scholarly journals Arabidopsis JASMONATE-INDUCED OXYGENASES down-regulate plant immunity by hydroxylation and inactivation of the hormone jasmonic acid

2017 ◽  
Author(s):  
Lotte Caarls ◽  
Joyce Elberse ◽  
Mo Awwanah ◽  
Nora R. Ludwig ◽  
Michel de Vries ◽  
...  
Keyword(s):  
Gene Expression ◽  
Jasmonic Acid ◽  
Plant Immunity ◽  
Defense Responses ◽  
Mamestra Brassicae ◽  
Loss Of Function ◽  
Defense Gene Expression ◽  
Quadruple Mutant ◽  
Arabidopsis Mutant

ABSTRACTThe phytohormone jasmonic acid (JA) is vital in plant defense and development. Although biosynthesis of JA and activation of JA-responsive gene expression by the bioactive form JA-isoleucine (JA-Ile) have been well-studied, knowledge on JA metabolism is incomplete. In particular, the enzyme that hydroxylates JA to 12-OH-JA, an inactive form of JA that accumulates after wounding and pathogen attack, is unknown. Here, we report the identification of four paralogous 2-oxoglutarate/Fe(II)-dependent oxygenases in Arabidopsis thaliana as JA hydroxylases and show that they down-regulate JA-dependent responses. As they are induced by JA we named them JASMONATE-INDUCED OXYGENASEs (JOXs). Concurrent mutation of the four genes in a quadruple Arabidopsis mutant resulted in increased defense gene expression and increased resistance to the necrotrophic fungus Botrytis cinerea and the caterpillar Mamestra brassicae. In addition, root and shoot growth of the plants was inhibited. Metabolite analysis of leaves showed that loss of function of the four JOX enzymes resulted in over-accumulation of JA and in reduced turnover of JA into 12-OH-JA. Transformation of the quadruple mutant with each JOX gene strongly reduced JA levels, demonstrating that all four JOXs inactivate JA in plants. The in vitro catalysis of 12-OH-JA from JA by recombinant enzyme could be confirmed for three JOXs. The identification of the enzymes responsible for hydroxylation of JA reveals a missing step in JA metabolism, which is important for the inactivation of the hormone and subsequent down-regulation of JA-dependent defenses.SIGNIFICANCE STATEMENTIn plants, the hormone jasmonic acid (JA) is synthesized in response to attack by pathogens and herbivores, leading to activation of defense responses. Rapidly following JA accumulation, the hormone is metabolized, presumably to prevent inhibitive effects of high JA levels on growth and development. The enzymes that directly inactivate JA were so far unknown. Here, we identify four jasmonate-induced oxygenases (JOXs) in Arabidopsis that hydroxylate jasmonic acid to form inactive 12-OH-JA. A mutant that no longer produces the four enzymes hyperaccumulates JA, exhibits reduced growth, and is highly resistant to attackers that are sensitive to JA-dependent defense. The JOX enzymes thus play an important role in determining the amplitude and duration of JA responses to balance the growth-defense tradeoff.

scholarly journals Arabidopsis JASMONATE-INDUCED OXYGENASES down-regulate plant immunity by hydroxylation and inactivation of the hormone jasmonic acid

2017 ◽  
Vol 114 (24) ◽  
pp. 6388-6393 ◽  
Author(s):  
Lotte Caarls ◽  
Joyce Elberse ◽  
Mo Awwanah ◽  
Nora R. Ludwig ◽  
Michel de Vries ◽  
...  
Keyword(s):  
Gene Expression ◽  
Jasmonic Acid ◽  
Plant Immunity ◽  
Mamestra Brassicae ◽  
Loss Of Function ◽  
Defense Gene Expression ◽  
Defense Gene ◽  
Inactive Form ◽  
Quadruple Mutant

