The Cuticle Mutant eca2 Modifies Plant Defense Responses to Biotrophic and Necrotrophic Pathogens and Herbivory Insects

We isolated previously several Arabidopsis thaliana mutants with constitutive expression of the early microbe-associated molecular pattern–induced gene ATL2, named eca (expresión constitutiva de ATL2). Here, we further explored the interaction of eca mutants with pest and pathogens. Of all eca mutants, eca2 was more resistant to a fungal pathogen (Botrytis cinerea) and a bacterial pathogen (Pseudomonas syringae) as well as to a generalist herbivorous insect (Spodoptera littoralis). Permeability of the cuticle is increased in eca2; chemical characterization shows that eca2 has a significant reduction of both cuticular wax and cutin. Additionally, we determined that eca2 did not display a similar compensatory transcriptional response, compared with a previously characterized cuticular mutant, and that resistance to B. cinerea is mediated by the priming of the early and late induced defense responses, including salicylic acid– and jasmonic acid–induced genes. These results suggest that ECA2-dependent responses are involved in the nonhost defense mechanism against biotrophic and necrotrophic pathogens and against a generalist insect by modulation and priming of innate immunity and late defense responses. Making eca2 an interesting model to characterize the molecular basis for plant defenses against different biotic interactions and to study the initial events that take place in the cuticle surface of the aerial organs.

Download Full-text

Ethylene and Jasmonic Acid Signaling Affect the NPR1-Independent Expression of Defense Genes Without Impacting Resistance to Pseudomonas syringae and Peronospora parasitica in the Arabidopsis ssi1 Mutant

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2003.16.7.588 ◽

2003 ◽

Vol 16 (7) ◽

pp. 588-599 ◽

Cited By ~ 44

Author(s):

Ashis Nandi ◽

Pradeep Kachroo ◽

Hirotada Fukushige ◽

David F. Hildebrand ◽

Daniel F. Klessig ◽

...

Keyword(s):

Jasmonic Acid ◽

Plant Defense ◽

Pseudomonas Syringae ◽

Defense Mechanism ◽

Constitutive Expression ◽

Defense Responses ◽

Peronospora Parasitica ◽

Defense Genes ◽

Pr Genes ◽

Ja Signaling

Salicylic acid (SA), ethylene, and jasmonic acid (JA) are important signaling molecules in plant defense to biotic stress. An intricate signaling network involving SA, ethylene, and JA fine tunes plant defense responses. SA-dependent defense responses in Arabidopsis thaliana are mediated through NPR1-dependent and -independent mechanisms. We have previously shown that activation of an NPR1-independent defense mechanism confers enhanced disease resistance and constitutive expression of the pathogenesis-related (PR) genes in the Arabidopsis ssi1 mutant. In addition, the ssi1 mutant constitutively expresses the defensin gene PDF1.2. Moreover, SA is required for the ssi1-conferred constitutive expression of PDF1.2 in addition to PR genes. Hence, the ssi1 mutant appears to target a step common to SA- and ethylene- or JA-regulated defense pathways. In the present study, we show that, in addition to SA, ethylene and JA signaling also are required for the ssi1-conferred constitutive expression of PDF1.2 and the NPR1-independent expression of PR-1. Furthermore, the ethylene-insensitive ein2 and JA-insensitive jar1 mutants enhance susceptibility of ssi1 plants to the necrotrophic fungus Botrytis cinerea. However, defects in either the ethylene- or JA-signaling pathways do not compromise ssi1-conferred resistance to the bacterial pathogen Pseudomonas syringae pv. maculicola and the oomycete pathogen Peronospora parasitica. Interestingly, ssi1 exhibits a marginal increase in the levels of ethylene and JA, suggesting that low endogenous levels of these phytohormones are sufficient to activate expression of defense genes. Taken together, our results indicate that although cross talk in ssi1 renders expression of ethylene- or JA-responsive defense genes sensitive to SA and vice versa, it does not affect downstream signaling leading to resistance.

