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Organ regeneration in plants is independent of stem cell niche activity

ABSTRACT: 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

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE9996 | GEO | 2008/10/30

SECONDARY ACCESSION(S): PRJNA104017

REPOSITORIES: GEO

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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:Protemics of anolis carolinensis tails undergoing regeneration. As amniote vertebrates, lizards are the most closely related organisms to humans capable of appendage regeneration. Lizards can autotomize, or release their tails as a means of predator evasion, and subsequently regenerate a functional replacement. Green anoles (Anolis carolinensis) can regenerate their tails through a process that involves differential expression of hundreds of genes, which has previously been analyzed by transcriptomic and microRNA analysis. To investigate protein expression in regenerating tissue, we performed whole proteomic analysis of regenerating tail tip and base. This is the first proteomic data set available for the green anole lizard. We identified 976 proteins only in the regenerating tail base, 796 only in the tail tip, and 874 in both tip and base. For 90% of these proteins in these tissues, we were able to assign a clear orthology to gene models in either the Ensembl or NCBI databases. For 20 proteins in the tail base (2.5%), 7 proteins in the tail tip (0.9%), and 7 proteins in both regions (0.8%), the gene model in Ensembl and NCBI matched an uncharacterized protein, confirming that these predictions are present in the proteome. Ontology and pathways analysis of proteins expressed in the regenerating tail base identified categories including actin filament-based process, ncRNA metabolism, regulation of phosphatase activity, small GTPase mediated signal transduction, and cellular component organization or biogenesis. Analysis of proteins expressed in the tail tip identified categories including regulation of organelle organization, regulation of protein localization, ubiquitin-dependent protein catabolism, small GTPase mediated signal transduction, morphogenesis of epithelium, and regulation of biological quality. These proteomic findings confirm pathways and gene families activated in tail regeneration in the green anole as well as identify uncharacterized proteins whose role in regrowth remains to be revealed.

Project description:Variability of regenerative potential among animals has long perplexed biologists. Based on their amazing regenerative abilities, planarians have become important models for understanding the molecular basis of regeneration; however, planarian species with limited regenerative abilities are also found. Despite the importance of understanding the differences between closely related, regenerating and non-regenerating organisms, few studies have focused on the evolutionary loss of regeneration, and the molecular mechanisms leading to such regenerative loss remain obscure. Here we examine Procotyla fluviatilis, a planarian with restricted ability to replace missing tissues, utilizing next-generation sequencing to define the gene expression programs active in regeneration-permissive and regeneration-deficient tissues. We found that Wnt signaling is aberrantly activated in regeneration-deficient tissues. Remarkably, down-regulation of canonical Wnt signaling in regeneration-deficient regions restores regenerative abilities: blastemas form and new heads regenerate in tissues that normally never regenerate. This work reveals that manipulating a single signaling pathway can reverse the evolutionary loss of regenerative potential. RNA-seq experiments to identify gene expression changes following amputation in body regions with variable regenerative potential. Adult Procotyla fluviatilis were amputated at sites either anterior or posterior to the pharynx. After 24 hours post-amputation, tissues near the amputation site were excised and RNA was extracted. Similar tissues were excised from uncut control animals. Samples were processed for RNA-seq using Illumina procedures. We generated a de novo P. fluviatilis transcriptome and used RNA sequencing (RNA-seq) to characterize transcripts from excised tissue fragments in Reg+ and Reg- body regions 24 hours post-amputation. We performed parallel analyses on tissues excised from intact animals at identical body regions to account for regional differences in transcripts, thereby identifying changes resulting from amputation. Samples A1-A3 = Regeneration-proficient (Reg+) tissue excision 24 hours after amputation. Samples B1-B3 = Tissue excision from regeneration-proficient (Reg+) region but not amputated. Samples C1-C3 = Tissue excision from regeneration-deficient (Reg-) tissues 24 hours after amputation. Samples D1, D3-D4 = Tissue excision from regeneration-deficient (Reg-) region that was not amputated.

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Organ regeneration in plants is independent of stem cell niche activity

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