Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 2.650
Filtrar
1.
J Environ Sci (China) ; 85: 35-45, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31471029

RESUMO

Imazethapyr (IM) is an acetolactate synthase (ALS)-inhibiting herbicide that has been widely used in recent years. However, IM spraying can lead to the accumulation of herbicide residues in leaves. Here, we determined the effects of IM spraying on the plant growth and leaf surface microbial communities of Arabidopsis thaliana after 7 and 14 days of exposure. The results suggested that IM spraying inhibited plant growth. Fresh weight decreased to 48% and 26% of the control value after 7 and 14 days, respectively, of 0.035 kg/ha IM exposure. In addition, anthocyanin content increased 9.2-fold and 37.2-fold relative to the control content after 7 and 14 days of treatment, respectively. Furthermore, IM spraying destroyed the cell structures of the leaves, as evidenced by increases in the number of starch granules and the stomatal closure rate. Reductions in photosynthetic efficiency and antioxidant enzyme activity were observed after IM spraying, especially after 14 days of exposure. The diversity and evenness of the leaf microbiota were not affected by IM treatment, but the composition of community structure at the genus level was altered by IM spraying. Imazethapyr application increased the abundance of Pseudomonas, a genus that includes species pathogenic to plants and humans, indicating that IM potentially increased the abundance of pathogenic bacteria on leaves. Our findings increase our understanding of the relationships between herbicide application and the microbial community structures on plant leaves, and they provide a new perspective for studying the ecological safety of herbicide usage.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Herbicidas/toxicidade , Microbiota/efeitos dos fármacos , Ácidos Nicotínicos/toxicidade , Folhas de Planta/microbiologia , Arabidopsis/efeitos dos fármacos , Arabidopsis/microbiologia , Folhas de Planta/efeitos dos fármacos
2.
Microbiol Res ; 227: 126297, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31421711

RESUMO

Many plant growth promoting rhizobacteria such as Bacillus velezensis GJ11 can produce acetoin to trigger induced systemic resistance (ISR) in plants. For improving acetoin production, the mutant strains were respectively constructed by knockout of the gene of bdh (2,3-butanediol dehydrogenase) and gdh (glycerol dehydrogenase) in GJ11, but only GJ11Δbdh produced a high level of acetoin triggering strong ISR against Pseudomonas syringae infection in plants. GJ11Δbdh could induce H2O2 accumulation in plants by producing a high level of acetoin. H2O2 was necessary for triggering ISR against the pathogen infection because after scavenging H2O2 with ascorbic acid or catalase, the inhibition role to pathogen infection induced by acetoin almost disappeared in plants. Further investigation found the plants treated with GJ11Δbdh in an obvious "priming" state, in which the mild immune response was observed such as a slight increase of H2O2 production, callose deposition, and enzymes activity related with defence response (e.g. POD, PAL and PPO). The plants in "priming" could rapidly respond to the pathogen infection accompanying with a significant increase of H2O2 production, callose deposition, and enzymes activity. Collectively, this study provides new insight into the role of acetoin as a strong elicitor of defense response, and ascribes a new approach to construct the mutant strains with high production of acetoin for triggering stronger ISR against pathogens infection in plants.


Assuntos
Acetoína/metabolismo , Arabidopsis/genética , Bacillus/genética , Bacillus/metabolismo , Resistência à Doença/genética , Imunidade Vegetal/genética , Oxirredutases do Álcool/genética , Arabidopsis/imunologia , Arabidopsis/microbiologia , Ácido Ascórbico/metabolismo , Catalase/metabolismo , Resistência à Doença/fisiologia , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Técnicas de Inativação de Genes , Genes de Plantas/genética , Peróxido de Hidrogênio/metabolismo , Doenças das Plantas/imunologia , Doenças das Plantas/microbiologia , Imunidade Vegetal/fisiologia , Pseudomonas syringae/patogenicidade , Desidrogenase do Álcool de Açúcar/genética
3.
Plant Mol Biol ; 101(1-2): 149-162, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31267255

