Members of the <i>Arabidopsis</i> WRKY Group III Transcription Factors Are Part of Different Plant Defense Signaling Pathways

Kalde, Monika; Barth, Meike; Somssich, Imre E.; Lippok, Bernadette

doi:10.1094/mpmi.2003.16.4.295

Cited by 266 publications

(218 citation statements)

References 54 publications

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“…Plant immune responses are associated with the concerted modulation of a large number of different WRKY transcripts and proteins [15,[34][35][36]37 ]. Upon triggering of SAdependent defenses, at least 49 AtWRKY genes exhibited differential regulation representing separate waves of transcript accumulation or repression [34].…”

Section: The Wrky Webmentioning

confidence: 99%

Networks of WRKY transcription factors in defense signaling

Eulgem

Somssich

2007

Current Opinion in Plant Biology

1,168

890

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Members of the complex family of WRKY transcription factors have been implicated in the regulation of transcriptional reprogramming associated with plant immune responses. Recently genetic evidence directly proving their significance as positive and negative regulators of disease resistance has accumulated. WRKY genes were shown to be functionally connected forming a transcriptional network composed of positive and negative feedback loops and feed-forward modules. Within a web of partially redundant elements some WRKY factors hold central positions mediating fast and efficient activation of defense programs. A key mechanism triggering strong immune responses appears to be based on the inactivation of defense-suppressing WRKY proteins. [13,15,16 ]. Moreover, AtWRKY70 is required for both basal defense and full R-gene (RPP4)-mediated disease resistance against the oomycete Hyaloperonospora parasitica [17 ] Similarly, mutants compromised in AtWRKY33 were more susceptible to infection by B. cinerea and Alternaria brassicicola [18]. Several WRKY factors act as negative regulators of resistance. For instance, basal plant resistance triggered by a virulent P. syringae strain was enhanced in Atwrky7 and Atwrky11/Atwrky17 insertional mutants [19 ,20] thereby also revealing partly redundant functions for these closely related TFs.A small clade (subgroup IIa) of WRKY genes, comprising AtWRKY18, AtWRKY40, and AtWRKY60, play important and partly redundant functions in regulating plant disease resistance. Xu et al. [21 ] showed that Atwrky18/Atwrky40 and Atwrky18/Atwrky60 double mutants were more resistant to P. syringae DC3000 but more susceptible to B. cinerea infection. Atwrky18/Atwrky40 double mutants were also highly resistant toward an otherwise virulent powdery mildew, Golovinomyces orontii [22 ]. In both studies single Atwrky mutants behaved similar to wild-type plants. Interestingly, AtWRKY18 was also identified as a positive regulator required for full SAR, but here AtWRKY40 does not seem to be involved [16 ]. Differences in the experimental set-ups employed by Xu et al.[21 ] and Wang et al.[16 ] may be responsible for the apparent discrepancy observed in the Atwrky18 mutant when challenged by virulent P. syringae strains. Xu et al. used 10-fold higher bacterial inoculum that may have masked the effect on basal resistance caused by loss-ofAtWRKY18 function.In barley, two IIa WRKY members were shown to suppress basal defense to virulent Blumeria graminis in silencing and transient overexpression experiments [22 ,23]. Unfortunately, a solution structure exists only for the common zinc-finger-containing WRKY DNA-binding domain [27 ] and thus no topological information regarding subgroup-specific motifs are available. Nevertheless, some of these structural hallmarks, which appear largely conserved throughout the plant kingdom, have recently been associated with defined molecular or biological functions. It is very likely that they functionally link individual WRKY molecules to each other or to additional de...

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Section: The Wrky Webmentioning

confidence: 99%

Networks of WRKY transcription factors in defense signaling

Eulgem

Somssich

2007

Current Opinion in Plant Biology

1,168

890

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“…5B). WRKY proteins are essential regulators in plant immune responses (20,21). WRKY38 and WRKY60 are up-regulated during plant defense activation, whereas WRKY 33, encoding a negative regulator of the defense response, is down-regulated (21-23).…”

