Project description:bHLH122 could be induced by salt, osmotic and drought stress except ABA, the transgentic Arabidopsis were more tolerant to abiotic stresses, such as drought and salt. What's more, in the overexpression plants, the endogenesis ABA contents were higher than WT. We found there existed an interaction between bHLH122 and CYP707A3 by virtue of EMSA and ChIP assays. We wanted to learn more about the molecular mechanism of bHLH122 and to explore what had changed in the over-expression plant through Genechips. Two independent overexpression bHLH122 lines and WT Arabidopsis were chosen to RNA extraction and hybridization on Affymetrix microarrays. The plants were sowed on MS medium after 96 h stratification,then transferred into soil after one weeks. After 2 weeks, collected the shoot above the soil and extracted RNA, digested by DNaseM-bM-^EM- and hybrid on Affymetrix microarrays.
Project description:We characterized the global response of plants carrying a mitochondrial dysfunction induced by the expression of the unedited form of the ATP synthase 9 subunit. The u-ATP9 transgene driven by A9 and Apetala3 promoters induce mitochondrial dysfunction revealed by a decrease in both oxygen uptake and ATP levels, with an increase in ROS and a concomitant oxidative stress response. The transcriptome analysis of young Arabidopsis flowers, validated by RT-PCR and enzymatic or functional tests, show dramatic changes in u-ATP9 plants. Both lines present a modification in the expression of several genes involved in carbon, lipid and cell wall metabolism, suggesting that an important metabolic readjustment occurs in plants with a mitochondrial dysfunction. Interestingly, transcript levels involved in mitochondrial biogenesis, protein synthesis, and degradation are affected. Moreover, several mRNA levels for transcription factors and DNA binding proteins were also changed. Some of them are involved in stress and hormone response, suggesting that several signaling pathways overlap. Indeed, the transcriptome data reveal that the mitochondrial dysfunction dramatically alters genes involved in signaling pathways, including those involved in ethylene, absicic acid and auxin signal transduction. Our data suggest that the mitochondrial dysfunction model used in this rapport may be useful to uncover the retrograde signaling mechanism between the nucleus and mitochondria in plant cells. Arabidopsis oligonucleotide microarrays fabricated by the University of Arizona contain 26,000 oligonucleotides (http://www.ag.arizona.edu/microarray/). RNA was isolated from 6-week-old flowers from u-ATP9 and wt plants. The experimental (mutant) and reference (wild type) RNA samples were reverse-transcribed and directly labeled with either Cy5-dUTP or Cy3-dUTP fluorescent dye (GE Healthcare), using random hexamer primers (Invitrogen). Excess nucleotides and primers were removed using QIAquick PCR Purification Kit (Qiagen). Labeled samples were mixed and then hybridized to microarray for 15 h at 60°C. The slides were washed at room temperature in three wash steps: 2 x SSC, 0.5% SDS; 0.5 x SSC; and 0.05 x SSC for 5 min each with gentle shaking. The slides were scanned with a GenePix 4000B Scanner (Axon Instruments Inc., Union City, CA). Normalization between the Cy3 and Cy5 fluorescent dye emission channels was achieved by adjusting the levels of both image intensities. The experiments were repeated four times with samples from different experiments, as biological replicates. In dye swapping experiments, the RNA samples from different experiments were reciprocally labeled, both as a biological and technical repetition for comparing the reproducibility of the experiments. Hybridization intensities for each microarray element were measured using ScanAlyze 4.24 (available at http://genome-www4.stanford.edu/MicroArray/SMD/restech.html). The two channels were normalized in log space using the z-score normalization on a 95% trimmed data set. We removed unreliable spots according to the following criteria: spots flagged as having false intensity caused by dust or background on the array were removed; and spots for which intensity was less than three fold above background were also eliminated. Data from multiple experiments were normalized (Bolstad, 2003) and signals from spots from different experiments were statistically analyzed using Significance Analysis of Microarrays using the one class response (SAM, http://www-stat.stanford.edu/~tibs/SAM/), cut at a false discovery rate < 10% (Tusher, 2001).
Project description:In plants, transposons and non-protein-coding repeats are epigenetically silenced by CG and non-CG methylation. This pattern of methylation is mediated in part by small RNAs and two specialized RNA polymerases, Pol IV and Pol V, in a process called RNA-directed DNA methylation. By contrast, many protein-coding genes transcribed by Pol II contain in their gene bodies exclusively CG methylation that is independent of small RNAs and Pol IV/Pol V activities. It is unclear how the different methylation machineries distinguish between transposons and genes. Here we report on a group of atypical genes that display in their coding region a transposon-like methylation pattern, which is associated with gene silencing in sporophytic tissues. We performed a methylation-sensitive amplification polymorphism analysis to search for targets of RNA-directed DNA methylation in Arabidopsis thaliana and identified several members of a gene family encoding cysteine-rich peptides (CRPs). We also examined small RNA abundance at individual CRP genes in the wild type plant, nrpd1, and rdr2 mutant plants.