RESUMO

KEY MESSAGE: Here we describe that the regulation of MdWRKY31 on MdHIR4 in transcription and translation levels associated with disease in apple. The phytohormone salicylic acid (SA) is a main factor in apple (Malus domestica) production due to its function in disease resistance. WRKY transcription factors play a vital role in response to stress. An RNA-seq analysis was conducted with 'Royal Gala' seedlings treated with SA to identify the WRKY regulatory mechanism of disease resistance in apple. The analysis indicated that MdWRKY31 was induced. A quantitative real-time polymerase chain reaction (qPCR) analysis demonstrated that the expression of MdWRKY31 was induced by SA and flg22. Ectopic expression of MdWRKY31 in Arabidopsis and Nicotiana benthamiana increased the resistance to flg22 and Pseudomonas syringae tomato (Pst DC3000). A yeast two-hybrid screen was conducted to further analyze the function of MdWRKY31. As a result, hypersensitive-induced reaction (HIR) protein MdHIR4 interacted with MdWRKY31. Biomolecular fluorescence complementation, yeast two-hybrid, and pull-down assays demonstrated the interaction. In our previous study, MdHIR4 conferred decreased resistance to Botryosphaeria dothidea (B. dothidea). A viral vector-based transformation assay indicated that MdWRKY31 evaluated the transcription of SA-related genes, including MdPR1, MdPR5, and MdNPR1 in an MdHIR4-dependent way. A GUS analysis demonstrated that the w-box, particularly w-box2, of the MdHIR4 promoter played a major role in the responses to SA and B. dothidea. Electrophoretic mobility shift assays, yeast one-hybrid assay, and chromatin immunoprecipitation-qPCR demonstrated that MdWRKY31 directly bound to the w-box2 motif in the MdHIR4 promoter. GUS staining activity and a protein intensity analysis further showed that MdWRKY31 repressed MdHIR4 expression. Taken together, our findings reveal that MdWRKY31 regulated plant resistance to B. dothidea through the SA signaling pathway by interacting with MdHIR4.


Assuntos
Resistência à Doença , Malus/genética , Doenças das Plantas/imunologia , Reguladores de Crescimento de Planta/farmacologia , Proteínas de Plantas/metabolismo , Ácido Salicílico/farmacologia , Arabidopsis/genética , Arabidopsis/imunologia , Arabidopsis/microbiologia , Ascomicetos/fisiologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Frutas/genética , Frutas/imunologia , Frutas/microbiologia , Regulação da Expressão Gênica de Plantas , Genes Reporter , Malus/imunologia , Malus/microbiologia , Doenças das Plantas/microbiologia , Proteínas de Plantas/genética , Regiões Promotoras Genéticas/genética , Pseudomonas syringae/fisiologia , Plântula/genética , Plântula/imunologia , Plântula/microbiologia , Transdução de Sinais , Tabaco/genética , Tabaco/imunologia , Tabaco/microbiologia , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Técnicas do Sistema de Duplo-Híbrido
4.
Nat Commun ; 10(1): 2886, 2019 06 28.
Artigo em Inglês | MEDLINE | ID: mdl-31253809

RESUMO

Glucosinolates accumulate mainly in cruciferous plants and their hydrolysis-derived products play important roles in plant resistance against pathogens. The pathogen Botrytis cinerea has variable sensitivity to glucosinolates, but the mechanisms by which it responds to them are mostly unknown. Exposure of B. cinerea to glucosinolate-breakdown products induces expression of the Major Facilitator Superfamily transporter, mfsG, which functions in fungitoxic compound efflux. Inoculation of B. cinerea on wild-type Arabidopsis thaliana plants induces mfsG expression to higher levels than on glucosinolate-deficient A. thaliana mutants. A B. cinerea strain lacking functional mfsG transporter is deficient in efflux ability. It accumulates more isothiocyanates (ITCs) and is therefore more sensitive to this compound in vitro; it is also less virulent to glucosinolates-containing plants. Moreover, mfsG mediates ITC efflux in Saccharomyces cerevisiae cells, thereby conferring tolerance to ITCs in the yeast. These findings suggest that mfsG transporter is a virulence factor that increases tolerance to glucosinolates.


Assuntos
Arabidopsis/microbiologia , Botrytis/metabolismo , Regulação Fúngica da Expressão Gênica/fisiologia , Glucosinolatos/química , DNA Complementar , DNA Fúngico , Deleção de Genes , Mutação , Doenças das Plantas/microbiologia , RNA Fúngico , Saccharomyces cerevisiae/metabolismo
5.
Nat Commun ; 10(1): 2543, 2019 06 11.
Artigo em Inglês | MEDLINE | ID: mdl-31186426

RESUMO

The circadian clock is known to regulate plant innate immunity but the underlying mechanism of this regulation remains largely unclear. We show here that mutations in the core clock component LUX ARRHYTHMO (LUX) disrupt circadian regulation of stomata under free running and Pseudomonas syringae challenge conditions as well as defense signaling mediated by SA and JA, leading to compromised disease resistance. RNA-seq analysis reveals that both clock- and defense-related genes are regulated by LUX. LUX binds to clock gene promoters that have not been shown before, expanding the clock gene networks that require LUX function. LUX also binds to the promoters of EDS1 and JAZ5, likely acting through these genes to affect SA- and JA-signaling. We further show that JA signaling reciprocally affects clock activity. Thus, our data support crosstalk between the circadian clock and plant innate immunity and imply an important role of LUX in this process.


