RESUMEN
The downy mildew oomycete Hyaloperonospora arabidopsidis, an obligate filamentous pathogen, infects Arabidopsis (Arabidopsis thaliana) by forming structures called haustoria inside host cells. Previous transcriptome analyses have revealed that host genes are specifically induced during infection; however, RNA profiling from whole-infected tissues may fail to capture key transcriptional events occurring exclusively in haustoriated host cells, where the pathogen injects virulence effectors to modulate host immunity. To determine interactions between Arabidopsis and H. arabidopsidis at the cellular level, we devised a translating ribosome affinity purification system using 2 high-affinity binding proteins, colicin E9 and Im9 (immunity protein of colicin E9), applicable to pathogen-responsive promoters, thus enabling haustoriated cell-specific RNA profiling. Among the host genes specifically expressed in H. arabidopsidis-haustoriated cells, we found genes that promote either susceptibility or resistance to the pathogen, providing insights into the Arabidopsis-downy mildew interaction. We propose that our protocol for profiling cell-specific transcripts will apply to several stimulus-specific contexts and other plant-pathogen interactions.
Asunto(s)
Arabidopsis , Colicinas , Oomicetos , Peronospora , Arabidopsis/genética , ARN/metabolismo , Colicinas/metabolismo , Interacciones Huésped-Patógeno/genética , Enfermedades de las Plantas/genéticaRESUMEN
The rapid production of reactive oxygen species (ROS) burst is a conserved signaling output in immunity across kingdoms. In plants, perception of pathogen-associated molecular patterns (PAMPs) by surface-localized pattern recognition receptors (PRRs) activates the NADPH oxidase RBOHD by hitherto unknown mechanisms. Here, we show that RBOHD exists in complex with the receptor kinases EFR and FLS2, which are the PRRs for bacterial EF-Tu and flagellin, respectively. The plasma-membrane-associated kinase BIK1, which is a direct substrate of the PRR complex, directly interacts with and phosphorylates RBOHD upon PAMP perception. BIK1 phosphorylates different residues than calcium-dependent protein kinases, and both PAMP-induced BIK1 activation and BIK1-mediated phosphorylation of RBOHD are calcium independent. Importantly, phosphorylation of these residues is critical for the PAMP-induced ROS burst and antibacterial immunity. Our study reveals a rapid regulatory mechanism of a plant RBOH, which occurs in parallel with and is essential for its paradigmatic calcium-based regulation.
Asunto(s)
Proteínas de Arabidopsis/inmunología , Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimología , Inmunidad Innata , NADPH Oxidasas/inmunología , Nicotiana/enzimología , Inmunidad de la Planta , Proteínas Serina-Treonina Quinasas/metabolismo , Secuencia de Aminoácidos , Arabidopsis/genética , Arabidopsis/inmunología , Arabidopsis/microbiología , Proteínas de Arabidopsis/genética , Línea Celular , Activación Enzimática , Flagelina/inmunología , Flagelina/metabolismo , Regulación Enzimológica de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Ligandos , Datos de Secuencia Molecular , Complejos Multienzimáticos , NADPH Oxidasas/genética , Factor Tu de Elongación Peptídica/inmunología , Factor Tu de Elongación Peptídica/metabolismo , Fosforilación , Estomas de Plantas/inmunología , Estomas de Plantas/metabolismo , Proteínas Quinasas/inmunología , Proteínas Quinasas/metabolismo , Proteínas Serina-Treonina Quinasas/genética , Especies Reactivas de Oxígeno/metabolismo , Receptores Inmunológicos/metabolismo , Receptores de Reconocimiento de Patrones/inmunología , Receptores de Reconocimiento de Patrones/metabolismo , Transducción de Señal , Nicotiana/genética , Nicotiana/inmunología , Nicotiana/microbiologíaRESUMEN
The soilborne filamentous fungus Fusarium oxysporum causes devastating diseases of many cultivated plant species. F. oxysporum f. sp. raphani and f. sp. rapae are two of four formae speciales that are pathogenic to Brassicaceae plants. Here, we present high-quality genome sequences of F. oxysporum f. sp. raphani strain Tf1262 and F. oxysporum f. sp. rapae strain Tf1208 that were isolated from radish (Raphanus sativus) and turnip (Brassica rapa var. rapa), respectively. These genome resources should facilitate in-depth investigation of interactions between F. oxysporum and Brassicaceae plants, and enable comparative genomics of the F. oxysporum species complex to uncover how pathogenicity evolved within F. oxysporum.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
Asunto(s)
Brassicaceae , Fusarium , Fusarium/genética , Genoma Fúngico , Enfermedades de las PlantasRESUMEN
