Project description:We characterised mutants in the GRAS family transcription factor AtSCL26 in Arabidopsis thaliana using a combination of gene functional analysis, hormone treatments and expression profiling at the cell type level. This has enabled us to implicate AtSCL26 in the cell-specific control of nitrogen-giberellic acid response cross-talk to control root architecture.
Project description:To optimize access to nitrogen under limiting conditions, root systems must continuously sense and respond to local or temporal fluctuations in nitrogen availability. In Arabidopsis thaliana and several other species, external N levels that induce only mild deficiency stimulate the emergence of lateral roots and especially the elongation of primary and lateral roots. However, the identity of the genes involved in this coordination remains still largely elusive. In order to identify novel genes and mechanisms underlying nitrogen-dependent root morphological changes, we investigated time-dependent changes in the root transcriptome of Arabidopsis thaliana plants grown under sufficient nitrogen or under conditions that induced mild nitrogen deficiency.
Project description:Root branching in response to changes in nitrogen status in the soil, is a dramatic example of the plant’s remarkable developmental plasticity. In recent work we investigated the genetic architecture of developmental plasticity, combining phenoclustering and genome-wide association studies in 96 Arabidopsis thaliana ecotypes with expression profiling in 7 ecotypes, to characterise natural variation in root architectural plasticity at the phenotypic, genetic, and transcriptional levels. This series contains the microarray expression data for 7 ecotypes that represent a range of root branching strategies. We used microarrays to detail the global programme of gene expression involved in the plants response to nitrogen in the root and identified distinct classes of up- and down-regulated genes in the seven different Arabidopsis ecotypes during this process. The whole experiment was carried out in triplicate with 42 chips in total (14 experiments). The nitrogen response in seven Arabidopsis thaliana ecotype (Col0, Kas2, NFA8, SQ8, TAMM27, Ts5, Var2-1) whole roots was assayed using Affymetrix microarrays. Seedlings were grown hydroponically in low nitrogen for 12 days, then 5mM KNO3 was used as a nitrogen treatment for 2 hours with 5mM KCl used as a control treatment for the same length of time. At the end of the treatment time roots were harvested and flash-frozen in liquid nitrogen for subsequent RNA extraction. For *Probe_Elements_Removed* file descriptions, please see the Sample records' "Data processing" annotations.
Project description:Nitrogen (N), the primary limiting factor for plant growth and yield in agriculture, has a patchy distribution in soils due to fertilizer application or decomposing organic matter. Studies in solution culture over-simplify the complex soil environment where microbial competition and spatial and temporal heterogeneity challenge roots’ ability to acquire adequate amounts of nutrients required for plant growth. In this study, various ammonium treatments (as 15N) were applied to a discrete volume of soil containing tomato (Solanum lycopersicum) roots to simulate encounters with a localized enriched patch of soil. Transcriptome analysis was used to identify genes differentially expressed in roots 53 hrs after treatment. Results: The ammonium treatments resulted in significantly higher concentrations of both ammonium and nitrate in the patch soil. The plant roots and shoots exhibited increased levels of 15N over time, indicating a sustained response to the enriched environment. Root transcriptome analysis identified 585 genes differentially regulated 53 hrs after the treatments. Nitrogen metabolism and cell growth genes were induced by the high ammonium (65 ug NH4+-N g-1 soil), while stress response genes were repressed. The complex regulation of specific transporters following the ammonium pulse reflects a simultaneous and synergistic response to rapidly changing concentrations of both forms of inorganic N in the soil patch. Transcriptional analysis of the phosphate transporters demonstrates cross-talk between N and phosphate uptake pathways and suggests that roots increase phosphate uptake via the arbuscular mycorrhizal symbiosis in response to N. Conclusion: This work enhances our understanding of root function by providing a snapshot of the response of the tomato root transcriptome to a pulse of ammonium in a complex soil environment. This response includes an important role for the mycorrhizal symbiosis in the utilization of an N patch.
Project description:The acquisition of water and nutrients by plant roots is a fundamental aspect of agriculture and strongly depends on root architecture. Root branching and expansion of the root system is achieved through the development of lateral roots and is to a large extent controlled by the plant hormone auxin. However, the pleiotropic effects of auxin or auxin-like molecules on root systems complicate the study of lateral root development. Here we describe a small-molecule screen in Arabidopsis thaliana that identified naxillin as what is to our knowledge the first non-auxin-like molecule that promotes root branching. By using naxillin as a chemical tool, we identified a new function for root cap-specific conversion of the auxin precursor indole-3-butyric acid into the active auxin indole-3-acetic acid and uncovered the involvement of the root cap in root branching. Delivery of an auxin precursor in peripheral tissues such as the root cap might represent an important mechanism shaping root architecture. To further explore the specificity of naxillin for lateral root development, we compared the early effects of naxillin at the transcriptome level with NAA (1-Naphthaleneacetic acid) in roots of 3-day-old seedlings after 2-h and 6-h treatment. Arabidopsis thaliana (L). Heynh., Col-0 seeds were germinated vertically on solid medium derived from standard MS medium supplemented with 10 μM NPA (1-N-Naphthylphthalamic acid). Three days after germination, plants were transferred to 10 μM NAA (1-Naphthaleneacetic acid) or 50 μM naxillin for 2 and 6 hours. Plants were sampled before (Roots at T0, NPA) or after treatment (Roots at T1 and T2). RNA isolation was performed on 500 root sections (only root without meristems) for each sample. All sampling points were performed in three independent experiments.
