESUMO

Indole-3-acetic acid (IAA) is one of the most important molecules produced by Azospirillum sp., given that it affects plant growth and development. Azospirillum brasilense strains Sp245 and Az39 (pFAJ64) were pre-incubated in MMAB medium plus 100 mg/mL L-tryptophan and treated with or exposed to the following (a) abiotic and (b) biotic stress effectors: (a) 100 mM NaCl or Na2SO4, 4.0% (w/v) PEG6000, 0.5 mM H2O2, 0.1 mM abscisic acid, 0.1 mM 1-aminocyclopropane 1-carboxylic acid, 45 °C or daylight, and (b) 4.0% (v/v) filtered supernatant of Pseudomonas savastanoi (Ps) or Fusarium oxysporum (Fo), 0.1 mM salicylic acid (SA), 0.1 mM methyl jasmonic acid (MeJA), and 0.01% (w/v) chitosan (CH). After 30 and 120 min of incubation, biomass production, cell viability, IAA concentration (µg/mL), and ipdC gene expression were measured. Our results show that IAA production increases with daylight or in the presence of PEG6000, ABA, SA, CH, and Fo. On the contrary, exposure to 45 °C or treatment with H2O2, NaCl, Na2SO4, ACC, MeJA, and Ps decrease IAA biosynthesis. In this report, growth and IAA biosynthesis in A. brasilense under biotic and abiotic stress conditions are discussed from the point of view of their role in bacterial lifestyle and their potential application as bioproducts.


Assuntos
Azospirillum brasilense/genética , Regulação Bacteriana da Expressão Gênica , Ácidos Indolacéticos/metabolismo , Reguladores de Crescimento de Plantas/biossíntese , Azospirillum brasilense/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Meios de Cultura/química , Meios de Cultura/metabolismo , Triptofano/metabolismo
8.
Arch Microbiol ; 199(3): 513-517, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28070613

RESUMO

The use of plant growth-promoting rhizobacteria as a sustainable alternative for chemical nitrogen fertilizers has been explored for many economically important crops. For one such strain isolated from rice rhizosphere and endosphere, nitrogen-fixing Pseudomonas stutzeri A15, unequivocal evidence of the plant growth-promoting effect and the potential contribution of biological nitrogen fixation (BNF) is still lacking. In this study, we investigated the effect of P. stutzeri A15 inoculation on the growth of rice seedlings in greenhouse conditions. P. stutzeri A15 induced significant growth promotion compared to uninoculated rice seedlings. Furthermore, inoculation with strain A15 performed significantly better than chemical nitrogen fertilization, clearly pointing to the potential of this bacterium as biofertilizer. To assess the contribution of BNF to the plant growth-promoting effect, rice seedlings were also inoculated with a nitrogen fixation-deficient mutant. Our results suggest that BNF (at best) only partially contributes to the stimulation of plant growth.


Assuntos
Fixação de Nitrogênio/fisiologia , Oryza/microbiologia , Pseudomonas stutzeri/fisiologia , Endófitos/fisiologia , Mutação , Nitrogênio/farmacologia , Fixação de Nitrogênio/efeitos dos fármacos , Fixação de Nitrogênio/genética , Desenvolvimento Vegetal/efeitos dos fármacos , Desenvolvimento Vegetal/fisiologia , Raízes de Plantas/microbiologia
9.
BMC Plant Biol ; 15: 195, 2015 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-26264238