Project description:RNA-directed DNA methylation (RdDM) is a small interfering RNA (siRNA)-mediated epigenetic modification that contributes to transposon silencing in plants. RdDM requires a complex transcriptional machinery that includes specialized RNA polymerases, named Pol IV and Pol V, as well as chromatin remodelling proteins, transcription factors, RNA binding proteins, and other plant-specific proteins whose functions are not yet clarified. In Arabidopsis thaliana, DICER-LIKE3 and members of the ARGONAUTE4 group of AROGONAUTE (AGO) proteins are involved, respectively, in generating and using 24-nt siRNAs that trigger methylation and transcriptional gene silencing (TGS) of homologous promoter sequences. AGO proteins act in silencing effector complexes by anchoring the 3â and 5â ends of the guide siRNAs at their N-terminal PAZ domain and MID domain, respectively. In addition, many AGO proteins cleave complementary target RNAs through an endonuclease (âslicerâ) activity in their C-terminal PIWI domain. AGO4 is the main AGO protein implicated in the RdDM pathway. Here we report the identification of the related AGO6 in a forward genetic screen for mutants defective in RdDM and TGS in shoot and root apical meristems in Arabidopsis thaliana. The identification of AGO6, and not AGO4, in our screen is consistent with the primary expression of AGO6 in shoot and root growing points and the preferential association of Pol V with AGO6. Examination of siRNA abundance in the trasngenic wild type plant (contains trigger and silencer transgenes) and the ago6-4 mutant.
Project description:Agilent 4x44k tobacco micro array of wild type tobacco (WT) and whole tobacco mosaic virus (TMV) containing transgenic tobacco plants. The transgenic plants before resistance break (BRB-6 weeks), after resistance break (ARB-8 weeks) and wild type tobacco plants infected with TMV (TMVi-9weeks) leaves were analyzed. Three biological replicates were performed for each sample.
Project description:Agilent 4x44k tobacco micro array of wild type tobacco, empty vector control, and HC-Pro transgenic tobacco plants. Both 1-month old leaves and flowers were analyzed. Three biological replicates were performed of each sample.
Project description:We have used a microarray approach to study the effects of the Potato Virus X Potexvirus (PVX)-specific P25 VRS protein on the transcript profile of tobacco plants, when expressed as a transgene in these plants.
Project description:Full title: Deep sequencing of small RNAs in the trasngenic wild type plant (contains trigger and silencer transgenes) and the IWR1-type transcription factor mutant, dms4 RNA-directed DNA methylation (RdDM) in plants requires two RNA polymerase II (PolII)-related RNA polymerases named PolIV and PolV. A genetic screen designed to reveal factors important for RdDM in a developmental context in Arabidopsis identified DEFECTIVE IN MERISTEM SILENCING 4 (DMS4). Unlike other mutants defective in RdDM, dms4 mutants have a pleiotropic developmental phenotype.DMS4 is similar to yeast IWR1, a conserved putative transcription factor that interacts with PolII subunits. In the transgenic system studied, mutations in DMS4 directly or indirectly affect PolIV-dependent secondary siRNAs, PolV-mediated RdDM, PolV-dependent synthesis of intergenic noncoding RNA, and expression of many PolII-driven genes. These data suggest that DMS4 may be a regulatory factor for multiple RNA polymerases, thus explaining its diverse roles in the plant. Examination of siRNA abundance in the trasngenic wild type plant (contains trigger and silencer transgenes) and the dms4 mutant.
Project description:Wood-degrading brown rot fungi are essential recyclers of plant biomass in forest ecosystems. Their efficient cellulolytic systems, which have potential biotechnological applications, apparently depend on a combination of two mechanisms: lignocellulose oxidation by reactive oxygen species (ROS) and polysaccharide hydrolysis by a limited set of glycoside hydrolases (GHs). Given that ROS are strongly oxidizing and non-selective, these two steps are likely segregated. A common hypothesis has been that brown rot fungi use a concentration gradient of chelated metal ions to confine ROS generation inside wood cell walls before enzymes can infiltrate. We examined an alternative: that lignocellulose-oxidation (LOX) components involved in ROS production are differentially expressed by brown rot fungi ahead of GH components. We used spatial mapping to resolve a temporal sequence in Postia placenta, sectioning thin wood wafers colonized directionally. Among sections, we measured gene expression by whole transcriptome sequencing (RNAseq) and assayed relevant enzyme activities. We found a marked pattern of LOX upregulation in a narrow (5-mm; 48-hr) zone at the hyphal front, which included many genes likely involved in ROS generation. Upregulation of GH5 endoglucanases and many other GHs clearly occurred later, behind the hyphal front, with notable exceptions of two likely expansins and a GH28 pectinase. Our results support a staggered mechanism for brown rot that is controlled by differential expression rather than microenvironmental gradients. This mechanism likely results in an oxidative pretreatment of lignocellulose, possibly facilitated by expansin- and pectinase-assisted cell wall swelling, before cellulases and hemicellulases are deployed for polysaccharide depolymerization. We sequenced mRNA from 9 Postia placenta samples taken from 3 wood sections of wafer design, with 3 bioreplicates for each wood section, to compare the gene expression during brown rot processes. Three wood sections of the wafer are representing early to late decay stages.