Assuntos
Arabidopsis/genética , Relógios Circadianos/genética , Imunidade Vegetal/genética , Arabidopsis/microbiologia , Relógios Circadianos/fisiologia , Resistência à Doença/genética , Regulação da Expressão Gênica de Plantas , Mutação , Doenças das Plantas/imunologia , Doenças das Plantas/microbiologia , Estômatos de Plantas/fisiologia , Pseudomonas syringae/fisiologia , Análise de Sequência de RNA
6.
World J Microbiol Biotechnol ; 35(6): 90, 2019 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-31147784

RESUMO

The ability of plant growth promoting rhizobacteria (PGPR) for imparting abiotic stress tolerance to plants has been widely explored in recent years; however, the diversity and potential of these microbes have not been maximally exploited. In this study, we characterized four bacterial strains, namely, Pseudomonas aeruginosa PM389, Pseudomonas aeruginosa ZNP1, Bacillus endophyticus J13 and Bacillus tequilensis J12, for potential plant growth promoting (PGP) traits under osmotic-stress, induced by 25% polyethylene glycol (PEG) in the growth medium. Growth curve analysis was performed in LB medium with or without PEG, in order to understand the growth patterns of these bacteria under osmotic-stress. All strains were able to grow and proliferate under osmotic-stress, although their growth rate was slower than that under non-stressed conditions (LB without PEG). Bacterial secretions were analyzed for the presence of exopolysaccharides and phytohormones and it was observed that all four strains released these compounds into the media, both, under stressed and non-stressed conditions. In the Pseudomonas strains, osmotic stress caused a decrease in the levels of auxin (IAA) and cytokinin (tZ), but an increase in the levels of gibberellic acid. The Bacillus strains on the other hand showed a stress-induced increase in the levels of all three phytohormones. P. aeruginosa ZNP1 and B. endophyticus J13 exhibited increased EPS production under osmotic-stress. While osmotic stress caused a decrease in the levels of EPS in P. aeruginosa PM389, B. tequilensis J12 showed no change in EPS quantities released into the media under osmotic stress when compared to non-stressed conditions. Upon inoculating Arabidopsis thaliana seedlings with these strains individually, it was observed that all four strains were able to ameliorate the adverse effects of osmotic-stress (induced by 25% PEG in MS-Agar medium) in the plants, as evidenced by their enhanced fresh weight, dry weight and plant water content, as opposed to osmotic-stressed, non-inoculated plants.


Assuntos
Arabidopsis/microbiologia , Fenômenos Fisiológicos Bacterianos , Secas , Pressão Osmótica , Desenvolvimento Vegetal , Reguladores de Crescimento de Planta/metabolismo , Polissacarídeos Bacterianos/metabolismo , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Bacillus/crescimento & desenvolvimento , Bacillus/fisiologia , Bactérias/classificação , Bactérias/crescimento & desenvolvimento , Bactérias/metabolismo , Citocininas/metabolismo , Giberelinas/metabolismo , Ácidos Indolacéticos/metabolismo , Raízes de Plantas/microbiologia , Pseudomonas aeruginosa/crescimento & desenvolvimento , Pseudomonas aeruginosa/fisiologia , Rizosfera , Plântula/crescimento & desenvolvimento , Microbiologia do Solo , Estresse Fisiológico/fisiologia
7.
Mol Plant Microbe Interact ; 32(10): 1303-1313, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31194615

RESUMO

Pipecolic acid (Pip) is an essential component of systemic acquired resistance, priming resistance in Arabidopsis thaliana against (hemi)biotrophic pathogens. Here, we studied the potential role of Pip in bacteria-induced systemic immunity in barley. Exudates of barley leaves infected with the systemic immunity-inducing pathogen Pseudomonas syringae pv. japonica induced immune responses in A. thaliana. The same leaf exudates contained elevated Pip levels compared with those of mock-treated barley leaves. Exogenous application of Pip induced resistance in barley against the hemibiotrophic bacterial pathogen Xanthomonas translucens pv. cerealis. Furthermore, both a systemic immunity-inducing infection and exogenous application of Pip enhanced the resistance of barley against the biotrophic powdery mildew pathogen Blumeria graminis f. sp. hordei. In contrast to a systemic immunity-inducing infection, Pip application did not influence lesion formation by a systemically applied inoculum of the necrotrophic fungus Pyrenophora teres. Nitric oxide (NO) levels in barley leaves increased after Pip application. Furthermore, X. translucens pv. cerealis induced the accumulation of superoxide anion radicals and this response was stronger in Pip-pretreated compared with mock-pretreated plants. Thus, the data suggest that Pip induces barley innate immune responses by triggering NO and priming reactive oxygen species accumulation.