Plant immunity protects plants from numerous potentially pathogenic microbes. The biological network that controls plant inducible immunity must function effectively even when network components are targeted and disabled by pathogen effectors. Network buffering could confer this resilience by allowing different parts of the network to compensate for loss of one another's functions. Networks rich in buffering rely on interactions within the network, but these mechanisms are difficult to study by simple genetic means. Through a network reconstitution strategy, in which we disassemble and stepwise reassemble the plant immune network that mediates Pattern-Triggered-Immunity, we have resolved systems-level regulatory mechanisms underlying the Arabidopsis transcriptome response to the immune stimulant flagellin-22 (flg22). These mechanisms show widespread evidence of interactions among major sub-networks-we call these sectors-in the flg22-responsive transcriptome. Many of these interactions result in network buffering. Resolved regulatory mechanisms show unexpected patterns for how the jasmonate (JA), ethylene (ET), phytoalexin-deficient 4 (PAD4), and salicylate (SA) signaling sectors control the transcriptional response to flg22. We demonstrate that many of the regulatory mechanisms we resolved are not detectable by the traditional genetic approach of single-gene null-mutant analysis. Similar to potential pathogenic perturbations, null-mutant effects on immune signaling can be buffered by the network.
Asunto(s)
Proteínas de Arabidopsis/genética , Hidrolasas de Éster Carboxílico/genética , Flagelina/genética , Interacciones Huésped-Patógeno/genética , Inmunidad de la Planta/genética , Transcriptoma/genética , Arabidopsis/genética , Arabidopsis/inmunología , Proteínas de Arabidopsis/inmunología , Hidrolasas de Éster Carboxílico/inmunología , Ciclopentanos/inmunología , Ciclopentanos/metabolismo , Etilenos/inmunología , Etilenos/metabolismo , Flagelina/inmunología , Regulación de la Expresión Génica de las Plantas , Redes Reguladoras de Genes/inmunología , Interacciones Huésped-Patógeno/inmunología , Oxilipinas/inmunología , Oxilipinas/metabolismo , Enfermedades de las Plantas/genética , Enfermedades de las Plantas/inmunología , Ácido Salicílico/inmunología , Ácido Salicílico/metabolismo , Transducción de Señal , Transcriptoma/inmunologíaRESUMEN
The oomycete pathogen Hyaloperonospora arabidopsidis (Hpa) causes downy mildew disease on Arabidopsis. To colonize its host, Hpa translocates effector proteins that suppress plant immunity into infected host cells. Here, we investigate the relevance of the interaction between one of these effectors, HaRxL106, and Arabidopsis RADICAL-INDUCED CELL DEATH1 (RCD1). We use pathogen infection assays as well as molecular and biochemical analyses to test the hypothesis that HaRxL106 manipulates RCD1 to attenuate transcriptional activation of defense genes. We report that HaRxL106 suppresses transcriptional activation of salicylic acid (SA)-induced defense genes and alters plant growth responses to light. HaRxL106-mediated suppression of immunity is abolished in RCD1 loss-of-function mutants. We report that RCD1-type proteins are phosphorylated, and we identified Mut9-like kinases (MLKs), which function as phosphoregulatory nodes at the level of photoreceptors, as RCD1-interacting proteins. An mlk1,3,4 triple mutant exhibits stronger SA-induced defense marker gene expression compared with wild-type plants, suggesting that MLKs also affect transcriptional regulation of SA signaling. Based on the combined evidence, we hypothesize that nuclear RCD1/MLK complexes act as signaling nodes that integrate information from environmental cues and pathogen sensors, and that the Arabidopsis downy mildew pathogen targets RCD1 to prevent activation of plant immunity.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/inmunología , Arabidopsis/microbiología , Proteínas Nucleares/metabolismo , Oomicetos/metabolismo , Inmunidad de la Planta , Proteínas/metabolismo , ADP Ribosa Transferasas/metabolismo , Arabidopsis/efectos de los fármacos , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Regulación de la Expresión Génica de las Plantas/efectos de la radiación , Mutación/genética , Proteínas Nucleares/genética , Oomicetos/efectos de los fármacos , Oomicetos/aislamiento & purificación , Oomicetos/patogenicidad , Enfermedades de las Plantas/microbiología , Inmunidad de la Planta/efectos de los fármacos , Plantas Modificadas Genéticamente , Dominios Proteicos , Multimerización de Proteína/efectos de los fármacos , Ácido Salicílico/farmacología , Transducción de Señal/efectos de la radiación , Transcripción Genética/efectos de los fármacos , Virulencia/efectos de los fármacosRESUMEN