Download Full-text

Caterpillar salivary enzymes: "eliciting" a response

Phytoprotection ◽

10.7202/008904ar ◽

2004 ◽

Vol 85 (1) ◽

pp. 33-37 ◽

Cited By ~ 14

Author(s):

Magali Merkx-Jacques ◽

Jacqueline C. Bede

Keyword(s):

Artificial Diet ◽

Spodoptera Exigua ◽

Induced Defense ◽

Defense Responses ◽

Beet Armyworm ◽

Herbivorous Insect ◽

Plant Responses ◽

Plant Defense Responses ◽

Induced Defense Responses ◽

Bertha Armyworm

Abstract Plants exhibit remarkable plasticity in their ability to differentiate between herbivorous insect species and subtly adjust their defense responses to target distinct pests. One key mechanism used by plants to recognize herbivorous caterpillars is elicitors present in their oral secretions; however, these elicitors not only cause the induction of plant defenses but recent evidence suggests that they may also suppress plant responses. The absence of “expected changes” in induced defense responses of insect-infested plants has been attributed to hydrogen peroxide produced by caterpillar salivary glucose oxidase (GOX). Activity of this enzyme is variable among caterpillar species; it was detected in two generalist caterpillars, the beet armyworm (Spodoptera exigua) and the bertha armyworm (Mamestra configurata), but not in other generalist or specialist caterpillar species tested. In the beet armyworm, GOX activity fluctuated over larval development with high activity associated with the salivary glands of fourth instars. Larval salivary GOX activity of the beet armyworm and the bertha armyworm was observed to be significantly higher in caterpillars reared on artificial diet as compared with those reared on Medicago truncatula plants. This implies that a factor in the diet is involved in the regulation of caterpillar salivary enzyme activity. Therefore, plant diet may be regulating caterpillar oral elicitors that are involved in the regulation of plant defense responses: our goal is to understand these two processes.

Download Full-text

C-Terminal Region of Plant Ferredoxin-Like Protein Is Required to Enhance Resistance to Bacterial Disease in Arabidopsis thaliana

Phytopathology ◽

10.1094/phyto-08-10-0220 ◽

2011 ◽

Vol 101 (6) ◽

pp. 741-749 ◽

Cited By ~ 8

Author(s):

Yi-Hsien Lin ◽

Hsiang-En Huang ◽

Yen-Ru Chen ◽

Pei-Luan Liao ◽

Ching-Lian Chen ◽

...

Keyword(s):

Disease Resistance ◽

Transgenic Plants ◽

Nadph Oxidase ◽

Pseudomonas Syringae ◽

Induced Defense ◽

Defense Responses ◽

Bacterial Disease ◽

Oxidase Gene ◽

Induced Defense Responses ◽

Resistance To Ralstonia Solanacearum

Protein phosphorylation is an important biological process associated with elicitor-induced defense responses in plants. In a previous report, we described how plant ferredoxin-like protein (PFLP) in transgenic plants enhances resistance to bacterial pathogens associated with the hypersensitive response (HR). PFLP possesses a putative casein kinase II phosphorylation (CK2P) site at the C-terminal in which phosphorylation occurs rapidly during defense response. However, the contribution of this site to the enhancement of disease resistance and the intensity of HR has not been clearly demonstrated. In this study, we generated two versions of truncated PFLP, PEC (extant CK2P site) and PDC (deleted CK2P site), and assessed their ability to trigger HR through harpin (HrpZ) derived from Pseudomonas syringae as well as their resistance to Ralstonia solanacearum. In an infiltration assay of HrpZ, PEC intensified harpin-mediated HR; however, PDC negated this effect. Transgenic plants expressing these versions indicate that nonphosphorylated PFLP loses its ability to induce HR or enhance disease resistance against R. solanacearum. Interestingly, the CK2P site of PFLP is required to induce the expression of the NADPH oxidase gene, AtrbohD, which is a reactive oxygen species producing enzyme. This was further confirmed by evaluating the HR on NADPH oxidase in mutants of Arabidopsis. As a result, we have concluded that the CK2P site is required for the phosphorylation of PFLP to enhance disease resistance.

Download Full-text

Molecular characterization of differences between the tomato immune receptors Fls3 and Fls2

10.1101/2020.02.04.934133 ◽

2020 ◽

Author(s):

Robyn Roberts ◽

Alexander E. Liu ◽

Lingwei Wan ◽

Annie M. Geiger ◽

Sarah R. Hind ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Molecular Mechanisms ◽