Assuntos
Resistência à Doença , Hordeum , Óxido Nítrico , Ácidos Pipecólicos , Arabidopsis/microbiologia , Resistência à Doença/efeitos dos fármacos , Resistência à Doença/fisiologia , Hordeum/metabolismo , Hordeum/microbiologia , Ácidos Pipecólicos/metabolismo , Ácidos Pipecólicos/farmacologia , Doenças das Plantas/microbiologia , Pseudomonas syringae/fisiologia , Espécies Reativas de Oxigênio/metabolismo , Xanthomonas/fisiologia
8.
Nat Commun ; 10(1): 2853, 2019 06 28.
Artigo em Inglês | MEDLINE | ID: mdl-31253808

RESUMO

Plant innate immunity restricts growth of bacterial pathogens that threaten global food security. However, the mechanisms by which plant immunity suppresses bacterial growth remain enigmatic. Here we show that Arabidopsis thaliana secreted aspartic protease 1 and 2 (SAP1 and SAP2) cleave the evolutionarily conserved bacterial protein MucD to redundantly inhibit the growth of the bacterial pathogen Pseudomonas syringae. Antibacterial activity of SAP1 requires its protease activity in planta and in vitro. Plants overexpressing SAP1 exhibit enhanced MucD cleavage and resistance but incur no penalties in growth and reproduction, while sap1 sap2 double mutant plants exhibit compromised MucD cleavage and resistance against P. syringae. P. syringae lacking mucD shows compromised growth in planta and in vitro. Notably, growth of ΔmucD complemented with the non-cleavable MucDF106Y is not affected by SAP activity in planta and in vitro. Our findings identify the genetic factors and biochemical process underlying an antibacterial mechanism in plants.


Assuntos
Arabidopsis/metabolismo , Arabidopsis/microbiologia , Proteínas de Bactérias/metabolismo , Peptídeo Hidrolases/metabolismo , Doenças das Plantas/microbiologia , Serina Endopeptidases/metabolismo , Arabidopsis/imunologia , Proteínas de Bactérias/genética , Evolução Molecular , Regulação Enzimológica da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Filogenia , Doenças das Plantas/imunologia , Plantas Geneticamente Modificadas , Pseudomonas aeruginosa/enzimologia , Pseudomonas aeruginosa/metabolismo , Serina Endopeptidases/genética
9.
Mol Plant Microbe Interact ; 32(7): 813-827, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31140930

RESUMO

Bacterial wilt caused by the bacterial pathogen Ralstonia solanacearum is one of the most devastating crop diseases worldwide. The molecular mechanisms controlling the early stage of R. solanacearum colonization in the root remain unknown. Aiming to better understand the mechanism of the establishment of R. solanacearum infection in root, we established four stages in the early interaction of the pathogen with Arabidopsis roots and determined the transcriptional profiles of these stages of infection. A total 2,698 genes were identified as differentially expressed genes during the initial 96 h after infection, with the majority of changes in gene expression occurring after pathogen-triggered root-hair development observed. Further analysis of differentially expressed genes indicated sequential activation of multiple hormone signaling cascades, including abscisic acid (ABA), auxin, jasmonic acid, and ethylene. Simultaneous impairment of ABA receptor genes promoted plant wilting symptoms after R. solanacearum infection but did not affect primary root growth inhibition or root-hair and lateral root formation caused by R. solanacearum. This indicated that ABA signaling positively regulates root defense to R. solanacearum. Moreover, transcriptional changes of genes involved in primary root, lateral root, and root-hair formation exhibited high temporal dynamics upon infection. Taken together, our results suggest that successful infection of R. solanacearum on roots is a highly programmed process involving in hormone crosstalk.


Assuntos
Arabidopsis , Ralstonia solanacearum , Transcriptoma , Arabidopsis/genética , Arabidopsis/microbiologia , Sequenciamento de Nucleotídeos em Larga Escala , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Raízes de Plantas/microbiologia , Ralstonia solanacearum/fisiologia
10.
Plant Sci ; 283: 1-10, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31128679

RESUMO

Colletotrichum higginsianum causes anthracnose disease in a wide range of cruciferous crops and has been used as a model system to study plant-pathogen interactions and pathogenicity of hemibiotrophic plant pathogens. Conidiation, hyphae growth, appressorial development and appressorial penetration are significant steps during the infection process of C. higginsianum. However, the mechanisms of these important steps during infection remain incompletely understood. To further investigate the mechanisms of the plant-C. higginsianum interactions during infection progress, we characterized Cyclase-Associated Protein (ChCAP) gene. Deletion of the ChCAP gene resulted in reduction in conidiation and hyphal growth rate. The pathogenicity of ΔChCAP mutants was significantly reduced with much smaller lesion on the infected leaves compared to that of wild type strain with typically water-soaked and dark necrotic lesions on Arabidopsis leaves. Further study demonstrated that the appressorial formation rate, turgor pressure, penetration ability and switch from biotrophic to necrotrophic phases decreased obviously in ΔChCAP mutants, indicating that the attenuated pathogenicity of ΔChCAP mutants was due to these defective phenotypes. In addition, the ΔChCAP mutants sectored on PDA with abnormal, dark color, vesicle-like colony morphology and hyphae tip. Moreover, the ΔChCAP mutants had a reduced intracellular cAMP levels and exogenous cAMP can partially rescue the defects of ΔChCAP mutants in appressorial formation and penetration rate, but not in colony morphology, conidial shape and virulence, indicating that ChCAP is a key component in cAMP signaling pathway and likely play other roles in biology of C. higginsianum. In summary, our findings support the role of ChCAP in regulating conidiation, intracellular cAMP level, hyphal growth, appressorial formation, penetration ability and pathogenicity of this hemibiotrophic fungus.