BACKGROUND: Plants are exposed to diverse pathogens and pests, yet most plants are resistant to most plant pathogens. Non-host resistance describes the ability of all members of a plant species to successfully prevent colonization by any given member of a pathogen species. White blister rust caused by Albugo species can overcome non-host resistance and enable secondary infection and reproduction of usually non-virulent pathogens, including the potato late blight pathogen Phytophthora infestans on Arabidopsis thaliana. However, the molecular basis of host defense suppression in this complex plant-microbe interaction is unclear. Here, we investigate specific defense mechanisms in Arabidopsis that are suppressed by Albugo infection. RESULTS: Gene expression profiling revealed that two species of Albugo upregulate genes associated with tryptophan-derived antimicrobial metabolites in Arabidopsis. Albugo laibachii-infected tissue has altered levels of these metabolites, with lower indol-3-yl methylglucosinolate and higher camalexin accumulation than uninfected tissue. We investigated the contribution of these Albugo-imposed phenotypes to suppression of non-host resistance to P. infestans. Absence of tryptophan-derived antimicrobial compounds enables P. infestans colonization of Arabidopsis, although to a lesser extent than Albugo-infected tissue. A. laibachii also suppresses a subset of genes regulated by salicylic acid; however, salicylic acid plays only a minor role in non-host resistance to P. infestans. CONCLUSIONS: Albugo sp. alter tryptophan-derived metabolites and suppress elements of the responses to salicylic acid in Arabidopsis. Albugo sp. imposed alterations in tryptophan-derived metabolites may play a role in Arabidopsis non-host resistance to P. infestans. Understanding the basis of non-host resistance to pathogens such as P. infestans could assist in development of strategies to elevate food security.
Asunto(s)
Antiinfecciosos/metabolismo , Arabidopsis/inmunología , Arabidopsis/microbiología , Vías Biosintéticas , Resistencia a la Enfermedad/inmunología , Phytophthora infestans/fisiología , Enfermedades de las Plantas/microbiología , Triptófano/metabolismo , Arabidopsis/efectos de los fármacos , Arabidopsis/genética , Biomasa , Vías Biosintéticas/efectos de los fármacos , Vías Biosintéticas/genética , Brassica/microbiología , Resistencia a la Enfermedad/efectos de los fármacos , Susceptibilidad a Enfermedades , Perfilación de la Expresión Génica , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Ontología de Genes , Genes de Plantas , Glucosinolatos/metabolismo , Indoles/metabolismo , Redes y Vías Metabólicas/efectos de los fármacos , Mutación/genética , Enfermedades de las Plantas/inmunología , Inmunidad de la Planta/efectos de los fármacos , Hojas de la Planta/efectos de los fármacos , Hojas de la Planta/microbiología , Reproducibilidad de los Resultados , Ácido Salicílico/farmacología , Transducción de Señal/efectos de los fármacos , Tiazoles/metabolismo , Regulación hacia Arriba/efectos de los fármacosRESUMEN
Importin-αs are essential adapter proteins that recruit cytoplasmic proteins destined for active nuclear import to the nuclear transport machinery. Cargo proteins interact with the importin-α armadillo repeat domain via nuclear localization sequences (NLSs), short amino acids motifs enriched in Lys and Arg residues. Plant genomes typically encode several importin-α paralogs that can have both specific and partially redundant functions. Although some cargos are preferentially imported by a distinct importin-α it remains unknown how this specificity is generated and to what extent cargos compete for binding to nuclear transport receptors. Here we report that the effector protein HaRxL106 from the oomycete pathogen Hyaloperonospora arabidopsidis co-opts the host cell's nuclear import machinery. We use HaRxL106 as a probe to determine redundant and specific functions of importin-α paralogs from Arabidopsis thaliana. A crystal structure of the importin-α3/MOS6 armadillo repeat domain suggests that five of the six Arabidopsis importin-αs expressed in rosette leaves have an almost identical NLS-binding site. Comparison of the importin-α binding affinities of HaRxL106 and other cargos in vitro and in plant cells suggests that relatively small affinity differences in vitro affect the rate of transport complex formation in vivo. Our results suggest that cargo affinity for importin-α, sequence variation at the importin-α NLS-binding sites and tissue-specific expression levels of importin-αs determine formation of cargo/importin-α transport complexes in plant cells.