The phytohormone jasmonic acid (JA) is vital in plant defense and development. Although biosynthesis of JA and activation of JA-responsive gene expression by the bioactive form JA-isoleucine have been well-studied, knowledge on JA metabolism is incomplete. In particular, the enzyme that hydroxylates JA to 12-OH-JA, an inactive form of JA that accumulates after wounding and pathogen attack, is unknown. Here, we report the identification of four paralogous 2-oxoglutarate/Fe(II)–dependent oxygenases in Arabidopsis thaliana as JA hydroxylases and show that they down-regulate JA-dependent responses. Because they are induced by JA we named them JASMONATE-INDUCED OXYGENASES (JOXs). Concurrent mutation of the four genes in a quadruple Arabidopsis mutant resulted in increased defense gene expression and increased resistance to the necrotrophic fungus Botrytis cinerea and the caterpillar Mamestra brassicae. In addition, root and shoot growth of the plants was inhibited. Metabolite analysis of leaves showed that loss of function of the four JOX enzymes resulted in overaccumulation of JA and in reduced turnover of JA into 12-OH-JA. Transformation of the quadruple mutant with each JOX gene strongly reduced JA levels, demonstrating that all four JOXs inactivate JA in plants. The in vitro catalysis of 12-OH-JA from JA by recombinant enzyme could be confirmed for three JOXs. The identification of the enzymes responsible for hydroxylation of JA reveals a missing step in JA metabolism, which is important for the inactivation of the hormone and subsequent down-regulation of JA-dependent defenses.

scholarly journals The Arabidopsis mediator complex subunit 8 regulates oxidative stress responses

2021 ◽  
Author(s):  
Huaming He ◽  
Jordi Denecker ◽  
Katrien Van Der Kelen ◽  
Patrick Willems ◽  
Robin Pottie ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Gene Expression ◽  
Salicylic Acid ◽  
Jasmonic Acid ◽  
Stress Responses ◽  
Negative Regulator ◽  
Mediator Complex ◽  
Defense Gene Expression ◽  
A Genome ◽  
Oxidative Stress Responses

Abstract Signaling events triggered by hydrogen peroxide (H2O2) regulate plant growth and defense by orchestrating a genome-wide transcriptional reprogramming. However, the specific mechanisms that govern H2O2-dependent gene expression are still poorly understood. Here, we identify the Arabidopsis Mediator complex subunit MED8 as a regulator of H2O2 responses. The introduction of the med8 mutation in a constitutive oxidative stress genetic background (catalase-deficient, cat2) was associated with enhanced activation of the salicylic acid pathway and accelerated cell death. Interestingly, med8 seedlings were more tolerant to oxidative stress generated by the herbicide methyl viologen (MV) and exhibited transcriptional hyperactivation of defense signaling, in particular salicylic acid- and jasmonic acid-related pathways. The med8-triggered tolerance to MV was manipulated by the introduction of secondary mutations in salicylic acid and jasmonic acid pathways. In addition, analysis of the Mediator interactome revealed interactions with components involved in mRNA processing and microRNA biogenesis, hence expanding the role of Mediator beyond transcription. Notably, MED8 interacted with the transcriptional regulator NEGATIVE ON TATA-LESS, NOT2, to control the expression of H2O2-inducible genes and stress responses. Our work establishes MED8 as a component regulating oxidative stress responses and demonstrates that it acts as a negative regulator of H2O2-driven activation of defense gene expression.

scholarly journals HOS15 is a transcriptional corepressor of NPR1-mediated gene activation of plant immunity

2020 ◽  
Vol 117 (48) ◽  
pp. 30805-30815
Author(s):  
Mingzhe Shen ◽  
Chae Jin Lim ◽  
Junghoon Park ◽  
Jeong Eun Kim ◽  
Dongwon Baek ◽  
...  
Keyword(s):  
Gene Expression ◽  
Ubiquitin Ligase ◽  
Transcriptional Activation ◽  
Plant Immunity ◽  
Gene Activation ◽  
Transcriptional Corepressor ◽  
Defense Gene Expression ◽  
Dynamic Regulation ◽  
Defense Gene ◽  
Transcriptional Corepressors

Transcriptional regulation is a complex and pivotal process in living cells. HOS15 is a transcriptional corepressor. Although transcriptional repressors generally have been associated with inactive genes, increasing evidence indicates that, through poorly understood mechanisms, transcriptional corepressors also associate with actively transcribed genes. Here, we show that HOS15 is the substrate receptor for an SCF/CUL1 E3 ubiquitin ligase complex (SCFHOS15) that negatively regulates plant immunity by destabilizing transcriptional activation complexes containing NPR1 and associated transcriptional activators. In unchallenged conditions, HOS15 continuously eliminates NPR1 to prevent inappropriate defense gene expression. Upon defense activation, HOS15 preferentially associates with phosphorylated NPR1 to stimulate rapid degradation of transcriptionally active NPR1 and thus limit the extent of defense gene expression. Our findings indicate that HOS15-mediated ubiquitination and elimination of NPR1 produce effects contrary to those of CUL3-containing ubiquitin ligase that coactivate defense gene expression. Thus, HOS15 plays a key role in the dynamic regulation of pre- and postactivation host defense.