Project description:The aim of the experiment was to identify early gibberellin (GA) responsive genes in the roots of an Arabidopsis GA deficient mutant.The GA deficient mutant used in this study is a transgenic line overexpressing the PcGA2ox1 gene. This mutant has an identical phenotype to ga1-3, but it does not require exogenous GA treatment for germination.Seeds were germinated on 1xMS + 1% (w/v) sucrose plates containing 0.7% gelrite, and grown under continous light. The plates were orientated vertically.After six days growth the plates were treated with or without 5uM GA4 for 0, 30, 60 and 180 minutes.Approximately 400 hypocotyls were harvested per timepoint using a razorblade and after excision the hypocotyls were frozen in liquid nitrogen giving a total of 7 experimental samples (1: untreated, 2: 30 mins GA4, 3: 30 mins untreated, 4: 60 mins GA4, 5: 60 mins untreated, 6: 180 mins GA4, 7: 180 mins untreated. Three biological replicates were performed giving a total of 21 root samples. Total RNA was isolated from the roots using the QIAGEN RNeasy method. Keywords: Expression profiling by array
Project description:The acquisition of water and nutrients by plant roots is a fundamental aspect of agriculture and strongly depends on root architecture. Root branching and expansion of the root system is achieved through the development of lateral roots and is to a large extent controlled by the plant hormone auxin. However, the pleiotropic effects of auxin or auxin-like molecules on root systems complicate the study of lateral root development. Here we describe a small-molecule screen in Arabidopsis thaliana that identified naxillin as what is to our knowledge the first non-auxin-like molecule that promotes root branching. By using naxillin as a chemical tool, we identified a new function for root cap-specific conversion of the auxin precursor indole-3-butyric acid into the active auxin indole-3-acetic acid and uncovered the involvement of the root cap in root branching. Delivery of an auxin precursor in peripheral tissues such as the root cap might represent an important mechanism shaping root architecture. To further explore the specificity of naxillin for lateral root development, we compared the early effects of naxillin at the transcriptome level with NAA (1-Naphthaleneacetic acid) in roots of 3-day-old seedlings after 2-h and 6-h treatment.
Project description:We study the effect of nitrogen limitation on the growth and development of poplar roots. We used microarrays to detail the global program of gene expression underlying morphological and developmental changes driven by low nitrogen in the growth media. We report the effect of nitrogen limitation on the growth and development of poplar roots. Low nitrogen concentration led to increased root elongation followed by lateral root proliferation and finally increased root biomass. These morphological responses correlated with high and specific activation of genes encoding regulators of cell cycle and enzymes involved in cell wall biogenesis, growth and remodeling. Comparative analysis of poplar and Arabidopsis root transcriptomes under nitrogen deficiency indicated many similarities and diversification in the response in the two species. A reconstruction of genetic regulatory network (GRN) analysis revealed a sub-network centered on a PtaNAC1-like transcription factor. Consistent with the GRN predictions, root-specific upregulation of PtaNAC1 in transgenic poplar plants increased root biomass and led to significant changes in the expression of the connected genes specifically under low nitrogen. PtaNAC1 and its regulatory miR164 showed inverse expression profiles during response to LN, suggesting of a micro RNA mediated attenuation of PtaNAC1 transcript abundance in response to nitrogen deprivation.
Project description:12plex_medicago_2012-03 - mtefd1 and wt roots and nodules - Identification of genes affected by a KO mutation in a transcription factor involved in root and nodule development, MtEFD1. - Comparison of wild type and efd-1 transcriptomes in non inoculated nitrogen-starved control roots and nodules at 4 dpi, 6 and 11 dpi. Comparison of wild type nodule (11 dpi) and root transcriptomes, using mixed random primed and polydT primed probes.
Project description:The plant hormone gibberellin (GA) represents an important regulator of growth and development. Early transcriptional events controlled by GA are not well characterised. Previous microarray studies have identified genes responsive to GA treatment in the whole seedling. The whole seedling represents many tissues where subtle effects of GA treatment in specific tissues may be masked. When treated with GA, an effect on the growth rate of roots was observed. More specifically, the shorter root of a GA-deficient plant can be rescued to wild-type length by the application of GA. This experiment was designed to identify GA-regulated genes in the root tips of Arabidopsis. The use of a GA-deficient mutant provides a greater potential to identify genes responding to GA treatment. Root tips are ideally suited for the quick uptake of the hormone treatment. There will be two biological replicates which will each consist of a control treatment at 0 minutes and 2 hours, as well as the experimental GA-treated 2 hour time point. This system provides an opportunity to compare gene expression between treated and non-treated root tips and allow the identification of early GA-responsive genes.