RESUMO

BACKGROUND: Plant growth-promoting rhizobacteria are increasingly being seen as a way of complementing conventional inputs in agricultural systems. The effects on their host plants are diverse and include volatile-mediated growth enhancement. This study sought to assess the effects of bacterial volatiles on the biomass production and root system architecture of the model grass Brachypodium distachyon (L.) Beauv. RESULTS: An in vitro experiment allowing plant-bacteria interaction throughout the gaseous phase without any physical contact was used to screen 19 bacterial strains for their growth-promotion ability over a 10-day co-cultivation period. Five groups of bacteria were defined and characterised based on their combined influence on biomass production and root system architecture. The observed effects ranged from unchanged to greatly increased biomass production coupled with increased root length and branching. Primary root length was increased only by the volatile compounds emitted by Enterobacter cloacae JM22 and Bacillus pumilus T4. Overall, the most significant results were obtained with Bacillus subtilis GB03, which induced an 81 % increase in total biomass, as well as enhancing total root length, total secondary root length and total adventitious root length by 88.5, 201.5 and 474.5 %, respectively. CONCLUSIONS: This study is the first report on bacterial volatile-mediated growth promotion of a grass plant. Contrasting modulations of biomass production coupled with changes in root system architecture were observed. Most of the strains that increased total plant biomass also modulated adventitious root growth. Under our screening conditions, total biomass production was strongly correlated with the length and branching of the root system components, except for primary root length. An analysis of the emission kinetics of the bacterial volatile compounds is being undertaken and should lead to the identification of the compounds responsible for the observed growth-promotion effects. Within the context of the inherent characteristics of our in vitro system, this paper identifies the next critical experimental steps and discusses them from both a fundamental and an applied perspective.


Assuntos
Bactérias/metabolismo , Biomassa , Brachypodium/anatomia & histologia , Brachypodium/crescimento & desenvolvimento , Compostos Orgânicos Voláteis/metabolismo , Brachypodium/microbiologia , Raízes de Plantas/anatomia & histologia , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/microbiologia , Rizosfera
10.
PLoS Pathog ; 9(2): e1003199, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23468636

RESUMO

Lectin-like bacteriotoxic proteins, identified in several plant-associated bacteria, are able to selectively kill closely related species, including several phytopathogens, such as Pseudomonas syringae and Xanthomonas species, but so far their mode of action remains unrevealed. The crystal structure of LlpABW, the prototype lectin-like bacteriocin from Pseudomonas putida, reveals an architecture of two monocot mannose-binding lectin (MMBL) domains and a C-terminal ß-hairpin extension. The C-terminal MMBL domain (C-domain) adopts a fold very similar to MMBL domains from plant lectins and contains a binding site for mannose and oligomannosides. Mutational analysis indicates that an intact sugar-binding pocket in this domain is crucial for bactericidal activity. The N-terminal MMBL domain (N-domain) adopts the same fold but is structurally more divergent and lacks a functional mannose-binding site. Differential activity of engineered N/C-domain chimers derived from two LlpA homologues with different killing spectra, disclosed that the N-domain determines target specificity. Apparently this bacteriocin is assembled from two structurally similar domains that evolved separately towards dedicated functions in target recognition and bacteriotoxicity.


Assuntos
Antibacterianos/química , Toxinas Bacterianas/química , Bacteriocinas/química , Pseudomonas putida/metabolismo , Antibacterianos/metabolismo , Antibacterianos/farmacologia , Toxinas Bacterianas/metabolismo , Bacteriocinas/metabolismo , Bacteriocinas/farmacologia , Dicroísmo Circular , Cristalização , Análise Mutacional de DNA , DNA Bacteriano/análise , DNA Recombinante , Testes de Sensibilidade Microbiana , Ligação Proteica , Estrutura Terciária de Proteína , Pseudomonas putida/genética , Relação Estrutura-Atividade , Especificidade por Substrato
11.
Crit Rev Microbiol ; 41(1): 109-23, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23855358

RESUMO

Cell surface display of proteins can be used for several biotechnological applications such as the screening of protein libraries, whole cell biocatalysis and live vaccine development. Amongst all secretion systems and surface appendages of Gram-negative bacteria, the autotransporter secretion pathway holds great potential for surface display because of its modular structure and apparent simplicity. Autotransporters are polypeptides made up of an N-terminal signal peptide, a secreted or surface-displayed passenger domain and a membrane-anchored C-terminal translocation unit. Genetic replacement of the passenger domain allows for the surface display of heterologous passengers. An autotransporter-based surface expression module essentially consists of an application-dependent promoter system, a signal peptide, a passenger domain of interest and the autotransporter translocation unit. The passenger domain needs to be compatible with surface translocation although till now no general rules have been determined to test this compatibility. The autotransporter technology for surface display of heterologous passenger domains is critically discussed for various applications.