scholarly journals The Xanthomonas type-III effector protein XopS stabilizes CaWRKY40a to regulate defense hormone responses and preinvasion immunity in pepper (Capsicum annuum)

2021 ◽  
Author(s):  
Margot Raffeiner ◽  
Suayib Üstün ◽  
Tiziana Guerra ◽  
Daniela Spinti ◽  
Maria Fitzner ◽  
...  
Keyword(s):  
Gene Expression ◽  
Xanthomonas Campestris ◽  
Stomatal Closure ◽  
Ectopic Expression ◽  
Defense Responses ◽  
Dependent Manner ◽  
Plant Tolerance ◽  
Defense Gene Expression ◽  
Type Iii Effector ◽  
Type Iii

A critical component of plant immunity against invading pathogens is the rapid transcriptional reprogramming of the attacked cell to minimize virulence. Many adapted plant bacterial pathogens use type III effector (T3E) proteins to interfere with plant defense responses, including the induction of immunity genes. The elucidation of effector function is essential to understanding bacterial pathogenesis. Here, we show that XopS, a T3E of Xanthomonas campestris pv. vesicatoria (Xcv), interacts with and inhibits the proteasomal degradation of the transcriptional regulator of defense gene expression WRKY40. Virus-induced gene silencing of WRKY40 in pepper enhanced plant tolerance towards Xcv infection, indicating it represses immunity. Stabilization of WRKY40 by XopS reduces the expression of its targets including salicylic acid (SA)-responsive genes and the jasmonic acid (JA) signaling repressor JAZ8. Xcv bacteria lacking XopS display significantly reduced virulence when surface inoculated onto susceptible pepper leaves. XopS delivery by Xcv, as well as ectopic expression of XopS in Arabidopsis or Nicotiana benthamiana prevented stomatal closure in response to bacteria and biotic elicitors in a WRKY40 dependent manner. This suggests that XopS interferes with preinvasion as well as with apoplastic defense by manipulating WRKY40 stability and gene expression eventually altering phytohormone crosstalk to promote pathogen proliferation.

scholarly journals A putative nuclear copper chaperone promotes plant immunity in Arabidopsis

2020 ◽  
Vol 71 (20) ◽  
pp. 6684-6696 ◽  
Author(s):  
Long-Xiang Chai ◽  
Kai Dong ◽  
Song-Yu Liu ◽  
Zhen Zhang ◽  
Xiao-Peng Zhang ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Plant Immunity ◽  
Copper Chaperone ◽  
Copper Binding ◽  
Nuclear Speckles ◽  
Defense Gene Expression ◽  
Copper Chaperones ◽  
Plant Nucleus

Abstract Copper is essential for many metabolic processes but must be sequestrated by copper chaperones. It is well known that plant copper chaperones regulate various physiological processes. However, the functions of copper chaperones in the plant nucleus remain largely unknown. Here, we identified a putative copper chaperone induced by pathogens (CCP) in Arabidopsis thaliana. CCP harbors a classical MXCXXC copper-binding site (CBS) at its N-terminus and a nuclear localization signal (NLS) at its C-terminus. CCP mainly formed nuclear speckles in the plant nucleus, which requires the NLS and CBS domains. Overexpression of CCP induced PR1 expression and enhanced resistance against Pseudomonas syringae pv. tomato DC3000 compared with Col-0 plants. Conversely, two CRISPR/Cas9-mediated ccp mutants were impaired in plant immunity. Further biochemical analyses revealed that CCP interacted with the transcription factor TGA2 in vivo and in vitro. Moreover, CCP recruits TGA2 to the PR1 promoter sequences in vivo, which induces defense gene expression and plant immunity. Collectively, our results have identified a putative nuclear copper chaperone required for plant immunity and provided evidence for a potential function of copper in the salicylic pathway.

