Project description:The root epidermis of Arabidopsis provides a simple and experimentally useful model for studying the molecular basis of cell fate and differentiation. The goal of this study was to define the transcript changes in the root epidermis of mutants associated with root epidermis cell specification, including mutants that lack a visible phenotypic alteration (try, egl3, myb23, and ttg2). Transcript levels were assessed by purifying populations of root epidermal cells using fluorescence-based cell-sorting with the WER::GFP transgene. These microarray results were used to compare the effects of single and double mutants on the gene regulatory network that controls root epidermal cell fate and differentiation in Arabidopsis. The cells of the developing root epidermis were obtained by growing plant seedlings expressing the WER::GFP transgene under sterile conditions on MS media, cutting off root tips (including all developmental stages), protoplasting the roots, and purifying cells containing GFP using FACS. The WER::GFP transgene is expressed throughout the developing cells of the root epidermis and the lateral root cap. Three biological replicates were analyzed for each of the plant lines examined in this study.
Project description:The plant hormone auxin represents an important regulator of growth and development. Significant insight into the mechanisms of auxin action have been obtained from studies of auxin resistant mutants such as aux1 and axr3. The Arabidopsis axr4 mutant was identified in a screen for auxin resistant root growth. In addition to the root growth of axr4 being resistant to exogenous auxin, there is also a 50% reduction in the number of lateral roots that form. The double axr4/aux1 mutant shows an additive effect in reducing lateral root numbers to 10% of wild-type. Gaining further information about the potential interaction between AUX1 and AXR4 may provide important insight into auxin regulated plant growth. Mapping experiments have placed the AXR4 gene on the lower arm of chromosome 1 between the ch1 and le markers (Hobbie and Estelle 1995). However, the AXR4 gene remains to be cloned. Identifying the AXR4 gene will help in elucidating the function of the protein. A transcript analysis of axr4 mutant seedlings will be used in 2 ways. Firstly, the transcription level of genes in the locality of the axr4 map position will be examined to identify those which are absent or significantly reduced in axr4 compared to the Col0 control. If the lesion causing the axr4 mutation results in a highly unstable mRNA or abolishes transcription then the signal will be dramatically reduced. Potential candidate genes identified in this way will be further analysed using a combination of RT-PCR and sequencing to identify the AXR4 gene. Secondly, the transcriptomics data obtained from axr4 and Col0 will be compared to identify genes which show significant transcript level differences and therefore represent targets for either direct or indirect regulation by AXR4. Hobbie, L. and Estelle, M. (1995) The axr4 auxin-resistant mutants of Arabidopsis thaliana define a gene important for root gravitropism and lateral root initiation. Plant J. 7 211-220
Project description:Plant roots located in the upper soil layers are prone to experience high temperatures. To gain insight into the effect of high temperature on root development and functioning, we exposed five-day-old Arabidopsis thaliana seedlings grown on agar plates to 30 °C for 48 hours, and compared the gene expression profile in the root tip with that from seedlings that remained at 22 °C.
Project description:Phosphate (Pi) deficiency alters root hair length and frequency as a means of increasing the absorptive surface area of roots. Three partly redundant single R3 MYB proteins, CAPRICE (CPC), ENHANCER OF TRY AND CPC1 (ETC1) and TRIPTYCHON (TRY), positively regulate the root hair cell fate by participating in a lateral inhibition mechanism. To identify putative targets and processes that are controlled by these three transcription factors (TFs), we conducted transcriptional profiling of roots from Arabidopsis thaliana wild-type plants, and cpc, etc1 and try mutants grown under Pi-replete and Pi-deficient conditions using RNA-seq.
Project description:Lateral roots are essential components of the plant edaphic interface; contributing to water and nutrient uptake, biotic and abiotic interactions, stress survival, and plant anchorage. We have identified the TETRATRICOPEPTIDE-REPEAT THIOREDOXIN-LIKE 3 (TTL3) gene as being related to lateral root emergence and later development. Loss of function of TTL3 leads to a reduced number of emerged lateral roots due to delayed development of lateral root primordia. This trait is further enhanced in the triple mutant ttl1ttl3ttl4. TTL3 interacts with microtubules and endomembranes and is known to participate in the brassinosteroid signaling pathway. Both ttl3 and ttl1ttl3ttl4 mutants are less sensitive to brassinosteroid treatment in terms of lateral root formation and primary root growth. The ability of TTL3 to modulate biophysical properties of the cell wall was established under restrictive conditions of hyperosmotic stress and loss of root growth recovery, which was enhanced in ttl1ttl3ttl4. Timing and spatial distribution of TTL3 expression is consistent with its role in development of lateral root primordia before their emergence and subsequent growth of lateral roots. TTL3 emerged as a novel component of the root system morphogenesis regulatory network.
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:Control of the dimensions of organ primordia is crucial for proper organogenesis in the development of multicellular organisms. Lateral root formation is a major type of plant organogenesis important for postembryonic development of the root system. Lateral root formation begins with a few rounds of asymmetric, anticlinal cell division (formative cell division) in the pericycle, which determines the basal dimensions of root primordia. Here we show, based on molecular genetic analysis of temperature-dependent fasciation (TDF) mutants of Arabidopsis thaliana, that mitochondria play an unexpected role in the restriction of formative cell division and thus in the control of the basal dimensions of lateral root primordia. Three TDF mutants, root redifferentiation defective 1 (rrd1), rrd2, and root initiation defective 4 (rid4), exhibit lateral root fasciation from excess formative cell division under high-temperature conditions. We identify RRD1 as encoding a poly(A)-specific ribonuclease (PARN)-like protein and RRD2 and RID4 as encoding pentatricopeptide repeat (PPR) proteins. Subcellular localization and predicted functions of these proteins implicate them in poly(A)-dependent RNA degradation in mitochondria. This characterization is supported by the finding that mitochondrial RNAs with poly(A) tails, most of which are mRNAs of respiratory chain components, accumulate at an unusually high level in these TDF mutants.