Bacterial Pathogen ◽

Transcript Abundance ◽

Defense Responses ◽

Structural Features ◽

Host Responses ◽

Pathogen Invasion

AbstractPlants mount defense responses by recognizing indications of pathogen invasion, including microbe-associated molecular patterns (MAMPs). Flagellin from the bacterial pathogen Pseudomonas syringae pv. tomato (Pst) contains two MAMPs, flg22 and flgII-28, that are recognized by tomato receptors Flagellin sensing 2 (Fls2) and Flagellin sensing 3 (Fls3), respectively. It is unknown to what degree each receptor contributes to immunity and if they promote immune responses using the same molecular mechanisms. Characterization of CRISPR/Cas9-generated Fls2 and Fls3 tomato mutants revealed that the two receptors contribute equally to disease resistance both on the leaf surface and in the apoplast. However, striking differences were observed in certain host responses mediated by the two receptors. Compared to Fls2, Fls3 mediated a more sustained production of reactive oxygen species (ROS) and an increase in transcript abundance of 44 tomato genes, with two genes serving as reporters for Fls3. Fls3 had greater in vitro kinase activity and interacted differently with the Pst effector AvrPtoB as compared to Fls2. Using chimeric Fls2/Fls3 proteins, we found that no receptor domain was solely responsible for the Fls3 sustained ROS, suggesting involvement of multiple structural features. This work reveals differences in the immunity outputs between Fls2 and Fls3, suggesting they use distinct molecular mechanisms to activate pattern-triggered immunity in response to flagellin-derived MAMPs.

Download Full-text

Elongator Plays a Positive Role in Exogenous NAD-Induced Defense Responses in Arabidopsis

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-01-16-0005-r ◽

2016 ◽

Vol 29 (5) ◽

pp. 396-404 ◽

Cited By ~ 15

Author(s):

Chuanfu An ◽

Yezhang Ding ◽

Xudong Zhang ◽

Chenggang Wang ◽

Zhonglin Mou

Keyword(s):

Pseudomonas Syringae ◽

Induced Defense ◽

Defense Responses ◽

Rna Modification ◽

Coding Region ◽

Animal Cells ◽

Signal Molecule ◽

Positive Role ◽

Elongator Complex ◽

Induced Defense Responses

Extracellular NAD is emerging as an important signal molecule in animal cells, but its role in plants has not been well-established. Although it has been shown that exogenous NAD+ activates defense responses in Arabidopsis, components in the exogenous NAD+-activated defense pathway remain to be fully discovered. In a genetic screen for mutants insensitive to exogenous NAD+ (ien), we isolated a mutant named ien2. Map-based cloning revealed that IEN2 encodes ELONGATA3 (ELO3)/AtELP3, a subunit of the Arabidopsis Elongator complex, which functions in multiple biological processes, including histone modification, DNA (de)methylation, and transfer RNA modification. Mutations in the ELO3/AtELP3 gene compromise exogenous NAD+-induced expression of pathogenesis-related (PR) genes and resistance to the bacterial pathogen Pseudomonas syringae pv. maculicola ES4326, and transgenic expression of the coding region of ELO3/AtELP3 in elo3/Atelp3 restores NAD+ responsiveness to the mutant plants, demonstrating that ELO3/AtELP3 is required for exogenous NAD+-induced defense responses. Furthermore, mutations in genes encoding the other five Arabidopsis Elongator subunits (ELO2/AtELP1, AtELP2, ELO1/AtELP4, AtELP5, and AtELP6) also compromise exogenous NAD+-induced PR gene expression and resistance to P. syringae pv. maculicola ES4326. These results indicate that the Elongator complex functions as a whole in exogenous NAD+-activated defense signaling in Arabidopsis.

Download Full-text

Characterization of a Novel, Defense-Related Arabidopsis Mutant, cir1, Isolated By Luciferase Imaging

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2002.15.6.557 ◽

2002 ◽

Vol 15 (6) ◽

pp. 557-566 ◽

Cited By ~ 32

Author(s):

Shane L. Murray ◽

Catherine Thomson ◽

Andrea Chini ◽

Nick D. Read ◽

Gary J. Loake

Keyword(s):