Assuntos
Colletotrichum/crescimento & desenvolvimento , AMP Cíclico/metabolismo , Proteínas Fúngicas/fisiologia , Hifas/crescimento & desenvolvimento , Esporos Fúngicos/crescimento & desenvolvimento , Arabidopsis/microbiologia , Colletotrichum/metabolismo , Colletotrichum/patogenicidade , Colletotrichum/fisiologia , Proteínas Fúngicas/metabolismo , Hifas/fisiologia , Filogenia , Doenças das Plantas/microbiologia , Reação em Cadeia da Polimerase em Tempo Real , Transdução de Sinais , Esporos Fúngicos/fisiologia , Estresse Fisiológico
11.
Science ; 364(6436): 178-181, 2019 04 12.
Artigo em Inglês | MEDLINE | ID: mdl-30975887

RESUMO

In plants, cell-surface immune receptors sense molecular non-self-signatures. Lipid A of Gram-negative bacterial lipopolysaccharide is considered such a non-self-signature. The receptor kinase LIPOOLIGOSACCHARIDE-SPECIFIC REDUCED ELICITATION (LORE) mediates plant immune responses to Pseudomonas and Xanthomonas but not enterobacterial lipid A or lipopolysaccharide preparations. Here, we demonstrate that synthetic and bacterial lipopolysaccharide-copurified medium-chain 3-hydroxy fatty acid (mc-3-OH-FA) metabolites elicit LORE-dependent immunity. The mc-3-OH-FAs are sensed in a chain length- and hydroxylation-specific manner, with free (R)-3-hydroxydecanoic acid [(R)-3-OH-C10:0] representing the strongest immune elicitor. By contrast, bacterial compounds comprising mc-3-OH-acyl building blocks but devoid of free mc-3-OH-FAs-including lipid A or lipopolysaccharide, rhamnolipids, lipopeptides, and acyl-homoserine-lactones-do not trigger LORE-dependent responses. Hence, plants sense low-complexity bacterial metabolites to trigger immune responses.


Assuntos
Arabidopsis/imunologia , Arabidopsis/microbiologia , Ácidos Decanoicos/metabolismo , Pseudomonas aeruginosa/metabolismo , Acil-Butirolactonas/metabolismo , Ácidos Decanoicos/química , Glicolipídeos/metabolismo , Lipídeo A/metabolismo , Lipopeptídeos/metabolismo
12.
Plant Cell Physiol ; 60(7): 1514-1524, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-30989198

RESUMO

Pathogenic fungi from the genus Colletotrichum form invasive hyphae; the hyphae are surrounded by an extra-invasive hyphal membrane (EIHM), which is continuous with the plant plasma membrane. Although the EIHM plays a crucial role as the interface between plant and fungal cells, its precise function during Colletotrichum infection remains elusive. Here, we show that enrichment of phosphoinositides (PIs) has a crucial role in Colletotrichum infection. We observed the localization of PIs in Arabidopsis thaliana cells infected by A. thaliana-adapted Colletotrichum higginsianum (Ch), and found that phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] was extremely enriched in the EIHM during Ch infection. We also found that phosphatidylinositol 4-phosphate-5 kinase (PIP5K), which catalyzes production of PI(4,5)P2, also accumulated at the EIHM. The overexpression of PIP5K3 in A. thaliana increased hyphal invasion by Ch. An exocytic factor, EXO84b, was targeted to the EIHM during Ch infection, although endocytic factors such as CLATHRIN LIGHT CHAIN 2 and FLOTILLIN 1 did not. Intriguingly, the interfacial membranes between A. thaliana and powdery mildew- or downy mildew-causing pathogens did not accumulate PI(4,5)P2. These results suggest that Ch could modify the PI(4,5)P2 levels in the EIHM to increase the exocytic membrane/protein supply of the EIHM for successful infection. Our results also suggest that PI(4,5)P2 biosynthesis is a promising target for improved defense against Colletotrichum infection.