Asunto(s)
Proteínas de Arabidopsis/fisiología , Arabidopsis/metabolismo , Carioferinas/fisiología , Transporte Activo de Núcleo Celular , Secuencia de Aminoácidos , Arabidopsis/genética , Arabidopsis/microbiología , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Secuencia Conservada , Escherichia coli/genética , Interacciones Huésped-Patógeno , Carioferinas/química , Carioferinas/genética , Carioferinas/metabolismo , Modelos Moleculares , Oomicetos/genética , Estructura Terciaria de ProteínaRESUMEN
Plants have evolved strong innate immunity mechanisms, but successful pathogens evade or suppress plant immunity via effectors delivered into the plant cell. Hyaloperonospora arabidopsidis (Hpa) causes downy mildew on Arabidopsis thaliana, and a genome sequence is available for isolate Emoy2. Here, we exploit the availability of genome sequences for Hpa and Arabidopsis to measure gene-expression changes in both Hpa and Arabidopsis simultaneously during infection. Using a high-throughput cDNA tag sequencing method, we reveal expression patterns of Hpa predicted effectors and Arabidopsis genes in compatible and incompatible interactions, and promoter elements associated with Hpa genes expressed during infection. By resequencing Hpa isolate Waco9, we found it evades Arabidopsis resistance gene RPP1 through deletion of the cognate recognized effector ATR1. Arabidopsis salicylic acid (SA)-responsive genes including PR1 were activated not only at early time points in the incompatible interaction but also at late time points in the compatible interaction. By histochemical analysis, we found that Hpa suppresses SA-inducible PR1 expression, specifically in the haustoriated cells into which host-translocated effectors are delivered, but not in non-haustoriated adjacent cells. Finally, we found a highly-expressed Hpa effector candidate that suppresses responsiveness to SA. As this approach can be easily applied to host-pathogen interactions for which both host and pathogen genome sequences are available, this work opens the door towards transcriptome studies in infection biology that should help unravel pathogen infection strategies and the mechanisms by which host defense responses are overcome.
Asunto(s)
Arabidopsis/efectos de los fármacos , Arabidopsis/genética , Interacciones Huésped-Patógeno/inmunología , Oomicetos/efectos de los fármacos , Enfermedades de las Plantas/inmunología , Inmunidad de la Planta/inmunología , Ácido Salicílico/farmacología , Proteínas de Arabidopsis/genética , Secuencia de Bases/genética , Regulación de la Expresión Génica de las Plantas , Interacciones Huésped-Patógeno/efectos de los fármacos , Oomicetos/genética , Enfermedades de las Plantas/genética , Enfermedades de las Plantas/microbiología , Ácido Salicílico/metabolismoRESUMEN
Plants are continually exposed to pathogen attack but usually remain healthy because they can activate defences upon perception of microbes. However, pathogens have evolved to overcome plant immunity by delivering effectors into the plant cell to attenuate defence, resulting in disease. Recent studies suggest that some effectors may manipulate host transcription, but the specific mechanisms by which such effectors promote susceptibility remain unclear. We study the oomycete downy mildew pathogen of Arabidopsis, Hyaloperonospora arabidopsidis (Hpa), and show here that the nuclear-localized effector HaRxL44 interacts with Mediator subunit 19a (MED19a), resulting in the degradation of MED19a in a proteasome-dependent manner. The Mediator complex of â¼25 proteins is broadly conserved in eukaryotes and mediates the interaction between transcriptional regulators and RNA polymerase II. We found MED19a to be a positive regulator of immunity against Hpa. Expression profiling experiments reveal transcriptional changes resembling jasmonic acid/ethylene (JA/ET) signalling in the presence of HaRxL44, and also 3 d after infection with Hpa. Elevated JA/ET signalling is associated with a decrease in salicylic acid (SA)-triggered immunity (SATI) in Arabidopsis plants expressing HaRxL44 and in med19a loss-of-function mutants, whereas SATI is elevated in plants overexpressing MED19a. Using a PR1::GUS reporter, we discovered that Hpa suppresses PR1 expression specifically in cells containing haustoria, into which RxLR effectors are delivered, but not in nonhaustoriated adjacent cells, which show high PR1::GUS expression levels. Thus, HaRxL44 interferes with Mediator function by degrading MED19, shifting the balance of defence transcription from SA-responsive defence to JA/ET-signalling, and enhancing susceptibility to biotrophs by attenuating SA-dependent gene expression.