Section: Genes and Metabolic Pathways Important In The F1 Hybrid Phenmentioning

confidence: 99%

Hybrid mimics and hybrid vigor in Arabidopsis

Wang

Greaves

Groszmann

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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F1 hybrids can outperform their parents in yield and vegetative biomass, features of hybrid vigor that form the basis of the hybrid seed industry. The yield advantage of the F1 is lost in the F2 and subsequent generations. In Arabidopsis, from F2 plants that have a F1-like phenotype, we have by recurrent selection produced pure breeding F5/F6 lines, hybrid mimics, in which the characteristics of the F1 hybrid are stabilized. These hybrid mimic lines, like the F1 hybrid, have larger leaves than the parent plant, and the leaves have increased photosynthetic cell numbers, and in some lines, increased size of cells, suggesting an increased supply of photosynthate. A comparison of the differentially expressed genes in the F1 hybrid with those of eight hybrid mimic lines identified metabolic pathways altered in both; these pathways include down-regulation of defense response pathways and altered abiotic response pathways. F6 hybrid mimic lines are mostly homozygous at each locus in the genome and yet retain the large F1-like phenotype. Many alleles in the F6 plants, when they are homozygous, have expression levels different to the level in the parent. We consider this altered expression to be a consequence of transregulation of genes from one parent by genes from the other parent. Transregulation could also arise from epigenetic modifications in the F1. The pure breeding hybrid mimics have been valuable in probing the mechanisms of hybrid vigor and may also prove to be useful hybrid vigor equivalents in agriculture.I n Arabidopsis some ecotypes with similar genome sequences produce F1 hybrids with large increases in vegetative and reproductive yields (1, 2). These results appear to be at variance with the generalization that the larger the genetic distance between parents, the greater the hybrid vigor (3); however, the Arabidopsis ecotypes have different epigenomes that may be important for hybrid vigor (4). In hybrids between C24 and Ler, we found altered levels in two epigenetic systems: 24nt siRNAs and DNA methylation (4, 5). These epigenetic changes appear common among hybrid systems with similar observations being made in maize and rice hybrids (6). The epigenetic changes can correlate with changes in gene expression and contribute to the unique gene expression profile of the F1 hybrid (7). Not all crosses result in hybrid vigor (heterosis); some result in decreased vigor and yield referred to as "hybrid weakness" (8).Heterotic F1 hybrids are featured in agricultural and horticultural crops, and in all species, the yield gains are restricted to the F1 generation. The F2 and subsequent selfed generations are discarded because of reduced yields and heterogeneity of morphological and developmental traits. A hybrid crop system requires an efficient method of F1 hybrid seed production dependent on male sterility in the female parent and synchronous flowering of the male and female parents.QTL analysis in maize and rice has confirmed that hundreds of genome segments contribute to the heterotic phenotype, but the main m...

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“…However, WRKYs are not confined to PR induction. The members of this family (74 in Arabidopsis) have diverse biological functions ranging from stress responses to development [36]. Interestingly, the two developmental processes in which WRKY transcription factors are implicated are trichome development and senescence, and in both cases PCD is indispensable for the normal processes to occur [37,38].…”

Section: Transcription Factors and The Global Transcriptional Reprogrmentioning

confidence: 99%

An extensive microarray analysis of AAL-toxin-induced cell death in Arabidopsis thaliana brings new insights into the complexity of programmed cell death in plants

Gechev

Gadjev

Hille

2004

Cellular and Molecular Life Sciences (CMLS)

129

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An extensive microarray analysis of AAL-toxin-induced cell death in Arabidopsis thaliana brings new insights into the complexity of programmed cell death in plants Gechev, T.S.; Gadjev, I.Z.; Hille, J. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Abstract. A T-DNA knockout of the Arabidopsis homologue of the tomato disease resistance gene Asc was obtained. The asc gene renders plants sensitive to programmed cell death (PCD) triggered by the fungal AAL toxin. To obtain more insights into the nature of AALtoxin-induced cell death and to identify genes of potential importance for PCD, we carried out transcription profiling of AAL-toxin-induced cell death in this knockout with an oligonucleotide array representing 21,500 Arabidopsis genes. Genes responsive to reactive oxygen species (ROS) and ethylene were among the earliest to be upregulated, suggesting that an oxidative burst and production of ethylene played a role in the activation of the cell death. This notion was corroborated by induction of several genes encoding ROS-generating proteins, including a respiratory burst oxidase and germin oxalate oxi- CMLS, Cell. Mol. Life Sci. 61 (2004) 1185 -1197 1420-682X/04/101185-13 DOI 10.1007/s00018-004-4067-2 © Birkhäuser Verlag, Basel, 2004 CMLS Cellular and Molecular Life Sciences dase. Cytochemical studies confirmed the oxidative burst and, in addition, showed synthesis of callose, a feature of the hypersensitive response. A diverse group of transcription factors was also induced. These events were followed by repression of most of the auxin-regulated genes known to be involved in growth and developmental responses. All photosynthesis-related genes were repressed. Blocking the synthesis of ethylene or NO significantly compromised cell death. In addition, we identified a heterogeneous group of early-induced genes, some of them never before associated with PCD. The group of earlyinduced genes included a number of proteases that were previously implicated in developmentally regulated types of PCD, suggesting a more principal role for these proteases in the PCD process. These findings provide new insights into the molecular mechanisms of plant PCD.

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Members of the Arabidopsis WRKY Group III Transcription Factors Are Part of Different Plant Defense Signaling Pathways

Cited by 266 publications

References 54 publications

Networks of WRKY transcription factors in defense signaling

Networks of WRKY transcription factors in defense signaling

Hybrid mimics and hybrid vigor in Arabidopsis

An extensive microarray analysis of AAL-toxin-induced cell death in Arabidopsis thaliana brings new insights into the complexity of programmed cell death in plants

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