Assuntos
Arabidopsis/microbiologia , Colletotrichum , Hifas/metabolismo , Fosfatidilinositol 4,5-Difosfato/metabolismo , Doenças das Plantas/microbiologia , Membrana Celular/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Fosfatidilinositol 4,5-Difosfato/fisiologia , Folhas de Planta/microbiologia , Tabaco/microbiologia
13.
Science ; 364(6435)2019 04 05.
Artigo em Inglês | MEDLINE | ID: mdl-30948526

RESUMO

Pathogen recognition by nucleotide-binding (NB), leucine-rich repeat (LRR) receptors (NLRs) plays roles in plant immunity. The Xanthomonas campestris pv. campestris effector AvrAC uridylylates the Arabidopsis PBL2 kinase, and the latter (PBL2UMP) acts as a ligand to activate the NLR ZAR1 precomplexed with the RKS1 pseudokinase. Here we report the cryo-electron microscopy structures of ZAR1-RKS1 and ZAR1-RKS1-PBL2UMP in an inactive and intermediate state, respectively. The ZAR1LRR domain, compared with animal NLRLRR domains, is differently positioned to sequester ZAR1 in an inactive state. Recognition of PBL2UMP is exclusively through RKS1, which interacts with ZAR1LRR PBL2UMP binding stabilizes the RKS1 activation segment, which sterically blocks ZAR1 adenosine diphosphate (ADP) binding. This engenders a more flexible NB domain without conformational changes in the other ZAR1 domains. Our study provides a structural template for understanding plant NLRs.


Assuntos
Difosfato de Adenosina/química , Proteínas de Arabidopsis/química , Arabidopsis/enzimologia , Arabidopsis/microbiologia , Proteínas de Transporte/química , Peptídeos e Proteínas de Sinalização Intracelular/química , Proteínas NLR/química , Fosfoproteínas/química , Proteínas Serina-Treonina Quinases/química , Difosfato de Adenosina/metabolismo , Proteínas de Arabidopsis/metabolismo , Proteínas de Bactérias/metabolismo , Microscopia Crioeletrônica , Ligantes , Núcleosídeo-Fosfato Quinase/metabolismo , Domínios Proteicos , Proteínas Serina-Treonina Quinases/metabolismo , Xanthomonas campestris/enzimologia
14.
Science ; 364(6435)2019 04 05.
Artigo em Inglês | MEDLINE | ID: mdl-30948527

RESUMO

Nucleotide-binding, leucine-rich repeat receptors (NLRs) perceive pathogen effectors to trigger plant immunity. Biochemical mechanisms underlying plant NLR activation have until now remained poorly understood. We reconstituted an active complex containing the Arabidopsis coiled-coil NLR ZAR1, the pseudokinase RKS1, uridylated protein kinase PBL2, and 2'-deoxyadenosine 5'-triphosphate (dATP), demonstrating the oligomerization of the complex during immune activation. The cryo-electron microscopy structure reveals a wheel-like pentameric ZAR1 resistosome. Besides the nucleotide-binding domain, the coiled-coil domain of ZAR1 also contributes to resistosome pentamerization by forming an α-helical barrel that interacts with the leucine-rich repeat and winged-helix domains. Structural remodeling and fold switching during activation release the very N-terminal amphipathic α helix of ZAR1 to form a funnel-shaped structure that is required for the plasma membrane association, cell death triggering, and disease resistance, offering clues to the biochemical function of a plant resistosome.


Assuntos
Difosfato de Adenosina/química , Proteínas de Arabidopsis/química , Arabidopsis/imunologia , Arabidopsis/microbiologia , Proteínas de Transporte/química , Resistência à Doença , Interações Hospedeiro-Patógeno/imunologia , Peptídeos e Proteínas de Sinalização Intracelular/química , Proteínas NLR/química , Fosfoproteínas/química , Proteínas Serina-Treonina Quinases/química , Arabidopsis/enzimologia , Proteínas de Arabidopsis/metabolismo , Proteínas de Bactérias/metabolismo , Microscopia Crioeletrônica , Ligantes , Núcleosídeo-Fosfato Quinase/metabolismo , Domínios Proteicos , Estrutura Secundária de Proteína , Proteínas Serina-Treonina Quinases/metabolismo , Xanthomonas campestris/enzimologia
15.
Mol Plant Microbe Interact ; 32(9): 1188-1195, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30939072

RESUMO

Bacillus subtilis is a Gram-positive plant-growth-promoting rhizobacterium exerting many beneficial effects on plant health. Because they secrete antimicrobial compounds and elicit induced systemic resistance, B. subtilis and phylogenetically related species are of particular interest as antifungals in organic agriculture. These bacteria are also known for their capacity to differentiate phenotypically into endospores able to withstand many environmental stresses. However, although B. subtilis is often inoculated on plants as spores, dynamics of germination and sporulation on roots remain unexplored. Using a hydroponic culture system and a soil system for Arabidopsis thaliana, we observed that B. subtilis spores germinate rapidly on contact with plants. However, the vegetative cells are abundant on roots for only a few days before reversing back to spores. We observed that the germinant receptor GerK and sporulation kinases KinA and KinB identified in vitro control sporulation dynamics on plants. Surprisingly, when plants are inoculated with B. subtilis, free-living cells sporulate more rapidly than plant-associated cells. However, direct contact between plant and bacteria is required for the induction of sporulation in the surrounding B. subtilis. This study has fundamental implications for our understanding of interactions between Bacillus spp. and plants, and particularly for a more efficient usage of B. subtilis as a biofertilizer or biofungicide.