Signaling Pathways ◽

Pseudomonas Syringae ◽

Constitutive Expression ◽

Bacterial Pathogen ◽

Negative Regulator ◽

Reactive Oxygen Intermediate ◽

Peronospora Parasitica ◽

Tomato Dc3000 ◽

Pathogen Invasion ◽

Arabidopsis Mutant

In order to identify components of the defense signaling network engaged following attempted pathogen invasion, we generated a novel PR-1∷luciferase (LUC) transgenic line that was deployed in an imaging-based screen to uncover defense-related mutants. The recessive mutant designated cir1 exhibited constitutive expression of salicylic acid (SA), jasmonic acid (JA)/ethylene, and reactive oxygen intermediate-dependent genes. Moreover, this mutation conferred resistance against the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 and a virulent oomycete pathogen Peronospora parasitica Noco2. Epistasis analyses were undertaken between cir1 and mutants that disrupt the SA (npr1, nahG), JA (jar1), and ethylene (ET) (ein2) signaling pathways. While resistance against both P. syringae pv. tomato DC3000 and Peronospora parasitica Noco2 was partially reduced by npr1, resistance against both of these pathogens was lost in an nahG genetic background. Hence, cir1-mediated resistance is established via NPR1-dependent and -independent signaling pathways and SA accumulation is essential for the function of both pathways. While jar1 and ein2 reduced resistance against P. syringae pv. tomato DC3000, these mutations appeared not to impact cir1-mediated resistance against Peronospora parasitica Noco2. Thus, JA and ET sensitivity are required for cir1-mediated resistance against P. syringae pv. tomato DC3000 but not Peronospora parasitica Noco2. Therefore, the cir1 mutation may define a negative regulator of disease resistance that operates upstream of SA, JA, and ET accumulation.

Download Full-text

JUB1 suppresses Pseudomonas syringae-induced defense responses through accumulation of DELLA proteins

Plant Signaling & Behavior ◽

10.1080/15592324.2016.1181245 ◽

2016 ◽

Vol 11 (6) ◽

pp. e1181245 ◽

Cited By ~ 11

Author(s):

Sara Shahnejat-Bushehri ◽

Barbara Nobmann ◽

Annapurna Devi Allu ◽

Salma Balazadeh

Keyword(s):

Pseudomonas Syringae ◽

Induced Defense ◽

Defense Responses ◽

Della Proteins ◽

Induced Defense Responses

Download Full-text

Analysis of Resistance Gene-Mediated Defense Responses in Arabidopsis thaliana Plants Carrying a Mutation in CPR5

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.1998.11.12.1196 ◽

1998 ◽

Vol 11 (12) ◽

pp. 1196-1206 ◽

Cited By ~ 51

Author(s):

Jens Boch ◽

Michelle L. Verbsky ◽

Tara L. Robertson ◽

John C. Larkin ◽

Barbara N. Kunkel

Keyword(s):

Gene Expression ◽

Arabidopsis Thaliana ◽

Resistance Gene ◽

Pseudomonas Syringae ◽

Bacterial Pathogen ◽

Defense Responses ◽

Negative Regulator ◽

Suppressor Mutations ◽

Defense Related Gene ◽

Rapid Activation

In resistant plants, pathogen attack often leads to rapid activation of defense responses that limit multiplication and spread of the pathogen. To investigate the signaling mechanisms underlying this process, we carried out a screen for mutants in the signaling pathway governing resistance in Arabidopsis thaliana to the bacterial pathogen Pseudomonas syringae. This involved screening for suppressor mutations that restored resistance to a susceptible line carrying a mutation in the RPS2 resistance gene. A mutant that conferred resistance by activating defense responses in the absence of pathogens was isolated. This mutant, which carries a mutation at the CPR5 locus and was thus designated cpr5-2, exhibited resistance to P. syringae, spontaneous development of necrotic lesions, elevated PR gene expression in the absence of pathogens, and abnormal trichomes. Resistance gene-mediated defenses, including the hypersensitive response, restriction of pathogen growth, and induction of defense-related gene expression, were functional in cpr5-2 mutant plants. Additionally, in cpr5-2 plants RPS2-mediated induction of PR-1 expression was enhanced, whereas RPM1-mediated induction of ELI3 was not. These findings suggest that CPR5 encodes a negative regulator of the RPS2 signal transduc-tion pathway.

Download Full-text

Role of Benzoic Acid and Lettucenin A in the Defense Response of Lettuce against Soil-Borne Pathogens

Plants ◽

10.3390/plants10112336 ◽

2021 ◽

Vol 10 (11) ◽

pp. 2336

Author(s):

Saskia Windisch ◽

Anja Walter ◽

Narges Moradtalab ◽

Frank Walker ◽

Birgit Höglinger ◽

...