Assuntos
Sistemas de Secreção Bacterianos , Biotecnologia/métodos , Técnicas de Visualização da Superfície Celular/métodos , Bactérias Gram-Negativas , Proteínas da Membrana Bacteriana Externa , Biodegradação Ambiental , Modelos Moleculares , Proteínas Recombinantes , Vacinas Sintéticas
12.
BMC Plant Biol ; 14: 11, 2014 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-24401128

RESUMO

BACKGROUND: Solanum lycopersicum or tomato is extensively studied with respect to the ethylene metabolism during climacteric ripening, focusing almost exclusively on fruit pericarp. In this work the ethylene biosynthesis pathway was examined in all major tomato fruit tissues: pericarp, septa, columella, placenta, locular gel and seeds. The tissue specific ethylene production rate was measured throughout fruit development, climacteric ripening and postharvest storage. All ethylene intermediate metabolites (1-aminocyclopropane-1-carboxylic acid (ACC), malonyl-ACC (MACC) and S-adenosyl-L-methionine (SAM)) and enzyme activities (ACC-oxidase (ACO) and ACC-synthase (ACS)) were assessed. RESULTS: All tissues showed a similar climacteric pattern in ethylene productions, but with a different amplitude. Profound differences were found between tissue types at the metabolic and enzymatic level. The pericarp tissue produced the highest amount of ethylene, but showed only a low ACC content and limited ACS activity, while the locular gel accumulated a lot of ACC, MACC and SAM and showed only limited ACO and ACS activity. Central tissues (septa, columella and placenta) showed a strong accumulation of ACC and MACC. These differences indicate that the ethylene biosynthesis pathway is organized and regulated in a tissue specific way. The possible role of inter- and intra-tissue transport is discussed to explain these discrepancies. Furthermore, the antagonistic relation between ACO and E8, an ethylene biosynthesis inhibiting protein, was shown to be tissue specific and developmentally regulated. In addition, ethylene inhibition by E8 is not achieved by a direct interaction between ACO and E8, as previously suggested in literature. CONCLUSIONS: The Ethylene biosynthesis pathway and E8 show a tissue specific and developmental differentiation throughout tomato fruit development and ripening.


Assuntos
Etilenos/metabolismo , Solanum lycopersicum/metabolismo , Aminoácido Oxirredutases/metabolismo , Aminoácidos Cíclicos/metabolismo , Regulação da Expressão Gênica de Plantas , Liases/metabolismo , Solanum lycopersicum/fisiologia
13.
New Phytol ; 201(3): 850-861, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-24219779

RESUMO

The auxin-producing bacterium Azospirillum brasilense Sp245 can promote the growth of several plant species. The model plant Arabidopsis thaliana was chosen as host plant to gain an insight into the molecular mechanisms that govern this interaction. The determination of differential gene expression in Arabidopsis roots after inoculation with either A. brasilense wild-type or an auxin biosynthesis mutant was achieved by microarray analysis. Arabidopsis thaliana inoculation with A. brasilense wild-type increases the number of lateral roots and root hairs, and elevates the internal auxin concentration in the plant. The A. thaliana root transcriptome undergoes extensive changes on A. brasilense inoculation, and the effects are more pronounced at later time points. The wild-type bacterial strain induces changes in hormone- and defense-related genes, as well as in plant cell wall-related genes. The A. brasilense mutant, however, does not elicit these transcriptional changes to the same extent. There are qualitative and quantitative differences between A. thaliana responses to the wild-type A. brasilense strain and the auxin biosynthesis mutant strain, based on both phenotypic and transcriptomic data. This illustrates the major role played by auxin in the Azospirillum-Arabidopsis interaction, and possibly also in other bacterium-plant interactions.


