Project description:Wounding is a trigger for both regeneration and defense in plants, but it is not clear if the two responses are linked by common activation or represent potential tradeoffs. While plant glutamate-like receptors (GLRs) are known to mediate defense responses, we implicate GLRs in regeneration through dynamic changes in chromatin and transcription in reprogramming cells near wound sites. Here, we show that genetic mutation and pharmacological inhibition of GLRs increases regeneration efficiency in multiple organ repair systems and plant species. Perturbation of GLR-mediated function, possibly by affecting Calcium fluxes, speeds cell division and re-specification of the stem cell niche while dampening a subset of defense responses. We show that the GLRs work through salicylic acid (SA) signaling in their effects on regeneration, with mutants in the SA receptor NPR1 partially resistant to GLR perturbation and hyper regenerative. These findings reveal a conserved mechanism that regulates a tradeoff between defense and regeneration and also offer new strategies to improve regeneration in agricultural and conservation.
Project description:Plant roots can regenerate after complete excision of their tip, including the stem cell niche, but it is not clear what developmental program mediates such repair. Here, we use a combination of lineage tracing, single-cell RNA-seq, and marker analysis to test different models of tissue reassembly. We show that rapid cell-identity transitions lead to the formation of a new stem cell niche from multiple remnant tissues. The transcriptome of regenerating cells prior to stem cell activation resembled that of the embryonic root progenitor, and regeneration defects were more severe in embryonic versus adult root mutants. Furthermore, the signaling domains of the hormones auxin and cytokinin mirrored their embryonic dynamics, and manipulation of both hormones altered the position of new tissues and stem cell niche markers. Our findings suggest that plant organ regeneration resembles the developmental stages of embryonic patterning and is guided by spatial information laid down by complementary hormone domains. 215 single cells isolated from marked stele tissue (either using WOL or AHP6 promoters), before, at 3h, 16h and 46h post root tip decapitation
Project description:A critical step in regeneration is recreating the cellular identities and patterns of lost organs long after embryogenesis is complete. In plants, perpetual (indeterminate) organ growth occurs in apical stem cell niches, which have been shown to re-establish quickly when damaged or removed (1,2). Here we ask whether the machinery of perpetual organ growth, stem cell activity, is needed for the phase of regeneration that leads to replenishing lost cell identities and patterning, or, whether organ re-establishment enlists a wider group of pluripotent cells. We adapt a root tip regeneration system to Arabidopsis that permits us to assess the molecular and functional recovery of specific cell fates during organ regeneration. These results suggest a rapid restoration of missing cell fate and function in advance of the recovery of stem cell activity. Surprisingly, plants with mutations that fail to maintain stem cell activity were able to re-pattern their distal tip and re-specify lost cell fates. Thus, although stem cell activity is required to resume indeterminate growth (3), our results show it is not necessary for cell re-specification and patterning steps. This implies a regeneration mechanism that coordinates patterning of the whole organ, as in embryogenesis, but is initiated from different starting morphologies. 1. Feldman, L. J. Denovo Origin of Quiescent Center Regenerating Root Apices of Zea-Mays. Planta 128, 207-212 (1976). 2. Xu, J. et al. A molecular framework for plant regeneration. Science 311, 385-8 (2006). 3. Gordon, S. P. et al. Pattern formation during de novo assembly of the Arabidopsis shoot meristem. Development 134, 3539-48 (2007). We adapted root tip excision techniques to Arabidopsis, enabling us to perform microarray profiling of regenerating root tissue. Excisions were performed at 4 days post-germination (dpg) at a distance of 130 um from the root tip, resulting in the complete excision of QC, all surrounding stem cells along with several tiers of daughter cells, and the root cap, including all of the columella and most of the lateral root cap. The tip section and then approximately 70 um of regenerating tissue was recut at different time points post cutting. We sampled regenerating stumps at 0hrs, 5 hrs, 13 hrs, 22 hrs, and 7 days after the excision for microarray analysis (Methods). We also sampled root sections immediately above the zone competent to regenerate at 270 um to approximately 340 um. Experiment Overall Design: 30 samples with 4 or 3 replicates for each condition representing a time course of regenerating root stumps and including controls for root tips (regeneration endpoint) at 4 dpg and 8 dpg and a wounded set of samples representing root tissue at 270-340 mm from the root tip for non-regeneration control
Project description:Plant roots can regenerate after complete excision of their tip, including the stem cell niche, but it is not clear what developmental program mediates such repair. Here, we use a combination of lineage tracing, single-cell RNA-seq, and marker analysis to test different models of tissue reassembly. We show that rapid cell-identity transitions lead to the formation of a new stem cell niche from multiple remnant tissues. The transcriptome of regenerating cells prior to stem cell activation resembled that of the embryonic root progenitor, and regeneration defects were more severe in embryonic versus adult root mutants. Furthermore, the signaling domains of the hormones auxin and cytokinin mirrored their embryonic dynamics, and manipulation of both hormones altered the position of new tissues and stem cell niche markers. Our findings suggest that plant organ regeneration resembles the developmental stages of embryonic patterning and is guided by spatial information laid down by complementary hormone domains.