scholarly journals Defense Gene Expression of Vigna radiata (L.) Wilczek., against Cercospora Leaf Spots (CLS)

2019 ◽  
pp. 1-8
Author(s):  
Deepak K. Koche ◽  
Arvind D. Chaudhary
Keyword(s):  
Vigna Radiata ◽  
Defense Mechanism ◽  
Indian Subcontinent ◽  
Disease Incidence ◽  
Defense Responses ◽  
Pr Proteins ◽  
Early Screening ◽  
Cercospora Leaf Spot ◽  
Defense Gene Expression

Most cultivars of Vigna radiata (L) Wilczek grown in Indian subcontinent are susceptible to various biotic and abiotic stresses. Cercospora leaf spot (CLS) is a major biotic stress resulting in poor yield of this crop. Therefore, it is essential to investigate resistance status of different cultivars to CLS and develop effective strategy. Present investigation was focused on the role of biochemical compounds in resistance response of this crop to CLS in naturally grown population and after artificial induction with pathogen derived elicitor. The defense responses in vivo and in vitro were analyzed in the form of phytoalexin genestein, PAL and PR- proteins in their leaves. PR-proteins, PAL and genestein were assayed employing established protocols. In naturally grown population, four cultivars- Kopergaon, TARM-1, TARM-2 and TARM-18 showed lesser accumulation of genestein and lower level of PAL and PR- proteins. However, Pant M-3, ML-1037 and ML-936 showed resistant interaction with very high accumulation of genestein, PAL and PR proteins. Similar trends of accumulation of these biochemicals were observed in in vitro condition after elicitation with pathogen derived elicitor. The correlation study showed that the cultivars with lower defense related expression showed high disease incidence (51-61%) and with higher defense related expression were with less than 5% CLS incidence. It could be stated that PR-proteins, PAL and genestein has prominent role in defense mechanism of mungbean against CLS  as biochemical markers and further their utility in early screening for disease resistance of crop plants could be explored.

scholarly journals The Arabidopsis ORA59 coordinates jasmonic acid- and ethylene-responsive gene expression to regulate plant immunity

2021 ◽  
Author(s):  
Young Nam Yang ◽  
Youngseong Kim ◽  
Hyeri Kim ◽  
Su Jin Kim ◽  
Kwang-Moon Cho ◽  
...  
Keyword(s):  
Gene Expression ◽  
Jasmonic Acid ◽  
Plant Immunity ◽  
Gene Promoters ◽  
Response Factors ◽  
Cis Element ◽  
Transcriptional Reprogramming ◽  
Gcc Box ◽  
Gene Expression Dynamics ◽  
Direct Binding

Jasmonic acid (JA) and ethylene (ET) signaling modulate plant defense against necrotrophic pathogens. These hormone pathways lead to transcriptional reprogramming, which is a major part of plant immunity and requires the roles of transcription factors. ET response factors are responsible for the transcriptional regulation of JA/ET-responsive defense genes, among which ORA59 functions as a key regulator of this process and has been implicated in the JA-ET crosstalk. Here, we identified the ERELEE4 as an ORA59-binding cis-element, in addition to the well-characterized GCC box, demonstrating that ORA59 regulates JA/ET-responsive genes through direct binding to these elements in the gene promoters. Notably, ORA59 exhibited differential preference for the GCC box and ERELEE4, depending on whether ORA59 activation is achieved by JA and ET, respectively. Our results provide insights into how ORA59 can generate specific patterns of gene expression dynamics through JA and ET hormone pathways.

ARID1a as a marker of prognosis and increased sensitivity to CDK4/6, mTOR 1/2 and Src homology region 2 phosphatase (SHP 1/2) inhibitors in breast cancer (BC).