Assuntos
Arabidopsis/genética , Arabidopsis/microbiologia , Azospirillum brasilense/metabolismo , Ácidos Indolacéticos/metabolismo , Raízes de Plantas/anatomia & histologia , Raízes de Plantas/microbiologia , Análise por Conglomerados , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Ontologia Genética , Mutação/genética , Análise de Sequência com Séries de Oligonucleotídeos , Fenótipo , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Transdução de Sinais/genética
14.
Appl Environ Microbiol ; 78(8): 2533-42, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22307303

RESUMO

Autotransporters are a widespread family of proteins, generally known as virulence factors produced by Gram-negative bacteria. In this study, the esterase A (EstA) autotransporter of the rice root-colonizing beneficial bacterium Pseudomonas stutzeri A15 was characterized. A multiple sequence alignment identified EstA as belonging to clade II of the GDSL esterase family. Autologous overexpression allowed the investigation of several features of both autotransporter proteins and GDSL esterases. First, the correctly folded autotransporter was shown to be present in the membrane fraction. Unexpectedly, after separation of the membrane fraction, EstA was detected in the N-laurylsarcosine soluble fraction. However, evidence is presented for the surface exposure of EstA based on fluorescent labeling with EstA specific antibodies. Another remarkable feature is the occurrence of a C-terminal leucine residue instead of the canonical phenylalanine or tryptophan residue. Replacement of this residue with a phenylalanine residue reduced the stability of the ß-barrel. Regarding the esterase passenger domain, we show the importance of the catalytic triad residues, with the serine and histidine residues being more critical than the aspartate residue. Furthermore, the growth of an estA-negative mutant was not impaired and cell mobility was not disabled compared to the wild type. No specific phenotype was detected for an estA-negative mutant. Overall, P. stutzeri A15 EstA is a new candidate for the surface display of proteins in environmentally relevant biotechnological applications.


Assuntos
Proteínas de Bactérias/metabolismo , Hidrolases de Éster Carboxílico/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Pseudomonas stutzeri/enzimologia , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Proteínas de Bactérias/isolamento & purificação , Hidrolases de Éster Carboxílico/genética , Hidrolases de Éster Carboxílico/isolamento & purificação , Membrana Celular/química , Análise por Conglomerados , Proteínas de Membrana Transportadoras/genética , Proteínas de Membrana Transportadoras/isolamento & purificação , Filogenia , Pseudomonas stutzeri/genética , Alinhamento de Sequência
15.
Microb Cell Fact ; 11: 158, 2012 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-23237539

RESUMO

BACKGROUND: Autotransporters represent a widespread family of secreted proteins in Gram-negative bacteria. Their seemingly easy secretion mechanism and modular structure make them interesting candidates for cell surface display of heterologous proteins. The most widely applied host organism for this purpose is Escherichia coli. Pseudomonas stutzeri A15 is an interesting candidate host for environmentally relevant biotechnological applications. With the recently characterized P. stutzeri A15 EstA autotransporter at hand, all tools for developing a surface display system for environmental use are available. More general, this system could serve as a case-study to test the broad applicability of autotransporter based surface display. RESULTS: Based on the P. stutzeri A15 EstA autotransporter ß-domain, a surface display expression module was constructed for use in P. stutzeri A15. Proof of concept of this module was presented by successful surface display of the original EstA passenger domain, which retained its full esterase activity. Almost all of the tested heterologous passenger domains however were not exposed at the cell surface of P. stutzeri A15, as assessed by whole cell proteinase K treatment. Only for a beta-lactamase protein, cell surface display in P. stutzeri A15 was comparable to presentation of the original EstA passenger domain. Development of expression modules based on the full-length EstA autotransporter did not resolve these problems. CONCLUSIONS: Since only one of the tested heterologous passenger proteins could be displayed at the cell surface of P. stutzeri A15 to a notable extent, our results indicate that the EstA autotransporter cannot be regarded as a broad spectrum cell surface display system in P. stutzeri A15.