Asunto(s)
Arabidopsis/fisiología , Interacciones Huésped-Patógeno/fisiología , Peronospora/inmunología , Enfermedades de las Plantas/microbiología , Reguladores del Crecimiento de las Plantas/fisiología , Inmunidad de la Planta/fisiología , Ácido Salicílico/metabolismo , Proteínas de Arabidopsis/fisiología , Interacciones Huésped-Patógeno/inmunología , Complejo Mediador/fisiología , Enfermedades de las Plantas/inmunologíaRESUMEN
Calcium-dependent protein kinases (CDPKs) are Ca(2+) sensors that regulate diverse biological processes in plants and apicomplexans. However, how CDPKs discriminate specific substrates in vivo is still largely unknown. Previously, we found that a potato StCDPK5 is dominantly localized to the plasma membrane and activates the plasma membrane NADPH oxidase (RBOH; for respiratory burst oxidase homolog) StRBOHB by direct phosphorylation of the N-terminal region. Here, we report the contribution of the StCDPK5 N-terminal variable (V) domain to activation of StRBOHB in vivo using heterologous expression system in Nicotiana benthamiana. Mutations of N-terminal myristoylation and palmitoylation sites in the V domain eliminated the predominantly plasma membrane localization and the capacity of StCDPK5 to activate StRBOHB in vivo. A tomato SlCDPK2, which also contains myristoylation and palmitoylation sites in its N terminus, phosphorylated StRBOHB in vitro but not in vivo. Functional domains responsible for activation and phosphorylation of StRBOHB were identified by swapping regions for each domain between StCDPK5 and SlCDPK2. The substitution of the V domain of StCDPK5 with that of SlCDPK2 abolished the activation and phosphorylation abilities of StRBOHB in vivo and relocalized the chimeric CDPK to the trans-Golgi network, as observed for SlCDPK2. Conversely, SlCDPK2 substituted with the V domain of StCDPK5 localized to the plasma membrane and activated StRBOHB. These results suggest that the V domains confer substrate specificity in vivo by dictating proper subcellular localization of CDPKs.
Asunto(s)
Regulación de la Expresión Génica de las Plantas , Mutación , NADPH Oxidasas/metabolismo , Nicotiana/metabolismo , Proteínas de Plantas/metabolismo , Proteínas Quinasas/metabolismo , Calcio/metabolismo , Membrana Celular/metabolismo , Solanum lycopersicum/enzimología , Solanum lycopersicum/genética , Microscopía Confocal , Fosforilación , Inmunidad de la Planta , Proteínas de Plantas/genética , Proteínas Quinasas/genética , Especies Reactivas de Oxígeno , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Estallido Respiratorio , Transducción de Señal , Solanum tuberosum/enzimología , Solanum tuberosum/genética , Especificidad por SustratoRESUMEN
Sequential recognition of invading microbes and rapid induction of plant immune responses comprise at least two recognition systems. Early basal defenses are initiated by pathogen-associated molecular patterns and pattern recognition receptors (PRR) in the plasma membrane. Pathogens produce effectors to suppress defense but plants, in turn, can sense such effectors by dominant plant resistance (R) gene products. Plant PRR and R proteins modulate signaling networks for defense responses that rely on rapid production of reactive nitrogen species (RNS) and reactive oxygen species (ROS). Recent research has shown that nitric oxide (NO) mainly mediates biological function through chemical reactions between locally controlled accumulation of RNS and proteins leading to potential alteration of protein function. Many proteins specifically regulated by NO and participating in signaling during plant defense response have been identified, highlighting the physiological relevance of these modifications in plant immunity. ROS function independently or in cooperation with NO during defense, modulating the RNS signaling functions through the entire process. This review provides an overview of current knowledge about regulatory mechanisms for NO burst and signaling, and crosstalk with ROS in response to pathogen attack.