2019 ◽  
Vol 37 (15_suppl) ◽  
pp. 1082-1082 ◽  
Author(s):  
Veronica Mariotti ◽  
Howard L. McLeod ◽  
Hatem Hussein Soliman
Keyword(s):  
Gene Expression ◽  
Cell Lines ◽  
Sensitivity Analyses ◽  
Tissue Loss ◽  
Loss Of Function ◽  
Her2 Receptor ◽  
Luminal A ◽  
Genomic Databases ◽  
Metastatic Tissue

1082 Background: ARID1a (AT Rich Interactive Domain 1A) is part of the SWI/SNF complex, which regulates gene transcription, and is believed to be a tumor suppressor gene. Low ARID1a expression has been associated with poor prognosis in BC. The aim of this study was to explore the clinical significance of ARID1a mutation and expression loss, and its potential as a therapeutic target in BC. Methods: We analyzed publicly available genomic databases to study the clinical implication of ARID1a mutations and gene expression in BC. Results: ARID1a was mutated in ~5-7 % of BCs within TCGA/METABRIC/MSK (5511 samples), but did not show differences in frequency between histology, grade, or estrogen receptor (ER)/HER2 receptor status. MSK metastatic tissue samples had higher incidence of ARID1a mutation compared to primary tumor samples (7.6% vs 4.4%, χ2 P = 0.0073). Analysis of ARID1a in KMPLOT showed that lower gene expression was associated with worse relapse-free survival and overall survival across all BCs, but the difference was primarily in molecularly classified luminal A tumors. Mutations in ARID1a did not show an association with outcomes in TCGA/METABRIC/MSK datasets. Pathway analysis of ARID1a showed it is involved in regulating ER ligand driven signaling and interacts with targets regulated by CDK4 and mTOR activity. CancerRxgene drug sensitivity analyses on BC cell lines revealed that ARID1a mutated BC cell lines were significantly more sensitive to palbociclib, SHP1/2, and mTOR1/2 inhibitors compared to ARID1a wildtype cell lines. Conclusions: Reduced activity of ARID1a in luminal BC cells may negatively affect prognosis by altering ER signaling leading to activation of druggable resistance mechanisms, particularly in metastatic tissue. Loss of function ARID1a mutations may sensitize cancer cells to CDK4/6, mTOR1/2, and SHP1/2 inhibitors in vitro. Further research in ARID1a mutated ER+ BCs using combinations of these inhibitors is warranted.

ASXL1 Mutations Promote Myeloid Transformation Through Inhibition of PRC2-Mediated Gene Repression

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 405-405 ◽  
Author(s):  
Omar Abdel-Wahab ◽  
Mazhar Adli ◽  
Lindsay Saunders ◽  
Jie Gao ◽  
Alan H. Shih ◽  
...  
Keyword(s):  
Gene Expression ◽  
Research Funding ◽  
Hematopoietic Cells ◽  
Loss Of Function ◽  
Genome Wide ◽  
Hoxa Gene Expression ◽  
Primary Leukemia ◽  
Hoxa Gene

