Propagation, Storage, and Assays with Hyaloperonospora arabidopsidis: A Model Oomycete Pathogen of Arabidopsis

McDowell, John M.; Hoff, Troy; Anderson, Ryan; Deegan, Daniel F.

doi:10.1007/978-1-61737-998-7_12

Cited by 25 publications

(30 citation statements)

References 18 publications

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“…Hyaloperonospora arabidopsidis ( Hpa ) strains were propagated and prepared as previously described [56], [87]. Seven day-old soil-grown seedlings were sprayed with a spore suspension (5×10 4 spores/ml in water) containing the virulent strain Hpa Emco5 or the avirulent strain Hpa Emoy2.…”

Section: Methodsmentioning

confidence: 99%

Crosstalk between the Circadian Clock and Innate Immunity in Arabidopsis

et al. 2013

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The circadian clock integrates temporal information with environmental cues in regulating plant development and physiology. Recently, the circadian clock has been shown to affect plant responses to biotic cues. To further examine this role of the circadian clock, we tested disease resistance in mutants disrupted in CCA1 and LHY, which act synergistically to regulate clock activity. We found that cca1 and lhy mutants also synergistically affect basal and resistance gene-mediated defense against Pseudomonas syringae and Hyaloperonospora arabidopsidis. Disrupting the circadian clock caused by overexpression of CCA1 or LHY also resulted in severe susceptibility to P. syringae. We identified a downstream target of CCA1 and LHY, GRP7, a key constituent of a slave oscillator regulated by the circadian clock and previously shown to influence plant defense and stomatal activity. We show that the defense role of CCA1 and LHY against P. syringae is at least partially through circadian control of stomatal aperture but is independent of defense mediated by salicylic acid. Furthermore, we found defense activation by P. syringae infection and treatment with the elicitor flg22 can feedback-regulate clock activity. Together this data strongly supports a direct role of the circadian clock in defense control and reveal for the first time crosstalk between the circadian clock and plant innate immunity.

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Section: Methodsmentioning

confidence: 99%

Crosstalk between the Circadian Clock and Innate Immunity in Arabidopsis

et al. 2013

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“…Strain propagation and preparation were conducted as previously described (Song et al, 2004; McDowell et al, 2010). Hpa Noco2 spores (5 × 10 4 spores/ml in water) were sprayed on 7-day-old soil-grown seedlings.…”

Section: Methodsmentioning

confidence: 99%

Overexpression of a citrus NDR1 ortholog increases disease resistance in Arabidopsis

Zhang

Albrecht

et al. 2013

Front. Plant Sci.

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Emerging devastating diseases, such as Huanglongbing (HLB) and citrus canker, have caused tremendous losses to the citrus industry worldwide. Genetic engineering is a powerful approach that could allow us to increase citrus resistance against these diseases. The key to the success of this approach relies on a thorough understanding of defense mechanisms of citrus. Studies of Arabidopsis and other plants have provided a framework for us to better understand defense mechanisms of citrus. Salicylic acid (SA) is a key signaling molecule involved in basal defense and resistance (R) gene-mediated defense against broad-spectrum pathogens. The Arabidopsis gene NDR1 (NON-RACE-SPECIFIC DISEASE RESISTANCE 1) is a positive regulator of SA accumulation and is specifically required for signaling mediated by a subset of R genes upon recognition of their cognate pathogen effectors. Our bioinformatic analysis identified an ortholog of NDR1 from citrus, CsNDR1. Overexpression of CsNDR1 complemented susceptibility conferred by the Arabidopsis ndr1-1 mutant to Pseudomonas syringae strains and also led to enhanced resistance to an oomycete pathogen Hyaloperonospora arabidopsidis. Such heightened resistance is associated with increased SA production and expression of the defense marker gene PATHOGENESIS RELATED 1 (PR1). In addition, we found that expression of PR1 and accumulation of SA were induced to modest levels in citrus infected with Candidatus Liberibacter asiaticus, the bacterial pathogen associated with HLB disease. Thus, our data suggest that CsNDR1 is a functional ortholog of Arabidopsis NDR1. Since Ca. L. asiaticus infection only activates modest levels of defense responses in citrus, we propose that genetically increasing SA/NDR1-mediated pathways could potentially lead to enhanced resistance against HLB, citrus canker, and other destructive diseases challenging global citrus production.

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“…Hpa isolate Emco5 infections were performed as described (McDowell et al, 2011) with suspensions of 5 3 10 4 spores/mL, sprayed on 2-weekold seedlings under short-day conditions and scored 2 weeks after infection by counting sporangiophores. For the visualization of cell death, plants were briefly boiled in a 50% ethanol trypan blue-lactophenol solution and cleared with chloral hydrate overnight as described.…”

Section: Pathogen Infection Assaysmentioning

confidence: 99%

The Ubiquitin Ligase PUB22 Targets a Subunit of the Exocyst Complex Required for PAMP-Triggered Responses in Arabidopsis

et al. 2012

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Plant pathogens are perceived by pattern recognition receptors, which are activated upon binding to pathogen-associated molecular patterns (PAMPs). Ubiquitination and vesicle trafficking have been linked to the regulation of immune signaling. However, little information exists about components of vesicle trafficking involved in immune signaling and the mechanisms that regulate them. In this study, we identified Arabidopsis thaliana Exo70B2, a subunit of the exocyst complex that mediates vesicle tethering during exocytosis, as a target of the plant U-box-type ubiquitin ligase 22 (PUB22), which acts in concert with PUB23 and PUB24 as a negative regulator of PAMP-triggered responses. We show that Exo70B2 is required for both immediate and later responses triggered by all tested PAMPs, suggestive of a role in signaling. Exo70B2 is also necessary for the immune response against different pathogens. Our data demonstrate that PUB22 mediates the ubiquitination and degradation of Exo70B2 via the 26S Proteasome. Furthermore, degradation is regulated by the autocatalytic turnover of PUB22, which is stabilized upon PAMP perception. We therefore propose a mechanism by which PUB22-mediated degradation of Exo70B2 contributes to the attenuation of PAMP-induced signaling.

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Propagation, Storage, and Assays with Hyaloperonospora arabidopsidis: A Model Oomycete Pathogen of Arabidopsis

Cited by 25 publications

References 18 publications

Crosstalk between the Circadian Clock and Innate Immunity in Arabidopsis

Crosstalk between the Circadian Clock and Innate Immunity in Arabidopsis

Overexpression of a citrus NDR1 ortholog increases disease resistance in Arabidopsis

The Ubiquitin Ligase PUB22 Targets a Subunit of the Exocyst Complex Required for PAMP-Triggered Responses in Arabidopsis

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