Asunto(s)
Óxido Nítrico/metabolismo , Inmunidad de la Planta , Plantas/inmunología , Transducción de Señal , Interacciones Huésped-Patógeno , Proteínas de Plantas/metabolismo , Plantas/metabolismo , Plantas/microbiología , Especies de Nitrógeno Reactivo/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Receptores de Reconocimiento de Patrones/fisiologíaRESUMEN
Transposable elements (TEs) are accumulated in both intergenic and intragenic regions in plant genomes. Intragenic TEs often act as regulatory elements of associated genes and are also co-transcribed with genes, generating chimeric TE-gene transcripts. Despite the potential impact on mRNA regulation and gene function, the prevalence and transcriptional regulation of TE-gene transcripts are poorly understood. By long-read direct RNA sequencing and a dedicated bioinformatics pipeline, ParasiTE, we investigated the transcription and RNA processing of TE-gene transcripts in Arabidopsis thaliana. We identified a global production of TE-gene transcripts in thousands of A. thaliana gene loci, with TE sequences often being associated with alternative transcription start sites or transcription termination sites. The epigenetic state of intragenic TEs affects RNAPII elongation and usage of alternative poly(A) signals within TE sequences, regulating alternative TE-gene isoform production. Co-transcription and inclusion of TE-derived sequences into gene transcripts impact regulation of RNA stability and environmental responses of some loci. Our study provides insights into TE-gene interactions that contributes to mRNA regulation, transcriptome diversity, and environmental responses in plants.
Asunto(s)
Arabidopsis , Arabidopsis/genética , Epigénesis Genética , Regulación de la Expresión Génica de las Plantas , Elementos Transponibles de ADN/genética , ARN Interferente Pequeño/genética , ARN Mensajero/genética , Análisis de Secuencia de ARNRESUMEN
⢠Potato (Solanum tuberosum) calcium-dependent protein kinase (StCDPK5) has been shown to phosphorylate the N-terminal region of plasma membrane RBOH (respiratory burst oxidase homolog) proteins, and participate in StRBOHB-mediated reactive oxygen species (ROS) burst. The constitutively active form, StCDPK5VK, provides a useful tool for gain-of-function analysis of RBOH in defense responses. ⢠StCDPK5- and StCDPK5VK-green fluorescent protein fusion proteins were predominantly targeted to the plasma membrane, and conditional expression of StCDPK5VK activated StRBOHA-D. The interaction was confirmed by bimolecular fluorescence complementation assay. We generated transgenic potato plants containing StCDPK5VK under the control of a pathogen-inducible promoter to investigate the role of ROS burst on defense responses to blight pathogens. ⢠Virulent isolates of the late blight pathogen Phytophthora infestans and the early blight pathogen Alternaria solani induced hypersensitive response-like cell death accompanied by ROS production at the infection sites of transgenic plants. Transgenic plants showed resistance to the near-obligate hemibiotrophic pathogen P. infestans and, by contrast, increased susceptibility to the necrotrophic pathogen A. solani. ⢠These results indicate that RBOH-dependent ROS contribute to basal defense against near-obligate pathogens, but have a negative role in resistance or have a positive role in expansion of disease lesions caused by necrotrophic pathogens.