Assuntos
Arabidopsis , Bacillus subtilis , Interações Hospedeiro-Patógeno , Plântula , Esporos Bacterianos , Arabidopsis/microbiologia , Bacillus subtilis/crescimento & desenvolvimento , Proteínas de Bactérias , Plântula/microbiologia , Esporos Bacterianos/crescimento & desenvolvimento
16.
Plant Sci ; 280: 228-240, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30824001

RESUMO

Salinity severely hampers crop productivity worldwide and plant growth promoting bacteria could serve as a sustainable solution to improve plant growth under salt stress. However, the molecular mechanisms underlying salt stress tolerance promotion by beneficial bacteria remain unclear. In this work, six bacterial isolates from four different desert plant species were screened for their biochemical plant growth promoting traits and salinity stress tolerance promotion of the unknown host plant Arabidopsis thaliana. Five of the isolates induced variable root phenotypes but could all increase plant shoot and root weight under salinity stress. Inoculation of Arabidopsis with five isolates under salinity stress resulted in tissue-specific transcriptional changes of ion transporters and reduced Na+/K+ shoot ratios. The work provides first insights into the possible mechanisms and the commonality by which phylogenetically diverse bacteria from different desert plants induce salinity stress tolerance in Arabidopsis. The bacterial isolates provide new tools for studying abiotic stress tolerance mechanisms in plants and a promising agricultural solution for increasing crop yields in semi-arid regions.


Assuntos
Arabidopsis/microbiologia , Bactérias/classificação , Fenômenos Fisiológicos Bacterianos , Regulação da Expressão Gênica de Plantas , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/fisiologia , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Bactérias/genética , Bactérias/isolamento & purificação , Clima Desértico , Endófitos , Transporte de Íons , Proteínas de Membrana Transportadoras/genética , Proteínas de Membrana Transportadoras/metabolismo , Filogenia , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/microbiologia , Raízes de Plantas/fisiologia , Brotos de Planta/genética , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/microbiologia , Brotos de Planta/fisiologia , Potássio/análise , Estresse Salino , Tolerância ao Sal , Sódio/análise
17.
Proc Natl Acad Sci U S A ; 116(8): 3193-3201, 2019 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-30728304

RESUMO

Cooperation is associated with major transitions in evolution such as the emergence of multicellularity. It is central to the evolution of many complex traits in nature, including growth and virulence in pathogenic bacteria. Whether cells of multicellular parasites function cooperatively during infection remains, however, largely unknown. Here, we show that hyphal cells of the fungal pathogen Sclerotinia sclerotiorum reprogram toward division of labor to facilitate the colonization of host plants. Using global transcriptome sequencing, we reveal that gene expression patterns diverge markedly in cells at the center and apex of hyphae during Arabidopsis thaliana colonization compared with in vitro growth. We reconstructed a genome-scale metabolic model for S. sclerotiorum and used flux balance analysis to demonstrate metabolic heterogeneity supporting division of labor between hyphal cells. Accordingly, continuity between the central and apical compartments of invasive hyphae was required for optimal growth in planta Using a multicell model of fungal hyphae, we show that this cooperative functioning enhances fungal growth predominantly during host colonization. Our work identifies cooperation in fungal hyphae as a mechanism emerging at the multicellular level to support host colonization and virulence.


Assuntos
Arabidopsis/microbiologia , Ascomicetos/patogenicidade , Interações Hospedeiro-Patógeno/genética , Doenças das Plantas/genética , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Ascomicetos/genética , Genoma de Planta/genética , Hifas/genética , Hifas/patogenicidade , Doenças das Plantas/microbiologia
18.
Int J Mol Sci ; 20(4)2019 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-30781829

RESUMO

RAD51 (DNA repair gene) family genes play ubiquitous roles in immune response among species from plants to mammals. In this study, we cloned the ZmRAD51A gene (a member of RAD51) in maize and generated ZmRAD51A overexpression (ZmRAD51A-OE) in rice, tobacco, and Arabidopsis. The expression level of ZmRAD51A was remarkably induced by salicylic acid (SA) application in maize, and the transient overexpression of ZmRAD51A in tobacco induced a hypersensitive response. The disease resistance was significantly enhanced in ZmRAD51A- OE (overexpressing) plants, triggering an increased expression of defense-related genes. High-performance liquid chromatography (HPLC) analysis showed that, compared to control lines, ZmRAD51A-OE in rice plants resulted in higher SA levels, and conferred rice plants resistance to Magnaporthe oryzae. Moreover, the ZmRAD51A-OE Arabidopsis plants displayed increased resistance to Pseudomonas syringae pv. tomato DC3000 when compared to wild types. Together, our results provide the evidence that, for the first time, the maize DNA repair gene ZmRAD51A plays an important role in in disease resistance.