Keyword(s):

Benzoic Acid ◽

Defense Mechanism ◽

Induced Defense ◽

Hyphal Growth ◽

Defense Responses ◽

Soil Culture ◽

Defense Compounds ◽

Soil Borne Pathogens ◽

Induced Defense Responses

Soil-borne pathogens can severely limit plant productivity. Induced defense responses are plant strategies to counteract pathogen-related damage and yield loss. In this study, we hypothesized that benzoic acid and lettucenin A are involved as defense compounds against Rhizoctonia solani and Olpidium virulentus in lettuce. To address this hypothesis, we conducted growth chamber experiments using hydroponics, peat culture substrate and soil culture in pots and minirhizotrons. Benzoic acid was identified as root exudate released from lettuce plants upon pathogen infection, with pre-accumulation of benzoic acid esters in the root tissue. The amounts were sufficient to inhibit hyphal growth of R. solani in vitro (30%), to mitigate growth retardation (51%) and damage of fine roots (130%) in lettuce plants caused by R. solani, but were not able to overcome plant growth suppression induced by Olpidium infection. Additionally, lettucenin A was identified as major phytoalexin, with local accumulation in affected plant tissues upon infection with pathogens or chemical elicitation (CuSO4) and detected in trace amounts in root exudates. The results suggest a two-stage defense mechanism with pathogen-induced benzoic acid exudation initially located in the rhizosphere followed by accumulation of lettucenin A locally restricted to affected root and leaf tissues.

Download Full-text

Contrasting functions of Arabidopsis SUMO1/2 isoforms with SUMO3 intersect to modulate innate immunity and global SUMOylome responses

10.1101/2020.05.15.097535 ◽

2020 ◽

Author(s):

Kishor Dnyaneshwar Ingole ◽

Mritunjay Kasera ◽

Harrold A. van den Burg ◽

Saikat Bhattacharjee

Keyword(s):

Arabidopsis Thaliana ◽

Steady State ◽

Heat Shock ◽

Pseudomonas Syringae ◽

Bacterial Pathogen ◽

Defense Responses ◽

Vital Role ◽

Covalent Attachment ◽

Developmental Defects ◽

Small Proteins

AbstractReversible covalent attachment of SMALL UBIQUITIN-LIKE MODIFIERS (SUMOs) on target proteins regulate diverse cellular process across all eukaryotes. In Arabidopsis thaliana, most mutants with perturbed global SUMOylome display severe impairments in growth and adaptations to physiological stresses. Since SUMOs self-regulate activities of SUMOylation-associated proteins, existence of multiple isoforms introduces possibilities of their functional intersections which remain unexplored especially in plant systems. Using well-established defense responses elicited against virulent and avirulent Pseudomonas syringae pv. tomato strains, we investigated crosstalks in individual and combinatorial Arabidopsis sum mutants. Here we report that while SUM1 and SUM2 additively, but not equivalently suppress basal and TNL-specific immunity via down-regulation of salicylic acid (SA)-dependent responses, SUM3 promotes these defenses genetically downstream of SA. Remarkably, the expression of SUM3 is transcriptionally suppressed by SUMO1 or SUMO2. The loss of SUM3 not only lowers basal or post-bacterial challenge responsive enhancements of SUMO1/2-congugates but also reduces upregulation dynamics of defensive proteins and SUMOylation-associated transcripts. Combining a sum3 mutation partially attenuates heightened immunity of sum1 or sum2 mutants suggesting intricate functional impingements among these isoforms in optimizing immune amplitudes. Similar SUM1-SUM3 intersections also affect global SUMOylome responses to heat-shock affecting most notably the induction of selective heat-shock transcription factors. Overall, our investigations reveal novel insights into auto-regulatory mechanisms among SUMO isoforms in host SUMOylome maintenance and adjustments to environmental challenges.Author SummaryIn plants, similar to animals, protein functions are regulated at multiple levels. One prevalent mode is to allow covalent linkage of small proteins to specific amino acids on targets thereby affecting its fate and function. One such kind of modification named as SUMOylation involves attachment of SUMO proteins. A plant maintains strict control over its pool of SUMOylated proteins (termed SUMOylome) which upon biotic or abiotic stresses are altered to facilitate appropriate responses, returning back to steady-state when the threat subsides. In mutants of the model plant Arabidopsis thaliana having disturbed steady-state SUMOylome, growth and developmental defects ensue. These mutants are auto-immune showing more resistance to infection by the bacterial pathogen Pseudomonas syringae. However, Arabidopsis SUMO-family are comprised of multiple members raising the question about their specificity or functional crosstalks. We discovered that two SUMO members function in coordination to suppress immunity including the repression of a third member which supports defenses. The expression of this third member during pathogen attack or heat-shock influences the responsive changes in the host SUMOylome likely suggesting SUMOs themselves play vital role in these adaptations. Overall, our work highlights novel intersections of SUMO members in mounting stress-specific responses.

Download Full-text