Asunto(s)
Alternaria/fisiología , Resistencia a la Enfermedad/inmunología , Phytophthora infestans/fisiología , Enfermedades de las Plantas/microbiología , Proteínas Quinasas/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Solanum tuberosum/enzimología , Secuencia de Aminoácidos , Secuencia de Bases , Membrana Celular/metabolismo , Resistencia a la Enfermedad/genética , Perfilación de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Glucuronidasa , Modelos Biológicos , Datos de Secuencia Molecular , Phytophthora infestans/patogenicidad , Enfermedades de las Plantas/genética , Hojas de la Planta/microbiología , Proteínas de Plantas/química , Proteínas de Plantas/metabolismo , Plantas Modificadas Genéticamente , Regiones Promotoras Genéticas/genética , Unión Proteica , Transporte de Proteínas , Estallido Respiratorio/genética , Solanum tuberosum/genética , Solanum tuberosum/inmunología , Solanum tuberosum/microbiología , Fracciones Subcelulares/metabolismo , Nicotiana/genética , Nicotiana/microbiologíaRESUMEN
Nitric oxide (NO) and reactive oxygen species (ROS) play key roles in plant immunity. However, the regulatory mechanisms of the production of these radicals are not fully understood. Hypersensitive response (HR) cell death requires the simultaneous and balanced production of NO and ROS. In this study we indentified NbRibAencoding a bifunctional enzyme, guanosine triphosphate cyclohydrolase II/3,4-dihydroxy-2-butanone-4-phosphate synthase, which participates in the biosynthesis of flavin, by screening genes related to mitogen-activated protein kinase-mediated cell death, using virus-induced gene silencing. Levels of endogenous riboflavin and its derivatives, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which are important prosthetic groups for several enzymes participating in redox reactions, decreased in NbRibA-silenced Nicotiana benthamiana. Silencing NbRibA compromised not only HR cell death, but also the NO and ROS production induced by INF1 elicitin and a constitutively active form of NbMEK2 (NbMEK2DD), and also induced high susceptibility to oomycete Phytophthora infestans and ascomycete Colletotrichum orbiculare. Compromised radical production and HR cell death induced by INF1 in NbRibA-silenced leaves were rescued by adding riboflavin, FMN or FAD. These results indicate that flavin biosynthesis participates in regulating NO and ROS production, and HR cell death.
Asunto(s)
Flavinas/biosíntesis , Transferasas Intramoleculares/metabolismo , Nicotiana/enzimología , Óxido Nítrico/metabolismo , Proteínas de Plantas/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Muerte Celular , Regulación de la Expresión Génica de las Plantas , Biblioteca de Genes , Silenciador del Gen , Genes de Plantas , Inmunidad Innata , Transferasas Intramoleculares/genética , Mutagénesis Sitio-Dirigida , Proteínas de Plantas/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Nicotiana/genética , Nicotiana/inmunologíaRESUMEN
Rapid production of nitric oxide (NO) and reactive oxygen species (ROS) has been implicated in diverse physiological processes, such as programmed cell death, development, cell elongation and hormonal signaling, in plants. Much attention has been paid to the regulation of plant innate immunity by these signal molecules. Recent studies provide evidence that an NADPH oxidase, respiratory burst oxidase homolog, is responsible for pathogen-responsive ROS burst. However, we still do not know about NO-producing enzymes, except for nitrate reductase, although many studies suggest the existence of NO synthase-like activity responsible for NO burst in plants. Here, we introduce regulatory mechanisms of NO and ROS bursts by mitogen-activated protein kinase cascades, calcium-dependent protein kinase or riboflavin and its derivatives, flavin mononucleotide and flavin adenine dinucleotide, and we discuss the roles of the bursts in defense responses against plant pathogens.