Abstract Abstract 405 Somatic mutations in ASXL1 have been identified in patients with myeloid malignancies and are associated with worsened overall survival in AML and MDS patients. However the mechanisms of myeloid transformation of ASXL1 mutations had not been delineated. We therefore performed extensive in vitro and in vivo studies to assess the functional implications of ASXL1 mutations in the hematopoietic compartment. Transcriptional and Western blot analysis demonstrated loss of ASXL1 protein in primary leukemia samples with endogenous ASXL1 mutations indicating that these mutations are loss-of-function disease alleles. Further, ASXL1 depletion by shRNA in normal and malignant hematopoietic cells leads to robust upregulation of a set of genes including the posterior HOXA cluster (HoxA5-HoxA13). Increased HoxA gene expression was confirmed in human hematopoietic stem progenitor cells targeted with ASXL1 siRNA and in mice with conditional deletion of Asxl1 in the hematopoietic compartment. Previous studies in Drosophila had revealed that Asxl forms the polycomb-repressive deubiquitinase (PR-DUB) complex with BAP1, which normally opposes the function of polycomb repressive complex 1 (PRC1) by removing H2AK119 ubiquitination. We verified that wild-type, but not mutant ASXL1 associates with BAP1 in co-immunoprecipitation studies. However, BAP1 depletion in hematopoietic cells did not result in significant changes in HoxA gene expression, suggesting that ASXL1 regulates gene expression in hematopoietic cells independent of its role in the PR-DUB complex. We therefore performed CHIP sequencing for known activating and repressive chromatin marks and histone mass spectrometry to elucidate the genome-wide effects of ASXL1 loss on chromatin state in hematopoietic cells. This allowed us to show that ASXL1 loss resulted in genome-wide loss of the transcriptionally repressive mark H3K27me3 in hematopoietic cells and primary patient samples with ASXL1 mutations. These data were supported by western blot analysis and histone mass spectrometry demonstrating a significant loss of H3K27 trimethylation in ASXL1-mutant cells. Moreover, ASXL1 mutations in primary leukemia samples are characterized by loss of H3K27 trimethylation at the HoxA locus. These data led us to hypothesize that ASXL1 interacts with the PRC2 complex; co-immunoprecipitation studies revealed that ASXL1 associates with members of the PRC2 complex including EZH2 and SUZ12 but not with the PRC1 repressive complex. Importantly, ASXL1 downregulation resulted in loss of EZH2 recruitment to the HOXA locus indicating a role of ASXL1 in recruiting the PRC2 complex to known leukemogenic loci. We next assessed the effects of ASXL1 loss in vivo by generating a conditional knock-out model of ASXL1 and also by employing shRNA to deplete ASXL1 in hematopoietic cells expressing the NRASG12D oncogene. Consonant with the in vitro data, we observed HOXA9 overexpression with ASXL1 loss/depletion in vivo. Preliminary analysis reveals that conditional, hematopoietic specific ASXL1-knockout (ASXL1fl/fl Vav-Cre) mice are characterized by progressive expansion of LSK and myeloid progenitor cells in mice less than 6 months of age. After 6 months of age a significant proportion of ASXL1fl/fl Vav-Cre mice developed leukocytosis, anemia, thrombocytopenia, and splenomegaly; pathologic analysis of tissues revealed a phenotype consistent with myelodysplasia with myeloproliferative features. Moreover, loss of ASXL1 in cooperation with expression of NRasG12D resulted in impaired survival, increased myeloproliferation, and progressive anemia consistent with MPN/MDS in vivo. Taken together, these results reveal that ASXL1 mutations result in a loss-of-function and suggest a specific role for ASXL1 in epigenetic regulation of gene expression by facilitating PRC2-mediated transcriptional repression of known leukemic oncogenes. Moreover, our in vivo data validate the importance of ASXL1 mutations in the pathogenesis of myeloid malignancies and provide insight into how mutations that inhibit PRC2 function contribute to myeloid transformation through epigenetic dysregulation of specific target genes. Disclosures: Carroll: Agios Pharmaceuticals: Research Funding; TetraLogic Pharmaceuticals: Research Funding; Sanofi Aventis Corporation: Research Funding; Glaxo Smith Kline, Inc.: Research Funding.

scholarly journals Ulvan, a Sulfated Polysaccharide from Green Algae, Activates Plant Immunity through the Jasmonic Acid Signaling Pathway

2010 ◽  
Vol 2010 ◽  
pp. 1-11 ◽  
Author(s):  
Valérie Jaulneau ◽  
Claude Lafitte ◽  
Christophe Jacquet ◽  
Sylvie Fournier ◽  
Sylvie Salamagne ◽  
...  
Keyword(s):  
Gene Expression ◽  
Jasmonic Acid ◽  
Green Algae ◽  
Plant Immunity ◽  
Gene Promoter ◽  
Gene Expression Signature ◽  
Sulfated Polysaccharide ◽  
Promoter Gene ◽  
Potential Reservoir ◽  
Hormonal Mutants

The industrial use of elicitors as alternative tools for disease control needs the identification of abundant sources of them. We report on an elicitor obtained from the green algaeUlvaspp. A fraction containing most exclusively the sulfated polysaccharide known as ulvan-induced expression of a GUS gene placed under the control of a lipoxygenase gene promoter. Gene expression profiling was performed upon ulvan treatments onMedicago truncatulaand compared to phytohormone effects. Ulvan induced a gene expression signature similar to that observed upon methyl jasmonate treatment (MeJA). Involvement of jasmonic acid (JA) in ulvan response was confirmed by detecting induction of protease inhibitory activity and by hormonal profiling of JA, salicylic acid (SA) and abscisic acid (ABA). Ulvan activity on the hormonal pathway was further consolidated by usingArabidopsishormonal mutants. Altogether, our results demonstrate that green algae are a potential reservoir of ulvan elicitor which acts through the JA pathway.

Sign in / Sign up

Export Citation Format

Share Document