Project description:Wounding is a trigger for both regeneration and defense in plants, but it is not clear if the two responses are linked by common activation or represent potential tradeoffs. While plant glutamate-like receptors (GLRs) are known to mediate defense responses, we implicate GLRs in regeneration through dynamic changes in chromatin and transcription in reprogramming cells near wound sites. Here, we show that genetic mutation and pharmacological inhibition of GLRs increases regeneration efficiency in multiple organ repair systems and plant species. Perturbation of GLR-mediated function, possibly by affecting Calcium fluxes, speeds cell division and re-specification of the stem cell niche while dampening a subset of defense responses. We show that the GLRs work through salicylic acid (SA) signaling in their effects on regeneration, with mutants in the SA receptor NPR1 partially resistant to GLR perturbation and hyper regenerative. These findings reveal a conserved mechanism that regulates a tradeoff between defense and regeneration and also offer new strategies to improve regeneration in agricultural and conservation.
Project description:A critical step in regeneration is recreating the cellular identities and patterns of lost organs long after embryogenesis is complete. In plants, perpetual (indeterminate) organ growth occurs in apical stem cell niches, which have been shown to re-establish quickly when damaged or removed (1,2). Here we ask whether the machinery of perpetual organ growth, stem cell activity, is needed for the phase of regeneration that leads to replenishing lost cell identities and patterning, or, whether organ re-establishment enlists a wider group of pluripotent cells. We adapt a root tip regeneration system to Arabidopsis that permits us to assess the molecular and functional recovery of specific cell fates during organ regeneration. These results suggest a rapid restoration of missing cell fate and function in advance of the recovery of stem cell activity. Surprisingly, plants with mutations that fail to maintain stem cell activity were able to re-pattern their distal tip and re-specify lost cell fates. Thus, although stem cell activity is required to resume indeterminate growth (3), our results show it is not necessary for cell re-specification and patterning steps. This implies a regeneration mechanism that coordinates patterning of the whole organ, as in embryogenesis, but is initiated from different starting morphologies. 1. Feldman, L. J. Denovo Origin of Quiescent Center Regenerating Root Apices of Zea-Mays. Planta 128, 207-212 (1976). 2. Xu, J. et al. A molecular framework for plant regeneration. Science 311, 385-8 (2006). 3. Gordon, S. P. et al. Pattern formation during de novo assembly of the Arabidopsis shoot meristem. Development 134, 3539-48 (2007). We adapted root tip excision techniques to Arabidopsis, enabling us to perform microarray profiling of regenerating root tissue. Excisions were performed at 4 days post-germination (dpg) at a distance of 130 um from the root tip, resulting in the complete excision of QC, all surrounding stem cells along with several tiers of daughter cells, and the root cap, including all of the columella and most of the lateral root cap. The tip section and then approximately 70 um of regenerating tissue was recut at different time points post cutting. We sampled regenerating stumps at 0hrs, 5 hrs, 13 hrs, 22 hrs, and 7 days after the excision for microarray analysis (Methods). We also sampled root sections immediately above the zone competent to regenerate at 270 um to approximately 340 um. Keywords: time course, development, root regeneration
Project description:As the only known mammalian organ that can fully and annually regenerate, deer antler has significant advantages over lower-order animal models when investigating the control of stem cell-based organ regeneration. Antler regeneration is known to be initiated and maintained by neural crest-derived stem cells in different states of activation. Antler stem cells can therefore be used as a model system to study the proteins and pathways involved in the maintenance of a stem cell niche and their activation and differentiation during organ formation. In the current study, the MSC markers CD73, CD90 and CD105 were examined within the antler tip. Label-free quantification was performed to investigate the protein profiles of antler stem cells under different stages of activation and included: dormant pedicle periosteum (DPP), antler growth center (GC), post-active stem cells from mid-beam antler periosteum (MAP), and deer facial periosteum (FP) as a control (n = 3 per group). PEAKS and IPA software were used to analyze the proteomic data. Our research confirmed the central role of stem cell activation in the development of this mammalian organ by localizing the MSC markers within the antler growth center. Label-free quantification revealed that the greatest number of unique proteins (eighty-seven) was found in the growth center tissue. There were only 12 proteins found with expression levels that significantly differed between DPP and FP. Protein profiles of these two groups indicated that antler stem cells may use similar mechanisms to maintain dormancy within a stem cell niche. The number of significantly regulated proteins between DPP, MAP and GC was 153. Among them, the majority were upregulated in the growth center. Activation of antler stem cells was associated with a number of biological processes and signaling pathways such as Hippo and canonical Wnt signaling. This work identifies the key canonical pathways, molecular/cellular functions and upstream regulators involved in mammal organ regeneration.
Project description:Shoot apical meristem (SAM) of higher plant composed of a few distinct cell types. All the cells in a mature plant’s SAM derived from 30~35 stem cells reservoir which are located at the tip of the apex. Plants ability to give rise diverse cell types from a pool of pluripotent stem cells requires orchestrated gene network that controls the cell fate commitment during the meristem development. To understand, how gene regulatory networks control cell identities switches during cell differentiation requires resolution in recording their gene expression pattern at single cell resolution. An earlier expression map involving three-cell population of stem cell niche revealed complex expression pattern among the cell types1. We developed this approach further and report here a gene expression map using cell-sorting methods for fluorescent protein marked cells in Arabidopsis shoot. The map covered 10 cell populations. This gene expression map represents data from 10 different cell types from Arabidopsis SAM. It will be first step in defining the function of many unknown genes in model plant Arabidopsis.