Asunto(s)
Óxido Nítrico/metabolismo , Inmunidad de la Planta , Especies Reactivas de Oxígeno/metabolismo , Activación Enzimática , Silenciador del Gen , Genes de Plantas , Proteínas Quinasas Activadas por Mitógenos/metabolismo , NADPH Oxidasas/metabolismo , Óxido Nítrico Sintasa/metabolismo , Oxidación-Reducción , Fosforilación , Proteínas de Plantas/metabolismo , Plantas/genética , Plantas/inmunología , Plantas/metabolismo , Riboflavina/metabolismo , Transducción de SeñalRESUMEN
Nonsteroidal anti-inflammatory drugs (NSAIDs), including salicylic acid (SA), target mammalian cyclooxygenases. In plants, SA is a defense hormone that regulates NON-EXPRESSOR OF PATHOGENESIS RELATED GENES 1 (NPR1), the master transcriptional regulator of immunity-related genes. We identify that the oxicam-type NSAIDs tenoxicam (TNX), meloxicam, and piroxicam, but not other types of NSAIDs, exhibit an inhibitory effect on immunity to bacteria and SA-dependent plant immune response. TNX treatment decreases NPR1 levels, independently from the proposed SA receptors NPR3 and NPR4. Instead, TNX induces oxidation of cytosolic redox status, which is also affected by SA and regulates NPR1 homeostasis. A cysteine labeling assay reveals that cysteine residues in NPR1 can be oxidized in vitro, leading to disulfide-bridged oligomerization of NPR1, but not in vivo regardless of SA or TNX treatment. Therefore, this study indicates that oxicam inhibits NPR1-mediated SA signaling without affecting the redox status of NPR1.
Asunto(s)
Antiinflamatorios no Esteroideos/farmacología , Proteínas de Arabidopsis/metabolismo , Arabidopsis/efectos de los fármacos , Arabidopsis/metabolismo , Piroxicam/análogos & derivados , Ácido Salicílico/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Meloxicam/farmacología , Piroxicam/farmacologíaRESUMEN
Pseudomonas amygdali pv. tabaci strain 6605 is the bacterial pathogen causing tobacco wildfire disease that has been used as a model for elucidating virulence mechanisms. Here, we present the complete genome sequence of P. amygdali pv. tabaci 6605 as a circular chromosome from reads using a PacBio sequencer.
RESUMEN
Many plant pathogenic fungi contain conditionally dispensable (CD) chromosomes that are associated with virulence, but not growth in vitro. Virulence-associated CD chromosomes carry genes encoding effectors and/or host-specific toxin biosynthesis enzymes that may contribute to determining host specificity. Fusarium oxysporum causes devastating diseases of more than 100 plant species. Among a large number of host-specific forms, F. oxysporum f. sp. conglutinans (Focn) can infect Brassicaceae plants including Arabidopsis (Arabidopsis thaliana) and cabbage. Here we show that Focn has multiple CD chromosomes. We identified specific CD chromosomes that are required for virulence on Arabidopsis, cabbage, or both, and describe a pair of effectors encoded on one of the CD chromosomes that is required for suppression of Arabidopsis-specific phytoalexin-based immunity. The effector pair is highly conserved in F. oxysporum isolates capable of infecting Arabidopsis, but not of other plants. This study provides insight into how host specificity of F. oxysporum may be determined by a pair of effector genes on a transmissible CD chromosome.
Asunto(s)
Cromosomas Fúngicos/genética , Fusarium/genética , Enfermedades de las Plantas/microbiología , Arabidopsis/inmunología , Arabidopsis/microbiología , Brassicaceae/inmunología , Brassicaceae/microbiología , Cromosomas Fúngicos/fisiología , Fusarium/patogenicidad , Fusarium/fisiología , Genoma Fúngico/genética , Interacciones Huésped-Patógeno/inmunología , Enfermedades de las Plantas/inmunologíaRESUMEN
Nitric oxide (NO) is an essential regulatory molecule in plant immunity in synergy with reactive oxygen species (ROS). However, little is known about the role of NO in disease resistance to necrotrophic pathogens. NO and oxidative bursts were induced during necrotrophic fungal pathogen Botrytis cinerea and Nicotiana benthamiana compatible interaction. Histochemical analyses showed that both NO and ROS were produced in adjacent cells of invaded areas in N. benthamiana leaves. Activation of salicylic acid-induced protein kinase, which regulates the radical burst, and several defense-related genes were induced after inoculation of B. cinerea. Loss-of-function analyses using inhibitors and virus-induced gene silencing were done to investigate the role of the radical burst in pathogenesis. We showed that NO plays a pivotal role in basal defense against B. cinerea and PR-1 gene expression in N. benthamiana. By contrast, ROS function has a negative role in resistance or has a positive role in expansion of disease lesions during B. cinerea-N. benthamiana interaction.