Assuntos
Proteínas de Bactérias/genética , Hidrolases de Éster Carboxílico/genética , Membrana Celular/enzimologia , Pseudomonas stutzeri/enzimologia , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Hidrolases de Éster Carboxílico/química , Hidrolases de Éster Carboxílico/metabolismo , Membrana Celular/química , Membrana Celular/genética , Expressão Gênica , Estrutura Terciária de Proteína , Transporte Proteico , Pseudomonas stutzeri/química , Pseudomonas stutzeri/genética
16.
mBio ; 13(2): e0258421, 2022 04 26.
Artigo em Inglês | MEDLINE | ID: mdl-35258335

RESUMO

Plant roots are colonized by microorganisms from the surrounding soil that belong to different kingdoms and form a multikingdom microbial community called the root microbiota. Despite their importance for plant growth, the relationship between soil management, the root microbiota, and plant performance remains unknown. Here, we characterize the maize root-associated bacterial, fungal, and oomycetal communities during the vegetative and reproductive growth stages of four maize inbred lines and the pht1;6 phosphate transporter mutant. These plants were grown in two long-term experimental fields under four contrasting soil managements, including phosphate-deficient and -sufficient conditions. We showed that the maize root-associated microbiota is influenced by soil management and changes during host growth stages. We identified stable bacterial and fungal root-associated taxa that persist throughout the host life cycle. These taxa were accompanied by dynamic members that covary with changes in root metabolites. We observed an inverse stable-to-dynamic ratio between root-associated bacterial and fungal communities. We also found a host footprint on the soil biota, characterized by a convergence between soil, rhizosphere, and root bacterial communities during reproductive maize growth. Our study reveals the spatiotemporal dynamics of the maize root-associated microbiota and suggests that the fungal assemblage is less responsive to changes in root metabolites than the bacterial community. IMPORTANCE Plant roots are inhabited by microbial communities called the root microbiota, which supports plant growth and health. We show in a maize field study that the root microbiota consists of stable and dynamic members. The dynamics of the microbial community appear to be driven by changes in the metabolic state of the roots over the life cycle of maize.


Assuntos
Microbiota , Zea mays , Bactérias , Fungos/genética , Raízes de Plantas/microbiologia , Plantas , Solo , Microbiologia do Solo , Zea mays/microbiologia
17.
Microb Ecol ; 61(4): 723-8, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21340736

RESUMO

The rhizosphere bacterium Azospirillum brasilense produces the auxin indole-3-acetic acid (IAA) through the indole-3-pyruvate pathway. As we previously demonstrated that transcription of the indole-3-pyruvate decarboxylase (ipdC) gene is positively regulated by IAA, produced by A. brasilense itself or added exogenously, we performed a microarray analysis to study the overall effects of IAA on the transcriptome of A. brasilense. The transcriptomes of A. brasilense wild-type and the ipdC knockout mutant, both cultured in the absence and presence of exogenously added IAA, were compared.Interfering with the IAA biosynthesis/homeostasis in A. brasilense through inactivation of the ipdC gene or IAA addition results in much broader transcriptional changes than anticipated. Based on the multitude of changes observed by comparing the different transcriptomes, we can conclude that IAA is a signaling molecule in A. brasilense. It appears that the bacterium, when exposed to IAA, adapts itself to the plant rhizosphere, by changing its arsenal of transport proteins and cell surface proteins. A striking example of adaptation to IAA exposure, as happens in the rhizosphere, is the upregulation of a type VI secretion system (T6SS) in the presence of IAA. The T6SS is described as specifically involved in bacterium-eukaryotic host interactions. Additionally, many transcription factors show an altered regulation as well, indicating that the regulatory machinery of the bacterium is changing.


Assuntos
Azospirillum brasilense/genética , Azospirillum brasilense/metabolismo , Perfilação da Expressão Gênica , Ácidos Indolacéticos/metabolismo , Rizosfera , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica , Dados de Sequência Molecular
18.
Plant Direct ; 5(1): e00296, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33532689