Assuntos
Arabidopsis/imunologia , Reparo do DNA/genética , Resistência à Doença , Genes de Plantas , Oryza/imunologia , Doenças das Plantas/imunologia , Zea mays/genética , Arabidopsis/microbiologia , Regulação da Expressão Gênica de Plantas , Magnaporthe , Oryza/microbiologia , Doenças das Plantas/microbiologia , Folhas de Planta/fisiologia , Plantas Geneticamente Modificadas , Pseudomonas syringae/fisiologia , Ácido Salicílico/metabolismo , Tabaco/genética
19.
Nat Commun ; 10(1): 844, 2019 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-30783097

RESUMO

Argonaute (AGO) proteins are core components of RNA interference (RNAi) but the mechanisms of their regulation, especially at the post-translational level, remain unclear. Among the ten AGOs in Arabidopsis, only AGO2 is induced by bacterial infection and is known to positively regulate immunity. Here we show that the N-terminal domain of AGO2 is enriched with arginine-glycine RG/GR repeats, which are methylated by protein arginine methyltransferase5 (PRMT5). Arginine methylation has dual functions in AGO2 regulation. Methylated arginine residues can promote AGO2 protein degradation and are also bound by Tudor-domain proteins (TSNs), which can degrade AGO2-associated small RNAs (sRNAs). PRMT5 is down-regulated during infection and the prmt5 mutant is more resistant to bacteria. We speculate that reduced PRMT5 expression during infection may lead to reduced arginine methylation of AGO2, resulting in accumulation of both AGO2 and, via reduced interaction with TSNs, accumulation of AGO2-associated sRNAs, to promote plant immunity. These results reveal that both the arginine methylation writer (PRMT5) and readers (TSNs) can regulate AGO2-mediated RNAi.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arginina/metabolismo , Proteínas Argonauta/metabolismo , Proteína-Arginina N-Metiltransferases/metabolismo , Arabidopsis/metabolismo , Arabidopsis/microbiologia , Proteínas de Arabidopsis/genética , Proteínas Argonauta/genética , Metilação , Doenças das Plantas/microbiologia , Plantas Geneticamente Modificadas , Estabilidade Proteica , Pseudomonas syringae/patogenicidade , RNA de Plantas/metabolismo
20.
Plant Physiol ; 179(4): 1343-1361, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30670606

RESUMO

Trichoderma spp. are a rich source of secondary metabolites and volatile organic compounds (VOCs), which may induce plant defenses and modulate plant growth. In filamentous fungi, chromatin modifications regulate secondary metabolism. In this study we investigated how the absence of histone deacetylase HDA-2 in the Trichoderma atroviride strain Δhda-2 impacts its effect on a host, Arabidopsis (Arabidopsis thaliana). The production of VOCs and their impact on plant growth and development were assessed as well. The Δhda-2 strain was impaired in its ability to colonize Arabidopsis roots, thus affecting the promotion of plant growth and modulation of plant defenses against foliar pathogens Botrytis cinerea and Pseudomonas syringae, which normally result from interaction with T. atroviride Furthermore, Δhda-2 VOCs were incapable of triggering plant defenses to counterattack foliar pathogens. The Δhda-2 overproduced the VOC 6-pentyl-2H-pyran-2-one (6-PP), which resulted in enhanced root branching and differentially regulated phytohormone-related genes. Analysis of ten VOCs (including 6-PP) revealed that three of them positively regulated plant growth, whereas six had the opposite effect. Assessment of secondary metabolites, detoxification, and communication with plant-related genes showed a dual role for HDA-2 in T. atroviride gene expression regulation during its interaction with plants. Chromatin immunoprecipitation of acetylated histone H3 on the promoters of plant-responsive genes in Δhda-2 showed, in the presence of Arabidopsis, low levels of epl-1 and abc-2 compared with that in the wild type; whereas ctf-1 presented high constitutive levels, supporting a dual role of HDA-2 in gene regulation. This work highlights the importance of HDA-2 as a global regulator in Trichoderma to modulate multiple responses in Arabidopsis.


Assuntos
Arabidopsis/microbiologia , Histona Desacetilases/metabolismo , Trichoderma/enzimologia , Compostos Orgânicos Voláteis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Proteínas Fúngicas/metabolismo , Regulação da Expressão Gênica de Plantas , Desenvolvimento Vegetal , Doenças das Plantas , Imunidade Vegetal , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/microbiologia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA