Myzus persicae (green peach aphid) feeding on Arabidopsis thaliana induces a defense response, quantified as reduced aphid progeny production, in infested leaves but not in other parts of the plant. Similarly, infiltration of aphid saliva into Arabidopsis leaves causes only a local increase in aphid resistance. Further characterization of the defense-eliciting salivary components indicates that Arabidopsis recognizes a proteinaceous elicitor with a size between 3 to 10 kD. Genetic analysis using well-characterized Arabidopsis mutant shows that saliva-induced resistance against M. persicae is independent of the known defense signaling pathways involving salicylic acid, jasmonate, and ethylene. Among 78 Arabidopsis genes that were induced by aphid saliva infiltration, 52 had been identified previously as aphid-induced, but few are responsive to the well-known plant defense signaling molecules salicylic acid and jasmonate. Quantitative PCR analysis confirms expression of saliva-induced genes. In particular, expression of a set of O-methyltransferases, which may be involved in the synthesis of aphid-repellent glucosinolates, was significantly up-regulated by both M. persicae feeding and treatment with aphid saliva. However, this did not correlate with increased production of 4-methoxyindol-3-ylmethylglucosinolate, suggesting that aphid salivary components trigger an Arabidopsis defense response that is independent of this aphid-deterrent glucosinolate.
Myzus persicae (green peach aphid) salivary components induce defence responses in Arabidopsis thaliana.
Specimen part, Treatment
View SamplesA prominent enzyme in organellar RNA metabolism is the exoribonuclease polynucleotide phosphorylase (PNPase), whose reversible activity is governed by the nucleotides diphosphate-inorganic phosphate ratio. In Chlamydomonas reinhardtii, PNPase regulates chloroplast transcript accumulation in response to phosphorus (P) starvation, and PNPase expression is repressed by the response regulator PSR1 under these conditions. Here, we investigated the role of PNPase in the Arabidopsis (Arabidopsis thaliana) P deprivation response by comparing wild-type and pnp mutant plants with respect to their morphology, metabolite profiles, and transcriptomes. We found that P-deprived pnp mutants develop aborted clusters of lateral roots, which are characterized by decreased auxin responsiveness and cell division, and exhibit cell death at the root tips. Electron microscopy revealed that the collapse of root organelles is enhanced in the pnp mutant under P deprivation and occurred with low frequency under P-replete conditions. Global analyses of metabolites and transcripts were carried out to understand the molecular bases of these altered P deprivation responses. We found that the pnp mutant expresses some elements of the deprivation response even when grown on a full nutrient medium, including altered transcript accumulation, although its total and inorganic P contents are not reduced. The pnp mutation also confers P status-independent responses, including but not limited to stress responses. Taken together, our data support the hypothesis that the activity of the chloroplast PNPase is involved in plant acclimation to P availability and that it may help maintain an appropriate balance of P metabolites even under normal growth conditions.
Abnormal physiological and molecular mutant phenotypes link chloroplast polynucleotide phosphorylase to the phosphorus deprivation response in Arabidopsis.
Age, Specimen part, Treatment
View SamplesNo description.
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Specimen part, Treatment
View SamplesUnderstanding how the expression of transcription factor (TF) genes is modulated is essential for reconstructing gene regulatory networks. There is increasing evidence that sequences other than upstream noncoding can contribute to modulating gene expression, but how frequently they do so remains unclear. Here, we investigated the regulation of TFs expressed in a tissue-enriched manner in Arabidopsis roots. For 61 TFs, we created GFP reporter constructs driven by each TF's upstream noncoding sequence (including the 5'UTR) fused to the GFP reporter gene alone or together with the TF's coding sequence. We compared the visually detectable GFP patterns with endogenous mRNA expression patterns, as defined by a genome-wide microarray root expression map.
Transcriptional and posttranscriptional regulation of transcription factor expression in Arabidopsis roots.
Age, Specimen part
View SamplesA key question in developmental biology is how cells exchange positional information for proper patterning during organ development. In plant roots the radial tissue organization is highly conserved with a central vascular cylinder in which two water conducting cell types, protoxylem and metaxylem, are patterned centripetally. We show that this patterning occurs through crosstalk between the vascular cylinder and the surrounding endodermis mediated by cell-to-cell movement of a transcription factor in one direction and microRNAs in the other. SHORT ROOT, produced in the vascular cylinder, moves into the endodermis to activate SCARECROW. Together these transcription factors activate MIR165a and 166b. Endodermally produced miR165/6 then acts to degrade its target mRNAs encoding class III homeodomain-leucine zipper transcription factors in the endodermis and stele periphery. The resulting differential distribution of target mRNA in the vascular cylinder determines xylem cell types in a dosage dependent manner.
Cell signalling by microRNA165/6 directs gene dose-dependent root cell fate.
Age, Specimen part
View SamplesAlthough many regulatory components of light signaling have been functionally characterized, only a few of them have been reported to cross talk with other signaling cascades. In this study, we have analyzed the expression profiles of Arabidopsis genes in wild-type, atmyc2 mutant, cop1-6 mutant, and atmyc2 cop1-6 double mutant seedlings grown under constant dark, constant blue-light, and constant blue-light along with abscisic acid (ABA) to illustrate the interplay of negative regulators, AtMYC2 and COP1, in light and ABA signaling
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View SamplesArabidopsis thaliana seeds after imbibition were inoculated in ½ MS medium supplemented with 0.8% agar and 1% sucrose. Once the plant material was uniformly germinated, the experimental conditions were applied. 5d old light-grown uniformly germinated seedlings were washed seven times with sterile water with last wash given by ½ MS liquid medium without sucrose to remove residual exogenous sugar and the plant material was kept in ½ MS liquid without sucrose in the dark for all subsequent steps. Cultures were shaken at 140 rpm at 22oC for 24 h and then 3 h treatment was given with liquid ½ MS without glucose and liquid ½ MS supplemented with BR (0.1 ?M EBR), glucose (3%), glucose (3%) + BR (0.1 ?M EBR). Seedlings were harvested after 3h and preceded for RNA isolation and Microarray analysis.
Genome wide Analysis of Glucose and Brassinosteroid Signaling Interactions in Arabidopsis thaliana
Age, Time
View SamplesRecognition of microbial patterns and host derived damage signals by host pattern recognition receptors is a key step in immune activation in multicellular eukaryotes. Here we show how mutations in ethylene signaling and the coreceptor bak1 affect host immune responses triggered by elicitors.
Layered pattern receptor signaling via ethylene and endogenous elicitor peptides during Arabidopsis immunity to bacterial infection.
Treatment, Time
View SamplesInnate immune responses of plant cells confer the first line of defence against pathogens. Signals generated by activated receptors are integrated inside the cell and converge on transcriptional programmes in the nucleus. The Arabidopsis Toll-related intracellular receptor RPS4 operates inside nuclei to trigger resistance to Pseudomonas bacteria expressing AvrRps4 and defence gene reprogramming through the stress response regulator, EDS1.
Arabidopsis TNL-WRKY domain receptor RRS1 contributes to temperature-conditioned RPS4 auto-immunity.
Specimen part
View SamplesArabidopsis SnRK1 is structurally and functionally related to the yeast Snf1 and mammalian AMP-activated kinases, which are activated in response to carbon/glucose limitation and stress conditions causing an imbalance of energy homeostasis increasing the AMP/ATP ratio. Mutations of the SNF4 activating subunit of trimeric Arabidopsis SnRK1 complexes are not transmitted through the male meiosis. Silencing of SNF4 by a -estradiol-inducible artificial microRNA (amiR-SNF4) constructs was used to examine how inhibition of SnRK1 affects transcriptional regulation of different cellular pathways in dark and light grown seedlings. This study shows that amiR-SNF4 silencing of SnRK1 leads to coordinate transcriptional activation of salicylic acid and trehalose synthesis, oxidative/endoplasmic reticulum stress and pathogen defense responses by inducing simultaneous changes in numerous other essential hormonal and metabolic pathways in Arabidopsis.
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Age, Specimen part
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