RESUMO

BACKGROUND: Mineral phosphorus (P) fertilizers must be used wisely in order to preserve rock phosphate, a limited and non-renewable resource. The use of bio-inoculants to improve soil nutrient availability and trigger an efficient plant response to nutrient deficiency is one potential strategy in the attempt to decrease P inputs in agriculture. METHOD: An in vitro co-cultivation system was used to study the response of Brachypodium distachyon to contrasted P supplies (soluble and poorly soluble forms of P) and inoculation with P solubilizing bacteria. Brachypodium's responses to P conditions and inoculation with bacteria were studied in terms of developmental plasticity and P use efficiency. RESULTS: Brachypodium showed plasticity in its biomass allocation pattern in response to variable P conditions, specifically by prioritizing root development over shoot productivity under poorly soluble P conditions. Despite the ability of the bacteria to solubilize P, shoot productivity was depressed in plants inoculated with bacteria, although the root system development was maintained. The negative impact of bacteria on biomass production in Brachypodium might be attributed to inadequate C supply to bacteria, an increased competition for P between both organisms under P-limiting conditions, or an accumulation of toxic bacterial metabolites in our cultivation system. Both P and inoculation treatments impacted root system morphology. The modulation of Brachypodium's developmental response to P supplies by P solubilizing bacteria did not lead to improved P use efficiency. CONCLUSION: Our results support the hypothesis that plastic responses of Brachypodium cultivated under P-limited conditions are modulated by P solubilizing bacteria. The considered experimental context impacts plant-bacteria interactions. Choosing experimental conditions as close as possible to real ones is important in the selection of P solubilizing bacteria. Both persistent homology and allometric analyses proved to be useful tools that should be considered when studying the impact of bio-inoculants on plant development in response to varying nutritional context.

19.
Res Microbiol ; 172(3): 103814, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33539931

RESUMO

Bradyrhizobium japonicum E109 is a bacterium widely used for inoculants production in Argentina. It is known for its ability to produce several phytohormones and degrade indole-3-acetic acid (IAA). The genome sequence of B. japonicum E109 was recently analyzed and it showed the presence of genes related to the synthesis of IAA by indole-3-acetonitrile, indole-3-acetamide and tryptamine pathways. Nevertheless, B. japonicum E109 is not able to produce IAA and instead has the ability to degrade this hormone under saprophytic culture conditions. This work aimed to study the molecular and physiological features of IAA degradation and identify the genes responsible of this activity. In B. japonicum E109 we identified two sequences coding for a putative 3-phenylpropionate dioxygenase (subunits α and ß) responsible for the IAA degradation that were homologous to the canonical cluster of iacC and iacD of Pseudomonas putida 1290. These genes form a separate cluster together with three additional genes with unknown functions. The degradation activity was found to be constitutively expressed in B. japonicum E109. As products of IAA degradation, we identified two compounds, 3-indoleacetic acid 2,3-oxide and 2-(2-hydroperoxy-3-hydroxyindolin-3-yl) acetic acid. Our report proposes, for the first time, a model for IAA degradation in Bradyrhizobium.


Assuntos
Bradyrhizobium/genética , Bradyrhizobium/metabolismo , Ácidos Indolacéticos/metabolismo , Redes e Vias Metabólicas/genética , Indóis/metabolismo , Triptaminas/metabolismo
20.
FEMS Microbiol Rev ; 31(4): 425-48, 2007 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-17509086

RESUMO

Diverse bacterial species possess the ability to produce the auxin phytohormone indole-3-acetic acid (IAA). Different biosynthesis pathways have been identified and redundancy for IAA biosynthesis is widespread among plant-associated bacteria. Interactions between IAA-producing bacteria and plants lead to diverse outcomes on the plant side, varying from pathogenesis to phyto-stimulation. Reviewing the role of bacterial IAA in different microorganism-plant interactions highlights the fact that bacteria use this phytohormone to interact with plants as part of their colonization strategy, including phyto-stimulation and circumvention of basal plant defense mechanisms. Moreover, several recent reports indicate that IAA can also be a signaling molecule in bacteria and therefore can have a direct effect on bacterial physiology. This review discusses past and recent data, and emerging views on IAA, a well-known phytohormone, as a microbial metabolic and signaling molecule.


Assuntos
Bactérias/metabolismo , Bactérias/patogenicidade , Ácidos Indolacéticos/metabolismo , Desenvolvimento Vegetal , Doenças das Plantas/microbiologia , Transdução de Sinais , Bactérias/genética , Bactérias/crescimento & desenvolvimento , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica , Reguladores de Crescimento de Plantas/metabolismo , Plantas/metabolismo , Plantas/microbiologia
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